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The world I've been working on has a higher gravity (1.4g) and a denser, more oxygen-rich atmosphere (33% O2, 4 bar). While this has a plethora of effects, this question primarily discusses the impacts this has on aerial combat when technology is at a first world war level.

The heavier atmosphere means that a blimp, balloon, or zeppelin of the same volume will have 4 times the lifting force. This enables heavy bombers, aerial cruisers, and flying aircraft-carriers.

The denser atmosphere also induces four times the lift and drag at any particular airspeed. As drag is proportional to the square of airspeed, this presumably means a similar vehicle could travel at half the speed, though this may be compensated for with the improved power and cooling the atmosphere will give the engines. The lower speed combined with higher drag and lift should reduce the wing-load even further, though I do not know to what extent.

I have had difficulty calculating the exact effects the denser atmosphere and drag would have on bullet range, aircraft maneuverability, fuel-consumption, and wing-design. I would appreciate any help that could be provided in these areas, as well as any other thoughts or considerations that might be relevant.

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    $\begingroup$ With that much oxygen, you cannot have humans, and creature life will be more difficult.. Oxygen becomes toxic to humans at .5 bars of pressure. A 4 bar atmosphere with 33% oxygen has 1.32 bars of oxygen. That's pretty toxic and corrosive. $\endgroup$
    – Questor
    Mar 16, 2023 at 21:09
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    $\begingroup$ I do wonder if your intent is to make a fiery hellscape... That much oxygen is going to make everything burn.. I think that iron, aluminum and a lot of other "non-flammable" materials are flammable with that much oxygen present. Iron burns easily with 1 bar of oxygen (100% oxygen at sea level)... I don't know the atmosphere being only 33% might make it less flammable, but something you might want to consider. $\endgroup$
    – Questor
    Mar 16, 2023 at 21:22
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    $\begingroup$ I have done much consideration on the oxygen levels, and am likely to lower the total oxygen pressure to lower than 1 bar precisely for flammability reasons, as has been mentioned. The goal /is/ to have rapidly growing forests, fields, and swamps that regularly do burst into a fiery hellscape, though the levels may be adjusted to keep this at a balance. As for the humans, they would be humans that had evolved in this atmosphere and would have respiratory systems suited to avoid both oxygen toxicity and nitrogen narcosis. It is likely such a "human" would suffocate on Earth. $\endgroup$ Mar 16, 2023 at 22:17
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    $\begingroup$ This is not limited to aerial combat as such but yeah, a thick, high-oxygen atmosphere would have quite the effect on high-speed projectiles like bullets and artillery rounds, and not necessarily a desired one. $\endgroup$
    – biziclop
    Mar 16, 2023 at 22:30

2 Answers 2

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The speeds would be lower, altitudes higher, and there would be more planes without swept wings.

Think of lift and drag this way. Doubling airspeed causes 4x drag and lift. So, with 4x density you get the same forces (more or less) with half the speed. Half the speed means half the needed power. It would be much easier to get off the ground, which may have been accomplished even before combustion engines, using human power, and that's to say nothing of lighter-than-air aircraft. This civilisation would be very avian compared to ours.

Of course, speed is important in air combat, and at sea level, planes would struggle to approach the speed of sound. The speed of sound mostly depends on temperature and composition, not density or pressure, so it would be similar to ours. Therefore hitting the sound barrier takes a lot more power, even if not 4x the power, because planes could have smaller wings and inlets.

However, like in our world, airplanes escape high density and high drag by simply flying higher. Travel and combat would sometimes happen at very high altitudes, possibly at supersonic speeds. If they instead choose to optimise for low drag at subsonic speeds, planes would have thin droplet-like shapes and smaller, non-swept wings.

Weapons would more often feature rockets instead of guns for the same reason that submarines use torpedos. They might use subsonic cannons in close range combat.

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My first thought (without doing any calculations) - is that powered flight in terms of the aerodynamic load on the airframe is going to be much more difficult.

I'm not sure if Canvas, Wood and wire bracing would hold up with all the extra load that the increased density would generate.

This could potentially mean that Bi-Planes and Tri-Planes of WW1 never existed. Or at least, existed in a much studier format.

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