Prototype spacecraft propulsion engine
The
helicon double-layer thruster
is a prototype
electric spacecraft propulsion
. It was created by Australian scientist
Christine Charles
, based on a technology invented by
Professor Rod Boswell
, both of the
Australian National University
.
The design has been verified by the
ESA
, which is participating in its development.
Theory of operation
[
edit
]
A helicon double-layer thruster (HDLT) is a type of
plasma thruster
, which ejects
ionized
gas at high velocity to provide
thrust
to a
spacecraft
. In this thruster design, gas is injected into a tubular chamber (the
source tube
) with one open end.
Radio frequency
AC power (at
13.56 MHz
in the prototype design) is coupled into a specially shaped
antenna
wrapped around the chamber. The
electromagnetic wave
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
in the source tube (supplied by
solenoids
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
. In operation, there is a sharp boundary between the dense plasma inside the source region, and the less dense 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
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 (high-
I
sp
) 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.
[1]
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
.
[2]
[3]
The HDLT has two main advantages over most other
ion thruster
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, Charles explains, 'As long as you provide the power and the propellant you can go forever.'
[2]
Applications
[
edit
]
The primary application for this thruster design is intended for satellite station-keeping, long-term
LEO
-to-
GEO
orbit transfers and deep-space applications. While a typical design could provide a 50-year life span,
[
citation needed
]
or a saving of 1,000 pounds (450 kg) of launch weight for large
satellites
, this type of thruster could also significantly reduce the length of interplanetary space trips.
[4]
For example, a trip to Mars could be shortened to three months instead of the eight to nine months with conventional chemical rockets.
[5]
[6]
[
failed verification
]
See also
[
edit
]
References
[
edit
]
- ^
J Ling; M D West; T Lafleur; C Charles; R W Boswell (2010). "Thrust measurements in a low-magnetic field high-density mode in the helicon double layer thruster".
Journal of Physics D: Applied Physics
.
43
(30). IOP Publishing.
Bibcode
:
2010JPhD...43D5203L
.
doi
:
10.1088/0022-3727/43/30/305203
.
- ^
a
b
"Testing ground set for plasma jar to the stars"
.
ResearchCareer
. March 11, 2014
. Retrieved
July 19,
2016
.
- ^
"Wombat puts electric rocket through its paces"
.
Stories of Australian Science
. May 16, 2014
. Retrieved
July 19,
2016
.
- ^
"HDLT Applications"
. Plasma Research Laboratory. Archived from
the original
on March 2, 2011
. Retrieved
July 19,
2016
.
- ^
Tarantola, Andrew (June 13, 2012).
"Australia Is Building a Pee-Powered Ion Thruster"
.
Gizmodo
. Retrieved
July 19,
2016
.
- ^
"How long would a trip to Mars take?"
. Retrieved
July 19,
2016
.
Sources
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Concepts
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Physical propulsion
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Chemical propulsion
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Propellants
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Power cycles
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Intake mechanisms
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Electrical propulsion
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Electromagnetic
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Electrothermal
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Other
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Nuclear propulsion
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Open system
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External power
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Related concepts
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