Hacker News Reader

Comment by ChuckMcM | Hacker News Reader

Pretty neat. This would certainly make for an interesting Mars mission should SpaceX want to try it, land a lander, have the lander process regolith into iron chunks, create a pile of chunks. All good threshold goals.

What ever happened the asteroid mining folks? They have a similar problem, albeit with very little gravity and no atmosphere, but their metals are in theory worth a lot more (platinum, gold, silver, Etc.)

There was a similar idea/proposal for extracting aluminum from Lunar regolith, also a good space mission for private interests.

Once you've got basic metals you can make more interesting things, with iron you can make reinforced concrete which would be an interesting building material on Mars I suspect.

View on HN

Asteroids are hit-and-miss composition wise (though you can determine quite a bit by observing them), but when they are a hit they tend to be really valuable. The problem then is that you need to get to them and then the next problem is that you need to get back to where you came from.

Both of these can hurt your ROI considerably assuming you can solve for them at all with the masses involved. They're also usually moving at a pretty good clip and are bad to set up long term for. I think until we have a long term presence in the asteroid belt that this is mostly going to be SF rather than that it will actually happen.

delta-V happened to asteroid folks.

there are no realistic proposals for asteroid drives ala https://en.wikipedia.org/wiki/K240

The product I have in mind is solar sails to be delivered to the Earth-Sun L1 point to counteract climate change. A carbonaceous chondrite asteroid is rich in volatiles to make plastic films as well as metals and stones to coat them with. The pros are:

- solar sails transport themselves without using reaction mass

- you're not competing with cheap resources on Earth to be used on Earth, rather resources from Earth transported past LEO

eliminating many of the fundamental objections to scenarios where ISRU materials get transported somewhere.

Cons are:

- a good sunshade and a good solar sail are different things

- plastic + metal solar sails seem to get corroded badly over time

- if you think the turnaround time between Earth and Mars is bad, you are talking half a decade or more to round trip parts plus a 45 minute communication delay at some times; you either need to send people with all the problems that entails or have advanced autonomy and a manned simulation platform somewhere in near-Earth or cislunar space.

I've got a good picture of what parts of the "head end" that consumes asteroid materials and turns them into reasonable chemical feedstocks looks like with the exception of how to devolatize the asteroid to begin with and where to get the storage tanks to store early offgassing before the metals line comes online. (Storage tanks are an interesting question for manufacturing since the chemical factory needs plenty of them.) I also have some idea of what the "shipyard" that builds the actual sails look like. Trouble is you probably need a Drexler machine to make spare parts and also make customized parts given that you don't really know what you're up against when it comes to the "head end" (though upper pyramid parts of the chemical factory and the shipyard can be simulated close to Earth) ... and Drexler's concept for a Drexler machine doesn't work.

If you so very want some mylar over carbon fiber put up in L1, and not ever launch that from Earth then Luna is the most obviously cheap and abundant source of whatever. No need for asteroids at all. Also the comms delay is 1.25s IIRC.

I personally consider this a folly.

On the other hand, no comprehensive survey of Luna was ever done, and we target Mars or even asteroids why? I'd like some at least plausible reason for this.

It is true that Luna is halfway to Mars in dV on hohmanns. But not in time spent. Never will be.

Luna has the aluminum but probably not the stuff to make mylar or kapton or something similar. You need CHN (Carbon, Hydrogen, Nitrogen) for that.

On the other hand, O'Neill's students did think a bit about how to make metal films without any plastic backing and that might be (1) practical w/ Lunar materials assuming you can get the mass driver, catcher and all of that working, and (2) produce a very high performance sail if it survives the corrosive space environment, metal-Kapton sails didn't do that well here

https://en.wikipedia.org/wiki/IKAROS

> to counteract climate change

Seems way easier to get our act together on earth. It's all solved from a technological angle.

the economic angle far outweigh the technological angle.

And the political/religious angle, don't forget that one. Hate against "woke" goes deep, gotta drive that diesel F150 cause that's our patriotic identity!!1 /s

The economic angle argument backfires though in this thread's context. If fixing a little bit of behavior down here is too expensive then it surely is prohibitively expensive to attempt all that on a different planet. Everybody not seeing this as obvious has watched too much scifi.

Uhh... Why? Getting stuff from an asteroid orbit to Earth needs a delta-v of around 1 km/s. You can even get to circularize the orbit if you're comfortable with doing a couple of gravitational assists.

You won't be moving the whole asteroids, but a few hundred tons of extracted platinum-group metals? Certainly doable.

Apropos of nothing, was the PC version/successor Fragile Allegiance as good/better than K240?

It's mostly same gameplay-wise. Fancier graphics, clunkier interface. K240 under Amiga emulator ran way better than original FA under dosbox until GOG or someone released pre-dosbox-ed version. This runs fine if you want to try.

Why can't you just use a mass driver? Just mine bits of the asteroid and fling them. The biggest problem would be fueling this, and nuclear is probably quite cost effective. (Shout out to KSR's fantastic mars trilogy for this idea.)

Sure, this would be slow. But I think it'd be viable. You could move them into earth's orbit or even slam it into the moon.

A mass driver would run off a capacitor bank most likely - can't you just charge that by a solar array ? Unless you really need to send huge amounts, this should be much less hassle than lugging a nuclear reactor around. And for near-Earth asteroids, you should get the same power per square meter, but better (no atmosphere & clouds to get in the way) at least half of the time (considering the asteroid rotates - and even that could be handled by clever engineering/tethered array).

> There was a similar idea/proposal for extracting aluminum from Lunar regolith, also a good space mission for private interests.

With the asteroids, I assume the idea is to bring enough platinum and gold back to Earth to offset the costs of getting them from space. That doesn't sound especially realistic, but in the right circumstances I guess it could be.

With aluminum on the moon or iron on Mars, that will never happen. You'd have to want to use those materials on location.

So what would the value be of producing aluminum on the moon?

> So what would the value be of producing aluminum on the moon?

Building more rockets? Interesting detail: there isn't enough oxygen there to cause aluminum to immediately be covered with a skin of aluminum oxide. I wonder what the energy cost of an extraction process for aluminum on the moon would be. At the same time I would hate to see the moon mined, that's one piece of common property that we should maybe try to preserve unless we have no other alternative, not just for commerce.

The idea you see in O'Neill and other science fiction that iron is rare on the moon is bunk. There is Hematite

https://www.jpl.nasa.gov/news/the-moon-is-rusting-and-resear...

and Apollo astronauts brought back perfectly good Iron ore. It's true that there is lot of aluminum and titanium on the moon and a lunar economy might use that but there is enough iron that if loonies wanted to make things out of iron they could make things out of iron.

Yes, absolutely, but they specifically asked about aluminum. Mining iron or aluminum on the moon would be trivial compared to earth in terms of access. Getting the gear there to bootstrap it all would be an interesting technical problem but I think it is solvable. Why you would want to do it to me is only to jump start a deep space program taking advantage of the reduced requirements to reach escape velocity while still having a long term platform to build on. If you want to do better than that then space construction will have to go to a completely different level first.

ISRU tends to make no sense at all when you have to move things from place to place, it makes more sense when you use them in place.

For instance there may be some usable ice at the moon's poles maybe even some carbon. You could get oxygen out of rocks one way or another. You could make rocket fuel and launch stuff the conventional way but there are two problems: (1) Earth is the most competitive and cheapest market for everything in the solar system, and (2) lunar colonists might see volatiles as precious and decide to circularize them rather than expend them. [1] [2] Contrast that to Earth which has plenty of volatiles.

There is the idea of O'Neill and Heinlein [1] of the lunar mass driver, the picture you get from The High Frontier and The Moon is a Harsh Mistress that it looks like a maglev train a few km long is totally wrong because your elevation angle is pretty high if you want to target the Earth-Moon L1 point or the Earth or LEO (assuming you can aerobrake reliably) If it is a few km long it is a slanted hole a few km deep. I don't know about coilguns but a railgun with 2.5 km/s that would fit on a ship has been tested [3] and you need 3.5 km/s to get to L1 -- one way or another I think a viable mass driver looks like the Paris Gun and shoots small payloads. If you could launch a 1kg payload per second you could put up a rail car worth of material in a day.

O'Neill's students thought a lot about the "catcher" for stuff from the lunar mass driver and never came up with anything convincing if anybody else has I haven't seen it.

[1] See The Moon is a Harsh Mistress

[2] Niven's Protector talks about the problem of very long-term space colonies , starships and stuff losing volatiles at steady rate no matter how well you try to keep them in.

[3] ... and burns up the barrels

Fascinating stuff, thank you for the comment. I always wonder to what degree the various 'hard SF' authors really run the numbers, some are very good at it, good enough that there are no immediately obvious mistakes, others get stuff glaringly wrong but still spin a good yarn.

> ... your elevation angle is pretty high if you want to target the Earth-Moon L1 point or the Earth or LEO...

You don't point at where you want to go. You point retrograde (relative to the moon's orbit) so that, after escaping the moon, the payload is just past the apogee of a transfer orbit with the desired perigee.

Further, the moon isn't a flat disk, with the Earth "up"; getting the required angle is just a matter of choosing the right place on the surface of the moon (a sphere has multiple tangents pointing in any direction you want).

So no, you wouldn't need "a slanted hole a few km deep".

You may be right but I'd want to see the trajectories numerically integrated and plotted. What I know is that trajectories that hit the L1 point with low velocity will confound your intuition that comes from conics. Here is a recent analysis that considers a range of trajectories launched from a certain point

https://www.sjsu.edu/ae/docs/project-thesis/Ethan.Miller-Su2...

which a student project that has a lot of problems and doesn't consider the possibility of relocating the driver but they are considering moderately high angles of around 30 degrees. Their mass driver is about 500m long in the range that if you want to drill a hole that deep you can drill a hole that deep.

Practically there are other concerns about a moon base, particularly these days people are interested in polar locations. You could possibly run 1000 km of maglev to get to the base of the thing but if you are talking that big you might consider a lunar beanstalk which at least doesn't require a catcher at L1.

A lunar beanstalk? How is that supposed to work? (Answer: it won't; Lunar-stationary orbits do not exist, since they would have a radius on the order of the Earth-moon distance, and the Earth is much more massive than the moon).

https://explainingscience.org/2025/08/19/lunar-stationary-or...

Iron may not be rare but the value of iron ores is subtly dependent on eg, non-iron content

"A few smelting companies formed in the late 19th and early 20th centuries, but were unable to process the ore with any economic success due to the sandy nature and high titanium content, which tended to form hard, brittle carbides in the steel." https://en.wikipedia.org/wiki/Ironsand#:~:text=%5D%20A%20few...

Even today's "economic" process wastes all that titanium (which should be even more valuable for a lunar economy - Ti burning is a major thorn on earth!)

Why preserve the current landscape of the moon? It harbors no life, and its surface is scarred by billions years of space collisions.

Because it is a historical record that we are able to read better and better and I think that the moon's usefulness as a historical record is unique and as a resource for basic building materials it is far less so.

With this framing, is there ever a situation in which it would be okay to utilize the moon's material? It's not like the moon has feelings, and exploiting a bunch of lifeless rock seems better than doing it on Earth, no?

IMO we've ruined the sky already. We can't see all the stars we used to, and new ones (starlink) are visible to the unaided eye. Changing the face of the moon such that it, too, is no longer the same symbol every human has ever seen, feels like a monumental step we maybe shouldn't take. I don't want to see the twinkle of a refinery, any more than I'd want to see a giant McDonald's logo carved into it.

24/7 solar furnaces harvesting asteroids seems like a huge industry once it's figured out. The big problem is that it would take a billionaire to make it happen.

Reply on news.ycombinator.com