The Ingenuity helicopter arrived on Mars Feb. 18, encapsulated in the bottom of the Perseverance rover. As this is a technology demonstration, this experiment was filled with great challenges and firsts, with a planned experiment session 31 days long. The rover will monitor flights, measure meteorological data, and provide long-range communications for the helicopter. It is the first aircraft of any kind to land on another planet.
The first design challenge is the thin Mars atmosphere, which is just 1% as thick as the air we breathe. Since the air was so thin, scientists designed Ingenuity to be as light as possible, so it has miniaturized computers, sensors, and motors. It is 19 inches high with a 4-foot (1.2 m) carbon-fiber rotor that will spin at an incredible 2,400 RPM to generate enough thrust to lift the four pounds into the thin Martian atmosphere. That design also meant a small 5.5 inch (14cm) cube chassis. Given the weight limits, batteries needed to be small, limiting flight time to 90 seconds.
One factor helping this challenge was the significantly lower gravity of Mars, which is just 38% of Earth’s gravity. It would be much more difficult to achieve flight in that thin are with Earth’s gravity. On Earth, the altitude record for helicopters is 40,814 ft (12,442 m), but the pressure on Mars is equivalent to 22 miles (35km) above Earth’s surface.
The next design challenge was to survive the severe temperatures from -115°F in the night to -10°F during the day, which it did thanks to the excellent lightweight insulation. To save weight and space, scientists designed thin sheets of insulation with air trapped between them, just as layers of feathers trap air around a duck or goose.
The final design challenge was that the flight needed to be autonomous because the communications delay between Mars and Earth is several minutes. Given the weight and power restrictions plus temperature extremes, scientists combined new controllers, sensors, and cameras with smartphone devices to create the helicopter’s control system.
The first step after arriving on mars was to drop the protective shield and land on Martian soil. The sequence looked something like this test of the rover-helicopter equipment before launch:
Ingenuity touched Martian soil on April 3rd, landing on its feet. Here is a shot of Ingenuity hanging under Perseverance rover, ready to drop:
On the ground, after initial diagnostics, it send back this first photo from beneath the rover, proving all was well:
From April 3rd to the 19th, the helicopter absorbed the Sun’s rays, charging the batteries and scientists tested the navigation camera, accelerometer, gyroscope, and laser altimeter. Then diagnostics included testing the rotor without lifting off and finally loading the first flight plan.
The flight plan is a set of steps or milestones that Ingenuity’s brains will move to meet. Imagine someone telling you to get up from the couch and get a glass of water. They don’t need to tell you which muscles to move or individual waypoints. The flight plan works the same way – It will tell Ingenuity to spin the rotors for a set time, fly this high in this direction, take a few photos, and land. The processor then uses the sensors and rotor spin to match that path as closely as possible. Since this was a technology demonstration, the flights would start simple and increase in complexity as Ingenuity passed each step.
Since the rover cannot move the helicopter upright after a crash or after topping over and there are so many unknowns about operating in thin atmosphere and light gravity, NASA is taking baby steps. Each flight will test one or two maneuvers, then land and recharge while scientists examine all the data.
Ingenuity’s first flight on April 19 was short and simple, but historic – It climbed to an altitude of 10 feet, hovered for 30 seconds, then descended safely to the surface for a total of 39 seconds of flight. This was the first flight on Mars and like the Wright brothers’ flight simply proved flight was possible and that all systems worked as expected:
NASA has named the location for the Ingenuity flights “Wright Brothers Field”. Here’s’ the first shot of the field from Ingenuity at 10 feet:
The second flight on April 22 was a slightly higher altitude of 16 feet (5m) with a slight tilt of 5° to move 7 feet (2m) sideways. Then the helicopter hovered, rotated to point the camera in different directions, then headed back to the center of Wright Field and landed again.
Ingenuity’s third flight was again more complicated, this time moving 164 feet (50m) sideways at 6.6 fps (2mps) at same altitude as the second flight, 16 feet (5m):
For more information, check out this video from one of my favorite YouTube channels, Veritasium:
The 16 minute video is packed with info and well worth the time.