SSI-92

SSI-82
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 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
←SSI-91 SSI Balloon Launches SSI-93→

SSI-92 (project designation CY-6) was the sixth launch of 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 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

Mission trajectory

Balloon ascending after release

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.