Field Emission Electric Propulsion
Encyclopedia
Field-emission electric propulsion (FEEP) is an advanced electrostatic propulsion concept, a form of ion thruster
, that uses liquid metal
(usually either caesium
, indium
or mercury
) as a propellant. A FEEP device consists of an emitter and an accelerator electrode. A potential difference of the order of 10 kV is applied between the two, which generates a strong electric field
at the tip of the metal surface. The interplay of electric force and surface tension generates surface instabilities which give rise to Taylor cone
s on the liquid surface. At sufficiently high values of the applied field, ions are extracted from the cone tip by field evaporation or similar mechanisms, which then are accelerated to high velocities (typically 100 km/s or more).
A separate electron source is required to keep the spacecraft electrically neutral. Due to its very low thrust (in the micronewton to millinewton range), FEEPs are primarily used for microradian, micronewton attitude control on spacecraft
, such as in the ESA/NASA LISA Pathfinder
scientific spacecraft.
Ion thruster
An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
, that uses liquid metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
(usually either caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
, indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
or mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
) as a propellant. A FEEP device consists of an emitter and an accelerator electrode. A potential difference of the order of 10 kV is applied between the two, which generates a strong electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
at the tip of the metal surface. The interplay of electric force and surface tension generates surface instabilities which give rise to Taylor cone
Taylor cone
A Taylor cone refers to the cone observed in electrospinning, electrospraying and hydrodynamic spray processes from which a jet of charged particles emanates above a threshold voltage...
s on the liquid surface. At sufficiently high values of the applied field, ions are extracted from the cone tip by field evaporation or similar mechanisms, which then are accelerated to high velocities (typically 100 km/s or more).
A separate electron source is required to keep the spacecraft electrically neutral. Due to its very low thrust (in the micronewton to millinewton range), FEEPs are primarily used for microradian, micronewton attitude control on spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
, such as in the ESA/NASA LISA Pathfinder
LISA Pathfinder
LISA Pathfinder is the revised name for SMART-2, a NASA/ESA space probe to be launched in June 2013. SMART stands for Small Missions for Advanced Research in Technology. The aim of the LISA Pathfinder is to test technologies needed for the Laser Interferometer Space Antenna, a joint NASA/ESA...
scientific spacecraft.
External links
- FEEP – Field Emission Electric Propulsion at Alta SpA
- FEEP thrusters studied in the Nonequilibrium Gas and Plasma Dynamics GroupNonequilibrium Gas and Plasma dynamics groupThe Nonequilibrium Gas and Plasma Dynamics Laboratory at the Aerospace Engineering Department of the University of Michigan is headed by Professor Iain Boyd and performs research of nonequilibrium gases and plasmas involving the development of physical models for various gas systems of interest,...
at the University of MichiganUniversity of MichiganThe University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...