Cheers for the link fix.

Your quote is from https://en.wikipedia.org/wiki/Asteroid_mining#Self-replicating_machines and you apparently didn't include the first sentence; "A 1980 NASA study entitled Advanced Automation for Space Missions proposed a complex automated factory on the Moon that would work over several years to build 80% of a copy of itself, the other 20% being imported from Earth since those more complex parts (like computer chips) would require a vastly larger supply chain to produce." (emphasis mine).

Even if the percentage of external resources is dropping low or near zero, it has to be zero for self replication. There's no point in having it make a perfect copy of itself but not having any fuel, or fuelled up but has no battery acid.

Perhaps there are ways of building metal 3d printer nozzles in space, maybe you find a large cube of titanium randomly floating around, you're carrying a couple dozen tons of cnc machinary, you're willing to expend the fuel to get over to it, use a 6-axis arm to retrieve it, use some magic replaceable coolant for the drill bits and can run this all from solar power. But how you think you're getting this built in a decade is beyond me.

You seem to handwave when I say making chips is hard. It takes ridiculous tooling to make a usable chip, and the requirements a self assembling machine would have would be extensive. I'm not saying it's impossible to put a chip manufacturing plant into LEO, but it would be massive, and you would have to send silicon up to it all the time.

You seem to be confused with space mining. If i dig up 100 gigatons of material to extract say, 5 million tons of helium. I haven't launched the 100GT into space, it stays on the moon. The mass is relatively unaffected.

To summarise; your statement that you could do this solo, and in a decade, is crazy. That the end result would not be massive is crazy. And in my opinion, you wouldn't find enough material in LEO to do much of anything like moving around, let alone self assembly. The machine would just have too many consumables.

Yes, it wasn't a complete abstract, there was no intent to be misdirectional, and I had previously acknowledged the "supply chain" issue and that the link specificly mentioned asteriod mining as opposed to LEO debris. The LEO debris is just a starting point - again, because it is close, easy to reach, and needs clearing up anyway. If using this to mostly make things, it reduces total cost of deployment of these things, realistically sillicon chip production is likely to be one of the later things deployed, for a variety of reasons. But there's no reason it can't evenually be made to happen. Ofc, once mass harvesting sillicon this won't be much of a concern overall, with facilities in place to be building almost anything else it's possilbe to account for this "supply chain". The earlier we can produce this, though, the better.

Near zero is about all we can manage, realistically, until we've amassed more resources "up there" via the likes of mining(say by throwing one of these machines out into the asteroid belt past Mars) and then it really can be self replicating. Near zero is still a damn sight better than "you're going to have to lift everything". One of these concepts makes things a little more realistic to persue. You're not going to find a large cube of titanium, but you can find plenty that will be able to be rendered into a cube - or a more suitable shape - readily. You'd definitely not need a couple of tonnes of CNC machinery - a few six axis arms are almost essential but not for retrieving crap floating thorugh space, you'd use something more like a net - maybe more like a wind sock would be more sensible. The arms would hold and or mainpulate parts and toosl. All this could be run from solar power, but there might be some better tricks to deploy. Possibly hydrogen generators, with an on-demand system splitting water harvested from comets. Making a perfect copy of itself, sans fuel, is still useful, as it reduces the "cost" to make it operational to fuel. Once this can be sourced externally then this is even better. The goal is even for fuel, but we'll have to work with what we can wrangle.

One way for dealing with "fluids in microgravity" and their behavioural adjustments is potentially Tesla's valve system, or something based on. I was under the impression the extruder head on printer nozzles operated under pressure other than gravity feed, commonly, it shouldn't be an issue. Another is to just centrafuge the lot and make artificial gravity. Or you could 3D print the moulds in plastic, disolve the metal as a hyperconcentrate solution, insert a seed crystal into the mould, inser the solution into the mould, very slowly cool the solution and then lend the seed crystal a little kinetic energy and watch as physics moves all the atoms in the metal to form a single crystal the shape of the mould. Discard mould and finish part.

Coolant on drill bits and the like was a concern, With artificial gravity Selective Laser Sintering might be possible, but otherwise carving from a block using a laser sounds plausible to me. Otherwise coolant can largely be recycled and the refuse lumps of shaven metal it sweeps can be harvested.

Yes, the "tooling" involved in CPU fabrication is precision affairs, you may consider me "dismissive" but I'm aware it's possible. That's all I need. Once I have machines that can build their own parts, they can build themselves again, mostly, with subtle differences that result in more precise output - a few cycles of that and it can produce something suitable, surely. The supporting infrastructre may indeed be extensive, but it's not as if there's any shortage of room in space, so we're good there. You avoid sending it sillicon all the time by stealing asteroids from problematical orbits, and from resources thrown back by the first seed you throw out past Mars to start on that asteroid field.

The mass on the moon is relatively effected, it's redistributed - then it's absent 5 million tonnes. Five million laps later, it's orbit is now noticably different.

Doing it solo isn't likely what's going to be happening, I can already draw on a lot of research in a lot of directions to springboard the entire affair, and hopefully I'll encounter others with more vision - I know they exist, we just need to cross. Considering 97% of what I'm talking about already exists, it just needs to be combined together in the "right" way then I don't really see why it shouldn't be possible. You might well lable it madness, I see plenty talking greater insanity. The end result shouldn't require to be massive, either. What I have in my shed might be, but what we lift can possibly unfold itself and assemble once it's up there automated, using LEO debris for the last bits of panelwork etc. There's far more material in LEO than you give credit. Look into it. More than enough to pop off a few dozen tugs a copy of itself and a few centrafugal launchers - yes, it's likely to require additional lift to make these things functional, but it reduces the cost of deployment, significantly. I wager that there's enough afterwards to build much of the facilities to process resources when they get thrown back from past Mars. Selling 40% of that to earth should pay for getting the "missing" equipments and parts to the facilities. If we can score contracts to remove LEO debris, then this can even be made to pay for itself somewhat. Even if things like making the bulk of EM-Drives is unsuitable due to it being hype, we can do things like make the Xenon tanks and much of the ion propulsion systems for the tugs up there - reducing lift to electronics packages and fuels. Once we've some facilities in place, collecting more scrap will literally cost fuel - add 10%-15% on the cost of getting that fuel there and I'd wager most others offering a similar service wouldn't be able to compete. At the end of the day, this initative doesn't need to be made ot pay for itself, but aiming for it can't hurt. It's the mining between Mars and Jupiter that comes with the payback. Recyclling LEO debris is good practice for being able to build additional units and spare parts remotely. Yes, there will still be a requirement for "external" goods, this is unlikley to be completely eliminated in the early phases, but we can reduce it significantly and that will matter. Eventually as resources and capacities expand, this will solve itself.

When you said self replicating probes moving outwards I thought you meant Von neumann probes, maybe I'm getting too caught up in that. From a practical standpoint, you could perhaps use some more basic automation to make some kind of salvage operation for LEO that might reduce launch costs for certain payloads (eg by preparing a metal heatshield, or maybe an engine nozzle). Your arguments jump from LEO utilisation to mining, were mining the point where a more complex machine was designed, then I would roughly agree. You're not finding water or silicon in orbit for example.

5 million tons is 0.000 000 000 000 07% of the moon's mass. Try to imagine the infrastructure/energy required to move that amount of mass off the moon and you'll see that worrying about deorbiting the moon isn't a worry.

I don't disagree that there are (metal/component) resources in LEO, rather that they are energy-expensive to retrieve. You need to have a magic propellantless drive to make this feasible.

Take a couple minutes to sketch out how you think this would be built and you'll start to see glaring design issues. Even in your last post, you claim you can do away with the need for an arm and use a net instead. When the object is retracted in, how do you position it for drilling/lasering/whatever? What if it gets tangled in the net? What if a sharp edge cuts it? If it's metal cord, how heavy would that have to be to run 500m and have a catchment of 4m^2? There's two dozen components bolted, welded and screwed into this piece, how do you remove them? A screw holding a brass clip is stripped, do you discard the whole piece? How do you even discard anything with only a net?

I've read about teams trying to solve just the retrieval part of debris cleanup, and they expect to take years to have something with this capability. http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/7867/The-ESA-Wants-to-Harpoon-Space-Debris.aspx (harpooning; expected 2021, article from 2014)

I've taken more than min to sketch. Sometimes there's been more than sketches. The "net" was just for orbital snare - it'd still need to be taken out of the net, and manipulated ofc. And yes, things like six axis arms will be handy here. You probably wouldn't be snaring it with the facilities, instead using "tugs" to pull it in. You prevent tangle by having the "net" more like a "wind sock" - you can close the "mouth" with a drawstring like arrangement - sharp edges may be an issue, but it should be possible to manuever it quite gently to minimise this. Using the right materials can assist greatly too. You'd not discard the lot for a stripped screw - can drill that out, possibly with a laser. You don't discard from the net, you discard from the facility. One of the first things this "facility" should really build is some "boxes" and some sort of racking system in order to store parts. The idea is to use as much as possible, but certainly there will be "refuse". This could be centrafuged into the atmosphere to burn up if it's a problem - but if possible retaining it until we can recycle it would be better.

The LEO debris is only really energy expensive to retrieve when you have to factor in fighting Earth's gravity to get there. We can get that done once with some tools and tugs. Instead of pulling it towards the facility, and fighting it's momentum you wait until the "right" point in it's trajectory and then give it a little push - work with it. Many small adjustments can more efficiently provide adjustment of Delta-V. If the EM-Drive is a go, then there's your magical propellantless drive. There's a few "interesting" projects in the JPL that would otherwise potentially be of viable and many other more nutcase schemes that could hold potential. Absolute worst case then existing technology provides well for ion drives with xenon propellant - which can be lifted relatively cheaply as it's so light - and we can operate a refuling operation. Once this crap is in place, then the charge we require for removal of debris can easily become more than competitive and still pay for more fuel than when we started - or lifting of other consumables as required(mostly). We can reduce the cost of printing out more tugs for example to the electronics packages the functional part of the drive, etc. Again, the goal isn't LEO debris, that's just; close, needs clearing anyway, is good practice, can be used to reduce the cost of developing further the facilities required for mining and to actually do something with the produce of mining.

Von-neuman would be a "ultimate goal" - but something pretty damn close is achievable with current technology, with the current resource pool. Close enough to actually make itself fully Von-neuman complient when it's more practically feasible. Water and sillicon are in orbit - water is evacuated quite commonly, and chemical rockets tend to generate quite a lot of this - which is why it rains shortly after a launch - so it it can be intercepted before it de-orbits then it's harvestable - sillicon exists in the form of existing digital equipment's components, and the occasional MMOD fragments. And "visiting" matter, we might be able to catch up to and then steer/redirect some of the smaller/slower of that. Definitely feasible if the EM-Drive is functional as claimed. I'm not sure how "recycled silicon" plays out TBH but once ground into a powder, melted, grown up again as a single crystal it should be fine I'd wager. Could even save the hassle of doping, but I'm not overly confident. But again, I'd suggest this sort of thing to be the later features added to the system. It'd be ideal if it could start with, but in interests of reducing weight and complexity of initial launch equipment it'd possibly be best absented. Again, at least 2/3 of the facility required for can be built up there, out of repurposed scrap. It'd likely be more productive to aim for solar panel fabrication, first, as the sillicon doesn't need to be quite as high grade and much of the development process and experiences gained within should make the silicon waifer production "easier".

You may of noticed my timeframe was years. That's just me, however. I'm confident it won't be. This should solve the problems I haven't accounted for and reduce development time. As a concerted effort I do not think it unfeasible to have something that has paid for and built itself on the ground, and ready to clip to ISS about 2024/2025 when NASA retire from it and move operations to their cisluner facility they aim to have in place by then.

My original contention that you can't get this done in ten years still stands, but I don't seem to be able to convince you of that, regardless of how many design features both yourself and myself come up with to make it function the way you want.

We'll have to disagree on the value of LEO debris, from what you've said I doubt I can convince you there's little retrievable water in orbit.

And although I agree that self replication is a great goal to work toward, we seem to have wildly different estimations on how long such a project would take.

Thanks for the discussion.

I don't honestly expect there to be reliably usable amounts of either water or silicon in LEO - but it is there.

As to the value... In some orbital "parking slots" there is high value. Especially as these are already occupied. As technology advances at a wonderful pace, and equipment fails over time etc some of these slots are filled with dead equipment, or so far below technological capacity it might as well be dead. There are people that will pay to have this removed. Then there's the few hundred tonnes of upper rocket stages that have built up steadily since the 60's. It's certainly not worth ignoring, and LEO debris is a problem that needs clearing up. Few dozen tonnes of otherwise dead birds, maybe about a dozen tonnes of paint chips, dust, solar cell fragments and other MMOD. This could be made viable in it's own right, let alone as a springboard towards better things.

Your contention still stands, as does my lack of caring for it. Ultimately, actions speak louder than words. I'll be doing what I can. That can be enough. It's not as if I'm asking you to do anything. The only real "assistence" that would be more generally required would be to get the finished product into orbit - preliminary guesswork suggests it's a more than reasonable per-head sum and I honestly think I can get that paid for too - and that'd not be happening until there's an operational product capable of performing to specification. Ofc, I predict there to be more with greater vision and thusly it won't just be me, which pulls it for definitely in under a decade.

This article is relevent to the space mining. The space mining will be one of the most important periorities of Asgardia especially seeking for minerals which are not plentiful on Earth. For example, titanium which is the main component for constructing the spaceships is not so ample on Earth and its sources will not sufficient for the future demand for the spaceship industries. Copper has become much more expensive since 2003 because of the very high demand of it for the electronic industries. Gallium has also very important applications in the advanced and complicated electronic industries. The space mining will be cedrtainly an ample source of titanium, copper and gallium.

Gallium also has a wonderful reaction with aluminium, which when doped with will react violently with water. Just violent enough to split the bond between hydrogen and oxygen, not enough to set it off. Unless you pressurise it. But it could easily form a printer cartridge like replacable catalyst pack for an on-demand hydrogen system that can safely store enough hydrogen to make a hydrogen generator output electrical energy for months in a few liters of incredibly safe water.

The best bit is you can harvest all of the gallium and the aluminium out of the catalyst pack to build another.

But definitely, the stock of pretty much everything in the entire periodic table "up there" are rediculous. We just have to get them. I personally feel LEO debris is a logical step, but meh, Things like the stocks of nickel, titanium, copper, sillicon, oxygen(can split that from silicon dioxide etc) iron, platinum, gold, gallium, francium etc are what make me consider things like five meters thick NiFe skinned in 6cm thick titanium as a outer radiation shield(over the entire mass of facilities, that's a lot. And that's just the outer radiation shield, let alone the outer hull, the inner pressure hull, or anything inside the facility) there's really that much there then things that seem utterly rediculous right now become perfectly feasible and almost trivial once you start making things that can make use of these resources. And NiFe will be something there's a lot of, in attempts to get at other things.