NASA’s nuclear power plans face higher hurdles

Engines for a cosmic ocean
Under an agreement signed last August, the reactor for Prometheus is being developed for NASA by the U.S. Department of Energy’s Office of Naval Reactors in Washington. They are no newcomers to nuclear power plants. But they haven't done this sort of thing for space missions.

The Office of Naval Reactors provides nuclear propulsion plants for the Navy’s fleet of aircraft carriers, as well as attack and strategic submarines. The Naval Reactors organization brings to the table a track record spanning 50-plus years of expertise in developing powerful, safe, rugged, reliable, compact and long-lived reactor systems for use in unforgiving environments.

The office declares that more than 130 million miles have been safely steamed on nuclear power. They currently operate more than 100 reactors and have accrued more than 5,500 reactor-years of operations. Because of its demonstrated reliability, the organization salutes the fact that U.S. nuclear-powered warships are welcomed in more than 150 ports of call in over 50 foreign countries and dependencies.

The dual-agency Prometheus partnership also involves Knolls Atomic Power Laboratory in Schenectady, N.Y., as well as Bettis Laboratory in Pittsburgh and other supporting Department of Energy national laboratories.

Infinite heat sink
"There’s a lot of enthusiasm. They have staffed up vigorously," said John Casani, Prometheus project manager at JPL.

Sailing Earth’s ocean or plying through the ocean of space under nuclear power — there’s a difference, Casani explained. For one, the space reactor has to be smaller and more compact than on submarines.

"Running a reactor … you reject heat to the ocean, and that’s an infinite heat sink. Space, you’ve got to reject heat through radiators. And the radiation environment is not from the reactor so much, but the radiation of space itself," Casani told Space.com in an interview during February’s Space Technology and Applications International Forum, held in Albuquerque, N.M.

So simply bolting in a sub’s nuclear power plant into a spacecraft isn’t in the cards.

The Office of Naval Reactors didn’t sign up for space reactor work without forethought about putting their record of success at risk. The office also had to think through the implications of getting hooked up with another agency, dealing with security issues and avoiding overcommitment of its work force.

"Yes, they do things differently than we do," Casani added. "But they are driven by the same imperative for success, safety and doing it right. I think we’ve integrated very well with them."

The Prometheus space reactor system would provide more electrical power than available for past missions. That added energy can greatly enhance the capability of electric propulsion, the number and variety of scientific instruments on the spacecraft, the rate of data transmission, and orbital maneuvering.

Template spacecraft
Last September, JPL selected Northrop Grumman Space Technology of Redondo Beach, Calif., as the contractor for co-designing the proposed Prometheus spacecraft. The contract award is for approximately $400 million, covering work through mid-2008.

"Prometheus is the project name, not the destination," said Peggy Nelson, Northrop Grumman vice president and project manager for Prometheus 1. "Prometheus is a template spacecraft that will explore a number of different locations," she told Space.com in a phone interview.

Nelson’s group is working on aspects of JIMO, as well as alternative first missions. Those new missions would be shorter in duration, on the order of three to five years, she said.

There’s a big difference in short-duration Prometheus hardware, Nelson advised, contrasted with JIMO’s life expectancy of 20 years. Redundancy issues are reduced. Also, less propellant has to be toted. And that impacts the overall scale of the Prometheus-class space vehicle.

The key now is having a space nuclear reactor design for the first Prometheus mission that, in fact, also can be utilized for a second mission.

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