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How NASA Designed a Helicopter That Could Fly Autonomously on Mars

spectrum.ieee.org

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Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#61

Post by interestica »

ryan_j_naughton wrote: post #52

Can someone who understands aeronautical engineering explain why they went with a helicopter over a winged aircraft? My guess is that takeoff would be too difficult for a traditional winged aircraft and VTOL was way too complicated. But given the thin nature of the atmosphere, a helicopter seems even more difficult to get lift than a winged aircraft. Can someone explain or link to the science between lift and air den…

> But given the thin nature of the atmosphere, a helicopter seems even more difficult to get lift than a winged aircraft.

Easier to speed up a helicopter's wings (rotors) than speeding up an aircraft which would need more and more runway.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#62

Post by aero-glide2 »

BorisTheBrave wrote: post #36

Can someone explain the phyics of flying a helicopter in such low density atmosphere? It must be less efficient than on earth, but evidently efficiency isn't proportional to density or else it could not fly at all.

The blades spin much faster to generate the required lift (lift proportional to density). Mars having lower gravity also helps.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#63

Post by aero-glide2 »

inetstarrrrrr wrote: post #12
shatnersbassoon wrote: post #6

Earlier quoted context omitted.

I would have thought atmospheric data that you can't get elsewhere - you'd be able to learn things about pressure and wind at altitudes that rovers can't get to.

I don't think it will fly that high to make a measurably difference to ground level. It only flies for 90 seconds. How high can you get in that time?

This is a tech demo. This will help design future Martian drones.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#64

Post by mzs »

nuccy wrote: post #46
retSava wrote: post #8

So many interesting details in this article. Snapdragon 801-based hw running Linux, sensor fusion from three sensors whereof some bought COTS from sparkfun (who make breakout boards for sensors, basically the sensor datasheet recommended design). 3 flights planned, but potentially more which will be planned after the three first. 30 day lifetime window, due to dependecy on the rover, which needs to conserve resources…

Actually the computing power of Ingenuity surpasses one of the Perseverance rover (and probably by a lot). The rover has a radiation hardened RAD 750 CPU (based on PowerPC 750 architecture, which was introduced in 1997 to compete with Intel's Pentium II [1,2]) with 250-150nm technology process operating at 200Mhz[3]. Ingenuity's Snapdragon 801 can reach up to 2.5 GHz and is based on more energy-efficient 28nm modern…

There are also two redundant TI MCUs on the copter

>TMS570LC43x high-reliability automotive processor operating at 300 MHz, with 512 K RAM, 4 MB flash memory, UART, SPI, GPIO

https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#65

Post by drone_aero »

BorisTheBrave wrote: post #36

Can someone explain the phyics of flying a helicopter in such low density atmosphere? It must be less efficient than on earth, but evidently efficiency isn't proportional to density or else it could not fly at all.

Using actuator disc theory, accounting for 38% gravity and 1.2% air density, Ingenuity would need about 2.1x more power to hover on Mars.

But it's not that simple. The reynolds number which Ingenuity's blades are operating on Mars is extremely low, 10,000 to 20,000. This makes the airfoils less efficient compared to what you might design on Earth.

Compare to a Trex 450 (30% heavier weight equivalent) helicopter on Earth, it's got 10+ minutes of endurance and has a smaller diameter rotor, whereas Ingenuity has a 90 second stated endurance, although that is probably limited by navigation too.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#66

Post by rtkwe »

amelius wrote: post #42
gambiting wrote: post #39

Earlier quoted context omitted.

I do remember reading about this - a balloon would work, but it would be absolutely enormous, far larger than anything we can bring into Mars currently. Maybe some day.

Another thing I'm wondering: the drones can probably carry only a small (light) camera, whereas a satellite can carry much more and thus also a much better camera. Wouldn't a satellite+camera be a better option?

For a given aperture there's a limit to the angular resolution you can get which means you can only see objects above a certain size from orbit. The highest resolution we had in 2013 had a resolution of ~.3m/pixel. That's too large for anything beyond rough mapping for things like landing or a vague plan for driving.

TL;DR a decent camera at 100km no matter how good the satellite camera is.

https://space.stackexchange.com/questions/1140/whats-the-hig...

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#67

Post by holoduke »

inetstarrrrrr wrote: post #3

What's the point of flying a helicopter on Mars? What scientifically relevant data do you get? Its fun and cool but why?

Because exploring is our nature. And because it will be the first test or flying something in an alien atmosphere. Tons of data alone from the first 5 seconds is very interesting. It's the first step to commercial airliners on Mars :)

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#68

Post by teraflop »

nynx wrote: post #59
jhurliman wrote: post #54

Earlier quoted context omitted.

I had the opportunity to go down to JPL and speak with team members about this design decision. The space hardened processors are not fast enough to do real time sensor fusion and flight control, so they were forced to move to the faster snapdragon. This processor will have not flips on Mars, possibly up to every few minutes. Their solution is to hold two copies of memory and double check operations as much as possib…

I'm a little surprised they didn't go for three separate computers and compare them for every operation, or something like that, but I'm sure they have their reasons.

I've never seen an off-the-shelf processor that has hardware support for doing that kind of cross-checking on every instruction. And doing it in software would probably add so much overhead that the error-checking would be much more likely to fail than the application code.

If you're willing to relax your real-time constraints a bit, and risk a brief period of incorrect behavior before the error is caught, the problem becomes vastly easier and cheaper to solve.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#69

Post by chasd00 »

alfla wrote: post #55
jhurliman wrote: post #54

Earlier quoted context omitted.

I had the opportunity to go down to JPL and speak with team members about this design decision. The space hardened processors are not fast enough to do real time sensor fusion and flight control, so they were forced to move to the faster snapdragon. This processor will have not flips on Mars, possibly up to every few minutes. Their solution is to hold two copies of memory and double check operations as much as possib…

Do you have a source for those fast reboots? It's running Linux after all

is Ingenuity running Linux? All of the flight controller software i've seen for autonomous drones don't use an operating system.

Re: How NASA Designed a Helicopter That Could Fly Autonomously on Mars

#70

Post by zyxzevn »

drone_aero wrote: post #65
BorisTheBrave wrote: post #36

Can someone explain the phyics of flying a helicopter in such low density atmosphere? It must be less efficient than on earth, but evidently efficiency isn't proportional to density or else it could not fly at all.

Using actuator disc theory, accounting for 38% gravity and 1.2% air density, Ingenuity would need about 2.1x more power to hover on Mars. But it's not that simple. The reynolds number which Ingenuity's blades are operating on Mars is extremely low, 10,000 to 20,000. This makes the airfoils less efficient compared to what you might design on Earth. Compare to a Trex 450 (30% heavier weight equivalent) helicopter on Ea…

Thanks for your answer. It is hard to find good information about the aerodynamics.
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