Motorless sailplane design could take flight on Mars

Inspired by the flight of the albatross, a team of researchers and space experts have designed the sailplane that could fly on Mars. The team aims to use the sailplane to analyse the Red Planet’s atmosphere and geology.

"You have this really important, critical piece in this planetary boundary layer, like in the first few kilometres above the ground," said Alexandre Kling, a research scientist in Nasa's Mars Climate Modeling Centre.

"This is where all the exchanges between the surface and atmosphere happen. This is where the dust is picked up and sent into the atmosphere, where trace gases are mixed, and where the modulation of large-scale winds by mountain-valley flows happens. And we just don't have very much data about it."

At the moment, there are eight active spacecraft orbiting Mars, gathering imagery of the planet's surface at a resolution of about one foot per pixel. Meanwhile, three rovers traverse the ground, mapping small areas of the planet with greater precision. However, there is a part of the planet’s atmosphere and surface that cannot be analysed by either device and which is of high interest to scientists, as it includes atmospheric climate processes and geological features such as volcanoes and canyons.

In order to address this data gap, Kling partnered with a group of Arizona scientists to design a sailplane that could observe the space that cannot be covered by either surface rovers or orbiting spacecraft.

The final design, described in a paper published in the journal Aerospace, shows a sailplane equipped with flight, temperature and gas sensors, as well as cameras. The sailplanes would weigh only an estimated 11 pounds each. According to the research team, the plane would use wind energy to fly for hours or even days.

The team’s sailplane is not the first invention that hopes to fly in Mars' thin atmosphere. In 2021, Nasa landed a four-pound helicopter on the Red Planet named Ingenuity, which is considered the first device to test powered, controlled flight on another planet.

However, Ingenuity is a solar-powered vehicle that can only fly for around three minutes at a time, reaching maximum heights of just 12m (about 39 feet), which would not be enough to conduct the type of research Kling envisions.

"These other technologies have all been very limited by energy," said Adrien Bouskela, the paper's first author.

"What we're proposing is just using the energy in situ. It's kind of a leap forward in those methods of extending missions. Because the main question is: how can you fly for free? How can you use the wind that's there, the thermal dynamics that are there, to avoid using solar panels and relying on batteries that need to be recharged?"

Instead of helicopters, the Arizona team turned to lightweight, low-cost, wind-powered sailplanes for a solution.

The planes will use several different flight methods, including simple static soaring when sufficient vertical winds are present. They can also use a technique called dynamic soaring, which - like an albatross on a long journey - takes advantage of how horizontal wind speed often increases with altitude, a phenomenon particularly common on Mars.

Using this nimble manoeuvring, the sailplanes can continually harvest energy from the atmosphere, flying for hours or even days at a time.

"It's almost something you have to see to believe," said paper co-author Jekan Thanga.

Due to its small weight of 11 pounds (5kg) and size (3.4m), the model could be packed into a small satellite, delivered to Mars as part of a larger mission and then unfold like origami or inflate to its final size. The researchers are also considering delivery into the atmosphere by way of a balloon or blimp that could act as a docking station for the plane. The sailplanes could even potentially redock on the balloon or blimp after a flight and go on to complete multiple missions.

After landing on the Martian surface, the planes would continue to relay information about the atmosphere back to the spacecraft, essentially becoming weather stations. In this way, each Mars sailplane that was retired would become another node in a network of weather stations similar to the one that exists on Earth.

"If we run out of flight energy, or if our inertial sensors suddenly fail for whatever reason, we expect to then keep doing science," Bouskela said. "From the planetary science perspective, the mission continues."

This summer, the team is set to test experimental planes at about 15,000 feet above sea level, where Earth's atmosphere is thinner and flight conditions are more akin to those on Mars. Ultimately, the researchers aim to secure a seat in a future Mars mission for its albatross-like sailplanes.