The MDA envisions a "multi-layered" system in which different elements take a shot at a missile at different phases of its trajectory, yet this is, even under the most optimistic of projections, a far-off dream. Theoretically, the most effective stage of a layered system is the first stage, known as "boost-phase intercept," in which air- or space-based interceptors knock down a missile just after it is launched, while it's still rising, before the warhead separates from the booster rocket—in short, while it's still a large object emitting hot exhaust plumes. However, Gen. Kadish said in the Dec. 17 press conference that the boost-phase part of the Missile Defense program is "the most immature" of them all. Nothing exists. Kadish says that, for the foreseeable future, the ground-based interceptors are designed to shoot down long-range missiles; the sea-based interceptors are for medium-range missiles; the modified Patriots are for short-range missiles. In other words, in the current plan, there's only one layer of defense for each type of missile and therefore none of the redundancy that could help make missile defense effective. Meanwhile, the MDA's headache of the moment is finding a decent rocket-booster for its interceptors. The program's last two tests were called "no-tests" (neither successes nor failures) because the booster didn't work.