alt.hn

7/13/2026 at 4:11:20 AM

A metallurgist's doubts about self-replicating probes

 https://www.centauri-dreams.org/2026/07/10/a-metallurgists-doubts-about-self-replicating-probes/

by EA-3167

7/13/2026 at 11:44:17 AM

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 would certainly need vitamins for electronics components for a time. Even much older computer chip architectures (1990s level) still require the clean room and 20-30 stages of prep. I believe an orbital chip fab is not only possible but, kind of ideal? Keeping it clean would be within reach - and it's mostly if not entirely an autonomous process from silicon monocrystal to assembled part today.

We're along way from self replicating probes. But I would argue were quite capable of autonomous mining, manufacturing and material transport - assuming we can figure out how to refine effectively. If someone wants a cool PhD project and ship an experiment to the ISS, I would argue an ionic or plasma based refining technique designed for micro gravity could be very interesting and very useful

by zeryx

7/14/2026 at 5:42:33 PM

> 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.

by Animats

7/14/2026 at 7:58:17 PM

"Israel or North Korea, both of which try to be self-sufficient" - Neither of them do any such thing though. From a quick search Israel imports about 80% of their calories though they also export some food they are heavily reliant on imported grains and meat. North Korea is obviously harder to get information on but it imports large amounts of food from China.

by neaden

7/15/2026 at 11:35:52 AM

North Korea has an official ideology of "Juche", and "The goal of Juche is to establish a self-reliant state" (1)

It may not be like that in practice. But nevertheless, self-reliance is in their stated goals, and North Korea is one of the least "open" states in the world.

I think you can make the case that they "try to be self-sufficient". They do try.

As for Israel, eh, it depends. They certainly don't rely on neighbouring countries.

1) https://en.wikipedia.org/wiki/Juche#Core_principles

by SideburnsOfDoom

7/15/2026 at 6:34:34 PM

Sure North Korea tries, but they don't succeed so it's not really helpful as an example of a self sufficient society to base a space colony off of. As for Israel yeah, they mostly don't import food from their neighbors (most of whom also import the majority of their food calories) but I don't see what that has to do with anything, as I said they import 80% of their calories which is certainly not tenable for a space colony to do.

by neaden

7/14/2026 at 8:20:11 PM

Both North Korea and Israel are notable (compared to space) for their dense oxygen rich atmospheres, accessible large reservoirs of water, access to solvents/lubricants, and a generally "shirt sleeves" environment for workers. Asteroids, the Moon, and deep space don't really have these things. So you're not just bootstrapping an industrial facility at those locations but all the basic infrastructure that industry requires to exist.

With space manufacturing the first widget out of a factory costs trillions of dollars. There's also few if any raw materials that are far more abundant in space than here on Earth (at orders of magnitude smaller cost).

by giantrobot

7/14/2026 at 3:47:10 PM

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.

by seiferteric

7/14/2026 at 5:30:54 PM

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)

by Diogenesian

7/14/2026 at 8:53:36 PM

You're making assumptions that the parent isn't necessarily making. Imagine sending humans to other earthlike planets on hypothetical generation ships. Those humans could throw away their technology and rebuild from zero over thousands of years to send more spaceships of humans to yet further planets. Presto, an example of self-replicating biological von Neumann systems.

by AlotOfReading

7/14/2026 at 11:52:31 PM

It's important to say that isn't self-replicating in the von Neumann sense, even setting aside the question of how it's being executed. Humans don't replicate, we reproduce and critically evolve, never more quickly or drastically then when we're introduced to a new environment with new selection pressures. Unless these future humans have the technology to avoid that natural drift then they won't be a probe for the original species in any sense, they will speciate. In fact if you send people on a one-way trip to start over from scratch, I think it's pretty extreme to imagine their nth descendants caring about the goals of the parent civilization. Even if they in turn become spacefaring it's not as though they'll act as "probes" for their ancient and probably forgotten ancestors.

by EA-3167

7/15/2026 at 12:08:10 AM

There are decades old papers [0] on this subject that explicitly use humans as a analogy and call it "reproduction" because of the need to learn or evolve for local conditions. I don't think using terms in a way they've been used since the first serious analysis of the concept is going to confuse anyone.

    I think it's pretty extreme to imagine their nth descendants caring about the goals of the parent civilization.
It's an example to demonstrate the concept in familiar terms, not a psychohistorical prediction.

[0] https://www.rfreitas.com/Astro/ReproJBISJuly1980.htm

by AlotOfReading

7/14/2026 at 4:25:53 PM

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.

by andrewflnr

7/14/2026 at 5:39:42 PM

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?

by Windchaser

7/14/2026 at 6:51:20 PM

I would argue that, over the time scales at which Von Neumann probes would hypothetically spread, “report home” may be a useless or even wasteful requirement. Even if somebody were still around to hear the message, what is the likelihood that they would still be listening? Or be able to interpret it?

by bunderbunder

7/14/2026 at 9:06:55 PM

If we build self-replicating machines and send them out into the universe we're really just sending out our evolutionary progeny. Hopefully they would remember us fondly.

by EvanAnderson

7/14/2026 at 5:54:53 PM

I'd argue all self-replicating systems subject to entropy (i.e. existing in the physical world) are automatically subject to mutation and natural selection and, therefore, alive and able to evolve around any innate goals or constraints. If the inmate goal isn't tied to a highly-conserved phenotype I would think the goal would disappear as mutations accumulate and natural selection takes its toll.

by EvanAnderson

7/14/2026 at 10:50:40 PM

> how do you keep the self-reproducing probes "on-task" from one generation to the next?

This is, indeed, the exact question one must ask before attempting to build and launch biological Von Neumann probes.

by andrewflnr

7/14/2026 at 11:27:16 PM

Judging by our behavior on the current rock we're on, don't give them the choice. Humanity has been around for a long time. In that time, I don't believe I've ever heard discussion of changing the direction the Sun and Earth are headed. If there were something deep inside the Earth, or another planet that would activate in another 10,000 years that would do the phone home step, we still don't know about it. So while we're hypothesizing about sci-fi Von Neumann probes, just scale the entire thing up to the size of a solar system and send that off in the right direction. Collect all the mass in our system that isn't Sol, Terra, (and Luna), and build a rogue planet with an underground civilization, and then don't give them engines. Unless the civilization on the planet advances too the point that they can create engines, decide they don't want to go where you've sent them, voila, generational ship. Just bury a computer deep I side the rogue planet's core that activates once it reaches the destination.

by fragmede

7/14/2026 at 5:56:33 PM

> 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.

Biological systems require extremely specific environments that aren't space.

Yeah, you can self-replicate (well, not exactly self-replicate), but just think of all the "infrastructure" you need to do that: massive volumes of air and water, all kinds of weird chemicals not found in minerals, a whole biosphere of other stuff, a literal star, etc. And none of that infrastructure is really space-worthy on any reasonable scale for a probe.

If you broke it all down, I bet you'd need a mass/volume at least as big as a more technological probe. And you still need the technological infrastructure to build a vessel to hold it all together.

by palmotea

7/14/2026 at 4:35:00 PM

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

by abecedarius

7/14/2026 at 4:38:28 PM

The thing is, while the universe is full of metals, it's not that full of the materials needed to sustain life (as we know it, at least). You can find metals and other inorganic compounds on virtually every asteroid, moon, and planet, and many comets even. But water and nitrogen and carbon are significantly rarer.

Plus, life can't survive more than a few minutes in space without metal encasings and electronic life support; whereas metal alone only requires life at a much longer time scale. So, while it may be possible to build a fully inorganic self-replicating fleet, it's certainly impossible to build a fully-organic one with any technology or chemistry we know about today at least.

by simiones

7/14/2026 at 4:44:59 PM

In the outer solar system organics and water are abundant (and in the inner there are plenty of carbonaceous chondrites, admittedly not the most generic inner-system bodies).

Agreed that metals should unlock wider opportunities in the inner system where solar energy is more abundant. I just don't think it matters much, you need a good place to plant your seed; once you've built up to scale you can then build wherever.

(False that life dies in minutes in space; plus the engineers can invest in even greater error correction than radiodurans.)

by abecedarius

7/15/2026 at 3:05:30 PM

> (False that life dies in minutes in space; plus the engineers can invest in even greater error correction than radiodurans.)

What form of life can actually survive (that is, continue living, not just go into some dormant state from which it can later resurrect like a tardigrade) in space for more than a few minutes?

by simiones

7/14/2026 at 6:55:16 PM

Actually the other way around:

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

There's tons of Carbon, Nitrogen and Oxygen in the universe, but very little metals. Heavier elements are much rarer.

by torginus

7/15/2026 at 3:03:53 PM

Not in rocky bodies, except maybe for Oxygen (which is commonly found in the form of oxides, very rarely as a gas). Carbon and Nitrogen and Hydrogen and similar elements are mostly found in gas clouds and star that are not really conducive to any form of life or even really fit for extraction by a probe. Maybe some gas giants could be targets for a process of this kind?

by simiones

7/14/2026 at 6:37:44 PM

Carbon does not beat metal structurally. Some organic polymers are competitive in tensile strength. In flexural strength and fracture toughness, alloys continue to rule. And when carbon materials are competitive in strength and toughness, they tend to be highly temperature-sensitive and have sudden failure modes, which is not great for operating in space. Consider e.g. the Titan submarine that failed due to carbon fiber composite fatigue.

by scythe

7/14/2026 at 4:42:57 PM

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 scale, but then you’re back to the hard problem of dependencies and “fuel”.

I’m not sure that the problem of beneficiation changes because the system is biological rather than industrial. Edit: Without carrying whole ecosystems with the probe at least.

by EA-3167

7/14/2026 at 5:01:47 PM

> 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.

by abecedarius

7/14/2026 at 5:23:40 PM

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”.

by EA-3167

7/14/2026 at 6:52:40 PM

Mainly my point there is that it doesn't seem reasonable to anchor advanced nanotechnology on the doubling times we're used to for industry. I don't want to guess just what to expect for early construction from a starseed arriving at e.g. an outer-solar-system carbon-rich moon -- but nothing like a human generation.

by abecedarius

7/14/2026 at 6:32:50 PM

Biology ignored some of the most abundant elements because they can't be worked with under the constrained temperature and pressure conditions where biological systems operate. Biology barely uses any silicon, even though it is the second-most common element in the biosphere. Biology does not use aluminum, the third-most common element, at all. Biology does use iron but cannot reduce it to the pure metal. In fact, biological systems produce no metals. Structurally, biology relies on weak minerals like calcium carbonate and calcium phosphate, rather than much stronger ones like quartz and alumina, because of the difficulty of biochemical processing.

This isn't insurmountable for a probe. Biology can get stuck in local optima. Humans have the Periodic Table and quantum mechanics. But it means we are on untrodden ground. Refining titanium, today, uses a massive molybdenum-lined reactor operating at 1600 C (2900 F). The alternative processes (FFC and Chinuka) use liquid calcium chloride, mp 773 C. The square-cube law points to enormous energy losses trying to scale these processes down. And that's just one element.

by scythe

7/14/2026 at 9:15:59 PM

> In fact, biological systems produce no metals

I'm going to be very pedantic and point out a counterexample: https://en.wikipedia.org/wiki/Scaly-foot_gastropod

by pavel_lishin

7/14/2026 at 9:37:18 PM

Is greigite a metal? It is definitely a more interesting mineral, I'll give you that.

by scythe

7/14/2026 at 3:54:07 PM

We are selfreplicating bots - can eat anything, self healing minor damage, very agile, autonomous. When we stop growing numbers the harvest will begin

by artemonster

7/14/2026 at 4:14:33 PM

> When we stop growing numbers the harvest will begin

I like this part. It gives me chills.

by pjio

7/14/2026 at 4:10:50 PM

thats what i meant.

by seiferteric

7/14/2026 at 4:14:39 PM

... but traveling for months, years, decades and millennia in space away from earth has proven difficult so far. Even astronauts in space for a year had significant changes afterwards.

by golem14

7/14/2026 at 4:45:48 PM

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 right now.

by marcosdumay

7/14/2026 at 5:09:02 PM

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.

by pfortuny

7/14/2026 at 5:35:29 PM

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?

by alwa

7/14/2026 at 6:40:52 PM

Unless the capacitor breaks down before it's charged, one of the main problems discussed in the article.

by M95D

7/14/2026 at 8:19:15 PM

Any chemical bond is a potential source of energy. Plenty of sources of potential energy too able to be converted to work.

by asdff

7/14/2026 at 9:28:04 PM

That's the source, but for chemical reactions you also need a sink. For instance gasoline is not usable as an energy source without an oxidant. Take away the oxygen in Earth's atmosphere (an asteroid has no atmosphere at all) and now gasoline has no potential energy available. Asteroids have no available oxidants (regolith was already fully oxidized long ago).

by saulpw

7/14/2026 at 10:59:26 PM

If it has been oxidized, there's your oxygen source.

by asdff

7/15/2026 at 1:39:44 AM

It takes more energy to liberate the oxygen than you could ever get from the fuel. You don't need oxygen atoms, you need the oxidant.

by saulpw

7/15/2026 at 11:39:19 AM

As long as you can get an exogenous reaction from it, which is not guaranteed at all.

by pfortuny

7/14/2026 at 6:25:28 PM

I would also think that self-replicating probes would work more like living things. He seems to be imagining that we make probes like modern machines, and then find ways to let them build themselves. But nature found much easier solutions.

by qnleigh

7/14/2026 at 6:37:02 PM

Life as we know it until now has big difficulties outside goldilocks zone. It would theoretically be possible to make microbes (or fish?) that float high in Venus atmosphere, if we put money into 200 years of research, but no way life as we know it could ever break up and "eat" an asteroid.

by M95D

7/14/2026 at 7:29:15 PM

Never say never

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

by asdff

7/14/2026 at 9:23:03 PM

Very interesting. I didn't know about them.

But I still think it's impossible on an asteroid. No nitrogen, very little sunlight, wrong temperature, zero pressure, etc. They are already at their limit on Earth.

by M95D

7/14/2026 at 4:50:40 PM

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

by simiones

7/14/2026 at 6:21:24 PM

This isn't elaborated on in the piece, but it does mention that it's written in the context of the Fermi paradox. Adding 50,000 years of technological development and a 1,000 year rebooting phase at each star system doesn't meaningfully change how long it would take life to spread when considered against the 13,500,000,000 years since stars developed.

by pushcx

7/15/2026 at 3:07:00 PM

Why 50,000 years of technological development and not 50 billion?

by simiones

7/15/2026 at 5:50:13 PM

I timed it a few times.

by pushcx

7/14/2026 at 5:00:22 PM

It's absolutely possible that we'll never be able to build it.

There's absolutely no evidence of that on the article.

by marcosdumay

7/14/2026 at 6:38:52 PM

Of course not. That isn’t what the article was trying to say.

The thesis was, “I would like to suggest that the hardest part is the one that gets a single sentence: ‘mines local material and builds a copy.’” And so naturally the points in the article are only trying to support that point.

The closest we get to what this thread is talking about is the concluding remark on the Fermi paradox. Which doesn’t rest on the idea that it’s a practical impossibility; just on the suggestion that it may be hard enough that we can’t just assume civilizations that are in principle capable of building them are likely to actually do it.

by bunderbunder

7/14/2026 at 6:56:16 PM

> There's absolutely no evidence of that on the article.

If you treat evidence as in the law of excluded middle, then yes. But if you are ready for a probabilistic evidence, then the article is a piece of evidence.

It chains Fermi Paradox, and our lack of knowledge how to do metallurgy in space. They both combined raise probability of impossibility of Von Neumann probes. It is not a proof that rules out Von Neumann probes, but it raises doubts about them.

by ordu

7/14/2026 at 5:02:19 PM

> 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.

by red75prime

7/15/2026 at 2:57:29 PM

> A lot of computational power can be thrown at the problem in this time.

We know plenty of actually very simple problems that we would not be able to solve from now till the Sun explodes even if we all of the computers on earth were only doing this. Say, solving a worse case instance of the Knapsack problem for n > 250 items easily fits into this.

If you want to be precise, the complexity class EXP best fits my description (though NP-complete would also be enough). That is, if discovering the required technology to build a self-replicating interstellar probe requires solving an instance of an EXP problem that is not ridiculously tiny, then we would likely never be find out how to build this probe. And no amount of AGI would change this, in this case.

I'm not suggesting that I have any reason for this ridiculously precise scenario to be correct. Just that some technology being allowed by the laws of physics should not be taken to mean that it is actually implementable in any imaginable amount of time, even if we were to assume singularity-style AGI.

by simiones

7/15/2026 at 6:09:40 PM

> if discovering the required technology to build a self-replicating interstellar probe requires solving an instance of an EXP problem[...]

Ah, I think I know why I felt it was very unlikely. Engineering constraints should be very "unlucky" so that only the solution works. That is, there's no wiggle room that allows an approximate solution (which is usually simpler to find) to work, even if it would be slightly heavier, costlier, or something of the sort.

For such a tight constraint not to be a coincidence, nature itself would have to be able to solve EXP problems. Which might mean that not all is lost.

ETA: ChatGPT has pointed out that many interesting instances of computationally hard problems are still solvable. For example, see SAT-solvers (SAT is NP-complete).

That is in addition to tight constraints the problem instance should have no exploitable structure.

by red75prime

7/14/2026 at 8:50:24 PM

This article contains 19 em-dashes, as well as the following direct quotes:

Not X, but dramatic Y:

- "But the missing few percent are not marginal; they are precisely the hardest items"

- "is not an engineering detail. It may be the entire problem.

- "the galaxy may be quiet not because nobody tried, but because replication is harder than arithmetic suggests."

as well as at least two other longer "not X, it's Y" type phrases.

Also, melodramatic phrasing like "Replication must outrun degradation — and degradation never sleeps."

Yes, someone could have written these manually, but these particular patterns are the things I notice most commonly in LLM outputs that I don't see in known-human writing.

by chrisshroba

7/14/2026 at 8:53:56 PM

Thanks. You saved me some time.

by therobots927

7/14/2026 at 3:29:40 PM

If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong.

- Arthur C Clarke

by bryanlarsen

7/14/2026 at 8:01:43 PM

OK, so elderly distinguished scientists say it is impossible for me to travel FTL by spinning in a circle with my eyes closed while on acid, guess we should start investing research dollars into that.

by neaden

7/14/2026 at 3:49:16 PM

[dead]

by aaron695

7/14/2026 at 4:11:13 PM

I did some research on this in the context of self-replicating PV panel construction. I arrived at similar conclusions: mining (ore extraction and refining) was the hardest part. Our current methods involve all involve some kind of high energy system:

- crushing

- breaking down with powerful solutions

- blasting

And a self-replicating probe will (initially at least) be a low energy system. I eventually decided that the pathway with the most likelihood of success would be some kind of very slow crushing/grinding machine that can break down ore into separable components, but then you get into a kind of Darwinist explosive combinatorics research rabbit hole: which crusher/grinder, what kind of machine, how to make something that works on different ore types, what mechanical pressure is better?

Conceptualizing something that can sinter and assemble PV cells was pretty easy, there are broad families of chemistries that work and they mainly differ on input temperatures and output efficiencies. Fairly tractable. But mineral extraction... yeesh, it's extremely difficult.

FWIW on the original article: I think the jump from "insulating wires" to "semiconductor fabs" was kind of obtuse. You don't necessarily need Turing complete PCBs or microchips for most (any?) of this.

by davedx

7/14/2026 at 5:10:04 PM

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.

by PaulHoule

7/14/2026 at 5:52:09 PM

[dead]

by cindyllm

7/14/2026 at 7:53:24 PM

Well, if this and other problems are ever solved towards self-replicating probes, we must just make sure not to over-prioritize replication like the Slylandro: https://wiki.starcontrol.com/index.php/Probe

by jonathanlydall

7/13/2026 at 6:28:31 PM

One "solution" to these problems is to have the probes land on planets instead of asteroids, and build the necessary infrastructure there.

by in-silico

7/14/2026 at 3:49:21 PM

That solves many of those problems, although it rather introduces a big gravity well to escape from when replication is complete.

by jpitz

7/14/2026 at 4:35:56 PM

Though, by the time we've replicated a complete industrial hinterland (up to and including a semiconductor supply chain) which the author describes, it seems like generating fuel and engines wouldn't be impossible.

Also to the authors last point (extremely long time scales causing degradation), it seems like we'd want high thrust capabilities regardless. i.e. maybe a small gravity well doesn't gain us anything, since we'd need big engines to get up to speed anyway.

by mNovak

7/14/2026 at 8:25:53 PM

Oh wow the concept of Vitamins, which I learned about from the Reprap Project, must have come from that 1980 NASA study!

https://reprap.org/wiki/Category:Vitamin

by SequoiaHope

7/13/2026 at 7:23:48 PM

There is no doubt that compressing a whole industrial supply network into a little probe is incredibly hard.

But I can't see microgravity specifically as a huge challenge. If you can get a probe to another star system, you can probably figure out how to spin it.

by voidmain

7/14/2026 at 4:29:38 PM

I suppose it depends if you're assuming the probe is a complete factory, just taking in regolith and spitting out new probes, vs if the probe deploys and builds up the factory on the surface of an asteroid.

In the latter case spinning doesn't get you far.

by mNovak

7/14/2026 at 9:54:04 PM

This whole story is so nonsensical - we can't make self replicating probes because the materials are very hard to extract - extract from what? Perhaps if that is the case, it's because you have to get the metal from that mineral-rich rock that's like 0.1% of said metal by content. Why not build probes from the rest? Common atoms like carbon etc.

by torginus

7/14/2026 at 10:08:47 PM

I imagine the extreme physical constraints will force us to explore alternative and unconventional forms of machines and computers, built from different materials available. For example, molecular or microscopic scale of self-replicating machines might be "easier" to build than what we typically think of as machines.

by lioeters

7/14/2026 at 10:19:42 PM

1. Carbon quality would need to be ensured somehow - sounds like extraction/refinement still necessary

2. Carbon seems to be brittle.

by crewindream

7/14/2026 at 8:09:08 PM

I find the confusion confusing. Meaning isn’t it obvious it would take an entire civilization and all of its technology to create functional space craft, computers, and mining robots?

I don’t see how anyone would expect some kind of self contained probe to be able to do all of that.

by bilsbie

7/14/2026 at 10:22:10 PM

> Is there a credible inorganic-only pathway for electrical insulation

Well, there is -- distance.

Also, the regolith is a good electrical insulator.

Also, basic organic compounds are plentiful in space.

by deepsun

7/14/2026 at 4:23:38 PM

The thermodynamic argument seems much more important to the Fermi Paradox than any difficulties in refining material, but I don't think I understand it.

by andrewflnr

7/14/2026 at 4:38:31 PM

If physics were to forbid closure at small scale, how could life begin? And how does a micron-scale autotroph reproduce?

by abecedarius

7/14/2026 at 6:30:36 PM

> 2. Is there a credible inorganic-only pathway for electrical insulation and semiconductor packaging?

What about glass, SiO2?

by M95D

7/13/2026 at 6:05:52 PM

Honestly, I always assumed that consensus was that replication is the hardest part. I believe we have almost none of the technologies required for that.

Whenever I read of von Neumann probes I always thought "How can that even made possible?".

by chopin

7/14/2026 at 1:16:47 AM

> 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 exergy, yada, yada, yada. We could start with sending self-replicating probes to the asteroid belt. There is zero chance that we'll attempt to send self-replicating probes to a different star system before we send them inside our own solar system. And the second error is this:

> Bootstrapping this loop [...] is a chicken-and-egg problem that no study I am aware of has worked through at the level of actual process flowsheets.

The fact that the current technology is not adequate, and nobody even attempted to solve such a problem is a weak argument. Three hundred years ago nobody had "worked through the process flowsheets" of making an injection molding machine, or a 3D printer, or a power drill, yet they are all available now.

by credit_guy

7/14/2026 at 6:58:57 PM

The subheadings are all full of AI tells.

> The closure problem, honestly accounted

> A thermodynamic framing

All of those read like AI, especially considering that the subsections aren't consistent. Some are numbers, some are not, some are framings some are problem juxtapositions.

EM dashes everywhere, AI tells in subheadings, "It's not X it's Y" all over the text of the body. This is clearly AI writen.

Notice also the article has two by lines. At the top it's "by Paul Gilster" at the top of the text it's "by Peter Marinko"

Also note that the "metallugrist" they're interviewing that they claim "his current work explores the thermodynamics of technological civilizations" at Uppsala University, but the university's page for him says he's only involved in Animal Research Ethics Committee

by malfist

7/14/2026 at 9:11:08 PM

> Notice also the article has two by lines. At the top it's "by Paul Gilster" at the top of the text it's "by Peter Marinko".

It is Paul Gilster's blog. It looks like all articles there are by him, hence his byline at the top.

In this particular article he writes an introduction talking about self-replication, then says "Right now I want to introduce Peter Marinko, who today weighs in on self-replication and the problems therein", describes Marinko, and then the rest of the text is Marinko's, hence the second byline after Gilster's introduction.

Something similar happens in the next article on the site. Marinko write a length response to comments on the first article. Gilster decided that would be better as a separate article to further discussion: "When Peter wrote recently with his thoughts on reader reactions, I asked him for permission to run it as a regular post rather than a comment, because I think this is a lively question and would like to see us continue to explore it".

So that too is a post by Gilster, and so with his byline, but after an introduction it just run's Marinko's text, so has a second byline for that section.

He does the same thing on this article [1]. He wrote a review a paper, some commenter had interesting thoughts, and Gilster posted an article talking about that, introducing the commenter, and then the rest of the article was the commenter's text. So two bylines, one for the intro and one for the guest text.

It looks like the other articles on the site are just Gilster, and so only have one byline.

[1] https://www.centauri-dreams.org/2026/06/05/observations-on-t...

by tzs

7/14/2026 at 3:26:29 PM

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

by JohnMakin

7/14/2026 at 3:55:21 PM

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

by credit_guy

7/14/2026 at 5:19:45 PM

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

by JohnMakin

7/14/2026 at 7:05:46 PM

I didn’t assume that. The author makes the opposite assumption: that because nobody has ever proposed a path to technological feasibility, that thing will forever be technologically unfeasible. I simply find this argument to be very weak.

by credit_guy

7/14/2026 at 5:36:18 PM

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.

by snowwrestler

7/14/2026 at 6:08:59 PM

But LLMs go through post-training that gives them a style distinctive from most human writing. It's certainly detectable.

This reads as heavily LLM generated/edited to me.

by jamilton

7/14/2026 at 6:24:49 PM

I find this line of reason to be incredibly irritating. So anything written above the level of "see Spot run" now must be AI slop? The author's piece is written well and reads easily. As a long-time user of nonrestrictive elements in sentences, I bristle at the idea that only AI is capable of writing sentences containing brief asides -- the things between the em dashes -- now.

by primoprimo4444

7/14/2026 at 6:16:28 PM

It’s true that current tech can’t do it and he has said it but it doesn’t mean new tech can’t do it. He is assuming other civilizations cannot do it and also assuming probes will be easily detected therefore there are no probes

by m3kw9

7/14/2026 at 7:10:51 PM

[dead]

by dmurvihill