The upper and lower atmospheres are crowded. Below 40,000 feet, commercial airplanes zig-zag across the sky while weather balloons, gliders, and planes for data collection and defense capabilities hit the ceiling at the altitude they can reach. Much higher, more than 7,000 satellites orbit the planet in focused circles. But right in the middle of all that, there’s a band of the atmosphere that’s inaccessible.

That region is the focus of a newly launched aerospace startup out of the John A. Paulson School of Engineering and Applied Sciences (SEAS). Rarefied Technologies plans to propel small devices into near space to gather novel climate data and create a constellation of networked devices for telecommunications. The company launched this fall after receiving support from the Harvard Grid Accelerator to advance the research. Harvard’s Office of Technology Development (OTD) protected the intellectual property of the technology and licensed it to Rarefied Technologies for further advancement.  

Rarefied’s purview is the mesosphere, the strip of atmosphere between 50 and 100 kilometers above Earth, where there’s not enough lift for airplanes to cruise, but it’s too low for satellites to orbit.

“Some people call it ‘the ignorosphere,’ kind of glibly, just because there's really nothing that can fly in this region. It's too high for planes, and it’s too low for satellites,” says co-founder Benjamin Schafer, who recently completed his PhD in Applied Physics at Harvard. “Rarefied is building devices that can fly in part of the atmosphere that nothing else can reach.”

The devices work only in low atmospheric pressure environments — the pressure in the mesosphere is 5 million times lower than at sea level — and among rarefied gas. Once out of the lab and launched into space, Rarefied’s devices would be the first to collect data directly from this region. The climate data they gather could help model weather events, incoming natural disasters like hurricanes, and help improve flight paths. That previously uncollectable information could be valuable to industries like insurance and agriculture. Defense and telecommunications may also benefit by using the devices in a networked communications system.

Moving from that theoretical idea to a fully-fledged commercial operation involved significant advancements in the research while at SEAS. The research team was named one of the Harvard Grid Accelerator awardees earlier this year. The Grid Accelerator is specifically designed to bridge the funding gap that haunts many startups; as companies move from research to commercialization, there’s often a gulf between early innovation funding — sources like academic funding and government grants — and financing focused on industry from a venture capital firm or a bank.

Chris Petty, OTD’s director of business development for physical sciences, worked with the team on their submission to the Grid Accelerator and continued collaborating with them on commercialization opportunities and conversations with potential funders. The accelerator invested in Rarefied, Petty says, because of its strong ability to articulate a market need and commercial potential.

“Every once in a while at work, you sort of feel like you're walking through a science fiction novel. And this is one of those,” says Petty. But Schafer and the team also “do a really good job of tying that capability back to very practical applications.”

One category of geoengineering involves increasing the reflectance of the atmosphere to deflect rays of sunlight and cool the earth. Early in his PhD, Schafer and other Harvard researchers, including David Keith, explored photopheresis, a mechanism discovered in the late 1800s that allows aerosols to levitate in the upper atmosphere. When applied to climate change, researchers at Harvard hypothesized that engineered aerosols could be launched above the stratosphere, where they could remain for long periods to reflect sunlight.  

Soon, Schafer and his colleagues began wondering: Would it be possible to float something bigger in space? That question—and the mechanism for lofting larger devices—became the core of Schafer’s research. Though photopheresis is over a century old, engineering the devices themselves only became possible with very recent developments in nanotechnology.

Much of Schafer’s PhD focused on modeling the lofting mechanism that allows such devices to fly in the mesosphere. Eventually, the team built an experimental vacuum chamber at Harvard to simulate the upper atmosphere. At reduced pressures similar to those in the mesosphere, it takes less than one sun’s worth of light to move these devices around.

Schafer and his co-founder Angela Feldhaus, a Harvard PhD candidate in Applied Mathematics, worked with OTD to protect their innovations and are now commercializing that research as part of Rarefied. The startup is also continuing its work at Harvard, fabricating the devices at the Center for Nanoscale Systems. Schafer and Feldhaus were named Breakthrough Energy Fellows this year, receiving funding and hands-on support to advance Rarefied’s capabilities in climate technology innovation. Schafer, named a 2025 Forbes 30 Under 30, is also part of the New Mexico Lab-Embedded Entrepreneur Program at Los Alamos National Laboratory. Feldhaus is a Chain Reaction Innovations fellow at Argonne National Laboratory.

The startup hopes to advance to field tests in the next couple of years after continuing to improve flight characteristics as its devices levitate in the upper atmosphere. The company is also interested in eventually making larger structures that could host more weight. Such innovations won’t only be beneficial for Rarefied’s focus industries, Schafer says, it will provide important research for scientists in a “pretty unexplored field.”

“Not only are the structures we're making very novel, but the data they collect could be novel in an academic sense as well,” says Schafer. “One of the great parts about this project is that there's commercial use, but we're also kind of pushing the forefront of science on what these structures are capable of doing.”