Liquid/Vapor-Hydrazine Thruster Would Produce Small Impulses

A report proposes a liquid/vapor-hydrazine thruster for use in controlling the attitude of a small spacecraft. From the upstream to the downstream end, the thruster would include a tank containing liquid hydrazine, a fast liquid valve, a heated prevaporizing plenum, a fast gas valve, and a heated catalytic bed. In one mode of operation (the conventional mode), heat would not be supplied to the prevaporizing plenum; instead, liquid hydrazine would be fed directly to the heated catalytic bed. In another mode of operation, heat would be supplied to the prevaporizing plenum, and the gas valve would be opened in brief pulses to pass the hydrazine vapor to the heated catalytic bed to produce small pulses of thrust. The use of vapor (as compared with liquid) feed in the pulse mode would make it possible to generate smaller impulses, which are better suited for highly precise spacecraft maneuvers.