Slashdot Mirror
Ask 'Rocket Guy' Brian Walker
We've mentioned amateur rocket enthusiast Brian Walker (better known as Rocket Guy) a few times before; he's one of those people who aren't content with building Estes model rockets that carry eggs or tiny cameras. Instead, Rocket Guy is building a backyard rocket -- and he hopes to launch himself about 35 miles into the air. His launch, originally planned to take place sometime this year, has been delayed for the best of reasons, but now's your chance to ask about the theory and practice of home-brewed rocket travel. We'll pass the best questions along to Rocket Guy, and post his answers soon.
AFAIK (we met at Space Access this year), Brian is not interested in advanced engine work. For his goals, simple monoprop peroxide is far and away the most direct route.
For reference, while the theoretical Isp is usually listed around 155, we typically only see 115 or so at sea level with less than 300 psi chamber pressure.
> hybrid (ie, plastic/nitrous oxide) propellants?
Peroxide makes a pretty good hybrid oxidizer, with better Isp and density-Isp than nitrous based hybrids, plus it auto-ignites after decomposition. Vec Isp may be as high as 275 with 90% peroxide, but sea level will be down around 200-225, depending on chamber pressures. We fired a couple peroxide / polyethylene hybrid grains last year, but we haven't pursued it much.
There is a very tantalizing possibility of using aluminum hydride as a hybrid graid with peroxide, giving a theoretical vacuum Isp of over 400 (!!!), and it is non-toxic. We are probably going to look into this one of these days.
> buckyballs
Not much use. Buckytube composites may make for very mass efficient tanks and structures in the not too distant future.
> multi-atomic nitrogen
If it can ever be produced affordably, a 600 Isp monoprop would sure be nice. Easy to go boom, though.
> fluorine
Ick. Very toxic, very corrosive. Flourine / lithium hybrids can get over 500 Isp, but it would be very dangerous.
I feel that the best way to take advantage of exotic developments is to build a fully functional vehicle with conventional materials, so if a wonder material / propellent does materialize, you are well poised to take advantage of it.
John Carmack