Back to the Future - Serviceable Spacecraft Make a Comeback

Estimated reading time: 7 minutes

“GEO may not an option for these missions because of the thermal-stability requirements,” Kienlen said. “One stumbling block is the perception that there is not a plausible scenario for servicing satellites at SEL2. We don’t want to force all future flagship missions to a lesser-performing orbit because they are required to be serviceable. So, we will figure out how to take servicing to them.”

“It’s not like we have to reinvent the wheel. We have never stopped developing servicing technologies. The difference today is that future flagship missions are required to be serviceable,” added Julie Crooke, a Goddard engineer, astrophysics technical manager, and member of a team that has been studying one of several future mission concepts. “With appropriate technology investments, we are on a clear path to demonstrating a servicing capability far from low-Earth orbit,” she said.

Beth Keer, who heads SSCO’s Advanced Concepts Office, agrees. “We have demonstrated robotic refueling on the space station. It’s one of the stepping stones along the way to making robotic servicing the way of the future.”

Robotic Refueling

Now in the second phase of its on-orbit demonstration aboard the International Space Station, NASA’s Robotic Refueling Mission (RRM) is using the Canadian Space Agency’s two-armed robotic handyman, Dextre, to show how future robots could service and refuel satellites in space.

One of those tools, VIPIR, short for Visual Inspection Poseable Invertebrate Robot, is a robotic, articulating borescope equipped with a second motorized, zoom-lens camera that would help mission operators who need robotic eyes to troubleshoot anomalies, investigate micrometeoroid strikes, and carry out teleoperated satellite-repair jobs. NASA successfully demonstrated VIPIR’s capabilities earlier this year. During RRM’s third phase, the SSCO team plans to demonstrate the transfer of xenon, a colorless, dense noble gas potentially useful for powering ion engines.

RRM, however, is only one piece of SSCO’s ongoing efforts to making servicing a tried-and-true capability for future missions.

ROSE and Restore

To be easily serviceable, regardless of its orbit, the satellite itself must be specially designed to accommodate repairs. For example, NASA’s MMS serviceable satellite bus featured a modular design that made it easy for astronauts to install a new attitude control system when the original failed on Solar Max.

Though not modular like MMS, Hubble did support on-orbit servicing on a component level. Like opening a door, astronauts literally would pull out an instrument before reinserting the new one into the same cavity — a job made easier with the observatory’s 76 handholds. However, Hubble’s lack of modularity meant that NASA had to develop special tools and procedures specifically for nearly each component and task.

“Although Hubble servicing was extremely successful, the missions were complex and required a highly orchestrated combination of robotic and astronaut activities,” observed Dino Rossetti, of Conceptual Analytics in Glen Dale, Maryland, in a paper submitted at an American Institute of Aeronautics and Astronautics conference in September.

Modularity is key, and SSCO is taking it to a new level, Keer said.

The organization now is developing the Reconfigurable Operational spacecraft for Science and Exploration (ROSE), a low-cost spacecraft concept that seeks to build on the success of MMS. The organization’s overriding goal is long-term affordability and servicing at a system level, which would make ROSE highly flexible for medium-size missions, Keer said.

“We view ROSE as a pathfinder for future missions,” Reed added.

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