Monday, August 27, 2012
The quest for pyro free parachute deployment
Pyro free deployment is, in my opinion, one of the 'holy grails' of sport rocketry. The 'pyro' rocketry folks (of which I am one) have had some success with compressed gas and mechanical approaches. However, they tend to me heavy and relatively complicated (when compared to an altimeter and some powder). These also don't scale well to the LPR spectrum.
The water rocket folks have had better success mainly using small mechanical timers. Some of the big dogs of the hydro crowd have even built electro-mechanical timers. For instance, the good folks at Air Command have a really cool servo timer. TRF user closet astronaut is applying one to a flying Mercury Redstone capsule (thread). A video of what he's currently working on is at the bottom of this post.
The reason I'm pondering this issue (again) is that I'd like to deploy a parachute from an an air powered rocket. These rockets have less lift capability than water rockets and much less than modrocs. They are also inherently light so there aren't many hardpoints where mechanisms can be attached. Mike Bauer is working on a 'Tomy' timer mechanism (1:12 Mercury Redstone Air Launch Rocket) and reader Artemi has provided a link to his work (Sky Dart Air Rocketry). Artemi also is working with backsliding, where the CP/CG is such that the rocket will glide backwards. This would work for long skinny air rockets too. I have noticed that my big air powered HoJo would start to backslide. It would then fall parallel to the ground before transitioning to lawn dart recovery. On my next big build, I think I'll check the CG and CP and consider adjusting the CG.