Changes

== Payload Specifications ==

== Payload Specifications ==

[[File:ssi191.jpg | thumb | <center> SSI-19 Payload </center>]]

[[File:ssi191.jpg | left | thumb | <center> SSI-19 Payload </center>]]

The SSI-19 payload was, as needed, a very barebones set of electronics. It included an APRS BigRedBee transmitter using the callsign of balloons team member Iskender Kushan (KK6MIR), a GPS for position reporting, a sizable lithium-ion battery, and a heater made of nickel-chromium (nichrome) wire. In total, the payload had a mass of about 365g. It was the first balloon to be launched during the launch of SSI-19, SSI-20, and SSI-21. CNSP graciously brought their mass-flow meter to fill the SSI-19 latex balloon to a precise lift capacity (a mission-critical aspect of this launch).

The SSI-19 payload was, as needed, a very barebones set of electronics. It included an APRS BigRedBee transmitter using the callsign of balloons team member Iskender Kushan (KK6MIR), a GPS for position reporting, a sizable lithium-ion battery, and a heater made of nickel-chromium (nichrome) wire. In total, the payload had a mass of about 365g. It was the first balloon to be launched during the launch of SSI-19, SSI-20, and SSI-21. CNSP graciously brought their mass-flow meter to fill the SSI-19 latex balloon to a precise lift capacity (a mission-critical aspect of this launch).

== The Flight ==

== The Flight ==

[[File:ssi_22_storm.png | thumb | <center> The storm </center>]]

As expected, the balloon had a fairly slow ascent velocity due to its low free lift. It ascended at an average velocity of around 1.5 m/s, initially with a southbound heading until hitting north-bound winds 10 minutes into flight. Following ascent to approximately 10,000 feet at 7:07 PM PDT, SSI-19 had a East-Northeast heading for the majority of its flight. It reached critical altitude at around 8:00 AM PDT on May 17th, just south of Mono Lake in the Yosemite National Park. As the sun rose, the balloon began being degraded by UV radiation.

The fast ascent rate of the balloon proved to be an immediate test of the resilience and fidelity of the autonomous altitude control algorithm. As soon as the balloon was launched, the team began to pack up while waiting for the first message from the payload. The first message confirmed that the payload was slowly being incentivized to vent gas and slow its ascent. By the time the team had packed up and started driving out, the payload had vented gas a total of 7 times, decreasing its ascent rate to < 1.5 m/s. The algorithm was pre-programmed to maintain an altitude between 12km and 14km, as this range of altitudes was chosen to optimize the wind conditions the balloon would experience (fastest winds, most predictable, and most appropriate direction). After the balloon roughly levelled off, the team armed the ballast mechanism over satellite comms. The GPS lock was lost at exactly 12:00 am PDT (due to a snippet of code in the GPS library relying on date, and being unable to cope with the month turnover of May to June). Nonetheless, the satellite communications module transmitted GPS coordinates (albeit with a subpar ~ 4km accuracy).

The balloon reached a peak altitude of 119,932 ft at 9:15 AM PDT, May 17th, breaking the former SSI altitude records for latex balloons. It burst shortly after this position report, indicating a descent of nearly 1,000 feet. Unequipped with a parachute, SSI-19 descended from altitude in a matter of approximately 30 minutes. It landed just east of Grant Lake, a few hundred feet off the California 395.

The payload flew at considerable speed, crossing into Nevada after two hours in the appropriate altitude range. The flight continued through Nevada northward, cutting through the southeastern corner of Oregon before entering Idaho around 2:20 am PDT. The payload spent considerable time in central Idaho, and transmitted data suggesting considerable venting and ballast dropping occurring in this area. Unbeknownst to the team until the balloon was out of Idaho airspace, the balloon flew through a class 3 thunderstorm, experiencing considerable turbulence. Despite the tremendous up and downdrafts, the balloon was able to autonomously maintain its altitude within its defined range, at the cost of considerable gas and ballast.

[[File:ssi19rec.jpg | thumb | <center> SSI-19 at the Recovery Site </center>]]

After spending a few hours in the thunderstorm, the balloon entered Montana at around 8:00 am PDT, continuing on a north/northeast trajectory. At 2:39 pm PDT, and at over 1,000 miles from the launch site, the balloon entered Canadian airspace in Saskatchewan province. At this point the balloon began a more prominently eastward flight path along the Canadian border. At around 6:36 PDT, the balloon began a steady descent just north of the North Dakota/Montana border. Based on data transmitted from the balloon, it was clear that the system had ran out of ballast material and was thus unable to drop weight to compensate for lost lift as night was arriving and hence began to fall. The ballooon fell slowly for about an hour, finally terminating its flight at around 8:35 pm EDT, landing in a field.

[[File:ssi19aprs.PNG|center|800px|frame|<center> SSI-19 Flight Path </center>]]

== Debriefing ==

== Debriefing ==

The ability of the balloon to maintain altitude on its own through almost the entire flight to such precision was a testament to the resilience of the technology. Nevertheless, problems were encountered, including the following:

The ability to use natural passive feedback to equilibrate at a given altitude was spectacular to observe. Nonetheless, issues existed.

*The power draw for heating was quite high; the battery started at a voltage of ~ 4.34 V and was around ~ 3.40 V upon landing. 3.20 V is the point at which the flight control system ceases to function; thus, for longer flights, more power is needed. Proposed improvements included more battery storage and, more importantly, solar panels for power regeneration.  

* In order to utilize this feedback mechanism, the balloon must be at a sufficiently high altitude. Achieving this altitude requires a large balloon with very little gas (in order to not burst prematurely). This requires a very lightweight payload, which means very little can be carried onboard.

*This flight offered an indication of how far the preloaded quantity of ballast was able to take the balloon. Granted, the turbulence experienced over Idaho resulted in considerable usage of ballast, but the fact that this occurred suggested that significantly more ballast would be required for longer journeys.

* UV radiation is very strong at this high altitude (being above the Ozone layer), causing the latex to break down very quickly. Additionally, latex quality varies drastically from balloon to balloon, making launches fairly unpredictable.  

 

*Gas venting can also be amended; a 3-inch neck was used to allow for high volumes of gas to be vented, but this could have been reduced to a neck diameter as small as 1 inch and compensated for with a larger vent time. Venting for 5 seconds at a time with a 3 inch neck caused unnecessarily large volumes of gas to be vented.

 

*Better payload insulation is needed. [[SSI-18]] used a payload wrapped in AeroGel Cryogel blanket, which was so insulative that its heaters did not need to turn on for over 10 hours. A shrinking budget and smaller timeframe did not permit the team to put Aerogel on this flight, but its potential value to future payload containers was demonstrated.

== Milestones ==

== Milestones ==

* Longest flight of SSI Balloons (as of May 2015)

* Longest flight of SSI Balloons (as of September 2015)

* Highest altitude reached of SSI Balloons (as of May 2015)

* Longest ground distance traveled by any SSI Balloons mission (as of September 2015)

 

 

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

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