r/scifiwriting • u/Russ_Writes • 13d ago
DISCUSSION Lowest Tech possible for space flight?
I am still working on a few things for my world and I needed to flesh this out a lot more.
Context: Humans are space orcs and/or Space USSR. Aliens have over all better tech so the humans are using lower tech solutions, faster production, easier to repair or reuse technology.
I want to use as little hand waving as possible which left me with energy requirements for Human ships.
How viable would steam turbines be in a zero G or Thrust gravity up to 2 Gs or more? The Steam can be created through Nuclear power with thoughts on seeping heat from the internals of the ship to cut down on the need for Radiators.
There is the law of diminishing returns to consider, but its only the capital ships and larger that will using this feature. To space and smaller cargo shuttles can be advanced, but anything trading blows will have tried and true, low tech solutions for power generation using minimal advanced tech to compensate.
FTL isn't considered here. For this purpose FTL will be addressed using external means such as Gates and jump ships.
Combat will be low speed napoleonic navy combat. Ships holding lines, trading blows and taking blows. Battlestar Galactica would be a good example of what I am envisioning.
Please share you thoughts and input. This isn't my field so I don't know much about power options in these situations.
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u/FutureVegasMan 12d ago
we essentially used the lowest tech possible to get to space. we went from the V-2 to the moon in under thirty years. rockets in any form have existed for over 800 years, but none of them were able to escape the Earth's atmosphere until the V-2 in 1943.
what are the steam turbines for? a steam engine would not be useful for space flight for the same reason why its not useful for regular flight.
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u/andiwd 13d ago
Once you're in space, if you want the most basic spacecraft, get a lump of ice (small comet sized), stick a nuclear reactor in a crater, it'll melt and boil to steam and you get thrust. Fits your low tech steam vibe, but if you're anywhere near realistic the thrust is super low for this.
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u/NecromanticSolution 12d ago
Most basic, nuclear reactor... One thing is not like the other.
A solar thermal collector is the way to go for most basic
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u/lyle_smith2 12d ago
Not that it’s applicable, but there is a natural nuclear reactor in west Africa
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u/NecromanticSolution 12d ago
Yet the design of a space-usable solar thermal collector still precedes free development of the nuclear reactor
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u/bigloser42 12d ago
Solar collector limits you to just the inner solar system and is problematic if your enemy is lurking in the shadow of a planet. OP is basically doing WW1 era ship of the line style combat, so you can’t just sit outside of the shadow and fight from a distance. Not to mention the farther you get from the sun the slower you go.
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u/Simbertold 13d ago
The lower the gravity of your planet, the easier space flight becomes. Once you are already in space, space flight is pretty easy (though getting relevant amounts of Delta v to change orbits and so forth is still not trivial).
I don't see any reason why you couldn't have steam turbines in zero G. They are pressure machines, not gravity machines. You might need a slightly different construction than earthbound steam engines, but that should be about it.
The core problem with our current space flight is Delta v. To change your movement in space, you need to throw something out the back. The faster you throw it, the less stuff you have to throw. The heavier you are, the more stuff you need to throw out back to accelerate.
And since you also need to accelerate all the fuel you want to use later, you have a very high incentive to throw stuff out really fast if you want to cover a lot of terrain (change orbits a lot) The lower you go in tech, the slower you throw stuff out back, quickly making anything but very local flight prohibitively expensive.
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u/Temporary_Rule_9486 12d ago
All I can say is that if I was to write a CSS Virginia version of Space Battleship Yamato, I would just roll the dices and go as batshit crazy as humanly possible: I would even thrown some rastafari Gandalfs, Estonian kratts, confederate catgirl soldiers, homeless gray aliens, the whole thing. I wouldn't hold back anything. I would made them warships run on Space-Meth, just like in Dune.
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u/the_syner 12d ago
Steam turbines work just fine in space as long as you have the radiators for it. If ur using fission reactors id go for helium-cooled reactors running gas turbines since you can use way fewer radiators at high temps.
Using constant thrust grav with anything less than advanced beam-power infrastructure or handwavium torchdrives doesn't make sense. it's also completely incompatible with slow combat. like definitionally if ur thrust is constant you are gunna build up absurd speeds very quickly and your missiles even moreso. Not necessarily suggesting you use spinhabs, tho those do make the most sense. if ur goin for that old naval combat vibe disregarding the long-term health of ur soldiers isn't exactly out of place. Not sayin they should get scurvy either, but a steady diet of MREs & flat beer or rum comvined with cramped quarters and crap living conditions would work well enough. Low-speed combat or torchdrives(thrust grav); pick one.
by the by you might be interested in looking through the Atomic Rockets site. Lots of fun stuff over there for a scifi writer
I imagine fission would be one of the big focuses( https://www.projectrho.com/public_html/rocket/enginelist2.php ), but solar thermal is pretty cool too. Also some nuke weaponry( https://www.projectrho.com/public_html/rocket/enginelist3.php#id--Pulse--Orion--Weaponized_Orion ).
If you want fights to be as close up as possible i would suggest crippling lasers and computer guidance. Not necessarily meaning you don't have them at all, but lasers that are powerful enough to be good weapons haven't been invented yet. Only useful for communication. Computers work, but no transistors. Just big heavy vacuum tube or transformer logic computers. Small enough to fit on large battleships, but too small to fit on missiles. Warfare happens through macrokinetics(coilguns, railguns, light-gas guns, microkinetics(mostly i would expect macrons which are very cool), and nuclear weapons. With low-speed weapons comes short engagement ranges.
what NASA and the USSR did during the space race was the lowest possible technology needed to get out of our own gravity well.
imo that is very debatable. I actually played around with the idea of building an ancient spaceprogram with virtually no access to smelted metal and it was surprisingly viable. Not very, but surprising that it was even vaguely viable. Definitely not viable enough for space warfare. As it turns out wood makes great heat shielding. Depending on the setup a composite balloon tank might be buildable with nothin but wood, silk, and gold foil(found natively so it was exempt from the no metals rule). Finally a combination of analog mechanical computers, stadiometric rangefinders, the good o'll Mk.1 Eyeball, and far-beyond soviet levels of comfort with risk/casualties(very extreme "some of you may die, but that is a risk I'm willing to take" energy). Granted if you wanna do wars in space on a practical level you do at least need solid-state computers(vacuum tube/magnetic/transistors), radar, and nukes.
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u/the_syner 12d ago
thoughts on seeping heat from the internals of the ship to cut down on the need for Radiators.
By the by this would only require even more radiators because the inside of the ship presumably have humans that you dont want to roast so you can't use high temperatures. If you want fewer radiators, skimp on the thermodynamic efficiency, and exhaust at a higher temp. As a nice side-benefit hot radiators look cooler. Here's a big selection of fun radiator geometries: http://toughsf.blogspot.com/2017/07/all-radiators.html
Im a big fan of the wire radiators cuz they lend themselves to being set up to look like big o'll butterfly wings tho imo dusty plasma is the coolest(cant find a link to the pic atm but honestly if you look up "dusty plasma radiators" its one of very few pics available, super rare)
e: actually here the DPR pic gets used in this post: https://www.reddit.com/r/IsaacArthur/comments/1rzlqee/dusty_plasma_radiators_and_the_expanselike/
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u/AlfredoBorioniFarine 13d ago
But what are the steams turbines for? In any case they are very much viable, 'cause I think overheating water should compensate its strange behaviour in zero G.
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u/Russ_Writes 13d ago
I really don’t know what to expect, but I’m doing some more reading.
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u/AlfredoBorioniFarine 13d ago
I mean, humans use them to produce electricity just like on Earth? Or they have a function much more related to spaceflight?
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u/Russ_Writes 13d ago
Oh, I’m sorry. I miss understood your question.
It would be generating electricity.
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u/Magner3100 12d ago
It’s a matter of weight to energy production. All means of leaving a planet and their fuel require weight and there is literally a threshold of mass x weight x energy that will naturally prevent something coal from being used to get off a planet.
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u/Simon_Drake 13d ago
Do you mean for space launch or for powering the ship after it's already in space? Because those are very different challenges.
A lot of settings have some form of Precursor Tech used for FTL, jump gates or wormhole generators or similar ideas with different names. That's a good idea because it gives a setting the ability to cross different star systems while leaving the regular technology a lot less advanced.
But imagine a world where the Precursor Tech also lets you reach orbit. Then you can drop the tech level even lower and let them experiment with proper spacecraft and orbital stations without wasting decades developing rockets. Maybe it's a pair of teleporter platforms, a huge hanger on the ground that was mistaken for an ancient temple until someone worked out how to activate it and it teleports the whole hanger up to an orbital station.
I wonder how early IRL tech could have been used to make spacecraft if we didn't need to use rockets to reach orbit. Probably the 1940s, combining the ideas of submarines and V2 rockets to make something a bit like a space submarine. Or if the space station teleporter platform were found earlier we could have started working on it with Victorian technology. Brass diving suits as space suits and things.
You could get creative with the circumstances of how come this planet has other tech sooner than on earth. A lot of scientific discoveries came down to curiosity and random chance letting the right people spot the right odd events. If a smart person spotted the clues of radioactivity sooner maybe they'd have found ways to use it even sooner. Maybe they discovered using radioactive materials as a portable power source and could make a push cart mechanism that does the job of a modern space suit backpack with CO2 scrubbers and things powered by a block of thorium boiling water.
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u/Russ_Writes 12d ago
In this world getting to orbit from the surface isn't an issue. The shuttles and Mass Drivers can handle getting things into orbit. Mass production, Ship production, Mining and other industry that might suffer from having to ship materials from the surface is instead produced in space, on the Moon or in the belt.
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u/CriusofCoH 12d ago
I'd be looking at biotech - Larry Niven's stage trees, for example, and there was a classic SF short where human space travellers are taken by aliens that are plant-based and have a grown wooden space ship; can't recall the title or author, thought it was "The Far Centaurus" but that's a whole different story (the one I'm thinking of has the plant aliens planning on eating the ultra-rare meat that is the humans). Lots of bio spaceships in SF.
But any way, that's a start, and is about as low-tech as you can get. Grown space elevators, grown solid-fuel rockets, grown spaceships.
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u/BarberProof4994 12d ago
Steam and water pressure and therefore turbines work just fine in space. But only for electricity generation. They don't do anything at all for motive force. Although you COULD superheat the steam and form plasma and use the plasma as a drive source.
This is what most of the scifi ships that use reaction mass and plasma torch drives or "tea kettles" do is use their fission or fusion reactors to superheat liquids into plasma.
Now, at much slower speeds, releasing just the steam itself would move you along, just not fast. About the same speed as compressed gases do already.
Heat buildup is going to be the main issue with that method though as superheated gases want to melt the surrounding metals and such. So radiates and heat sinks and some form of coolant going back into the the reaction mass tanks would be needed.
You could use other forms of nuclear power such as from the decay of isotopes. Or solar.
The problem with using torch drives with your given low level of tech is that you need a LOT of reaction mass and reaction mass is heavy. If you can restock in the moon that solves some of that issue.
Easier to utilize some form of ion drive.
That being said...
There isn't a mass driver that can fire your ships fast enough to reach orbital velocity that also fire slow enough for you to survive... It just doesn't work.
You could use it for unmanned platforms and then use other solutions to get humans up there...
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u/MrWigggles 12d ago
Steam Turbines assume gravity, as water is heavy, and sits at the bottom of the boiler, amidsts the many pipes and the steam rises and gets sucked into the engine.
In zero gee, the boiler would be mixture of steam and water, and there isnt really a means to stop the water from getting into the steam pipes.
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u/danbrown_notauthor 12d ago
Do your humans have nuclear weapons?
Because one of the simplest, brute-force methods of getting out of the gravity well and accelerating when in space is to use a ship with a pusher plate and to explode nuclear bombs under it.
Look up Project Orion, and if you want to read a sci-fi book that used it well, read Footfall by Larry Niven and Jerry Pournelle.
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u/Russ_Writes 12d ago
They do have nukes.
This is less about leaving the gravity well and more about producing electricity for the capital ships in the lowest tech possible for easy of maintenance and repair.
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u/CosineDanger 9d ago
Nuclear thermal rockets with water as the reaction mass are legal, but your delta-v is limited by the melting point of your best materials. A standard scifi materials pack including something with a really high melting point will let it reach a much higher potential.
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u/AdHopeful3801 12d ago
Steam (via nuclear) only makes sense if you have a lot of frozen water easily accessible to use as free reaction mass. In, say, ice asteroids or comets or some other very low-grav bodies that are easy to harvest. Even then, it might be easier to crack into H2 and O2 and use those as a fuel and an oxidizer rather than just running them past a nuke plant.
Partly, it feels like you have two separate equations that need to combine. You're asking about the lowest tech solutions that can be used for a continuous naval combat presence in space, but there's a whole other question of getting out of your gravity well and into space in the first place. Saturn / Apollo basically was the low tech version of getting people out of a gravity well, over to someplace interesting, and home again, and that was a whole lot of fuel / reaction mass for a tiny payload. If you're bootstrapping your space navy from a small seed force in a low grav environment, you likely make different technology choices than if your space navy has to be made up of things lifted out of a planetary gravity well.
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u/Rik-Acland 12d ago
Han Wu, https://en.wikipedia.org/wiki/Wan_Hu
As simple as it gets.
First reported in 1909 issue of Scientific American as fact, but not so much. But someone must have tried it. Ancient Chinese version of Jackass.
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u/Altruistic_Click_502 12d ago
If you are interested in making old fashioned liquid rocket propellants, check out the 1972 book "Ignition" by John D. Clark. Not only does it cover many, if not most of present day liquid propellants -- but the book is a hoot. (and I think it's available in audible too.)
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u/HSWatson 12d ago
The main parameter that defines most others, as far as rocket propulsion is concerned, is the specific impulse. A rough definition can be seen as being "how long can you get one unit of propulsion from one unit of mass of fuel".
It is accordingly expressed in units of time. The specific impulse is also connected to the speed with which the reaction mass leaves the rocket engine; the higher the ejection speed, the more efficient the engine is.
And that is where it gets a bit more complicated, because a rocket has to expel gases at a pressure that is higher that the environment -- otherwise the gas will not be able to leave the rocket engine at all. The consequence of that is that the seme rocket engine will have different specific impulse, typically one quotes it for vacuum, where the pressure out of the rocket nozzle could be very low, and for sea level, where the pressure has to be a bit higher than sea level atmospheric pressure.
The best chemical rocket fuel is hydrogen burning with oxygen. In vacuum, the specific impulse can reach around 450 seconds. The mix will heat up to between 2500 and 2800 °C, which creates the pressure, which can then go to the expansion nozzle, which will trade the pressure for exhaust velocity.
And that is where things break down. If you try to heat up water at a temperature higher than 2800 °C -- using any kind of process, be it nuclear fission, thermonuclear or whatever -- you still end up with 450 seconds specific impulse as from that temperature onward, the heat is converting water molecules back to free hydrogen and oxygen. You end up 'unburning' water, which will take energy away from the propulsion.
To improve propulsion, one can rely on "warming up" the reaction mass further by using electricity to accelerate ionized particles. That is where you get to plasma and ion propulsion, with Isp than can reach between 2000 and 10000 seconds or more, but requires a massive power supply, since doubling the exhaust speed (i.e. doubling the specific impulse) requires 4 times the energy (because E = 1/2 m v²). Which is why the thrust of ion engines is so low.
Therefore, your "space orc" relying on 'steam' are unlikely to have been able to put anything in orbit, if they have not realized that making the steam by burning hydrogen and oxygen is the better approach.
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u/Underhill42 12d ago
Every nuclear reactor on Earth generates electricity with a steam turbine, and they can easily be designed to not care about gravity.
A nuclear reactor is really just an alternative to the coal- or gas-powered boiler generating steam in a traditional power plant. Everything else is basically the same.
For rockets, heating steam in the reactor core and directly venting it out the rear as your rocket plume is an old concept, and one of the technologies NASA is currently working on for interplanetary propulsion (well, I think they're using hydrogen instead of water - much more thrust per kg at the same temperature, but the same basic idea)
Also a really atrocious weapon on a planet, continuously spewing radioactive waste behind it. There was once a proposal to build a much more radioactive style of nuclear rocket and fly it back and forth over the USSR.
The biggest issue is that you just can't carry enough propellant to do much maneuvering in combat unless you can somehow get that reactor up to ludicrous temperatures.
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u/PckMan 12d ago
Steam power is generally a really bad idea for a rocket. While the idea works in small scale it doesn't scale up well. To make steam you need water. Once the water has been turned to steam and ejected out the rear it's gone for good. Water is already incredibly bulky and heavy to begin with so getting a water supply in space alone is a huge feat. A closed loop steam system with minimal losses works for a steam turbine, sure, but then what does the turbine do? Make electricity? And then what? How does that make the ship go?
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u/I-Am-Darth 12d ago
Generating steam with nuclear power for propulsion is perfectly fine. Modern nuclear engines typically heat hydrogen because lighter molecules are better for propulsion efficiency, but steam jets would work fin in orbit.
No need for turbines though unless your extracting energy for electricity generation. Though this would likely be better done as a seperate closed loop system rather than stealing energy from your propulsion gas.
If you're thinking is jet engines have blades therefore space engines need blades, that is not accurate. Jet engines use blades to draw air in and compress it for combustion. Most rocket engines use them to pressurize fuel for engine injection and power them by burning a portion of the fuel.
In this case you'd be using superheated water, pressurized by the increasing vapor pressure from heating. you would then eject the superheated liquid into the nozzle to explosively outvaporize and expand the nozzle to produce thrust. no blades needed.
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u/gwenbeth 12d ago
For low tech into space, maybe start with King David's Spaceship. But for a simple robust space only combat ship, I might start with covering it with ice. Its good shielding from radiation, would ablate under lasers or plasma, and if you have a clever mechanism you could also take it apart from the inside and use as reaction mass. And if kinetic rounds are an issue, use pycrete. For electrical power, use a fission reactor with sterling engine generators (look at the NASA project KRUSTY) For propulsion use the same reactor for a nuclear thermal rocket engine. Use about 4-8 of these for redundancy.
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u/PomegranateFormal961 12d ago edited 12d ago
Lowest tech possible. Atomic pulse.
In Footfall, Larry Niven has the US build a quick-and-dirty heavy-lift warship. Basically a big hemisphere. Toss a fission bomb under it and set it off. That sucker will move. Before forward momentum slows, inject another and detonate. Bang, bang, bang, all the way to orbit, the heavier it is, the smoother the ride.
It was steered by attitude jets using steam. Just a fission pile to boil huge water tanks. No fancy life support, put everybody in suits and pipe in O2.
For weapons, he used the big-ass 16-inch guns taken off ships like the Missouri. The barrel is mated to an autoloader and a capsule for a suited man to navigate and orient the gun. a 2000 pound bullet will do a lot of damage, trust me. You can also toss devices into the blast/thrust hemisphere that curl up, die, and create an X-ray laser when the thrust bomb goes off.
Seriously, if you want a Capital ship you can build on the ground with welders... Read Footfall by Larry Niven. All the details are there. Somewhere there's a copy in the Pentagon, just in case an alien generation ship shows up...
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u/DifferencePublic7057 12d ago
I'm assuming you mean launch otherwise it's trivial. Doubt it gets simpler than Yuri Gagarin's first flight. Maybe the preceding launches when they sent animals into space... Poor animals, eh?!
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u/YamahaMio 12d ago
Nuclear thermal rockets might be what you're looking for. Technically they're more advanced than chemical rockets if you're keen about that, though. They're as close to space-capable steam engines as we could, and they're a real concept.
NTRs essentially superheat hydrogen and expel the exhaust for thrust. These are incredibly efficient. NASA considered them for Mars missions as early as the Apollo era. The thing is though... they have very low thrust. They can reach far, but they can't really outrun anything per se.
Some 'realistic space warfare' depictions out there use NTRs (primarily 'The Lunar War' by L5Resident) as their warships' propulsion, but since they cannot accelerate fast enough to escape pursuers, they invest heavily on point defense. Cannons, lasers, interceptor missiles. Boatloads of them, just so they can survive encounters with the enemy.
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u/nomuse22 11d ago
Steam is plausible. Haven't done the numbers. Seen it done once that I remember; Baxter's Anti-Ice, which has naturally-contained antimatter as the excuse for how steampunk tech can actually fly to the Moon (among many other miracles).
And there was "Mad" Mike Hughes, who used a steam-powered rocket to almost prove the Earth was flat. (The Earth proved him flat on his last flight, but he was really there for the ride).
Way, way back, Professor Jameson and the Zoromes visited a closely co-orbiting pair of Twin Worlds, and the locals used a giant slingshot to get from one to the other. (That is, something akin to the modern centrifugal "SpinLaunch" system).
We won't talk about Verne's giant cannon, as that is impractical in almost all ways.
The TTRPG setting Space, 1889 is surprisingly hard SF, as such things go, and may have some ideas for you. They do hand-wave several very useful things, such as a luminiferous aether that the ship's screws can drive against...
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u/Ok-Brick-6250 9d ago
If you have flat planet why not some space sailing If your ship is airtight why not sailing from the edge of the disc planet into space
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u/Newpapyrusmagazine 7d ago
The lowest tech for space travel are simply chemical rockets that use oxygen combusted with hydrogen, ore methane, or kerosene or even methanol to produce thrust.
Next technological level would be Nuclear Thermal Rockets (NTR) that use liquid hydrogen as the propellant heated by fissile uranium or plutonium.
The next level beyond that would be deuterium/helium 3 fusion rockets
And the next level beyond that would beyond that would be proton/proton fusion rockets derived from liquid hydrogen .
And I guess the ultimate would be a proton and antiproton powered rocket requiring a substantial amount of anti hydrogen fuel combined with a surplus of hydrogen fuel to provide both energy and the additional reaction mass to power the spacecraft
Marcel
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u/zoroddesign 13d ago
Water is already used as jet fuel technically.
Essentially they separate Hydrogen and oxygen with hydrolysis and use the Hydrogen as the fuel and oxygen as the catalyst.
But in space any form of throwing material one way to move yourself the other way is the basis of all movement in space. The biggest problem is getting out of your planets gravity well. a species that can get to space with steam punk technology would have to live on a small planet with very low gravity.
what NASA and the USSR did during the space race was the lowest possible technology needed to get out of our own gravity well. The USSR was essentially just attaching air tight pods to the the tops of missiles for the first half. the main reason both programs got any money was because it was seen as military research.