Hello all.
An interesting bit that I've been rolling around... If one believes the numbers that the simulator spits out, One could launch Micro-payloads (< 5 lb) on a Balloon staged mostly off-the-shelf M engine powered model rocket. (Don't expect a lot of input from me on this, It'll be a while before I qualify to buy M's..)
-Ejay
To 100km, yes. To orbit, no. Even ignoring the guidance and control issue, the mass fraction of even the biggest sport rocketry motors don't get much over 2, even without a rocket around them. The Isp isn't very high -- around 220 or so, so you need a mass ratio of about 60 to get to orbit. With stage mass ratios under 2, that means at least six stages, with the bottom stage having 64 motors.
Hotter propellant with much lighter casings and vacuum optimized nozzles can reasonably get a two stage solid to orbit from a balloon -- Isp around 280, mass ratio around 9. It is possible to get a two stage solid to orbit from a ground launch, but the required burn times to minimize drag losses require solids of a quite large minimum grain thickness, so balloon launch could allow a much smaller total vehicle, but not less total stages.
JPA's two stage microsat launcher was never going to get close to orbital dV.
John Carmack
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