 The general concept was endorsed by the Council and by High Frontier, Inc., a Washington-based group headed by Lt. Gen. Daniel O. Graham that lobbied for SDI programs.Working together, Hunter and High Frontier convinced SDI management and other national officials that a study should be initiated to determine once and for all the feasibility of SSTO vehicles for military missions.This led to a U.S. Department of Defense (DoD) program to design a single-stage vehicle that could replace military satellites on short notice during a national emergency.