Air Force managers cleared the first of 20 new Delta 2 rockets for blastoff at Cape Canaveral, Fla., today on a voyage marking a new era in America's resurgent military space program. The launch of the 128-foot rocket, the first of a new breed of unmanned boosters ordered in the wake of the Challenger disaster, was delayed a day due to bad weather conditions, Air Force officials said. The rocket will boost into orbit a $62-million Navstar Global Positioning System (GPS) satellite, the first of an $8-billion series of 21 that is expected to revolutionize navigation. From its orbit 11,000 miles above the Earth the GPS will beam two channels--one to be sold for commercial use and the other for the U.S. military and its allies, officials said. The military has spent the last three years building a new fleet of rockets to reduce its dependence on the shuttle program.