A report proposes monopropellant microthrusters for a new generation of miniature spacecraft with mission lifetimes stretching into years. These thrusters would include micromachined nozzle/chamber assemblies containing microvalves, designed according to emerging concepts of microelectromechanical systems (MEMS). Like some previously designed monopropellant thrusters, these thrusters would generate expanding gases and thereby generate thrust through catalytic dissociation of liquid hydrazine; however, these thrusters would be considerably smaller. Moreover, instead of putting catalytic pellets in chambers according to the previous designs, one would roughen the inner walls of the chambers and coat them with iridium or some other suitable catalyst. The micromachined thruster assemblies would be enclosed within aerogel bodies for thermal insulation. Each thruster would be heated with a small amount of power (< 1 W) to promote vaporization. Flow geometries and the characteristic times of residence and dissociation of hydrazine would be optimized.
This work was done by Philip Moynihan and Carl Guernsey of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Monopropellant Hydrazine Microthruster," access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Machinery/Automation category,or circle no. 180 on the TSP Order Card in this issue to receive a copy by mail ($5 charge). NPO-20159