SomeGuy123

We have self replicating machines today, and they have the properties described. They don't need to be nanoscale, and qualified experts never thought they would be. (some day, pieces of the machines would be nanoscale but the overall system would not be) We currently do in fact have industrial equipment sophisticated enough to perform every task needed to produce the equipment itself, and partial automation - enough to prove that self replication is possible. There just isn't the money or economic need for full 100% self replication at the present time, but there are massive factories that make every component used in those factories, and robots that can duplicate any task a human hand is capable of doing, so long as sophisticated judgement is not required...(you would reject any part that doesn't meet close enough tolerances so that you can use the same motion on every part going through that particular station) So yeah, we have such experts right now. As for creationists...the reason their beliefs are wrong is because scientists can show how evolved mechanisms did get their, piecewise. Each predecessor, simpler version of something evolution made was functional in a simpler form. In the evolutionary world, it turns out that plain RNA, without anything else - just RNA in a test tube - is self replicating. Certain magic RNA sequences are able to catalyze copying themselves because they conform into a certain functional shape. Reason the creationists are wrong is because the special environment that nature operates in, and the chemistry it uses allows for gradual evolution. Intelligently designed equipment that humans make does not allow for this. Take a rep rap 3d printer. How well's that printer going to work if half it's parts are missing? Describe to me a version of the printer that is simpler that still works. All a self replicating machine is something like a 3d printer, a set of assembly robots, a CNC mill, some chemical reactors, plasma furnaces...it's a lot of machines that the sum total of all their collective efforts is self replication. We already have all of these machines today, we just don't have the money and design resources to make them closed loop in this way.(and they ARE closed loop, actually, just no single facility has all of the equipment under the same rooof) A nanomachinery version is just the same equipment, shrunken... So no. You aren't qualified to make any other comments on this subject. You're wrong about the lack of experts - plenty of industrial and process engineers today are more than qualified. You're wrong about nature. You're wrong about operation speeds. You're wrong about the design fragility of intelligently designed systems. You're basically just blowing hot air. Aren't you like a grad student in physics?

The question is like asking "what if the Challenger never blew up". When you analyze real life disasters, they are virtually never caused by "black swan, 1 in a billion" fluke events happening in isolation. Almost always, there are several causes, and the real risk of the disaster - as a result of a number of consistently made mistakes - was actually high enough that it was inevitable. The RBMK reactor had a number of faults. It used graphite as a moderator and was vulnerable to odd phase changes. It had a design flaw where inserting the control rods would increase reactivity. It had a positive void coefficient at some power levels. The safeties could be overriden without requiring physical rewiring of the plant's computers. The computers were too slow. The control rod motors were too slow. And on top of all these faults - making a meltdown a real likelihood - it had no secondary containment. So maybe the big disaster would have happened in 1990, or 1996, or some other more recent year. It was still basically a certainty.

Try reading Nanosystems, K^2. You're talking outside your area of expertise. To summarize, the world's leading expert on the subject points out that vastly faster optimizations on the replication speed of life is possible.(he works it out based on fundamental theory and points out the absurd inefficiency and floppiness of existing ribosomes) The reason life isn't this fast is because (1) it isn't intelligently designed, and the kind of replicating machinery that would be orders of magnitudes quicker would be radically different from anything evolution has reached (2) current life depends on liquid chemistry for legacy reasons (3) designs that are faster than existing life by several orders of magnitude by using stiffness and tightly designed feeding chains would be very vulnerable to design error. A really well made, high performance machine will fail completely if any part is wrong. So evolution can't random walk it's way there, as it is sort of a skyscraper on the evolutionary landscape surrounded by a vast moat of dead zones. Ironically, real self replicating nanomachines might easily be so fast that waste heat becomes the limiting factor. You'd be burning megawatts per cubic inch if you can reject the heat fast enough.

Yes, you could make self replicating factories with a far lower tech-base needed if the factories "only" self replicated 90% of themselves and needed 10% of their total bill of materials imported from much larger and advanced factories on Earth. What is the Moon missing? If it's a chunk of the earth, originally, it should have a true element mix close to the earth. (but missing the liquids and gasses that are in the atmosphere and oceans since that all sublimated long ago) Nobody has actually dug deep rock core wells at sample points over the entire lunar surface, so the "known" composition is just guesswork.

Observation : the visible universe seen by telescopes does not appear to be majorly edited by intelligent life. Hypothesis : "fast" FTL travel is impossible. The reason is simple. In science fiction, it is common for there to be no ultimate speed limit. More and more advanced alien races can get around quicker and quicker. N00bs like humanity might take a few days to reach another star (like Starfleet), but there are methods that are faster and faster, to the point of reaching other galaxies in hours. What would be the consequence if this actually is possible? (never mind existing knowledge of physics, let's just say there is an exploit not yet found that lets you basically teleport anywhere in the universe instantly) Well, all it takes is one species with the ability to (1) teleport around near instantly (2) consume arbitrary solid matter to make self replicating robots. Basically, once they have the technology for one and two, ZOOMP, whole universe is converted. We as a species never come to exist because this happened long ago. Ergo, since humans do exist, it's probably not possible to do (1). (we basically already can do (2) as we ourselves are such replicating robots. We just need some tools we already know how to make to let us turn arbitrary chunks of planets and asteroids into things we can eat and live in)

Anyways, I do think the magnet railway is a great idea. Having something leave the Moon at orbital velocity (just too low for sustained flight, there would have to be a correction burn after launch to fix your apo and periapsis) without a puff of propellant consumed is how you do something long term. Only n00bs burn propellant - master space engineers avoid it whenever possible. There are far less points of failure - a track segment failure on the magnetic railway could result in some nasty wrecks, but most of them probably will leave most of the railway intact. You can do maintenance on it. Unlike an elevator ribbon, a shut down railway with faults can be taken apart whenever you want - it isn't under perpetual tension.

Remember you do have a little leeway. On approach you'll have extremely exact positioning. Laser beams from near the mouth of the maglev track, phase detection of multiple encoded beams, markers on the lunar terrain leading up to the track - there are a lot of methods, and you could use several methods to make sure you're "in the pipe" on approach. An abort would just be an RCS firing so you miss the track by flying a few 10s of meters above it. You don't have to have a perfect solution of the N-body problem, merely one good enough that you can correct any small errors on approach before you actually have to make contact with the receiver track's magnetic fields. And it doesn't have to be perfect - unlike the ski example, where you probably have to touch the ground with a tolerance of less than a millimeter or risk destroying your skis or bouncing into space - you have a little more tolerance with magnets. And even doing this routinely is possible. You would make the digital systems that do this all run on single solid state chips. You'd use FPGAs for perfect, clock by clock timing. You'd have 3 or more parallel digital systems all wired to the sensors. (and majority gate decisions) You'd have enough parallel sensor systems that if several fail to give accurate or consistent data the faulty data would be rejected automatically. (it's as simple as calculating the position and velocity reported by each system and rejecting the ones that don't agree precisely with the majority) All this would physically fit on a single circuit board with a digital bus that connects to the sensors. Making computers this reliable is expensive but routinely doable. The glitchy computers you are used to using had their software made in a rush, they have vastly more features, they may use a wide variety of hardware, they update the hardware chips in use every couple years, and so on. I'd say the technical challenge is the magnetics (a maglev railway able to receive something at over a kilometer a second? Wow. ) and getting enough construction machinery to the Moon and operating it for years to build something this major. You'd basically need self replicating machinery and a massive industrial base on the Moon itself.

What exactly is wrong with maglev? You can even fine tune your control circuitry to make up for small variances in the position of the maglev track segments. No physical contact, you can even store the energy of orbit spaceflight or use it for something. (if you were really clever and used all superconductors, you could dump the energy of decelerating one spacecraft to launch another.)

You could in principle make this really really simple. A package of RCS nozzles pointed different directions, a couple of pressurized tanks, a bank of valves, a valve controller, and the guts of an iphone. (a camera to see the starfield for position references, a radio, IMUs) Just saying a "full featured spacecraft" makes it sound a lot worse than it is. It wouldn't be cheap, but it's not that bad.

These were example numbers of why you get more out of your capital. You can make the quench gun bigger.

Aww. It was a cool idea. One nasty problem with something like this is that it costs a bunch of money in infrastructure. (those massive microwave arrays). So you need a large launch volume to make enough money to break even. Except, supply and demand doesn't work that way. Suppose you can break even if you launch 10 times global launch volume at $2000/kg. Sounds good, right? The issue is that there just may not be enough demand for 10 times the current spaceflight volume at that still relatively high price. $2000/kg is still very expensive, and so only delicate and light satellites are worth it, and you only need so many of those.

Why would the elevator be cheaper than a quench gun? The rail gun, yes, because the rails will erode and need to be replaced every so often. A quench gun doesn't have this problem (it's a gauss gun using superconducting magnets). A quench gun, you could in principle launch a payload every few minutes, day in and day out, until something breaks or you run out of payloads lined up. The advantage there is if you can launch every 5 minutes 1 ton, say, you can launch 105,000 tons a year. An elevator, if it only can carry 100 tons in transit and the transit takes a week of climbing, has a yearly launch volume 1/20 of that. It's also vastly easier to work on the quench gun. It's a big set of separate modules, and everything is inside some gigantic set of tunnels in a mountain or something, readily accessible. A good design for one would include maintenance access equipment to let you rapidly swap any piece of equipment with a spare to get the system online as fast as possible. If elevator cables start to fail, I'm not even sure what you can do. Dunno what kind of spackle can patch a cable under this kind of tension...

Actually...if you used the gunpowder to drive a piston and hydrogen gas as an intermediate...

Then this really is just straight up science fiction. Being able to produce something this complex and fragile in orbit, building a facility that needs thousands of tons of raw materials in a station in geosync, etc. It kind of defeats the purpose of a space elevator if you have to launch more payload than the total launched in the history of orbital spaceflight to build a space elevator. You pretty much would need to first develop cheap rocket flight first which then makes the relative advantage of an elevator smaller.

I'm actually surprised by how many people agree with me. Apparently, I was wrong about deployment. Naturally, it sounds even harder to get into orbit a spool of elevator cable. The cable has to be thick enough that a very small climber car can traverse it bringing another cable, and there are other issues such as it needing a coating to protect the nanotubes inside against oxidation, etc. So a single reel of elevator cable might be extremely heavy.

It's my fairly well informed opinion that Space Elevators are a horrible, no good, very bad idea. Now, there are details I don't know. But I feel that the facts I do know are so damning to outweigh any positive element that could be proposed. Here's what I think I know : 1. The elevator cable has to be at least 35,786 kilometers long. This means if there is a break anywhere on this cable, the entire apparatus is destroyed. 2. The elevator cable has to somehow be launched from a rocket while unspooling in flight, and it needs to mass thousands of tons in total. This means if it's lost, it will not be cheap to replace. (I understand that the first rocket launches a "leader" cable that is reasonable in amss and then you would have to add additional cables to the bundle by having climbers carry them) 3. The cable is under so much structural stress that the only proposed material that is plausible are extremely long carbon nanotubes and extremely strong bonding between the separate molecules to prevent them from delaminating. Oh, and it needs to be flexible so you can spool it as well...It can't just meet the strength requirements, it has to be flexible, resistant to external wear, manufacturable for a cost you can afford, and have enough longevity to last decades... It's one thing to ask material scientists for unobtanium. It's another to ask for 5 more desirable characteristics when the first one is already just a hair less than impossible. 4. Due to 4, you need 35,786 continuous kilometers made to near nanoscale perfection. Any flaw could potentially result in a catastrophic failure. There won't really be any other commercial use for elevator length cables, so you're talking about creating an entire industry of R&D and engineering and factories just to manufacture these things. A product that has to be perfect costs exponentially more than a product that has a moderate acceptable failure rate. This is why Xboxes cost a tiny fraction of the cost of the same capacity computer in a missile. (and actually no missile has nearly that much processing power or memory) 5. Currently, the entire energy of orbit flight is supposed to be beamed to the elevator cable using lasers on the ground. Solar cells can only be so light, so the transit car crawls it's way up. This is horrible for 2 reasons a. An elevator represents an immense capital asset, probably hundreds of billions of dollars. Yet since the cars can only crawl up over a period of days, it means you are not getting that much payload into orbit for your money per day. Like any asset, it depreciates and the elevator will need to be replaced, so for it to be worth it, it needs to deliver more payload than the same money could buy in mass produced conventional rockets. b. The climber cars put mechanical wear on the cable surface. 6. Even optimist economics of something like an elevator or laser launch are only cheap if there is large launch volume. But space, as an economic endeavor, isn't profitable for large volumes. Once you have enough communication satellites to saturate all the available RF spectrum, and enough spy and weather monitoring satellites to meet everyone's need, there isn't actually much market for space travel. There is no evidence that low gravity manufacturing will ever be better than machines on earth. Raw materials are too expensive to recover - retrieving enough platinum to pay for an asteroid redirect mission would crash the market price for platinum....(note I do think it will eventually be worth it, but you need self replicating machines so that you only need to launch a factory massing a few thousand tons and it then copies itself with asteroid or lunar mined material thereafter. That is radically advanced technology of the future. And, if you had self replicating machines, you still might not build elevators. You could instead build an array of thousands of automated factories making big dumb boosters in parallel...) 7. A space elevator, a national asset worth hundreds of billions of dollars, needs a single purposeful break to fail. A single missile, launched by a rival nation state or terrorists, need only break it at a single point to cause it to snap. Probably the pieces wouldn't be dangerous to people on the ground, but it's essentially a financial asset that is indefensible (it can't move or hide itself, missiles can be stealthed with radar absorbing materials so you can't see them incoming) that is trivial to destroy. (a 1-10 million missile knocks out hundreds of billions of elevator cable) If a missile sounds too unlikely, keep in mind a simple shaped charge against the cable is enough. That in turn means security and near strip searches of anyone permitted near the cable, which reduces the economic value of it because of all these costs and delays... Anyways, TLDR, I don't see why anyone ever wasted any time on the space elevator as a concept. It fails the most basic analysis of feasibility. There are other ways to reach space, and some of those ways could be potentially made very cheap with advanced technology.

Physics. If you draw out the actual vectors, and keep in mind that RCS thrusters cannot burn their fuel instantaneously, then you waste RCS fuel, always. Only way to not waste fuel is if the burns take only microseconds to complete, and the gas isn't that fast to exit the thruster. Maybe if you change the thruster orientation during the burn keeping it aligned in a way that compensates for the rotation. The reason your idea is still bad and will probably never be done in the history of manned spaceflight actually has to do with design coupling. You talking about the complexity of electromagnetic bearings - yeah, that's some complexity - but you fail to appreciate that if you take a perfectly good rocket engine and fuel tank design and expect it to take rotational stresses that vary depending on the location on the ship - you end up with immensely complex engineering problems. The current heat radiators and solar panels they fly are only able to work in microgravity, as a side note. If the bearings don't have to hold an internal tube that astronauts can traverse, it's just a big bearing in vacuum, that's straightforward engineering.

No. There's still an immense difference in complexity between "3 or 4 ring modules with the same thing in each" and "everything in the ship must be designed around always being spun." The facts of the problem tell me that Nibb31 is flat out wrong, his concept is roughly as bad as the Apollo proposals before they settled on separating the lander and command modules.

You aren't, but there are better solutions that don't consume propellant. The optimizer in me says the most mass-efficient way to handle this is to divide the habitat ring into 2 separate sections. Try to make the split such that there isn't the need for an excessive amount of traffic between the 2 rings. For example, processing fluids in zero g is annoying, and some terrestrial plants don't like to grow, so maybe the food production and water recycling systems are in ring B while in ring A you have the crew. Or maybe the split is that ring A is sleeping areas and residential and ring B is actual work areas. Anyways, however you do it, the rings spin in opposite directions and have the same mass. So the net angular momentum adds to zero. One way to switch between rings that eliminates most or all air loss is to have a transfer ring. This is a ring that can spin up or spin down, and it is located between the 2 main rings. It might actually not be a complete ring, just 2 dumbbells attached to a central hub. To transfer it speeds up to match velocity with one ring and connects hatches to the side. Crew and cargo get in. It then spins down and spins up the other direction. (a lot of acceleration if you do this quick, so there might be acceleration couches) A transfer ring design avoids hub bearings completely, the hub would just be a central point where all the tension cables supporting the weight of the ring come together (and an electromagnetic bearing). Even with a transfer ring, you'd need a fourth, "counterweight" ring. This ring would be full of weights. You could actually make it a solid disk made of tungsten or lead, and have it dual purpose, acting like a radiation shield between the crew section and the engine. This right might rotate clockwise or counterclockwise, at a wide variety of velocities, including some that would crush humans from g forces if they were on the ring. This ring would act to balance the angular momentum between the 3 rings (main ring A, main ring B, transfer ring) so the net actually adds to zero. That way the 2 main rings can remain at constant velocity. You could also use this ring as a gigantic gyroscope to force the ship to spin on an axis.

I'd want to do it with omniporters. These are robots that drive along grooves or rails in the outer hull of the ship, or transit down conveyer tubes. They carry roughly a cube shaped "cargo pod" that can have anything in it that will fit. Well, there would be cryogenic gas pods - a cryogenic bottle shaped to fit inside a cube, with various ports that robots can connect to. So to transfer between spinning and non spinning sections, one of the main things to move is cryogenic gas. So the liquid CO2/liquid O2 would be used to fill the gas pods, then porters would move along the grooves to the interface between spinning and non spin sections. There would be an outer transfer ring with a groove in it. Porter moves into that groove. From non-spin section -> spin : transfer ring matches speed with the spin section (the transfer ring is mounted in the non spin section), so the groove is now perfectly matched with the groove in the spin section. From spin -> nonspin. Robot waits in the last groove segment of the spin section until the transfer ring matches speed. Then it slides over into the groove on the transfer ring. Transfer ring decelerates to rest and the robot proceeds on it's way. This to me makes sense. You might bring aboard asteroid ore, each section of ore kept in a separate cube storage container in a holding bay. You send the ore to the smelter and the output ingots get carried away in one set of porters while the slag gets stored in a separate set of cube containers. So the ship's raw materials are kept in containers that are separate now. When a manufacturing order is placed, a whole lineup of porters bring by cubes containing each needed material. More realistically you'd probably end up storing many intermediate stages as you build things.

What you're neglecting is that when you spin something fast enough that there's enough apparent gravity/centripetal acceleration at the end to stand up and walk around (so at least 1/6 G, probably more), the structure of the spacecraft in that section has to withstand stress equal to the 'weight' of the spun sections. That structure is mass you wouldn't otherwise need. I'm describing interplanetary vehicles that are made in orbit and will never leave a low gravity environment. They will never touch a planet's atmosphere, and their engines won't subject their structures to more than 1/100 of 1 gravity (10 centimeters/second squared) even with nearly dry fuel tanks. Things like the heat radiators are optimal if they are incredibly thin foil sheets or vapor sprays. Fuel tanks are optimal if they are basically balloons just strong enough to keep the slush hydrogen inside in one piece. And so on. By making everything strong enough to be spun you're making everything heavier, increasing dry mass, and thus reducing your performance and increasing the minimum propellant needed for a given mission. As for complexity : it's relative. A nuclear interplanetary spacecraft won't be simple, rotating bearings or not, and the bearings are not the complex part, either. A lightweight heat radiator system or a fusion engine would be immensely more complex. By making it lighter, you reduce costs, leaving your more money for your immensely complex engines and heat rejection systems and closed loop life support systems and so on.

Here's why you don't rotate the whole spacecraft. Any practical spacecraft is going to have the crew quarters be only a small percentage of the mass of the ship. The rest is the nuclear engine, the propellant tanks full of many tons of hydrogen slush, the heat radiator wings, onboard manufacturing and cargo bays, lander storage, weapons...basically everything that isn't the crew's sleeping, exercise, eating, and office work areas. Anyways, all that stuff would have to be designed to tolerate the additional stress of being rotated. That makes everything else on the spacecraft heavier and lowers your mission delta V by a lot. It also increases your fuel consumption, and even in the far future, propellant consumption costs you money even if there's asteroid or lunar propellant available. So it makes sense to have the crew quarters rotate, and yet you would be able to climb into the low G sections that are pressurized whenever you need to. All the heavy "industrial" equipment on the spacecraft would probably be in low g because it takes a lot of structure to spin it, while the "residential/commercial" zones of the spacecraft would be in the centrifuge. (by commercial I mean "office workspace", not literally commercial)

Yeah that would work. So the magnets are "pulling" the oil perpetually back into the groove, so the pressure of the atmosphere on this oil layer doesn't gradually shove it out of it's slot. Oil is basically impermeable to air, it would be low friction. Only problem is if it boils in a vacuum and so you constantly lose oil to outgassing.

So I'm hearing you guys. The problem is the flexibility of deployment. You need something you can bolt to something else the player can stick together from modular pieces, like legos. A cylindrical mining bore that you can mount in a cylindrical hollow piece that becomes a square works for this. You'd need a terrain engine that lets you subtract cylindrical pieces from it, but I've seen several engines that can do this, so it's possible. I don't quite know how you'd realistically deploy a bag around the asteroid. How would you control where it went? Where would you stick the pieces? Just hard to imagine.

So there was a proposed "Nautilus X" module that would be added to the international space station so that centrifugal gravity experiments on humans can be performed. As a side note, this is kind of critical - any proposals to colonize the Moon or Mars need to know if humans can live in reduced gravity long term without going blind or other show stopper problems. There's just one teensy problem. See that spinning ring? And then that non spinning section that connects to the ISS? The ring part is going to have a circular "sleeve" that goes over some kind of bearing. It must turn, so no hermetically sealed connections. What stops air from just leaking right on out through this sleeve?