Air Force officials announced plans Thursday to increase unmanned launches at this coastal base, after reaffirming a decision to put its space shuttle facilities in mothballs. Col. Sebastian Colitore said at the 25th Annual Space Congress convention Thursday in Cocoa Beach, Fla., that the Air Force would build one new launch pad and modify another at the base to launch the Titan 4 missile. His statement came a day after Maj. Gen. Donald Cromer, chief of the Space and Missile Test Organization at Vandenberg, reaffirmed a February announcement that the $3.5 billion shuttle launch facility at Vandenberg was being placed in mothballs because of federal budget cuts. Cromer said the move would save the Air Force $40 million in 1989. The Air Force plans to use the shuttle pad to launch other, unmanned missles, Maj. Sgt. Bruce Zielsdorf, a Vandenberg spokesman, said Thursday. The Titan 4, the military's workhorse missile, carries huge, shuttle-sized payloads and satellites into orbit. The first planned launch of the Titan 4, which is 20 feet taller than the shuttle at 204 feet, is set for February 1990, Colitore said. The Air Force also will modify another launch pad for old Titan 2 intercontinental missiles that are being refurbished into space boosters, said Lt. Col. Mike Callaway, project manager. The first launch of the Titan 2 is set for July 1 at Vandenberg, he said. Colitore said the Air Force would increase its unmanned launches at Vandenberg, 150 miles northwest of Los Angeles on the California coast. The Vandenberg shuttle site has been regularly maintained at a cost of $50 million a year since the space shuttle Challenger exploded during launch in Florida in January 1986, killing the seven people aboard. It was to be the next site of a shuttle launch in July 1986. But after the Challenger disaster, NASA moved the launch back to 1992. Now launches have been indefinitely postponed at Vandenberg, although an August shuttle launch is planned at Cape Canaveral in Florida. Even if Vandenberg's vast shuttle complex, which includes a launch pad, buildings and runway, were to be reactivated, it would take at least four years for it to be functional, Zielsdorf said.