Underpinning the stewardship program is ASCI, which aims to provide the necessary computing power. Nuclear weapons basically have been designed on computers for almost 50 years. This work only could be performed in two dimensions, however, and these designs always could be tested in the government's underground Nevada test range. Sophisticated diagnostics would measure the warhead yield to perfect the design. The recently reached comprehensive test ban treaty bars this underground warhead testing, so nuclear weapons engineers no longer have the luxury of live-fire tests to validate their designs.
Testing becomes all the more crucial as the nuclear stockpile ages.
Fissionable material is highly dynamic, and its caustic environment causes cracks and other deteriorations in warheads that have been discovered when weapons are dismantled periodically. Cooper notes that, in the past, these weapons always could be tested to determine if their long shelf life affected their yields. Another concern is warhead safety, as scientists need to determine whether a weapon might explode in an airplane crash, for example. One involves the aging of the weapons, many of which already have been in existence longer than anticipated. While the department has a considerable database of test results from the past 50 years, these data are not coordinated and are not as extensive as is needed.