Project Prometheus, NASA’s multibillion-dollar nuclear power and propulsion initiative, has a new home inside the U.S. space agency.

Begun as the Nuclear Systems Initiative in 2002, the program was given a new name in 2003, a bigger budget and its first mission: the Jupiter Icy Moons Orbiter (JIMO).

Now, with an ambitious new space exploration agenda handed down by the White House, NASA is making more changes to Project Prometheus.

JIMO’s launch date is slipping and responsibility for developing the nuclear systems NASA says it needs to kick solar system exploration into high gear is being given to the newly established Exploration Systems Enterprise. The new enterprise will be headed by retired U.S. Navy Adm. Craig Steidle, a veteran of the Pentagon’s Joint Strike Fighter program.

The move takes the bulk of Project Prometheus and its funding -- expected to top $438 million in 2005 — away from NASA’s Space Science Enterprise.

Ed Weiler, NASA associate administrator for space science, said his organization remains in charge of setting the science guidelines for the JIMO mission and will continue to oversee the development of the radioisotope power generators -- essentially plutonium-powered batteries -- the agency needs for a long-lasting science rover it is launching to Mars in 2009.

The rest of Project Prometheus, including the design and development of the JIMO spacecraft and its nuclear propulsion system, is moving to Steidle’s organization, literally just down the hall from Weiler’s office at NASA headquarters here.

But the move is more than just a change of location for the program. It also marks a change in the way that NASA has historically gone about developing spacecraft and other major systems. Now, instead of one organization setting the science requirements and developing the spacecraft -- a process that usually entails a spirited tug of war between what scientists want to do and what engineers think can be done -- the two pieces will be split between two organizations.

Weiler said he sees no major problems with the new way of doing business. “I have spent a lot of time with Craig Steidle,” Weiler told reporters Feb. 3. “We have a good start at a good relationship both at my level and at the division director level.”

The new relationship goes both ways. For example, Weiler’s space science organization will be in charge of NASA’s new lunar orbiter and lunar lander missions planned for 2008 and 2009 respectively, but the goals of the pair of missions -- which will be technology-driven instead of science-driven -- will be established by Steidle’s exploration enterprise.

New management is not the only change in store for Project Prometheus. In NASA’s 2005 budget request, JIMO’s target launch date has slipped a few years to 2014 or 2015. In NASA’s budget request a year ago, the target launch date was around 2011.

Still, the three industry teams competing for the contract to design and build JIMO are hoping NASA will go ahead as planned and pick a prime contractor in 2005. All three teams are currently working on conceptual designs under $5 million study contracts from NASA.

James Crocker, vice president of civil space for Lockheed Martin Space and Strategic Missiles, Denver, said the later launch date could allow some promising new technologies to come into play -- he declined to be specific, citing competition sensitivity -- but he would still like to see NASA select a prime sooner rather than later.

“This is a very challenging mission and I think we need to pick a contractor and move on with it,” Crocker said in an interview.

Joe Mills, JIMO program manager at Boeing NASA Systems in Pasadena, Calif., said his team -- which includes Boulder, Colo.-based Ball Aerospace & Technology -- also still expects to submit their bid this summer with NASA making a decision sometime before the end of the year.

JIMO has the potential to be the biggest and most expensive spacecraft NASA has ever built. Although NASA has yet to set firm requirements for JIMO -- or make public a cost estimate -- agency officials are generally looking at a spacecraft built to operate 10-15 years.

The mighty spacecraft NASA envisions would be powered by a nuclear fission reactor capable of pumping out 100 kilowatts of power. The reactor would power JIMO’s propulsion system and provide more electricity than any spacecraft has ever had for instruments, computers and communications.

Mills said the spacecraft could easily be 50 meters long when fully deployed -- about half the size of the international space station. Boeing, at least, is concentrating on designing a spacecraft light enough to launch in one piece aboard a heavy lift version of either the Delta 4 or Atlas 5 rockets.

Craig Staresinich, vice president for Project Prometheus at Northrop Grumman Space Technology, Redondo Beach, Calif., said he expects JIMO to be just the first in a long line of nuclear-powered spacecraft ordered by NASA for solar system exploration. Aside from the enhanced mobility promised by nuclear propulsion -- JIMO is being designed to visit three of Jupiter’s moons during its mission -- nuclear spacecraft are expected to be anything but power constrained.

The big challenge for scientists, Staresinich said, would be finding creative ways to take advantage of all the surplus power spacecraft like JIMO can provide.

“It opens up new paradigms and new ways of thinking about the science we can do with this much power,” he said. “That’s the beauty of this mission. Power is available.”