The helicon double-layer thruster is a prototype spacecraft propulsion engine. It was created by Australian scientist
Dr Christine Charles, based on a technology invented by
Professor Rod Boswell, both of the
Australian National University
The Australian National University (ANU) is a public research university located in Canberra, the capital of Australia. Its main campus in Acton encompasses seven teaching and research colleges, in addition to several national academies and ...
.
The design has been verified by the
ESA
, owners =
, headquarters = Paris, Île-de-France, France
, coordinates =
, spaceport = Guiana Space Centre
, seal = File:ESA emblem seal.png
, seal_size = 130px
, image = Views in the Main Control Room (1205 ...
, which is participating in its development.
Theory of operation
A helicon double-layer thruster (HDLT) is a type of
plasma thruster
A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast with ion thruster engines, which generate thrust through extracting an ion current from the plasma source, which i ...
, which ejects high velocity
ionized
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
gas to provide
thrust
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
to a
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
. In this thruster design, gas is injected into a tubular chamber (the ''source tube'') with one open end.
Radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...
AC power (at
13.56 MHz in the prototype design) is coupled into a specially shaped
antenna
Antenna ( antennas or antennae) may refer to:
Science and engineering
* Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves
* Antennae Galaxies, the name of two collid ...
wrapped around the chamber. The
electromagnetic wave
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...
emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a
helicon wave in the plasma, which further heats the plasma.
The device has a roughly constant
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
in the source tube (supplied by
solenoids
upright=1.20, An illustration of a solenoid
upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
in the prototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region, and might be thought of as a kind of magnetic
nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe.
A nozzle is often a pipe or tube of varying cross sectional area, a ...
. In operation, there is a sharp boundary between the high density plasma inside the source region, and the low density plasma in the exhaust, which is associated with a sharp change in electrical potential. The plasma properties change rapidly across this boundary, which is known as a ''current-free electric
double layer''. The electrical potential is much higher inside the source region than in the exhaust, and this serves both to confine most of the electrons, and to accelerate the
ions
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
away from the source region. Enough electrons escape the source region to ensure that the plasma in the exhaust is neutral overall.
Like most ion propulsion devices, the HDLT is a low thrust, high specific impulse (Isp) thruster.
A prototype 15 cm diameter thruster, operated in low-magnetic field mode, underwent initial thrust testing in 2010, however, a more complete testing method would be necessary to properly calculate the total thrust. Currently, the final thruster prototype is undergoing tests at the space simulation facility dubbed "Wombat XL" located at the Australian National University (ANU)
Mount Stromlo Observatory
Mount Stromlo Observatory located just outside Canberra, Australia, is part of the Research School of Astronomy and Astrophysics at the Australian National University (ANU).
History
The observatory was established in 1924 as The Commonwea ...
.
The HDLT has two main advantages over most other
ion thruster
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
An ion thruster ionizes a neutral gas by extracting some electrons out of a ...
designs; first, it creates an accelerating electric field without inserting unreliable components like high voltage grids into the plasma (the only plasma-facing component is the robust plasma vessel). Secondly, a ''neutralizer'' is not needed, since there are equal numbers of electrons and (singly charged) positive ions emitted. So, with neither moving mechanical parts nor susceptibility to erosion, Dr Charles explains, 'As long as you provide the power and the propellant you can go forever.'
[
]
Applications
The primary application for this thruster design is intended for satellite station-keeping, long term LEO to GEO
Geo- is a prefix derived from the Greek word ''γη'' or ''γαια'', meaning "earth", usually in the sense of "ground or land”.
GEO or Geo may also refer to:
Arts, entertainment, and media
* ''GEO'' (magazine), a popular scientific magazine ...
orbit transfers and deep space applications. While a typical design could provide a 50-year life span, or a saving of 1000 lb (≈454 kg) of launch weight for large satellites
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...
, this type of thruster could also significantly reduce the length of interplanetary space trips. For example, a trip to Mars could be shortened to 3 months instead of the 8 to 9 months with conventional chemical rockets.
See also
* Variable Specific Impulse Magnetoplasma Rocket
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electrothermal thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionization, ionize and heat an chemically inert, inert rocket propellan ...
(VASIMR)
References
Sources
Plasma thruster tested for Mars mission
Australia Building Ion Thruster (2012)
ESA Propulsion Lab
Plasma Jar to the Stars (2014)
{{emerging technologies, topics=yes, space=yes
Spacecraft propulsion
Spacecraft components
Emerging technologies