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Engineers at NASAs Goddard Space Plight Center are sifting ideas received last week on applying in-space servicing techniques pioneered with the Hubble Space Telescope to "previously impossible" science, exploration and other space missions.
An in-orbit testbed to validate robotic techniques for refueling satellites not designed to be refueled is already in development under a $20-million congressional appropriation. And using the responses to a broad request for information (RFI) on the subject, plans are afoot to develop a set of notional space missions that could be enabled by human and robotic servicing.
These could include building and maintaining space-based fuel depots, an idea proposed as an option for future human exploration by Norman Augustine and his panel of experts who reviewed options for human spaceflight last summer. The results, to be summarized in a report to Congress in September, are intended to guide future technology developments for both human and robotic spaceflight.
"The purpose of the study is to use the servicing experience gained by NASA, including servicing Hubble, to identify capabilities for future servicing," says Preston Burch, the Hubble program manager.
In addition to the analytical work, Goddard engineers are planning an orbital testbed designed to be mounted on the International Space Station (ISS) that would simulate a satellite in need of refueling. The flight-test concept calls for using the Canadian-built Special Purpose Dexterous Manipulator (Dex-tre) to simulate cutting into a spacecraft's insulation, tapping its fuel plumbing, and refilling its tanks to extend its service life.
"We've already developed a prototype tool that's pretty cool. It can cut through [a satellite's] external skin, snip the safety wire on the cap on the fuel valve, attach the hose, turn the valve and transfer the fuel into the vehicle," Burch says. "We're •hoping to demonstrate that on the ISS."
The work began with the S20 million allocated in Fiscal 2009 to capture lessons learned from the five Hubble-ser-vicing missions with spacewalking astronauts, and from the planning that went into a robotic servicing mission, which ultimately was dropped. Burch stresses that the appropriation does not cover an actual flight test, which would involve attaching a testbed to the outside of the station and putting Dextre to work on it.
"This is being proposed," Burch says. "We're laying the groundwork in the [anticipated] future funding."
The study will gauge how robotic and human servicing can aid several notional missions in low-Earth and geostationary orbits, and at the Sun-Earth Lagrange points about 1 million mi. from Earth where the planned James Webb Space Telescope will deploy. In addition to refueling spacecraft and setting up orbiting fuel depots, space-servicing possibilities include installing new instruments on old spacecraft, and assembling spacecraft too large to launch in one piece, Burch says.
The notional missions will be refined based on the responses to the RFI, and on an open workshop set for Feb. 16-18.
We do not want to constrain ourselves prematurely on a particular mission or technology area," says Burch. "We want to blue-sky this a bit in the early going, and try to envelope all of the potential technologies, users and missions that can do this. That's why we're taking this approach of a large suite of notional missions to be studied."
The study and its workshop are open, and, prior to the Jan. 15 deadline for submitting responses, Burch said NASA had discussed the undertaking with potential international and commercial participants as well as with government organizations. Formal responses will be vetted by NASA to ensure that proprietary data are not made public, he says, and strict attention will be paid to U.S. technology-export controls under the International Traffic in Arms Regulations (ITAR).
"A significant reason for issuing the RFI is to ensure coordination and collaboration between government and commercial efforts in this area," Burch says.
Many techniques and tools pioneered on the Hubble were used to build the ISS; the lessons-learned study and possible flight testing will continue this evolution. As the White House finesses its Fiscal 2011 NASA budget and the direction for the Constellation program of exploration vehicles, Burch says the follow-on space-servicing work will be valuable regardless of the final decision.
“We tend to think of Constellation as this human-based capability, but we feel that robots have a really important place in the future of in-space servicing”, he says. “So it's really much bigger than constellation.”
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