Why flying a helicopter on Mars is so damn hard

On Earth, humans put more than a century of work into the art of flying. On Mars, we’re just getting started.

NASA’s four-pound helicopter, Ingenuity, touched down on the the surface of Mars on April 3 and will begin test flights in early April. It will be the first time humans have flown anything on another planet. 

In a nod to the Wright brothers' first flight, it’s carrying a tiny piece of the plane that flew at Kitty Hawk. If all goes well, Ingenuity could take up to five 90-second flights over 30 sols, or Mars days, which are slightly longer than Earth days. 

For decades, scientists have examined the surfaces of moons and planets from spacecraft high above. Rovers provide a closer look, but are painfully slow. Ingenuity has the advantage of flying low — only 10 to 16 feet in the air — while traveling relatively fast. It’s equipped only with a camera. But future drones could carry more tools. 

“It represents opening up a new avenue of space exploration,” said Josh Ravich, mechanical lead on Ingenuity. “It opens a lot of possibilities not just for Mars, but for any body with an atmosphere.”

One proposed mission to Saturn’s moon Titan features a drone dubbed Dragonfly. Data from Ingenuity could help make it a reality.

The question remains, though: Can Ingenuity fly? 

That’s no simple task.

Different planet, different atmosphere, different rules

If the flight tests begin in April as expected, Mars will be anywhere between 260 million and 330 million kilometers away from Earth. At that distance, it would take up to 15 minutes for a signal from a pilot to reach Ingenuity, a delay that would make it nearly impossible to control the drone manually. 

Even if scientists did have someone on the surface of Mars with a joystick, NASA Jet Propulsion Lab (JPL) researchers found out years ago that even the best drone pilots have trouble navigating in a Mars-like atmosphere, which is only about 1 percent as dense as Earth’s. 

Because there are fewer molecules to push off of, Ingenuity’s helicopter blades have to rotate between 2,000 and 3,000 times per minute, compared to 300 to 500 on Earth. To account for increased vibrations, Ingenuity’s nearly four-foot-long blades are much thicker near the rotor than the tips, affecting the way it handles.

Around 2014, a couple years before Ravich joined the Mars Helicopter team, he said the researchers attempted to fly an earlier version of the drone in a vacuum chamber.

“They had a really experienced drone pilot, like a private toy drone pilot, try to joystick it by hand,” he said. “It doesn't work the way you think it would. You try to move it one way and it goes the other way. It was a good lesson they learned quickly that, yeah, a human couldn't fly it.”

Their solution was to outfit it with a computer and sensors so it could control itself, adjusting on the fly to changes in speed, direction, and altitude.

Solving the Ingenuity puzzle

Considering the thin atmosphere, engineers had to thread the needle between providing enough power for the rotors and computer, and making it light enough to fly. 

For processing data on Ingenuity, NASA turned to Qualcomm, who was able to provide a Snapdragon 801 processor — the same you'd find in a Samsung Galaxy S5. The lightweight, efficient processor was able to handle the rigorous testing that NASA threw at it, said Dev Singh, GM of robotics, drones, and intelligent machines at Qualcomm.

“Keeping the                                                                               electronics warmenough to actually                                                           Work safely is a trick” “They tested it with radiation,” he said. “While other processors just disintegrated, our processor made it through all of that … It can run the 4K camera. It can run all the rotors. It can do the machine learning and obstacle avoidance.”

“They tested it with radiation,” he said. “While other processors just disintegrated, our processor made it through all of that … It can run the 4K camera. It can run all the rotors. It can do the machine learning and obstacle avoidance.”

One key ingredient to Snapdragon’s success is its power efficiency. Because it needs less power than other processors, Ingenuity can have a smaller battery. 

“Batteries are really heavy, so if you don't need them, why take more?” said JPL’s Ravich.

Ingenuity’s solar-charged battery powers the rotors, computer, and heating system to keep the whole thing from freezing. Mars is cold, sometimes reaching -110 degrees Fahrenheit or lower on cold days.

Qualcomm’s processors are only rated to work in temperatures ranging from about 255 F down to -40 F, Singh said.

“Have you ever tried to start your car when it's -40? It doesn't always turn on,” Ravich said, laughing. “Keeping the electronics warm enough to actually work safely is a trick.”

The 90-second flights don’t actually take that much power. Most of the battery energy goes to heating.

The future

Plans for a Mars helicopter have been in the works since the late ‘90s, Ravich said. 

The team "had been playing around with it for a while and it wasn't until around the 2014-ish timeframe that it really got some traction,” he said. By 2018 they were testing flights of the current Mars helicopter model. 

“We're really excited,” Ravich said about the team. “We put a lot of our heart into this and it's still amazing to us that we're there and we got this opportunity to try to fly.”

A successful flight would pave the way for more helicopter missions on Mars and other planets and moons in our solar system. As Qualcomm’s Singh pointed out, drones can cover much more ground than a rover. Curiosity took nine years to travel less than 25 kilometers. 

“Think about the future of Mars exploration, you could cover 24 kilometers in an hour, flying and scouting,” Signh said. “If you send five of them, you could probably cover Mars in five years and have pictures of different elements.”

Exploration is one thing. In the future, Ravich said he could picture helicopters on Mars helping astronauts. 

“One of my favorite goofy uses for it is, if you're an astronaut and you forget your wrench back at your base and you don't want to go back and get it yourself,” he said with a laugh. “Just send a helicopter to pick it up for you.”

For the sake of future, forgetful astronauts, let’s hope this thing works.

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