UMD Propulsion Technology Offers New Possibilities for Satellite
Positioning, Space Exploration
Aug. 13, 2013
New electromagnetic propulsion
technology being tested by the University
of Maryland's Space Power and Propulsion Laboratory
(SPPL) on the International Space Station could revolutionize
the capabilities of satellites and future spacecraft by reducing
reliance on propellants and extending the lifecycle of
satellites through the use of a renewable power source.
Because a finite propellant payload is
often the limiting factor on the number of times a satellite can
be moved or repositioned in space, a new propulsion method that
uses a renewable, onboard electromagnetic power source and does
not rely on propellants could exponentially extend a satellite's
useful life span and provide greater scientific return on
investment.
Associate Professor of Aerospace
Engineering Ray Sedwick and his research team have been
developing technology that could enable electromagnetic
formation flight (EMFF), which uses locally generated
electromagnetic forces to position satellites or spacecraft
without relying on propellants. Their research project is titled
Resonant Inductive Near-field Generation System, or RINGS.
RINGS was sent to the International
Space Station on August 3 as part
of a payload launched on
Japan's HTV-4 Cargo Ship from the Tanegashima
Space Center. The project is scheduled for four test sessions on
the research station. Astronauts will unpack the equipment,
integrate it into the test environment and run diagnostics. From
there, RINGS will undergo three science research sessions where
data will be collected and transmitted back to the ground for
analysis.
RINGS is composed of two units, each
of which contains a specially fabricated coil of aluminum wire
that supports an oscillating current of up to 18 amps and is
housed within a protective polycarbonate shell.
Microcontrollers ensure that the currents oscillate either
in-phase or out-of-phase to produce attracting, repelling and
even shearing forces. While aluminum wire was chosen for
its low density in this research prototype, eventual systems
would employ superconducting wires to significantly increase
range and performance.
In the spring of 2013, RINGS was
tested for the first time in a microgravity environment on
NASA's reduced gravity aircraft. UMD graduate students
Allison Porter and
Dustin Alinger were on hand
to oversee the testing. RINGS achieved the first and only
successful demonstration of EMFF in full six degrees of freedom
to date.
"While reduced gravity flights can
only provide short, 15-20 second tests at a time, the cumulative
test time over the four-day campaign provided extremely valuable
data that will allow us to really get the most from the test
sessions that we'll have on the International Space Station,"
said Sedwick.
In addition to EMFF, the RINGS project
is also being used to test a second technology demonstrating
wireless power transfer (WPT). WPT may offer a means to
wirelessly transfer power between spacecraft and in turn power a
fleet of smaller vessels or satellites. Having the power to
support multiple satellites, and using EMFF as a propellant-less
means to reposition those same satellites, provides the
flexibility to perform formation control maneuvers such as
on-orbit assembly or creating synthetic aperture arrays. A
synthetic aperture array uses a network of smaller antennas to
function collectively as one large antenna. Larger antennas are
capable of producing higher resolution images and better quality
data.
The RINGS project has been a
collaborative effort between UMD SPPL and partners from the
Massachusetts Institute of Technology
(MIT) and Aurora Flight Sciences
(AFS). MIT's SPHERES (Synchronized
Position Hold Engage Re-orient Experimental Satellites) program
provided SPPL an existing test bed of miniature satellites and
control algorithms that will be used to integrate and test the
RINGS technology. AFS has provided hardware development and
support for the integration of RINGS onto the SPHERES platform.
SPPL began work on RINGS in 2011, and
the project is funded under a joint DARPA/NASA program that aims
to demonstrate and develop new technologies that could enable
future space missions by using a network of smaller spacecraft
