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Designations CY-8
Launch date November 17, 2019
Launch site Pigeon Point Light Station, Pescadero, CA
Launch coordinates 37.1827, -122.3923
Flight profile Ground tests
←SSI-93 SSI Balloon Launches

SSI-97 (project designation CY-8) was the seventh launch of 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.


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 Launches
2014-15 SSI-19202122
2015-16 SSI-23(a) • 2425262728293031323334353637383940414243
2016-17 444546474849505152
2018-19 8386879091
2019-20 929397