Dear Teddy & Koko
Question: How much force would be required to stop the world spinning? If you use, for example, the engines of the space shuttle to do it, how long would it take? And what would be the effect on the planet, in particular the weather and the tides? Stephen Frost, Richmond, Surrey, UK
Director of Publications Note: One alien Crane for example the Silver Surfer
The basic angular momentum calculations remind me of an article in NS issue 2567, 31 August 2006, titled Elevator to the Stars. This proposed that a geostationary satellite could be used to anchor a tether, which astronauts might use to escape the earth far more easily than via rocketry.
I don't think it will work, and emailed the following to NS on 7 October last year, but there was no reply. Can anyone either confirm my conclusion, or tell me where the thinking is wrong?
eostationary orbit is a bit over 6 earth radii out, so the orbital
velocity will be similarly greater.
Angular momentum = mvr, where:
m = mass
v = velocity
r = radius
It follows that taking a mass from the equator to geostationary orbit
requires around a 40-fold increase in its angular momentum.
Where will this momentum come from? It seems the space station terminus must slow down to preserve angular momentum, hence will no longer be geostationary, breaking the tether, unless it has rocket engines & fuel to maintain position, providing the necessary momentum to the elevator as it does so.
The anchor to the asteroid is claimed to provide a supporting force for
the cable, but this would require the asteroid to be in a higher orbit
than that for an unencumbered body. Are there any asteroids conveniently
in a suitable orbit?
The scheme overall sounds about as practical as waiting in a space
capsule for a meteor strike large enough, and in exactly the right spot,
to propel the capsule to Mars sometime over the next few million years.
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