Changes

==Project context==

==Project context==

The same day that [[SSI-87|CY-3]] failed to reach the Pacific Ocean due to an unexpected flight termination at relatively low altitudes, [[Spaceshot|Spaceshot's]] [[SSI-88]], flying a Raven 50k cubic foot polyethylene ZPB, experienced ''increased'' flight endurance thanks to equipment failure, surviving into the Pacific Ocean and floating on its surface for two days despite a conscious objective to avoid doing so. It was remarked by many that Spaceshot had achieved Cycloon's mission profile more successfully than Cycloon. This was almost entirely attributable to the characteristics of Spaceshot's polyethylene envelope --- unlike a latex envelope, it was capable of passive venting and equilibration, was impossible to pop, and was significantly more water-resistant. Upon reflection, it became clear that the only reason Cycloon had defaulted to latex was that no low-cost polyethylene envelopes could be purchased at a size suitable for Cycloon-type missions. However, thanks to the obvious low cost of the raw materials and relative simplicity of manufacture, an initiative was launched to look into manufacturing polyethylene in house. As an additional benefit, active venting would be highly simplified in a zero-pressure envelope, as an apex vent could be mechanically identical to a latex bottom vent.

The same day that [[SSI-87|CY-3]] failed to reach the Pacific Ocean due to an unexpected flight termination at relatively low altitudes, [[Spaceshot|Spaceshot's]] [[SSI-89]], flying a Raven 54k cubic foot polyethylene ZPB, experienced ''increased'' flight endurance thanks to equipment failure, surviving into the Pacific Ocean and floating on its surface for two days despite a conscious objective to avoid doing so. It was remarked by many that Spaceshot had achieved Cycloon's mission profile more successfully than Cycloon. This was almost entirely attributable to the characteristics of Spaceshot's polyethylene envelope --- unlike a latex envelope, it was capable of passive venting and equilibration, was impossible to pop, and was significantly more water-resistant. Upon reflection, it became clear that the only reason Cycloon had defaulted to latex was that no low-cost polyethylene envelopes could be purchased at a size suitable for Cycloon-type missions. However, thanks to the obvious low cost of the raw materials and relative simplicity of manufacture, an initiative was launched to look into manufacturing polyethylene in house. As an additional benefit, active venting would be highly simplified in a zero-pressure envelope, as an apex vent could be mechanically identical to a latex bottom vent.

On June 6, 2019, summer goals were formally codified. It was determined that writing an altitude control algorithm, improving simulations, manufacture of a platform PCB, manufacturing polyethylene envelopes, and mass producing ballast and vent mechanisms were the top priorities. After a summer recess, work began in earnest following a meeting on July 9. A launch schedule was set, featuring a test launch of an in-house manufactured ZPB on '''July 21, 2019''', and an altitude-controlled ZPB on '''August 18, 2019''', with other goals and deadlines left unspecified.

On June 6, 2019, summer goals were formally codified. It was determined that writing an altitude control algorithm, improving simulations, manufacture of a platform PCB, manufacturing polyethylene envelopes, and mass producing ballast and vent mechanisms were the top priorities. After a summer recess, work began in earnest following a meeting on July 9. A launch schedule was set, featuring a test launch of an in-house manufactured ZPB on '''July 21, 2019''', and an altitude-controlled ZPB on '''August 18, 2019''', with other goals and deadlines left unspecified.

'''July 27, 2019, 1246 PDT''': Balloon release with an estimate ascent rate of 2.5 m/s. Due to ground winds being stronger than expected, the orientation of the balloon was nearly sideways at the moment of release, and the payload suffered a hard impact with the ground and was dragged by the balloon for approximately one second before lifting off. In post-analysis, it was determined that this impact likely loosened connections already made vulnerable by the impact at the end of CY-3, in particular the connections to the RockBlock. No transmissions were received after launch.

'''July 27, 2019, 1246 PDT''': Balloon release with an estimate ascent rate of 2.5 m/s. Due to ground winds being stronger than expected, the orientation of the balloon was nearly sideways at the moment of release, and the payload suffered a hard impact with the ground and was dragged by the balloon for approximately one second before lifting off. In post-analysis, it was determined that this impact likely loosened connections already made vulnerable by the impact at the end of CY-3, in particular the connections to the RockBlock. No transmissions were received after launch.

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[[Category: High Altitude Balloons]][[Category: Balloon Launches]]

[[Category: High Altitude Balloons]][[Category: Balloon Launches]]