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The Question
(Submitted October 19, 1997)
Do today's rockets use the same fuel as the Apollo missions used
in the late 60's and early 70's? I am in the ninth grade. I was wondering
about this because you don't hear very much about changes in technology in
the space program. I assume basic technology must have changed a lot in 30
years, but maybe not.
The Answer
You are basically correct. There have been no fundamental changes
in rocket engines for the last 30 or so years. For more on the subject
check:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970509c.html
However, Aerospike technologies are being developed for the X-33
experimental spacecraft. An Aerospike is like a traditional bell-shaped
rocket engine turned inside out.
For non-chemical propulsion systems, there are several alternatives in
various stages of development. None of these have enough thrust to get
a spaceship off the ground and into orbit, but once in space, a small
amount of thrust over a long time period can produce a large velocity
change.
Ion drives (which use electric power rather than chemical power to eject a
propellant at high speeds) will be used by the Deep Space I mission,
scheduled to launch next July
http://nmp.jpl.nasa.gov/ds1/
By using a tether (long wire) between two masses, orbital changes can be
made. If current is run through the tether when it is in Earth's magnetic
field, the system acts as an electric motor which can climb to a higher
orbit. This technique has been tested several times in space, although
it has not yet been used for practical purposes.
Lightsails are even further in the future. When light hits something, it
gives it a tiny force. If you make a very big, very lightweight mirror,
you can get a very small thrust on your spacecraft.
Jeff Silvis, Leonard Garcia and David Palmer
For Ask a High-Energy Astronomer
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