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A composite image of an infrared view of Saturn's moon Titan from NASA's Cassini spacecraft; renderings of several "SPARK" Aerobots being developed by Daniel Drew of the University of Hawaii. | Credit: NASA/JPL/University of Arizona/University of Idaho/Daniel Drew/University of Hawaii
Spherical "Aerobots" may one day swarm the caves of Titan — a moon of Saturn that NASA says is one of the most Earthlike in our solar system.
Titan is covered in rivers, lakes and seas of hydrocarbons, like methane and ethane, as well as a strange "karst" terrain including underground sinkholes and caves. No rover could easily traverse this surface, but flying vehicles may have more success.
So a new grant, under the early-stage NASA Innovative Advanced Concepts (NIAC) program, aims to create small, flying vehicles that could explore those caves. It's unclear if the aerobots — called SPARK, or Solid-state Propulsion for Autonomous Reconnaissance of Karst — would be ready in time for NASA's Dragonfly mission to Titan, project lead Daniel Drew, an assistant professor at the University of Hawaii at Mānoa, told Space.com.
That's because SPARK is beginning a nine-month Phase 1 grant and would need to at least get through the up-to-two-year Phase 2 before things look "more realistic" for a liftoff, he noted. Dragonfly, meanwhile, is targeted for a 2028 launch but if the mission is delayed, that provides more possibilities for late-mission additions.
"Where does that line up with the current Titan mission timeline, assuming we've missed the window for Dragonfly? I don't know," Drew said of SPARK. But whenever the mission lifts off, Drew said SPARK has a good chance of doing well on Titan with its novel ion (electric) thrusters.
Drew said his design could "provide persistence, maneuverability, robustness to the challenging near-cryogenic [icy] conditions, and minimize downwash disturbance of scientifically-important hydrocarbon layering." He hopes that SPARK, he added, could be a cave-exploration forerunner at Titan similar to the Ingenuity helicopter on Mars that made 72 flights — more than tenfold what the Red Planet demo mission was supposed to do.
Drew has been working on a particular type of ion thrusters, called electrohydrodynamic (EHD) propulsion, since he did graduate school at the University of California, Berkeley. Thanks in part to a National Science Foundation (NSF) fellowship, Drew explored several designs for flying and became interested in creating robots that flap their wings in a way similar to real-life creatures.
While exploring, he stumbled on the hobbyist "lifter" community "pretty much by chance," he said. "These [prototypes] are triangular balsa wood, magnet wire, and aluminum foil prototypes. You connect them to 40,000 volts from a flyback transformer that you rip out of a microwave or CRT monitor or whatever, and they can float above the table. There are plenty of examples of people making these on YouTube," he said.
More plumbing the archives revealed early experiments and studies at NASA and the Air Force similar to what the hobbyists were using. And by coincidence, NIAC awarded funding to another research group, led by the Massachusetts Institute of Technology, that was interested in using EHD propulsion for Earthborne aircraft. As such, Drew sensed a fruitful direction for research.
"Long story short, I ran with that idea," Drew said, "and wrote a bunch of papers where I created microfabricated centimeter-scale flying robots propelled by atmospheric ion thrusters." His accomplishments prior to the NIAC grant included what he says is the first demonstration of microfabricated EHD actuators (mechanical devices), and other firsts such as a centimeter-scale "ionocraft" taking off and subsequently, carrying a payload.
"We recently published the design and takeoff of the first ion-propelled micro-hovercraft," he added, referring to a paper on preprint server arXiv. "That may seem like a pretty decent list of significant milestones, but it's really not a crowded space of people working on this topic. I'm mostly racing against myself here."
Now with the NIAC support, Drew said he hopes to dive deeper into the benefits of EHD propulsion, such as its scalability, the fact that it's virtually silent, and its simplicity (being solid state, there are fewer parts to worry about).
A graphic depiction of the SPARK concept being developed by Daniel Drew of the University of Hawaii. | Credit: Daniel Drew/University of Hawaii
