How NASA Designed a Helicopter That Could Fly Autonomously on Mars

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.<p>I would looooove to know more more more about this. What did dev of this look like (eg simulators)? What&#x27;s the flight envelope? What are the most important risks and how are they mitigated? What internal discussions took place (do this, prio that, don&#x27;t do X etc).<p>Just so much interesting stuff! Can&#x27;t wait :)<p>edit: from wikipedia: &quot;Each flight is planned to be at altitudes ranging from 3–5 metres (10–16 ft) above the ground.[1] In up to 90 seconds per flight, it could travel as far as 50 metres (160 ft) downrange and then back to the starting area&quot;.<p>&quot;The helicopter uses counter-rotating coaxial rotors about 1.2 metres (4 ft) in diameter&quot;.<p>Etc. Recommend the wiki page on it: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Mars_Helicopter_Ingenuity" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Mars_Helicopter_Ingenuity</a>

I had the opportunity to speak with one of Ingenuity&#x27;s engineers in the NASA pavilion at the EAA Fly In in Oshkosh, WI in 2017 (or perhaps 2016). This was before it had been accepted for the Rover2020 mission but just after they had proven the concept flight capable. I asked him about flight conditions on Mars and what they had to do to get their design airborne in such a thin atmosphere. He made a few points.<p>1. Given the thinness of the atmosphere, the counter rotating blades are balanced among thickness, length, and rotation speed. They&#x27;re essentially as big as they can spin with the power they have at a speed where the tips are just under the Martian speed of sound.<p>2. I asked if wind was an issue. He said that it wasn&#x27;t an issue for the stability of the craft (Martian wind moving much of anything is a movie trope) but the turbulence it caused could be a major issue for the blades, as they&#x27;re essentially small wings, like a helicopter. The turbulence of a cross breeze could disrupt the flow of air over the blades and cause them to lose lift.<p>3. The design of the craft was essentially locked once they confirmed it could fly. They would keep most of their original hardware and software, rather than rebuild anything, which I found surprising. Given this was before they were accepted on the mission I&#x27;m not sure if anything changed. It does appear to be pretty equivalent to what we saw there.

I find, besides all the extremely exciting, technical challenges, the following sentence incredibly fascinating:<p>&gt; &quot;This [is] the first time we’ll be flying Linux on Mars.&quot;<p>But regardless of that, I find it so incredibly cool and inspiring that during my lifetime, a human flying vehicle will fly on Mars. I was a space nut in my childhood and youth and love to see this.

&gt; It’s kind of an open-source victory, because we’re flying an open-source operating system ...<p>That is in reference to Linux. I think it can be a proud moment for Linus Torvalds and the team.

One thing that I have been wondering, if the atmosphere is so thin, then how does the RTG cool? I seem to have nerd-sniped myself.<p>It needs a temperature differential to generate electric current and it looks to have fins for convective cooling but the atmospheric pressure is a few % of that of sea level Earth.

Here&#x27;s one of the referenced software frameworks (if I understand correctly) used for the ingenuity control systems: <a href="https:&#x2F;&#x2F;github.com&#x2F;nasa&#x2F;fprime" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;nasa&#x2F;fprime</a>

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&#x27;t proportional to density or else it could not fly at all.

If you just want images from a different angle, why not tether it to the rover?<p>Also can&#x27;t you use a kind of balloon instead to save power?

Could they use it to try blow dust off the Opportunity rover&#x27;s solar panels to see if it&#x27;ll boot again?

techpod did an episode recently with the engineering camera payload uplink lead from nasa jpl doug ellison. it was very cool.<p>from the episode summary:<p>&gt; &quot;Friend of the podcast Doug Ellison from NASA&#x27;s Jet Propulsion Lab stops by to give us the lowdown on the newest Mars rover Perseverance, which will be landing on the red planet in just a few weeks, plus all kinds of fun info about Lagrange transceivers, making oxygen out of thin air, flying helicopters on other planets, and recording home movies at mach 25.&quot;<p><a href="https:&#x2F;&#x2F;techpod.content.town&#x2F;episodes&#x2F;71-curiosity-and-perseverance" rel="nofollow">https:&#x2F;&#x2F;techpod.content.town&#x2F;episodes&#x2F;71-curiosity-and-perse...</a>

I implemented a visual-inertial navigation based on the algorithm called MSCKF. It would be really interesting to know what kind of algorithm they are using. They mentioned state propagation in the article. This might indicate they are using an algorithm based on extended kalman filter.<p>It takes quite some care to make those algorithms robust. Even when you run in an environment covered with diverse visual features. The state divergence is a real thing which essentially means the copter is falling from the sky (Do they call it like that on Mars?).

Can someone who understands aeronautical engineering explain why they went with a helicopter over a winged aircraft?<p>My guess is that takeoff would be too difficult for a traditional winged aircraft and VTOL was way too complicated.<p>But given the thin nature of the atmosphere, a helicopter seems even more difficult to get lift than a winged aircraft.<p>Can someone explain or link to the science between lift and air density and it&#x27;s relation to helicopters and winged aircraft? Thanks!

Unfortunately the article does not talk about how this helicopter would fare in a sandstorm. Are the winds strong enough to tip it over?

&gt; With all this in mind, getting Ingenuity to Mars in one piece and having it take off and land even once is a definite victory for NASA<p>Sorry, slightly off-topic: Not a native English speaker. Isn&#x27;t this sloppy writing? Seems like declaring victory ahead of time?

I&#x27;m amazed they were able to pack enough energy in the thing to get the props to go fast enough to work in Mars&#x27;s barely there atmosphere. Keeping it upright is standard equipment in even low-end quadcopter drones.

Seems shortsighted to end this mission after 30 days.<p>I imagine it&#x27;s purely for mission planning complexity reasons. But a more sensible approach seems to be to say &quot;after 30 days you have to limit comms to 100 bytes&#x2F;sec back to earth and stay 100 meters from the rover&quot;.<p>In the future I could imagine the more modern processor on the helicopter might become handy... Some neural network based navigation system might run on it but not the rover main cpu... Also the helicopter might be able to get very good aerial photos that could be turned into 3d models to figure out the best spots to do science. It should be able to see much better than orbital radars.

Obligatory Veritasium video link: <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=GhsZUZmJvaM" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=GhsZUZmJvaM</a>

I wish we could have more information on the terrain relative navigation implementation..

Imagine how far the technology could go had we sent 10 times the missions we do now.

What&#x27;s the point of flying a helicopter on Mars? What scientifically relevant data do you get? Its fun and cool but why?