Generally speaking, on Earth, in order to fly, the pressure on the top of aircraft wings is lower than the local atmospheric pressure. So if we fly an airplane on Mars, will the pressure on the top of its wings also be lower than the local atmospheric pressure on Mars? I think it seems necessary, otherwise there won't be enough lift and the plane won't be able to fly. But I'm not sure if it's really like that.
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3 Answers
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I'm going to go out on a limb and saying "Yes".
There is only one plane on Mars, and it is rotary wing, so you can read about that (https://en.wikipedia.org/wiki/Ingenuity_(helicopter)).
What I remember from my time on Mars is that the atmospheric pressure is:
$$ p = 6{\,\rm mbar} $$
which is really low, but you also need to consider gravity:
$$ a \approx \frac 3 8 g $$
where $g$ ($a$) is for "geo" ("aero"--for Ares, not "air").
With the low temperature, that works out to an Earth density altitude of 87,000 ft (flight level 870?), well beyond the range of any Earth helicopter.
Note: this is way too expensive to test in the field. I wondered if they tested it in a the National Historic Registered Space Simulator (https://www.nasa.gov/setmo/facilities/25-foot-space-simulator/)..that might present some dynamic hazards, though.
Ginny was not part of the science package (afaik) and I think was just a technology demonstration (see: https://en.wikipedia.org/wiki/Technology_readiness_level), but may have been pitched as a "risk reduction" package. All that affects how much NASA is willing to spend on it, and that affects testing, and what we learned in the 90's "Better, Faster, Cheaper" era is that skipping tests leads to failure.
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It doesn't matter whether a wing is operating on Earth or Mars, or what the atmospheric pressure happens to be.
The lift on a wing depends on the average pressure on its upper surface being lower than the average pressure on its lower surface.
Notice that I mentioned average pressures. Locally, there can be pressures on either surface that are larger or smaller than atmospheric.
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I guess we're talking about NASA's Ingenuity helicopter, which has flown in the gossamer thin atmosphere and low gravity of Mars over the past years or so.
Mars' gravity of 3.73 m/sec^2 on the 1.8 kg mass of Ingenuity generated a downward force of 6.7 Newtons towards the surface.
On the ground, that force was opposed by an equal and opposite force from the surface.
When in flight, and no longer in contact with the surface, the downward force was opposed by the aerodynamic force generated by its spinning propeller blades.
Classical physics states that the only way that a gas can exert a force on a body is by pressure. So yes, to support Ingenuity there had to be a pressure difference between the top and the bottom of the wings (the blades of the helicopter).
It's not fluid dynamics or aerodynamics: it's fundamental physics, which is why it's an excellent example to raise in this physic sub-forum.
(Building the craft getting it to Mars was an engineering marvel.)
