WATER-HAMMER IN A SPACECRAFT PROPELLANT FEED SYSTEM

Water hammer and pressure surges in shuttle-launched spacecraft are of special concern in the priming of evacuated propellant lines which are designed to satisfy launch safety requirements. A series of tests using water as a reference fluid was performed to ascertain the integrity of a bipropellant feed system subjected to water hammer effects. A variety of priming flow configurations, ranging from straight-tube flow to full scale network flow, were tested. The test data were correlated using analytical modeling that combines water hammer principles with dissipation due to friction and branching effects. It is concluded that 1) in a network of branches fed from a "trunk" line manifold, the potential for water hammer is greatly reduced by frictional dissipation along the "trunk" line compared with ideal, frictionless water hammer, and 2) further branching dissipation, of secondary importance, results in acceptable low water hammer throughout the representative propellant feed system. The cushioning effect of inert gas prepressurization in the manifold on the priming pressure surges was also correlated on the assumption of adiabatic gas compression.