From: strider@clotho.acm.rpi.edu (Greg Moore)
Subject: Re: DC vs Shuttle capabilities
Organization: The Voice of Fate
Date: Thu, 17 Dec 1992 03:14:06 GMT

In article <1992Dec14.175934.5993@iti.org> aws@iti.org (Allen W. Sherzer) writes:
>In article <g9g2v_p@rpi.edu> strider@clotho.acm.rpi.edu (Greg Moore) writes:
>
>First of all, which crew? The flight crew rides in the cockpit which is
>above the cargo bay. If more crew are needed, then the satellite can
>ride in the part of the cargo bay not used by the extra crew.
>
	Sorry, my mistake, I got confused on the crew accomodations of the
proposed DC-1.

	Another question though:  Am I correct in recalling that the goal is
to use pilots, and not astronauts (at least in the NASA sense) to fly the 
proposed DC-1?  Who will do satellite repair? Who pays for training? The
customer, or will McD (or whoever operates it) have "on-call techs" that
you can pay extra for.  (I'm not calling for you to predict the future
(thouh seem to believe at times you know it... :-) just an idea if SDIO
has given this any thought?

>If it turns out that this isn't roomy enough, then you use the technology
>developed under DC to build a larger vehicle. After all, DC will be a usefull
>piece of technology but it isn't the only spaceship which will ever be built.
>

	But wait, DC-1 was going to solve all my problem, and slice my bread.
Seriously though, I think this leads to a comment directed to you, Gary,
Michael, and Edward and any others I've forgotten.
	We've all argued various merits, benefits and drawbacks of the DC 
program, but sometimes I think we forget what we are talking about.  Are
we talking about DC-X, the planned DC-Y, or the proposed DC-1.  It seems
to me that everyone here agrees that DC-X is a good idea, whether or not it
works.  As long as it is treated like an X program, it seems to get a lot
of support.  We will learn from it.  Perhaps we will find everything 
will be as "easy" as they say, or perhaps they run into stumbling blocks.
But we won't nkow until we try.
	DC-Y doesn't seem to be of much conflict per se.

	I think we differ big-time when it comes to DC-1.  Allen seems
to me to be saying, "Things will work out, and this is how it will be."
I think that is the attitude that bothers me the most.  That is the
exact same thign that was said with the Shuttle.  NOw granted, there are
some major difference, major enough to make me believe that DC-1 has
a better chance than the Shuttle did.  However, we can't be sure
until we start FLYING these things.  A better way of thinking may be,
"If things work out, this is how it will be."
	I don't mean to pick out you Allen, and I don't mean to pick
on your belief in the DC-X program, but sometimes it seems to me you're
trying to sell it before it's tested.

Off the soapbox.

>>	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.  
>
>Exactly.
>
	Ah, we agree.  That's nice to hear. :-)

>>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... 
>
>Although a DC with a robot arm and some avionics changes may be the
>OTV. Certainly the engines for a DC will be just what an OTV needs.
>
	Is this inherent in the RL-10 design, or does work need to
be done on the tanks to make sure the fuel is near the outlets?

>>>>	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-?.
>
>Load the pallet with some extra power sources, add some solar cells and
>your all set.
>
	So, your pallet now has attachments for consumables that DC-1 can
draw on?  (Hmm... let's just use a EDO... Oops, no, ITWIH Syndrome. :-)
(Seriously, I know, it probably won't fit.)

>>Also, what type of fuel margin would DC-1 have for IN-orbit
>>manevours? 
>
>DC-Y has a fair amount of fuel for on orbit delta V but I don't
>remember the exact numbers. How much DC has will depend on the
>design requirements and who pays the bills.
>
>But note that on a DC-Y you can power the fuel cells, main engines, and
>RCS from the same source. This allows you some very powerful tradeoffs.
>
	True, but I'd still like to have a separate fuel reserve or
power supply.

>>(I realize it has enough for landing, and of course
>>you don't wnt to cut into that for safety reasons.)
>
>At least enough to get back to the orbital fuel dump.
>
	Oh, gee, I didn't realize we had one.  And what if it isn't 
in your orbital plane?  Might was well re-enter...

>>	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.
>
>Agreed. But they don't look all that hard given a working DC.
>
	And they didn't look all that hard given a working shuttle.
Hmm, RMS came from Canada, and even at that was a bargin.  So I'm sure
DC can use one.
	Airlock, that's simple enough.
	On-orbit capacity: That's a little tougher.  Depends on how
your DC is scarred, etc.  BTW, what is the FAA say about adding fuel tanks.
I know the 747-400 didn't have to be completely recertified... I'm sure
DIC won't have to be either, but I'm sure there would have to be some 
testing.

	Sounds good.  Prove to me it works with flying hardware, and
I'm sold.  

>>	Also, does it make sense for the DC1-EOT and OMV and LM the same.
>
>Not 100% the same. For an OMV I would strip off the thermal protection
>system, add attach points outside for additional fuel and hardware (like
>arms), I might look at lining it with solar cells for more power. For a LM
>I think you would need to provide better insulation to reduce fuel boil off,
>replace the landing gear to give it a larger footprint (like the Apollo LM),
>and beef up the TPS for aerobreaking.
>

	Beef up the TPS how much?  Also, I believe that Henry pointed out
that it ieasier to do a direct re-entry than a return to orbit.  (I can't
recall why, and wasn't celar at the time I read it, so I may be wrong.)
If so, will you have enough fuel to do this.  Remember, until you have your
moonbase set up, you've got to leave LEO, land on the moon, take off, and
either re-enter, or re-enter LEO.
	Now your changing your landing gear.  How, what does this entail?

>This will allow us to use the same core vehicle for multiple applications
>which will allow development to be amortized over more vehicles and reduce
>construction costs since we are building more core vehicles.
>
	Ayup, and if we had built Shuttle-C, we could have amortized
engine costs a tad more, and amortized facility costs more.

>      Allen
>
>-- 
>+---------------------------------------------------------------------------+
>| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
>|  aws@iti.org     |  nothing undone"                                       |
>+----------------------131 DAYS TO FIRST FLIGHT OF DCX----------------------+


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