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'''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.

'''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), prompting immediate ballasting.

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

'''May 18 1953 PDT:''' Communications resumed, with GPS and barometer reading nonsensical values. From this point forward, RockBlock coordinates were the only available information.

'''May 18 1953 PDT:''' Communications resumed, with GPS and barometer reading nonsensical values. From this point forward, RockBlock coordinates were the only available information.

'''May 19 1530 PDT:''' Unbeknownst to anyone at the time, balloon resumed flight.

'''May 19 1530 PDT:''' Unbeknownst to anyone at the time, balloon resumed flight after over 24 hours on the ground, presumably due to solar heating and drying.

'''May 19 2110 PDT:''' Balloon appeared to land in Yosemite NP, in the vicinity of Vogelsang Peak and Bernice Lake, well above the tree and snow line. Due to noisy RockBlock coordinates, it is impossible to ascertain a precise location, nor to rule out further movement down the slopes overnight.

'''May 19 2110 PDT:''' Balloon appeared to land in Yosemite NP, in the vicinity of Vogelsang Peak and Bernice Lake, well above the tree and snow line. Due to noisy RockBlock coordinates, it is impossible to ascertain a precise location, nor to rule out further movement down the slopes overnight. It is also unknown if the balloon popped or experienced a thermal descent at sunset.

'''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.

'''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.