(07/03/1975) -- ASTP asstronauts Donald slayton, Vance Brand and Thomas Stafford leave the transfer van at Complex 39's Pad B and enter the pad elevator during the Countdown Demonstration Test. The test, a step-by-step dress rehearsal for the July 15 launch, simulates the actual countdown but without the propellants in the Saturn IB launch vehicle's fuel tanks. The fueled portion of the test was conducted yesterday.