But saying "mine asteroids" is like walking up to a stone age man and saying "why are you walking, just build a Bugatti Veyron and drive there dummy".
Even if we do develop technology to mine asteroids (note that several of the companies that were attempting this in recent years have gone out of business or been acquired extremely cheaply) it's still a relatively short term solution. The asteroid belt only contains material equal to (roughly) 4% of the mass of the Moon.
That 4% mass of the Moon is spread out over mind boggling distances that doesn't even start untill roughly beyond the orbit of Mars. At those distances, PV power is going to be worthless, even at Mars the maximum solar irradiance is only about 59% of that on Earth so you're going to need to either build massive solar arrays and use wireless transmission to get the power down to the mining craft/drones (which will have to have considerable batteries in the event they get out of line of sight) or power them with some sort of nuclear solution.
Now, you'll be pulling a good deal of material off that you use purely for reaction mass. You'll also be pulling off a lot of stuff that won't really be worth sending back to Earth in any appreciable quantity like nickel and iron (although could be useful for construction in space and possibly worth sending to Mars) so when you do actually get to rare earths/precious metals you'll likely be able to mine more in a decade (if not a year) than earth has ever of say gold or platinum metal groups, but by even assuming you develop all the technology you need to do this, by the time you safely land it back on Earth it'll still be fantastically expensive to get to point of first delivery and a very very time consuming process purely due to the distances and practical limit on reaction mass for accelerating and decelerating.
Then you're still only talking 4% the mass of the Moon, if you were making a decent effort at mining the asteroids you might pull worthwhile material out for a century or two before you've exhausted the bulk of it and then it is "well, I hope we've developed FTL travel or generation ships!"
I would compare it to telling Wright brothers after their first airplane flight that we will land on the Moon in 66 years. If there will be a reason to do it, we will. Still, I would agree that we will have close to 100% effective recycling of metals before we will start bringing them to Earth from space.
But in time we will start to utilize space resources.
SpaceX, Blue Origin will latch to any possibility to make money in space.
Space mining is exactly how Bezos thinks O'Neill cylinder could be built in 100-200 years.
BTW - You could bet for worthless internet points on Metaculus:
To access an equivalent amount of mass from the moon you would need to strip mine it to a depth of about 23.5km. On earth it would be about 1km. Your point about losing a lot of it as reaction mass still stands, but 4% of the moon is actually quite a lot.
Yes, and it is spread out over a huge amount of space. The asteroid belt occupies 1AU of space that starts 2.2 AU out and and ends 3.2 AU out.
Sure, roughly half of the belt's mass is contained in just four asteroids - Ceres, Vesta, Pallas, and Hygiea.
Ceres alone is the 33rd largest known object in our solar system and simply mining it might be realistic but its orbit is 2.5-3 AU out but from what we've observed it is estimated to be 20% carbon by mass in its near surface, that is a LOT of material that you have to remove just to get at other stuff. With a (believed) rocky core, you have 70-190km of ice that likely varies considerably in composition and concentration.
Even if you can get out there, even if you can mine it at -36F in direct sunlight, you're going to have a world of trouble doing it and may not even find a worthwhile concentration of materials you actually want, you may be processing ice and dust attempting to skim the rare earths and precious metals out of the dust.
Even if we do develop technology to mine asteroids (note that several of the companies that were attempting this in recent years have gone out of business or been acquired extremely cheaply) it's still a relatively short term solution. The asteroid belt only contains material equal to (roughly) 4% of the mass of the Moon.
That 4% mass of the Moon is spread out over mind boggling distances that doesn't even start untill roughly beyond the orbit of Mars. At those distances, PV power is going to be worthless, even at Mars the maximum solar irradiance is only about 59% of that on Earth so you're going to need to either build massive solar arrays and use wireless transmission to get the power down to the mining craft/drones (which will have to have considerable batteries in the event they get out of line of sight) or power them with some sort of nuclear solution.
Now, you'll be pulling a good deal of material off that you use purely for reaction mass. You'll also be pulling off a lot of stuff that won't really be worth sending back to Earth in any appreciable quantity like nickel and iron (although could be useful for construction in space and possibly worth sending to Mars) so when you do actually get to rare earths/precious metals you'll likely be able to mine more in a decade (if not a year) than earth has ever of say gold or platinum metal groups, but by even assuming you develop all the technology you need to do this, by the time you safely land it back on Earth it'll still be fantastically expensive to get to point of first delivery and a very very time consuming process purely due to the distances and practical limit on reaction mass for accelerating and decelerating.
Then you're still only talking 4% the mass of the Moon, if you were making a decent effort at mining the asteroids you might pull worthwhile material out for a century or two before you've exhausted the bulk of it and then it is "well, I hope we've developed FTL travel or generation ships!"