A long time ago, I set off to work on a rocket worthy of attempting a Level 3 High Power Rocketry certification. In an effort to document this project, I’ve been posting pictures and haphazard build logs for various subsystems of this rocket. However, some things have not merited entire posts, but are still critical to the function of flight. This is their place. (Note: I still have a couple more full-length posts to go regarding electronics and avionics bays, full vehicle integration, and flight operations. These will be available soon!)
Performance was a major driver in the early stages of design of this rocket, as was my anticipated cost. While high flight was not ideal, altitude was not a strong design constraint (though, nominally, it was to fly under 24,000 ft based on the waiver of my old field near Talladega, AL). I’ve had past trouble with supersonic rockets, so I felt pretty strongly about keeping the nominal design below Mach 0.90–the lower the better. I also imposed a 75mm motor size requirement since I had obtained a CTI 75mm motor case set. I would also insist on redundant electronics and a sufficiently simple design (which may or may not have been realized). I designed for a static stability margin between 1.0 and 2.0 calibers (leaning towards 2.0), a minimum ground acceleration of 6.0 G, and a minimum velocity off an 8-foot rail of 50 ft/s. Here’s some of the projected characteristics:
- Length: 120 in
- Diameter: 5.5 in
- Fin span: 15 in
- Weight (liftoff): 34.8 lb
- Static stability margin: 1.98
- Max acceleration: 11.7 G
- Max velocity: 963 ft/s
- Max altitude: 11,680 ft
- Max Mach number: 0.87
- Velocity off 8-ft rail: 73.2 ft/s
- Time to apogee: 25.5 s
- Time of flight: 229 s
While recovery systems are extremely important, it is difficult to dedicate an entire post to the basic recovery hardware. This rocket will implement a fairly standard redundant dual deploy system. A 30-inch Top Flight Recovery flat sheet parachute will deploy as a drogue at apogee. It will be tethered to the rocket by 50+ feet of 9/16″ tubular nylon webbing. At 600 feet AGL, the altimeters will deploy a 96-inch Top Flight Recovery Crossfire parachute. This main parachute will be tethered by 30+ feet of 9/16″ tubular webbing. This should allow the rocket to touch down at a little over 18 ft/s. Parachutes will be tied into 1/4-20 quick links. Parachutes will be protected from hot ejection gases by a combination of Nomex cloth and dog barf insulation.
I have obtained an Eggfinder GPS tracker unit to install in the nose cone to perform post-flight rocket location.