Changes

| launch site = Brigantino Park, Hollister, CA

| launch site = Brigantino Park, Hollister, CA

| launch coordinates = 36.849, -121.433

| launch coordinates = 36.849, -121.433

| flight duration = 5h:12m (first) <br/>

| flight duration = 5h:12m (first) <br/> 5h:40m (second)

| flight length = 195 km (first) <br/>

| flight length = 195 km (first) <br/> 236 km (second)

| flight profile = Ballast control (first) <br/> Standard latex (second)

| flight profile = Ballast control (first) <br/> Standard latex (second)

| landing time = May 18, 2019, 14:47 PDT (first) <br/> May 19, 2019, 21:10 PDT (second)

| landing time = May 18, 2019, 14:47 PDT (first) <br/> May 19, 2019, 21:10 PDT (second)

| landing site=2.3 km SSW of Clinton, Amador County, CA (first) <br/> Near Bernice Lake, Yosemite NP, CA (second)

| landing site=2.3 km SSW of Clinton, Amador County, CA (first) <br/> Near Bernice Lake, Yosemite NP, CA (second)

| landing coordinates = 38.356, -120.675 (first) <br/> 37.7677, -119.3281(second)

| landing coordinates = 38.356, -120.675 (first) <br/> 37.7677, -119.3281 (second)

| last = 83

| last = 83

| next = 87

| next = 87

}}

}}

'''SSI-86''' (project designation '''CY-2'''; also called ''BalBal'') was the second launch of [[Cycloon|Project Cycloon]] on May 18, 2019. It featured a legacy ballast mechanism from ValBal operated by Cycloon avionics and thus marked the beginning of ''#cy-flops'', or ''Cycloon flight operations''. The mission was noted for its low-altitude profile, interaction with inclement weather, pentagram traced out by RockBlock coordinates, and most remarkably, resumption of flight a full 24 hours after presumed flight termination, the only such occurrence in SSI history.

'''SSI-86''' (project designation '''CY-2'''; also called ''BalBal'') was the second launch of [[Cycloon|Project Cycloon]] on May 18, 2019. It featured a legacy ballast mechanism from ValBal operated by Cycloon avionics and thus marked the beginning of {{slack-channel|cy-flops}}, or ''Cycloon flight operations''. The mission was noted for its low-altitude profile, interaction with inclement weather, pentagram traced out by RockBlock coordinates, and most remarkably, resumption of flight a full 24 hours after presumed flight termination, the only such occurrence in SSI history.

==Pre-Launch==

==Project context==

After the lessons learned of [[SSI-83|CY-1]], a plan for the remainder of the year was decided upon on April 21. First, due to the avionics issues of CY-1, it was envisioned that a marine tether profile launch would be reattempted in early May. Because it was decided that a grounded tether would be a more suitable means of testing endurance, the requirement on launch windows became much less stringent. Then, on May 11, there was to be a HF communications test module as a payload on a ValBal. Finally, on June 4 there would be a fully altitude-controlled flight using the ValBal ballast mechanism, Apex Vent, and Cycloon avionics.

After the lessons learned of [[SSI-83|CY-1]], a plan for the remainder of the year was decided upon on April 21. First, due to the avionics issues of CY-1, it was envisioned that a marine tether profile launch would be reattempted in early May. Because it was decided that a grounded tether would be a more suitable means of testing endurance, the requirement on launch windows became much less stringent. Then, on May 11, there was to be a HF communications test module as a payload on a ValBal. Finally, on June 1 there would be a fully altitude-controlled flight using the ValBal ballast mechanism, Apex Vent, and Cycloon avionics.

Data from CY-1 had demonstrated that the floating coefficient of the system was very low and therefore the aerodynamic drag on the balloon very large; it was suspected that high aerodynamic forces during  winds led to the termination of that mission. Therefore, the first priority was to design a more effective and hydrodynamic floater. This was done by April 25. On April 28, however, the would-be second launch was cancelled due the ValBal controversy, and the would-be first launch was delayed to mid-May. Furthermore, due to continued delays in the HF transceiver parts supply chain and the overall lack of urgency, the communications test was delayed indefinitely. The mid-May launch would instead aim to test the full extent of the system in the absence of a venting mechanism --- that is, marine tether and ballast mechanism --- by starting as a marine tether, dropping ballast, popping, and landing on land, a so-called float-drop-pop profile.

Data from CY-1 had demonstrated that the floating coefficient of the system was very low and therefore the aerodynamic drag on the balloon very large; it was suspected that high aerodynamic forces during  winds led to the termination of that mission. Therefore, the first priority was to design a more effective and hydrodynamic floater. This was done by April 25. On April 28, however, the would-be second launch was cancelled due the ValBal controversy, and the would-be first launch was delayed to mid-May. Furthermore, due to continued delays in the HF transceiver parts supply chain and the overall lack of urgency, the communications test was delayed indefinitely. The mid-May launch would instead aim to test the full extent of the system in the absence of a venting mechanism --- that is, marine tether and ballast mechanism --- by starting as a marine tether, dropping ballast, popping, and landing on land, a so-called float-drop-pop profile.

'''Avionics:''' BMP280, TinyGPS, Teensy 3.2 reporting all data at regular, fixed intervals via RockBlock modem. 2 solar-charged LED modules. Ballast motor controlled by N-type MOSFET.

'''Avionics:''' BMP280, TinyGPS, Teensy 3.2 reporting all data at regular, fixed intervals via RockBlock modem. 2 solar-charged LED modules. Ballast motor controlled by N-type MOSFET.

'''Power:''' 18 L92 lithium AA batteries. In comparison with the standard ValBal complement of 12 L92 batteries, this was thought to be more than sufficient under the most optimistic conditions.

'''Power:''' 18 L91 lithium AA batteries. In comparison with the standard ValBal complement of 12 L92 batteries, this was thought to be more than sufficient under the most optimistic conditions.

'''Mass budget:''' 3.42 kg. Counterweight was designed to balance 3.1 kg of total lift, after which ballast would be removed. In actuality, target fill resulted in nearly perfect buoyancy and no significant ballast was removed.

'''Mass budget:''' 3.42 kg. Counterweight was designed to balance 3.1 kg of total lift, after which ballast would be removed. In actuality, target fill resulted in nearly perfect buoyancy and no significant ballast was removed.

==Flight synopsis==

==Flight synopsis==

[[File:Ssi86traj.png|thumb|Mission trajectory (first segment)]]

[[File:Ssi86traj.png|400px|thumb|Mission trajectory]]

'''May 18 0935 PDT:''' Balloon released after being adjusted to a barely perceptible ascent rate. The mass of some 5m of tether was sufficient to cancel net lift, and an upward thrust was necessary at release time. Initial motion was very slowly to the southeast.

'''May 18 0935 PDT:''' Balloon released after being adjusted to a barely perceptible ascent rate. The mass of some 5m of tether was sufficient to cancel net lift, and an upward thrust was necessary at release time. Initial motion was very slowly to the southeast.

'''May 18 1128 PDT:''' Despite passing over the descending slopes of the Diablo Range, steady ascent continued and even accelerated at one point to over 1.5 m/s.

'''May 18 1128 PDT:''' Despite passing over the descending slopes of the Diablo Range, steady ascent continued and even accelerated at one point to over 1.5 m/s.

'''May 18 1143 PDT:''' After slowing ascent, balloon reached maximum altitude at 4430m over (37.3780, -121.0420). Balloon then began to descend. While it was not clear at the time why ascent stopped, it is apparent in retrospect that the trajectory had entered areas of inclement weather, and downdrafts and/or rain were pushing the balloon downward.

'''May 18 1143 PDT:''' After slowing ascent, balloon reached maximum altitude at 4430m over (37.3780, -121.0420). Balloon then began to descend. While it was not clear at the time why ascent stopped, it is apparent in retrospect that the trajectory had entered areas of inclement weather, and downdrafts and/or rain were pushing/weighing the balloon downward.

'''May 18 1153 PDT:''' Descent rate accelerated to an alarming 2.0 m/s over (37.462, -120.970). Although it was believed that the equilibrium ascent rate was already too high, ballasting was seriously considered in light of this rapid descent.

'''May 18 1153 PDT:''' Descent rate accelerated to an alarming 2.0 m/s over (37.462, -120.970), prompting immediate ballasting.

'''May 18 1220 PDT:''' After two ballast events, the trajectory leveled off over (37.713, -120.908), reaching a minimum altitude of 1220 m, and then resumed ascent just above 0.5 m/s. This was viewed as having effectively delayed launch by 2 hours and therefore a net benefit for mission endurance.

'''May 18 1220 PDT:''' After two ballast events, the trajectory leveled off over (37.713, -120.908), reaching a minimum altitude of 1220 m, and then resumed ascent just above 0.5 m/s. This was viewed as having effectively delayed launch by 2 hours and therefore a net benefit for mission endurance.

'''May 18 1331 PDT:''' Balloon equilibrates at 3431m, a second altitude maximum, over (38.082, -120.868).

'''May 18 1331 PDT:''' Balloon equilibrated at 3431m, a second altitude maximum, over (38.082, -120.868).

'''May 18 1341 PDT:''' Balloon descends at over 2 m/s less than 2km above the ground, again likely due to downdrafts and/or rain, prompting a series of frantic ballast events. Due to the low altitude and rising ground elevation, the trajectory was within two communications intervals of flight termination. All hopes of a long-endurance flight had been abandoned; survival was the only priority.

'''May 18 1341 PDT:''' Balloon descended at over 2 m/s less than 2km above the ground, again likely due to downdrafts and/or rain, prompting a series of frantic ballast events. Due to the low altitude and rising ground elevation, the trajectory was within two communications intervals of flight termination. All hopes of a long-endurance flight had been abandoned; survival was the only priority.

'''May 18 1416 PDT:''' Descent slows and balloon reaches a minimum altitude of 351m, less than 80m above the ground elevation of 285m at (38.277, -120.799) (due to hilly terrain, it is possible the balloon was even closer to the ground and maybe even made contact). Nevertheless, the trajectory was recovered and ascent resumed.

'''May 18 1416 PDT:''' Descent slowed and balloon reached a minimum altitude of 351m, less than 80m above the ground elevation of 285m at (38.277, -120.799) just east of Pardee Reservoir in Calaveras County (due to hilly terrain, it is possible the balloon was even closer to the ground and maybe even made contact). Nevertheless, the trajectory was recovered and ascent resumed. A ballast command was sent to make sure ascent was steady enough to clear the rising Sierra Nevada foothills.

'''May 18 1446 PDT:''' After several consecutive intervals of ascent, sudden descent was observed at a rapid enough speed to terminate flight by the next communication. A ballast interval was sent --- too little, too late in retrospect.

'''May 18 1446 PDT:''' After several consecutive intervals of ascent, sudden descent was observed at a rapid enough speed to terminate flight by the next communication. A ballast interval was sent --- too little, too late in retrospect.

'''May 18 1451 PDT:''' Balloon reported its final resting coordinates and elevation. After the next communication, flight termination was confirmed.

'''May 18 1451 PDT:''' Balloon reported its final resting coordinates and elevation. After the next communication, flight termination was confirmed.

'''May 19 1608 PDT:''' Communications ceased, presumably due to rain. By now it had become clear that at least the last two hours of the flight had been in the midst of inclement weather.

'''May 18 1608 PDT:''' Communications ceased, presumably due to rain. By now it had become clear that at least the last two hours of the flight had been in the midst of inclement weather.

 

 

 

 

'''May 20 1952 PDT:''' Last RockBlock message received. It was not until the evening of May 23 that efforts were made to contact local individuals for recovery and the second flight was discovered.

[[File:Ssi86profile.png|frameless|800px|center]]

[[File:Ssi86profile.png|frameless|800px|center]]