Originally posted by WoodPush
Is it really as lucrative as implied here? Space travel isn't exactly cheap. Is it even feasible?
It's feasible but I would have to be convinced if I were the venture capitalist sticking millions or billions into such a project. For instance, if we found an asteroid that had a high concentration of platinum or palladium, a few tons of that stuff back on earth would go a long way to pay for such a project but iron?
Iron is star poop. The last of the line for fusion, you can't get any more energy out of iron either with fission or fusion so it comes out by the megaton from stars and coats everything in its path so there would of course be millions of asteroids half iron but unless you could figure a way to get it down to earth ala meterorite or something it would be worthless from a mining point of view.
Rare Earths, platinum, palladium, indium, that kind of stuff could be well worth it from asteroid mining but it would have to be proven a given asteroid had high concentrations of that stuff before any kind of mining equipment was sent there. So the first order of business would be analysis probes sent to at first the big guys, Vesta and so forth.
You could probably see from IR and UV and other techniques the hints of the major stuff we would want just in a fly by if you had the right tools on the craft. Otherwise you are talking explorers, humans, who of course have not even gone past the moon yet much less gone to Vesta or any other asteroid.
On the other hand, we may find nice deposits on the moon, which is a lot closer and lends itself to magnetic powered ramp launches to sling stuff from the moon to Earth, such devices could be powered by solar energy, where there is an infinite supply of on the moon, no atmosphere to block solar and no hailstorms, except for the occasional meteorite, a few acres for solar on the moon at 20% would get you megawatts of energy for a rail gun launcher, couple of klicks long in a vaccum, it would easily be able to escape moon's gravity.
The same thing could be built on an asteroid but the solar flux there would be maybe only 10 percent of what we have here so there would need to be a lot more area collected. On the other hand, the escape velocity of an asteroid is puny even by Lunar standards so the energy required would also be lower so it could work out. No fuel needed to get the stuff back to Earth.
BTW, just for example, if you had a system of 100% usage of energy, to accelerate 555 pounds at one G would take 32 horsepower. Of course we can't get anywhere near 100% but suppose it was 50% efficient for a rail gun on the moon, since there is no atmosphere, that would mean something like 60 Hp to get say 500 pounds off the moon. Just for grins, call it 50 kw for 500 pounds after all the friction, electrical and other losses taken into account so 200 Kw per ton, not a bad deal energy wise!
200 megawatts would sling 1000 tons off the moon, and it doesn't have to be all at once, it could come from 1000 launches of one ton each and you have to have a collection mechanism in orbit around the Earth but the engineering has already been worked out for such a project. Magnetic catchers (assuming the boules coming in from the moon are aimed precisely) would slow them down, like a rail gun in reverse and the neat thing about that is you get free energy.
Slinging stuff off the moon in a vacuum like that with its relatively low energy requirements as apposed to using rockets, which are extremely inefficient energy-wise is a win win situation.
Because the stuff is launched at only lunar escape velocity, some six times less than Earth's, when it comes into the Earths gravitational field, it starts building up kinetic energy, it was calculated to be pound for pound, kilo gram for kilogram, 6 times the energy density of gasoline, which is about 47 Mj/kg. So the magnetic catcher takes that 500 pound plug, say, and slows it down from about 25,000 mph to orbital velocity and the catcher is a giant generator at that point, the kinetic energy of the 500 pound slug going 25,000 mph minus 18,000 mph= 7000 mph, is very significant and the catcher is designed to handle that amount of energy and stop the slug dead in its tracks.
Then the satellite that has that catcher gets free energy for its own use and could even beam excess energy down to Earth.
Here is a great vision: a space elevator, if and when we can get that technology working, could be used in conjunction with the magnetic catcher, take the now zero velocity relative to orbital velocity, use that extra energy to go back to earth and use the elevator to transport the slugs from the moon to earth. All with no energy inputs needed anywhere except the solar panels on the moon.
Great concept, eh!