On Orbital Fuel Stations

dylanduck writes "Being able to fill up your spacecraft from a fuel depot in orbit round the Earth or Moon is key to the long-term prospects of astronauts exploring the solar system, according to NASA engineers. Trouble is NASA doesn't want to build it themselves. So there's $5 million for any enterprising groups who can develop a simple version themselves."

Comments

It's doable

[PatrickThomson]

Obviously you need atoms up there, which have to come from somewhere, but splitting them into fuel is easy, you're floating in space with all this sunlight. The problem is that if you carry a kilo of water from the surface and then swap it for a kilo of hydrogen/oxygen when you get to space, the benefits are minimal (easier storage?). This would work well coupled with a captured icy asteroid, even a small one.

Hmmm

[hyfe]

Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

So sure, once you get liquid hydrogen from the moon / some other energy source it'd be usefull.. which pretty much means we need a moonbase first.

Re:Hmmm

[Funkcikle]

"$9 a gallon? Let's just orbit a bit longer till we find a cheaper one."

Re:Hmmm

[MichaelSmith]

Erm, you still have to get the fuel up there right? .. and the cost of putting something up there is still reasonably proportional to weight?

Fuel depots make sense for aircraft on Earth because you can use cheap surface transport to deliver the fuel, store it, and then load it into your aircraft when needed.

This might work in space if you have ion powered slow boats to ship the heavy stuff, and fast human carrying vehicles to load up on fuel. But we are not that advanced yet. If we go to mars any time soon it might make sense to launch the cruise stage unmanned and then hook it to the command module in earth orbit. That would be a kind of fuel dump.

Re:Hmmm

[Darkman, Walkin Dude]

There might be methods whereby you wouldn't need to carry the fuel with you, for example with a space elevator. However, just what advantages would a space elevator offer over a tower launch? (I've used parts of this post before, but I have since refined my ideas). I contacted a man responsible for a similar idea a while back, the skyramp (warning: hideous javascript menu may break firefox), Carlton Meyer, and had a dialogue in which he pointed me to a tower launch archive.

The ideas I see bandied about there are similar to what I had in mind, which would be essentially an 11km tall tower (think pylons rather than skyscrapers, based at sea), with evacuated airless launch tubes, using nuclear reactors to power a maglev or pulley system to accelerate vessels to escape velocity. These would then emerge above the end of the troposphere, with it's associated weather and air pressure, and have little to no fuel needed to match the earth's gravity, meaning you could do a lot more while you were up there. At a reasonable acceleration (5 to 7 g's) you would be in geostationary orbit. From there you could build a fully system wide ship or ships, as its much easier to escape the planet's gravity from GEO than from the surface.

Not only would this enable multiple launches daily, it is, unlike the space elevator, readily achievable with today's technology, and financially viable as well. Given NASA had an annual budget of $16.2 billion for 2005, and a nuclear power plant costs a cool billion to build, give or take, we could have this up and running in a few years.

Re:Hmmm

[NOLAChief]

If we go to mars any time soon it might make sense to launch the cruise stage unmanned and then hook it to the command module in earth orbit. That would be a kind of fuel dump.

Effectively that's what's being planned with the earth departure stage for the proposed lunar missions. That stage would be launched on the Cargo Launch Vehicle into earth orbit, where a CEV launch would rendezvous with it for a trip to the moon. See the Project Constellation article here.

Have we learnt nothing.

[Kaptain_Korolev]

Honestly, have we learnt nothing from Jerry Bruckheimer's excellent film Armageddon.

Refuelling in orbit is dangerous!

Next they'll be suggesting we man these orbital filling stations with drunken Russians. I only hope Ben and Bruce are there to sort things out when matters go awry.

I, for one, welcome our oxygen yielding overlords!

[holdenholden]

I say good for NASA. They are finally starting to realize that science can be done outside the government laboratories too. An (academic-type) researcher wastes plenty of time begging for money, writing grants and often balancing a teaching load. In industry, on the other hand, you worry less about budgets and more about what you are trying to achieve and how to achieve it. There is a flip side as well--in academia you are free to work on pretty much anything you like, while in industry you work on whatever your manager wants you to work. In the happy case when your interests and the company's interests coincide, you are only limited by your skills and your knowledge.

Space One proved that a competition with a good incentive can produce results faster than state sponsored research. I hope the trend will continue.

Zero Gee problems?

[Cicero382]

Has anyone else noticed that zero G is a constant PITA for nearly all space applications?

A short list includes:

Human health (bones, muscles, fluid accumulation etc)
Environment (air flow, hygeine)
Fluids in general (measuring, pumping)
Going to the toilet (or john)

And lots of others.

I have a question: Why aren't we putting some effort into artificial gravity? I mean centrifuge effects - not Star Trek. After all, we're expending all this effort into individual engineering solutions for each problem. If we had AG of some sort, wouldn't that remove the need for that?

Just my 2 pennies worth.

Re:Zero Gee problems?

[GroeFaZ]

Obviously, the cost-benefit-analysis, at the current state of technology, does not speak in favor of simulated gravity or the engineers would've done it already. Rocket engineers must justify every pound of mass they want to put into space (which is, by the way, an argument against manned space flight), and, while needless to say, it's just a LOT easier and cheaper to let an astronaut pee into a plastic bag and toss it out the window than designing the rocket with 2 huge rotating discs tens of meters in diameter. Ditto for all other points you mentioned.

If and when our technology has matured enough so we can start designing RAMA-style spaceships or large spacestations with permanent crews of dozens or hundreds, then this or another kind of AG will certainly be included.

Re:Zero Gee problems?

[smilindog2000]

It's not as bad as people think. You need a long cable, with a good tensile strength to weight ratio. A simple steel cable will do. On one end you attach the space station, which could be as small as a single module of the current space station. The other end needs a weight, supplies, another half of the space station, space junk... whatever. Then you spin the thing. No big deal.

To dock, you pull up to the middle and grab old of the rotating cable. You then lower yourself down to the station, and enter through a hatch on 'top'.

I think for long-term living in space, it's a win. For the short term, it adds complexity and cost that nobody wants to pay for.

It's not rocket science :-D

Delivering Fuel

[DanielRavenNest]

When I worked at Boeing, I was in charge of a fuel-depot study.
The method we looked at was a BFG to launch the fuel into orbit.
The big gun used hydrogen gas that is quickly heated in a heat
exchanger, then pushes a 600 kg projectile to 2/3 of orbital
speed. The projectile uses some onboard fuel to go the rest
of the way to orbit, then delivers the remaining 100 kg of fuel
to the orbital gas station. The projectile de-orbits and is
recovered to be reused. The projectile is rugged enough that
it can land on anything without damage.

The big gun is very cheap ($100M) compared to electromagnetic
launchers, because it is basically a length of pipe, compared
to a series of coils, switches, and big power supplies. On the
other hand, it is more expensive to operate.

The velocity split between the gun and the projectile depends
on the size of the projectile and how much traffic there is to
orbit. For the case we were studying, delivering fuel to
carry comsats to GEO, we were launching 100 kg a day, or 30 tons/yr
(allowing for downtime).

DRN

Re:Delivering Fuel

[rufty_tufty]

Attempt to use BFG to get into orbit - mostly successful, damn politics though.
http://www.astronautix.com/articles/abroject.htm