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In this scenario people are in a constant war on an infinite flat world with the geography of Antarctica's interior (but with no liquid water or hydrocarbons). Notably this world has an abundance of deposits of radioactive ore and the people are decades ahead of us in some areas like nuclear tech, as well as having shadow magic that can create very effective shielding and cheaply separate isotopes. This world experiences a universal 1 G acceleration, but while other physics are the same there's no "true" gravity. This also means that gravitational sensors can't work.

The scale of conflict means that people need to build a lot of transport vehicles as cheaply as possible and having to set up a new settlement and move isn't uncommon so it should ideally be as easy as possible to set up new factories. Not having the transport vehicle compete with military vehicles for minerals or rare components is also strongly desired here where possible.

What sort of nuclear based transportation would be best suited to cheaply transporting large amount of cargo at decent speed over Antarctic geography, if radiation weren't a concern?

For these purposes something like the Antarctic Snow Cruiser doesn't remotely cut it, the people here want way more carrying capacity and speed.

Importantly people in this world don't really need to worry about any radiation that wouldn't rapidly kill them: Due to a combination of biotech, and using shadow magic to shield against radiation and separate radioisotopes.

Shadow magic wards can also be used to shield mechanical components against radiation, but this gets costlier the better the absorption needs to be (so you're not blocking a direct nuclear strike with this).

In order to not let radiation reveal one's activity/position, people deliberately set off large numbers of nukes and fly around drones that spray nuclear fallout behind them. In order obscure their location and activities (like them using nukes for tunneling).

Propulsion options I've considered but can't decide between include:

  • Nuclear saltwater rockets (I strongly suspect they may not be practical for this application).
  • Nuclear thermal rockets (seem like a better option than the saltwater rocket, but it is still a rocket so idk, also seems worse than a ramjet because of the propellant's weight).
  • Nuclear reactor power source for electric propulsion like jet engines.
  • Ramjets which directly use nuclear material to heat up air generating thrust like Project Pluto. This option seems like it might be the most promising since I've heard ramjets are simpler than regular jet engines.
  • Nuclear steam-craft are an idea I had where a vehicle sucks up snow with a fan/scoop and then flies around over the ground on jets of steam (I have no idea how viable this would be). I guess this might technically count as a type of NTR as well.
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  • $\begingroup$ Are we only transporting stuff around Antarctica? And are we allowed to leave the atmosphere? (It's a big continent.) $\endgroup$
    – BMF
    May 15, 2023 at 1:05
  • $\begingroup$ @BMF It's an infinite plane with the terrain of Antarctica, but it's infinite. You can definitely go to a high enough elevation to reach a vacuum just like on earth. It's just there's no stars and you could keep going up forever without gravity ever diminishing. $\endgroup$ May 15, 2023 at 1:12
  • $\begingroup$ Vote for Nuclear reactor powered jet engines. The only reason they didn't build it was concerns for radiation pollution if the thing were to crash. Otherwise it would be a very simple but capable design. You can power jet engines directly with thermonuclear. $\endgroup$ May 15, 2023 at 8:32
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    $\begingroup$ If your world is infinite, what resources are your factions fighting over? Just set off in different directions and never see each other again. $\endgroup$
    – Bergi
    May 15, 2023 at 19:49
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    $\begingroup$ An electrified railroad powered by nuclear power plants? $\endgroup$
    – Sascha
    May 17, 2023 at 11:17

13 Answers 13

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First, I'll address why I think some options will not work.

Rockets

Because your world is an infinite flat plane, rockets are impractical (even if there is a 'space') - without a body to orbit around, they lose most of the advantages of going to space.

  • Nuclear thermal rockets are right out, because their thrust-to-weight ratio is far too small to take off, and they still need fuel (hydrogen, usually).
  • Nuclear Salt Water Rockets are better, but since they would likely be designed as aeroplanes (can't orbit), they would then spew tens of thousands of tons of highly radioactive exhaust into your atmosphere.† (Even if it did reach space, because orbits are impossible, the exhaust would eventually just fall back down into the atmosphere too.)
  • Lithium Salt Water Rockets are better, because their exhaust is not radioactive, but they are much more challenging to make than a standard NSWR.
  • However Nuclear Salt Water Rockets are probably not what you want - I doubt you need to reach speeds of 3% C when transporting military equipment, not to mention you would evaporate because of atmospheric heating.

†You have mentioned that it is easy to shield against and treat radiation issues in this world, but even then, unless your people are all just entirely immune to radiation all the time, it would still be better not to dump radioactive material everywhere.

Ground-based

Ground-based solutions have problems not only with infrastructure requirements, but also that damage to said infrastructure is an easy way to render them useless.

  • Trains. With apologies to a couple of the other answers, I think trains are the worst option. Look at how armoured trains have fared in warfare in the past. When their rails are damaged, they become worthless. Especially since you have asked for speed, you need very well-maintained rails (see TGV, Shinkansen, and similar).
  • Road or Off-Road: Better than trains, but slower, and (usually) unable to carry as much cargo. If the vehicle is designed for off-road work then significant damage to the road is required to stop it. However, it can be stopped by cliffs, walls, ravines, etc. A determined enemy will use all of these.
  • Hovercraft: These are generally a good option for snow and ice, because they cannot easily get stuck. Their chief disadvantage is they require fairly smooth ground. A wall or hole will stop or hinder them, and some spikes could severely damage the skirt which is essential to their operation.

Ekranoplans might be a possibility (except for Type A ones - these have the same problems as wheeled vehicles). I mention them again at the end of this answer.


Therefore, I think you are looking for an Aeroplane. And you are in luck! Such an aeroplane has already been designed:

The Lockheed CL-1201

If you are looking for speed, range, and capacity, see the Lockheed CL-1201: a proposal (1969) for a VTOL nuclear aeroplane of truly vast proportions, able to carry 12,000,000 lbs (5.44kt) and stay airborne for 41 days straight (without refuelling). Its wingspan would almost have been equal to the height of the empire state building (341m), and it was to be supersonic.

It would have used something similar to a nuclear-thermal ramjet for power, sending all the waste heat from the reactor to a set of 186 (182 VTOL, 4 flight) engines. These would operate similarly to standard jet engines except, instead of creating heat by burning fuel, they would take heat from the molten lithium metal used to cool the reactor. The advantage is that it needs no fuel other than uranium for the nuclear reactor.

This, or other vehicles similar to it, seem to be the optimal solution for your problem.


Edit:

After further consideration, I think that a Type B or C Ekranoplan based on similar principles to the CL-1201 might be an even better option, due to its increased carrying capacity and improved stealth over a standard aeroplane. However, it will also be easier to damage or attack than a standard, high-flying aeroplane.

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    $\begingroup$ I'm surprised that they proposed the Cl1201 both having VTOL and supersonic capabilities at that scale. Radiation is very much not a concern though since people have both technology and magic which can easily mitigate both external radiation and purge radioisotopes from the body. $\endgroup$ May 15, 2023 at 2:46
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    $\begingroup$ Up voted for referencing a real proposed design. A great starting point. $\endgroup$ May 15, 2023 at 8:37
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    $\begingroup$ @VakusDrake when you're able to design with UNLIMITED POWER (tm) the answer to what you select from a menu of possible features is "yes". $\endgroup$ May 15, 2023 at 20:28
  • $\begingroup$ It's less demented than en.wikipedia.org/wiki/Project_Pluto (a nuclear ramjet cruise missile) was anyway. $\endgroup$ May 15, 2023 at 20:30
  • $\begingroup$ @DanIsFiddlingByFirelight Having unlimited power and no concern for radioactive contamination makes this setting very interesting to me because it lets nuclear tech get used to its full potential in a way it never was in RL. However, like I said in my question I'm really curious about what makes the most sense to use for bulk transit, given that the considerations are very different than for military vehicles. So please give me your thoughts, and note that even burning grams of nuclear material a day isn't too demented given fallout is irrelevant and plutonium is quite cheap. $\endgroup$ May 16, 2023 at 0:05
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In a world abundant with radioactive materials, cutting-edge nuclear technology, and shadow magic for shielding and isotope separation, a nuclear-powered hovercraft-like vehicle becomes the ideal choice for affordable, speedy transport of large cargo across Antarctic-like landscapes.

The hovercraft would be driven by a compact nuclear reactor, supplying the energy required to generate lift and propulsion for efficient travel over icy terrain. Advanced reactor designs, such as molten salt reactors or small modular reactors, are known for their efficiency, safety, and scalability (World Nuclear Association, 2021). These features make them suitable for transportation vehicles as they produce significant energy with a small, lightweight core.

Traversing snowy and icy landscapes is made easy with the hovercraft's design, as it doesn't rely on wheels or tracks that may become stuck or slowed down. Instead, it uses a cushion of air, created by the nuclear reactor's power, to hover above the surface, enabling high-speed movement in difficult conditions (ScienceDirect, 2021).

Shadow magic's use for radiation shielding and isotope separation adds to the nuclear hovercraft's suitability. The shielding protects passengers and cargo from radiation, while isotope separation ensures continuous fuel supply. Compact reactor designs minimize required shielding, reducing costs.

Modularity in the hovercraft's components allows for quick assembly, disassembly, and maintenance. This simplifies the establishment of new factories and production lines in response to the ongoing conflict's shifting demands.

In summary, a nuclear-powered hovercraft utilizing advanced nuclear reactors and shadow magic offers a cost-effective, efficient, and adaptable solution for transporting large cargo at decent speeds across this world's challenging Antarctic-like terrain.

Sources:

World Nuclear Association. (2021). Small Nuclear Power Reactors. Retrieved from https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx

ScienceDirect. (2021). Hovercraft. Retrieved from https://www.sciencedirect.com/topics/engineering/hovercraft

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  • $\begingroup$ Hovercraft was also my first idea, but the extreme cold might be an issue. Apparently the most common material for their skirts is currently neoprene, which has a glass transition temperature around -45C and definitely isn't rated to the -90C that real-life antarctica can get to. Might be useable as a plot point though. $\endgroup$
    – llama
    May 15, 2023 at 18:10
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    $\begingroup$ Good news, with a nuclear reactor you can use the skirt as your heat sink (necessary for a heat engine to work anyway) and warm it to a toasty -10 degrees with ease. In fact you could probably get it much hotter, but melting the ice may not be the best idea. $\endgroup$
    – Turksarama
    May 15, 2023 at 23:21
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I can think of 3 things, going in order from most energy efficient to least energy efficient & most infrastructure needed to least infrastructure needed. Note that i'm leaning more into the move large amounts efficiently side than the speed side as these 2 things are generally incompatible most of the time.

Electrified railway with nuclear power plants

Ultimately, the most energy efficient way to get power from nuclear is large, centralized power plants. Using anything to keep you off the ground is always going to mean your going to need much much more energy that staying on it no matter how you do it. As well, electrified trains allow movement of literal 1,000s of tons of material, using multiple unit operation allows 10,000s or even over 100,000 tons at the highest end to be moved.

Speed for very heavy freight trains isn't going to be as fast as anything flying, obviously. But it's also possible to run faster trains, even on non-high speed track achieving speeds up to 200kph is doable, although there is an inherent trade off between maximum safe speed & maximum safe axle loading with tracks. For an example the Iron Ore Line in northern Sweden & Norway has freight trains moving loads of 8,600 tons at 60kph with passenger trains going 135kph.

Non electrified railway

Much the same points as above apply. Nuclear trains have been proposed irl many times & are always faced with 3 big problems, very high axle loading, safety, & cost. They are also significantly less energy efficient. It is possible but almost certainly worse than electrifying the line but it would save you the cost of well, electrifying the line. Otherwise similar to an electrified railway

Nuclear Overland Train

This is probably the least efficient & fast, but it's the only one to not need pre-existing infrastructure. Overland trains are the idea of connecting a large chain of wagons on rubber tires with a power unit to move large amounts of cargo in difficult terrain. While the only ones built irl were diesel or gas turbine powered & didn't actually work very well, nuclear powered ones were proposed. This could probably be used to move large amounts of cargo. Concepts i can find would have been capable of moving ~150-300 tons

While none of these options are particularly fast, none are particularly slow i think. However they are all very energy efficient & aside from overland trains very high capacity.

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  • $\begingroup$ Not electrified railway has the advantage in times of war, that it's hard to put the whole line out of commission by shooting down one pylon, and breaking the cable. Tracks are harder to damage, and don't stick so high so you need to be closer to damage them. $\endgroup$
    – Mołot
    May 16, 2023 at 12:13
  • $\begingroup$ land trains actually worked surprisingly well with later iterations but the need disappeared. $\endgroup$
    – John
    May 16, 2023 at 22:54
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Semi-buoyant steam airships. An infinite planar world with no liquid water should have particularly boring weather that would be of little threat to airships, and hybrid airships could land and take off from small airfields surrounded by rugged terrain that would be impassable to ground vehicles, but are more compact and can carry heavier payloads than fully buoyant aircraft.

Steam is a reasonably effective lifting gas, far better than hot air for example, with the major drawback of requiring high temperatures. A nuclear reactor would make these temperatures relatively easy to maintain, while also powering steam engines to drive lift/propulsion fans or propellers.

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Scramjets are very simple... If you can get to Mach 6. Ram Jets have a similar issue - namely you need to get supersonic for them to work. This is because they use the shockwaves to compress the air, rather than a compressor.

From a design point of view - you've indicated you want speed, but you also want large volumes of cargo. I'm also presuming that you have no fixed infrastructure (e.g. rail lines) which puts us in a bit of a quandry - If you want speed, you'll be flying. If you want Bulk, you won't be.

To put this in perspective - a single C5 Galaxy heavy lift cargo plane can carry about 127,000 KG of cargo. In NZ the Maximum weight allowed for a Truck is 46,000 KG - so it's about 3 trucks to one plane.

Then you have the issue of weight displacement on Ice and landing on ice - both of which are issues.

However I think the best answer would be...

A Scaled up, Nuclear powered Hovercraft

Something like the Russian Zubr craft which can hold 190,000 Kg of Cargo (based on my back-of-the-envelope maths). You would run the reactor at the rear and use steam pressure to drive a generator and have all the fans on the Hovercraft be Electrical.

The air cushion means that many of the issues with moving on Ice are mitigated - you aren't worried if there's a crack or a fissure, you can ride over it. We can beef up the propulsion so that we can get some speed - 200Kph might be reasonable - if we want to add some form of Nuclear powered jet, perhaps even more so.

You could even have multiple Hover-barges being towed by the main unit, which would decrease top-speed, but would provide for significant cargo capacity (several thousand tonnes of cargo)

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  • $\begingroup$ I put scramjet when I meant ramjet. I'm surprised hovercraft could carry that much. $\endgroup$ May 15, 2023 at 0:09
  • $\begingroup$ Ramjets don't need to be supersonic to function, they just are most efficient at supersonic speeds. Scramjets are specifically combustion engines, their defining characteristic is combustion in a supersonic airflow, and it doesn't make sense for them to be nuclear powered. $\endgroup$ May 15, 2023 at 3:21
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Land trains

The US military actually planned on building it, it was called the Nuclear Overland Vehicle.

It was designed to freight delivery over tundra. A giant offroad land train. Each wheel on each car powered by an independent electric motor connected to a compact nuclear plant on one car. Several iteration were built using deisel electric engines but a nuclear one was planned before the need to move so much freight across tundra fell away with huge cargo helicopters.

They could ford small rivers and the huge wheels made its displacement low enough it could drive over tundra mud or loose sand easily.

here is the last iteration actually built, the TC-497 Overland Train, Mk II which was almost 600ft long. It had a top speed with 150 tons of cargo of 20mph. The final nuclear version was expected to be several times longer.

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Upsides: offroad, not much infrastructure needed, probably the most cargo possibly without infrastructure. Great setting for a story.

downsides: slow, offroad means 20-30mph tops. That sounds slow but that is about how a fast a modern cargo ship travels.

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How about something like the Soviet TES-3? This was a tracked nuclear power station. The article provides some idea of its intended use. It could provide power for temporary settlements, but it could also provide power for other vehicles.

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Barges

Barges are about the cheapest and easiest to construct vehicle per ton of cargo. With unrestricted mastery of nuclear energy on an ice plateau, it's easy to construct canals: simply melt them! The mass of a reactor on a tugboat is much less of a problem than on land or air vehicles. A single tugboat can propel many barges at once.

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  • $\begingroup$ I think you grossly underestimate the cost of melting that ice. what-if.xkcd.com/130 $\endgroup$
    – Demigan
    May 17, 2023 at 5:49
  • $\begingroup$ @Demigan It's not practical with chemical energy, but nuclear fission yields ~a million times as much energy per gram of fuel. That makes a huge difference. $\endgroup$
    – John Doty
    May 17, 2023 at 14:13
  • $\begingroup$ as the XKCD explains you need 3 aircraft carrier reactors just to clear the snow in front of your car, to make channels and keep them open in a perpetual cold area as described would be a ludicrously expensive task. It doesn’t seem like the radioactive material is infinite in a local area. $\endgroup$
    – Demigan
    May 17, 2023 at 14:22
  • $\begingroup$ @Demigan Clearing a track at highway speeds is ridiculous. However just melting snow as it falls, and keeping the surface above freezing isn't so crazy: Pagosa Springs, Colorado keeps sidewalks clear in winter using geothermal energy. Estimate this takes ~100W/m^2. A 1 GWT reactor could then keep 10^7 m^2 clear. That's a canal 100 m wide, 100 km long. That's a bigger than naval reactors, but modest for a fixed installation. $\endgroup$
    – John Doty
    May 17, 2023 at 15:43
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Consider that any nuclear reactor will generate a discernible trail, if you have cutting-edge nuclear technology you will also have cutting-edge methods of finding trails of radioactive residue. Because of this it would be very easy to target supply lines and attack them while avoiding the bulk of nuclear military power (since concentrated nuclear-powered forces will be even easier to spot).

As such, you can go different ways:

  1. Either there's some sort of jamming tower that can cloak radiation trails, and then there can be a lot of tension surrounding this concept. If you want to advance you either take the risk of having everyone see your travel lines, or you take it slow and build jamming towers and then more conventional methods of scouting are also relevant. It's also a statement that you're intending to advance somewhere when you create jamming towers which can fuel political tension. Also, the other side can use your own jamming towers.

  2. I would suspect people would tend to avoid nuclear-powered transport vehicles because of this trail and instead use nuclear power to generate electricity, and then use electrical vehicles to transport whatever (maybe even wireless vehicles). This would be a way to circumvent the problems I stated earlier, but also creates more interesting applications for nuclear power.

Say someone destroys a power plant, now a bunch of transport vehicles will have a limited time to function until they run out of power.

  1. Maybe some factions will use electrical power created through nuclear technology, some other faction uses jamming towers and another faction uses some sort of shadow magic to cover its tracks, but it only works for a short while, then you have this aggressive faction that is based on some blitzkrieg style warfare.
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  • $\begingroup$ I actually did come up with a solution to radiation giving away your positions: Mainly that people deliberately set of large numbers of nukes and fly around drones that spray nuclear fallout behind them in order obscure their location and activities (like them using nukes for tunneling). $\endgroup$ May 15, 2023 at 16:02
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    $\begingroup$ Why would a nuclear reactor leave a trail? Most reactors are sealed. If they were not, submarines would have problems. You would have to be very close to detect the radiation itself. The most distinctive signature would probably be the heat, as all your generated energy ends up as heat. $\endgroup$ May 15, 2023 at 20:16
  • $\begingroup$ Sounds good, my idea is that factions with varying capabilities are more interesting than some standardized approach used by everyone. Didn't know nuclear reactors don't leave any trail of radiation, thanks. $\endgroup$
    – florianc63
    May 16, 2023 at 17:58
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Nuclear powered airships.

Contrary to popular belief airships aren’t made of explodium, in fact even the badly designed WWII airships would be more durable than any other modern aircraft, including military ones. The problems that they suffered were the same as with regular aircraft, except that a single aircraft crash was less newsworthy than the far harder to mass produce airships.

Airships are also well suited for the antarctic. At one point during the cold war the weather above the north pole became so cold that nothing could fly there except the airships with early warning radars.

The drawbacks of airships can be solved with modern engineering, just like most of the problems with regular aircraft at the time were solved. A hybrid airship for example uses both lift surfaces and gas to stay in the air, if it slows down it can land like a (massive) aircraft and with vectored thrust you can land more easily and controlled.

Airships also are able to carry immense loads, and the bigger they get the more efficient this gets.

The speed is also different than what you might see in the movies. The Hindenburg, a giant WWII powered airship, could cruise at 126km/h or go up to a maximum speed of 135km/h. A more modern, nuclear powered take could do much better. The resilience against storms has a rule of thumb: it can handle storms where the average wind speed is the same as the maximum speed of the airship, and that was for the poorly designed pre-modern material airships. With proper weather control and warning systems as well as more modern materials and design features these could handle most storms you throw at it, especially if you land them and anchor them.

Technically this lets you build entire flying nuclear villages if you want.

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G.E.V. A nuclear powered vehicle for operation on an infinite flat plain. The ideal craft has to be a GEV Ground-effect vehicle. Not only is this type of craft, versatile, fast, efficient and scalable. They are damn Sexy!,

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Super cheap, brute force, and only marginally difficult to control... Project Orion doable with standard earth 1960s tech. big pusher plate [with your magic shielding] lots of cargo sitting on top of pusher plate.... log small nukes out a small hole in said pusher plate and blast away. Thousands of tons of cargo moved at as fast a speed as you would like at any planetary or extra planetary distance you'd care to chose. ;-) hope this helps!

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A couple of notable points: With no hydrocarbons and an Antarctic environment, you have no plastics and little to no cloth except what could be grown in nuclear-powered greenhouses. It also sounds like metals are rare (based on your comment about not competing with the military). With constant war, fixed infrastructure means targets. If there's any kind of capability to strike across borders (which I can think of quite a few ways, given nigh-unlimited nuclear power) you will want some kind of mobile solution, not trains or canals, built out of solid metal, with the least metal possible and ridiculous amounts of nuclear energy.

I would go with a hybrid hovercraft / barge, floating tons of cargo on a bed of super-heated steam from nuclear material lining the underside of the barge, with nuclear turboshaft engines providing propulsion. If radiation isn't a concern, just pile uranium in enough quantity and thickness and it'll generate enough raw heat to just melt and vaporize the ice below.

Mind, if it gets in a crash, squishing uranium around like that might cause the vehicle to go critical. Exciting!

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