|Launch date||October 26, 2019, 10:14 PDT|
|Launch site||Brigantino Park, Hollister, CA|
|Launch coordinates||36.849, -121.433|
|Flight length||202 km|
|Flight profile||Folded zero pressure w/ ballast control|
|Landing time||October 27, 2019, 14:18 PDT|
|Landing site||9 km SW of Tulare, Tulare County, CA|
|Landing coordinates||36.164, -119.431|
SSI-93 (project designation CY-7) was the seventh launch of Project Cycloon on October 26, 2019. It was the zero pressure balloon equipped with altitude control (ballast mechanism), and launched alongside two other zero-pressure balloons at Onboarding. It was the first balloon in the folded topology as a result of a notably eventful filling, and consequently also experienced a noteable post-landing.
The launch plan at the beginning of the quarter had called for a fully controlled ZPB flight coincident with onboarding on October 26, 2019. However, the unavailability of a vent mechanism and the surprising endurance of SSI-92 motivated the decision to do a long-endurance ballast-controlled ZPB instead. The analysis of data from that previous flight had suggested a thermal difference of 10% during the day; given this, it seemed possible to aim for a multi-day flight with a reasonable amount of ballast. Briefly, on October 18, a floater was considered as the forecast appeared to show winds going towards the ocean, but this was temporary. The primary upgrades, in addition to the vent mechanism, was a heating mechanism and a GPS reset mechanism, lessons learned from the last flight.
Construction of the payload was a streamlined process by this time. Avionics were produced in an October 15 worksession; on October 18 a large number of balloons were manufactured for Onboarding; and on October 20, the payload was integrated, marking launch readiness a week ahead of time. The integration of the payload was tricky, as no top piece was suitable for the legacy ballast piece, and furthermore thermal insulation was a concern.
Balloon: 0.8 mil polyethylene tubing, folded topology, width 2.5 m, length 10 m, volume unknown. Total mass 1 kg with fill tube (PVC of length approximately 12 inches and diameter 1/2 inch).
Avionics: TinyGPS, Teensy 3.2, BMP 280 transmitting at adjustable intervals over Rockblock. SPOT Trace. Ballast control; nichrome cutdown; GPS power reset MOSFET.
Power: 12 L91 lithium AA batteries. 3 L91 lithium AA batteries on resistive heater and cutdown.
Ballast: Legacy valbal mechanism with 500 g ballast, theoretically enough for two nightfalls.
Payload: Half valbal-style polycarbonate cylinder within styrofoam enclosure. Mass 1.25 kg including ballast.
Mass budget: 2.26 kg total.
October 26 953 PDT: Balloon released after an attempted titration to 0.5 kg of free lift. Moderate winds made this difficult. However, within a few dozen seconds of release the balloon began to descend, and was caught barely within the southwestern boundaries of Brigantino park. A large leak at the top seal was discovered, motivating the decision to fold the envelope over. The balloon was re-filled and observed for 10 minutes for second release.
October 26 1014 PDT: Balloon released at approximate 1.5 m/s ascent with initial motion to the southwest.
|2014-15||SSI-19 • 20 • 21 • 22|
|2015-16||SSI-23(a) • 24 • 25 • 26 • 27 • 28 • 29 • 30 • 31 • 32 • 33 • 34 • 35 • 36 • 37 • 38 • 39 • 40 • 41 • 42 • 43|
|2016-17||44 • 45 • 46 • 47 • 48 • 49 • 50 • 51 • 52|
|2018-19||83 • 86 • 87 • 90 • 91|
|2019-20||92 • 93 • 97|