Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!oliveb!pyramid!prls!philabs!micomvax!ncc!alberta!ubc-cs!fornax!zeke
From: zeke@fornax.UUCP (Zeke Hoskin)
Newsgroups: sci.space.shuttle
Subject: Re: QUESTION: Shuttle round trips to the moon?
Summary: the problem is aerobraking
Message-ID: <855@fornax.UUCP>
Date: 20 Jan 89 19:26:14 GMT
References: <14549@oberon.USC.EDU> <17360001@hpsel1.HP.COM> <492@geovision.UUCP>
Lines: 33

(everything about Phoenix and shuttles deleted, but Alastair's signature
retained for esthetic reasons)
> -- 
> "The problem is not that spaceflight is expensive,  | Alastair J.W. Mayer
> therefore only the government can do it, but that   | alastair@geovision.UUCP
> only the government is doing spaceflight, therefore | al@BIX
> it is expensive."                                   |

   A Lunar round trip has to :take off from Earth, achieve Lunar injection,
slow down enough to land on the moon, take off from the moon, achieve
Terran insertion, slow down enough to land here, and land. It makes good
sense to use some kind of LEO system to tank up/assemble before step 2,
and likewise a low-lunar-orbit system between lunar takeoff and T.I.
   However, an object approaching Earth from Lunar orbit is coming fast.
The options are: burn up the same amount of delta-vee needed for Lunar
insertion from LEO in order to re-enter LEO, match with Earth lander, and
land; or use Earth's atmosphere to aerobrake and land. (All right, you
could also aerobrake in a shallow graze of atmosphere, trying to slow
down enough to enter LEO with a minor correction, but this requires you
to carry pretty much everything you'd need for direct landing, so why
bother?)
   It would be easier to tank up a Shuttle in LEO and fly it to LLO and
back to an aerobraked landing, than to send something else to the Moon
and have it rendezvous with the Shuttle on the way home. Not _possible_,
I'm not claiming that, just _easier_. We start out with a project to
build/modify an orbiter to do LEO refueling and, say, make it out as far
as Clarke orbit... (NB: refueling the hypergolic OMS motors would be
safer and easier than trying to restart the LH2/LOX main ones.)


-- 
What makes one step a giant leap|Zeke Hoskin/SFU VLSI group,Burnaby,BC,Canada
Is all the steps before         | ...!ubc-cs!sfu_fornax!zeke