WASHINGTON — The U.S. Senate gave final passage to an energy and water spending bill Oct. 15 that denies President Barack Obama’s request for $30 million for the Department of Energy to restart production of plutonium-238 (pu-238) for NASA deep space missions.

The House of Representatives originally approved $10 million of Obama’s pu-238 request for next year, but ultimately adopted the Senate’s position before voting Oct. 1 to approve the conference report on the 2010 Energy-Water Appropriations bill (H.R. 3183). The bill now heads to Obama, who is expected to sign it.

NASA relies on pu-238 to power long-lasting spacecraft batteries that transform heat into electricity. With foreign and domestic supplies dwindling, NASA officials are worried the shortage will prevent the agency from sending spacecraft to the outer planets and other destinations where sunlight is scarce.

Brian Berger is editor in chief of SpaceNews.com and the SpaceNews magazine. He joined SpaceNews.com in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...