NASA Remote Robotic Oxidizer Transfer Test (RROxiTT) robot refuelling satellites

The Remote Robotic Oxidizer Transfer Test (RROxiTT) robot demonstrated a way for future servicing satellites to transfer oxidizer to a satellite in need of refueling, at the Kennedy Space Center's Payload Hazardous Servicing Facility.

Credit: NASA

NASA wants to create a robotic gas station in space.

While that might call to mind visions of interstellar starships, the unmanned depot won't actually be used to refuel rockets leading to the outer solar system or other worlds. Instead, it will service satellites orbiting Earth.

Thousands of satellites currently circle the Earth, transmitting everything from GPS navigation signals to weather forecasts to television shows, and all of them need fuel to maneuver in orbit.

Without a way to refuel these aging machines, many satellites that could otherwise provide many more years of service break down and are retired.


NASA's Satellite Servicing Capabilities Office (SSCO) at Goddard Space Flight Center in Maryland teamed with the Kennedy Space Center (in Florida) in 2011 to concoct a way to refuel satellites as they zip around the planet. Under their solution, this refueling will be carried out by robotics.

By creating this new technology, "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's Bob Granat wrote in a statement.

This robotic technology is not limited to fueling, though. NASA can also use it to fix malfunctioning satellites and build entirely new structures in outer space.

The partnership between Goddard and Kennedy has been fruitful thanks to each organization's special capabilities.

Kennedy's long history of preparing spacecraft for launch, for instance, meant that it had a lot of experience with loading propellant.

In addition, because of Kennedy's involvement, "project participants were able to use existing equipment, facilities and excess Space Shuttle Program hardware, saving millions of dollars in development costs," NASA said.

Goddard, meanwhile, focused on the robotics. In fact, they recently shipped a robotic arm to Kennedy, 800 miles (1,287 kilometers) away, to test the system's remote-control capability.

During the test, the remote robot operator, located at Goddard, connected the end of the robot arm to a valve on the side of a simulated satellite, which was located at Kennedy.

The Kennedy team then made sure that the nitrogen tetroxide, a substance commonly used in spacecraft, flowed smoothly through the valve.

One beneficial side effect of refueling satellites in orbit is that it lessens the amount of dangerous space junk in the area just above Earth's atmosphere.

Instead of having dead satellites floating around uncontrolled, engineers on the ground can extend their lives with refueling, putting off costly launches and slowing the rate of material sent into space.

At the geosynchronous orbit level, a region 22,236 miles (35,786 km) above Earth, there are more than 100 government-owned spacecraft and 360 "commercial communication satellites."

Therefore, "the capability to refuel and repair satellites at this orbit could make GEO [Geosynchronous Earth orbit] more sustainable and help mitigate orbital debris problems," officials with NASA's Satellite Servicing Capabilities Office wrote on their website.

NASA RROxiTT: Testing new technologies for robotic refueling - Video

In space, a robot servicer could use propellant transfer technologies to extend the life of orbiting satellites (depicted, artist’s concept). 

Credit: NASA 

It's corrosive, it's hazardous, and it can cause an explosion powerful enough to thrust a satellite forward in space.

Multiple NASA centers are currently conducting a remotely controlled test of new technologies that would empower future space robots to transfer this dangerous fluid—satellite oxidizer—into the propellant tanks of spacecraft in space today.

Building on the success of the International Space Station's landmark Robotic Refueling Mission (RRM) demonstration, the ground-based Remote Robotic Oxidizer Transfer Test (RROxiTT) is taking another step forward in NASA's ongoing campaign to develop satellite-servicing capabilities for space architectures and human exploration.

August 2013 - In its second phase, RRM is now moving on to demonstrate how a space robot can complete intermediate tasks required to replenish croygen in the instruments of "legacy" satellites: existing, orbiting spacecraft that were not designed to be serviced. 

Initial activities to demonstrate this on-orbit capability were completed in March and June 2012 with the aid of the original RRM tools and activity boards.

Credit: NASA

On Earth, RROxiTT technologies could one day be applied to robotically replenish satellites before they launch, keeping humans at a safe distance during an extremely hazardous operation.

In space, a robot servicer could use propellant transfer technologies to extend the life of orbiting satellites (depicted, artist's concept).

Building on the Past to Set the Stage for the Future
In January 2013, RRM demonstrated that remotely controlled robots—using current-day technology—could work through the caps and wires on a satellite fuel valve and transfer fluid into existent, orbiting spacecraft that were not designed to be serviced.

To meet the safety requirements of space station, ethanol was used as a stand-in for satellite fuel.

For the team that conceived and built RRM, the Satellite Servicing Capabilities Office (SSCO) at NASA's Goddard Space Flight Center in Greenbelt, Md., the successful conclusion of this refueling demonstration was not the end of their work, only the beginning.

Benjamin Reed

"We were immensely pleased with RRM results. But doing more was always part of the plan," says Benjamin Reed, deputy project manager of SSCO.

"There were certain aspects of satellite refueling that couldn't be demonstrated safely while we were using space station as a test bed – aspects that we chose to defer to a later test date."

"RROxiTT is the next step in that technology development."


In this video, robotic arm operator Alex Janas introduces RROxiTT (Remote Robotic Oxidizer Transfer Test) while standing next to the robotic arm. 

Credit: NASA/GSFC/Scientific Visualization Studio

Taking lessons learned from RRM, the SSCO team devised the ground-based RROxiTT to test how robots can transfer oxidizer, at flight-like pressures and flow rates, through the propellant valve and into the mock tank of a satellite that was not designed to be serviced in space.

"No one has ever attempted this type of oxidizer transfer before," says Marion Riley, the SSCO test manager for RROxiTT.

"Like any NASA-sized challenge, we had to figure out—and at times, create—the right set of technologies and procedures to get the job done. Testing on the ground helps us know we're on the right track."

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