A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Technology
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

What does it make sense to bring back?



 
 
Thread Tools Display Modes
  #1  
Old June 30th 04, 04:28 AM
Hephaestus
external usenet poster
 
Posts: n/a
Default What does it make sense to bring back?

Here's something that's bothered me a bit about the current shuttle design.
You have a fixed size payload bay. And doors. Etc. Ok, that's fine if
you're a launch vehicle, but are you always one? And how much of what you
carry up is really valuable enough that it is cost effective to bring it
back??

It seems that once you're in orbit, all you really want to return is the
crew and the SSMEs. Most of the rest of the stuff, well, either leave it
at the space station for future use, or let it burn up. I.e. have a modular
launch stack composed of:

1. Engine and control module
2. external tank or similar cheap, non-reusable drop tanks.
3. boosters, as necessary
4. Cargo containers of various size

Crew, in this design, is essentially cargo: they can be sitting in their
return capsule inside a cargo container, or on top of the stack, or something.

Crew is ready for a return at any point in flight, more or less. Returning
the engine module with the crew module or separately is an interesting
question. Putting the crew module right next to the engine module seems like
a bad idea for a number of reasons; returning them together would require some
orbital dancing but it doesn't seem to horribly hard.

Basically, once you decide not to go 100% reusable, you have the ability to
decide certain components (tanks, structure, etc) just aren't cost effective
to reuse. Right?
  #2  
Old July 2nd 04, 01:50 PM
David Given
external usenet poster
 
Posts: n/a
Default What does it make sense to bring back?

On Tue, 29 Jun 2004 20:28:51 -0700, Hephaestus wrote: [...]
Basically, once you decide not to go 100% reusable, you have the ability
to decide certain components (tanks, structure, etc) just aren't cost
effective to reuse. Right?


I worked out once shortly after Columbia broke up that for the same cost
as a single shuttle mission, you could launch the same amount of cargo,
personnel and habitat space on multiple Russian launches for about half
the cost. I was figuring on a Soyuz capsule for the crew, and two
heavylifter launches for the cargo; one for the habitat module, and one
for the cargo. I believe I opted for a Proton, although it could have been
an Energia. Once safely aloft, the Soyuz would dock with the habitat
module, which would then rendezvous with the cargo, whatever it was. The
only part of the whole assembly that would return to Earth would be the
crew. Everything else would be discarded.

(Unfortunately, I can't find any of my reasoning --- it's lost somewhere
on the web and Google's being uncooperative.)

Of course, this was a very simplistic analysis. The major cost I didn't
include was the design and construction cost of the habitat module; you'd
need one of these every time you wanted a mission aloft. However, given
that it doesn't have to be man-rated on launch, only on orbit, and that
once the decision has been made to make it disposable it's possible to
simplify construction considerably --- fuel cells rather than solar
panels, thrusters rather than gyros, etc --- I would expect the long-term
cost per unit to be quite small.

I opted not to reuse *anything* mostly because it made the calculations
simpler. (All the off-the-shelf components I was using were disposable.)
It might be worthwhile to reuse some components. The habitat module is a
prime example; if its consumables allow, leave it in orbit and use it
again. Think of it as being a short-lifetime space station. (Reusability
does not necessarily mean that you have to bring it back to Earth.) Also,
you may not want to deorbit them once you've finished with them --- even
as dead mass in orbit, they're valuable. If your orbit allows, add them to
a station-keeping platform; an orbital scrapyard. As and when technology
allows, it may be cost-effective to reuse them, or at least mine them for
components.

--
+- David Given --McQ-+ "I smell a rat; I see him forming in the air &
| | darkening the sky; but I'll nip him in the bud."
| ) | --- Sir Boyle Roche
+-
www.cowlark.com --+
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
No Moon, Mars, or Space in the State of the Union Speech [was Audio of Bush's Speech] GCGassaway Space Shuttle 1 January 22nd 04 01:22 PM
Is it feasible to land on Mars and come back? Chung Leong Technology 16 January 18th 04 01:44 AM
UK Astronomers Look Forward To Looking Back (SIRTF) Ron Baalke Science 0 August 20th 03 05:08 PM
Making Sense Of Centaurs And Their Kin Ron Baalke Science 0 August 10th 03 12:28 AM
DEATH DOES NOT EXIST -- Coal Mine Rescue Proves It Ed Conrad Space Shuttle 4 August 2nd 03 01:00 AM


All times are GMT +1. The time now is 05:28 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.