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.

--
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