As little as two years ago, nobody outside of a very small group of scientists and engineers had ever heard of “space helicopters.” Then, on 19 April 2021, NASA’s Ingenuity helicopter lifted off from the surface of Mars, flew around, and landed—proving that it was, amazingly, possible to fly in the thin Martian air.
Since then, the plucky helicopter (which masses a mere 1.8 kilograms) has proven itself not only capable of flying in conditions equivalent to those four times higher than the summit of Mt. Everest, but of being a useful scout for NASA’s Perseverance rover, for which it has now flown more than 40 missions. “[It] is the first aircraft in history to operate from the surface of another planet,” says its chief pilot, Håvard Grip, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
But it’s unlikely to be the last. Not only are there plans to send two more Ingenuity-class helicopters to Mars to help with the Mars Sample Return mission, scheduled for launch in 2027, but NASA is well under way in designing a helicopter called Dragonfly, scheduled to be launched for Saturn’s moon Titan the same year.
The new Mars helicopters are a direct result of Ingenuity’s success. “We originally sent Ingenuity to Mars as a technology demonstration,” Grip said at the meeting of the American Geophysical Union in Chicago, Illinois, “but Ingenuity far exceeded those original objectives.”
The first flight, he admits, was a nailbiter. Ingenuity is a gossamer thing of spindly legs and thin high-speed rotors that looks more like a toy than a $US 80 million research project. Not only was it so difficult to fly under Martian conditions that in lab tests no human pilot had been able to control the prototype (requiring the development of a very fast-acting robotic control system), but all it would take would be an awkward landing on a 10-centimeter rock to topple it on its side where it would likely spend the rest of eternity in the Martian dust. “We were scared to death,” Grip says.
But it worked and then scientists started finding ways to expand its capabilities. First, they learned how to scout ahead, looking for safe landing spots. Initially, the idea was to leave from a safe base, fly out about half as far as it could go on a single hop—photographing what it saw en route—then return to its prior safe haven. While it was recharging its batteries, scientists would examine the images and pick the next safe landing zone.
That worked, but it was slow. Ingenuity has a flight range of about 700 meters. That meant it could only scout 350 meters ahead before returning for the data to be processed. Then it could hop to the new safe haven, land, recharge, and start the process over. It took two flights (and recharge cycles) to go 350 meters—an average of 175 meters per flight, rather than the 700 meters it was capable of. Too slow to be useful.
Read more: Explainer: The chemistry of Titan.
To fix this, the engineers got innovative. From space, they could see the difference between rocky terrain and smoother terrain, but there was a limit to the size of the rocks they could see. One-meter boulders were easy. Ten-centimeter saucer plates of the type that could upend Ingenuity were invisible.
But the geological processes that form rocky and smooth terrain aren’t random, says Ralph Lorenz, of the Applied Physics Laboratory (APL) at Johns Hopkins University, Laurel, Maryland, which is designing the Dragonfly mission, and author of a book about Ingenuity and Dragonfly. “There’s a general correlation such that if an area is rocky for 10-centimeter rocks, it’s also rocky for one-meter rocks you can see [from] orbit,” he says.
That doesn’t mean Ingenuity won’t someday get unlucky, and do the human equivalent of breaking an ankle on a cobblestone. But it’s a lot better than giving up and being left behind. And even when its demise comes, it will have paved the way for a future generation of Mars helicopters, accompanying not only the Mars Sample Return mission, but future human missions.
“My personal dream [is that] one day we’ll have astronauts on Mars and there’ll be fleets of vehicles zipping around helping,” says Theodore Tzanetos, who is part of the sample return program at JPL.
Meanwhile, there’s Dragonfly. “Dragonfly is in its preliminary design phase,” says its principal investigator, Elizabeth Turtle, also of APL, “[but] we are working toward a launch date in 2027 and arrival at Titan in 2030.”
Unlike Ingenuity, which looks like a conventional (albeit spindly) helicopter, Dragonfly is an ‘octocopter,’ basically an eight-rotor drone whose extra rotors provide backup in case one or more fails. It’s also nearly 300 times heavier than Ingenuity—feasible because Titan has an atmosphere 1.5 times denser than Earth’swith a surface gravity a bit less than the Moon’s, making it pretty much the perfect place to fly a helicopter. With one problem: it’s wickedly cold. “The surface temperature is 94 Kelvin (-179°C),” Turtle says.
Scientifically, that’s interesting because on Titan, water ice plays the role of granite, while methane plays the role water does on Earth, producing methane clouds, methane rains, methane lakes, methane rivers, and methane seas. That makes it an incredibly appealing place to explore, but also a bit of a technological challenge. “There are some aspects, like the low temperatures, that need particular attention,” Lorenz says.
That said, neither Ingenuity nor Dragonfly are acting as drivers for new technology in the way the 1960s Moon-shot missions drove everything from the development of Plexiglas and Teflon to food-safety protocols designed to assure that no NASA astronaut would ever get food poisoning, and now taken into consideration by food processers worldwide.
The Apollo program cost roughly $US200 billion, adjusted for today’s prices. Ingenuity and Dragonfly cost $US80 million and $US850 million respectively (not counting launch costs). The difference means that rather than being technology drivers, they are drawing on existing technology and finding ways to repurpose it for space exploration.
Much of that derives from the explosion in what Lorenz calls urban air mobility vehicles—the innovations that are rapidly leading toward automated drone delivery services, aerial police protection, and a host of other applications here on Earth.
Read more: Mars helicopter’s odyssey.
Part of what’s making the new wave of low-cost space exploration possible, he says, is an improvement in electric motors, driven by the development of strong magnets and motor-drive electronics, “all part of the drone revolution.” Equally important are advances in autonomous navigation derived from now-unclassified technologies first developed in the 1970s and 1980s to help cruise missiles find their targets.
Apollo’s giant budget drove a suite of innovations valued at perhaps $US 100 billion per year.
Today’s lower-budget programs are better at showcasing what’s possible with modern off-the-shelf technology.
And if that means space helicopters on Mars and Titan, maybe my next car really will be an autonomous flying vehicle. George Jetson, here we come!
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