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Titan has 50% denser atmosphere than Earth and a fraction of the gravity. Could a helicopter-like probe, similar to the Dragonfly or Ingenuity, generate enough lift and velocity to escape Titan? Or maybe just enough to reach orbit just from its own propellers? How would one calculate size and power necessary for that?

My first instinct was no, not possible, because regardless of atmospheric density that ground level, eventually it gets so thin the higher you go that can't keep propelling up. But, if it's so dense with such low gravity at ground level. Can't you just leverage (abuse) that first phase of the flight to generate so much velocity that by the time you get to thin atmosphere, you already have so much momentum that you can just turn off the blades and still get to orbit?

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    $\begingroup$ Propeller-driven craft can't go supersonic because propellers don't work effectively at Mach 1+. $\endgroup$ – Giovanni Apr 20 at 13:42
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It's a good question, but no it's not possible. The denser atmosphere works for you and against you, for you in that you can achieve more lift with less blade or a slower blade rotation, against you because it also increases drag which will slow the craft and it's blades.

But, regardless of density this won't work because of the basic mechanics of helicopters. It is at low altitude with high atmosphere density where the blades will be most efficient, at higher altitudes where the air gets thin you get much less lift, you would never be able to get up to escape velocity.

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Good luck getting a helicopter hypersonic. You need more than 2,600 m/s to escape Titan. The speed of sound on Titan is 194 m/s.

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    $\begingroup$ OTOH a jet airplane, using oxidizer instead of fuel... $\endgroup$ – SF. Apr 20 at 12:20
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    $\begingroup$ @SF. A 2,600 m/s plane is going to be an absolute nightmare to design but I don't think it's impossible. (At those speeds you can only test on a 1:1 scale and with the entire airframe.) $\endgroup$ – Loren Pechtel Apr 21 at 20:05
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There is a maximum height for the helicopter. If the lift force of the rotor is equal to the weight of the helicopter it could not get higher. If you go up with maximum speed you only get a little jump above the maximum height but very soon the helicopter will be down at maximum height again.

The escape velocity of Titan is 2.639 km/s. A helicopter with about 360 km/h or 100 m/s is 26 times too slow.

You need a tiny body with a very low escape velocity, but those bodies don't have an atmosphere.

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  • $\begingroup$ The escape velocity is 2.639 km/s but how high could a helicopter go on Titan? And doesn't the escape velocity become lower the higher you get? $\endgroup$ – ypercubeᵀᴹ Apr 23 at 21:31

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