Apollo Service Module fuel tank. A positive expulsion titanium fuel tank approx. 23 in. tall and 12 in. in diameter with a large ID tag listing part number 8271-471151, serial number 100311510044, and manufactured on April 10, 1966 by Bell Aerospace Corp. with pressure rating and control number stamps. The Service Module reaction control system was made up of four sets of four rocket engines that used hypergolic propellants. This tank supplied the unsymmetrical dimethyl hydrazine (UDMH) fuel for those engines.