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Old March 2nd 07, 07:50 AM posted to,,,
Brian Gaff
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Posts: 2,312
Default The 100/10/1 Rule.

Does this take into account the efficiency changes during ascent, and I
wonder who would reuse an engine probably dumped in the Atlantic? I mean
solids are one thing, but...

Not sure about using the bits of the vehicle as payload, Surely you would
eventually have enough spare rcs etc, in orbit to start a space spares shop!


Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
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"kT" wrote in message
I've been simulating single stage to orbit (SSTO) launch to low earth
orbit (LEO) in orbiter space flight simulator for a little while now.

Consider your basic space shuttle main engine (SSME) powered single stage
to orbit (SSTO) rocket. Hydrogen is the most powerful chemical rocket fuel
known (excluding exotics). To reach low earth orbit with a cryogenic fuel
of this nature, a mass ratio of 10 to 1 is required (the 10/1 rule). That
is 10 parts of fuel and oxidizer to one part rocket. After accelerating to
a stable orbit roughly 1% of the fuel is remaining (more or less,
depending upon the ascent trajectory profile, the launch latitude, and
final orbit inclination and altitude). That's roughly 100 parts gross
liftoff weight to 1 part residual fuel (the 100/1 rule) or 10 parts empty
weight to 1 part residual fuel (yet another 10/1 rule).

Thus the usable payload delivered to an orbital station or spaceport is
roughly 1% of the gross liftoff weight, and 10% of vehicle empty weight.
In this case this is fuel which can be immediately converted into energy
and water (via a fuel cell), and water that can then be reconverted back
(using solar energy) into propellant and oxygen. This isn't very much.

However that's the reality of climbing the gravity well of Planet Earth.

In order to increase this payload, the obvious solution is converting the
rocket itself into payload. In this scheme the engine is removed from the
vehicle (roughly 20 percent of empty weight) and returned to Earth in a
cleverly designed nose cone engine carrier, and the tankage, the oxygen,
hydrogen, pressurization, residual fuel tanks and the RCS - reaction
control system, is then immediately pressed into service as payload for
infrastructure in constructing the space station or orbital spaceport
itself. Thus, the usable payload fraction is then increased by a factor of
seven (7) or so, dependent upon the amount of equipment or infrastructure
necessary to successfully reenter and recover a seven thousand pound space
shuttle main engine (SSME) from low earth orbit.

For a reasonably designed single space shuttle main engine powered single
stage to orbit launch vehicle, this represents 3500 pounds of residual
fuel and 25,000 pounds of infrastructure. This is not trivial.

Plus, you get the engine back. Adding some GEM-60s improves the numbers.

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