How to fly a helicopter on Mars

On Sunday, Ingenuity—the small helicopter delivered to the surface of Mars by the Perseverance rover—will, hopefully, take its first flight. The distance between Earth and Mars means that lagtime precludes real-time remote control. The helicopter flies autonomously, but the helicopter's digital twin had a lot of practice in simulations back on Earth. At IEEE Spectrum, Evan Ackerman interviews Ingenuity's chief pilot Håvard Grip:

Without being able to test on Mars, how much validation are you able to do of what you're seeing in simulation?

We can do a fair amount, but it requires a lot of planning. When we made our first real prototype (with a full-size rotor that looked like what we were thinking of putting on Mars) we first spent a lot of time designing it and using simulation tools to guide that design, and when we were sufficiently confident that we were close enough, and that we understood enough about it, then we actually built the thing and designed a whole suite of tests in a vacuum chamber where where we could replicate Mars atmospheric conditions. And those tests were before we tried to fly the helicopter—they were specifically targeted at what we call system identification, which has to do with figuring out what the true properties, the true dynamics of a system are, compared to what we assumed in our models. So then we got to see how well our models did, and in the places where they needed adjustment, we could go back and do that[…]

Because there are limits to the physical testing we can do on Earth, there are elements where we know there's more uncertainty. On those aspects where the uncertainty is high, we tried to build in enough margin that we can handle a range of things. And simulation gives you the ability to then maybe play with those parameters, and put them at their outer limits, and test them beyond where the real parameters are going to be to make sure that you have robustness even in those extreme cases.

And here is NASA's status update on the Ingenuity flight.