When NASA’s latest Mars rover, Perseverance, launches this week, the robot will have a tiny stowaway on board: a small box-shaped helicopter. If the copter manages to successfully hover above the Martian terrain, it’ll be the first time that a human-made vehicle has ever flown on another world — and it could open up a whole new way of exploring the Solar System in the future.

The helicopter, named Ingenuity, is not the main focus of the rover. Perseverance’s biggest goal is to look for signs of life on Mars and dig up samples of dirt that could one day be returned to Earth for study. But engineers managed to find room under the rover’s belly to stow the tiny helicopter. At some point during Perseverance’s journey, the rover will deploy Ingenuity onto the surface of Mars, where it will spin up its rotor and attempt to take off.

This interplanetary experiment hopes to provide a new vantage point for exploring Mars, beyond the current — limited — options. Mars orbiters can’t get the high-resolution imagery that a spacecraft can get near the ground. Landers can only get information from a fixed location, while rovers can only move so far, with limited information about what lies ahead. But a helicopter can act as a scout, doing reconnaissance for other spacecraft or reaching hard to access areas.

That scouting ability could be super helpful if humans ever make it to the Martian surface. “Really flying ahead and then getting high definition images to inform humans and rovers for traverses will really advance the exploration of the world,” says MiMi Aung, the project manager for the Mars helicopter at NASA’s Jet Propulsion Laboratory. “Being able to fly will add an entirely new dimension to exploration.”

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There’s still a very big hurdle to flying on Mars: the atmosphere. The air surrounding the planet is just 1 percent the thickness of Earth’s atmosphere. With so little air to move around, achieving lift on Mars will be very difficult. The low gravity on the surface of Mars helps; it’s about 38 percent that of Earth’s gravity. But even with that assist, a vehicle still can’t fly on Mars with the same technologies we use to fly on our planet.

For anything to get off the ground in that environment, it has to be super lightweight, and the propellers must be moving incredibly fast. But they can’t go too fast, or things start to get dicey. “You can’t keep going faster and faster, because what then happens is that the tips of your blades start approaching Mach one,” Bob Balaram, the chief engineer for the Mars helicopter at JPL, tells The Verge. “They start wanting to go supersonic, and you don’t want to even let them go transonic because you get much more turbulent effects.”

With these limitations in mind, a team of engineers at NASA JPL set out to invent the first Martian helicopter. The team behind Perseverance set the copter’s dimensions, determining that the rover could accommodate a tiny helicopter with blades that reached about 1.2 meters — or about 4 feet — wide. That ultimately dictated the weight the helicopter could be, putting it at just 1.8 kilograms, or roughly 4 pounds. Creating such a small-sized vehicle filled with electronics is only something that could have happened today, says Aung. “A few decades ago, the technology of lightweight electronics — computers, sensors, cameras, gyros — all of those were not available,” she says.

The final design of the copter looks like a daddy long-legs spider with an intricate headpiece. The main body of Ingenuity is a box with four protruding limbs that keep the vehicle upright on the ground. Four carbon-fiber blades are mounted on top, as well as a solar panel to generate power. Those blades are designed to spin up to 2,400 revolutions per minute — or 40 times a second. The blades of a typical Earth-bound helicopter spin at around 450 to 500 revolutions per minute. However, Ingenuity’s blades shouldn’t exceed the speed of sound, reaching less than 0.7 Mach.

Building Ingenuity was only half the battle, though. The team had to make sure that the helicopter could actually fly on another world. “Parallel to the invention of the helicopter is also: ‘How do you test it?’” says Aung. “Because it has never been done before.”

Fortunately, NASA’s Jet Propulsion Laboratory is outfitted with giant testing rooms that could be used for the job. A large chamber called the Space Simulator at JPL can re-create a total vacuum as well as manipulate all of the extreme temperatures that a spacecraft might experience after leaving Earth. To test Ingenuity, the engineering team turned the chamber into a Mars-like environment. “We basically took that chamber pumped it down to near vacuum and backfilled it with carbon dioxide, so that the room now contains Mars-like atmospheric density,” says Aung.

Another testing challenging remained: getting rid of Earth’s weighty gravity. To simulate the lower gravity of Mars, the engineers attached a lightweight tether to prototypes of Ingenuity whenever they were flying in the test chamber. Called the Gravity Offload System, the tether provided a constant upward tug on the spacecraft, making it feel as if the vehicle was in 38 percent of Earth’s gravity.

That testing helped shape the final design of Ingenuity. During the first couple of flight tests, the team found that the blades on the test helicopters kept flapping up and down. The tendency to flap happens with Earth helicopters, too, since the blades are long and spindly. But the thick atmosphere dampens that effect. The thin Martian atmosphere, on the other hand, doesn’t reduce that flapping.

“That was a bit of a discovery for us when we did the first flights,” says Balaram, adding that the flapping could have interfered with the helicopter’s controls. The solution? The engineers made the blades extra stiff, much stiffer than a normal helicopter of a similar size would be on Earth.

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The team conducted dozens of test flights in various extreme conditions — including deep cold to simulate the Martian nights that can reach -130 degrees Fahrenheit, or -90 degrees Celsius. Now, after all of that hard work, it’s time for Ingenuity to embark on its journey. To get to Mars, the copter will ride folded up on the underside of Perseverance, covered by a shield for protection. When the rover gets to Mars and finds just the right spot, Ingenuity will do some complicated gymnastics, unfurling into its final shape with its legs pointing toward the ground. It’ll then drop to the surface, as Perseverance rolls away and leaves it behind.

The team has been given just 30 Martian days to operate Ingenuity, which is roughly 31 Earth days. The very first flight will be simple: the copter will try to take off and climb to a height of about 10 feet, or 3 meters, hovering up there for 30 seconds or so. It’ll be short, but it’ll determine if all of the engineers’ hard work paid off. “I think I’ll feel like: finally, our kid, so to speak, is in the environment that it’s been developed for all these years,” says Aung.

Ingenuity will do up to four short flights, pushing the envelope with each progressive takeoff. No flight will last longer than about 90 seconds. But Ingenuity could reach up to about 15 feet, or 5 meters, high and travel horizontally by about 160 feet, or 50 meters.

All of these flights will have to be autonomous, thanks to the long lag time in communication between Earth and Mars. The team will send a list of commands to Ingenuity, and it will perform all of the steps on its own. The plan is for the helicopter to capture images when it flies, and it’s possible that Perseverance may also snap some far-off images of Ingenuity hovering in the air.

At the end of the day, Ingenuity is a technology demonstration, which is why its flights are meant to be short and straightforward. But it could prove that flying machines can be valuable for future missions to Mars. Engineers are already working on designs for larger helicopters that weigh up to 44 pounds or 20 kilograms. Larger copters could carry much more significant science payloads and nicer cameras than what Ingenuity has now.

But before you can walk, you have to crawl first. And that’s what Ingenuity is all about. “Hopefully we’ll have what I like to call our ‘Wright Brothers moment,’” says Balaram. “But it’s a controlled flight on another planet.”

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