Field emission devices for space applications

Abstract

AbstractIn the late 1950s, interest arose in the US to use electrostatic droplet sprayers as a new heavy charged particle source for electric space propulsion. Originally, charged droplets were produced from conductive organic liquids. Around 1960, first attempts were made to use liquid metals as the charge material. It was discovered that the device was a very high brightness source of metal ions, which could be focused to spots of nanometer dimensions. This liquid metal ion source (LMIS) has developed into a commercially exploited device for ion microbeam technology. In Europe, the potential of the LMIS as a very high specific impulse ion thruster has been recognized. Since the 1970s, development of cesium and, later, indium ion thrusters has been going on. Presently, the development is at an advanced stage. Contracts have been issued by ESA to equip microsatellites with an attitude control system based on field (ion) emission electric propulsion (FEEP). The first technological test to verify microgravity operation of the indium LMIS was performed in 1991 on the Russian MIR space station, and from 1992 the device has been exploited for active potential control of scientific satellites and for on‐site planetary mass spectrometry in seven space missions. The first gas field‐ionization source was flown as early as 1977 on a sounding rocket and in 1986 to comet Halley. Apart from these field emission devices actually flown, field ion‐ and electron devices are under development or discussion for a number of other space applications. The latest developments and future prospects are discussed. Copyright © 2007 John Wiley & Sons, Ltd.