https://thedebrief.org/plasma-propulsio ... oration/on
Wikipedia says this (https://en.wikipedia.org/wiki/Helicon_d ... r_thruster ):The helicon double-layer thruster (HDLT) is a prototype plasma thruster propulsion system that works by injecting gas into an open-ended source tube, where radio frequency AC power produced by an antenna surrounding it electromagnetically ionizes the gas. Within this highly charged plasma, a low-frequency electromagnetic helicon wave is excited by the antenna’s electromagnetic field, further heating the plasma.
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The HDLT, which was originally based on technologies developed by Rod W. Boswell, also one of the paper’s co-authors, employs a combination of an accelerating electric field and a lack of any need for a neutralizer. These make its use advantageous as a means of plasma propulsion, although there are still issues that could limit how soon the HDLT might be implemented in actual spaceflight systems.
Oh my goodness. Double Layers!A helicon double-layer thruster (HDLT) is a type of plasma thruster, which ejects high velocity ionized gas 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 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 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.
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, Dr Charles explains, 'As long as you provide the power and the propellant you can go forever.'
Here's a good article on it by the inventors ...
And some pictures of what might result ...
https://www.researchgate.net/profile/St ... -in-an.png
https://www.assemblymag.com/ext/resourc ... 14AIA6.jpg
Now I bet the budget for this development was pitiful compared to what's spent on mainstream gnomes. Actually, I suspect this discovery only happened because Rod Boswell (the inventor) is an old school plasma physicist (i.e., got his education back in the 60s and 70s, before the Dark Matter gnomers took over the universities) and Professor Christine Charles (co-inventor and primary researcher, apparently) was his colleague and thus not under their influence.
What led to my interest is this recent paper by the inventors on it …
https://www.sciencedaily.com/releases/2 ... 101032.htm
So, once again, as in controlled fusion efforts, the solution may be to take advantage of plasma instabilities, rather than try to fight them … sort of like the universe at large evolved to do long ago. Eh?Can plasma instability in fact be the savior for magnetic nozzle plasma thrusters
Date: December 7, 2022
Summary: Magnetic nozzle plasma thrusters are thought of as the future of space travel. But one problem has hampered their development -- plasma detachment. A recent study has shown that spontaneously excited plasma waves help magnetic nozzles overcome the plasma detachment problem, a rare instance of plasma instabilities having a positive effect on engineering.
A research group has demonstrated that spontaneously excited plasma waves may be the solution to a long-associated problem with magnetic nozzle plasma thrusters, turning conventional thinking on its head.