NASA has successfully concluded a remotely controlled test of new technologies that would empower future space robots to transfer hazardous oxidizer – a type of propellant – into the tanks of satellites in space today.
Concurrently on the ground, NASA is incorporating results from this test and the Robotic Refueling Mission on the International Space Station
to prepare for an upcoming ground-based test of a full-sized robotic
servicer system that will perform tasks on a mock satellite client.
Collectively, these efforts are part of an ongoing and aggressive
technology development campaign to equip robots and humans with the
tools and capabilities needed for spacecraft maintenance and repair, the
assembly of large space telescopes, and extended human exploration.
The Satellite Servicing Capabilities Office (SSCO) at NASA's Goddard Space Flight Center in Greenbelt, Md., checked another critical milestone off their list with the completion of their Remote Robotic Oxidizer Transfer Test (RROxiTT) in February 2014.
"This is the first time that anyone has tested this type of
technology, and we've proven that it works. It's ready for the next step
to flight," says Frank Cepollina, veteran leader of the five servicing missions to the Hubble Space Telescope and the associate director of SSCO.
"RROxiTT gives NASA, and the satellite community at large, confidence
that advanced satellite refueling and maintenance technologies aren't a
wild dream of the future," says Cepollina. "They're being built and
tested today – and the capabilities that they can unlock can become a
reality."
Since 2009, SSCO has been investigating human and robotic satellite
servicing while developing the technologies necessary to bring on-orbit
spacecraft inspection, repair, refueling, component replacement and
assembly capabilities to space.
Taking lessons learned from the successful Robotic Refueling Mission,
the SSCO team devised the ground-based RROxiTT to test how robots can
transfer hazardous oxidizer, at flight-like pressures and flow rates,
through the propellant valve and into the mock tank of a satellite.
While this capability could be applied to spacecraft in multiple
orbits, SSCO focused RROxiTT specifically on technologies that could
help satellites traveling the busy space highway of geosynchronous Earth orbit, or GEO.
Located about 22,000 miles above Earth, this orbital path is home to
more than 400 satellites, many of which beam communications, television
and weather data to customers worldwide.
By developing robotic capabilities to repair and refuel GEO
satellites, NASA hopes to add precious years of functional life to
satellites and expand options for operators who face unexpected
emergencies, tougher economic demands and aging fleets. NASA also hopes
that these new technologies will help boost the commercial
satellite-servicing industry that is rapidly gaining momentum.
Besides aiding the GEO satellite community, a capability to fix and
relocate "ailing" satellites also could help mitigate the growing
orbital debris problem that threatens continued space operations,
ultimately making space greener and more sustainable.
Goddard and Kennedy Collaborate on New Technologies
RROxiTT tested a suite of new robotic technologies and procedures
developed by the SSCO team at two collaborating centers, Goddard and Kennedy Space Center, Fla.
Technologies included a flexible propellant hose, a new Oxidizer Nozzle Tool, and a unique propellant transfer system (PTS)
all developed by the multi-Center SSCO team. The PTS, consisting of
oxidizer tanks, seal-less pumps, flow-metering devices, and a maze of
tubing, contains the components a servicer satellite would need to
replenish the propellant of orbiting spacecraft for many years of
extended life.
During operations, a robot operator at NASA Goddard in Maryland
commanded an industrial robot at Kennedy in Florida -- more than 800
miles away -- to mate to a satellite valve and transfer propellant into a
mock tank. At the conclusion of nine days of RROxiTT operations, the
SSCO team declared victory.
"It's one thing to build a set of technologies and discover that they work," says Benjamin Reed,
deputy project manager of SSCO at Goddard. "It's another thing to
consider the capabilities that they could unlock. The paradigm of
one-and-done should be relegated to the 20th century – the future of
space will be re-use, re-purpose and replenish."
Applications to Help People Stay Safer on Earth
While RROxiTT technologies are being designed for use in space, they
may one day be applied to robotically replenish satellites before they
launch.
Oxidizer
– namely nitrogen tetroxide – is a chemical that, when mixed with
satellite fuel, causes instant combustion that provides thrust (motion)
for a satellite. The liquid is contained within a satellite tank at
intense pressures, up to 300 pounds per square inch (about 20 times
atmospheric pressure). Toxic, extremely corrosive and compressed, it
requires special handling.
Using these new RROxiTT technologies to robotically fill up
satellites on the ground would keep humans at a safe distance during
these extremely hazardous operations.
Future Satellite Servicing Demonstrations
Since wrapping up RROxiTT, SSCO is broadening its portfolio to
include xenon transfer technologies -- propellant used by satellites
with electric propulsion systems.
The team is also gearing up for the next phase of the Robotic Refueling Mission on the International Space Station. The next Automated Transfer Vehicle,
currently scheduled to launch to the space station in June of this
year, will deliver new RRM hardware for a fresh set of activities.
Upcoming demonstrations include spacecraft inspection, the
replenishment of cryogens in satellites not originally designed for
in-flight service, and advanced solar cell technology. A separate space
station demonstration currently in development will focus on real-time relative navigation.
On the ground, SSCO will be conducting a separate test at Goddard in
later this year. Drawing from lessons learned from RRM, RROxiTT, and
their efforts in robot algorithms and development, the team will command
a full-sized robot servicer system to perform a series of servicing
tasks on a suspended satellite mockup. Results will help the team
evaluate how the numerous servicer subsystems and technologies work
together as an integrated system to accomplish servicing objectives.
The event will test both proven and newly developed technologies.
"Sustainable space development is not only good stewardship of the
shared resource of outer space," says Reed, "but it also makes sense as
we develop the skill set to embark humans deeper into our solar system."
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