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The Question

(Submitted May 09, 1997)

What kind of fuel do you use to make the space craft move?

The Answer

A discussion of the Thor-Delta rocket can be found on our web site at:

A discussion of the shuttle solid rocket motors can be found at:

The propellant mixture in each SRB motor consists of an ammonium perchlorate (oxidizer, 69.6 percent by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst, 0.4 percent), a polymer (a binder that holds the mixture together, 12.04 percent), and an epoxy curing agent (1.96 percent). Oxidizer (choose one of LOX, hydrogen peroxide, red fuming nitric acid etc.) and Kerosene hydrazine monopropellant pressurized nitrogen used in space-walking jet packs

An example:

Orbital Maneuvering System (OMS)

The NASA Space Shuttle Orbiter carries two OMS pods (name coined by Aerojet), each housing a single Aerojet OMS engine for orbit insertion, maneuvering, and re-entry initiation. They are capable of 100 missions and 500 starts in space.

Applications Space Shuttle orbit/de-orbit insertion, circularization
First Flown April 12th, 1981, on the Orbiter Columbia
Number Flown 14, to end of 1993
Dry Mass 118 kg
Length 195.6 cm
Maximum Diameter 116.8 cm
Mounting gimbaled ( 7 degrees yaw ( 6 pitch by two electromechanical actuators for thrust vector control
Engine Cycle pressure-fed (improvement underway for pump-fed)
Oxidizer 6743 kg nitrogen tetroxide in each pod (pods can be cross-linked)
Fuel 4087 kg of monomethyl hydrazine in each pod (pods can be cross-linked)
Mixture Ratio 1.65:1
Thrust 26.7 kN vacuum
Isp 316 sec vacuum
Expansion Ratio 55:1
Combustion Chamber Pressure 8.62 atm
Cooling Method fuel regenerative for chamber, radiative for nozzle
Burn Time qualified for 500 starts, 15 hr/100 mission life, longest firing 1250 sec, de-orbit burn typically 150-250 secs

David Palmer, Allie Cliffe and Tim Kallman
for the Ask an Astrophysicist team

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