Researchers from the University of Arizona (UArizona), US, and NASA Ames Research Centre are hopeful their design for a new lightweight, motorless sailplane will plug a gap in Martian data collection.
Laden with temperature and gas sensors and cameras for image collection, the sailplane would complement existing orbital spacecraft and land-based rovers to obtain data on Mars’s planetary boundary – the atmospheric layers between the planet’s surface and space.
“You have this really important, critical piece in this planetary boundary layer in the first few kilometres above the ground… where all the exchanges between the surface and atmosphere happen,” explains Alexandre Kling, a research scientist in NASA’s Mars Climate Modeling Center, who worked on the study.
“This is where the dust is picked up and sent into the atmosphere, where trace gases are mixed, where the modulation of large-scale winds by mountain-valley flows happen.
“We just don’t have very much data about it.”
The publication of the sailplane’s design in the journal Aerospace is the latest development in the quest for data about Mars’s planetary boundary.
It follows the landing of NASA’s tiny, two kilogram Ingenuity helicopter in Mars’s 45-kilometre wide Jezero crater last year – an event marking the debut of powered, controlled flight technology on another planet.
But reliance on solar powered motors limits Ingenuity’s flight duration to around three minutes of flight. It can fly just 12 metres above the surface. It’s because of these limitations that researchers jumped into the design of a craft that could harness the power of the Martian wind for propulsion and forgo reliance on other power sources.
“The main question is: How can you fly for free?”
The question posed by the study’s first author Adrien Bouskela, an aerospace engineering doctoral student from UArizona’s Micro Air Vehicles Laboratory, is the motivation for the sailplane’s design.
“How can you use the wind that’s there [and] the thermal dynamics that are there, to avoid using solar panels and relying on batteries that need to be recharged?”
Fortunately, Bouskela and colleagues didn’t need an out-of-this-world solution to solve the problem.
Using dynamic soaring, the sailplane utilises increases in horizontal wind speed with gaining altitude to continue flying long distances. It’s the same process albatrosses use to fly long distances without flapping their wings and expending crucial energy.
After lifting themselves up into fast, high-altitude air, albatrosses then turn their bodies to descend rapidly into regions of slower, low-altitude air. With the force of gravity providing downward acceleration, the albatross uses this momentum to slingshot itself back to higher altitudes.
Continuously repeating this process enables albatross and other seabird species to cover thousands of kilometres of ocean, flap-free.
It’s the inspiration for the sailplane’s own propulsion system, enabling it to cover the canyons and volcanoes dotted across the red planet currently inaccessible to Mars rovers.
From flying machine to weather station
While the sailplane’s primary task is for aerial data collection, its design also provides for end-of-mission or fault-triggered landing. After landing on the red surface – whether from a fault or after completing its mission – the grounded sailplane will continue recording atmospheric data for transmission to orbiting spacecraft.
In effect, the craft provides a two-in-one data collection solution.
“If we run out of flight energy, or if our inertial sensors suddenly fail for whatever reason, we expect to then keep doing science,” says Bouskela. “From the planetary science perspective, the mission continues.”
Earth testing awaits sailplane team
With a view to using the sailplane on larger Martian missions, the researchers’ focus now moves to deployment and testing.
While the design currently allows the craft to be packaged into miniature satellites no larger than a phone book, the UArizona team needs to decide whether the sailplane will unfold from the package or inflate and rigidise to full size, and if balloons or blimp drops will be involved in deployment.
The researchers are preparing to test experimental sailplanes at 15,000 feet (around 4570m) above the Earth’s surface, where atmospheric conditions are most like those the craft will encounter on Mars.