From: strider@clotho.acm.rpi.edu (Greg Moore)
Subject: Re: DC vs Shuttle capabilities
Organization: The Voice of Fate
Date: Sat, 12 Dec 1992 18:44:09 GMT

In article <1992Dec11.141858.16948@iti.org> aws@iti.org (Allen W. Sherzer) writes:
>In article <zjf2--+@rpi.edu> strider@clotho.acm.rpi.edu (Greg Moore) writes:
>
>>	1) Won't teh crew compartment take up part of the cargo bay?
>
>Of course. On the other hand the standard interface which makes you do
>this reduces integration time which keeps flight rate up and costs down.
>
	You missed my point.  If your crew compartment is in the cargo
bay, where do you put the satellite?

>In the longer run, you may be right. Plumeting launch costs will cause
>payload prices to fall since there will be more and cheaper launches
>plus the opportunity for on site repair.
>
	I eliminated some stuff above, but wanted to add some stuff here.
Actually, plummeting launch costs may contribute to lower payload costs
since people will be willing to build a less fault tolerant system
knowing that if it fails, they can launch another cheaply.  
As for on-site repair, for now DC-? fails for the same reason that
the Shuttle normally does, it can't get up to GEO, you need a 
OTV... in which case it doesn't matter in the long run how you get
into orbit, as long as it is cheap enough.

>>	Also, as for retrieval, the Shuttle has shown that it ain't
>>easy to do.  Will a two day on-orbit time be enough?
>
>It may take modifications to the DC. At the very least you need to add
>a robot arm and an airlock.
>
	Granted, but that's not what I meant.  Will you have enough time
to rendevous and capture the satelite?  It took what 3 days for the
shuttle to capture Intelsat VI? That's aday more than DC-?.
Also, what type of fuel margin would DC-1 have for IN-orbit
manevours? (I realize it has enough for landing, and of course
you don't wnt to cut into that for safety reasons.)

>>	Let's not try to have DC-1 do everything... remember that is
>>where the shuttle went wrong.
>
>But let's use it for what we can. The way to bring costs down fast with
>this concept is to use it.
>
	Use it yes, but use it for what it can be used for economically.
Let's see, we've added an airlock, an arm, additional on-orbit capacity.
Hmm, that adds up, and add complexity.  Yes, let's ok at possibilities,
but not claim t they are definites.

>My view is that we use the basic DC as a 'bus' which can be modified in
>small ways to meet diverse missions. Costs are cut because the same assembly
>lines are used to make DC1-EOT (Earth orbit transfer), DC1-OMV, and DC1-LM.
>
	I have a question about this.  EOT and LM should require roughly
the same amount of fuel, no? (as I recall, the energy to get into lunar
orbit is about the same as GEO? I'm ignoring landing here).  But how
economical is it to transport that fuel TO orbit?  Am I correct in 
remembering you saying about 10 DC-1 flights?

	Also, does it make sense for the DC1-EOT and OMV and LM the same.
The requirements for landing gear are different.  The requirements for
fuel transfer MAY be different.  What about thermal protection.  LM 
won't require any to land on the moon, but what about reentering earth 
orbit or earth landing?


>This makes the basid DC a building block of a more extensive space
>infrastructure.
>
	Granted.  And that is attractive.

>  Allen
>
>-- 
>+---------------------------------------------------------------------------+
>| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
>|  aws@iti.org     |  nothing undone"                                       |
>+----------------------134 DAYS TO FIRST FLIGHT OF DCX----------------------+


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