Pegasus II – Balloon Parameters

A few calculations made on the flight of Pegasus II.  We target an ascent rate of 5 m/s, then work out the remaining calculations.  It is always a trade off between max altitude, mass of payload, ascent rate, and balloon size.  We must be careful to avoid a floater (neutral buoyancy) and ensuring the tethering is has enough tension, i.e., > 500 grams of residual lift.  We don’t measure the volume of Helium, rather the Neck Lift as the balloon fills.

Balloon Size 2000 grams
Mass of Payload 3950 grams (8 lbf, 11 oz)
Target Altitude 30480 meters
Launch Altitude 192 meters
Burst Diameter 10.67 meters (35 ft)
Target Ascent Rate 5 meters/sec
Helium Volume 7.4 cubic meters, 260 cubic feet
Launch Diameter 2.4178 meters (7.93 ft)
Free Lift 7745 grams
Neck Lift 5745 grams
Residual Lift 1795 grams
Burst Altitude 32233 meters

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