Electric spaceship propulsion
An electric spaceship drive is a propulsion method for space travel in which the ejected supporting mass is independent of the energy carrier. Together with other components such as the neutralizer, it forms the electric drive system .
Electric space propulsion systems can be divided into three classes based on the underlying principle of thrust generation: electrothermal , electrostatic and electromagnetic propulsion.
Electrothermal drives
Electrothermal drives are the closest to chemical engines . Here the electrical power is used to heat a working gas to high temperatures. These temperatures are generally higher than the combustion temperatures of classic chemical fuels. Compared to the latter, this increases the exit speed of the gases during expansion in a nozzle and thus the specific impulse. The most important basic types of electrothermal drives are the Resistojet , which heats the working gas via a resistor, and the thermal arc drive , in which the gas is passed through an arc.
Electrostatic thrusters
Electrostatic engines accelerate electrically charged particles in an electrostatic field. The type of particles and their generation can be very different. In the field effect emission engine ( FEEP ), ions (e.g. Cs + , In + ) are emitted directly from a liquid surface by strong fields. Electron impact ionization sources ( ion thrusters ) generate plasma and thus also ions (e.g. Xe + ) in a gas, either by a high-frequency or a direct current discharge. Colloidal engines atomize the usually liquid fuel into small, electrically charged droplets. In most cases, a system of differently charged grids is used to build up the electrostatic acceleration field. Of all types of electric drives, the electrostatic systems have the highest specific impulse. As a result, however, they also have the greatest power requirement per thrust.
The Hall engine or stationary plasma engine ( SPT ) and the highly efficient multi-stage plasma engine ( HEMP ) occupy a special position between electrostatic and electromagnetic systems . Here, a magnetic field hinders the ability of the electrons to move, so that a potential gradient can be maintained even without a grid system. In this potential gradient, ions (Xe + ) are accelerated outwards.
Electromagnetic thrusters
Electromagnetic thrusters use crossed electric and magnetic fields to generate a force on a plasma. In contrast to the electrostatic thrusters, the outward accelerating force generally acts on both differently charged components of the plasma. Therefore these types are called real plasma engines. The most prominent representatives of this class are the magnetoplasmic dynamic engine ( MPD ) and the iMPD engine .
state of development
The most advanced have been the development of thermal arc engines, electron impact ionization sources and Hall drives . All three types have been deployed on satellites. The American ion engine NSTAR was successfully used as the main propulsion system on the interplanetary space probe Deep Space 1 , as was a Hall-type engine on the European lunar probe SMART-1 .
All major space agencies have their own program for the development and establishment of electrical drive systems, which is intended to ensure the coordinated continuation of development.
See also
Web links
- I. Physikalisches Institut der JLU-Giessen: Physical principles of the electric drive ( Memento from March 4, 2016 in the Internet Archive )
- Uni Stuttgart Electric Drives: Electric space propulsion
- Internet Encyclopedia of Science: electric space propulsion (English)
- Electric / Xenon in the Encyclopedia Astronautica (English)