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I have a setting that is pretty similar to Earth. The tech is at least around WW2 with some steampunk fantasy sprinkled here and there. A global war is about to break out. My civilizations need an agile aircraft that covers the 'fighter' niche.

Unfortunately, they have no access to petroleum on this planet. However, they have access to 2 unique technologies: Anti-gravity tech, and Sun-stones that can act as a battery for high-energy charge storage and powering the Anti-G Tech. They figured they could fuse these 2 technologies to create their aircraft. The Anti-gravity tech provides lift and traditional propellers provide force to move and push the craft; both are powered by electricity from the sun-stone.

Anti-Gravity Context The material that enables the Anti-gravity to move is Gravitite (not a unique name I know). The engineers have figured out ways to fully utilize it. One of the devices is an Altitude Pinner (AP). Once built into the frame of the aircraft, this can provide a few unique manoeuvres:

  • Vertical Take Off and Landing By adding a charge into the pinner, they can maintain an altitude relative to the dominant gravity well (in this case, the planet's gravity). Increasing or decreasing the charge will change the altitude. Discharging the power to a separate battery can turn off the pin and altitude lock. This can allow vertical take-off and landing without the use of the propeller. The downside is that it only acts against gravity, which is why you still need propellers to move horizontally.

  • Jump Pinning Once a Pin is activated, if the pinned object is forced to a different altitude, a force attempts to correct the altitude in proportion to the distance from its pinned altitude it has been moved. This can be useful for "slingshot" up or down manoeuvres. Having 2 Pins that can work with different altitudes can allow more advanced manoeuvres.

The Question In real life, we actually did have rear propeller aircraft back in WW1. But due to the extra weight required for the tail, and the invention of the synchronization gear, the tractor plan became favoured instead. The rear propeller design was more of an aesthetic difference then a practical one. My question with all this context about how Anti-gravity tech works. Would a Single Propeller Back Configuration make more sense for this kind of plane then a tractor type?

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  • $\begingroup$ This is a little thing, but "jump pinning" sounds a lot like violation of conservation of energy to me. It may not matter in your universe, and certainly not to stories in it, but you should be aware, at least. $\endgroup$
    – jdunlop
    Sep 12, 2022 at 2:20
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    $\begingroup$ There might not be a question here. An infinite energy battery combined with no need for lift means propellers as far out on the wings as possible that can be independently controlled might have greater value than worrying about push vs pull. In fact, the ability to put the motor anywhere would suggest that the front-vs-rear location of the prop (which will push just as much air either way) is irrelevant. What problem are you trying to solve? Having anti-grav and perfect batteries means a "real life" recommendation isn't the issue. The rear prop for your planes is pretty cool. Why not use it? $\endgroup$
    – JBH
    Sep 12, 2022 at 3:49
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    $\begingroup$ Also, please note that the only time I can think of when the Real World had the same plane as a fighter and a bomber was World War I's bi/tri-planes. Bombers needs space for bombs and power to move the weight, which makes them slow, cumbersome and easy to hit. Fighters are small, nimble, and fast. Anti-grav doesn't mean you're not moving the mass of the bombs. Just a thought. $\endgroup$
    – JBH
    Sep 12, 2022 at 3:50
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    $\begingroup$ You wouldn't actually need a propeller if you can counter gravity. A glider configuration would allow horizontal movement during both climb and descent by using good old fashioned control surfaces. 98+% of the aircraft on your world wouldn't even want one. But for fighter aircraft, you might. Only in a WW2 setting, a rocket would be the logical choice. No need for it in regular flight, massive sudden bursts of horizontal speed for maneuvering. Heavy fighters can lose altitude more easily, allowing frightening dive attacks. The physics are very different for your planes. $\endgroup$
    – DWKraus
    Sep 12, 2022 at 15:47
  • $\begingroup$ Plenty of answers, so I'll just drop this: Given the context. Id go for a pusher, flying wing. many of the issues that plague real world types are are likely mitigated with gravitite. $\endgroup$
    – Gillgamesh
    Sep 12, 2022 at 18:13

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Probably

There have been a few questions on Aviation SE such as this and this regarding whether pusher configurations are preferable or feasible. Obviously these are looking at the real world without antigrav, so the information there, including the link to this article comparing the advantages and disadvantages, need to be examined in light of the alternative physics.

One of the major concerns with a pusher propeller layout is that there are strict limits on how steeply nose-up the aircraft can be oriented on takeoff and landing, since nose-up = tail down = propeller gouging holes in the runway. If the aircraft in your world all maintain a level attitude and rely on pure antigravity for takeoff and landing then this is not a concern.

Another major advantage of tractor propeller layouts is that there is enhanced lift from the propeller's wash over the wing and control surfaces. However, antigrav aircraft aren't relying on wings for lift (though they will need control surfaces for steering) so again this is not a concern for an antigrav aircraft. In fact, not having the propeller forward make the control surface response more predictable rather than varying significantly depending on current engine output.

This leaves all the upsides of a pusher design still valid - improved forward visibility, reduced (eliminated) danger of propeller fragments striking the fuselage in the event of structural failure, improved safety on the ground with respect to boarding and disembarking in the vicinity of the propeller (which for a warplane includes loading munitions).

The only significant disadvantage is that any parts of the fuselage that are blown off in combat may fly back and strike the propeller of a pusher aircraft, which is physically impossible for a tractor configuration aircraft. This risk also applies to any pilots trying to bail out of an aircraft through the top. (To bail out safely, crew need to either go through the bomb bay or have an ejector seat that will boost them well clear of the aircraft.) It should still be perfectly safe to drop bombs, even with high-drag attachments, without any risk of them striking the propeller if the bottom of the bomb bay is lower than the lowest point of the propellers arc - which it probably needs to be in order to land.

Finally, as noted by JBH in comments, while the same aircraft design may be used as both a fighter and a tactical bomber with a minimal payload, strategic bombers are of necessity much bigger aircraft. It does not matter how they are powered, the different mission requires very different payload, range, crew and agility tradeoffs.

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Less Steampunk. More Buck Rodgers:

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Slight frame shift. I propose a different kind of rear-thrust propulsion.

You might be want to skip propellers entirely. There is really no need. Traditional aircraft use mostly horizontal thrust to create vertical changes in elevation by using control surfaces (wings) to climb in altitude. A fighter usually needed bigger engines during this period to attain an advantage in altitude. You could always go fast if you simply let your plane plummet.

With this tech, you have the opposite problem. You can easily attain altitude, but horizontal movement is a challenge. But the same control surfaces allow you to translate vertical motion into a horizontal change. the vast majority of aircraft on your world would have no need for anything else. They can go faster horizontally by increasing and decreasing altitude repeatedly. Horizontal speed can be shed in maneuvers. To save power, many aircraft would be designed like gliders to allow them to drift downward as slowly as possible while maintaining horizontal movement.

But for a fighter aircraft, sudden bursts of speed will let them maneuver in exotic and startling ways. Only for this as well, there is a simple solution in common use at the time of WW2 that would make a lot more sense.

Rockets.

enter image description hereenter image description here

Your WW2 will look like battles out of a Buck Rodgers comic. Rockets provide a GREAT deal of thrust in an extremely short period, and the basics of their engineering were worked out in ancient China. Many nations were building rocket-propelled fighter craft in WW2, but the limited range of a rocket meant you either ran out of fuel quickly or needed two propulsion systems (like propellers and rockets) to allow sudden bursts of speed in combat. Only weight and vertical climb are not your enemies the way they are in real life.

You won't even need complicated rockets with petroleum-based liquid rocket fuel. A solid-fuel rocket can be carried along on your gliding plane easily, burned quickly, then dropped to reduce drag and mass in a dog fight.

So I suspect your world would have big, heavy aircraft covered in rockets and guns, snaking their way through the sky up and down, then setting the heavens alight with rockets and guns blazing. With streaker rounds of the times, it will literally look like a bunch of star fighters blazing away at each other. It also means the transition to space battles will be a quick and easy one.

enter image description here

enter image description here

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The real question is how fast the vehicle is going, and how quickly the pilots can react to deviations. You need to make a configuration that self-stabilizes, or it will become unmanageable.

Hold a pencil vertically, like a rocket. Hold it from its front end, now hold it from its back end. You can feel the difference in stability there. The same can be said of front wheel vs rear wheel steering on a car.

Modern jets use the shape of the vehicle to improve stability, make it naturally tend towards flying straight. That is actually the failing of the 737 Max, that its configuration naturally caused the plane to dip forwards, and had to be perpetually compensated against. The perpetual compensation mechanism failed, causing crashes.

So you have lighter than air vehicles with significant mass. You have a minimum speed at which air stabilization works. Submarines and boats can get away with it because the water that they push out of the way weighs as much as they do. The aircraft speed has to pass through enough air-to-mass ratio to deflect it back into a stable configuration for this to work.

Blimps make this work because they move slowly enough, that they can control the motion by deflecting the direction of the air coming out of its propellers to change the direction of the aircraft.

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