Calculations

FLIGHT CALCULATIONS

Flight calculations are required prior to any launch. The two driving concerns which will dictate further calculations include both the burst height and the acceptable recovery distance. For most near space missions, a desired altitude would be approximately 100,000ft or 30,000m. Our team did not want to drive longer than 1-hour to retrieve the payload, thus we chose early June for the launch as late Spring or Summer typically have the lowest wind speeds and is a desired time for a launch.

To achieve the desired burst altitude, our team would need to obtain the correct sized balloon and apply the correct amount of helium. A considerable amount of helium would create a strong higher positive lift and faster ascent rate. Although this sounds good, as there is less lateral movement (wind) due to the faster ascension rate, it is likely that the balloon will burst at a lower altitude due to the increased volume of helium.

A recommended ascension rate of five meters per second is recommended for HAB flights. At an ascension rate of 5 m/s, the payload can attain its desire burst altitude in a relatively short amount of time, but also in a safe manner (turbulence). A slower ascension rate will likely result with a higher burst altitude, but considerably more recovery distance will be required.

To meet our desired ascension rate of 5 m/s, we required a buoyancy of 3437 g. Using an online calculator, we were able to determine the amount of helium required 4,940 liters or 275 bar (20 l tank).

Initial flight path and recovery distance is based upon ascension rate, wind speed, and burst altitude (www.predict.habhub.org). For our Raider II launch, conditions were fair having acceptable wind speed of approximately 9 mph and placed our vessel landing approximately 90 km away from launch site. Total time for the launch was estimated at 156 minutes (116 minutes ascension / 40 minute descent).