Oh come on! No-one stands the remotest chance of getting viable amounts of rock down from space for another two generations. We don't have any mechanism to get the rocks down (a space anchor - not even remotely close to necessary material strength / weight ratio), let alone the ability to survive journeys to closest rocks.
Give it 20 years of people living on the moon or Mars and solving the supply, radiation and working problems, then I will believe we might risk throwing a megatonne of iridium at Earth orbit.
But great way for rich dreamers to hob nob with other rich dreamers. Enjoy it folks. Just don't invest.
SpaceX is about commercialising an already-achieved process (ascending into Space and returning safely to Earth). We know we can do it - can we do it cheaper, or with different re-entry profiles?
And to be honest, with the record of successful unmanned missions to Mars (running at what, about evens just to make it to the surface) I am not holding out hope.
My best guess will be space-swarm -launch 500 independent solar powered motors, fling them at the general direction of a rock, and hope the 20 that attach can nudge it in side the moons orbit, where a later permanent colony can grab it. Smashing into the moon is less damaging. Hell, just bang it straight into the moon and pick up the pieces later on.
Damn, from "it'll never work" to "why not try it this way guys" in less than an hour. Need to work on curmudgeonly.
Still, even if it's on the moon, we cannot get it back to earth without the same risks. And picking it up from the moon, yeah we have guys just waiting around right now.
In-orbit infrastructure will have to be built, though probably not anything as exotic as a space elevator.
One approach to get material down: create basketball-sized meteors during the mining process or in-orbit with smelters. Coat or cover them in a material that will make their re-entry less wasteful. Using some kind of thruster, direct these into a de-orbit ending on a raft thing in the Pacific Ocean or parachuted to a deserted area.
For the more precious or dangerous material mined: use cheap glider-style re-entry vehicles.
Why would they try to bring the resources down to earth? It is so expensive to send things out of our orbit they should be selling the material to future floating stations, like the ISS. Also, satellite manufacturers and space probes could be constructed in something like the ISS with the majority of their heavy parts being made from asteroids.
Hmmmm. I don't know much about material science, but maybe they are mining silicon and fabricating solar panels? What is the heaviest part of a probe or satellite?
I can see a way to get the rocks down. Cut off chunks of particular size, cover them in nets and tie the nets to a little robotic space tugboat, that uses rocket power to pull the rocks into earth orbit and then lands with the rocks in a parachute. The space tug boat will be reusable of course.
Radiation is also a tough problem. Most space metals should be radioactive. They have been swimming in space radiation for millions of years, so even metals that are usually non-radioactive, like iron should get plenty of opportunity to get activated. And once a metal is radioactive we have no way to fix that. The only fix is to wait for it to deplete itself. And that is usually a very long wait.
But now that I think of it, perhaps in an asteroid only the outside metals are radioactive. Perhaps the inside of the asteroid gets shielded by the metals on the outside that absorb all incoming particles. If that's the way things work, one should be able to mine non radio-active metals on the inside.
So I see nothing impossible, but it will be difficult.
Why is that something that we should not worry about? (I am not being sarcastic, honestly asking, nuclear physics is not my primary expertise.) Yes many of them seem to have short half-lives but one of them has a half life of 1.5 million years.
Also I am not sure these are the only iron isotopes. This seems to be a list of "naturally occurring" iron isotopes which usually means "naturally occurring on Earth".
Also another thing to worry about is the isotopes of platinum and platinum group metals that seem to be the main and most lucrative target of space mining.
> Yes many of them seem to have short half-lives but one of them has a half life of 1.5 million years.
Which means it's completely safe. If it has a half-life that long, it won't be releasing radiation at a very high rate. Hardly enough to register above background. The isotopes you have to worry about are the ones with in-the-middle half lives- long enough that they don't deplete themselves in a conveniently short period, but short enough that they produce a dangerous power output.
That depends on concentrations of the isotope in the metal and the amount of metal we will be using. I have no idea what the concentrations of iron isotopes in meteors are and which iron isotopes are there, but I do not think it is correct to automatically say that radioactive isotopes with long half-lives are completely safe.
> Most space metals should be radioactive. They have been swimming in space radiation for millions of years, so even metals that are usually non-radioactive, like iron should get plenty of opportunity to get activated.
Not quite sure why we would want to get it down to earth myself. Think of the markup you could sell it for by just leaving it in space. No more need to launch rockets carrying materials/prefabs - it will just happen in space.
"Yea, I know our iron is XXX% more, but you know its already in space...."
And if its for mining for energy just create the energy in space and beam it down. Rather simple.
Rocks with enough metal ores to be useful and in sizes that can make it through re-entry with a useful quantity of material left tend to do other undesirable things, like smash stuff, just ask the dinosaurs.
Well, that one might be on the large side. Besides, a controlled re-entry from LEO would have lower speeds than a random solar system impactor and could also use aerobraking.
It still might be too risky, but it doesn't seem totally, obviously infeasible to me.
Give it 20 years of people living on the moon or Mars and solving the supply, radiation and working problems, then I will believe we might risk throwing a megatonne of iridium at Earth orbit.
But great way for rich dreamers to hob nob with other rich dreamers. Enjoy it folks. Just don't invest.