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Comment by KuiN | Hacker News Reader

As other have said, it's a tech demo. Partly just to show we can do powered flight on other celestial bodies, part of it is to test how well the off-the-shelf parts in Ingenuity work in that environment. Rotorcraft require more computing power than is available from typical rad-hardened processors. Ingenuity is using a Snapdragon mobile phone chip, will be interesting to see how long it survives up there.

NASA have plans to use rotorcraft in many future missions, including the Dragonfly which will fly around Titan[0]. Launches in 2027.

[0] https://www.nasa.gov/press-release/nasas-dragonfly-will-fly-...

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>Rotorcraft require more computing power than is available from typical rad-hardened processors.

Ingenuity uses a three-level control system for avionics[0] - the Linux part that runs on the Snapdragon 801 is at the top tier and does more the mission computer functions like navigation, computer-vision, telemetry, command processing and interfacing to the radio.

The middle tier is a dual-path redundant microcontroller system based on the TMS570 architecture. This is an automotive-grade part qualified for safety-critical usage. This an ARM Cortex R5 design, so not exactly a speed demon.

The bottom tier is a radiation tolerant, mil-spec FPGA (Microsemi ProASIC 3L) that actually runs the control loops at up to 500Hz, handles communication with the IMU, motor control interfaces etc; this part is actually supposed to be functionally identical to the space-qualified version.

The "Linux running on a smartphone processor" aspect gets a lot of play but the stack as a whole uses a lot more traditional high-integrity design approaches. Most of the heavy-lifting of "fly the rotorcraft" is done away from the Snapdragon, and I'm not sure where the idea that "rotorcraft need a lot of CPU power" comes from.

[0] https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

>Rotorcraft require more computing power than is available from typical rad-hardened processors.

the CPU on a fairly advanced quad, hex or octocopter on earth can be a STM32F7 or STM32H7 family microcontroller, which is not very powerful in terms of raw computing power. That's more than fast enough (in an earth environment) to pull in sensor input at a high Hz refresh rate from dual IMUs, barometer, GPS, and control up to eight motor ESCs, along with running the UARTs for communication to a remote control link, and additional spi, i2c or UARTs to do things like run camera gimbals.

https://docs.px4.io/master/en/flight_controller/cubepilot_cu...

Yeah, I think the biggest factor preventing such a simple design from working well on Mars would be the (current) lack of anything equivalent to GPS.

In order to navigate safely, especially during takeoff and landing, you need a reasonable idea of your absolute velocity relative to the ground. You can't get that from an IMU (except over very short timescales) because of integration errors. A barometer would work for the vertical axis, but getting the horizontal component is a lot trickier. GPS solves this nicely, especially since velocity can be derived from relative measurements, which are much more accurate than absolute ones.

It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide.

>It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide.

I believe that for Ingenuity they are actually doing this in software; but at this point, you can just buy off-the-shelf an optical flow odometry ASIC with a built-in camera and lens system that draws <5mA, fits in a 4x5mm footprint and gives you delta-X and delta-Y.

e.g. https://www.pixart.com/products-detail/108/PAA3905E1-Q

Kinda mind-blowing.

Is that kind of like optical mouse sensor?

Yes it is! Obviously it's a slightly harder problem if you don't know the distance from the surface and you can't provide your own illumination.

That's one of those missions I'm actually really hoping I live to see: a whole sequence of launches putting a GPS constellation into orbit around Mars.

At the relatively low heights ingenuity is flying at, a single point LIDAR rangefinder aimed straight down would also be well suited to maintaining a certain altitude.

In addition to the (very valid!) tech demo aspects of this, there's also the huge public interest/public relations aspect. I've seen more articles and comments on Ingenuity than on any other part of this Mars mission. (Personally, I'm excited for the MOXIE instrument[1] - tech that's all but mandatory before human missions)

[1] https://mars.nasa.gov/news/8926/nasas-perseverance-mars-rove...

> Quadcopters require more computing power than is available from typical rad-hardened processors.

Ingenuity isn't a quadcopter though, it has two blades that counter-rotate around the same axis.

> two blades that counter-rotate around the same axis

Which would make it a coaxial helicopter.

https://en.wikipedia.org/wiki/Coaxial_rotors

It's pretty funny to me that the processor on Ingenuity handily outperforms the one on Perseverance by several orders of magnitude.

That's the point of the demo. If Ingenuity's processor survives, then NASA can consider these more advanced processors. If it doesn't, then that means continued use of lesser capable but rad hardened processors will still need to be used. OR, it could mean a re-evaluation of mission lengths. if more science can be done using a more capable processor that is known to have a limited lifespan, then that will have to be evaluated against the benefits of longer missions with less processing requirements

They still have a sample size of 1...

Surely a better test would be to get 1000 mobile phone processors and put them in a radiation chamber on earth and see how many fail? It would be far cheaper and be better science.

But then we'd have no helicopter on mars right now

I reckon it might actually be cheaper to put together a smallsat with 1000 processors on it and stick it in low earth orbit. Building a chamber and finding all the radiation sources you'd need to accomplish such a thing surely is no small task...

Maybe we don't know the composition of the radiation on Mars precisely enough?

i've never thought about, but i don't recall any of the other probes/rovers reporting back on things like UVA/UVB or anything else like that. However, with no atmosphere or the Martian equivalent to Van Allen belts, wouldn't it be safe to assume that whatever streams out of the sun is reaching the surface? it would be a matter of intensity on the surface vs what type would it not?

Flying drones can open yet more places for exploration in the future - even with the new active precision landing feature introduces with Perserverance the landing elipse still needs to be relatively flat ground with limited ammount of obstacles.

If we want to see and explore deep valleys or high mountains before some future the first setlers go there with gopros and do a Twich stream then flying drones are a good option.

>Launches in 2027.

Hopes/Scheduled to launch in 2027 seems more accurate. Even when the rocket is fueled and on the pad, it can still get scrubbed.

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