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 positive lift of 1200g. Using an online calculator, we were able to determine the amount of helium required (1 cu.ft. of helium will lift 28 grams).

The result of the lower than projected positive lift and ascension rate had both a negative and positive impact. On a positive note, our payload exceeded our initial target of 100,000 ft. In fact, our vessel reached a maximum altitude of 109, 678 ft (33, 430 m), nearly 10% higher than expected. The negative affect caused a 132 minute longer mission than anticipated and approximately 30 km greater recovery distance. Furthermore, due to the longer overall flight time, the camera batteries were drained and rendered all cameras inoperable.

Initial flight path and recovery distance is based upon ascension rate, wind speed, and burst altitude (www.predict.habhub.org). For our Raider I launch, conditions were ideal having negligible wind speed and placed our vessel landing approximately 20 km away from launch site. Total time for the launch was estimated at 142 minutes (100 m ascent time + 42 minute descent time). Instead, we traveled 50 km and had to wait a total of 274 minutes (4h 34m).

Overall, we were quite disappointed about the extended flight time as many of the projected video and pictures were never obtained. Specifically, we hoped to have acquired our “money shot” which was to have our Raider logo in the forefront of the earth’s curvature which can be seen at 100,000 ft. Additionally, we hoped to capture the video of the balloon bursting. Both of these video opportunities will be available once again in our next launch (Raider II).