Message-ID: <gaPoQLO00VcJ85ek5=@andrew.cmu.edu>
Precedence: junk
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Fri,  8 Jun 1990 02:35:04 -0400 (EDT)
Subject: SPACE Digest V11 #508

SPACE Digest                                     Volume 11 : Issue 508

Today's Topics:
		 Re: T.A.F.  --  Tough Apollo Trivia

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  space+@andrew.cmu.edu.  Other mail, esp. [un]subscription notices,
  should be sent to space-request+@andrew.cmu.edu, or, if urgent, to
			 tm2b+@andrew.cmu.edu

----------------------------------------------------------------------

Date: 6 Jun 90 17:46:54 GMT
From: eru!luth!sunic!mcsun!ukc!strath-cs!cs.glasgow.ac.uk!ron@bloom-beacon.mit.edu  (Dr Ron Poet)
Subject: Re: T.A.F.  --  Tough Apollo Trivia

In article <5603@helios.TAMU.EDU> chrisd@photon.tamu.edu (Chris Duhon) writes:
>
>   1) Direct Ascent - Just get a *really* big rocket and go straight
>         from the earth to the moon, then straight back;
>   2) Earth Orbit Rendezvous - Use several smaller rockets to lift
>         the spaceship in pieces, assemble while in earth orbit,
>         then go;
>   3) Lunar Orbit Rendezvous - Take off in a medium sized rocket
>         and go straight to the moon, but go into orbit around the
>         moon when you get there, land a smaller, lighter craft,
>         then leave it behind when you're ready to come back.
>
>The question I have is this -- Why did they not use a combination
>of options 2 and 3.  That is, launch the LM on one rocket, then
>launch the CSM (Command Service Module) on another, redezvous,
>then go.  That might mean using half the fuel, rockets that
>were less powerful than the trouble plagued F-1's, and thus
>launch vehicles less complex and powerful than a Saturn V.
>
>Once it is decided to have *two* separate spacecraft and you have
>committed yourself to a deep-space rendezvous, then EOR seems
>to be a natural conclusion -- just lift those two craft separately.
>
>How 'bout it?
>
>chris
>--
>
>| Chris J. Duhon                 |  chrisd@photon.tamu.edu
>| Dept of Computer Science       |
>| Texas A&M University           |


Lunar landings can be categorised by their behaviour at the moon

1.	Direct Ascent:	The whole spacecraft lands and takes of

2.	Lunar Orbit Rendezvous:	Part of the spacecraft lands, takes off
		and rendezvous with the CSM, the Apollo method

3.	Two Rocket LOR:	The LM and CSM arrive as separate rockets.  The LM
		can either be unmanned, involving two rendezvous, or
		manned (risky) and one rendezvous.

	This method only works well if both the CSM and LM are about the
		same weight, in which case only one rocket, about half
		the size of LOR booster needs to be designed.

	In fact the Apollo LM and CSM after Lunar Orbit Insertion both weighed
		about 15 tons and a Saturn 2.5 would have been a good solution.

Earth Orbit Rendezvous is then just a method of building the above rockets
out of smaller pieces.

I have just reread an interview with designer Mishin which appeared in Pravda and
was reported in the March 90 issue of Spaceflight that indicates that the
Russians planned to land on the moon using Two Rocket LOR, and it is interesting
to try and work out the relevant booster size needed.

The 2 man CSM was Soyus, which would have weighed about 6 tons on the return
flight from the moon.  Making sensible assumptions about the propellants used
gives a weight of 8.5 tons in lunar orbit and 12 tons after translunar
Injection.  The Russian LM was designed for 1 man and would have had to weigh
about 8.5 tons, which seems about right when compared with the the 15 ton 2 man
Apollo LM.

If the Russians had followed the American booster design, using Hydrogen for
the second and third stage then they would have needed a booster weighing about
800 tons, just the size of the Proton booster.  They could have used the
Proton first stage and developed a relatively small 25 tons thrust Hydrogen
engine for the other two stages.

Fortunately (or unfortunately) they chose to go with Kerosine, which required
a 3000 ton booster and failed.  Mishin hints that this was caused by rivalry
with Glushko after Korolev's death.

------------------------------

End of SPACE Digest V11 #508
*******************