Porous materials for ion-electrospray spacecraft microengines

Porous materials are essential for ion-electrospray propulsion systems (iEPS). These are miniaturized devices designed to provide mobility to small satellites after they have been launched into orbit; they also can be used as ion sources for applications in microtechnology and nanotechnology. This study investigates the use of xerogels as a family of materials for electrospray applications due to their large surface-area:volume ratio and exceptional pore-size uniformity. In particular, laser-ablated carbon xerogel substrates have been selected for initial synthesis and characterization. Preliminary data on emitted ionic current versus operating voltage curves will be presented for arrays of tips 300 μm tall and 20 μm wide spaced on a 450-μm hexagonal lattice. Aerogels and xerogels present an opportunity to attain more-controllable emitter shapes than previous materials such as porous glass or metals. Improved emitter shape control and pore structure uniformity should have a positive impact on device lifetime and performance.