Transient Fluid Flow in Short-Pulse Operation of Bipropellant Thrusters

The flow of propellants into an evacuated injector during a short pulse was measured for several propellants using two different methods. In the first method, the fluid front was observed with a high-speed camera. In the second method, the average fluid velocity during a pulse was determined from the pressure rise in the chamber from'a pulse. The propellants tested were hydrazine, monomethyl hydrazine, hexane, water, and nitrogen tetroxide. The measured velocities are an order of magnitude slower than the steady-state velocities under the same conditions. The results are consistent with the development of a flow controlled by inertia and viscous drag. The implications for pulsed operation of bipropellant thrusters are discussed.