Tech Briefs Magazine - May 2021 - 37

interfere with the thrust produced by
the engines.
In the new hybrid-electric, or turboelectric design, a plane's source of
power would still be a conventional gas
turbine but it would be integrated within
the plane's cargo hold. Rather than directly powering propellers or fans, the
gas turbine would drive a generator, also
in the hold, to produce electricity, which
would then electrically power the airplane's wing-mounted, electrically driven propellers or fans. The emissions produced by the gas turbine would be fed
into an emissions control system, broadly similar to those in diesel vehicles, that
would clean the exhaust before ejecting
it into the atmosphere.
Before airplane electrification had
been seriously considered, it might
have been possible to implement a con-

cept such as this as an add-on to the
back of jet engines. But this design
would kill any stream of thrust that a jet
engine would produce, effectively
grounding the design. The new concept gets around this limitation by separating the thrust-producing propellers
or fans from the power-generating gas
turbine. The propellers or fans would
instead be directly powered by an electric generator, which in turn would be
powered by the gas turbine. The exhaust from the gas turbine would be fed
into an emissions control system, which
could be folded up, accordion-style, in
the plane's cargo hold - completely
isolated from the thrust-producing propellers.
The bulk of the hybrid-electric system
- gas turbine, electric generator, and
emissions control system - would fit

within the belly of a plane, where there
can be ample space in many commercial
aircraft. If such a hybrid-electric system
were implemented on a Boeing 737 or
Airbus A320-like aircraft, the extra
weight would require about 0.6 percent
more fuel to fly the plane. This would be
many times more feasible than what has
been proposed for all-electric aircraft.
The researchers also calculated the
emissions that would be produced by a
large aircraft, with and without an emissions control system, and found that the
hybrid-electric design would eliminate
95 percent of NOx emissions.
The team is now working on designs
for a zero-impact airplane that flies without emitting NOx and other chemicals
like climate-altering carbon dioxide.
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-253-2709.

Hybrid Propellant Formulation Uses Graphene Foams
This method increases burn rate of solid propellants.
Purdue University, West Lafayette, Indiana

raphene - a material with applications in biomedical technology, electronics, composites, energy, and sensors
- is being used to increase the burn rate
of solid propellants used to fuel rockets
and spacecraft.
Methods were developed for making
and using compositions with solid fuel
loaded on highly conductive, highly
porous graphene foams for enhanced
burn rates for the loaded solid fuel. Researchers maximized the catalytic effect
of metal oxide additives commonly
used in solid propellant to enhance
decomposition. The graphene foam
structures are also thermally stable,
even at high temperatures, and can be
reused. The developed compositions
provide significantly improved burn
rate and reusability.
The graphene foam works well for
solid propellants because it is superlightweight and highly porous, which
means it has many holes in which scientists can pour fuel to help ignite a rocket
launch. The graphene foam has a 3D,
interconnected structure to allow a
more efficient thermal transport pathway for heat to quickly spread and ignite
the propellant.
The technology provides higher performance that is especially important in
areas such as hypersonics. Tests demon-

61 μm
45°

56 μm
5°

b) High

PC-Std.

65 μm
4°

200 μm
10 kV

A new propellant formulation method uses porous graphene foams to power spacecraft. (Purdue)

strated a burn rate enhancement of nine
times the normal using functionalized
graphene foam structures.
The graphene foam technology has
applications for energy conversion
devices and missile defense systems,

Tech Briefs, May 2021

www.techbriefs.com

Cov

ToC

along with other areas where tailoring
nanomaterials for specific outcomes
may be useful.
For more information, contact the Purdue
Office of Technology Commercialization at
OTCIP@prf.org; 765-588-3475.
37

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Tech Briefs Magazine - May 2021

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