The antigrav is a bedroom-sized cube of smooth sheet metal walls encasing complicated metallic machinery inside. When switched on, it generates an anti-gravitational field enough to lift a stone building like the Cathedral of Notre Dame to an arbitrary height in the air.

This machine consumes roughly as much coal as a early 20th century steam train locomotive, and works in a similar way on the surface, spewing as much smoke and steam during it's operation as the steam train locomotive, although it's principle of operation is fundamentally different, a truly unique invention. If the steam locomotive train stops upon ceasing coal, and just sits on the railroad, the antigrav machine stops and starts falling down, with everyone on it.

Hence any airship, or flying building which has at least one antigrav machine, must make sure that there is enough coal for it's operation, and also that this machine is well protected against external bombs and missiles.

Having such antigrav machines, what kind of military uses could it be used for? I was thinking of maybe huge flying aircraft carriers, or battle ships, but in the sky. Perhaps even flying castles with lots of howitzers. Multiple antigrav machines can be placed at various parts of the structure.

In this alternate history, the technological level is similar to OTL 1950s, excepting the presence of this new invention. There are planes and helicopters, and there are no nuclear bombs in this world.

What would be possible military uses for antigrav machines in this world, and what would be their impacts on warfare? Keep in mind that the military men of this word are not always exactly sane, having practically unlimited budget, and would have no qualms about building big, ugly, and fearsome, but not necessarily practical and effective monstrosities.

  • 1
    $\begingroup$ This seems like a very broad question if you're asking us to brainstorm flying aircraft carriers and castles. It's also underspecified, depending on how difficult it is to manufacture and how much power it takes to run, you'll have vastly different usages. $\endgroup$
    – sphennings
    May 6, 2022 at 2:46
  • $\begingroup$ @sphennings Sure, give yourself the opportunity to come up with creative answers. It works basically like a train steam engine, taking roughly as much coal. It does not take any "power" other than coal. It is roughly about 10 to 20 times more difficult to manufacture than a train steam engine, but the military has an unlimited budget. $\endgroup$
    – Galaxy
    May 6, 2022 at 2:49
  • $\begingroup$ The military doesn't need an unlimited budget - this is a perpetual motion machine (like so many anti-grav concepts) that can be used to make a fortune running electric powerplants anywhere. The invention would fundamentally reshape the world, which means that it is easier to write about what isn't affected than what is. $\endgroup$ May 6, 2022 at 2:59
  • $\begingroup$ What are the limits of the "arbitrary height in the air"? Can something be lifted out of the atmosphere? $\endgroup$ May 6, 2022 at 3:02
  • $\begingroup$ @KerrAvon2055 It works only up to a certain height though. The antigrav machine only works in close proximity to a planet, meaning that it can't be taken out of orbit, or into the outer space, unless helped by rockets. The antigrav machine is useless in outer space. Current ships powered by antigravity can be taken into the upper atmosphere, where the air is too thin to breathe, but more sophisticated antigravs that could take ships into the lower Earth orbit would probably be at least half a century away. $\endgroup$
    – Galaxy
    May 6, 2022 at 5:21

3 Answers 3


Since antigrav violates the Laws of Thermodynamics, it can cleverly be abused to simply obliterate enemy concentrations (or whole cities). That's the real likely use: The loopholes of your antigrav physics make weapons of mass destruction, replacing the non-existent nuclear weapons as a strategic deterrent.

But let's put that aside and look at the spirit of the question.

Seem like you have invented the flying cargo-ship, and thereby revolutionized military logistics.

The initial effect is that seaports are replaced by cargo airfields adjacent to the storage depots. Without days lost to transloading at seaports, resupply of ammunition, fuel, equipment, food, and spare parts can move much faster. Also, airship travel might be faster than the 15mph-or-so of cargo steamships (dirigibles in the 1920s averaged about about 3x faster). If supply air-routes can be shifted to avoid threats in a way that sea routes sometimes cannot (pesky land in the way), air logistics might also be more reliable.

In turn that suggests that military units may updated equipment faster, may be more flexible when circumstances change, and may be able to tolerate lower reserve stocks of fuel and ammunition. Items in transit will be less subject to pilferage and misrouting. Soldiers will have higher morale due to better and fresher food and faster mail delivery.

At the operational level, supply lines won't run to distant seaports, but to closer airfield-depots. So fewer transportation units and other logistical slice units will be needed.

It's possible that you are not thinking about dull logistics at all, but are instead envisioning flying buildings of tactical death -- sky battleships twisting among the hills and raining fire onto the ground below. A lovely image...except that the folks on the ground also have artillery and aircraft capable of sinking battleships (sea or air) so you'll need extra miles of standoff distance, and then the fight becomes a lot more tedious and loses the poetic luster.

  • $\begingroup$ How would the defendants take down such a sky battleship anyway? Probably more importantly, even if they go manage to damage a sky battleship to the point that it's antigravs no longer work, and it starts falling to the ground, how do you prevent it from falling right on top of your head? I imagine that a sky battleship can be positioned right over a fortress or a city, bombarding it and disembarking helicopter crews. And if the defenders would manage to shoot it down, it would fall directly on top of the fortress or city, potentially blowing up. How would the defenders deal with this? $\endgroup$
    – Galaxy
    May 6, 2022 at 5:25
  • $\begingroup$ A note about the speed of airships: even the Hindenburg could reach 120km/h (393700 feet per hour). $\endgroup$
    – Demigan
    May 6, 2022 at 6:21
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    $\begingroup$ @Galaxy you shoot them before they are on top of you. It's not like they will be sneaky. Also, at sea there's probably only a few dozen ships max firing on you, so at most a hundred (although big) canon. On land you can have thousand of artillery pieces firing on you. With a lot more precision because there's no wave. Also, the crew might not feel suicidal, and you can just move from under ... fixed position were already less of thing by WW2. $\endgroup$
    – Cthu
    May 6, 2022 at 10:18
  • $\begingroup$ @Galaxy 1950s is when modern guided missiles first started to come into service. The existence of anti-gravity flying ship would provide an incentive to quicken the development of long range anti-(flying)ship weaponry $\endgroup$ May 9, 2022 at 13:25

There is a non-arbitrary height past which early planes were not super useful. If you can lift up defensive bunkers around cities to the point where they can't be easily bombed and they can fire off defensive weaponry against oncoming planes from a distance, it could affect how useful air strikes were as a strategical option. Air-to-air missiles were being developed and perfected during the 50s, so a bullet-proof air defense on the perimeter of a bombing target could push development of that technology. People trying to make the bombing runs would want incendiary missiles they could use to take down the floating defenders so that bombers could complete their missions, while defenders would want long range homing missiles to snag even the best pilots before they could get a shot or a bomb off.

As far as offensive uses of the technology, well, just taking a navy battle cruiser and making it float would probably be the best and easiest use of the technology. It would make earthworks and beachheads more or less obsolete if a bunch of cruisers could just rise out of the water and theoretically float on to land. Of course, they wouldn't want to float through defensive fire, so they'd shell the beaches first. This wouldn't be hard, though; Airborne ships would be harder to target out of the water, but would have an easier time targeting land-locked defenses from farther away given extra height. Meanwhile, giving defenders floating bunkers would have diminishing returns, since it would still be hard to hit the ships. Instead, they would probably want to use air force to push back, again emphasizing the importance of air-to-air missiles and of pushing the altitudes planes could fly to.

I imagine that any floating attack center would want to be aquatic, to allow it to 'land' gracefully in water, and since I am imagining that moving over water is more cost effective than through the air. The idea of floating air craft carriers probably isn't far off, but wouldn't be the first thing invested in.


Kamikaze attack craft

Put one anti-grav machine on a massive concrete block, float it over the enemy fortifications, turn of the anti-grav, and you’ve got one enemy pancake under a bunch of concrete.


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