When America first dreamed of sending astronauts to another world, German-American rocket engineer Wernher von Braun didn’t want to go to the moon. He wanted to send dozens of people to Mars. He envisioned a winged craft soaring through the Red Planet’s atmosphere, landing gently on the rust-colored surface. And though earthlings quickly learned that traveling to another planet isn’t so easy, the fantasy of flying on Mars never died.
And now, that dream is on the verge of being fulfilled. On July 22, NASA plans to launch its Mars Perseverance rover. But there’s also a robotic hitchhiker onboard; this small, solar-powered helicopter, named Ingenuity, is on a mission totally independent from the rover. While Perseverance searches for signs of alien life, Ingenuity will prove it’s possible to fly in Mars’ thin atmosphere. The data it gathers will help engineers build even larger helicopter drones for the Red Planet. And if it works, the long-term impact could be a game changer for Mars exploration.
Standing less than 2 feet tall and weighing less than 4 pounds (on Earth), Ingenuity has relatively limited abilities. It's designed to take off, hover no more than a few dozen feet above the surface, maneuver through Mars’ thin air and land on flat terrain. But future Mars helicopters could potentially be much larger and more capable, allowing them to explore expansive or hard-to-reach areas far more quickly than traditional rovers. These next-generation aerial robots could even serve as scouts that collect samples and return them to landers or wheeled rovers for scientific analysis.
“Sojourner, this tiny little rover the size of a microwave, paved the way for Curiosity and Perseverance,” says Bob Balaram of the Jet Propulsion Laboratory, Ingenuity’s chief engineer. And though Sojourner was small, the two most recent rovers are both the size of cars. Balaram sees the progression of Mars helicopters playing out much the same way.
But first, Ingenuity must prove it can fly — a test Balaram has waited decades for.
The History of Flying on Mars
More than a dozen martian aircraft have been seriously considered over the last half century, and most of those projects were gliders. Only a small number of prototypes ever made it to testing; one glider, called BIG BLUE, was dropped from an altitude of 100,000 feet above Earth’s surface. These fixed-wing aircraft were mainly designed to be dropped from a spacecraft orbiting Mars; when the glider got released, its wings would deploy, helping it gently coast down to the surface, all the while gathering bird’s-eye views of vast features below, like Valles Marineris.
But gliding is basically the best you can do on the Red Planet with current wing-based technology. If you managed to land an airplane on Mars, it’d be nearly impossible to take off again. That’s because Mars’ atmosphere is some 100 times thinner than our own.
On Earth, commercial airplanes cruise at 35,000 feet because the air in our stratosphere is thinner — so there’s less drag, hazardous weather and turbulence. But to reach air as thin as that found just above Mars’ surface, a commercial plane on Earth would have to ascend to 150,000 feet. That’s almost half the distance to the boundary of space called the Kármán line, which begins at an altitude of about 62 miles. So for any hope of flying on Mars with winged craft, you’d need to construct a runway where you could reach ultra-high takeoff speeds.
“You have to be going at a fairly decent clip to generate enough speed for liftoff [on Mars],” Balaram says.
Planes and gliders aren’t the only aircraft that struggle to fly on Mars, though. At one point, French scientists were nearly set to send a balloon-borne mission to Mars. However, they ran into major troubles during testing, forcing them to shelve the idea. The balloons proved unwieldy, difficult to inflate and nearly impossible to control in any significant wind.
A Drone for Mars
During the mid-1990s, Balaram was a young engineer at NASA's Jet Propulsion Laboratory, where other engineers were already toying with designs to fly fixed-wing aircraft on Mars. He’d even worked on some Mars balloon studies himself. But Balaram had gotten bored with the work he was doing, leading him to search for something new. That’s when he heard about a Stanford University professor’s research using tiny, coin-sized robots to monitor things like air and water pollution on Earth.
Balaram realized that the flight dynamics of these small robots were similar to what a larger aircraft would experience while flying in Mars’ thin atmosphere. So, he wrote a proposal and built a prototype to prove a small helicopter could indeed fly on Mars. The idea appeared to be gathering support. But then, before it could be attached to a mission, Balaram’s helicopter project was unceremoniously shelved due to NASA funding cuts. His project remained in limbo as he moved on to working on Mars rovers and other efforts.
In 2015, the world finally caught back up with Balaram’s early vision. A higher-up at JPL heard an eye-opening talk about the ways drones were revolutionizing the world. So he asked staff if they could send a drone to Mars — and someone recalled Balaram’s project. The engineer gave a briefing, and before Balaram knew it, he was dusting off his Mars helicopter concept. The refined project, now ready for launch, was rebranded as Ingenuity in a naming contest earlier this year.
In its final design, Ingenuity weighs just 4 pounds and stands 19 inches tall. But despite its petite frame, Mars’ thin atmosphere means the craft needs two sets of rotor blades that span some 4 feet each. Plus, to generate enough lift, the blades must spin at some 2,800 rotations per minute — or about 10 times faster than typical blades on an Earth-based helicopter.
The Small Electronics Revolution
Like the failed aircraft plans that came before it, things won’t be easy for Ingenuity. On Earth, drone pilots know that their quadcopter batteries won’t last as long when flying at high altitude, where the air is thinner and they must work harder to stay aloft. But Mars takes that to the extreme.
Even Balaram now thinks NASA would have struggled to build and fly the helicopter concept he first envisioned in the 1990s. But the years since have brought about a revolution in miniaturized electronics. Cellphone technology serves as a prime example of how a very small package can be filled with powerful computers, cameras and batteries. Meanwhile, enormous advancements in solar power have allowed for more compact and efficient designs. So by waiting a few decades, Ingenuity’s engineering team got by without having to invent and test all-new technologies.
Instead, Ingenuity is powered by off-the-shelf lithium-ion batteries, which are charged using a system of small solar panels. It has a cellphone-style camera that can take color photos, as well as two downward-facing black-and-white navigational cameras — which are also now available on consumer drones.
“There have been advances in all these supporting technologies; solar panels, computer processors, sensors and systems,” Balaram says. “Those are the kinds of things that made this possible.”
The Cold, Martian Night
But despite the banality of some of Ingenuity’s core components back on Earth, success for the upcoming Mars helicopter is far from guaranteed. All of the toughest tests, like pioneering air travel on Mars, still lie ahead.
With NASA’s rovers, the space agency can conduct extensive driving tests across the rocky deserts of Earth. But to simulate flying through Mars’ thin air, Balaram’s team had to build an entirely new kind of wind tunnel. There was just nothing else that could simulate the Red Planet’s unique atmospheric conditions.
The team practiced flying in a 25-foot-wide, 85-foot-tall chamber full of the gas mixtures found on Mars: roughly 95 percent carbon dioxide, 2.5 percent nitrogen, 2 percent argon, a fraction of a percent oxygen and a smattering of trace gases. After testing, they’d plug their measured flight details back into computer simulations to continue testing virtually.
To evaluate the drone’s landing abilities, the team simply took it outdoors and flew it over different terrain to see how it handled setting down on various rocks and soils. “The test program had to be invented from scratch,” Balaram says. “That was one of the major challenges.”
But Ingenuity isn’t just an aircraft; it’s a spacecraft, too. It has to survive radiation and temperatures unlike anything aerospace engineers ever have to deal with. It’s so cold on Mars that just one-third of the helicopter’s power can be used for flying. The rest has to be spent warming the craft’s electronics to prevent them from freezing during the frigid martian night, where temperatures can drop down to nearly –200 degrees Fahrenheit.
All these challenges mean Ingenuity’s main goal is experimental rather than to return actual scientific results from Mars. The space agency has also given Ingenuity’s engineers some breathing room on its tests. They aren’t sure how many flights Ingenuity might make before its components start to break, so as a technology demonstration the helicopter was allowed some shortcuts that larger flagship missions don’t get, like using off-the-shelf parts without extreme screening.
“If they see enough thermal cycles, they will start breaking,” Balaram says. “We don’t know when that will happen, but it can’t continue forever.”
Perseverance, the Delivery Rover
If it survives just one flight on Mars, NASA will consider the mission a great success. However, they have plans for up to five test flights, which will begin almost as soon as Perseverance touches down on Mars.
Once the rover lands, the six-wheeled robot will set off on its own mission while also searching for a place to deploy Ingenuity as soon as possible. The only real requirement is that the helicopter’s test site be flat and open.
“It’s no accident the Wright brothers picked Kitty Hawk. They didn’t go to Yosemite,” Balaram says, pointing out the historic site’s relatively flat, sloping hills. “This is our Wright brothers moment on another planet. We’re going to go out of our way to get dropped off in relatively easy terrain.”
After roughly 30 days, Perseverance will leave Ingenuity and continue on its way with no other plans to fly the helicopter again. After all, throughout its entire life, Ingenuity’s top priority will be to avoid crashing into NASA’s multibillion-dollar Perseverance rover. This is why the rover and helicopter will be required to put several hundred feet between each other before every test flight. Once Ingenuity proves it can fly, NASA sees it as simply not worth the risk of more tests while the off-the-shelf components continue to degrade.
“Perseverance has been very accommodating and given us 30 precious [martian days] out of a two-year window to dedicate toward this particular technology-demonstrating experiment,” Balaram says. “That’s a big commitment.”
But Balaram says that, in theory, the team’s little helicopter could be capable of much more. If their testing here on Earth hints at what’s possible on Mars, Ingenuity could soon surprise space fans. It may also leave NASA with the tough decision of whether or not to abandon the drone.
Their only real limitation is the mechanical dampers used in Ingenuity’s legs to soften the landing, which can last about 50 flights. Beyond that, the helicopter could theoretically last until winter — some six months after reaching Mars — when it will be too cold to survive.
“If this does work, in the future you can imagine more exploration with larger helicopters that can carry between 1 to 4 kilograms [2 to 9 pounds] of payload,” Balaram says. “I can easily imagine a mission where a helicopter fetches a sample and brings it back to a rover looking for something like life.”
And what’s more, Balaram says he’s already working on designs for those next-generation aircraft. They just need Ingenuity to gather a little data first.