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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:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/960925a.html
A discussion of the shuttle solid rocket motors can be found
at:
http://liftoff.msfc.nasa.gov/Shuttle/About/srb.html
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.
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Applications
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Space Shuttle orbit/de-orbit insertion,
circularization
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First Flown
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April 12th, 1981, on the Orbiter Columbia
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Number Flown
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14, to end of 1993
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Dry Mass
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118 kg
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Length
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195.6 cm
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Maximum Diameter
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116.8 cm
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Mounting
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gimbaled ( 7 degrees yaw ( 6 pitch by two
electromechanical actuators for thrust vector
control
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Engine Cycle
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pressure-fed (improvement underway for
pump-fed)
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Oxidizer
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6743 kg nitrogen tetroxide in each pod (pods can
be cross-linked)
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Fuel
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4087 kg of monomethyl hydrazine in each pod
(pods can be cross-linked)
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Mixture Ratio
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1.65:1
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Thrust
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26.7 kN vacuum
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Isp
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316 sec vacuum
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Expansion Ratio
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55:1
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Combustion Chamber Pressure
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8.62 atm
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Cooling Method
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fuel regenerative for chamber, radiative for
nozzle
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Burn Time
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qualified for 500 starts, 15 hr/100 mission life,
longest firing 1250 sec, de-orbit burn typically
150-250 secs
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David Palmer, Allie Cliffe and Tim Kallman
for the Ask an Astrophysicist team
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