The US Air Force wants to retain intercontinental ballistic missiles after the current inventory reaches the end of their operational life in 2020. The Air Force wants to maintain only single-warhead missiles, not the large 10-warhead Peacekeepers. One option is to extend the service lives of the Minuteman-3 force, which would be a short-term solution. Another is to build an entirely new missile. A final possibility is to build a modified version of an off-the-shelf commercial booster, although only if it could fit into existing silos.--Stephen V Cole