The Department of Energy's Sandia National Laboratories are refurbishing the Spin Rocket Motor, a prime component of the B61 nuclear weapon system. Both the original motor produced in i966 and the version last produced in 1991 are the subjects of the refurbishment. Both motors, which are essentially identical, produce thrust to arm the weapon. In December 2001, the National Nuclear Security Administration (NNSA) received Nuclear Weapons Council Standing and Safety Committee (NWCSSC) approval to study the feasibility and cost of replacement options In April 2003, the NWCSSC approved the development of a new Spin Rocket Motor based on Sandia's assertions that test data collected between 1997 and 2002 showed the motors, due in largc: part to "detrimental aging," were not performing according to specifications. Detrimental aging occurs when a component's age prevents it from performing to meet military requirements. The first production unit for this refurbishment effort is scheduled to be completed in December 2006, at an estimated overall project cost of about $60 million.