Future extraterrestrial rovers may be powered remotely by high-energy laser beams shot through miles of thin fiber-optic cables. This new technology could allow robotic probes to penetrate thick layers of ice to explore Antarctic lakes or the subterranean oceans on icy moons like Europa or Enceladus, and even power a new kind of rocket into space.
“Our modest goal over the next three years is to use a 5,000-watt laser to send a cryobot through up to 250 meters of ice,” inventor and explorer Bill Stone, who presented the new concept today at NASA’s Astrobiology Science Conference in Atlanta, told Wired. “All the data show there are no show-stoppers for doing that. But from my standpoint, this is child’s play compared to what we could do.”
The problem for scientists hoping to study the ocean of liquid water believed to lie beneath Europa’s icy crust has always been the amount of energy required to melt through miles of ice. Solar power won’t work below the surface, and batteries won’t last long enough. And while a small nuclear reactor might have enough power, the footprint would be too large for a device NASA might realistically expect to drill miles down. A nuclear device couldn’t be tested in Antarctica either, because of international treaty restrictions.
The new robot, a 6-foot by 10-inch cylinder called VALKYRIE, would leave its power plant on the surface, along with a high-energy laser. The laser beam would travel down miles of fiber-optic cable that unspools as the robot penetrates the ice, explores the ocean collecting samples and then melts its way back up to the surface, sealing the hole behind it.
The team has built and tested the laser-fiber-optic power system at Stone’s lab in Texas and plans to test it with a working cryobot at Alaska’s Matanuska Glacier in June 2013.
“All great ideas need fundamental building blocks,” Bart Hogan, an optics expert and principal engineer on the project, said. “Ten years ago, the fundamental technology for this project wasn’t there.”
Stone’s team combined simultaneous advances in several fields, where the researchers weren’t always aware of each other’s work. “It’s like you have all these groups making lenses for better eyeglasses, and someone says, ‘Hey, we can put these lenses together and build a telescope,’” Hogan said.
Stone has been designing and building robotic explorers for years. His first-generation bot, called DEPTHX, ventured deep into flooded Mexican hydrothermal springs without human control between 2003 and 2007, eventually descending more than 1,000 feet to find and collect microbial species previously unknown to science, creating 3-D maps and sampling mineral-laden water as it went. His next version, called ENDURANCE, did the same sort of thing in 2008 and 2009, but within a freshwater lake hidden beneath a permanent ice cap in Antarctica, creating the first 3-D chemistry map of a sub-glacial lake. But these robots were lowered into the water by humans. None of them had to melt through ice on their own.
Stone hit on the solution to the power problem as he tested ENDURANCE in advance of its Antarctic mission. His team already used a fiber optic cable, thinner than a human hair, to communicate with the vehicle, unspooling meter upon meter of line as the robot vanished from the surface on test dives. Although designed to travel on its own, the science team found it extremely useful to be able to look over the shoulder of the robot, observing from afar how it made decisions in complex situations – a process Stone called supervised autonomy.
He knew that the light traveling through the cable was generated by small, very weak lasers, which led him to wonder how much laser power a fiber optic cable could carry.
‘It was just one of those things, where a series of thoughts click through your head,’ he said. ‘We sent photons down these lines, so I asked, ‘how many photons could you send down these lines?’”
The answer, he found, was a lot. And while there had been major advances in both industrial lasers and fiber optic cables as recently as the past five years, no one had ever tried to shoot the former down the latter. “The thing driving fiber optic development is telecommunications,” Stone said, “which uses very low power.”
A big industrial laser, on the other hand, can cut a car in half. These tend to be used in sealed work cells, with the beam only a couple of meters away from objects being etched for manufacturing purposes. “Safety is the overriding concern,” Stone said, “so those beams tend to travel short distances.”
And traditional lasers amplify light within a crystal. The technology presented today depends on a new class of laser that amplifies light within the fiber optic itself, Hogan says. “You couldn’t get these levels of energy into a fiber from somewhere else,” he said. “You had to generate it there.”
However well it works, no cryobot is likely to travel to Eruopa anytime soon. “We just don’t know what the surface of the moon looks like at a lander-sized scale, or whether there is a place flat enough to land,” Robert Pappalardo, a senior research scientist at JPL and head of NASA’s Europa study group, said. Pappalardo said a recent review board expressed “very serious concerns” over authorizing any lander mission to the moon until a new orbiter or fly-by mission can photograph the surface in higher resolution than currently exists.
“We have a few images at 6 meters per pixel for Europa, and that’s not enough to tell,” Pappalardo said. “The one 4-meter-per-pixel image we have of Enceladus looks like a very scary boulder field.”
Regardless of whether his technology makes it to Europa, Stone thinks it can be used in other ways in space and on Earth. Stone says the laws of physics and the test data revealed today suggest he could send “much, much more power” to larger vehicles, from much greater distances — perhaps more than 60 miles — using a high-powered laser beam that would travel down a thin cable as it unspooled from the vehicle on a special device designed to keep the line from bending or kinking.
He envisions a new generation of smaller ROVs that could work on the ocean floor, unencumbered by large (and sometimes explosive) battery packs or thick power cables dangling from ships, which can be unwieldy in strong ocean currents. He imagines a fleet of small Mars rovers tethered to a single power source, exploring in all directions from a next-generation lander.
And with a 60-mile vehicle range, a powerful 10-megawatt laser could heat water or hydrogen with enough force to drive a small rocket engine straight up, delivering up to 20 pounds of supplies to low-Earth orbit at a small fraction of the cost of existing boosters, and repeating the process every 10 minutes.
“We’re not talking about people here,” Stone said. “We’re talking about things like food, electronics, water — staple consumables for the ultimate space tourism economy.”
Images: Stone Aerospace, Austin, Texas
|Author:||Michael Ray Taylor|