A metallurgist's doubts about self-replicating probes • Hacker News Board

Re: A metallurgist's doubts about self-replicating probes

#31

Post by red75prime » Tue, Jul 14, 2026, 5:02 PM UTC

simiones wrote: post #28

marcosdumay wrote: post #27

Yes, we don't know how to make a half-ton replicating probe right now. No, none of the arguments on the article have any implication on the possibility of such a probe. None at all. There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe ri…

I hate this assumption that many sci-fi enthusiasts seem to make, that as long as something is not ruled out by currently known physics rules, it doesn't matter that we have no idea how it could be built, there will be some way in some plausible future. When we see currently insurmountable problems in creating a piece of technology, it's absolutely possible that we'll never be able to build it. Even if it is theoreti…

> there is no reason to believe that the way to build it would be found before, say, the sun runs out of hydrogen.

A lot of computational power can be thrown at the problem in this time. So, the problem should admits no shortcuts, no decomposition into simpler problems, no alternative ways to get similar functionality that allow shotrcuts or decomposition. The result should look like a jumble of atoms that somehow produces the required functionality.

I wonder which problems can admit only this kind of a solution.

Re: A metallurgist's doubts about self-replicating probes

#32

Post by pfortuny » Tue, Jul 14, 2026, 5:09 PM UTC

marcosdumay wrote: post #27

Yes, we don't know how to make a half-ton replicating probe right now. No, none of the arguments on the article have any implication on the possibility of such a probe. None at all. There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe ri…

The self-replication assumes also that there is enough energy stored in each planet (or coming from a Sun) to do the work... That is pretty much unlikely.

Re: A metallurgist's doubts about self-replicating probes

#33

Post by PaulHoule » Tue, Jul 14, 2026, 5:10 PM UTC

CC asteroids have hydrogen, oxygen and carbon and with chemistry a bit like

https://www.dakotagas.com/

that is, CC asteroid contain “coal” more or less.

I don’t see a problem with drawing flowsheets for metals like iron, stones like silicon and even BTX chemicals to produce plastics. You cycle syngas and treat resulting H2O and CO2 as precious.

Now I was not thinking of a 500kg “seed” but a factory factory that is packed up in 100 ton loads that builds a sunshade factory by a process like building a ship inside a bottle except inside out.

I did worry about how you handle devolatization at the beginning, like it is precious and maybe even dangerous and it would be real nice to do it all at the beginning but you don’t have the storage tank factory online (thought a lot about storage tanks!)

The plan was to do all this in our solar system to sail sunshades to the Earth-Sun L1 point, the big questions I had was “how do you fix problems when it is hands-off that far away?” (physical twin in cislunar space for one thing!) vs “do you send people who you have to keep alive? can you bring them back? do they turn into Zeons?”

I have thought about the Drexler problem when it comes to Mars colonization and can’t think of a better answer than a synthetic biology platform based on bacteria and possibly yeast which can do versatile if not efficient chemical synthesis from syngas or photosynthesis. You still need flow chemistry, 3-d printing and some more methodologies but the project of “advanced manufacturing” that would enable a small settlement to achieve autakry seems achievable to me and would be essential for interplanetary colonization and helpful in case of forced degrowth.

Re: A metallurgist's doubts about self-replicating probes

#34

Post by JohnMakin » Tue, Jul 14, 2026, 5:19 PM UTC

credit_guy wrote: post #13

JohnMakin wrote: post #7

Earlier quoted context omitted.

300 years ago people also believed alchemy was a serious field of study

That is true. What should we conclude from this statement?

That you shouldn’t assume just because in the past ideas have existed that became reality, that all current ideas are feasible or possible?

Re: A metallurgist's doubts about self-replicating probes

#35

Post by EA-3167 » Tue, Jul 14, 2026, 5:23 PM UTC

abecedarius wrote: post #30

EA-3167 wrote: post #25

Earlier quoted context omitted.

Life as we know it relies on a complex and interdependent ecosystem, and complex life relies on countless other organisms to support us. Without plants we absolutely couldn’t survive, without microorganisms we can’t survive. Without ample supplies of food, water and oxygen we can’t function. Generally speaking the pace of biological activity is a lot slower than industrial ones too. We might make up for the pace with…

> complex and interdependent ecosystem That's why my other comment pointed to the autotrophs with the simplest requirements, and the (unknown but complexity-bounded) origin of life. > pace of biological activity is a lot slower than industrial ones Bacterial replication times can be under an hour.

You’re absolutely right about how quickly some bacteria can replicate, but that depends on the proper substrate, ambient conditions, availability of nutrients, and any competition from contaminants.

What something like E. Coli can do in a well bioreactor is the ideal case, and even then most of what they produce is the bacteria themselves. On Earth this isn’t a problem at all, but as a means of husbanding every joule because you don’t know when or where the next one is coming from, I think it might matter.

It’s also probably a genuinely hard problem keeping your organisms viable without a constant supply of food, a means to get rid of mutants, or some hitherto unknown means of preservation that could handle the extreme time spans involved between “awakenings”.

Re: A metallurgist's doubts about self-replicating probes

#36

Post by Diogenesian » Tue, Jul 14, 2026, 5:30 PM UTC

seiferteric wrote: post #9

Wouldn't a counter this argument be biological systems? These are reasonable points as long as we are talking about current methods, but I assume if we were to get to the point of self replicating probes it would be done by something like nanotechnology, synthetic biology like systems.

Why would biological systems be a counterargument? Smelting metals and sustaining life both require an enormous amount of water and about ~1ATM of atmosphere, as far as we know, and there's no plausible known mechanism for sidestepping this requirement. So "magical synthetic biology that can self-replicate in space" is actually a worse solution to the problem than "magical metallurgy that can be done in space" since humans at least have smelted metals, but we've never built synthetic forms of life. (Not counting CRISPR)

Re: A metallurgist's doubts about self-replicating probes

#37

Post by alwa » Tue, Jul 14, 2026, 5:35 PM UTC

pfortuny wrote: post #32

marcosdumay wrote: post #27

Yes, we don't know how to make a half-ton replicating probe right now. No, none of the arguments on the article have any implication on the possibility of such a probe. None at all. There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe ri…

The self-replication assumes also that there is enough energy stored in each planet (or coming from a Sun) to do the work... That is pretty much unlikely.

And stored in the specific forms the machine can exploit.

Over a long enough timescale, though… really, really slow solar trickle charge to a space-capacitor bank? A thousand years’ suns, culminating in a glorious orgy of smelting?

Re: A metallurgist's doubts about self-replicating probes

#38

Post by snowwrestler » Tue, Jul 14, 2026, 5:36 PM UTC

credit_guy wrote: post #6

> Shrinking that into a 500 kg seed — or even Freitas’ original 100-ton seed — is not an engineering detail. It may be the entire problem. How many AI tells can you count there? But honestly (see what I did there?) the AI slop is reasonably cleaned up in this piece. However, the essence of the argument has two deep flaws. One is that the time to complete an interstellar voyage is extremely long and you need some exer…

It’s a bit silly to be so sensitive to “AI tells” in phrasing. If you go look for them in original human writing, you are guaranteed to find them—just like the AI training did! That’s how they became “tells” in the first place.

Re: A metallurgist's doubts about self-replicating probes

#39

Post by Windchaser » Tue, Jul 14, 2026, 5:39 PM UTC

andrewflnr wrote: post #19

seiferteric wrote: post #9

Wouldn't a counter this argument be biological systems? These are reasonable points as long as we are talking about current methods, but I assume if we were to get to the point of self replicating probes it would be done by something like nanotechnology, synthetic biology like systems.

Somewhat famously with life, you aren't necessarily replicating the same thing at the end as you are at the beginning, which is an awkward property for an engineered system.

So that adds some extra "benefits" (mutation and natural selection improves the probes over time) along with some extra difficulties - how do you keep the self-reproducing probes "on-task" from one generation to the next? How do you instill "explore and report home" as an innate goal to a mutating system?

Re: A metallurgist's doubts about self-replicating probes

#40

Post by Animats » Tue, Jul 14, 2026, 5:42 PM UTC

zeryx wrote: post #2

I studied material science in school specifically to try and address his concerns. Unfortunately they are all quite valid - the hard part isn't manufacturing, extruding, printing. Those are actually all quite reasonable (albeit not super space or weight efficient). The hard part is refining and ore enrichment, and most techniques that could possibly work in microgravity are almost impossible to test on earth. You wou…

> Every terrestrial concentration process relies on things an asteroid lacks: gravity-driven sedimentation, water-based flotation, density separation in fluids, atmospheric combustion.

That's a good point. Most bulk industrial processes won't work in zero G. This limits asteroid mining. Breaking off pieces of rock and accelerating them to somewhere, maybe. Building a big wheel and spinning it up to get some gravity, maybe. Materials processing in open space, not so much.

The "seed" to start up an industrial economy might be the size of the industrial base of, say, Israel or North Korea, both of which try to be self-sufficient. We get to find out when someone tries to do something self-sustaining on Luna or Mars.