Sport Rocketry

SPORT ROCKETRY MAY/JUNE 2017 29 feet per second and utilized an Iris Ultra 84" Compact Parachute. The payload bay doors would free-fall. The lander however would require a much gentler rate of de- scent. For a safe/gentle landing I calculat- ed I needed a descent rate of around 3-5 fps. To achieve that rate, I worked closely with Gene Engelgau at Fruity Chutes to determine the proper recovery chute siz- ing. Considering the 3-5 fps requirement and lander launch weight of 2241grams, we determined an Iris Ultra 120" Compact Parachute should perform adequately (see Figures 16 and 17). Now I know what you're thinking (should be thinking): 3-5 fps recovery descent rate deployed at 2000 feet would present a serious horizontal drift issue! Considering the chute diameter being a substantial 120" and the launch weight of the lander being a modest 2241 grams, I was pushing the limitations of physics: The lander mass was considered marginally enough to open this sized recovery chute and therefore this event would require ad- ditional time to achieve full deployment. Since this isn't a typical configuration, there isn't any historical data to pull from. This is where some educated guesswork came into play and I estimated it would take about 1000 to 750 feet from apogee for the lander recovery chutes to fully de- ploy. The calculations I used for estimating lander drift (also assuming 5 fps horizon- tal drift) are shown above: Communications The project ultimately required the ability to remote control the rover with a live POV (from the lander) video feed. The live video feed was crucial, since this would be my only way to guide the rov- er visually. I quickly determined that a smartphone was the perfect solution for this challenge as it is readily program- mable, has cellular data comm, and Blue- tooth comm. As described earlier the rover "pairs" with the smartphone via Bluetooth. Relay unit connections. Lander Descent Calculations (two scenarios): Free Fall Phase 1000 ft 750 ft Mass 5 g 5 g Air Resistance k 0.24 kg/m 0.24 kg/m Gravity 9.807 m/s 2 9.807 m/s 2 Free fall time 32.5 seconds 24.5 seconds Free fall velocity 31.4 fps 31.4 fps 21.4 mph 21.4 mph Controlled Descent Phase 1000 ft 1250 ft Rate 4 fps 4 fps Duration (S) 250 seconds 312 seconds Duration (M) 4.2 minutes 5.2 minutes Horizontal Drift v estimate 5 fps 5 fps Horizontal Drift d estimate 1250 ft 1560 ft

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