The Mars helicopter is cool — a fleet of small, levitating nanocardboard aircraft would be cooler

• Exploring Mars in the future could be done using tiny, levitiating ‘nanocardboard’ aircraft — each of which weighs less than a fruit fly.
  
• These aircraft will be able to offer lower risk and higher rewards in comparison to the Mars helicopter set to make its way to the Red Planet later this year.
  
• “The Mars Helicopter is very exciting, but it’s still a single, complicated machine. If anything goes wrong, your experiment is over,” said lead author of the study.
  

NASA has plans to launch Perseverance this summer with a “high risk, high reward” helicopter on board to explore the Red Planet. Before the project’s had a chance to get off the ground — quite literally — researchers at Penn University have a more ambitious plan to use a levitating fleet of ‘nanocardboard’ aircraft to cruise above Mars.

Each plane would weigh less than a fruit fly and explore the skies of planet unencumbered. The solution will not be more effective in monitoring Mars’ dusty landscape but it will also present less risk, according to the researchers.

“The Mars Helicopter is very exciting, but it’s still a single, complicated machine. If anything goes wrong, your experiment is over, since there’s no way of fixing it. We’re proposing an entirely different approach that doesn’t put all of your eggs in one basket,” said lead author of the paper published in Advanced Materials, Igor Bargatin.

How does one make a flat piece of nanocardboard fly?
The aircraft is essentially a hollow plate of aluminium oxide walls that are only a few nanometers thick creating corrugation, which is a regular pattern of ridges and grooves that spread across the plate.


It makes the aircraft more flexible and prevents cracking in harsh environments. More importantly, the corrugation is also what gives the aircraft the ability to levitate. The temperature differentials create an air current which then flows through the hollow structure.

“The air current through these micro-channels is caused by a classical phenomenon called ‘thermal creep,’ which is a rarefied gas flow due to the temperature gradient along the channel wall,” said co-author Howard Hu.

It does all of it, and more, but simply relying on the power of light.

What else can the flying nanocardboard do?
Each of the nanocardboard flyers weighs around a third of a milligram. It would take a million of them to equal the same mass as the Mars Helicopter and more than six billion to measure up the ground-based rover that will deploy the chopper.

Even though the study claims that the risk of exploring Mars is decreased considerably with the new solution, the size of the aircraft limits the scope of how much it can do. It would primarily only come equipped with sensors and its payloads wouldn’t be able to exceed a few milligrams. However, according to Bargatin, the aircraft doesn’t need anything more.

“In addition to carrying sensors our flyers could simply land and have grains of dust or sand passively stick to them, then transport them back to the rover so it doesn’t need to travel as far,” he said.

He adds that it won’t need moving parts because it could simply be piloted by the rover. A pinpoint laster would be enough to guide it through the air since the direction since the flight of the nanocardboard aircraft depend on which parts of the plate are heated — which in turn determine airflow. It will also be able to fly higher than the current chopper.

“The Earth’s mesosphere is pretty similar to the Martian atmosphere in terms of density, and we currently don’t have anything that flies there, since it is too low for space satellites but too high for airplanes and balloons,” said Bargatin.

As the next step, he is in the process of collaborating with other researchers on how to miniaturize chemical sensors that could detect water or methane — key signatures of life on Mars.

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