"Wet" Asteroids Could Supply Space Gas Stations 163
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."
Re:Mining Asteroids like Eve Online (Score:3, Interesting)
* kind of like playing 'quarters' by hitting a cup racing past on the back of a flatbed
Mostly laughable concept. (Score:1, Interesting)
Your basic laws of physics limit this to a mostly laughable concept.
You can't make "fuel" out of water, not without the addition of about 9 times the energy you'd get by just using the original energy.
For example, to break up water into Hydrogen and Oxygen, you can use electrolysis, which is only about 11% efficient, so you need 10 units of electricity to make one unit of H and O. On an asteroid, you're gonna have to get the electricity from a nuclear reactor/turbine system, which itself is only going to be about 20% efficient (and you're going to need a few acres of heat-sink to condense the working fluid). So we're up to throwing away 49 units of energy to make one unit of H and O rocket fuel. Or you're going to need a very large and complex solar collector with super-complex metallurgy to generate a high enough heat to disassociate the water. And then there's the extra energy needed to compress and liquefy the fuels. Plus there's the not so small problem of anode poisoning and mineral clogging. The water up there is probably going to be heavily contaminated with typical asteroid junk like sulphates and phosphates. Those will poison the electrolysis anodes and clog up the solar disassociator toote-suite.
The whole idea is really, really, far out, with a negligible efficiency at best and dismal chance of success.
Really? (Score:4, Interesting)
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?
Re:Mostly laughable concept. (Score:4, Interesting)
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?
More important obstacle... (Score:3, Interesting)
Whether or not landing on asteroids is easy (I have my doubts - their motion is likely to be at least somewhat chaotic), there's a more important problem. We're talking about water here, which doesn't, you know, make a very good rocket fuel. Being as how it's already oxidized and everything. TFA indicates that for this to work, you'd first have to grind up some substantial amount of ice-containing rock, microwave it for a while, separate and purify the water... and then you get to electrolyze it. In other words, you need to dump an enormous amount of energy into it. So to do this, you'd have to ship a really large amount of equipment to said asteroid - solar collectors, electricity distribution and storage systems, rock-digging/grinding equipment, microwave machines, electrolysis equipment, hydrogen/oxygen distribution and storage systems, etc, etc. And presumably this all has to be automated, so you need to include computer equipment and then figure out how to actually do automation of a process this complicated.
You'd also need to figure out how to dispose of your rock tailings in such a way that they don't produce a giant abrasive cloud around the asteroid you want to work on, which would almost certainly screw up both incoming vehicles and your solar collectors and other equipment.
I highly, highly doubt you'd be able to make enough trips back and forth to this asteroid for such a system to pay off (all this is going to be extraordinarily expensive to build) before it broke down.
Bottom line: this idea hasn't even gotten to the half-baked stage yet. I wouldn't be bidding up the price of asteroid real estate at this point.
Re:More important obstacle... (Score:3, Interesting)
You'd also need to figure out how to dispose of your rock tailings in such a way that they don't produce a giant abrasive cloud around the asteroid you want to work on
Control your tailings output, and use solar collectors to fuse it into aggregate masses you can use for mass shielding. That's just one idea. You could also collect it and use it in rocket engines if it's fine enough, although that would likely require more energy input than it's worth.
In any case, any cloud that it formed around the asteroid you are working on would eventually be pushed away from the asteroid by the solar wind.
So to do this, you'd have to ship a really large amount of equipment to said asteroid - solar collectors, electricity distribution and storage systems, rock-digging/grinding equipment, microwave machines, electrolysis equipment, hydrogen/oxygen distribution and storage systems, etc, etc.
Or, you ship up the mining/refining equipment, and the machining shops to build the rest. We build these things on earth in automated factories, no reason why we can't adapt our techniques to do so in space. Difficult, massive investment, yes. Half baked fantasy, no.
Whether or not landing on asteroids is easy (I have my doubts - their motion is likely to be at least somewhat chaotic),
*snort* Where do you get "chaotic" from? Even NEA's that pass close enough to earth to have their orbits changed frequently are still trackable, and the changes in their orbits predictable enough to put any number of spacecraft within a few m/s delta V range of them. We are in the process - underfunded, but still doing it - of trying to improve our tracking of NEAs anyway.
SB