Newsgroups: sci.space.policy
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Endeavour Class Missions
Date: Sun, 12 Sep 1999 15:27:01 GMT

In article <7rcb4p$ffq@peabody.colorado.edu>,
Frank Crary <fcrary@rintintin.colorado.edu> wrote:
>>Seems to me that either the Earth-Moon  or Sun-Earth Lagrange points
>>would be a better place to start a Mars mission then LEO...
>
>If you plug in some numbers, you will see that the total delta v
>is higher if you stop along the way...

Only if you insert into your interplanetary trajectory direct from the
high orbit.  If you do insertion using a close Earth flyby, you recover
almost all of the losses; indeed, you may actually show a gain, because
you can do the insertion at a lower altitude than a LEO assembly base
could safely maintain.  The only losses are whatever delta-V you need to
go from your assembly orbit to the Earth flyby, plus a similar amount
earlier to inject into the assembly orbit.  With a good choice of assembly
orbit -- say, a halo orbit around the Earth-Sun L1 point -- those delta-Vs
can be very small.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)