The US Navy has now decided to convert four (instead of just two) Trident missile submarines to carry conventional cruise missiles. Moreover, it is studying new kinds of warheads and payloads for the missiles, as well as new missiles. Some possibilities include a supersonic missile to hit targets that are likely to move, an unmanned recon drone that could be lofted over the target by a cruise missile and then extend wings and cruise like an aircraft, and various kinds of bomblets, penetrating warheads, or fuel-air explosives.--Stephen V Cole