Two weeks after departing Earth in a cataclysm of smoke and flame, the Perseverance rover continues to function well as it traverses 300 million miles (480 million km) to reach Mars and touch down in the geological richness of Jezero Crater on 18 February 2021. NASA recently reported that its Ingenuity helicopter—the first rotor-driven, heavier-than-air craft ever to be deployed on another world—has successfully wrapped up its first checkout and battery recharge in the space environment. The tiny helicopter, which weighs only 4 pounds (1.8 kg), will make short flights of up to 90 seconds at a time, ahead of Perseverance, to scout out localities of interest on the Martian surface.
Over an eight-hour period on 7 August, Ingenuity’s six lithium-ion batteries received their health check and mission controllers brought their charge level up to 35 percent, a “low-charge state” considered optimal during the long cruise through the dark emptiness of the inner Solar System to reach the Red Planet. “This was a big milestone, as it was our first opportunity to turn on Ingenuity and give its electronics a test-drive since we launched on 30 July,” said helicopter operations lead Tim Canham of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “Since everything went by the book, we’ll perform the same activity about every two weeks to maintain an acceptable state of charge.”
Stowed on Perseverance’s belly, Ingenuity receives its power from the rover itself, but after deployment on Mars it will utilize its own solar panel to generate electricity. “This charge activity shows we have survived launch and that so far we can handle the harsh environment of interplanetary space,” said Ingenuity Project Manager MiMi Aung of JPL. “We have a lot more firsts to go before we can attempt the first experimental flight test on another planet, but right now we are all feeling very good about the future.”
Ingenuity was relative latecomer to the Perseverance mission. Whereas the rover itself can trace its beginnings back to late 2012, the tissue-box-sized helicopter first gained traction as a possible low-flying scout in January 2015. “A rover’s vision is limited by the view of the on-board cameras and images from spacecraft orbiting Mars are the only other clues to where to drive it,” NASA explained. “To have a better sense of where to go and what’s worth studying on Mars, it could be useful to have a low-flying scout.” And although Ingenuity will only fly at altitudes of between 10 feet (3.3 meters) and 30 feet (10 meters) above the Martian surface, doing so on a planet whose atmosphere is barely one-hundredth as dense as our own makes this comparable to an altitude on Earth of 100,000 feet (30,500 meters). That is around seven times higher than a terrestrial helicopter has ever voyaged.
Formally approved to fly on the mission in May 2018, it was noted that the United States would be first to fly a heavier-than-air craft on another planet. With a fuselage about the size of a softball and a pair of counter-rotating propellers spinning at 3,000 rpm—ten times faster than a terrestrial helicopter—to afford it lift, Ingenuity will be deployed onto the surface in early May 2021, about 2.5 months after Perseverance lands at Jezero Crater. Perseverance will then withdraw to a safe distance, before issuing commands to the helicopter. A 30-day test campaign will see as many as five airborne “sorties” of incrementally greater distances up to 980 feet (300 meters).
To date, the closest Ingenuity has come to the environmental conditions it will experience in the rarefied atmosphere of Mars was early last year when it completed a series of tests in JPL’s 25-foot-wide (7.6-meter) Space Simulator. “Our test flights could have similar atmospheric density here on Earth, if you put your airfield 100,000 feet up,” Aung remarked. “So you can’t go somewhere and find that. You have to make it.”
In the Space Simulator, nitrogen, oxygen and other Earthly gases were extracted and replaced with levels of carbon dioxide not dissimilar to atmospheric conditions on Mars. A motorized lanyard attached to the top of Ingenuity simulated two-thirds of terrestrial gravity on the Red Planet. “We only required a 2-inch (5 cm) hover to obtain all the data-sets needed to confirm that our Mars helicopter flies autonomously as designed in a thin, Mars-like atmosphere,” said Ingenuity test conductor Teddy Tzanetos of JPL. “There was no need to go higher.”
When the helicopter next experiences conditions like this, it will be the real thing.