NASA Considering Fuel Depots in Space | Hacker News Reader

NASA Considering Fuel Depots in Space

nytimes.com

12 pointssylvinus11 comments

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.

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.

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.

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."

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.

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.

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.

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

Well it's easier to engineer, cheaper to construct small rockets. All you need to get to the moon is a reusable rocket capable of making orbit, and enough flights.

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.

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.

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