Mars helicopter ingenuity flies, flies and flies

On the other hand, summer brought other problems: the already thin Martian atmosphere had become thinner due to rising temperatures. Air pressure dropped from about 1.2 to 1.5 percent of the ground value to just one percent. “The difference may seem small, but it has a huge impact on the creativity ability to fly.” Chief pilot writes fist. With a density of 1.2 percent, for which the helicopter was originally designed, Ingenuity has thrust reserves of at least 30 percent. It is a task to take off and in case of unplanned obstacles it has to be crossed. But in the summer of Mars, these reserves fell to eight percent. Not enough to fly safely.

So the team increased the speed of the rotors from the original 2,400 rpm to 2,700 rpm. More could not have been achieved, otherwise the rotor tips would have reached a velocity close to the speed of sound, which would generate additional drag.

However, higher speeds mean heavier loads are placed on the engines and other moving components. Onboard temperatures soared, and the team had to reduce the maximum flight time from 150 seconds to 130 seconds. Just leaving early in the morning when it’s colder on Mars wasn’t an option. Creativity needs the first rays of the sun to warm itself from the cold of the night and charge its batteries with the help of solar cells. This made every flight risky, and there was a trade-off between speeds, temperatures, take-off time and flight duration.

Another problem with the JPL team: Creativity is not made for height. Small helicopter navigation is responsible for this. Since there is no GPS on Mars, Ingenuity relies on built-in sensors. They measure acceleration and rotation and use that to calculate the helicopter’s position. However, this is all inaccurate. Therefore, there is also a navigation camera facing downwards on board. It takes a photo 30 times a second, compares individual photos and determines the old and the new position.

However, in its calculations, the program assumes that the Earth is flat – after all, creativity should not fly anywhere else. When the helicopter is in a mountainous area, the hilltops seem to move faster than the rest of the landscape because they are closer to the camera. This confuses the algorithms. Navigation becomes imprecise, direction of flight varies, and accurate landings are no longer possible. The longer the flight, the greater the potential landing area.

This becomes a challenge, especially in the uneven deltas of the Jezero crater. The problem is not easily resolved: flat navigation is hard-coded into the onboard Ingenuity computer. So the team surrounding lead pilot Grip simulates upcoming flights over hills, cliffs, and sand dunes on ground computers. It looks like what a cluttered computer might make on the board, and reschedule itineraries accordingly.