A brand new propulsion system may levitate automobiles in Earth’s higher ambiance

Sometimes it’s hard to remember that NASA also does atmospheric research. While the US space agency is usually considered a province of the National Oceanic and Atmospheric Administration (NOAA), it also has a vested interest in exploring our atmosphere and the technologies that enable us to do so. So the NASA Institute for Advanced Concepts (NIAC) program provided a Phase I grant to a University of Pennsylvania team to develop a novel type of propulsion that uses only light to generate data in Earth’s difficult-to-explore mesosphere to collect.

The mesosphere is the part of the atmosphere that extends between 50 km and 80 km and has several disadvantages for current exploration technologies. It is too high for balloons or regular aircraft to reach, making conventional high-altitude exploration technologies impractical. It’s also too low for satellites, as their orbit would degrade too quickly in their relatively thick soup of molecules, making the other typical space-based sensor platform impractical as well. Until now, researchers have only been able to explore it with research rockets, which traverse it for just a few minutes before falling back to earth.

Enter a new technology from Dr. Igor Bargatin, a professor of mechanical engineering at the University of Pennsylvania. The technology uses a phenomenon known as photophoretic levitation to levitate devices simply by hitting them with light.

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A lecture by Dr. Bargatin explaining the underlying photophoretic process.
Credit – GALCIT Media YouTube Channel

This propulsion technology may be similar to that of a solar sail, but the delicate foil layers of solar sails would die a horrible death in Earth’s atmosphere. The photophoretic effect, which has been known for almost a century, uses the heating of a solid compared to the surrounding gas as a buoyant force. As stated in the press release by Dr. Bargatin on the NIAC website reads: “The [photophoretic] Force creates buoyancy in structures that absorb light on the underside but remain cool on the top.”

The contribution of the laboratory of Dr. Bargatin to this centuries-old science is to make the first macro-scale demonstration of a system using this technology. Previous attempts have all been on the micron scale, as the lifting force is exceedingly weak, making it difficult to apply any significant lifting force to the payload to which it may be attached.

The design of the lab is heavily dependent on the pressure in which its plates operate, and it just so happens that the mesosphere, which pressure ranges from 1 to 100 pascals, hits right at the sweet spot where the lifting action is most effective, and enough Buoyancy generated Hold a centimeter-sized probe in the air, possibly indefinitely. Even at just a few centimeters, there are many miniaturized sensors that could be packed onto this platform to relay data previously only accessible to research rockets.

Another lecture given by Dr. Bargatin on how the technology could be useful for planetary exploration.
Credit – MarsU YouTube Channel

In fact, these micro-flyers could potentially stay aloft indefinitely if the technology were modified to use solar energy and have a day/night cycle, alternating from ascending during the day to descending during the night. dr Bargatin and his team also believe the technology could be easily modified to allow horizontal thrust, allowing the sensor platform to travel to any point in the mesosphere using only light as a propulsion source.

Like all NIAC grants, this technology is still in its very early stages and has a long way to go before a mission with a payload floats into the mesosphere. However, with the proof of concept already completed and recently published, it seems likely that this novel propulsion technology could soon get its time in the sun.

Learn more:
NASA/UPenn – Photophoretic propulsion to explore the mesosphere
Azadi et al. – Controlled levitation of nanostructured thin films for solar-powered spaceflight
Subtitles – What is the atmosphere?
UT – composition of the Earth’s atmosphere
UT – Did you know that the Earth’s atmosphere extends beyond the Moon’s orbit?

Mission Statement:|
System schematic of a photophoretic sensor system.
Credit – Igor Bargatin

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