The Wright Brothers get credit for the first controlled, autonomous flight on Earth, more than 120 years ago.
But what about on other planets?
That achievement for Mars came courtesy of the Ingenuity helicopter in April 2021, when the tiny craft, which had tagged along on the 2020 mission to the Red Planet, spun its blades in the extremely thin atmosphere and lifted nearly ten feet.
Meant to be test flown only up to five times in 30 days, it survived Martian winters and dust storms to fly 72 times over 1,000 Martian days, changing its mission from test subject to a full-fledged scout for the rover Perseverance that brought it there.
Its service ended abruptly, however, on January 18 after it apparently damaged a rotor during a landing.
“The Little Helicopter That Could,” NASA Administrator Bill Nelson said in a video announcement on January 25, “has now taken its last flight on Mars.”
But, he added, “what Ingenuity accomplished far exceeds what we thought possible.”
In a press conference that day, Laurie Leshin, director of NASA’s Jet Propulsion Laboratory (JPL), which oversaw the helicopter’s development, said, “I look forward to the day that one of our astronauts brings home Ingenuity and we can all visit it in the Smithsonian.”
And while that may not happen for another decade at least, according to current planning, the Smithsonian’s National Air and Space Museum recently announced it has received the prototype for the Ingenuity Mars helicopter for display.
The popular museum on the National Mall—and its auxiliary Steven F. Udvar-Hazy Center in Chantilly, Virginia—have hundreds of objects on display having to do with flight on Earth, but this will be the first having to do with autonomous flight on another planet.
“It’s pretty much ready for display,” says Matt Shindell, the Air and Space Museum curator of planetary science and exploration. “We just need to figure out a good place for it.”
For its outsized historic achievement, the Ingenuity helicopter is disarmingly small, at less than two feet tall and weighing just four pounds. The device is mainly rotors, with four of them stretching about four feet from tip to tip. In order to achieve lift in Mars’ excessively thin carbon dioxide atmosphere—one one-hundredth of the atmospheric pressure of Earth—its rotors had to spin exceedingly fast, at 2,500 revolutions per minute.
“Basically, they’re spinning ten times faster on Mars in order to achieve lift in that really thin atmosphere,” Shindell says. And at that speed, it’s much more difficult for human controllers to react quickly enough to correct flight movement, even in a demonstration mode on Earth. “Slight changes can lead to the helicopter needing to react very quickly to whatever small change has happened,” he adds.
Early prototypes powered with a joystick ended up crashing. “Human reaction time was just not fast enough under the simulated Martian conditions,” Shindell says.
And once on Mars, the delay in communicating with human operators about 140 million miles away would lag between 4.3 to 21 minutes depending on orbital positions.
The solution was the use of “very small computers—basically cellphone computers—that could be used on a vehicle like this, so it could control itself and react at much faster speeds than a human operator would be able to react to correcting its own position and maneuvers,” Shindell says.
The autonomous power is what made Ingenuity a helicopter and not a drone, he says. “Drones on Earth are operated by human controllers. You can fly them in real time, but with the Mars helicopter, you can’t.”
The prototype that NASA donated to the National Air and Space Museum was affixed with small cables to power its successful free flight under simulated Martian conditions in JPL’s 25-foot-wide thermal vacuum chamber on May 31, 2016. It was this flight that demonstrated that a helicopter flight on Mars was possible. The finished Ingenuity helicopter on Mars, however, had a solar panel and a battery to power it up (despite the panel getting a little dusty from the planet’s famous red dirt).
The solar panel was also able to keep the craft sufficiently warm on a planet whose temperatures can drop to minus 195 degrees Fahrenheit. “Most people expected it to die during the Martian winter when temperatures got cold and it wasn’t able to keep itself warm overnight,” Shindell says. “But it somehow survived that.”
Ingenuity arrived affixed to the underbelly of the Perseverance rover that was dropped on the planet, which took off from Earth in July 2020 and arrived in February 2021. But it wasn’t clear the Ingenuity would even fly after it got there. So a great cheer came over JPL in April 2021 when its achievement was clear.
“This is the first time that something actually flew by generating lift in the atmosphere of another planet,” Shindell says. “So it is unique in that way.” (It was never tried on the moon, he adds, because there’s no atmosphere there whatsoever.)
Ingenuity’s success was hailed by NASA as its “Wright brothers moment” at the time. And indeed, a piece of fabric from the 1903 Wright Flyer was attached to the Ingenuity to underscore the connection.
“That’s a nice sort of echo of the Apollo missions, where Apollo 11 brought a little bit of fabric and wood from the 1903 Wright Flyer to the moon and then brought it back again,” Shindell says. “Little pieces of the Wright Flyer have been to space a couple of times.”
The success of the Ingenuity has led to talk of future helicopters on Mars that will have wheels and be able to collect samples dug by the rovers. And JPL is developing a Mars Science Helicopter that will have six rotors and be even more versatile.
“You can imagine in the future [that] you will have fleets of these Mars science helicopters flying around, bringing important payloads to parts of Mars that we’ve never been able to access before,” JPL Ingenuity team lead Teddy Tzanetos said at the January 25 press conference.
Over the 72 different flights, Ingenuity flew more than 128 minutes total, covering 11 miles, according to NASA logs. Its maximum ground speed reached 22.4 miles per hour, and it flew as high as 79 feet.
On its final mission, the landing was “some of the hardest terrain we’ve ever had to navigate over,” Tzanetos said.
Not because it was rocky—but because it wasn’t. Flying over bland, featureless terrain made it difficult to orient Ingenuity’s motion, causing it to strike the ground and break a rotor, making further balanced flights impossible. But even its demise provided a lesson for the future.
“We now know that that particular kind of terrain can be a trap for a system like this,” Ingenuity’s chief pilot emeritus Håvard Grip said at the press conference. “Backing up when encountering this featureless terrain is a functionality that a future helicopter could be equipped with.”
Ultimately Shindell says he hopes to have the Ingenuity prototype among the other Mars exploration items in the award-winning Exploring the Planets gallery, which opened in October 2022 when the first phase of the Air and Space Museum’s remodeling on the National Mall was complete.
“Ingenuity demonstrated how flight can enhance operational missions, and it’s helping us in the search for life on Mars,” Nelson, the NASA administrator, said in his video message. “And, like the Wright brothers and what they did back here on Earth in the early part of the last century, Ingenuity has paved the way for future flight in our solar system. And it’s leading the way for smarter, safer human missions to Mars and beyond.”