On Sat, 15 Jun 2002 12:40:28 -0700, Randall Clague
<[EMAIL PROTECTED]> wrote:
>As you've discovered, SSTO with a small vehicle requires trajectory
>optimization, which in turn is a balancing act as you trade off drag losses
>against gravity losses. There is probably a minimum size (for a given
>shape, mass fraction, propellant type, engine, etc.) below which a single
>stage vehicle can't make orbit.
So I did a structural model for this really cool pressure fed TSTO.
Nothing fancy, 6061 T6, about 1000 kg GLOW, 10 kg payload, delta-v
9000 m/sec. You could take the thing out to the launch site in a
small U-Haul truck, and put 22 lbs in orbit for about $1000/lb.
Definitely within the reach of motivated amateurs, and probably
marketable as well. Way cool.
Next step, trajectory modeling.
Drag *killed* me. It didn't even make a decent sounding rocket.
I'm currently doing a parametric analysis, varying thrust, propellant
load, aspect ratio, and payload. What I've seen just from the first
few runs is that crawling along through the troposphere at M 0.5 or so
gets me the best final altitude. I throw away a lot of fuel "standing
on a pillar of fire," as Mitch puts it, but the alternative is burning
harder to get through the atmosphere quicker. This decreases my
gravity losses at the price of increasing my drag losses even more.
(Gravity losses are linear, but drag is proportional to the square of
the velocity.)
This sure is frustrating.
-R
--
"Sutton is the beginning of wisdom -
but only the beginning."
-- Jeff Greason
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