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Thursday, May 23, 2024

NASA Lands Ingenuity, the First-Ever Mars Helicopter

Very early this morning, NASA flew a small drone helicopter that its latest rover had toted to Mars, marking humankind’s first controlled and powered flight on another planet. Ingenuity stuck the landing—and space engineers are stoked.

“We’re ecstatic, of course,” said Matthew Golombek, a senior research scientist with NASA’s Jet Propulsion Lab, during a call with WIRED shortly after the Ingenuity team learned of the success. The data that trickled into JPL computers early Monday morning was “nominal,” he said—NASA-speak for a best-case scenario. “Anytime you've successfully landed a spacecraft, it's a pretty good moment,” Golombek said.

Ingenuity ascended about 1 meter per second, until it rose 3 meters—about 10 feet above Mars. The helicopter hung as evenly as its state-of-the-art electronics could allow, and then landed where it had been 40 seconds before. Then, Ingenuity pinged its Earth-bound engineers a message they’ve sought for almost a decade: Mission accomplished. The hovering drone sent back a black-and-white video of its own shadow, and the Perseverance rover’s high-resolution camera snapped shots of the flight and landing from a distance.

“We can now say that human beings have flown a rotorcraft on another planet,” MiMi Aung, the project manager, told her team after the flight as she stood in front of giant wall art that read “DARE MIGHTY THINGS,” the message that had also been encoded into the rover’s descent parachute.

The machines humankind has sent to Mars have gotten increasingly sophisticated since the first rover, Sojourner, rolled in 1997. That robot put the first wheels on Mars, and its cousins, Spirit, Opportunity, and Curiosity, followed carrying their suites of science experiments. But Perseverance—the largest of the bunch, which landed in February—has driven around the Red Planet with a helicopter in its belly. Ingenuity is NASA’s first attempt at flying a drone on another planet. The space agency and the contractors who participated in its design want to glean lessons from its flight data to design bigger exploratory flyers for future missions.

During a press conference held later Monday morning, Aung called it an “absolutely beautiful flight” as she watched the video sent from the rover. “I don’t think I can ever stop watching it over and over again,” she said.

The Sojourner technology demonstration in 1997 gave NASA the validation for subsequent rovers, JPL director Michael Watkins said at that press conference. “What the Ingenuity team has done is given us the third dimension,” said Watkins. “I think this is exactly the way we build the future.”

Ingenuity looks like a shiny four-legged mosquito rocking two sets of helicopter rotor blades and a solar panel on its head. It’s about 2 feet tall, and its 15-inch legs keep it upright on jagged alien terrain. Its 4-foot-wide carbon-fiber rotor blades spin ultra-fast to carry a body just big enough to house a battery, sensors, cameras, and the brain that makes each element work in concert.

Flying on Mars is way different than flying on Earth. Gravity is 62 percent weaker there, but the atmosphere is 99 percent thinner and provides much less lift. It would be like flying a helicopter at an altitude of 100,000 feet on Earth, where the record for high flying is less than 41,000 feet for a helicopter and 85,000 for a plane. Ingenuity’s rotor blades spin at up to 2,537 rotations per minute to make up for it—that’s about five times faster than helicopter blades whirl on Earth.

Because of its thin atmosphere, daily temperatures on Mars can swing by over 150 degrees, which makes the air density highly variable. Engineers had to account for this unreliable air cushion. “At sea level here on Earth, the pressure doesn't change by that much,” said Ben Pipenberg, an aeromechanical engineer with AeroVironment. The California aircraft company has been working with JPL since 2013 to bring the helicopter idea to life. But on Mars, he continues, “from our current operating point, we can vary the operating pressure by about 30 to 40 percent up or down and still fly fine.”

Each piece of the copter is crafted to maximize function and minimize weight. The blades weigh a total of 70 grams, less than a deck of cards. The whole $85 million drone weighs about 4 pounds—less than a gallon of ice cream.

Ingenuity’s real mission is to demonstrate flight on Mars and to log engineering data about how each of its mechanical and electronic organs function—it’s an experiment. “We have flown in an imagined Mars,” Ingenuity's chief engineer, Bob Balaram, told WIRED before the flight. “Imagined in our computers; imagined in our supercomputers; imagined in simulations; imagined in our testing facilities here on Earth. We want to see what is the stuff that we're missing.”

The main goal is just to fly and land safely: “That checks the box,” Balaram said. “Everything else after that is bonus.”

And there are a lot of potential bonuses. While flying, Ingenuity records the crosstalk between its brain and its sensor suite—an accelerometer, altimeter, inclinometer, gyroscope, and camera—to relay answers to questions like: “How stable can we keep this thing in air?” This data, logged 500 times per second, will be vital for future missions, partly because a helicopter could cover more ground than a slow-moving rover. (Perseverance white-knuckles the terrain at something like a blistering 4 centimeters per second—0.1 miles per hour.) NASA plans to send more ambitious flyers to Mars to scout ahead of future rovers, collect samples, and one day even help astronauts on crewed missions.

So far, Ingenuity has had a busy few weeks. NASA engineers designed the helicopter to lift off from Mars’ surface, not from the rover. So they tapped Lockheed Martin to create the packaging that protected Ingenuity through launch and landing and released it from the rover. They built its guitar-case-shaped undercarriage, which shielded the copter from dust and pebbles for more than a month after touchdown. They also had to design a super-lightweight system for linking the drone to the rover. "One of the most interesting things was the electrical connection to the helicopter," said Jeremy Morrey, an engineer with the Lockheed Martin team. JPL needed the robot connections to use high-power channels, which are traditionally quite heavy.

“Existing aerospace connectors are like military-grade giant threaded connectors—just one of them weighs some decent fraction of the entire helicopter. So those are completely out,” Morrey said. “So we had to invent something totally new, to make those electrical connections and survive all the environments and essentially add zero mass to the helicopter whatsoever."

On March 21, Perseverance began a series of steps that would finally release the case containing the copter. Over six days, controlled pyrotechnic blasts cut the cables and bolts that kept the copter in place. A small motor switched on, rotating the robot until it was upright. Latches snapped to drop the four legs into position. Ingenuity hovered above the Martian surface with its legs dangling, ready to feel red dirt. On March 30, there was one final snap to cut the last cords: Ingenuity now stood below the rover, like a very expensive freshly laid egg. Perseverance then rolled away from the flight path, and the helicopter got its first taste of Martian sunshine.

That sunshine is critical for this mission. Ingenuity will never return to the rover’s belly, so every ampere in its world will come from a solar-panel-charged battery. The juice flows to a motor powering its blades, and to its internal heater. (Nights on Mars can dip to –130 degrees Fahrenheit.) In order to know whether a machine like Ingenuity can endure on Mars and make repeat flights, the engineers have been keeping a close eye on how well its battery and insulation handle the cold. On April 4, JPL celebrated Ingenuity surviving its first night.

“The obstacles are just dropping one after another,” Morrey told WIRED two weeks before the flight. “So my stress level is dropping with each deployment step.”

NASA engineers also monitored how Ingenuity’s parts handled intense vibrational forces during launch, landing, and deployment. “We do some blade wiggles,” Balaram said, to check that the motors are in good shape. They also test-spun the blades at both low speeds—about 50 rpm—and high ones.

NASA had originally planned to fly Ingenuity as early as April 8, but it pushed that back to wait for the right conditions. "Ideal weather would have been one with the lowest possible wind,” Balaram said. “And that is, in some sense, the biggest risk we have, because we don't get to control that." NASA scrubbed an April 11 flight after the success of a high-speed blade test couldn’t be confirmed before an onboard timer expired. The team scrambled to push a fix, and by April 16, Ingenuity cleared the test.

“Similar to what the Wright brothers did,” he adds. “I’m sure if you asked them when their first flight was, they would say ‘probably no earlier than’ some date.”

For the Ingenuity team, that Wright brothers moment came around 3:30 am Eastern time on April 19. It took a few hours for orbiters high above the Martian surface to relay the message of the success to folks on Earth.

NASA hosted a livestream of its engineers downloading the data. The scene felt less like an unboxing video and more like a waiting room. Team members sat around a long U-shaped table with a model of Ingenuity at the center, facing them all. “It’s flight night! Whoo!” said Taryn Bailey, a JPL mechanical engineer, during an interview for the livestream, promising that Ingenuity’s success would open a doorway for the human exploration of Mars. Just as she began answering a question from the public on the livestream, a team member radioed: Data was trickling in.

Then, around 6:52 am Eastern time, flight control confirmed success. The room erupted in claps and cheers as Ingenuity sent back a black-and-white photo of its own shadow taken while hovering.

“We now have our Wright Brothers moment,” Aung said during the livestream. Data plotted on graphs showing the helicopter’s altitude shot up, leveled off, and dropped down, mirroring what the 4-pound drone had done 180 million miles away, three hours earlier. “History does tell us that soon after that first flight, Wilbur and Orville did go right back to work,” she continued.

NASA engineers intended for this first flight to be similar to trial runs they’ve done in their 25-foot-wide Mars simulation chamber on Earth. Data from this flight will give engineers an apples-to-apples comparison of flying on a simulated Mars versus the real Mars. AeroVironment engineer Pipenberg said that lessons from Ingenuity are also teaching the company’s engineers how to improve their telecom pseudo-satellites which fly at 96,000 feet above Earth.

Golombek, who cheerily told WIRED he’d be celebrating the early morning landing with a pot of coffee, is particularly excited about the images Ingenuity will collect of Martian geology. “When you're on the surface, your view is different than when you're up higher,” Golombek said. Ingenuity’s cameras will give NASA an unprecedented high-resolution vantage point, he continued, “to cover more area and go places that of course the rover can't go.” Rovers can’t mount steep inclines or terrain that’s very soft or uneven like Mars’ ripples. But a helicopter couldn’t care less about rugged terrain, and that’s great news for people like Golombek who want to get a good aerial look at rocks.

JPL confirmed during the press conference that Ingenuity’s solar panels, batteries, and blades survived the flight and landing. “All in all, it’s in a perfect state,” said Balaram.

Using data from Ingenuity’s many sensors, the engineers reconstructed every second of its flight, from its gentle pivot in midair to a light bounce upon landing. “To see it now finally happen on Mars, and happen exactly the way we imagined it, is just a really incredible feeling,” said Håvard Grip, the copter’s chief pilot at JPL, during Monday morning’s press conference.

NASA plans to send Ingenuity on four more Martian flights. The second will explore flying laterally, and the third will let the copter venture farther away from its launch spot. “Depending on what we see in the first three, we will do something perhaps more bold or aggressive or adventurous,” Balaram said of flights four and five.

On Monday, Aung announced that the agency is targeting Thursday, April 22, for the second flight date. NASA also plans to switch on Perseverance's microphones during Ingenuity's future flights, to hear what it sounds like from the rover’s vantage point. (But first, they want to be sure that the microphones don't interfere with communications.)

Overpreparing is the space agency’s MO. But they are ready to be surprised—“hopefully pleasantly surprised,” said Balaram—by what they learn from flying the copter. “Just like little Sojourner more than 20 years ago taught us how to operate a rover on Mars,” he continues. “That all comes from learning. And I'm not sure how you do learning without surprise.”

Update 4-19-2021 2:34 pm: This story was updated to provide additional comments and information from NASA's Monday morning press conference.

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