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Accumulate Fuel at Space Station?
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Accumulate Fuel at Space Station?
Phil Karn wrote:
Basically, the space station -- as conceived and especially as built -- is pretty much useless for all of the magical things it was once claimed would do. Acting as an interplanetary way station is just one of them, and the people who said it would should have known better. It's an incredible scandal. Well, one might be able to get around this by launching into a highly elliptical orbit, changing plane at apogee, then leaving orbit with another burn at perigee. Seems awfully complicated though, and it adds at least two more passes through the radiation belts. Paul |
#23
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Accumulate Fuel at Space Station?
JRS: In article , seen in
news:sci.space.science, Phil Karn posted at Sun, 14 Mar 2004 09:10:23 :- Although many planetary missions begin with an earth parking orbit, its orbital plane is carefully chosen to coincide with that of the interplanetary trajectory. To do otherwise would waste a *lot* of fuel for no good reason. But the space station is in a high inclination orbit to improve coverage of the earth and to make it easier for the Russians to reach it from their high latitude launch sites. Since all of the planets are in orbital planes not far from our own, they're all very hard to reach from a high inclination earth orbit. If the initial ISS orbit departure is with a correctly-timed burn taking it to the Moon's distance (for example), where its speed will be significantly less than the Moon's speed, which is about 1 km/s, then a small sideways burn (guesstimate : under 500 m/s) will change the plane of the orbit to the desired one. Then, after another half-orbit back to ISS height (or tweaked to lower), another major burn is used for final departure. It is well-known that propulsive burns should be done at low altitude; this way, there is more low time available for a burn, allowing less thrust and a smaller engine. The extra week or two for departure does cost consumables; OTOH there is also the advantage that re-lighting of the main engine is tested near Earth, and the manoeuvring engine can be tested at the plane change burn, with auto-return whether it works or not. I've not worked out the trade-offs. Conceivably, the plane change could be done by lunar gravity-assist. *** I believe that I used your software for a while; and that a sort-of- colleague still does. -- © John Stockton, Surrey, UK. Turnpike v4.00 MIME. © Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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