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A
new research program at Rensselaer Polytechnic Institute seeks to define the
next generation of low-orbit satellites that are more maneuverable, cheaper to
launch, easier to hide, and longer lived. Additionally, this research holds the
promise of guiding dead satellites and other space debris more safely to the
Earth’s surface.
Led
by Rensselaer faculty member Riccardo
Bevilacqua, the research team is challenged with developing new theories for
exploiting the forces of atmospheric drag to maneuver satellites in low-Earth
orbits. Atmospheric drag is present up to 500 km of altitude. Using this drag
to alter the trajectory of a satellite alleviates the need to burn propellant
to perform such action. Decreasing the amount of required propellant will make
satellites weigh less, which reduces the overall cost of launching satellites
into orbit.
Additionally,
this new research holds the promise of using drag to control and maneuver dead
satellites that are inoperable or have run out of propellant.
This
project, titled “Propellant-free Spacecraft Relative Maneuvering via
Atmospheric Differential Drag,” is funded by the Air Force Office of Scientific
Research (AFOSR) Young Investigator Research Program with an expected
three-year, $334,000 grant.
“Using
differential drag to maneuver multi-spacecraft systems in low-Earth orbit is a
new, non-chemical way to potentially reduce or even eliminate the need for
propellant,” said Bevilacqua, assistant professor in the Department of
Mechanical, Aerospace, and Nuclear Engineering (MANE) at Rensselaer. “Reducing the satellite’s overall mass at launch, by carrying less propellant,
allows for easier, cheaper, and faster access to space. In addition, the
ability to maneuver without expulsion of gases enables spacecraft missions that
are harder to detect.”
Satellites
experience drag while in low-Earth orbits, and this drag causes their orbits to
decay—sending the satellites closer and closer to Earth. Bevilacqua wants to
take advantage of this drag by attaching large retractable panels to
satellites. When deployed, these panels would work like a parachute and create
more drag in order to slow down or maneuver the satellite.
This
type of system could be built into new satellites, or even designed as a
separate device that could be attached to existing satellites already in orbit.
The drag panel system would use electrical power—which can be recharged via
solar panels—to perform its maneuvers. The system would not require any fuel or
propellant. Bevilacqua said such a device could be attached to a dead satellite
already in freefall, in order to help control where the satellite will land on
the Earth’s surface.
This new project is a key component of
Bevilacqua’s overall research portfolio, which focuses on the guidance,
navigation, and control of multiple spacecraft. The overall trend in spacecraft
design is to go smaller and smaller, he said. Today’s satellites are generally
one big unit. In the future, satellite systems likely will be made up of many
smaller satellites that join together and form one larger device. This type of
modular system allows for individual components to be replaced or upgraded
while the overall system remains functional in orbit. One of the major
challenges to realizing this vision is developing a propellant-free means to
maneuver small satellites so they’re able to rendezvous and join with one
another. Differential drag could be one such way to accomplish this, Bevilacqua
said.