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MARS HELICOPTER INGENUITY
In July 2020, NASA launched the Perseverance rover to Mars. Traveling along with Perseverance is Ingenuity, the first helicopter designed to fly on Mars. A small autonomous aircraft, Ingenuity is designed to perform the first tests of powered flight on another world. In the months after Perseverance lands, the helicopter will be lowered from the rover's belly onto the surface of Mars to test powered flight in the planet's thin atmosphere.
Lift is a force that is generated when the slightly angled moving blades of the helicopter encounter air particles. This increases the air pressure on the bottom of the blades. And the increased air pressure forces the blades and the entire helicopter up into the air. When there are fewer air particles in the atmosphere, less lift is generated. Mars' atmosphere has only 1% of the particles of Earth's atmosphere. This means that blades that generate enough lift on Earth won't work on Mars.
To generate enough lift for the Mars helicopter, engineers gave it two sets of enormous blades that are 4 feet (1.2 meters) across and rotate about 10 times as fast as those of helicopters on Earth.
Ingenuity will perform a series of test flights over a 30-Martian-day window that will begin sometime in the spring of 2021. (A Martian day, or sol, is 24 hours and 37 minutes.) For its first flight, Ingenuity will hover a few feet above the ground for about 20 to 30 seconds and land. That alone will be a major achievement: the very first powered flight in the extremely thin atmosphere of Mars! After that, the team will attempt additional experimental flights over a farther distance and at a greater altitude. Ingenuity’s performance during these experimental flights will help inform decisions about the future use of small helicopters for Mars exploration. Future Mars helicopters could serve as robotic scouts, surveying terrain from above, or they could function as stand-alone science craft carrying instrument payloads.
Designing a helicopter to fly on Mars was no small task. The Mars atmosphere is only 1% the density of Earth’s atmosphere, so generating enough lift to overcome the gravity of Mars is a challenge. The helicopter had to be lightweight with extremely fast rotors to be able to generate enough lift. Though a full outdoor test couldn't be done on Earth, engineers were able to simulate conditions on Mars inside a test chamber at NASA's Jet Propulsion Laboratory in Southern California. To do this, they offset Earth's gravity by attaching tethers to the helicopter that support about 62% of its weight. Then, they performed flight tests inside a vacuum chamber that pumped out approximately 99% of the air, leaving a very thin atmosphere. Months of design, testing, redesign, and retesting went into the development of the Ingenuity Mars helicopter. Though engineers came up with their best design and it worked well inside the test chamber, the real test is yet to come once the Perseverance rover lands on the surface of Mars, delivering Ingenuity to its new test environment.