Ingenuity the Mars Helicopter Technology Demonstrator

One of the most exciting part of the Mars 2020 mission is not visible on the Perseverance rover interactive 3D web page. It is Ingenuity, officially named the Mars Helicopter Technology Demonstrator. (It has its own online interactive 3D model.) For people like myself who want to really dig into the technical details, NASA JPL published many papers on the project including this one for the 2018 AIAA Atmospheric Flight Mechanics Conference. (DOI: 10.2514/6.2018-0023)

Ingenuity is the latest in a long line of technology demonstrator projects from JPL, where ideas are tested at a small scale in a noncritical capacity. Once proven, later missions can make more extensive use of the technology. Perseverance rover itself is part of such a line, tracing back to Sojourner which was the technology demonstrator for the concept of a Mars rover. Reflected in its official name, the Microrover Flight Experiment.

Most of the popular press has covered Ingenuity’s rotors and how they had to be designed for Mars. It has the advantage that it only had to lift against Martian gravity, which is much weaker than Earth gravity. But that advantage is more than balanced out by the disadvantage of having to work in Martian atmosphere, which is much much thinner than Earth air. Designing and testing them on Earth was a pretty significant challenge.

Mechanically, the part I find the most interesting were motor and control system for the coaxial helicopter. It has been simplified relative to coaxial helicopters flying on Earth, but still far more complex than the category of multirotor aircraft commonly called drones. Most multirotor aircraft have no mechanical control linkages at all, their propellers rigidly attached to a motor and control is strictly electronic via motor power. The paper describes the challenges of implementing a coaxial helicopter control system for Mars, but it didn’t explain why the design was chosen in the first place. I’m sure someone worked through the tradeoffs. Since mechanical simplicity (and hence reliability) is highly valued in planetary missions, I am very curious what factors outweighed it. Perhaps that information was published in another paper?

Electronically, the most exciting thing is Ingenuity’s brain, which is from the Snapdragon line of processors better known as the brains for cell phones and tablets here on Earth. If it works on Mars, it would offer a huge increase in computing power for planetary missions. Perseverance itself runs on a RAD750 computer, which has proven its reliability through many successful spacecraft but is roughly equivalent to a 20-year old PowerPC desktop. Having more powerful CPUs for future missions will allow our robotic explorers to be more autonomous instead of being dependent on brains back here on Earth to tell them what to do.

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