There are major concerns within the National Missile Defense system that the boosters to loft the kill vehicles toward enemy missiles may not be ready. Boeing is in charge of booster design, and is running behind schedule. There are problems with integrating the booster's components; some have been tested in other rockets but they have yet to be tested as a single unit. There are concerns that the thrust-vector control system may not be up to the job and that the top speed of the kill vehicles (at the time the booster burns its last fuel) may not be fast enough to intercept incoming ICBMs. In recent testimony to a Congressional panel, Air Force LtGen Kadish spoke of aggressive exploration of ways to restructure the booster program, Pentagon-speak for fears that they booster program may have to start over from scratch. --Stephen V Cole