How soon are we going to fly airplanes on Mars?
The Ingenuity helicopter was a success. It has conducted several flights on Mars since its deployment with the Perseverance rover in February 2021, and has fulfilled its main mission: to show that flying in the thin, dusty atmosphere of the Red planet is actually possible.
The next logical step would be to send a heavier, more efficient aircraft that could carry more sensors and survey the planet's surface faster. But is that possible? Could we fly an airplane on Mars?
The answer is simple: yes, and such a project has been proposed numerous times since the 1950s. Although the Martian atmosphere is just 1% as dense as Earth’s, the planet’s gravity is almost three times weaker, which partially offsets the disadvantages.
The Martian atmosphere also consists almost entirely of carbon dioxide, which cannot combust. So, jet engines are not an option. But propellers and rockets work just fine. Wing area on the Martian airplane would have to be significantly bigger than it is common on earth, but in principle, there is nothing that would prohibit a heavier-than-air flight, be it powered or unpowered.
Famously, the very first idea for the Mars mission, drafted by German-American engineer Wernher von Braun (the father of both Nazi V-2 rocket and the Apollo program), proposed to use huge gliders as landers. Back then the density of the planet's atmosphere was unknown, so the proposal was not very realistic.
Nevertheless, through the 60s and 70s NASA has been seriously considering gliding landers for its first missions to MARS, but those never came to be: there were simply way too many unknowns, and conventional landers were deemed more practical.
One project went farther than that though. In the late 70s, when the density of the planet's atmosphere was well known, a project to study it further with a propeller-driven airplane was being developed. NASA would use a modified version of a proven Mini-Sniffer drone for that. The aircraft could run without oxygen and was designed for high-altitude flight, in conditions that are somewhat similar to Martian ones. Various tests were done, but eventually the idea was dropped.
The rebirth of the idea
It resurfaced again several decades later. Since the 90s, dozens of various Mars mission proposals were planned by NASA and other space agencies, many of them involving either gliders or powered airplanes.
Their advantages over regular landers or rovers are numerous: an aerial platform would be able to study the planet's atmosphere at various altitudes, as well as cover large areas, surveying and photographing the surface in much greater detail than any satellite.
Such was the purpose of a dozen of proposals, and some of those – for example, the Prandtl-M and the Sky-Sailor – even reached a prototype stage.
None of them went beyond that though. There were many reasons for that, the major of them being limitations to the Martian budget. Airplanes, and especially gliders, would have an extremely short lifespan in comparison with, say, rovers – but cost almost as much or even more to develop and deploy.
Unless there was a way to refuel or recharge such aircraft, the idea is simply not efficient enough. Sky-Sailor tried to solve that by using solar batteries in its wings, but their effectiveness would have been small, as Mars is much further from the Sun than Earth.
Charging such an aircraft by docking it with a lander or a rover would be a bit simpler. That was one of the initial ideas for the Mars 2020 project – the one that resulted in the Perseverance and the Ingenuity.
One of its early variants involved a small vertical take-off and landing (VTOL) drone. Developed by Langley Research Center and called the Mars Flyer, the two-kilogram aircraft was intended to take off vertically, but transition into horizontal flight for covering large distances, meaning that it would be a helicopter and an airplane in one. It would not have its own solar panels though, and charge by docking with the rover.
That would limit its flight distance and make the aircraft less reliable overall. In the end, Ingenuity helicopter – a simpler and more robust project – was selected in its place, but the Mars Flyer still remains as a possibility for future missions.
The Martian airplane
But the concept that received the most development and the most attention is, undoubtedly, the Aerial Regional-scale Environmental Survey (ARES). Conceived in the early 2000s it was intended to be launched in early 2010s, but fell victim to some of the largest budget cuts in NASA’s history.
A rocket plane with a wingspan of 6.25 meters (20.5 feet) it would have featured extendable wings and be deployed straight out of the orbit, with a parachute. As well as studying the atmosphere, it would have conducted precise measurements of the Martian magnetic field and fly for about an hour before running out of propellant and crashing into the surface.
As the design phase was not yet finished, a possibility to use propeller propulsion instead of a rocket engine was considered too, but it would have been more difficult to implement. The stall speed of any Martian airplane would be extremely high, and even a vehicle with large wing surface and low drag would have to fly very, very fast.
The team behind ARES seemed to have solved the Martian aerodynamics though, but that did not help them to push the project through the selection process.
So, it remains shelved to this day. Is there still a possibility that ARES would fly? That is doubtful. Nevertheless, NASA’s next major Mars mission is still not planned.
It is highly likely that it will feature some form of reconnaissance drone to accompany a rover, maybe a pure helicopter like Ingenuity, or maybe a more efficient one similar to the already almost developed Flier. If NASA selects the latter, there might be a small semi-airplane flying on Mars in two to four years.
A bigger ARES-like airplane would have to travel to Mars separately and be a part of a separate mission. The possibility of conducting such a mission depends both on NASA’s budget and the perceived need to study the planet from the air.
But with an interest in the Red planet increasing, such possibility seems bigger and bigger. No date is set in stone yet, but we already have the technology, and a story of success in the form of Ingenuity. The next step seems to be only a matter of time.
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