Stanford SSI Wiki - User contributions [en]

HABSIM

2020-07-28T15:00:39Z

Bjing:

'''High Altitude Balloon Simulator''' (HABSIM) is a web server ([http://habsim.org/ link]) developed by the SSI [[Balloons]] Team for customizable, ensemble-based, long range trajectory predictions. The aims of the prediction server, in comparison to existing ones, are as follows:

*Offer probabilistic predictions based on the Monte-Carlo GEFS run set.
*Offer predictions out to the maximum time window permitted by GEFS (+378 hrs).
*Offer finer and broader control over simulation parameters, including ascent rate, duration, simulation step, and drift coefficient.
*Export an intuitive prediction API which can be used to simulate arbitrary flight profiles.
*Offer a web-based UI which captures the functionality and flexibility of the API.

Primary clients of HABSIM include [[Cycloon]] and [[Spaceshot]]. The project source code may be viewed on [https://github.com/SSI-MC/habsim GitHub]. To get involved, please contact {{slack-user|bjing}} and {{slack-user|Adi}} and join {{slack-channel|balloons-habsim}}!

'''PyHABSIM''' is a Python package which exploits the HABSIM API to offer an intuitive, object-oriented, highly customizable prediction interface, wind and elevation data accession utilities, and trajectory analysis and optimization methods in Python. The package home pages may be found at [https://pypi.org/project/habsim/ PyPI] or [https://github.com/stanford-ssi/habsim_client GitHub]. Please contact {{slack-user|bjing}} to get involved!

SSI-97

2019-12-08T00:36:46Z

Bjing:

{{balloon-launch
| header = SSI-97
| img link =
| designations = '''CY-8'''
| launch date = November 17, 2019
| launch site = Pigeon Point Light Station, Pescadero, CA
| launch coordinates = 37.1827, -122.3923
| flight duration =
| flight length =
| flight profile = Ground tests
| landing time =
| landing site=
| landing coordinates =
| last = 93
| next =
}}

'''SSI-97''' (project designation '''CY-8''') was the seventh launch of [[Cycloon|Project Cycloon]] on November 17, 2019. Not a true launch, it was instead a series of ground tests of various properties of polyethylene tubing envelopes and the newly designed Cycloon vent mechanism. It was also the first return of Cycloon to Pigeon Point since the first launch, [[SSI-83]].

==Project context==

The original launch schedule for the quarter had called for a second altitude controlled flight in mid-November after a first test in October, [[SSI-93]]. When that first test became a ballast-only flight, the November flight would have been the first altitude-controlled flight. However, the outcome of SSI-93 demonstrated that Cycloon needed a better understanding of zero pressure balloons, a more rigorous pre-launch procedure, checklists, and better balloon envelope quality control. Thus, it was decided to conduct a series of ground tests for that purpose. Additionally, as the first version of a Cycloon vent mechanism was approaching completion, it was decided to test this mechanism on a ZPB envelope. Initially scheduled for '''November 16''', the tests were pushed back one day to accommodate schedules.

The simple avionics for these tests were constructed on November 8, followed by the balloons on November 14. A working version of the vent was also produced by that date, and operational vent control was achieved and tested over RockBlock on that day. A final integration session installed the vent on November 16.

The chief goals of these tests were to determine the mass capacity of the ZPB envelope, test the envelope at full volumetric strain, and obtain a rough estimate of vent rate. For details, please see the appropriate document in the Cycloon Google drive.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, various topologies, width 2.5 m, various lengths and volumes. PVC of length approximately 12 inches and diameter 1/2 inch, as usual.

'''Avionics''': Teensy 3.2 transmitting at adjustable intervals over Rockblock. Vent controlled by TB6612 motor driver.

'''Power''': 3 L91 lithium AA batteries.

'''Vent''': Cycloon zero-pressure

'''Payload''': Half valbal-style polycarbonate cylinder within styrofoam enclosure. Mass 1.25 kg including ballast.

'''Mass budget''': Various

==Flight synopsis==

Since this was a series of ground tests, no flight synopsis is available. Please see the test report in the Cycloon Google Drive.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-97

2019-12-07T23:04:14Z

Bjing:

{{balloon-launch
| header = SSI-97
| img link =
| designations = '''CY-8'''
| launch date = November 17, 2019
| launch site = Pigeon Point Light Station, Pescadero, CA
| launch coordinates = 37.1827, -122.3923
| flight duration =
| flight length =
| flight profile = Ground tests
| landing time =
| landing site=
| landing coordinates =
| last = 93
| next =
}}

'''SSI-97''' (project designation '''CY-8''') was the seventh launch of [[Cycloon|Project Cycloon]] on November 17, 2019. Not a true launch, it was instead a series of ground tests of various properties of polyethylene tubing envelopes and the newly designed Cycloon vent mechanism. It was also the first return of Cycloon to Pigeon Point since the first launch, [[SSI-83]].

==Project context==

The original launch schedule for the quarter had called for a second altitude controlled flight in mid-November after a first test in October, [[SSI-93]]. When that first test became a ballast-only flight, the November flight would have been the first altitude-controlled flight. However, the outcome of SSI-93 demonstrated that Cycloon needed a better understanding of zero pressure balloons, a more rigorous pre-launch procedure, checklists, and better balloon envelope quality control. Thus, it was decided to conduct a series of ground tests for that purpose. Additionally, as the first version of a Cycloon vent mechanism was approaching completion, it was decided to test this mechanism on a ZPB envelope. Initially scheduled for '''November 16''', the tests were pushed back one day to accommodate schedules.

The simple avionics for these tests were constructed on November 8, followed by the balloons on November 14. A working version of the vent was also produced by that date, and operational vent control was achieved and tested over RockBlock on that day. A final integration session installed the vent on November 16.

The chief goals of these tests were to determine the mass capacity of the ZPB envelope, test the envelope at full volumetric strain, and obtain a rough estimate of vent rate. For details, please see the appropriate document in the Cycloon Google drive.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, various topologies, width 2.5 m, various lengths and volumes. PVC of length approximately 12 inches and diameter 1/2 inch, as usual.

'''Avionics''': Teensy 3.2 transmitting at adjustable intervals over Rockblock. Vent control.

'''Power''': 3 L91 lithium AA batteries.

'''Vent''': Cycloon zero-pressure

'''Payload''': Half valbal-style polycarbonate cylinder within styrofoam enclosure. Mass 1.25 kg including ballast.

'''Mass budget''': Various

==Flight synopsis==

Since this was a series of ground tests, no flight synopsis is available. Please see the test report in the Cycloon Google Drive.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-97

2019-12-07T23:02:50Z

Bjing:

{{balloon-launch
| header = SSI-97
| img link =
| designations = '''CY-8'''
| launch date = November 17, 2019
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration =
| flight length =
| flight profile = Ground tests
| landing time =
| landing site=
| landing coordinates =
| last = 93
| next =
}}

'''SSI-97''' (project designation '''CY-8''') was the seventh launch of [[Cycloon|Project Cycloon]] on November 17, 2019. Not a true launch, it was instead a series of ground tests of various properties of polyethylene tubing envelopes and the newly designed Cycloon vent mechanism. It was also the first return of Cycloon to Pigeon Point since the first launch, [[SSI-83]].

==Project context==

The original launch schedule for the quarter had called for a second altitude controlled flight in mid-November after a first test in October, [[SSI-93]]. When that first test became a ballast-only flight, the November flight would have been the first altitude-controlled flight. However, the outcome of SSI-93 demonstrated that Cycloon needed a better understanding of zero pressure balloons, a more rigorous pre-launch procedure, checklists, and better balloon envelope quality control. Thus, it was decided to conduct a series of ground tests for that purpose. Additionally, as the first version of a Cycloon vent mechanism was approaching completion, it was decided to test this mechanism on a ZPB envelope. Initially scheduled for '''November 16''', the tests were pushed back one day to accommodate schedules.

The simple avionics for these tests were constructed on November 8, followed by the balloons on November 14. A working version of the vent was also produced by that date, and operational vent control was achieved and tested over RockBlock on that day. A final integration session installed the vent on November 16.

The chief goals of these tests were to determine the mass capacity of the ZPB envelope, test the envelope at full volumetric strain, and obtain a rough estimate of vent rate. For details, please see the appropriate document in the Cycloon Google drive.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, various topologies, width 2.5 m, various lengths and volumes. PVC of length approximately 12 inches and diameter 1/2 inch, as usual.

'''Avionics''': Teensy 3.2 transmitting at adjustable intervals over Rockblock. Vent control.

'''Power''': 3 L91 lithium AA batteries.

'''Vent''': Cycloon zero-pressure

'''Payload''': Half valbal-style polycarbonate cylinder within styrofoam enclosure. Mass 1.25 kg including ballast.

'''Mass budget''': Various

==Flight synopsis==

Since this was a series of ground tests, no flight synopsis is available. Please see the test report in the Cycloon Google Drive.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-97

2019-12-07T22:39:10Z

Bjing:

SSI-92

2019-12-07T22:34:16Z

Bjing:

{{balloon-launch
| header = SSI-92
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length = 564 km
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]]).

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi92rates.png|400px|thumb|right|Ascent rates against altitude]]

[[File:Ssi92profile.png|600px|thumb|right|Flight profile]]
Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

[[File:Ssi92traj.png|800px|thumb|center|Flight trajectory up until loss of GPS]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

Cycloon

2019-12-07T22:15:39Z

Bjing:

[[File:Cycloon.png|400px|thumb|Project components]]
'''Project Cycloon''' ({{slack-channel|balloons-cycloon}}) is a core project on SSI's [[Balloons]] team with the aim of designing and operating altitude-controlled, long-endurance, aero-marine balloon platforms for tropical cyclone research. Begun in January 2019, Cycloon has launched five payloads as of August 2019 and has deployed proof-of-concepts of several novel techniques in high-altitude ballooning, as well as giving rise to [[HABSIM]]. Please contact the current co-leads of Cycloon, {{slack-user|bjing}} and {{slack-user|jtang}}, to get involved!

All flight code, simulations, communications protocols, and flight data/analysis for Cycloon are maintained on [https://github.com/stanford-ssi/cycloon GitHub] and repository notifications arrive in {{slack-channel|balloons-cy-git}}. The flight control channel is {{slack-channel|balloons-cy-flops}}.

==Aims==
Balloons platforms exhibit a very wide range of operating altitudes, making them uniquely well suited to study the [https://en.wikipedia.org/wiki/Tropical_cyclone#Physics_and_energetics secondary circulation and energetics] of tropical systems. Understanding such aspects of tropical cyclones is key to improving forecast models of cyclone intensity, whose reliability has lagged significantly behind that of storm track forecasts. [https://en.wikipedia.org/wiki/Hurricane_Michael Hurricane Michael] is a prime example of a storm where poor intensity forecasts resulted in substantial loss of life and property and was a key inspiration for the project. Additionally, balloons platforms can be deployed at significantly lower cost than planes and buoys, and are therefore significantly more scalable.

Key projects being undertaken within Cycloon (and their respective Slack channels) include:

*'''Altitude control:''' Cycloon aims to master and extend the legacy of altitude control on latex balloons pioneered by previous SSI projects. This entails both mechanical and algorithmic aspects. Design and production of the primary vent and ballast mechanisms is undertaken in {{slack-channel|balloons-cy-platform}}.
*'''Marine tether:''' In order to extend the flight endurance beyond the inherent limitations of latex, Cycloon is developing an tether and floater to rest on the surface of the ocean for days at a time. This architecture was successfully demonstrated in [[SSI-83|CY-1]].
*'''Simulations:''' The need to predict trajectories from California to the Pacific and Atlantic topical basins using the GEFS forecast ensemble has given rise to [[HABSIM]] and its associated work. See also {{slack-channel|balloons-cy-sims}}.
*'''Payload:''' Ultimately, the purpose of the balloon platform will be to carry low-cost, lightweight radiosondes. See {{slack-channel|balloons-cy-dropsonde}}.
*'''Communications:''' To augment data uplink rates, Cycloon is developing a skywave communications system and protocol in {{slack-channel|balloons-cy-comms}}.
*'''Avionics:''' Core avionics work involving circuit board design and flight code is undertaken in {{slack-channel|balloons-cy-avionics}}.
*'''ZPB:''' Polyethylene envelopes have intrinsically more desirable properties compared to latex envelopes. In-house manufacture of such envelopes is being explored in {{slack-channel|balloons-cy-zpb}} and was first demonstrated in [[SSI-90|CY-4]].
==Missions==
{| class="wikitable" style="margin: auto;"
!|Number
!|Link
!|Launch date
!|Launch site
!|Flight duration
!|Notes
|-
|1
! [[File:Ssi83.png|200px|frameless|link=SSI-83]]
| April 17, 2019
| Pigeon Point
| 60 hours, 33 minutes
| Demonstration of long-endurance marine tether. Float-only profile. Lost off the coast of San Luis Obispo county.
|-
|2
! [[File:SSI-86.png|200px|frameless|link=SSI-86]]
| May 18, 2019
| Hollister
| 5 hours, 12 minutes + 5 hours, 40 minutes
| Latex ballast control. Flight through inclement weather and resumption of flight after 24 hours. Final location in Yosemite National Park.
|-
|3
! [[SSI-87]]
| June 1, 2019
| Le Grand
| 3 hours, 52 minutes
| Latex full altitude control. Recovered from near Mendota, California on June 1, 2019.
|-
|4
! [[SSI-90]]
| July 27, 2019
| Hollister
| Unknown
| First flight of in-house constructed polyethylene envelope. Telemetry error; final location unknown.
|-
|5
! [[SSI-91]]
| August 5, 2019
| Hollister
| 2 hours, 0 minutes
| Second flight of in-house constructed polyethylene envelope. Recovered from near Tracy, CA on August 31, 2019.
|-
|6
! [[SSI-92]]
| October 5, 2019
| Hollister
| 9 hours, 28 minutes
| First polyethylene tubing envelope. First SSI ZPB flight with full telemetry. First interstate Cycloon flight. Final location near Alamo, NV.
|-
|7
! [[SSI-93]]
| October 27, 2019
| Hollister
| 4 hours, 4 minutes
| First ballast-controlled ZPB. Eventful launch and post-landing. Final location near Tulare, CA.
|-
|8
! [[SSI-97]]
| November 17, 2019
| Pigeon Point
| N/A
| Extensive ZPB ground tests.
|}

[[Category: High Altitude Balloons]]

SSI-93

2019-12-07T22:14:38Z

Bjing:

{{balloon-launch
| header = SSI-93
| img link =
| designations = '''CY-7'''
| launch date = October 26, 2019, 10:14 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 4h:04m
| flight length = 202 km
| flight profile = Folded zero pressure w/ ballast control
| landing time = October 27, 2019, 14:18 PDT
| landing site=9 km SW of Tulare, Tulare County, CA
| landing coordinates = 36.164, -119.431
| last = 92
| next = 97
}}

'''SSI-93''' (project designation '''CY-7''') was the seventh launch of [[Cycloon|Project Cycloon]] on October 26, 2019. It was the zero pressure balloon equipped with altitude control (ballast mechanism), and launched alongside two other zero-pressure balloons at Onboarding. It was the first balloon in the folded topology as a result of a notably eventful filling, and consequently also experienced a noteable post-landing.

==Project context==

The launch plan at the beginning of the quarter had called for a fully controlled ZPB flight coincident with onboarding on '''October 26, 2019'''. However, the unavailability of a vent mechanism and the surprising endurance of [[SSI-92]] motivated the decision to do a long-endurance ballast-controlled ZPB instead. The analysis of data from that previous flight had suggested a thermal difference of 10% during the day; given this, it seemed possible to aim for a multi-day flight with a reasonable amount of ballast. Briefly, on October 18, a floater was considered as the forecast appeared to show winds going towards the ocean, but this was temporary. The primary upgrades, in addition to the vent mechanism, were a heating mechanism and a GPS reset mechanism, lessons learned from the last flight.

Construction of the payload was a streamlined process by this time. Avionics were produced in an October 15 worksession; on October 18 a large number of balloons were manufactured for Onboarding; and on October 20, the payload was integrated, marking launch readiness a week ahead of time. The integration of the payload was tricky, as no top piece was suitable for the legacy ballast piece, and furthermore thermal insulation was a concern. Therefore the bottom half of the polyethylene enclosure was placed inside the styrofoam enclosure.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, folded topology, width 2.5 m, length 10 m, volume unknown. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. SPOT Trace. Ballast control; nichrome cutdown; GPS power reset MOSFET.

'''Power''': 12 L91 lithium AA batteries. 3 L91 lithium AA batteries on resistive heater and cutdown.

'''Ballast''': Legacy valbal mechanism with 500 g ballast, theoretically enough for two nightfalls.

'''Payload''': Half valbal-style polycarbonate cylinder within styrofoam enclosure. Mass 1.25 kg including ballast.

'''Mass budget''': 2.26 kg total.

==Flight synopsis==

[[File:Ssi93rates.png|400px|thumb|right|Ascent rates against altitude]]

[[File:ssi93profile.png|600px|thumb|right|Flight profile]]

'''October 26 953 PDT:''' Balloon released after an attempted titration to 0.5 kg of free lift. Moderate winds made this difficult. However, within a few dozen seconds of release the balloon began to descend, and was caught barely within the southwestern boundaries of Brigantino park. A large leak at the top seal was discovered, motivating the decision to fold the envelope over. The balloon was re-filled and observed for 10 minutes for second release.

'''October 26 1014 PDT:''' Balloon released at approximate 1.5 m/s ascent with initial motion to the southwest.

'''October 26 1126 PDT:''' Balloon reached 8438 m at an ascent rate of 2.5 m/s over (36.636, -121.0770), heading southeast over the Diablo range.

'''October 26 1136 PDT:''' Balloon reported an altitude of 10034 m. In post-analysis, it is clear that this transmission marked the beginning of a second phase of the flight, during which the balloon smoothly decelerated into a terminal descent. The cause and nature of this transition remains completely unknown.

'''October 26 1156 PDT:''' A maximum altitude of 10464 m was reported. At the time it was believed that the balloon had equilibrated. This was not a surprise, since the folded topology would have had a much smaller maximum volume, but was still a concerning altitude.

'''October 26 1228 PDT:''' At the 9619 m, the balloon was clearly descending at 1 m/s and clearly had not equilibrated.

'''October 26 1242 PDT:''' A ballast command of 16 seconds was sent in hopes of reestablishing equilibrium. By this time the balloon was at 8.5 km descending at approximate 1 m/s, and the ballast command had no effect.

'''October 26 1256 PDT:''' A ballast command of 64 seconds was sent in a last ditch effort. By this time the balloon was at 7.5 km descending at 1.5 m/s, a rate which it would maintain until landing.

'''October 26 1312 PDT:''' Although equilibrium and endurance was clearly out of the question now, it was noted that none of the ballast commands had any effect whatsoever, calling into question its operation. To verify this, a 100 second command was sent, which finally did evoke a temporary but insignificant perturbation. At this point the balloon was just below 6 km and was approaching its final landing location.

'''October 26 1418 PDT:''' The balloon reached ground level at its landing location. However, this was only apparent in retrospect, as for the next thirty minutes, the balloon appeared to rise over 50 m and fall again twice, and moved approximately one km to the southeast. It is likely that due to the folded topology and mostly inflated envelope, the balloon was blown around substantially by the wind.

'''October 26 1434 PDT:''' The balloon appears to comes to rest at ground level near (36.154, -119.425), yet its coordinates continued to fluctuate.

'''October 26 1443 PDT:''' The BMP malfunctioned and began to report erroneous data for unknown reasons. In conjunction with the strange motions, it is possible the balloon was picked up at this point.

'''October 26 1510 PDT:''' After a 18 minute break in comms, the payload suddenly moved to (36.167, -119.384). It remained in this general vicinity for the next two hours, although coordinates continued to fluctuate and comms intervals continued to be longer than expected.

'''October 26 1713 PDT:''' RockBlock reported a final coordinate of (36.165, -119.389).

In the ensuing hours, SPOT messages reported movement to the east side of Tulare highly consistent with a motor vehicle. The payload appeared to have been moved to two facilities that evening, and again the following morning. The last ping was at October 27 946 PDT from (36.18316,-119.33084), a gas station.

[[File:Ssi93traj.png|800px|thumb|center|Flight trajectory]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-93

2019-12-07T21:39:29Z

Bjing:

High Altitude Balloons Team

2019-12-06T21:35:52Z

Bjing:

[[File: BalloonSelfie.png|left|frame|A photo of the edge of space, taken by [[SSI-23]], Gemini]]
The Balloon team constructs and launches high altitude latex balloons with experimental payloads. To date, the team has launched and recovered nearly 100 high altitude balloons to as high as 120,000 feet with thermal controls, satellite communication, and scientific payloads. They have launched a balloon all the way across the Atlantic Ocean from California, and are currently working to enable balloons to fly even further. The Balloons Team Faculty Advisor is Dr. John Pauly.

Balloon payloads are launched with state-of-the-art equipment constantly re-envisioned by the team. Recent additions include altitude control mechanics for latex balloons, including a gas venting valve and ballast dispenser, as well as a custom flight control system, two-way satellite communications, an intelligent altitude control algorithm, and more. The goal of the team is to push the bounds on its current latex balloon flight hardware, both in terms of flight time and flight distance.

The current team co-leads are Aditeya Shuka ({{slack-user|Adi}}) and Sathya Edamadaka ({{slack-user|sathya}}). The co-leads in 2019 were Sydney Marler ({{slack-user|smarler}}) and Jason Kurohara ({{slack-user|jason kurohara}}). 

The core of the Balloons team is a set of long-term technical projects. Current projects include: 
[[Cycloon]], which aims to harness altitude control technology and the unique advantages of a balloon platform to study tropical cyclogenesis. 
[[HABSIM]], a GEFS-based trajectory prediction server and an associated Python package enabling predictions and optimizations on custom profiles. 
[[Spaceshot]], which aims to launch a rocket off a high-altitude balloon to reach space. 
[[HABMC]], the balloons team mission-control software, a powerful web-app that provides real-time data, analytics, and controls of balloon flights. 
[[Balloonerang]], which aims to build a payload which returns to its launch site after cutdown. 

Previous projects include: 
'''ValBal''', a long-endurance, low-cost latex balloon altitude-maintenance platform that holds multiple world records for endurance, and has flown as far as Morocco. 
'''HABEES''', the balloons project team responsible for all balloons standard-profile electronics, RF, and flight software systems. 
'''habhive''', the balloons mechanical-engineering project team, responsible for development of payload structures & novel mechanical projects to be flown on balloons. 

The balloons team is committed to openness and diversity in projects; project teams serve to facilitate member interests and novel new ideas and propositions; talk to the balloon co-leads or the relevant project leads if you have an awesome idea you'd like to try out! 

{|align="center"
|-
| [[File:valballogo.png | 200px| link=Category:ValBal]]
| [[File:habeeslogo.JPG | 200px | link=Category:HABEES]]
| [[File:habhivelogo.png | 200px | link=Category:habhive]]
| [[File:habmclogo.png | 200px | link=Category:habmc]]
|-
|}

{{balloon-footer}}
<noinclude>[[Category:High Altitude Balloons]]</noinclude>

SSI-93

2019-12-06T10:03:26Z

Bjing:

SSI-92

2019-12-06T09:58:22Z

Bjing:

{{balloon-launch
| header = SSI-92
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length = 564 km
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi92rates.png|400px|thumb|right|Ascent rates against altitude]]

[[File:Ssi92profile.png|600px|thumb|right|Flight profile]]
Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

[[File:Ssi92traj.png|800px|thumb|center|Flight trajectory up until loss of GPS]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-93

2019-12-06T09:56:33Z

Bjing:

File:Ssi93traj.png

2019-12-06T09:47:02Z

Bjing:

SSI-93

2019-12-06T09:45:05Z

Bjing:

{{balloon-launch
| header = SSI-93
| img link =
| designations = '''CY-7'''
| launch date = October 26, 2019, 10:14 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 4h:04m
| flight length = 202 km
| flight profile = Folded zero pressure w/ ballast control
| landing time = October 27, 2019, 14:18 PDT
| landing site=9 km SW of Tulare, Tulare County, CA
| landing coordinates = 36.164, -119.431
| last = 92
| next = 97
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:Ssi93rates.png|400px|thumb|right|Ascent rates against altitude]]

[[File:ssi93profile.png|600px|thumb|right|Flight profile]]
Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

[[File:Ssi92traj.png|800px|thumb|center|Flight trajectory up until loss of GPS]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

File:Ssi93rates.png

2019-12-06T09:44:20Z

Bjing:

File:Ssi93profile.png

2019-12-06T09:44:10Z

Bjing:

SSI-97

2019-12-06T09:40:36Z

Bjing:

SSI-93

2019-12-06T09:39:26Z

Bjing:

Cycloon

2019-12-06T09:24:47Z

Bjing:

[[File:Cycloon.png|400px|thumb|Project components]]
'''Project Cycloon''' ({{slack-channel|balloons-cycloon}}) is a core project on SSI's [[Balloons]] team with the aim of designing and operating altitude-controlled, long-endurance, aero-marine balloon platforms for tropical cyclone research. Begun in January 2019, Cycloon has launched five payloads as of August 2019 and has deployed proof-of-concepts of several novel techniques in high-altitude ballooning, as well as giving rise to [[HABSIM]]. Please contact the current co-leads of Cycloon, {{slack-user|bjing}} and {{slack-user|jtang}}, to get involved!

All flight code, simulations, communications protocols, and flight data/analysis for Cycloon are maintained on [https://github.com/stanford-ssi/cycloon GitHub] and repository notifications arrive in {{slack-channel|balloons-cy-git}}. The flight control channel is {{slack-channel|balloons-cy-flops}}.

==Aims==
Balloons platforms exhibit a very wide range of operating altitudes, making them uniquely well suited to study the [https://en.wikipedia.org/wiki/Tropical_cyclone#Physics_and_energetics secondary circulation and energetics] of tropical systems. Understanding such aspects of tropical cyclones is key to improving forecast models of cyclone intensity, whose reliability has lagged significantly behind that of storm track forecasts. [https://en.wikipedia.org/wiki/Hurricane_Michael Hurricane Michael] is a prime example of a storm where poor intensity forecasts resulted in substantial loss of life and property and was a key inspiration for the project. Additionally, balloons platforms can be deployed at significantly lower cost than planes and buoys, and are therefore significantly more scalable.

Key projects being undertaken within Cycloon (and their respective Slack channels) include:

*'''Altitude control:''' Cycloon aims to master and extend the legacy of altitude control on latex balloons pioneered by previous SSI projects. This entails both mechanical and algorithmic aspects. Design and production of the primary vent and ballast mechanisms is undertaken in {{slack-channel|balloons-cy-platform}}.
*'''Marine tether:''' In order to extend the flight endurance beyond the inherent limitations of latex, Cycloon is developing an tether and floater to rest on the surface of the ocean for days at a time. This architecture was successfully demonstrated in [[SSI-83|CY-1]].
*'''Simulations:''' The need to predict trajectories from California to the Pacific and Atlantic topical basins using the GEFS forecast ensemble has given rise to [[HABSIM]] and its associated work. See also {{slack-channel|balloons-cy-sims}}.
*'''Payload:''' Ultimately, the purpose of the balloon platform will be to carry low-cost, lightweight radiosondes. See {{slack-channel|balloons-cy-dropsonde}}.
*'''Communications:''' To augment data uplink rates, Cycloon is developing a skywave communications system and protocol in {{slack-channel|balloons-cy-comms}}.
*'''Avionics:''' Core avionics work involving circuit board design and flight code is undertaken in {{slack-channel|balloons-cy-avionics}}.
*'''ZPB:''' Polyethylene envelopes have intrinsically more desirable properties compared to latex envelopes. In-house manufacture of such envelopes is being explored in {{slack-channel|balloons-cy-zpb}} and was first demonstrated in [[SSI-90|CY-4]].
==Missions==
{| class="wikitable" style="margin: auto;"
!|Number
!|Link
!|Launch date
!|Launch site
!|Flight duration
!|Notes
|-
|1
! [[File:Ssi83.png|200px|frameless|link=SSI-83]]
| April 17, 2019
| Pigeon Point
| 60 hours, 33 minutes
| Demonstration of long-endurance marine tether. Float-only profile. Lost off the coast of San Luis Obispo county.
|-
|2
! [[File:SSI-86.png|200px|frameless|link=SSI-86]]
| May 18, 2019
| Hollister
| 5 hours, 12 minutes + 5 hours, 40 minutes
| Latex ballast control. Flight through inclement weather and resumption of flight after 24 hours. Final location in Yosemite National Park.
|-
|3
! [[SSI-87]]
| June 1, 2019
| Le Grand
| 3 hours, 52 minutes
| Latex full altitude control. Recovered from near Mendota, California on June 1, 2019.
|-
|4
! [[SSI-90]]
| July 27, 2019
| Hollister
| Unknown
| First flight of in-house constructed polyethylene envelope. Telemetry error; final location unknown.
|-
|5
! [[SSI-91]]
| August 5, 2019
| Hollister
| 2 hours, 0 minutes
| Second flight of in-house constructed polyethylene envelope. Recovered from near Tracy, CA on August 31, 2019.
|-
|6
! [[SSI-92]]
| October 5, 2019
| Hollister
| 9 hours, 28 minutes
| First polyethylene tubing envelope. First SSI ZPB flight with full telemetry. First interstate Cycloon flight. Final location near Alamo, NV.
|-
|7
! [[SSI-93]]
| October 27, 2019
| Hollister
| 4 hours, 4 minutes
| First ballast-controlled ZPB. Eventful launch and post-landing. Final location near Tulare, NV.
|-
|8
! [[SSI-97]]
| November 17, 2019
| Pigeon Point
| N/A
| Extensive ZPB ground tests.
|}

[[Category: High Altitude Balloons]]

SSI-93

2019-12-06T09:24:33Z

Bjing:

Cycloon

2019-12-06T09:05:17Z

Bjing:

[[File:Cycloon.png|400px|thumb|Project components]]
'''Project Cycloon''' ({{slack-channel|balloons-cycloon}}) is a core project on SSI's [[Balloons]] team with the aim of designing and operating altitude-controlled, long-endurance, aero-marine balloon platforms for tropical cyclone research. Begun in January 2019, Cycloon has launched five payloads as of August 2019 and has deployed proof-of-concepts of several novel techniques in high-altitude ballooning, as well as giving rise to [[HABSIM]]. Please contact the current co-leads of Cycloon, {{slack-user|bjing}} and {{slack-user|jtang}}, to get involved!

All flight code, simulations, communications protocols, and flight data/analysis for Cycloon are maintained on [https://github.com/stanford-ssi/cycloon GitHub] and repository notifications arrive in {{slack-channel|balloons-cy-git}}. The flight control channel is {{slack-channel|balloons-cy-flops}}.

==Aims==
Balloons platforms exhibit a very wide range of operating altitudes, making them uniquely well suited to study the [https://en.wikipedia.org/wiki/Tropical_cyclone#Physics_and_energetics secondary circulation and energetics] of tropical systems. Understanding such aspects of tropical cyclones is key to improving forecast models of cyclone intensity, whose reliability has lagged significantly behind that of storm track forecasts. [https://en.wikipedia.org/wiki/Hurricane_Michael Hurricane Michael] is a prime example of a storm where poor intensity forecasts resulted in substantial loss of life and property and was a key inspiration for the project. Additionally, balloons platforms can be deployed at significantly lower cost than planes and buoys, and are therefore significantly more scalable.

Key projects being undertaken within Cycloon (and their respective Slack channels) include:

*'''Altitude control:''' Cycloon aims to master and extend the legacy of altitude control on latex balloons pioneered by previous SSI projects. This entails both mechanical and algorithmic aspects. Design and production of the primary vent and ballast mechanisms is undertaken in {{slack-channel|balloons-cy-platform}}.
*'''Marine tether:''' In order to extend the flight endurance beyond the inherent limitations of latex, Cycloon is developing an tether and floater to rest on the surface of the ocean for days at a time. This architecture was successfully demonstrated in [[SSI-83|CY-1]].
*'''Simulations:''' The need to predict trajectories from California to the Pacific and Atlantic topical basins using the GEFS forecast ensemble has given rise to [[HABSIM]] and its associated work. See also {{slack-channel|balloons-cy-sims}}.
*'''Payload:''' Ultimately, the purpose of the balloon platform will be to carry low-cost, lightweight radiosondes. See {{slack-channel|balloons-cy-dropsonde}}.
*'''Communications:''' To augment data uplink rates, Cycloon is developing a skywave communications system and protocol in {{slack-channel|balloons-cy-comms}}.
*'''Avionics:''' Core avionics work involving circuit board design and flight code is undertaken in {{slack-channel|balloons-cy-avionics}}.
*'''ZPB:''' Polyethylene envelopes have intrinsically more desirable properties compared to latex envelopes. In-house manufacture of such envelopes is being explored in {{slack-channel|balloons-cy-zpb}} and was first demonstrated in [[SSI-90|CY-4]].
==Missions==
{| class="wikitable" style="margin: auto;"
!|Number
!|Link
!|Launch date
!|Launch site
!|Flight duration
!|Notes
|-
|1
! [[File:Ssi83.png|200px|frameless|link=SSI-83]]
| April 17, 2019
| Pigeon Point
| 60 hours, 33 minutes
| Demonstration of long-endurance marine tether. Float-only profile. Lost off the coast of San Luis Obispo county.
|-
|2
! [[File:SSI-86.png|200px|frameless|link=SSI-86]]
| May 18, 2019
| Hollister
| 5 hours, 12 minutes + 5 hours, 40 minutes
| Latex ballast control. Flight through inclement weather and resumption of flight after 24 hours. Final location in Yosemite National Park.
|-
|3
! [[SSI-87]]
| June 1, 2019
| Le Grand
| 3 hours, 52 minutes
| Latex full altitude control. Recovered from near Mendota, California on June 1, 2019.
|-
|4
! [[SSI-90]]
| July 27, 2019
| Hollister
| Unknown
| First flight of in-house constructed polyethylene envelope. Telemetry error; final location unknown.
|-
|5
! [[SSI-91]]
| August 5, 2019
| Hollister
| 2 hours, 0 minutes
| Second flight of in-house constructed polyethylene envelope. Recovered from near Tracy, CA on August 31, 2019.
|-
|6
! [[SSI-92]]
| October 5, 2019
| Hollister
| 9 hours, 28 minutes
| First polyethylene tubing envelope. First SSI ZPB flight with full telemetry. First interstate Cycloon flight. Final location near Alamo, NV.
|-
|7
! [[SSI-93]]
| October 27, 2019
| Hollister
| 4 hours, 20 minutes
| First ballast-controlled ZPB. Eventful launch and post-landing. Final location near Tulare, NV.
|-
|8
! [[SSI-97]]
| November 17, 2019
| Pigeon Point
| N/A
| Extensive ZPB ground tests.
|}

[[Category: High Altitude Balloons]]

SSI-93

2019-12-06T09:02:20Z

Bjing:

SSI-92

2019-12-06T08:47:41Z

Bjing:

{{balloon-launch
| header = SSI-92
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi92rates.png|400px|thumb|right|Ascent rates against altitude]]

[[File:Ssi92profile.png|600px|thumb|right|Flight profile]]
Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

[[File:Ssi92traj.png|800px|thumb|center|Flight trajectory up until loss of GPS]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-92

2019-12-06T08:46:00Z

Bjing:

{{balloon-launch
| header = SSI-92
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi92rates.png|400px|thumb|right|Ascent rates against altitude]]

Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

[[File:Ssi92profile.png|800px|thumb|center|Flight profile]]
{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

File:Ssi92traj.png

2019-12-06T08:45:54Z

Bjing:

File:Ssi92rates.png

2019-12-06T08:42:01Z

Bjing:

File:Ssi92profile.png

2019-12-06T08:41:50Z

Bjing:

SSI-92

2019-12-06T08:39:36Z

Bjing:

{{balloon-launch
| header = SSI-92
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-92

2019-12-06T08:39:14Z

Bjing:

{{balloon-launch
| header = SSI-82
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight (and to-date longest distance), the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered from [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Conditions at the launch site were ideal. Inflation was remarkably uneventful.

'''October 5 1100 PDT:''' Balloon released --- no running start needed. Free lift was measured at approximately 0.5 kg. Initial ascent at about 2.5 m/s. Nearly no horizontal initial motion, followed by a gradual drift to the southwest and then southeast.

'''October 5 1219 PDT:''' Balloon appeared to equilibrate at 17.43 km, having ascended at 4 - 5 m/s in the second half of its ascent. Within significant figures, this was essential equal to the predicted equilibration altitude of 17.37 km. At the point the balloon had been moving due east and had been crossing the Diablo range.

'''October 5 1225 PDT''' Balloon reached a maximum altitude of 17463 m, at 36.929, -120.947 over the eastern foothills of the Diablo range. In the ensuing hours, the trajectory fluctuated within the rates of +/- 0.3 m/s, which was considered a very successful equilibration.

'''October 5 1547 PDT''' At this time, the balloon was over the peaks of the Sierra Nevada (John Muir wilderness), yet still held an altitude of 16.4 km.

'''October 5 1602 PDT''' GPS lost lock over 37.198, -118.72 at an altitude of 16330 km. This sparked intense speculation, and the rapidly dropping temperature of -22 C was momentarily blamed. During the lock, the barometer and Iridium triangulation functioned as telemetry.

'''October 5 1729 PDT''' In the previous 15 minutes, Iridium had been reporting with increasing confidence from Nevada, so an interstate transition was declared. By this time, the balloon was just above 15 km in altitude, having stalled its descent over the past half hour. Now, however, descent began in earnest.

'''October 5 1839 PDT''' Altitude was around 13.8 km, and descent rate increased to around 1 m/s, marking an inflection point. Landing was predicted near St George, UT.

'''October 5 1903 PDT''' Altitude near 11.5 km. Descent rate stabilized near 2 m/s and fluctuated around this value for the next hour or so.

'''October 5 1917 PDT''' GPS signal returned at an altitude of 9745 m. The temperature was -37 C, disfavoring the cold hypothesis. Instead, the threshholds of 10 km and 1600 PDT were noted with suspicion.

'''October 5 1924 PDT''' At an altitude of 8914 m and a descent rate just above 2 m/s, an impact at 2030 PDT near US-93 was predicted.

'''October 5 1828 PDT''' Landing declared at a ground elevation of 1511 m. Descent just before impact had slowed somewhat, consistent with predictions.

'''October 9 1035 PDT''' Last RockBlock comm, having shown no movement since landing.

'''Otober

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-92

2019-12-06T07:47:57Z

Bjing:

{{balloon-launch
| header = SSI-82
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight, the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions. Continuing a trend, the payload was lighter still than that of its predecessor, [[SSI-91]].

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, it was decided to fly only one standard (non-controlled) ZPB. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively close to the day of the launch, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.8 mil polyethylene tubing, paper bag topology, width 2.5 m, length 10 m, volume approximately 17.5 cubic meters. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. A SPOT Trace was accidentally omitted. This set of avionics was recovered [[SSI-91|CY-5]]. Controlled novel cutdown mechanism.

'''Power''': 9 L91 lithium AA batteries. 3 L91 lithium AA batteries on cutdown.

'''Payload''': Styrofoam enclosure. Mass 0.55 kg

'''Mass budget''': 1.57 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Inflation was eventful thanks to strong ground winds from due west. The envelope ruptured midway through filling and was patched before refilling. Additionally, a hole approximately 5 mm in diameter was patched.

'''August 5 2011 PDT:''' Balloon released from a running start. Initial motion to the east at an ascent rate of 3.8 m/s --- significantly faster than the target ascent rate of 2.5 m/s.

'''August 5 2059 PDT:''' After almost an hour of steady ascent, balloon reaches a maximum altitude of 10.298 km over (37.1502, -121.4077). Ascent rate had fluctuated above and below the initial rate of 3.8 m/s. In theory, a slight acceleration in ascent was expected. By this time the balloon was in the jet stream layer travelling north at nearly 30 m/s.

'''August 5 2103 PDT:''' Balloon reported an altitude of 10.291 km, a highly unexpected measurement. In retrospect, it is believed that venting began at this altitude, but the vent hole was far too small to vent the necessary volume, leading to envelope rupture. The resulting leakage prevented the balloon from reaching the calculated equilibrium altitude of 14-15km and caused what more resembles a latex profile than a zero-pressure balloon profile.

'''August 5 2055 PDT:''' Balloon reported first definitive descent at an altitude of 9.905 km.

'''August 5 2213 PDT:''' After an hour of descent at 2.5 m/s - 3.0 m/s, balloon reported a ground elevation of 29 km. The landing site was less than 100 m from a road in an apple orchard.

'''August 9 0316 PDT:''' Last RockBlock transmission received, with no indication of movement since flight termination.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-92

2019-12-06T07:28:30Z

Bjing:

{{balloon-launch
| header = SSI-82
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight, the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions.

==Project context==

[[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

With the end of the summer, onboarding approached, and it was hoped to do a Cycloon demonstration launch very near the beginning of the year, on '''October 5, 2019'''. Ideally this would be ballast-controlled, collecting data and paving the way for a fully controlled launch in the middle of the quarter. It was also hoped to do this launch from Pigeon Point, but by September 23, wind forecasts proved unfavorable. Additionally, momentarily it was planned to launch two ballast controlled balloons (as a means of forcing Cycloon to self-manufacture a ballast mechanism), but as 3D printing attempts in the last week of September failed, this too was discarded. Nevertheless, a significant worksession on September 29 produced two balloons and two sets of avionics (one new, one recovered from [[SSI-91]].

Relatively near the flight, demands for an improved cutdown mechanism intensified. Amidst an absence of nichrome, a novel cutdown mechanism involving two ematches and a socket was devised, implemented, and tested the night of October 4.

==Configuration==

'''Balloon''': 0.3 mil polyethylene, paper bag topology, width 1.8 m, length 7 m, volume approximately 6 cubic meters. Total mass 0.26 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2 transmitting at adjustable intervals over Rockblock. SPOT Trace. Attempts to interface this Teensy with a BMP 280 were universally unsuccessful. This set of avionics was finished from the incomplete second set made for [[SSI-87|CY-3]].

'''Power''': 9 L91 lithium AA batteries. Resistive heater running on single L91 battery.

'''Payload''': Styrofoam enclosure. Mass 0.62 kg.

'''Mass budget''': 0.88 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Inflation was eventful thanks to strong ground winds from due west. The envelope ruptured midway through filling and was patched before refilling. Additionally, a hole approximately 5 mm in diameter was patched.

'''August 5 2011 PDT:''' Balloon released from a running start. Initial motion to the east at an ascent rate of 3.8 m/s --- significantly faster than the target ascent rate of 2.5 m/s.

'''August 5 2059 PDT:''' After almost an hour of steady ascent, balloon reaches a maximum altitude of 10.298 km over (37.1502, -121.4077). Ascent rate had fluctuated above and below the initial rate of 3.8 m/s. In theory, a slight acceleration in ascent was expected. By this time the balloon was in the jet stream layer travelling north at nearly 30 m/s.

'''August 5 2103 PDT:''' Balloon reported an altitude of 10.291 km, a highly unexpected measurement. In retrospect, it is believed that venting began at this altitude, but the vent hole was far too small to vent the necessary volume, leading to envelope rupture. The resulting leakage prevented the balloon from reaching the calculated equilibrium altitude of 14-15km and caused what more resembles a latex profile than a zero-pressure balloon profile.

'''August 5 2055 PDT:''' Balloon reported first definitive descent at an altitude of 9.905 km.

'''August 5 2213 PDT:''' After an hour of descent at 2.5 m/s - 3.0 m/s, balloon reported a ground elevation of 29 km. The landing site was less than 100 m from a road in an apple orchard.

'''August 9 0316 PDT:''' Last RockBlock transmission received, with no indication of movement since flight termination.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-92

2019-12-06T07:13:29Z

Bjing:

{{balloon-launch
| header = SSI-82
| img link =
| designations = '''CY-6'''
| launch date = October 5, 2019, 11:00 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.849, -121.433
| flight duration = 9h:28m
| flight length =
| flight profile = Standard zero pressure
| landing time = October 5, 2019, 20:38 PDT
| landing site=16 km SSW of Alamo, Lincoln County, NV
| landing coordinates = 37.144, -115.262
| last = 91
| next = 93
}}

'''SSI-92''' (project designation '''CY-6''') was the sixth launch of [[Cycloon|Project Cycloon]] on October 5, 2019. It was the first interstate Cycloon flight, the first launch of a poly tubing ZPB, and the first ZPB flight for which telemetry at equilibrium and descent was acquired since [[SSI-20]]. This enabled the acquisition of valuable thermal data and verification of equilibrium altitude predictions.

==Project context==

In August, [[SSI-91]] was a milestone in realizing flights with in-house manufactured ZPBs, yet due to unexpected termination no data on the equilibrium altitude and descent characteristics were obtained, thus failing to fulfill one of the major objectives of that flight. Meanwhile, a candid assessment of the ZPB manufacturing process proved discouraging. In mid to late August, a new manufacturing technique was devised based on commercially available polyethylene tubing, which promised to be far more durable and scalable. (The altitude limitations were deemed acceptable for the time being). Orders for commercial tubing were placed, set to arrive in September. In light of these developments, a third summer ZPB launch which had been planned for the weekend of September 1 was cancelled.

Thus, it was immediately decided that a repeat launch would be attempted, with nearly the exact same configurations, except for the addition of a SPOT Trace and strengthening of RockBlock connections. Since a repeat build would require little additional design work, it was decided that the repeat launch would be attempted on the evening of '''August 6, 2019''' from Pigeon Point.

As simulations from Pigeon Point showed the trajectory heading northeast over the Bay Area, it was decided on July 30 to request permission to launch from Garin Regional Park in Hayward, CA instead. That same day, avionics work began and was concluded on August 1. Due to the anticipated short duration of the flight, it was decided to reduce the power bank from 18 to 9 batteries. On July 31, the launch was moved to '''August 5, 2019''', and on August 2 the new launch site was rejected.

The construction of the ZPB and final payload assembly occurred on August 4. It was generally agreed that the quality of the balloon was inferior to that of the first attempt due to several reasons.

==Configuration==

'''Balloon''': 0.3 mil polyethylene, paper bag topology, width 1.8 m, length 7 m, volume approximately 6 cubic meters. Total mass 0.26 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2 transmitting at adjustable intervals over Rockblock. SPOT Trace. Attempts to interface this Teensy with a BMP 280 were universally unsuccessful. This set of avionics was finished from the incomplete second set made for [[SSI-87|CY-3]].

'''Power''': 9 L91 lithium AA batteries. Resistive heater running on single L91 battery.

'''Payload''': Styrofoam enclosure. Mass 0.62 kg.

'''Mass budget''': 0.88 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Inflation was eventful thanks to strong ground winds from due west. The envelope ruptured midway through filling and was patched before refilling. Additionally, a hole approximately 5 mm in diameter was patched.

'''August 5 2011 PDT:''' Balloon released from a running start. Initial motion to the east at an ascent rate of 3.8 m/s --- significantly faster than the target ascent rate of 2.5 m/s.

'''August 5 2059 PDT:''' After almost an hour of steady ascent, balloon reaches a maximum altitude of 10.298 km over (37.1502, -121.4077). Ascent rate had fluctuated above and below the initial rate of 3.8 m/s. In theory, a slight acceleration in ascent was expected. By this time the balloon was in the jet stream layer travelling north at nearly 30 m/s.

'''August 5 2103 PDT:''' Balloon reported an altitude of 10.291 km, a highly unexpected measurement. In retrospect, it is believed that venting began at this altitude, but the vent hole was far too small to vent the necessary volume, leading to envelope rupture. The resulting leakage prevented the balloon from reaching the calculated equilibrium altitude of 14-15km and caused what more resembles a latex profile than a zero-pressure balloon profile.

'''August 5 2055 PDT:''' Balloon reported first definitive descent at an altitude of 9.905 km.

'''August 5 2213 PDT:''' After an hour of descent at 2.5 m/s - 3.0 m/s, balloon reported a ground elevation of 29 km. The landing site was less than 100 m from a road in an apple orchard.

'''August 9 0316 PDT:''' Last RockBlock transmission received, with no indication of movement since flight termination.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

Template:Balloon-footer

2019-12-06T06:53:42Z

Bjing:

{| class="wikitable" style="margin: 1em auto 1em auto; font-size:85%;width:800px"
{{red-header|columns=2}}Balloon Launches
|-
{{red-header}} 2014-15
| [[SSI-19]] • [[SSI-20|20]] • [[SSI-21|21]] • [[SSI-22|22]]
|-
{{red-header}} 2015-16
| [[SSI-23]]([[SSI-23a|a]]) • [[SSI-24|24]] • [[SSI-25|25]] • [[SSI-26|26]] • [[SSI-27|27]] • [[SSI-28|28]] • [[SSI-29|29]] • [[SSI-30|30]] • [[SSI-31|31]] • [[SSI-32|32]] • [[SSI-33|33]] • [[SSI-34|34]] • [[SSI-35|35]] • [[SSI-36|36]] • [[SSI-37|37]] • [[SSI-38|38]] • [[SSI-39|39]] • [[SSI-40|40]] • [[SSI-41|41]] • [[SSI-42|42]] • [[SSI-43|43]]
|-
{{red-header}} 2016-17
| [[SSI-44|44]] • [[SSI-45|45]] • [[SSI-46|46]] • [[SSI-47|47]] • [[SSI-48|48]] • [[SSI-49|49]] • [[SSI-50|50]] • [[SSI-51|51]] • [[SSI-52|52]]
|-
{{red-header}} 2017-18
|
|-
{{red-header}} 2018-19
| [[SSI-83|83]] • [[SSI-86|86]] • [[SSI-87|87]] • [[SSI-90|90]] • [[SSI-91|91]]
|-
{{red-header}} 2019-20
| [[SSI-92|92]] • [[SSI-93|93]] • [[SSI-97|97]]
|-
{{red-header|textalign=right|columns=2}} [[Template:Balloon-footer | V]] • [http://wiki.stanfordssi.org/index.php?title=Template:Balloon-footer&action=edit E] 
|}

SSI-97

2019-12-06T06:53:08Z

Bjing: Created page with "{{balloon-launch | header = SSI-82 | img link = | designations = '''CY-6''' | launch date = October 5, 2019, 11:00 PDT | launch site = Brigantino Park, Hollister, CA | launc..."

SSI-93

2019-12-06T06:52:51Z

Bjing:

SSI-93

2019-12-06T06:52:42Z

SSI-92

2019-12-06T06:52:23Z

Bjing:

Cycloon

2019-12-06T06:50:19Z

Bjing:

File:Ssi87profile.png

2019-10-21T10:15:21Z

Bjing: Bjing uploaded a new version of File:Ssi87profile.png

File:Ssi87Rates.png

2019-10-21T10:15:06Z

Bjing: Bjing uploaded a new version of File:Ssi87Rates.png

SSI-87

2019-10-21T10:11:53Z

Bjing:

{{balloon-launch
| header = SSI-87
| img link =
| designations = '''CY-3'''
| launch date =June 1, 2019, 10:35 PDT
| launch site = Le Grand Elementary School, Le Grand, CA
| launch coordinates = 37.226, -120.251
| flight duration = 3h:52m
| flight length = unknown
| flight profile = Ballast and vent control
| landing time =June 1, 2019, 14:27 ODT
| landing site= 13 km SW of Mendota, Fresno County, CA
| landing coordinates = 36.692, -120.518
| last = 86
| next = 90
}}

'''SSI-87''' (project designation '''CY-3''') was the third launch of [[Cycloon|Project Cycloon]] on June 1, 2019. It featured a legacy ballast and vent mechanism from ValBal operated by Cycloon avionics and was the first such fully controlled Cycloon flight. The mission was noted for its eventful manual equilibration, early termination, and for being the last latex Cycloon before the project transitioned to polyethylene. The payload was recovered the afternoon of the launch.

==Project context==

Before and around the time of the previous flight, CY-2, a reevaluation of project goals for the quarter had been underway. While a full apex vent equipped flight had originally been envisioned for the weekend of '''June 2''', delays on the project prompted a decision to focus more on quick iterations and numerous launches rather than awaiting longer term initiatives. In particular, it was decided that a legacy ValBal vent mechanism, while unlikely to suffice as a long-term solution, was sufficient and necessary for building altitude control expertise within Cycloon in the short term. Therefore, on '''May 19''', the day after CY-2, it was decided that two payloads would be launched on '''June 1''', alongside Spaceshot and onboarding, each with ballast, vent, and (winds permitting) tether and floater mechanism.

The bulk of the avionics work for the two payloads was completed on May 27, followed by demonstration of vent control on May 29. As winds forecasts for favorable for a float-drop profile, a floater was confirmed for the final configuration. The bulk of the mechanics work occurred on May 29, though due to a lack of spare mechanics the second payload was cancelled. Finally, substantial system integration occurred on May 31. It was hoped that the flight would land safely in the Pacific, enabling controlled daytime hops throughout the following week.

==Configuration==

'''Balloon:''' Kaymont 1500g latex.

'''Mechanics:''' ValBal-style cylindrical polycarbonate sheeting, ValBal ballast and vent mechanism. Parachute in parachute tube. Total payload mass (without ballast, tether or floater) 1.07 kg.

'''Ballast:''' 1.5 kg.

'''Tether and floater:''' 30m paracord tether from balloon to payload and 30m paracord tether from balloon to floater. Total tether mass: 0.34kg. Hydrodynamic floater of mass 0.785 kg.

'''Avionics:''' BMP280, TinyGPS, Teensy 3.2 reporting all data at modifiable intervals via RockBlock modem. Ballast motor controlled by N-type MOSFET. Vent motor controlled by breakout motor driver.

'''Power:''' 18 L91 lithium AA batteries.

'''Mass budget:''' Total mass under balloon 3.695 kg. Total mass 5.195 kg. Target fill to 1.4 kg of tension at top of tether, translating to 275 kg free lift.

==Flight synopsis==

[[File:Ssi87pred.png|400px|thumb|Predicted flight trajectories before launch]]

'''June 1, 2019, 1035 PDT:''' Launch. A fitting between the neck of the balloon and the vent had to be improvised on site. The target ascent rate was 1.7 - 2 m/s, and the flight plan was to equilibrate at 19-22km, with the first vents occurring at 14km.

'''June 1, 2019, 1109 PDT:''' Due to slow ascent of 1.4 - 1.8 m/s, a first ballast command of five seconds was sent. Balloon altitude was around 3.6 km.

'''June 1, 2019, 1143 PDT:''' Further 5 seconds of ballast were sent, titrating successfully at 1.7 - 2.2 m/s at around 7 km in altitude.

'''June 1, 2019, 1236 PDT:''' First vent command of 5 seconds at an altitude of 13.9 km.

'''June 1, 2019, 1259 PDT:''' A communications gap was noted due to issues with HABMC. For the remainder of the flight, monitoring was performed through the RockBlock website.

'''June 1, 2019, 1309 PDT:''' In response to consistent ascent, a total of 25 seconds of vent were sent at an altitude of 17.8 km.

'''June 1, 2019, 1324 PDT:''' With ascent still maintaining around 2 m/s at nearly 20km, a total of 64 seconds of vent was sent.

'''June 1, 2019, 1334 PDT:''' With ascent only barely below 2 m/s and altitude nearing 21 km, 96 seconds of vent were sent.

'''June 1, 2019, 1341 PDT:''' 80 seconds of vent were sent, successfully slowing ascent to around 0.8 m/s at around 21.5 km.

'''June 1, 2019, 1347 PDT:''' 80 more seconds were sent with the intention of stopping ascent entirely. Altitude approaching 22 km.

'''June 1, 2019, 1355 PDT:''' To play it safe, yet 96 more seconds were sent, as the balloon was nearing the danger zone. Following this, a slight descent was observed after a peak altitude of 22.100 km, and equilibration was declared.

'''June 1, 2019, 1409 PDT:''' It was noticed that the GPS coordinates and altitude had frozen at the launch site. The cause for this remains unknown, and hence no detailed trajectory of this flight is available. Simultaneously, the barometer began reporting a negative altitude. This is when the balloon probably popped, after spending only three communication intervals between 22.0 and 22.1 km.

'''June 1, 2019, 1427 PDT:''' Iridium triangulation began reporting consistent coordinates. It is believed that this was payload impact.

'''June 1, 2019, 1435 PDT:''' GPS began reporting coordinates of landing site. It remains unknown why this reset occurred. A recovery team was dispatched to the landing site.
[[File:Ssi87profile.png|thumb|center|600px|Flight profile from launch to loss of telemetry]]
[[File:Ssi87Rates.png|thumb|center|600px|Ascent rate profile from launch to loss of telemetry]]

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

File:Ssi87Rates.png

2019-10-21T10:08:01Z

Bjing:

File:Ssi87profile.png

2019-10-21T10:07:50Z

Bjing:

File:Ssi87pred.png

2019-10-21T10:07:26Z

Bjing:

SSI-87

2019-10-21T10:07:06Z

Bjing:

{{balloon-launch
| header = SSI-87
| img link =
| designations = '''CY-3'''
| launch date =June 1, 2019, 10:35 PDT
| launch site = Le Grand Elementary School, Le Grand, CA
| launch coordinates = 37.226, -120.251
| flight duration = 3h:52m
| flight length = unknown
| flight profile = Ballast and vent control
| landing time =June 1, 2019, 14:27 ODT
| landing site= 13 km SW of Mendota, Fresno County, CA
| landing coordinates = 36.692, -120.518
| last = 86
| next = 90
}}

'''SSI-87''' (project designation '''CY-3''') was the third launch of [[Cycloon|Project Cycloon]] on June 1, 2019. It featured a legacy ballast and vent mechanism from ValBal operated by Cycloon avionics and was the first such fully controlled Cycloon flight. The mission was noted for its eventful manual equilibration, early termination, and for being the last latex Cycloon before the project transitioned to polyethylene. The payload was recovered the afternoon of the launch.

==Project context==

Before and around the time of the previous flight, CY-2, a reevaluation of project goals for the quarter had been underway. While a full apex vent equipped flight had originally been envisioned for the weekend of '''June 2''', delays on the project prompted a decision to focus more on quick iterations and numerous launches rather than awaiting longer term initiatives. In particular, it was decided that a legacy ValBal vent mechanism, while unlikely to suffice as a long-term solution, was sufficient and necessary for building altitude control expertise within Cycloon in the short term. Therefore, on '''May 19''', the day after CY-2, it was decided that two payloads would be launched on '''June 1''', alongside Spaceshot and onboarding, each with ballast, vent, and (winds permitting) tether and floater mechanism.

The bulk of the avionics work for the two payloads was completed on May 27, followed by demonstration of vent control on May 29. As winds forecasts for favorable for a float-drop profile, a floater was confirmed for the final configuration. The bulk of the mechanics work occurred on May 29, though due to a lack of spare mechanics the second payload was cancelled. Finally, substantial system integration occurred on May 31.

==Configuration==

'''Balloon:''' Kaymont 1500g latex.

'''Mechanics:''' ValBal-style cylindrical polycarbonate sheeting, ValBal ballast and vent mechanism. Parachute in parachute tube. Total payload mass (without ballast, tether or floater) 1.07 kg.

'''Ballast:''' 1.5 kg.

'''Tether and floater:''' 30m paracord tether from balloon to payload and 30m paracord tether from balloon to floater. Total tether mass: 0.34kg. Hydrodynamic floater of mass 0.785 kg.

'''Avionics:''' BMP280, TinyGPS, Teensy 3.2 reporting all data at modifiable intervals via RockBlock modem. Ballast motor controlled by N-type MOSFET. Vent motor controlled by breakout motor driver.

'''Power:''' 18 L91 lithium AA batteries.

'''Mass budget:''' Total mass under balloon 3.695 kg. Total mass 5.195 kg. Target fill to 1.4 kg of tension at top of tether, translating to 275 kg free lift.

==Flight synopsis==

[[File:Ssi86profile.png|frameless|800px|center]][[File:Ssi86traj.png|400px|thumb|Mission trajectory]]

'''June 1, 2019, 1035 PDT:''' Launch. A fitting between the neck of the balloon and the vent had to be improvised on site. The target ascent rate was 1.7 - 2 m/s, and the flight plan was to equilibrate at 19-22km, with the first vents occurring at 14km.

'''June 1, 2019, 1109 PDT:''' Due to slow ascent of 1.4 - 1.8 m/s, a first ballast command of five seconds was sent. Balloon altitude was around 3.6 km.

'''June 1, 2019, 1143 PDT:''' Further 5 seconds of ballast were sent, titrating successfully at 1.7 - 2.2 m/s at around 7 km in altitude.

'''June 1, 2019, 1236 PDT:''' First vent command of 5 seconds at an altitude of 13.9 km.

'''June 1, 2019, 1259 PDT:''' A communications gap was noted due to issues with HABMC. For the remainder of the flight, monitoring was performed through the RockBlock website.

'''June 1, 2019, 1309 PDT:''' In response to consistent ascent, a total of 25 seconds of vent were sent at an altitude of 17.8 km.

'''June 1, 2019, 1324 PDT:''' With ascent still maintaining around 2 m/s at nearly 20km, a total of 64 seconds of vent was sent.

'''June 1, 2019, 1334 PDT:''' With ascent only barely below 2 m/s and altitude nearing 21 km, 96 seconds of vent were sent.

'''June 1, 2019, 1341 PDT:''' 80 seconds of vent were sent, successfully slowing ascent to around 0.8 m/s at around 21.5 km.

'''June 1, 2019, 1347 PDT:''' 80 more seconds were sent with the intention of stopping ascent entirely. Altitude approaching 22 km.

'''June 1, 2019, 1355 PDT:''' To play it safe, yet 96 more seconds were sent, as the balloon was nearing the danger zone. Following this, a slight descent was observed after a peak altitude of 22.100 km, and equilibration was declared.

'''June 1, 2019, 1409 PDT:''' It was noticed that the GPS coordinates and altitude had frozen at the launch site. The cause for this remains unknown, and hence no detailed trajectory of this flight is available. Simultaneously, the barometer began reporting a negative altitude. This is when the balloon probably popped, after spending only three communication intervals between 22.0 and 22.1 km.

'''June 1, 2019, 1427 PDT:''' Iridium triangulation began reporting consistent coordinates. It is believed that this was payload impact.

'''June 1, 2019, 1435 PDT:''' GPS began reporting coordinates of landing site. It remains unknown why this reset occurred. A recovery team was dispatched to the landing site.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-91

2019-10-21T09:20:27Z

Bjing:

{{balloon-launch
| header = SSI-91
| img link =
| designations = '''CY-5'''
| launch date =August 5, 2019, 20:11 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.8491, -121.4338
| flight duration =2h:00m
| flight length = 94 km
| flight profile = Standard zero-pressure
| landing time=August 5, 2019, 22:11 PDT
| landing site= 5 km NW of Vernalis, San Joaquin County, CA
| landing coordinates = 37.6634, -121.3217
| last = 90
| next = 92
}}

'''SSI-91''' (project designation '''CY-5''') was the fifth launch of [[Cycloon|Project Cycloon]] on August 5, 2019. It was the second launch of an in-house manufactured polyethylene envelope and the first SSI zero-pressure balloon to report telemetry throughout the flight since [[SSI-20]]. It was also a rare sunset launch, a weekday launch, and featured an even lighter payload than its predecessor, [[SSI-90]]. The payload was recovered on August 31, 2019.

==Project context==

On July 27, 2019 [[SSI-90]] had demonstrated the viability of an in-house manufactured polyethylene envelope for standard-scale payloads. However, due to the mechanisms of that launch, no data on the ascent characteristics, equilibrium altitude, and descent characteristics of a zero-pressure profiles were obtained, thus failing to fulfill one of the major objectives of that flight. Thus, it was immediately decided that a repeat launch would be attempted, with nearly the exact same configurations, except for the addition of a SPOT Trace and strengthening of RockBlock connections. Since a repeat build would require little additional design work, it was decided that the repeat launch would be attempted on the evening of '''August 6, 2019''' from Pigeon Point.

As simulations from Pigeon Point showed the trajectory heading northeast over the Bay Area, it was decided on July 30 to request permission to launch from Garin Regional Park in Hayward, CA instead. That same day, avionics work began and was concluded on August 1. Due to the anticipated short duration of the flight, it was decided to reduce the power bank from 18 to 9 batteries. On July 31, the launch was moved to '''August 5, 2019''', and on August 2 the new launch site was rejected.

The construction of the ZPB and final payload assembly occurred on August 4. It was generally agreed that the quality of the balloon was inferior to that of the first attempt due to several reasons.

==Configuration==

'''Balloon''': 0.3 mil polyethylene, paper bag topology, width 1.8 m, length 7 m, volume approximately 6 cubic meters. Total mass 0.26 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2 transmitting at adjustable intervals over Rockblock. SPOT Trace. Attempts to interface this Teensy with a BMP 280 were universally unsuccessful. This set of avionics was finished from the incomplete second set made for [[SSI-87|CY-3]].

'''Power''': 9 L91 lithium AA batteries. Resistive heater running on single L91 battery.

'''Payload''': Styrofoam enclosure. Mass 0.62 kg.

'''Mass budget''': 0.88 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Inflation was eventful thanks to strong ground winds from due west. The envelope ruptured midway through filling and was patched before refilling. Additionally, a hole approximately 5 mm in diameter was patched.

'''August 5 2011 PDT:''' Balloon released from a running start. Initial motion to the east at an ascent rate of 3.8 m/s --- significantly faster than the target ascent rate of 2.5 m/s.

'''August 5 2059 PDT:''' After almost an hour of steady ascent, balloon reaches a maximum altitude of 10.298 km over (37.1502, -121.4077). Ascent rate had fluctuated above and below the initial rate of 3.8 m/s. In theory, a slight acceleration in ascent was expected. By this time the balloon was in the jet stream layer travelling north at nearly 30 m/s.

'''August 5 2103 PDT:''' Balloon reported an altitude of 10.291 km, a highly unexpected measurement. In retrospect, it is believed that venting began at this altitude, but the vent hole was far too small to vent the necessary volume, leading to envelope rupture. The resulting leakage prevented the balloon from reaching the calculated equilibrium altitude of 14-15km and caused what more resembles a latex profile than a zero-pressure balloon profile.

'''August 5 2055 PDT:''' Balloon reported first definitive descent at an altitude of 9.905 km.

'''August 5 2213 PDT:''' After an hour of descent at 2.5 m/s - 3.0 m/s, balloon reported a ground elevation of 29 km. The landing site was less than 100 m from a road in an apple orchard.

'''August 9 0316 PDT:''' Last RockBlock transmission received, with no indication of movement since flight termination.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

SSI-91

2019-10-21T09:20:10Z

Bjing:

{{balloon-launch
| header = SSI-91
| img link =
| designations = '''CY-5'''
| launch date =August 5, 2019, 20:11 PDT
| launch site = Brigantino Park, Hollister, CA
| launch coordinates = 36.8491, -121.4338
| flight duration =2h:00m
| flight length = 94 km
| flight profile = Standard zero-pressure
| landing time=August 5, 2019, 22:11 PDT
| landing site= 5 km NW of Vernalis, San Joaquin County, CA
| landing coordinates = 37.6634, -121.3217
| last = 90
| next = 92
}}

'''SSI-91''' (project designation '''CY-5''') was the fifth launch of [[Cycloon|Project Cycloon]] on August 5, 2019. It was the second launch of an in-house manufactured polyethylene envelope and the first SSI zero-pressure balloon to report telemetry throughout the flight since [[SSI-20]]. It was also a rare sunset launch, a weekday launch, and featured an even lighter payload than its predecessor, [[SSI-90]]. The payload was recovered on August 31, 2019.

==Project context==

On July 27, 2019 [[SSI-90]] had demonstrated the viability of an in-house manufactured polyethylene envelope for standard-scale payloads. However, due to the mechanisms of that launch, no data on the ascent characteristics, equilibrium altitude, and descent characteristics of a zero-pressure profiles were obtained, thus failing to fulfill one of the major objectives of that flight. Thus, it was immediately decided that a repeat launch would be attempted, with nearly the exact same configurations, except for the addition of a SPOT Trace and strengthening of RockBlock connections. Since a repeat build would require little additional design work, it was decided that the repeat launch would be attempted on the evening of '''August 6, 2019''' from Pigeon Point.

As simulations from Pigeon Point showed the trajectory heading northeast over the Bay Area, it was decided on July 30 to request permission to launch from Garin Regional Park in Hayward, CA instead. That same day, avionics work began and was concluded on August 1. Due to the anticipated short duration of the flight, it was decided to reduce the power bank from 18 to 9 batteries. On July 31, the launch was moved to '''August 5, 2019''', and on August 2 the new launch site was rejected.

The construction of the ZPB and final payload assembly occurred on August 4. It was generally agreed that the quality of the balloon was inferior to that of the first attempt due to several reasons.

==Configuration==

'''Balloon''': 0.3 mil polyethylene, paper bag topology, width 1.8 m, length 7 m, volume approximately 6 cubic meters. Total mass 0.26 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).

'''Avionics''': TinyGPS, Teensy 3.2 transmitting at adjustable intervals over Rockblock. SPOT Trace. Attempts to interface this Teensy with a BMP 280 were universally unsuccessful. This set of avionics was finished from the incomplete second set made for [[CY-3|SSI-87]].

'''Power''': 9 L91 lithium AA batteries. Resistive heater running on single L91 battery.

'''Payload''': Styrofoam enclosure. Mass 0.62 kg.

'''Mass budget''': 0.88 kg total.

==Flight synopsis==

[[File:ssi91traj.png|400px|thumb|Mission trajectory]]
[[File:ssi91launch.png|400px|thumb|left|Balloon ascending after release]]
[[File:Ssi91profile.png|400px|thumb|right|The altitude profile resembled a standard latex launch due to reasons discussed in the synopsis]]

Inflation was eventful thanks to strong ground winds from due west. The envelope ruptured midway through filling and was patched before refilling. Additionally, a hole approximately 5 mm in diameter was patched.

'''August 5 2011 PDT:''' Balloon released from a running start. Initial motion to the east at an ascent rate of 3.8 m/s --- significantly faster than the target ascent rate of 2.5 m/s.

'''August 5 2059 PDT:''' After almost an hour of steady ascent, balloon reaches a maximum altitude of 10.298 km over (37.1502, -121.4077). Ascent rate had fluctuated above and below the initial rate of 3.8 m/s. In theory, a slight acceleration in ascent was expected. By this time the balloon was in the jet stream layer travelling north at nearly 30 m/s.

'''August 5 2103 PDT:''' Balloon reported an altitude of 10.291 km, a highly unexpected measurement. In retrospect, it is believed that venting began at this altitude, but the vent hole was far too small to vent the necessary volume, leading to envelope rupture. The resulting leakage prevented the balloon from reaching the calculated equilibrium altitude of 14-15km and caused what more resembles a latex profile than a zero-pressure balloon profile.

'''August 5 2055 PDT:''' Balloon reported first definitive descent at an altitude of 9.905 km.

'''August 5 2213 PDT:''' After an hour of descent at 2.5 m/s - 3.0 m/s, balloon reported a ground elevation of 29 km. The landing site was less than 100 m from a road in an apple orchard.

'''August 9 0316 PDT:''' Last RockBlock transmission received, with no indication of movement since flight termination.

{{balloon-footer}}

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

Cycloon

2019-10-21T09:12:06Z

Bjing:

[[File:Cycloon.png|400px|thumb|Project components]]
'''Project Cycloon''' ({{slack-channel|balloons-cycloon}}) is a core project on SSI's [[Balloons]] team with the aim of designing and operating altitude-controlled, long-endurance, aero-marine balloon platforms for tropical cyclone research. Begun in January 2019, Cycloon has launched five payloads as of August 2019 and has deployed proof-of-concepts of several novel techniques in high-altitude ballooning, as well as giving rise to [[HABSIM]]. Please contact the current co-leads of Cycloon, {{slack-user|bjing}} and {{slack-user|jtang}}, to get involved!

All flight code, simulations, communications protocols, and flight data/analysis for Cycloon are maintained on [https://github.com/stanford-ssi/cycloon GitHub] and repository notifications arrive in {{slack-channel|balloons-cy-git}}. The flight control channel is {{slack-channel|balloons-cy-flops}}.

==Aims==
Balloons platforms exhibit a very wide range of operating altitudes, making them uniquely well suited to study the [https://en.wikipedia.org/wiki/Tropical_cyclone#Physics_and_energetics secondary circulation and energetics] of tropical systems. Understanding such aspects of tropical cyclones is key to improving forecast models of cyclone intensity, whose reliability has lagged significantly behind that of storm track forecasts. [https://en.wikipedia.org/wiki/Hurricane_Michael Hurricane Michael] is a prime example of a storm where poor intensity forecasts resulted in substantial loss of life and property and was a key inspiration for the project. Additionally, balloons platforms can be deployed at significantly lower cost than planes and buoys, and are therefore significantly more scalable.

Key projects being undertaken within Cycloon (and their respective Slack channels) include:

*'''Altitude control:''' Cycloon aims to master and extend the legacy of altitude control on latex balloons pioneered by previous SSI projects. This entails both mechanical and algorithmic aspects. Design and production of the primary vent and ballast mechanisms is undertaken in {{slack-channel|balloons-cy-platform}}.
*'''Marine tether:''' In order to extend the flight endurance beyond the inherent limitations of latex, Cycloon is developing an tether and floater to rest on the surface of the ocean for days at a time. This architecture was successfully demonstrated in [[SSI-83|CY-1]].
*'''Simulations:''' The need to predict trajectories from California to the Pacific and Atlantic topical basins using the GEFS forecast ensemble has given rise to [[HABSIM]] and its associated work. See also {{slack-channel|balloons-cy-sims}}.
*'''Payload:''' Ultimately, the purpose of the balloon platform will be to carry low-cost, lightweight radiosondes. See {{slack-channel|balloons-cy-payload}}.
*'''Communications:''' To augment data uplink rates, Cycloon is developing a skywave communications system and protocol in {{slack-channel|balloons-cy-comms}}.
*'''Avionics:''' Core avionics work involving circuit board design and flight code is undertaken in {{slack-channel|balloons-cy-avionics}}.
*'''ZPB:''' Polyethylene envelopes have intrinsically more desirable properties compared to latex envelopes. In-house manufacture of such envelopes is being explored in {{slack-channel|balloons-cy-zpb}} and was first demonstrated in [[SSI-90|CY-4]].
==Missions==
{| class="wikitable" style="margin: auto;"
!|Number
!|Link
!|Launch date
!|Launch site
!|Flight duration
!|Notes
|-
|1
! [[File:Ssi83.png|200px|frameless|link=SSI-83]]
| April 17, 2019
| Pigeon Point
| 60 hours, 33 minutes
| Demonstration of long-endurance marine tether. Float-only profile. Lost off the coast of San Luis Obispo county.
|-
|2
! [[File:SSI-86.png|200px|frameless|link=SSI-86]]
| May 18, 2019
| Hollister
| 5 hours, 12 minutes + 5 hours, 40 minutes
| Latex ballast control. Flight through inclement weather and resumption of flight after 24 hours. Final location in Yosemite National Park.
|-
|3
! [[SSI-87]]
| June 1, 2019
| Le Grand
| 3 hours, 52 minutes
| Latex full altitude control. Recovered from near Mendota, California on June 1, 2019.
|-
|4
! [[SSI-90]]
| July 27, 2019
| Hollister
| Unknown
| First flight of in-house constructed polyethylene envelope. Telemetry error; final location unknown.
|-
|5
! [[SSI-91]]
| August 5, 2019
| Hollister
| 2 hours, 0 minutes
| Second flight of in-house constructed polyethylene envelope. Recovered from near Tracy, CA on August 31, 2019.
|-
|6
! [[SSI-92]]
| October 5, 2019
| Hollister
| 9 hours, 28 minutes
| First polyethylene tubing envelope. First SSI ZPB flight with full telemetry. First interstate Cycloon flight. Final location near Alamo, NV.
|}

[[Category: High Altitude Balloons]]

Cycloon

2019-10-21T09:10:43Z

Bjing:

[[File:Cycloon.png|400px|thumb|Project components]]
'''Project Cycloon''' ({{slack-channel|balloons-cycloon}}) is a core project on SSI's [[Balloons]] team with the aim of designing and operating altitude-controlled, long-endurance, aero-marine balloon platforms for tropical cyclone research. Begun in January 2019, Cycloon has launched five payloads as of August 2019 and has deployed proof-of-concepts of several novel techniques in high-altitude ballooning, as well as giving rise to [[HABSIM]]. Please contact the current co-leads of Cycloon, {{slack-user|bjing}} and {{slack-user|jtang}}, to get involved!

All flight code, simulations, communications protocols, and flight data/analysis for Cycloon are maintained on [https://github.com/stanford-ssi/cycloon GitHub] and repository notifications arrive in {{slack-channel|balloons-cy-git}}. The flight control channel is {{slack-channel|balloons-cy-flops}}.

==Aims==
Balloons platforms exhibit a very wide range of operating altitudes, making them uniquely well suited to study the [https://en.wikipedia.org/wiki/Tropical_cyclone#Physics_and_energetics secondary circulation and energetics] of tropical systems. Understanding such aspects of tropical cyclones is key to improving forecast models of cyclone intensity, whose reliability has lagged significantly behind that of storm track forecasts. [https://en.wikipedia.org/wiki/Hurricane_Michael Hurricane Michael] is a prime example of a storm where poor intensity forecasts resulted in substantial loss of life and property and was a key inspiration for the project. Additionally, balloons platforms can be deployed at significantly lower cost than planes and buoys, and are therefore significantly more scalable.

Key projects being undertaken within Cycloon (and their respective Slack channels) include:

*'''Altitude control:''' Cycloon aims to master and extend the legacy of altitude control on latex balloons pioneered by previous SSI projects. This entails both mechanical and algorithmic aspects. Design and production of the primary vent and ballast mechanisms is undertaken in {{slack-channel|balloons-cy-platform}}.
*'''Marine tether:''' In order to extend the flight endurance beyond the inherent limitations of latex, Cycloon is developing an tether and floater to rest on the surface of the ocean for days at a time. This architecture was successfully demonstrated in [[SSI-83|CY-1]].
*'''Simulations:''' The need to predict trajectories from California to the Pacific and Atlantic topical basins using the GEFS forecast ensemble has given rise to [[HABSIM]] and its associated work. See also {{slack-channel|balloons-cy-sims}}.
*'''Payload:''' Ultimately, the purpose of the balloon platform will be to carry low-cost, lightweight radiosondes. See {{slack-channel|balloons-cy-payload}}.
*'''Communications:''' To augment data uplink rates, Cycloon is developing a skywave communications system and protocol in {{slack-channel|balloons-cy-comms}}.
*'''Avionics:''' Core avionics work involving circuit board design and flight code is undertaken in {{slack-channel|balloons-cy-avionics}}.
*'''ZPB:''' Polyethylene envelopes have intrinsically more desirable properties compared to latex envelopes. In-house manufacture of such envelopes is being explored in {{slack-channel|balloons-cy-zpb}} and was first demonstrated in [[SSI-90|CY-4]].
==Missions==
{| class="wikitable" style="margin: auto;"
!|Number
!|Link
!|Launch date
!|Launch site
!|Flight duration
!|Notes
|-
|1
! [[File:Ssi83.png|200px|frameless|link=SSI-83]]
| April 17, 2019
| Pigeon Point
| 60.5 hours
| Demonstration of long-endurance marine tether. Float-only profile. Lost off the coast of San Luis Obispo county.
|-
|2
! [[File:SSI-86.png|200px|frameless|link=SSI-86]]
| May 18, 2019
| Hollister
| 5 hours, 12 minutes + 5 hours, 40 minutes
| Latex ballast control. Flight through inclement weather and resumption of flight after 24 hours. Final location in Yosemite National Park.
|-
|3
! [[SSI-87]]
| June 1, 2019
| Le Grand
|
| Latex full altitude control. Recovered from near Mendota, California on June 1, 2019.
|-
|4
! [[SSI-90]]
| July 27, 2019
| Hollister
| Unknown
| First flight of in-house constructed polyethylene envelope. Telemetry error; final location unknown.
|-
|5
! [[SSI-91]]
| August 5, 2019
| Hollister
| 2 hours
| Second flight of in-house constructed polyethylene envelope. Recovered from near Tracy, CA on August 31, 2019.
|-
|6
! [[SSI-92]]
| October 5, 2019
| Hollister
| 9 hours, 28 minutes
| First polyethylene tubing envelope. First SSI ZPB flight with full telemetry. First interstate Cycloon flight.
|}

[[Category: High Altitude Balloons]]