The electrostatic ion thruster is a kind of design for ion thrusters (a kind of highly-efficient low-thrust spacecraft propulsion running on electrical power). These designs use high voltage electrodes in order to accelerate ions with electrostatic forces. A variant of the duoplasmatron, they were initially developed by Harold R. Kaufman at NASA in the early 1960s, but they were rarely used before the late 1990s. NASA has produced practical electrostatic ion thrusters, notably the NSTAR engine that was used successfully on Deep Space 1. Hughes Aircraft Company has developed the XIPS (Xenon Ion Propulsion System) for performing station keeping on geosynchronous satellites. NASA is currently working on a 20-50 kW electrostatic ion thruster called HiPEP which will have higher efficiency, specific impulse, and lifetime than NSTAR. Aerojet has recently completed testing of a prototype NEXT ion thruster.[1] Image File history File links Image I created from scratch File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article or section does not cite its references or sources. ... A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss (or addition) of an electron. ... Electrostatics is the branch of physics that deals with the force exerted by a static (i. ... Duoplasmatron, an invention of Manfred von Ardenne, is a type of ion beam source. ... Harold R. Kaufman is an American physicist, noted for his development of ion beam thrusters for NASA during the 1950s and 60s. ... NASA logo Listen to this article · (info) This audio file was created from an article revision dated 2005-09-01, and does not reflect subsequent edits to the article. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... See also 1990s, the band The 1990s decade refers to the years from 1990 to 1999, inclusive, sometimes informally including popular culture from the very late 1980s and from 2000 and beyond. ... NSTAR is a private utility company that provides retail electricity and natural gas to customers in eastern and central Massachusetts. ... The spacecraft Deep Space 1 was launched October 24, 1998 on top of a Delta II rocket. ... Hughes logo adopted after his death Hughes developed the AIM-120 AMRAAM, one of the worlds most advanced air-to-air missiles Hughes Aircraft Company was a major defense/aerospace company founded by Howard Hughes. ... The kilowatt (symbol: kW) is a unit for measuring power, equal to one thousand watts. ... HiPEP Beam Extraction Test In 2003 NASA ground-tested a new version of their ion thruster called High Power Electric Propulsion, or HiPEP. Theory The HiPEP thruster differs from earlier ion thrusters because the xenon ions are produced using a combination of microwave and magnetic fields. ... The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit of propellant. ... Aerojet is a major rocket and missile propulsion manufacturer based primarily in Sacramento, California with divisions in Redmond, Washington, Orange, VA, Gainesville, VA, and Camden, AK. Their products include a wide range of propulsion, from main engines used on a number of NASA vehicles and ballistic missiles, down to stationkeeping...

Method of operation

1. Propellant atoms are injected into the propulsion chamber. The propellant atoms are bombarded with electrons from a hollow cathode, causing the atoms to lose electrons of their own and become ionized, thus forming positive ions. The thruster walls and grid absorb the lost electrons.
2. The positively charged ions move towards the exit of the chamber due to diffusion. Ions will leak into a plasma sheath just upstream of the positively charged grid.
3. Once ions enter the sheath they see the potential between the positive and negative grids at the exit of the chamber, they are electrostatically accelerated away from the positive grid and towards the negative one.
4. The positive grid is at a much higher potential than the negative grid, thus the negative grid pulls on the positive ions. As the ions approach the negative grid they are electrostatically focused through the apertures of the negative grid and out into space at a high speed.
5. The expelled ions propel the ship in the opposite direction according to Newton's 3rd law.
6. Electrons are shot from a cathode, called the neutralizer, towards the ions behind the ship to ensure that equal amounts of positive and negative charge are ejected. Neutralizing is needed to prevent the ship from gaining a net negative charge.

Electron gun from a cathode ray tube An electron gun is a component that produces an electron stream that has a precise kinetic energy, being used in all TVs and monitors which use cathode ray tube technology, and in other instruments, eg. ... In the article vector quantities are written in bold whereas scalar ones are in italics. ...

Performance

The ion optics are constantly bombarded by propellant ions and erode or wear away, thus reducing engine efficiency and life. Ion engines need to be able to run efficiently and continuously for years. Several techniques were used to reduce erosion; most notable was switching to a different propellant. Mercury or caesium atoms were used as propellants during tests in the 1960s and 1970s, but these propellants adhered to, and eroded the grids. Xenon atoms, on the other hand, are far less corrosive, and became the propellant of choice for virtually all ion thruster types. NASA has demonstrated continuous operation of NSTAR engines for over 16,000 hours (1.8 years), and test are still ongoing for double this lifetime. Electrostatic ion thrusters have also achieved a specific impulse of 30-100 kN·s/kg, better than most other ion thruster types. Electrostatic ion thrusters have accelerated ions to speeds reaching 100 km/s. General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery white Atomic mass 200. ... General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Atomic mass 132. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ... General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Atomic mass 131. ... Hours is the name of the critically acclaimed second album by Welsh rock group Funeral for a Friend. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit of propellant. ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ...

In January 2006, the European Space Agency, together with the Australian National University, have announced successful testing of an improved electrostatic ion engine that showed exhaust speeds of 210 km/s, reportedly four times higher than previously achieved, allowing for a specific impulse which is four times higher. Conventional electrostatic ion thrusters possess only two grids, one high voltage and one low voltage, which perform both the ion extraction and acceleration functions. However, when the charge differential between these grids reaches around 5 kV, some of the particles extracted from the chamber collide with the low voltage grid, eroding it and compromising the engine's longevity. This limitation is successfully bypassed when two pairs of grids are used. The first pair operates at high voltage, possessing a voltage differential of around 3 kV between them; this grid pair is responsible for extracting the charged propellant particles from the gas chamber. The second pair, operating at low voltage, provides the electrical field that accelerates the particles outwards, creating thrust. Other advantages to the new engine include a more compact design, allowing it to be scaled up to higher thrusts, and a narrower, less divergent exhaust plume of 3 degrees, which is reportedly five times narrower than previously achieved. This reduces the propellant needed to correct the orientation of the spacecraft due to of small uncertainties in the thrust vector direction. The European Space Agency (ESA), established in 1975, is an inter-governmental organisation dedicated to the exploration of space, currently with 17 member states. ... The Australian National University (ANU), is a university located in Canberra, the national capital of Australia. ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ...

Variants

The chief variable in electrostatic ion thrusters is the method of ionizing the fuel atoms. New techniques such as using microwaves to heat the fuel atoms into a plasma (thus ionizing them) are under development; the advantage of such a technique is the lack of a cathode that would wear out or erode, increasing thruster life. A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation A solar coronal mass ejection blasts plasma throughout the solar system. ...

Other designs of ion thruster have also been developed in an effort to circumvent the problems of the electrostatic ion thruster. The chief focus of attention has been the grid, since grid wear is a major limiting factor in engine lifetime.

See also

• Spacecraft propulsion
• Ion thruster
• Field Emission Electric Propulsion
• Hall effect thruster
• Magnetoplasmadynamic thruster
• Pulsed inductive thruster
• Variable specific impulse magnetoplasma rocket
• Vacuum tube

A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... This article or section does not cite its references or sources. ... Field Emission Electric Propulsion (FEEP) is an advanced electrostatic propulsion concept, a form of ion thruster, that uses liquid metal (usually either cesium or indium) as a propellant. ... 2 kW Laboratory Hall Thruster in operation at the Princeton Plasma Physics Laboratory A Hall effect thruster is a type of ion thruster in which the propellant is accelerated by an electric field in a plasma discharge with a radial magnetic field. ... Magneto-Plasmadynamic (MPD) thrusters are a form of electric Propulsion which use the Lorentz force (a force exerted on charged particles by magnetic and electrical fields in combination) to generate thrust. ... Pulsed inductive thrusters or PITs as they are commonly abbreviated are a form of spacecraft propulsion that uses perpendicular electric and magnetic fields to accelerate a propellant. ... VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ... In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ...

External links

• NSTAR ion engine
• Technologies to Improve Ion Propulsion System (PDF)
• Electric Thruster Systems (PDF)
• HiPEP
• ESA And ANU Make Space Propulsion Breakthrough