So, four a.m. again. At nine I go to a new doctor for a physical. No exercise at all this summer, totally unfit, belly out to here, and I need to tighten up my carbohydrate intake again; I haven’t been watching it, and I shudder to think what my A1C is going to be like. Hi, Doctor, pleased to meet you. Think I’ll grab some coffee from the darkened kitchen; no sense in showing up with a boring heart rate . . .
I don’t know what to memorialize about how the Brett Kavanaugh nomination for the Supreme Court is going. Caesar’s ghost. No. Fought that out elsewhere. As usual to no effect, but I cleared my spleen.
The rovers on Ryugu continue to be a success. So far we have only their pictures from the grim gray rockpile. Much of the real science will have to wait until the samples get back home.
The mechanics of Ryugu have been entertaining me as far as the prospect of mining asteroids.
Just so I don’t start with the possibility of a premise that I’m talking about something outright pointless: Some asteroids are mineable at least as far as content. It is presumed that the contents of some would really be worth it. Anything mined in space doesn’t mess with Earth’s environment in the process. And it will be an option if Earth resources grow hard to get, if we don’t get to it sooner.
Most of all, any materials mined in space are materials that won’t have to be very expensively muscled up out of Earth’s gravity into space if you want them in space, which becomes really significant if you can then refine them in space and manufacture things in space . . .
which, to be clear, then leads (can lead, could lead) to the ability to do Really Good Things In Space, like giant solar collectors or collecting helium-3 from Saturn and Uranus for thousands and thousands of years, thus cleanly sustaining high-level civilization over the Long Term, which is the Whole Point, etc. . . .
Okay, but - given all that:
Imagine mining Ryugu.
Or something of Ryugu’s size that we’ll call Ryugu. Presume Ryugu happens to contain something that you want.
What do you do?
To be cartoonish about it to start, a suited astronaut swinging a pick at Ryugu would accomplish departure from Ryugu.
If one of the rovers tried something like just abrading the surface of Ryugu, what they would accomplish is loss of contact with the surface of Ryugu without succeeding in scuffing the rock they were sitting on. (They can’t even roll on wheels.)
Really, EVERYTHING about space is easy-say hard-do.
A hard thing for Earth people to fully realize is that Earth gravity is a constantly running machine that helps our muscles, and machines, and even our minds do everything. (With minds I mean as in organization. A magical force helps things stay where they are put.) The machine is running on Mars. It’s running less on our Moon, but enough.
On the very biggest dwarf planet in the Mars-Jupiter asteroid belt, which is Ceres, gravity is down to three hundredths of a gee. The astronaut with the pick would neither leave Ceres (that would require moving at 1,800 kilometers per hour) or go into orbit (1,296 kilometers per hour), but, given that you could jump 36 times as high on Ceres as you can on Earth, and would take considerably longer about it, the astronaut is going to have a few fumbly difficulties interacting forcefully with the surface.
And the solar system is not full of Cereses. (Ceres takes up a quarter of its belt’s mass all by itself.) Millions of asteroids are smaller than Ryugu or not much larger.
I will speculate . . .
I think to mine something like Ryugu you’d have to . . . encompass it. Tie your spacecraft or mining facility to it - i.e., pass a cable all the way around it in a loop! Which is in principle not crazy; Ryugu is 2.9 kilometers in circumference.
Note: Passing cables in free fall or no gravity, which is very nearly what this is, is not easy. In our own orbit, astronauts have found this a very non-simple task. There’s a trace of down on Ryugu, but still.
(Also . . . Ryugu isn’t very round, and most asteroids aren’t round. Some of them really aren’t round. The original Hayabusa’s target Itokawa is peanut-shaped! You have to get toward the size of mighty Ceres before gravity starts really forcing you into ball shape. This will complicate things.)
Tighten the cable firmly. (We may be assuming throughout that the asteroid in question is mostly solid and is not a rubble pile that’s just drifted together. Which is a very large assumption. To the extent it’s wrong, things may work differently. Maybe with all of this.)
But that cable holds down only that one spacecraft/mining rig against the surface - and only holds it down according to the way the cable tension works.
So, the mining rig is able to happily dig a hole under itself. Well, still probably gingerly, but we assume it can. Down to the depth of its drill, the reach of its mechanical hands, whatever.
. . . Then what does it do? It has dug itself out of a job. It is hanging there with a hole underneath it.
So maybe it has used the aid of this big loop of cable to be able to hammer a spike into Ryugu that it can hang on to. It can then (mostly, barring a safety tether) release itself from the cable and proceed to, very carefully, keep hammering new spikes into Ryugu as it digs downward while still being held in place by the earlier spikes. Like a mountain climber doing the same thing while climbing a granite cliff face - except that the mountain climber is disappearing into the cliff face while also exerting enough force on the cliff face to chip a hole in it.
. . . Yes, keep an extensible tether attached to that cable loop, by all means.
I feel that the use of blasting directly underneath your clinging-to-crampons mining facility would probably be problematic.
Now, meanwhile, the rig isn’t doing this for fun. It’s collecting ore. It has to keep the ore somewhere. So I’m pretty sure that other units will be sent to Ryugu to attach themselves to the big cable loop. (I’m far from sure this will be easy in practice, but let that go.) It’s likely that Ryugu will end up with a continuous ring of human constructions on it. Collector containers. Maybe processing units? Definitely a dock for the spacecraft that will pick up the ore to take it away.
The other problem is a very big one.
The rig is digging a hole. The spoil, the stuff it doesn’t want, has to go somewhere. Where can it put it?
Ryugu, is where.
This is a nightmare.
With exquisite gentleness, the spoil must be slowly, SLOWLY, gently taken to somewhere on Ryugu that isn’t on the loop of cable and gently, gently put down there, and gradually piled there.
With so little surface area on Ryugu that you can’t afford to be piling it there.
I imagine you loop a second cable around Ryugu perpendicular to the first loop to help you (LET you! this is RYUGU!) at least move the stuff over there with some semblance of speed. Maybe this can work, except that you’ll soon be burying the cable. Again, you have no room.
(Unless this is a tiny, brief mining operation, and if this were a tiny, brief mining operation you wouldn’t be going to all this trouble!)
We will pass over lightly the possibility of putting all the spoil - so slowly, so gently - into orbit around Ryugu. With such low speeds, in such a tiny gravity field, I think there is very little orbital stability however you do it . . . any problems would become uncontrollable (with the slowness only adding to the anticipation) . . . and spacecraft have to be arriving and departing. Through that.
The best possibility may be that there is no spoil and it’s all ore, or it at any rate will have to be treated as ore. The visiting spacecraft will take it all away.
But, you know, to where?
To sorting and refining facilities in space.
Which would have the same problem. Because they’d have waste material to get rid of!
Unless you landed the stuff on a planet - landed it hard or soft, which may have all kinds of problems - and which would mean that you no longer have these materials in space. You’d have to launch the end products.
The two best possibilities, I think:
Ceres or some moons would be a good compromise for the refining facilities. Far lower gravity than full-blown planets (low enough that you may be able to launch things using accelerated ramps/catapults), and enough gravity to greatly simplify manufacturing work, and they’re big enough that the short-term solution of piling up waste won’t catch up with them for some time. Ceres has nearly three million square kilometers of surface area.
. . . Except that even on Ceres - well, Ceres has no atmosphere. So you can’t exactly parachute anything down. So it’s either hard landings or using a lot of propellant to land mass-intensive loads.
A big expensive hollow facility in space that would enclose the deliveries throughout processing. Now and then it fires big loads of waste material outward at high speed using an acceleration ramp - which also means it accelerates itself in the other direction, now and then changing course whenever it gets rid of mass. (So a big solidly built hollow facility, to take the strain safely.) Then the answer to where the spoil/waste goes is Somewhere Else, somewhere in the solar system, details to be worked out later.
(You could not just do this on/from Ryugu . . . I think. You’d be changing the orbit of the asteroid, which would not be a disaster but would be cumbersome to manage - and you’d be putting very acute shocks and strain on a possibly not completely solid body that you happen to be digging into, which might very well be a disaster.)
But then none of this would be.
Especially at first - when you do not have space-mined space-refined space-manufactured things yet. The snake biting its tail, and hanging on.
I have no good ending sentence. It’s just that I was thinking about the confident talk about mining asteroids, entrepreneurship, all that. Nothing to it. (Like the line in The War of the Worlds: “We shall peck them to death tomorrow, my dear.”) None of that stuff (the stuff I haven’t even mentioned!) is out-of-the-box.
And the basic situation . . . it’s always pictured as being simpler than I think it is.
Ryugu is difficult to even touch.
Last updated October 01, 2018