Ingenuity helicopter on Mars - anomaly recovered

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Gfamily
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Ingenuity helicopter on Mars - anomaly recovered

Post by Gfamily » Sat May 29, 2021 7:20 pm

An interesting article on the recent sixth flight of the Ingenuity helicopter on Mars.
It suffered a dropped frame from the navigation camera which led to its AI flight control system having less control than it ought,
Fortunately, its general system resilience allowed it to keep within its overall flight envelope and it landed smoothly only a few metres from where it was planned.

https://mars.nasa.gov/technology/helico ... xth-flight

Worth sharing, I thought,
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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by bmforre » Sun May 30, 2021 10:16 am

Impressive.

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Martin Y
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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by Martin Y » Sun May 30, 2021 1:05 pm

I'm still astonished that a drone can fly at all in air that's only, what, about 1% the density of Earth's? Even though the gravity is less it's astonishing that the rotors can move a sufficient mass of air to make it lift.

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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by dyqik » Sun May 30, 2021 3:10 pm

Martin Y wrote:
Sun May 30, 2021 1:05 pm
I'm still astonished that a drone can fly at all in air that's only, what, about 1% the density of Earth's? Even though the gravity is less it's astonishing that the rotors can move a sufficient mass of air to make it lift.
I think it's one of those things that somewhat divides out. The air resistance the props encounter is pretty much proportional to the mass of air they shift. As long as you're in a regime where the flow is pretty much the same kind as on Earth, the props should work about the same, just at higher speeds.

But this is me handwaving hard enough to take off on Titan.

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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by IvanV » Tue Jun 01, 2021 10:04 am

Martin Y wrote:
Sun May 30, 2021 1:05 pm
I'm still astonished that a drone can fly at all in air that's only, what, about 1% the density of Earth's? Even though the gravity is less it's astonishing that the rotors can move a sufficient mass of air to make it lift.
I used to be rather surprised that the thin atmosphere of Mars can lift great dust storms, and display phenomena such as dust devils.

The force resulting from motion relative to a fluid is proportional to the density of the fluid. So air resistance at a given speed is only 1% what it is on earth. On the other hand, it is proportional to velocity squared. So at a very simple level, you might need to turn your rotors 10 times faster to get the same rotor/air force. Though I know nothing about aerodynamics, and maybe those effects would mean you can get away with less. Probably you can also compensate in part by having longer rotor blades.

It seems that typical wind speeds on Mars are generally somewhat higher than typical on earth (on land), but similar to windier places like Britain. Maximum wind speeds are rather lower than terrestrial hurricanes and tornadoes. In Martian dust storms, wind speeds tend to max out at about 100km/h.

Something I eventually appreciated is that dust is generally much finer on Mars than on earth. On earth, the finest dust is quickly lifted into the air and blown away to locations it can be captured, like being washed out into the sea and watercourses, or into soil where it gets compactified. What is left behind is rather coarse dust that is harder to lift in a dust storm than the fine stuff they have on Mars. Hence the sand dunes of our deserts, where what is left behind is the coarse sand particles.

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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by basementer » Tue Jun 01, 2021 10:20 am

That last point is mentioned in Kim Stanley Robinson's novels about terraforming Mars. One of his characters says that it's inaccurate to call the fine particulates "dust": they are much smaller than that, it would be like calling sand "gravel".
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Re: Ingenuity helicopter on Mars - anomaly recovered

Post by monkey » Tue Jun 01, 2021 2:16 pm

Martin Y wrote:
Sun May 30, 2021 1:05 pm
I'm still astonished that a drone can fly at all in air that's only, what, about 1% the density of Earth's? Even though the gravity is less it's astonishing that the rotors can move a sufficient mass of air to make it lift.
It's not helicopters, but Randall Monroe did a What If about flying a cesna on different planets and moons - clicky. It might give you some idea about what's required.

Monroe links to a blog - clicky - where the author used a flight sim to fly a plane on Mars. To fly a plane you have to go ~3.8x faster: ~10x for the thinner air and ~0.38x for the gravity. I imagine the same is true for a helicopter rotor, because that's just a wing that spins round. Apparently, designing a plane to fly over Mars is doable, but inertia is a problem when it comes to landing and avoiding mountains. In that respect, a helicopter seems more sensible than a plane.

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