NASA Plans to Refuel Mock Satellite at the Space Station
An artist's illustration of DARPA's Orbital Express spacecraft in orbit, with the ASTRO servicing vehicle (left) bearing down on NextSat.
Credit: DARPA.

SAN FRANCISCO ? The technology and tools already exist to allow people and robots to repair and refuel satellites in orbit. What is lacking is the recognition of that capability by senior government officials and a business model to enable commercial companies to profit from the enterprise, according to government and industry officials attending a workshop March 24-26 sponsored by the NASA Goddard Space Flight Center and held at the University of Maryland University College in Adelphi, Md.

"It's pretty clear," said Frank Cepollina, NASA deputy associate director in the space service capabilities office at NASA Goddard in Greenbelt, Md. "The time for study is over. We have now got to move forward."

The workshop was one step in a space agency campaign to demonstrate that a wide range of satellite repair, refueling and maintenance activities can be performed by human and robotic missions. NASA is conducting a study to determine the feasibility and cost of in-orbit satellite servicing. The results of that study are scheduled to be delivered to Congress in September, said Cepollina, NASA's lead engineer for Hubble Space Telescope repair missions.

NASA's long-term goal is to prove that satellites can be serviced in orbit, conduct a pathfinder mission to prove the concept and then transfer the technology to the commercial sector, Cepollina said.

NASA plans to demonstrate in-orbit satellite refueling at the international space station with the help of Dextre, the two-armed Canadian robot. In an experiment scheduled to be conducted in the next six to 12 months, Dextre will be equipped with special tools on the end of its arms to cut through a satellite's exterior, insulation and wiring, hook up a hose and pump hydrazine into the satellite. For the experiment, NASA will be relying on a simulated satellite, being built by NASA Goddard engineers and scheduled to be completed in October. The mock spacecraft ? essentially just the back end of a satellite ? will be bolted to an Express Logistics Carrier, a platform attached to the space station's exterior. Once the simulated spacecraft and tools are completed, the equipment will be sent to the space station.

"The simulated spacecraft is fully wrapped, like a spacecraft in geosynchronous or low Earth orbit," Cepollina said. The experiment will be directed by astronauts on the ground, probably located at Johnson Space Center in Houston, and will not involve any of the space station crew. "The fundamental objective is to prove that you don't have to design your satellites to be refueled on orbit," Cepollina said. "You can refuel existing fleets."

Following this experiment, NASA plans to demonstrate the work can be done autonomously, Cepollina said. That demonstration will be important to show that satellites traveling 14,000 kilometers from Earth in geosynchronous orbit also can be refueled and repaired. "We are trying to develop the dexterity of robots to fix spacecraft so they can continue to do their jobs, Cepollina said. "You would never buy a car that was not repairable, why should we buy a satellite that's not?"

During the workshop, participants reported on in-orbit servicing and refueling projects conducted by private industry, the U.S. Naval Research Laboratory, the U.S. Defense Advanced Research Projects Agency (DARPA) and NASA Goddard. Speakers also cited projects under way in Germany and Canada. In February, the German space agency DLR awarded a contract to OHB Technology of Bremen, Germany, to act as the prime contractor for the detailed design phase of the German Orbital Servicing Mission, a program that includes robotic technology to repair, refuel and de-orbit satellites.

Canada's MacDonald Dettwiler and Associates (MDA) Corp. is preparing to launch a mission in approximately three years to deliver 2,000 kilograms of fuel to an orbiting geostationary satellite. That work is being done for a customer that the company is not identifying. "We will validate the whole idea of on-orbit servicing," said John Lymer, MDA chief robotics engineer. "We will show that it is not only useful to the client, but that the service provider can make money as well." In order to see a profit, however, MDA must keep program costs as low as possible by relying on existing flight technology, Lymer said.

In fact, the only way companies can make money servicing satellites in orbit is to spread the cost of the missions and associated technology across multiple jobs, said Glen Henshaw, a roboticist at the Naval Research Laboratory in Washington. "It's not a technology problem," he added. "We have the technology to establish all of these capabilities today, but the technology can help us close the business case."

Henshaw compared the business of satellite servicing with that of automobile servicing. An automobile's value and the way it is used helps to determine the types of repairs a customer is willing to make. Few companies would rebuild a Toyota engine, but mechanics will perform that work to fix an extremely valuable automobile such as a Maserati.

By comparison, NASA is likely to pay a far higher price to repair and refuel billion-dollar space telescopes than companies would be willing to pay to fix communications satellites, Henshaw said. Still, other workshop participants said that the sheer quantity and value of government and commercial satellites in orbit indicate that there is an enormous market for in-orbit repair and maintenance activities.

To bring down the cost of those missions and make them more profitable, companies are developing a variety of technologies including advanced propulsion systems, improved fault detection programs, sophisticated sensors and equipment designed to ease the process of transferring cryogenic fuel, according to workshop participants.

Another hurdle to clear before in-orbit servicing becomes routine is to convince senior government and industry officials that in-orbit servicing can be done safely and effectively, said U.S. Air Force Lt. Col. Fred Kennedy. Kennedy was the program manager for DARPA's Orbital Express program, a successful 2007 demonstration of autonomous satellite refueling and maintenance.

"The technology can help with that," Henshaw said. "We can beat down some of the perceived risk."

However, some decision-makers will be skeptical until they see concrete demonstrations of in-orbit satellite servicing. "We should just go do it," Henshaw said. "Until we do it, nobody is going to believe we can do it."