On the face of it, NASA's newest probe sounds incredible. Known as Dragonfly, it is a dual-rotor quadcopter (technically an octocopter, even more technically an X8 octocopter); it's roughly the size of a compact car; it's completely autonomous; it's nuclear powered; and it will hover above the surface of Saturn's moon Titan.
But Elizabeth Turtle, the mission's principle investigator at the Johns Hopkins Applied Physics Laboratory, insists that this is actually a pretty tame space probe, as these things go.
"There's not a lot of new technology," she says.
Quadcopters (even X8 octocopters) are for sale on Amazon these days. Self-driving technology is coming along quickly. Nuclear power is harder to come by, but the team plans to use the same kind of system that runs NASA's Curiosity rover on Mars. Everything that's going into Dragonfly is already being used somewhere else.
Which is not to say that the idea of a nuclear-powered drone flying around a moon of Saturn doesn't sound kind of crazy.
"Almost everyone who gets exposed to Dragonfly has a similar thought process. The first time you see it, you think: 'You gotta be kidding, that's crazy,' " says Doug Adams, the mission's spacecraft systems engineer. But, he says, "eventually, you come to realize that this is a highly executable mission."
NASA reached that conclusion when, after a lot of careful study, it gave Dragonfly the green light earlier this summer. "This revolutionary mission would have been unthinkable just a few short years ago," NASA Administrator Jim Bridenstine said when the roughly $1 billion project was selected in June. "A great nation does great things."
For Shannon MacKenzie, a postdoc on the mission, there's no destination that could be greater than Titan. The largest moon of Saturn, it has dunes, mountains, gullies and even rivers and lakes — though on Titan, it's so cold the lakes are filled with liquid methane, not water.
"It is this complete package," she says. "It's this really unique place in the solar system where all of these different processes are coming together in a very Earthlike way."
Turtle says these features are part of what made Titan a target. It also appears that the surface is covered in organic molecules. The climate is probably too harsh for those molecules to make the shift into life, but Turtle thinks Titan could provide clues about how the building blocks of life started on Earth.
"All of these materials have been basically doing chemistry experiments for us," she says. "What we want to be able to do is go pick up the results of those experiments to understand the same kinds of steps that were taken here on Earth toward life."
Titan has one more feature that's worth noting: Although its mainly nitrogen atmosphere is denser than Earth's, its gravity is far lower. That makes it the perfect place to take to the skies.
"The conditions on Titan make it easier to fly there than on Earth," says Peter Bedini, the Dragonfly project manager. A drone is actually a much better way to explore such a world than a wheeled rover.
Dragonfly will launch from Earth in 2026 and arrive on Titan in 2034. After it enters the atmosphere, it will literally drop from the back of the capsule that brought it and fly down to a set of sandy dunes on the surface. From there, it will make a series of "hops" over two years, sampling the ground and sending back data and photos.
Adams is confident Dragonfly will be able to safely buzz across Titan's terrain. Because it can take nearly an hour-and-a-half for a signal to reach Titan from Earth, it will have to fly autonomously. But, he says, there's not a lot to run into: "We make the joke if we hit a tree, then we win because we found a tree on Titan," he says.
Adams plans to leverage a lot of technology from the recent drone revolution here on Earth. Radars, motors and software can all be used, or relatively easily adapted, for Dragonfly.
There is one thing he can't bring, however: "We don't actually have a map. There's no GPS; there's no magnetic field even to orient yourself," he says. He says the drone will navigate by continuously photographing the landscape, creating its own "map" as it goes.
For now, the Dragonfly team is still working with drones here on Earth to figure out how to build systems and software the probe will eventually need. But Turtle says they have time before the 2026 launch. "There's a lot to do between now and then," says Turtle. But she adds, it's all very doable.
DAVID GREENE, HOST:
Earlier this summer, NASA announced that it would fund an ambitious new mission to send a quadcopter-style drone to a moon of Saturn. This drone will leave earth in 2026, but work has already begun on it.
NPR's Geoff Brumfiel has been visiting with the team of scientists behind this mission.
GEOFF BRUMFIEL, BYLINE: This drone will head to a moon called Titan. And the first thing to know about Titan is that it's cool - like literally, it's really cold.
ELIZABETH TURTLE: It's 94 Kelvin and negative 290 Fahrenheit.
BRUMFIEL: Zibi Turtle is head of the mission, which is being run out of the Johns Hopkins Applied Physics Laboratory. Turtle - it should come as no surprise - also thinks Titan's figuratively cool.
TURTLE: Titan is a really fascinating world. It's the largest moon of Saturn. It's the only satellite in the solar system that has a dense atmosphere. In fact, its atmosphere is denser than Earth's atmosphere
BRUMFIEL: And there's more Earthlike things about it. Titan has dunes, mountains, gullies, even rivers and lakes. Though, on Titan, it's so cold the lakes are filled with liquid methane, not water. Think of it as a little, frigid Earthlette (ph) floating around the outer solar system. And that's what has Turtle and her teams so interested.
Like Earth, Titan is home to a lot of different kinds of organic molecules. The climate's probably too harsh for those molecules to turn into life. But Turtle thinks Titan could provide clues to how life started here on Earth.
TURTLE: All of these materials have been basically doing chemistry experiments for us. And so what we want to be able to do is go pick up the results of those experiments to understand, you know, the same kinds of steps that were taken here on Earth toward life.
BRUMFIEL: But look, I haven't told you the coolest thing about Titan yet.
TURTLE: If you had a good way to keep warm and some oxygen with you to breath and put wings on, you'd be able to fly.
BRUMFIEL: What - you mean, like, flapping?
TURTLE: Exactly. A human being would be able to fly on Titan. It's that much easier to fly on Titan than it is on Earth.
BRUMFIEL: Titan's dense atmosphere and low gravity make getting off the ground a cinch. And that's why Turtle's plan is to explore with a drone rather than a rover. Down the hall from her office in a conference room, there's a giant quadcopter.
TURTLE: Sweet. I didn't know we had that - the larger one...
BRUMFIEL: This is fantastic. Look at this thing. Hi.
TURTLE: Before I forget...
DOUG ADAMS: Hey. I'm Doug Adams.
BRUMFIEL: Doug Adams is one of the lead engineers on the project. The drone he's showing me takes up the whole table. And it's only a fraction of the size of what they have in mind.
Oh, that's quarter scale?
ADAMS: That's quarter scale.
TURTLE: That's quarter scale.
BRUMFIEL: ...This thing's big.
TURTLE: It is.
BRUMFIEL: The real drone, known as Dragonfly, will be roughly the size of a compact car. Titan's distance from Earth means that nobody can fly Dragonfly by remote control. It'll have to be completely autonomous. And there's no way to recharge it, which - if you've ever owned a drone - you know needs to happen a lot. And at this point, you may be thinking what I was thinking - really?
ADAMS: Almost everyone that gets exposed to Dragonfly has a similar thought process. The first time you see it, you think, you've got to be kidding. That's crazy.
BRUMFIEL: But Adams says the mission really is possible using technology we use all the time on Earth. Quadcopter-style drones, for example, are all over the place. This one's just a little bigger. Self-driving technology is increasingly common - and bonus, it should be easy on Titan because there aren't any obstacles.
ADAMS: We make the joke, if we hit a tree then we win - right? - because, you know, we found a tree on Titan.
BRUMFIEL: Recharging is a problem, but they've got a solution for that, too - a nuclear battery. NASA actually already uses one on its Mars rover. Turtle says, as ambitious as Dragonfly sounds, it's just a bunch of old tech bolted together.
TURTLE: One of the strategies that lowers risk for a mission is to use proven technology (laughter).
BRUMFIEL: Yeah. But, I mean, you're building a nuclear-powered, self-driving drone for a moon of Saturn...
BRUMFIEL: ...So it is something new, isn't it? I mean, let's not...
ADAMS: It is...
BRUMFIEL: ...Not understate that.
ADAMS: So we won't understate that. However, as Zibi pointed out, the secret is to limit the miracles, right? We're assembling as many technologies that are already existing as possible and limiting what we have to do.
BRUMFIEL: Even Dragonfly's scientific instruments that it will use to take samples and send data back to Earth have been tested on other missions. In fact, what Adams is most worried about is something we all have at our fingertips here on Earth that he can't take to Titan.
ADAMS: We don't actually have a map. There's no GPS. There's no magnetic field even to orient yourself.
BRUMFIEL: The biggest challenge facing Dragonfly is how to find its way around. Then again, any good explorer should get a little lost, right?
Geoff Brumfiel, NPR News.
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