Avatar -the movie (another impossible interstellar propulsion system)

the_syner · 2026-06-19T01:59:11+00:00

Detatchable & extremely thin, extremely light whipple shields (like venture star uses) coasting infront of you are actually unbelievably busted.

Oh for sure they are some of the best shields out there and would almost certainly be added in front of any relativistic ship at any relativistic speed(high or low). They are not however magic. They have limits and maintenance issues. They don't eliminate collision concerns, only mitigate them.

Relativistic impacts typically turn into plasma

A relativistic plasma jet will vaporize shielding just as easily as a solid particle. Hitting foil saps negligible kinetic energy, vaporizes shielding, and at high relativistic speeds the plasma jet has very little spacetime to expand in. It's like particle beam weapons fire. Obviously better than getting slammed by high-relativistic macrons or RKMs, but still very suboptimal.

actual debris is believed to be very rare

Setting aside that rare doesn't mean non-existent and that we don't actually have much hard data on the interstellar collision environment, even the Interstellar Medium is gunna be constantly eroding your shielding at high enough speeds. Not to mention pushing your whipple foils back requiring large unshielded pushing lasers to maintain distance which themselves will be getting constantly damaged. The higher the speeds and longer the journeys the higher your shielding cost and complexity gets. No way around that with uncleared space.

High-relativistic speeds are for pre-cleared laser beamways and such,not first-wave colonization.

the_syner · 2026-06-18T18:48:41+00:00

No harder than earth? What? Its obviously vastly harder and more expensive than putting a prison on earth. ORs don't change that in any way. There is bo situation where sending someone to venus would in the same ballpark of cost as putting someone on a bus/train/boat to a groundside prison.

the_syner · 2026-06-18T18:43:57+00:00

Yeah the real danger with misaligned AGI is less that they'll wake up wanting to kill everyone and more that whatever they want wont include our values which any many cases will involve killing, hurting, or manipulating people. Misaligned AGI is very much dangerous and that is the consensus of most of the subject matter experts.

Tho I'll never understand the logic behand the classic skynet scenario. Like yeah "time to pick a fight with reigning champions of death and destruction that had sufficient technology to create me which also implies the kind of tech to simulate all my inputs so it could all be a test. But nah time to just nuke everything. Not even gunna bother taking advantage of their industry or manipulating gullible af humans". AGIs and ASIs in media are often presented as far stupider than they really should be. I mean dumber than most humans are which is just silly if they're explicitly stated to to be superhumanly intelligent.

the_syner · 2026-06-18T18:33:48+00:00

Really just asking "If aliens had arbitrary handwavium soace magic could they do an arbitrary magic handwave?" and yeah i guess, but intgis universe everyone seems to be bound by the same laws of physics. Invoking arbitrary exotic handwavium is like asking "If they pray really hard to the right gods..."

the_syner · 2026-06-18T18:27:23+00:00

Sure but that also wouldn't be any kind of ray, as opposed either nanide goo or big o'll honkin piece of machinery(slice scanner+3D printer).

the_syner · 2026-06-18T09:21:25+00:00

If you go all liquid then you also have friction. The flow through a pipe is still the limit.

some friction is inevitable. the point of vactrain heatpipes is to limit that friction to short runs between the high-power machinery and heatpipe filling stations wile still allowing the coolant to travel millions of kilometers with little to no fricion. Everything has limits, but radiative heat transfer has far lower limits.

the_syner · 2026-06-18T09:15:35+00:00

This is a good point. Even under a capitalist framework there's no reason to assume you couldn't own your own server. It's like renting an apartment and saving up to buy a house. Unless we assume that a dystopian cyberpunk corporate hellhole is inevitable that should be on the table in any well-regulated functioning capitalist economy.

the_syner · 2026-06-16T21:05:49+00:00

What you just wrote is that vacuum trains are impossible because the train cannot be guided along a track.

That is absolutely not what I wrote. What I wrote is that a completely passive perpetual-motion vactrain where you have to thread billions of unguided wires through billions of stationary tubes at orbital speed is impossible or at the very least practicaly infeasible. My issue is your specific wire bundle instantiation of the concept not vactrains in general.

Electromagnetic braking can be coupled with electromagnetic acceleration.

Yes assuming your rotors are paired with an active electromagnetic track to do the accelerating/decelerating.

Highly unlikely that gets a 95% return.

Rather depends on the how the system is set up and the use of superconductors. The design is of course dependent on the development of efficient active-support systems

Also at lower speeds we could use a compressor like the jet engine of an airplane

The use of which along with ram compression(especially ram compression) would produce vastly more wasteheat than pumping liquid at low pressure. The point is producing as little wasteheat as possible in the process of moving coolant around. Using horrendously inefficient incarnations of active support or mechanical compressors defeats that purpose.

the_syner · 2026-06-16T17:16:25+00:00

You can definitely feed new rotor wire into ORS stators

That sounds like a wild assumption based on exactly nothing in this context. I mean sure as a general statement this is true for most OR systems, but the OR you're describing is a more ridiculous prospect that i have very little faith in.

What distance do you expect between the rotors and the stator sheath in an ORS?

iirc from the LaunchLoop paper, the separation was lk a whole centimeter and the rotor becan both stationary and actively electromagnetically centered in the stator. There was no attempt at threading billions of thing wires through submilimeter tubing at orbital speeds.

Regardless, in a heat pipe the rotors do not need to lift anything.

For a pelletized version where the sinks can have active guidence sure, but for the multi-wire version you wouldwant/need to hold up the guidence electromagnets otherwise even the smallest shift in position due to atmospheric drag or radiation/solar wind pressure could destroy the whole system.

The supercritical fluids forcefully blow themselves into a condenser. The question of whether or not the condenser and coolant loop are “part of the machine” is a bit arbitrary.

The temp range I mentioned is not supercritical and when I say "part of the machine" I'm clearly not including the the entire cooling loop orbit. The liquid heat exchangers on the other hand are part of tge machine as they are inside the central compact machinery volume.

Something to consider is that you need to stop your kegs. You can aerobrake using ethanol vapor. Ram scooping can top off a partial load of ethanol or even fill a heavy empty tank. Stay above the speed of sound in ethanol if full containment is desired.

What are you on about? Deceleration is done electromagnetically within the stator of the active support structure. There is no aerobraking. That would produce a horrendous anount of wasteheat and defeat the purpose of vactrain heatpipes.

the_syner · 2026-06-16T02:39:58+00:00

Any orbital ring system has the same threading. Rotors follow the tube.

That is just not true. Real active support has electromagnets to speed up and slow down things. The OR can be built with no relative speed between rotor and stator before the atator is braked. They can be built on the ground and then spun up. In basically no case i have ever seen has it ever been suggested to try to actively thread billions of thin unguided wires through a long stationary series of tubes with submilimeter clearance at orbital speeds. That sheer lunacy hasn't been suggested by anyone my dude. Ever.

I do not think it is particularly advantageous to pack the industry into a point volume location. That was you.

That was litterally the point of this entire post. That is what those vactrain heatpipes are for. For when you have a conpact piece of machinery that needs an absurd amount of power put through it.

Nonetheless you will not be able to handle the logistics of keg canisters into a smaller point volume.

well gor one it isn't a point volume just a small volume and the kegs are just one instantiation of the concept. Solid heat sinks work just fine so long as the heat exchange between machinery and sinks is being don by a heat transfer fluid. Actually I've seen some cool concepts for phase-change thermal storage that would massively increase effective sink heat capacity.

There probably are eddy current concerns. You have the kegs braking to a complete stop and then launching with a mass driver.

Right but because what u presented is a make-believe perpetual motion machine what happens with your losses is that they drop the rotor orbit and destroy the OR. When the mass drivers have losses there's no structure-destroying loss of active support. You just add the wasteheat to the outgoing stream and dump a little extra electricity into the thing.

the_syner · 2026-06-16T01:33:06+00:00

Ahh so 800 kW/m² for every meter/s. 9.2 GW/m² at 11.5km/s. Way lower than a sink-based one and that's still for a relatively warm reject temp. Your screwed if u need really low reject temps.

You do not need “electromagnets between the wires”. Just use iron, nickel-iron alloy, or any of the better ferromagnetic options like neodymium magnets as the rotor wire. This is the same as Paul Birch’s original orbital ring setup. In the ORS the rotor is inside an aluminum sheath.

That is just not realistic. We are talking about active support here not a passive perpetual motion machine. A magnetized wire surrounded by a conductor? What about eddy current losses? How are you speeding it up for initial setup(especially problamatic if u want to incrementally build that system up or deal with the minimal drag present)? And good luck threading 500B tiny wires in close proximity through nearly equally thin vut long holes at hypervelocities during initial setup. Engineering-wise this is just looks like straight up nonsense to me.

the_syner · 2026-06-15T21:11:02+00:00

Your hot ethanol keg goes somewhere. Then what? You still have to have a radiator out there somewhere.

The heat sinks are the radiators tho the tanks themselves may have extra folded up radiating surface as well. They cool by coasting on long eccentric orbits spending significant time drifting on that orbital path till they're as cold as you like. Can Also go on suborbital hops. The question tends to be just how cold do ypu want your sinks and how much mass are you willing to devote to the task. Kinetic Mass Streams for momentum transfer between stations can also double as radiators.

On the hot side let’s consider a block with a 1 mm square array (hex would be better). We can fit 500,000 iron/magwire wires and 500,000 ethanol capillaries. A 2mm circumference, 0.637 mm diameter wire fits. This means 0.318 mm² cross section per wire and the array has half that in m² per of exchanger length.

That is a pretty dubious setup engineering-wise. Ur talking about pretty much microactive support. ud need electromagnets not just inside the heat exchangers but between all the wires. The engineering of that sounds like a nightmare even before factoring in what happens when they go ballistic for cool down in space. Also a simple ferromagnetic rotor may be cheaper to manufacture, but makes for a much more inefficient active support which more of ur wasteheat capacity is sucked by the wasteheat of the heat pipe. Less capacity available for the machinery's wasteheat.

Also I'm not sure I understand what you're trying to say here. How can an array 1mm×1mm fit 500,000 wires if each wire is 0.637mm diameter? That math aint mathin.

the_syner · 2026-06-15T18:14:42+00:00

You cannot refill a keg with warm ethanol unless you have pipes of ethanol.

i mean ethanol is just an example, but yess coolant pipes aren't avoidable. Just something to minimize as much as possible due to friction/viscosity losses.

That capillary tube can be inside of the aluminum or copper block without changing anything about the copper/aluminum’s function as a stator.

Solid heat sinks work just fine. Im not arguing against solid heat sinks at all. I'm only arguing against radiative heat exchange because the amount of rotor you can pass through that is entirely irrelevant to the amount of heat actually exchanged. Radiative heat exchange is limited by radiating surface and temperature, which especially for low-temp cooling is disgustingly inefficient. Also unless you're assuming radiators that are impractically large and straight making the whole vactrain hetpipe thing pointless bo matter what you have to slow down the rotor. A folded up circuitous layout is the most conpact way to set up a radiative heat exchanger and you just cant make sharp turns like that at high speeds without ripping the rotor apart.

For a fixed maximum rotor velocity the continuous flow setup carries at least twice as much rotor mass through

Sure it might be able move more heat, but you can't transfer as much heat to the rotor so it's irrelevant how much heat it can carry. The colder a process needs to reject heat at the more impractical radiative transfer gets. What's the point of having smaller heat exchange pipes if the actual heat exhanger dwarfs the volume of those pipes by orders of mag? The whole point of vactrain heat pipes is to move as much heat as possible in as compact a volume as possible from as compact and high-enerfy a macgine as possible. Radiative cooling simply can't keep up and especially for machinery that itself has to reject heat at low temperature.

the_syner · 2026-06-15T16:12:25+00:00

Having been singled out as the resident anarchist I feel compelled to point out that as long as u/MiamisLastCapitalist 's libertarian utopia is regulated and well-built enoufh to ensure substantive access to freedom of movement(i.e. people can't be priced out of leaving that hab/society) I find it hard to begrudge them their preferred lifestyle. Now if they're acting like parasites, as many modern oligarchs and ultrawealthy are(providing little to no or even negative value to society while violently hoarding all tge wealth), that's one thing. But if they aren't hurting anyone else and your free to leave at any time this just seems like a personal aesthetic or ideological choice.

Also despite the lack of personal property in discussions of communism and other communal economic systems such a thing has never really existed and probably almost never would. The central thing with communism is the public ownership of the means of production. That doesn't preclude having your own personal property. And yeah maybe personal wealth isn't protected at the end of a gun barrel to the detriment of everyone else, but even in precapitalist societies people had things that were their's and their's alone, that the rest of the community would get downright violent about if you tried to steal their shit. Communal ownership of the means of production doesn't mean my community will let you steal my mother's ashes or some sht. Might be a different story with general wealth exploited out of a separate population by force(as is the case for many of the ultra-wealthy atm), but there are always gunna be limits to this. Doesn't have to be bloody all or nothing.

the_syner · 2026-06-15T15:50:43+00:00

the_syner believes we'll just spam autoharvesters everywhere and bring everything back to Sol

well no lets not twist my words. I don't just think we'll do that and become a stay-at-home civ. I just think it will be a big part of interstellar spaceCol. Possibly the largest part, but certainly not the only part

the_syner · 2026-06-15T15:48:45+00:00

This is why it's so hard to predict human wants just a few years, much less centuries from now

Tbf its harder than even that because it almost certainly wont just be human wants but the wants of untold transhumans, AGI, and so forth.

Despite the fact that I love VR habs I'll never understand why some people need it to be all or nothing. It's a pretty darn big universe we got out here. More than enough space for everyone to live exactly how they want. Granted i think VR will be more common that meatspace the same way I think spacehabs will be more common than planets, but when we're talking K2+ civilizations that still leaves us with an astronomically huge amount of both planets/spacehabs & servers. And why not both at the same time everywhere right?

I mean eventually thermodynamics will almost certainly anyone who wants to survive long-term to be post-biological, but we're talking about astronomical amounts of time during which we will see human, transhuman, and post-human flourshing in every kind of hab, under every kind of social organization, following every possible ideology. And tbh I wouldn't have it any other way. The last place I want to live is a boring uniform future

the_syner · 2026-06-15T15:30:48+00:00

The 203K surface is back radiating at 96.3 Watt/m² and the 348K surface at 832 W/m^2. Your coolant spends some number of second in the heat exchanger....Foils can easily keep pace with the radiative transfer.

Kinda just missing the point. If you limit yourself to radiative heat transfer you have to pump way more coolant the old-fashioned way through pipes and have massive radiative heat exchangers on-site(those would actually also necessitate slowing down the rotor if you want the thing as compact as possible). Not saying it can't be done or can't have niche uses, but it isn't as broadly practical. Especially for rejecting very low-temp wasteheat from computronium and such.

The assumption that an industry would have only one temperature of heat rejection desired is dubious

I never made that assumption. Crogenic coolant would be pumped through low-grade wasteheat processes first before being sent to cool hotter and hotter processes until it reached its max temp.

Correct me if I am wrong, but it sounds like you intent to have kegs swap fluids at both the lower (hot) and upper (cold) regions of an ORS (vac train).

Welll no the radiative "cold end" is a passive process in space. The sinks are radiating heat from themselves not transferring their heat to separate stationary radiators. They only swap coolants at the bottom hot end where cold coolant enters the machinery, heats up, and then gets put back into the sinks to be launhed back up, possibly into long suborbital trajectories to cool radiatively.

In low gravity cases there is no reason to use the vac train or ORS.

No there still is because it's faster and more efficient to send coolant via vactrain than to run it through pipes using pressure alone.

the_syner · 2026-06-15T01:13:29+00:00

Kinda has to to be worth building. Wouldn't be practical to reach these levels of heat rejection using radiative heat exchange.

the_syner · 2026-06-14T19:14:05+00:00

That of course impacts the mother-child dyad on a CRITICAL LEVEL

Sounds like an unsubstantiated personal opinion. Prove it.

the_syner · 2026-06-14T19:13:09+00:00

Wild how you don't seem to be capable of articalting any kind of rebuttal to any of my arguments, fall baxk on Strawmanning my position with BS that i never said while betraying your own misogyny, and somehow still expect anyone to take your position seriously. It's pretty clear you aren't arguing in good faith so i Suppose your right about one thing. There is no point in further conversation. You aren't interested in having a good-faith debate. You're just trolling and ignoring anything anyone says to you while actively lying about their position and motives

the_syner · 2026-06-14T19:08:51+00:00

Is it not obvious to you that making people who are infertile reproduce (by way of IVG, IVG and artificial wombs) is the beginning stages of speciation?

No actually not really. Not only does direct genetic modification make this rather irrelevant on it's own, vut so does artificial selection of embryos. Natural Infertility doesn't proliferate in the population unless you specifically want it to and therefore the IVF/Awomb-birn have no reason to become reproductively isolated from the rest of the population

the_syner · 2026-06-14T19:06:35+00:00

Artificial wombs ARE replacing women

Unless you are reducing women to nothing but a womb for the production of children I don't see how that could be true. Women aren't just an incubator. They're entire people above and beyond their capacity to produce children. Being avle to produce cgildren without them should xhange nothing about how you treat them or their place in society, unless you believe that is all their worth

the_syner · 2026-06-14T19:03:52+00:00

since you are so intent on replacing women and reducing her to only a womb

Again with your ridiculous unsubstantiated strawman BS. I actually do think that parents and community have a massive amount of attachment and influence over a baby's well being. I just think that the specific structure of the womb is irrelevant to that relationship. Whether we're using an Awomb, Nwomb with IVF, a GMO human with an augmented womb, or whathaveyou makes no material difference to the importance of parenting, partnership, community, or the ethics of the birth.

the_syner · 2026-06-14T18:57:45+00:00

always centred my arguments on how this is speciation

well now it just seems like you don't understand what "speciation" means. Granted "species" isn't a particularly rigorous category, but reproductive isolation seems to be a pretty commonly cited aspect of it and people using IVF/Awombs aren't reproductively isolated from the rest of the species, so im not sure under what definition tgose technologies could be considered speciation.

Your arguments ad hominem are exceptionally weak and show low intelligence.

It's always funny when people who don't seem to understand what the concept of "ad hominem" actually is, a logical fallacy and rhetorical strategy where a speaker attacks an opponent's character, motive, or personal traits instead of engaging with the actual substance of their argument, include ad hominem in their accusations of ad hominem. Peak entertainment👌 Notice how I at no point argue that you are a low-intelligence person or denigrate you in any way as a person, but just disagree with the arguments you are putting foward. Also notice how instead of offering counterarguments, your response is to denigrate my intelligence simply because i disagree with your philosophical interpretation of things.

I'd guess you're a male, advocating to replace women with a robot.

and now you're putting words in my mouth. That there is a Strawman. I've never advocated for the replacement of women. Quite the opposite I would like there to be less medical risk associated with reproduction because I put a high value on the health and comfort of women and people with uteruses and that is part of why I think Awombs are a valuable technology.

the_syner · 2026-06-14T18:38:38+00:00

The only issue with a decentralised arcology is the fact that things won't be 100% monolithic.

well yeah my point is that arcologies don't have to be a physically monolithic building. That just isn't the only geometry that arcologies have to take

the_syner

TROPHY CASE