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"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."
a large unknown is how to effectively extract water in an environment lacking gravity
Easy, bring the asteroid down to earth to extract the water. I don't see why they have to make it so complicated.
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Mining asteroids in EVE is one of the lowest paying professions one can engage in. Perhaps NASA would be better served to focus on killing the spaceships that they encounter around the asteroids for bounties.
After the mexican gulf and it's oil, let's polute space with giant water spills! Who the hell had that good idea at Nasa?
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.
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IANARS, but "extract water in an environment lacking gravity" doesn't seem like that hard of a problem.
Water's a fairly easy substance to deal with - nonexplosive, liquid at easily reachable temps, possibly bound in the asteroid in nothing more significantly complex than an ice conglomerate.
Crushing/pulverizing the regolith and then tossing the mess into a gentle screen centrifuge with even moderate heating (ie above 0 deg C) would seem to do the trick - the water would just flow out the centrifuge walls...wouldn't even have to be 'batched' but could run as a constant process. The spin rate wouldn't even have to be significant, just enough to let inertia do its thing and force the water from the slurry.
At least to my ignorance, this seems at least an order of magnitude LESS difficult/dangerous than electrolysis in zero-g, something we've (AFAIK) got a pretty solid grasp of.
What am I missing?
-Styopa
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.
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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....
"I do not agree with what you say, but I will defend to the death your right to say it"
Even your unmanned probes would work better with an unmanned fuel depot halfway to anywhere.
And no under our feet does not work, only a tiny percentage of the Earth's crust is mineable. And we've gotten all of the easy stuff already, if you look at how many tenths of an ounce per ton is considered profitiable for miners that then use acid solutions to reduce the ore down to what they want, and tailings (the waste) you end up with tons of industrial waster per ounce of useable material.
It has gotten so bad that many companies are now using current technologies to reprocess the tailings of mines/plants closed in the 1970s because those leftovers are richer in what they want than the new mines they are finding.
There IS more raw material in the belt than all of the Earth, and at higher concentrations than any mines being operated anywhere on the planet.
Now, tell me if you really believe what you've said, how much Helium / Helium 3 there is here on Earth, under our feet? What is the cost per ounce?
Helium 3 is $46500 per troy ounce.
Helium we get from Nuclear decay, Helium 3 we get as a byproduct from manufacturing Tritium for Nuclear bombs, we haven't made it in industrial quantities for a while, but there are numberous Medical Imaging and Fusion research uses for this limited resource.
How much is there on the moon?
How many Rare Earth Elements are available in the Belt that would make more efficient magnets for Hybrid Cars and High Speed Trains, but Neodymium is about $1 per Gram, and the price will go up the more demand for Hybrid and Electric vehicles goes up.
How many CD players and Cell phones would you have to recylce the magnets from to come up with the Kilo of Neodymium used in the motor of 1 Prius?