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AFIT Student Research Floats on a Vacuum
Posted: 07/22/2013 by AFIT Public Affairs

By Bill Hancock, 88th Air Base wing, Public Affairs

WRIGHT-PATTERSON AIR FORCE BASE, Ohio – Envision a one ton block of solid iron. If you place that block of iron into water it will sink. Iron is approximately eight times denser than water.  Submerged the block displaces only 1/8 ton of water. This displaced weight of water is not enough to make it float. Now reshape that iron into a boat hull. It still weighs one ton, but, because it is has greater volume, it displaces more than a ton of water and floats. The Greek scientist, Archimedes, stated that, “the buoyant force on a submerged object is equal to the weight of the fluid displaced by the object.”

At the Air Force Institute of Technology, recent graduate Captain Trent Metlen (USMC) has been researching structures that float in air using a vacuum.  “My structure is kind of like a submarine” said Metlen “A submarine is made to be in compression in the water. My structure is made to be in compression in the air. It will displace more weight of air than the structure weighs”. This is the principle behind achieving positive buoyancy and making a vacuum chamber float.

The quandary Metlen faced was coming up with a vacuum chamber that is very light, very stiff and very strong. “Today’s vacuum chambers are big, massive, metal chambers. They look like armored tanks” said Metlen “It takes a lot of stability and strength to create a vacuum chamber.” Metlen came up with several designs he showed analytically to be capable of the stability and strength needed to withstand one atmosphere of pressure while being light enough to float in air at sea level. He favored a geodesic sphere called an icosahedron, made of 20 equilateral triangular faces, because of its simplicity.

Metlen analytically showed that using modern optimization techniques and modern materials with high specific stiffness and strength, a lighter than air structure can be constructed that is strong enough to withstand one atmosphere of pressure and light enough to achieve positive buoyancy. Like the one ton iron boat in water, Metlen’s lightweight sphere will float in air and do so without the need of lifting gases like helium. As long as the pressure within the structure remains at a near perfect vacuum the structure could stay airborne indefinitely.

A potential use for this lighter than air structure would be as a sensor platform to be used for remote observation of hazardous environments inaccessible to ground vehicles.

“Metlen’s research into lighter than air structures has provided ground breaking capability for future study. This research could be considered on the level of a PhD dissertation” said Metlen’s research advisor and AFIT Aeronautical Engineering instructor, Dr. Anthony Palazotto. “We see much promise here. After Capt Metlen’s graduation and departure from AFIT, we anticipate continuing on with his research and having new students take up the mantle”.

When Capt Metlen first arrived at AFIT he quickly established a working relationship with Dr. Palazotto. He had ideas for his course of study and research. Both student and teacher recognized their shared interest in lighter than air structures. “It is this sort of teacher - student interaction that makes AFIT exceptional” states Dr. Todd Stewart, AFIT Chancellor, “Since 1919 this institute has been providing, high-quality graduate education programs and engaging in this type of ground breaking innovation and research that keeps our Air Force the best in the world”.

The AFIT mission is to advance air, space, and cyberspace power for our armed forces, the Nation, and its partners by providing relevant defense-focused technical graduate and continuing education, research, and consultation.  AFIT accomplishes this mission through three resident schools: the Graduate School of Engineering and Management, the School of Systems and Logistics, and the Civil Engineer and Services School. AFIT also manages all Air Force health, line, legal, and chaplain graduate education at civilian institutions.

Dr. Bradley Liebst, Head of AFIT's Department of Aeronautics and
Astronautics presented the Leading Edge Award sponsored by Aerovar Research
to Capt Trent Metlen, USMC, during AFIT's June 2013 Commencement Ceremony.
This was the inaugural year for the award, established to honor a student
whose research developed a breakthrough concept that can enhance the
aerospace industry.


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