"Wet" Asteroids Could Supply Space Gas Stations

FleaPlus writes "Water ice was recently discovered on the large asteroid 24 Themis, and Space.com discusses proposals for producing fuel from asteroid ice. NASA and the President recently announced plans for robotic precursor missions to asteroids (and a human mission by 2025), as well as a funding boost for R&D to develop techniques like in-situ resource utilization. Since most of the mass of a beyond-Earth mission is fuel, refueling in orbit would be a huge mass- and cost-saver for space exploration (especially if fuel can be produced in space), but a large unknown is how to effectively extract water in an environment lacking gravity."

Comments

Re:Mining Asteroids like Eve Online

[TheRaven64]

if landing on an asteroid is difficult at best*, and the chances of the asteroid moving in the direction of your ship's travels are slim to none

Why do you assume either of these? Asteroids are orbiting the sun. Their orbits are predictable, modulo some minor variations caused by the (very weak) gravity of nearby ones. It's much easier than, for example, landing on an aircraft carrier, where you have to worry about changes in the wind.

As to the probability of them travelling in the same direction, it's pretty much guaranteed. If you're going from the Earth to the asteroids, you use a transfer orbit, where you are starting in the Earth's orbit around the sun and then injecting enough energy to move you out to the asteroid belt. You end up on solar orbit in the asteroid belt. Any asteroid in the same orbit will, by definition, be going in the same direction and speed as you. Asteroids in nearby orbits will have a small relative speed, and the energy required to enter a transfer orbit to rendezvous with them is relatively small.

Re:Mostly laughable concept.

[johno.ie]

Multiple citations needed.

I don't know where you pulled those numbers out of, but they're completely wrong. Depending on the process used electrolysis can have an efficiency rating of 30%-60%. Nuclear reactors are much better than 20% efficient, unless you think an RTG is a nuclear reactor. Solar thermal power is a better bet for generating large amounts of power for running a space factory. No fuel needed and a few square kilometers of mylar will set it up nicely.

Re:Water for Life, Nuclear for Fuel

[CrimsonAvenger]

wouldnt the energy given off by the thrust in a nuclear reactor be radioactive?

Basically, no.

In somewhat more detail, slightly. Reactor coolant tends to get radioactive after a while. But a nuclear rocket doesn't have any particular part of the coolant present for "a while", since it goes in one end and out the other without any potentially embarrassing recirc.

So, in general, if you used H2 as the reaction mass for your reactor, you could expect some non-radioactive deuterium moderately (which is a joke, in case you didn't get it) regularly, and an atom or so of tritium now and then.

If you used water, the same plus some O-17 and less often O-18.

Note that the amount of radioactive H@ (and O2) will be dependent on the reactor design. Some neutrons are easier to capture than others....