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An illustration depicting what a Preliminary Research Aerodynamic Design to Land on Mars (Prandtl-m) aircraft might look like flying above the surface of Mars. (NASA/Dennis Calaba)

Preparing for first flight on Mars

With its eye on Mars, NASA Armstrong has been working on a prototype it refers to as the Preliminary Research Aerodynamic Design to Land on Mars, or Prandtl-m, which is “a flying wing aircraft with a twist.” It is planned to be ready for launch from a high-altitude balloon later this year and will be released at about at 100,000 ft. That altitude will allow it to operate in similar flight conditions as the Martian atmosphere, according to Al Bowers, NASA Armstrong Chief Scientist and Prandtl-m Program Manager.

Testing is expected to to lead to modifications that will allow the aircraft to fold and deploy from a 3U CubeSat in the aeroshell of a future Mars rover. A CubeSat is a miniature satellite used for space research that is usually about 4-in in each dimension, a 3U is three of those stacked together.

Bowers describes the aircraft as being part of the ballast that would be ejected from the aeroshell that takes the Mars rover to the planet. It would be able to deploy and fly in the Martian atmosphere and glide down and land. “The Prandtl-m could overfly some of the proposed landing sites for a future astronaut mission and send back to Earth very detailed high-resolution photographic map images that could tell scientists about the suitability of those landing sites,” he said.

Because the Prandtl-m could ride in a CubeSat as ballast aboard the aeroshell/Mars rover piggyback stack going to Mars in 2022-2024, the additional weight would not add to the mission's cost, he said. Once in the Martian atmosphere, the Prandtl-m would emerge from its host, deploy, and begin its mission.

"It would have a flight time of right around 10 minutes. The aircraft would be gliding for the last 2000 ft to the surface of Mars and have a range of about 20 miles," Bowers said.

But first, "We're going to build some vehicles and we are going to put them in very unusual attitudes and see if they will recover where other aircraft would not. Our expectation is that they will recover. As soon as we get that information, we will feel much better flying it from a high-altitude balloon," said Bowers.

"The actual aircraft's wingspan when it is deployed would measure 24 in and weigh less than a pound," Bowers said. "With Mars gravity 38% of what it is on Earth, that actually allows us up to 2.6 lb and the vehicle will still weigh only 1 lb on Mars. It will be made of composite material, either fiberglass or carbon fiber. We believe this particular design could best recover from the unusual conditions of an ejection."

The Flight Opportunities Program, which is managed at NASA Armstrong, will fund two balloon flights during the next several years and potentially a sounding rocket flight following that to demonstrate how the flier would work on Mars. The flights will be at one of two locations–Tucson, Arizona, or Tillamook, Oregon.

"We are going to use GPS initially, but obviously there is no GPS on Mars, so later on we will have to find something else for navigation," Bowers said. "But the little autopilot that provides the waypoint navigation, that's one of the things we're going to exercise on a research vehicle and then on the prototype that flies on a future balloon flight."

The flight test could also include some scientific research that will apply to a Mars mission.

"We could have one of two small science payloads on the Prandtl-m on that first balloon flight," Bowers said. "It might be the mapping camera, or one might be a small, high-altitude radiometer to measure radiation at very high altitudes of Earth's atmosphere. Eventually the aircraft may carry both of them at the same time."

A second research flight from a balloon is planned for next year and would feature an aircraft capable of returning to the launch site on a flight that could be as long as five hours as it glides back to Earth, he said.

Success could lead to a third mission that is already being discussed because the Flight Opportunities Program has access to a sounding rocket capable of going to very high altitudes, Bowers said.

"That mission could be to 450,000 ft and the release from a CubeSat at apogee," he said. "The aircraft would fall back into the Earth's atmosphere and as it approaches the 110,000- to 115,000-ft altitude range, the glider would deploy just as though it was over the surface of Mars.

"If the Prandtl-m completes a 450,000-ft drop, then I think the project stands a very good chance of being able to go to NASA Headquarters and say we would like permission to ride to Mars with one of the rovers."

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