

NASA Considering Fuel Depots in Space - sylvinus
http://www.nytimes.com/2011/10/23/science/space/23nasa.html

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rbanffy
I cannot imagine how the physics of this idea make sense. You still have to
put the fuel in orbit. You could do the same with orbital assembly of the
vehicle. I suppose you'll have a pretty good idea what you'll use the fuel
for.

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starwed
There is a claim that answers your question in the very beginning of the
article.

> _Currently, all of the fuel needed for a mission is carried up with the
> rocket, and the weight of the fuel limits the size of the spacecraft._

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rbanffy
That doesn't make much sense. You can send a booster stage to orbit, complete
with engine, cluster boosters (or add already full tanks) if needed and dock
the spacecraft (which can be assembled in orbit too) in place. There is no
reason to send empty "fuel depots" to orbit or to transfer cryogenic fuel and
oxidizer in zero-G.

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electromagnetic
I think the point is to minimize launches. 2 launches per mission as you
suggest is eventually going to cost more.

If it takes 10 launches to initially set up and 1 every say 5 fuel ups, then
it's only going to be 12 launches before it breaks even.

Given the Space Shuttles did 135 missions, doing 135 additional launches
definitely isn't cost effective. Not to mention you wouldn't have to re-enter
a vehicle or do another launch if you wanted to extend a mission.

It would pave way for transfer and potentially one day freight transfers in
space. Also it gives the potential for "Oh Space X you need fuel, well look
who has a fuel depot bitches."

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rbanffy
The number of launches should be more or less the same, since the mass that
gets to orbit is more or less the same. With the advantage pending towards
placing already full tanks in orbit because you don't have to launch a
separate tank plus the apparatus needed for the fuel transfer.

Unless this "surprise you need fuel" thing becomes common, something _very_
unlikely because you usually know what you are going to do in orbit, this
"fuel depot" thing makes no sense at all.

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wanorris
The best part of this idea is that it's incremental. Past manned missions seem
to have a long period when stuff gets studied, then when it comes time to
spend the real money, it gets killed in favor of the study phase for some
other mission.

By costing a comparatively modest amount at a time over a long series of
missions, it's more likely that it will be easier for Washington to complete a
mission that's already well underway and take credit for it than to kill it to
save a little bit more money at that point.

And to be really pessimistic, even if it does get killed halfway through, if
we've put a fuel station in space and started filling it, we can at least try
to reuse those resources for whatever the next mission is.

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electromagnetic
What I think is the greatest potential here is that this is essentially paving
the way for the government to begin selling this fuel to companies that can't
afford to put their own fuel depot into space.

Why is this good? Because once Congress sees the potential to make profit from
NASA, then we'll see hundreds of billions dropped into it.

I believe the next step to this would be to set up a depot in orbit around
Mars to reduce the weight necessary for a mission to Mars.

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sylvinus
If somebody could explain why storing fuel in space is more efficient than
just packing what's needed for each mission? :)

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sixtofour
If you move to a new apartment, on the third floor, it's "more efficient" to
carry all your stuff up on one trip. But there's a limit to how much you can
bring up on that one trip.

If you make a lot of smaller trips, there's almost no limit on what you can
have once you take the "final" trip up.

Also, if you drop something on one of those trips up, you don't lose all your
stuff (and you) at once.

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bfe
tl;dr: Congressman Rohrabacher (R-Boeing) is "shocked" that NASA would
consider rejecting a plan that would have created an artificial need to order
a bunch more expendable rockets, even though NASA already found that the plan
would have been far more expensive and unreliable.

