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Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California are investigating the feasibility of creating a windbot, a robotic probe designed to stay aloft in a planet's atmosphere for a long time without wings or hot-air balloons, to explore gas giants like Jupiter and Saturn.
The one-year, $100,000 study, funded by NASA's Innovative Advanced Concepts (NIAC) programme, will systematically investigate how future spacecraft of this kind could stay airborne and harvest energy.
Though no mission is currently scheduled to utilise windbots, the researchers hope their study will open new avenues for atmospheric science on gas giant planets using high-mobility robotic explorers.
Unlike the Moon and Mars, which have already been explored by robotic rovers, gas giant planets like Jupiter and Saturn have no solid surface on which a probe can land on.
In 1995, NASA's Galileo spacecraft dropped off an atmospheric probe that descended into Jupiter under a parachute. The battery-powered probe survived only about an hour before succumbing to high heat and pressure as it fell into the planet's deep atmosphere.
In contrast to the plummeting probe, a windbot could have rotors on several sides of its body that could spin independently to change direction or create lift.
Adrian Stoica, principal investigator for the windbots study at JPL, points to a great example to think about from nature: a dandelion seed.
"A dandelion seed is great at staying airborne. It rotates as it falls, creating lift, which allows it to stay afloat for a long time, carried by the wind. We'll be exploring this effect on windbot designs," Stoica said.
Stoica and colleagues think that, to stay airborne for a long time, a windbot would need to be able to use energy available in the planet's atmosphere. That energy might not be solar, because the probe could find itself on the planet's night side for an extended period.
Nuclear power sources could also be a liability for a floating probe because of their weight. But winds, temperature variations and even a planet's magnetic field could potentially be sources of energy an atmospheric probe could exploit.
The team suspects the best bet for an atmospheric robot to harvest energy is turbulence - wind that's frequently changing direction and intensity.
The key is variability. High wind velocity is not enough. But in a dynamic, turbulent environment there are gradients - differences in energy from high to low - that can be used.
The JPL team is characterising winds among the clouds of Jupiter to understand what kinds of places might be best for sending a windbot and to determine some of the technical requirements for its design.
