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13 December 2005
ESA has confirmed the principle of a new space thruster that may ultimately give much more thrust than today’s electric propulsion techniques. The concept is an ingenious one, inspired by the northern and southern aurorae, the glows in the sky that signal increased solar activity.“Essentially the concept exploits a natural phenomenon we see taking place in space,” says Dr Roger Walker of ESA’s Advanced Concepts Team. "When the solar wind, a ‘plasma’ of electrified gas released by the Sun, hits the magnetic field of the Earth, it creates a boundary consisting of two plasma layers. Each layer has differing electrical properties and this can accelerate some particles of the solar wind across the boundary, causing them to collide with the Earth’s atmosphere and create the aurora."
In essence, a plasma double layer is the electrostatic equivalent of a waterfall. Just as water molecules pick up energy as they fall between the two different heights, so electrically charged particles pick up energy as they travel through the layers of different electrical properties.
Researchers Christine Charles and Rod Boswell at the Australian National University in Canberra, first created plasma double layers in their laboratory in 2003 and realised their accelerating properties could enable new spacecraft thrusters. This led the group to develop a prototype called the Helicon Double Layer Thruster.
Laboratory setup of the helicon reactor at LPTP
The new ESA study, performed as part of ESA’s Ariadna academic research programme in association with Ecole Polytechnique, Paris, confirms the Australian findings by showing that under carefully controlled conditions, the double layer could be formed and remains stable, allowing the constant acceleration of charged particles in a beam. The study also confirmed that stable double layers could be created with different propellant gas mixtures.“The collaboration has been absolutely excellent,” says Dr Pascal Chabert, of Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique. “It has been a real kick-off for me and has given me lots of new ideas for plasma propulsion concepts to investigate with the Advanced Concepts Team. The new direction for our laboratory had led to a patent on a promising new electric propulsion device called an Electronegative Plasma Thruster.”
To create the double layer, Chabert and colleagues created a hollow tube around which was wound a radio antenna. Argon gas was continuously pumped into the tube and the antenna transmitted helicoidal radio waves of 13 megahertz. This ionised the argon creating a plasma. A diverging magnetic field at the end of the tube then forced the plasma leaving the pipe to expand. This allowed two different plasmas to be formed, upstream within the tube and downstream, and so the double layer was created at their boundary. This accelerated further argon plasma from the tube into a supersonic beam, creating thrust.
Image of the helicon reactor diffusion chamber during operation
Calculations suggest that a helicon double layer thruster would take up a little more space than the main electric thruster on ESA’s SMART-1 mission, yet it could potentially deliver many times more thrust at higher powers of up to 100 kW whilst giving a similar fuel efficiency.In the next steps, ESA will now construct a detailed computer simulation of the plasma in and around the thruster and use the laboratory results to verify its accuracy, so that the in-space performance can be fully assessed and larger high power experimental thrusters can be investigated in the future.
Note to editors:Plasma can be thought of as the fourth state of matter. Just as solids, liquids and gases have different properties, so too does plasma. It is a gas in which the atoms have been stripped of some of their electrons, meaning that it responds to the influence of electric and magnetic fields. It is estimated the 99% of the matter in the Universe is plasma. On Earth, however, naturally occurring plasma is rare, apart from within the layer of the atmosphere called the ionosphere.
Link to the article http://www.esa.int/esaCP/SEM6HSVLWFE_index_0.html
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I hope that this propulsion will help us on our way to Mars
ESA - European Space Agency
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It might be good for cargo ships, but it still won't do for manned craft.
It seems to be somewhere between a regular ion engine and a thermal plasma engine.
The problem isn't the engine so much as it is the power supply, you could generate quite a bit of thrust with plain old ion engines without sacrificing fuel efficiency if you had a big enough power plant, but without a really large power plant even this nifty plasma engine won't generate much thrust.
The supply of power is the limitation, if you convert every watt of power into propulsive force, you will still be limited to either low thrust or low fuel efficiency, and the engine is only capable of using the power to its fullest, it can't "find" new power that isn't there.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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It sounds like quite a positive development to me but I agree the engine is only half the problem. I am curious when it says it produces many times the trust is that per weight of the engine, per volume of the engine or per area of the engine.
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Such a plasma engine is definatly a big deal for electric-drive space probes, where the engine itself is a signifigant portion of the vehicle mass. If you can afford to build an engine, say, ten times lighter then a conventional ion engine of the same performance then this would be a big help.
It would be a modest improvement over conventional ion drive for heavy probes or cargo ships, but since the engine is a smaller fraction of the total vehicle mass here, then engine longevity might be more important. If the plasma engine is of similar durability, it might very well replace ion engines here too.
However for manned craft, you would still need a huge amount of power to really take advantage of this drive to effect travel times shorter than chemical or NTR, and the mass of that power supply is a real killer too.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Such a plasma engine is definatly a big deal for electric-drive space probes, where the engine itself is a signifigant portion of the vehicle mass. If you can afford to build an engine, say, ten times lighter then a conventional ion engine of the same performance then this would be a big help.
Which is what I belive it is inteded for. In my experience "thruster" tends to refer to low thrust engines used for staion-keeping, orbital manuvering, and the like. This thruster is likely designed to be used as a replacment for the ion/hydrazine/whatever that satilites currently use for these tasks. The terminology could use some work because technicaly any sort of engine could be called a "thruster" especialy one inteded for use in outerspace.
He who refuses to do arithmetic is doomed to talk nonsense.
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Plasma engine passes initial test
The 'double layer thruster' is a new kind of ion drive which could give much more power than existing versions. It works by accelerating charged particles between two layers of argon plasma, gas where the atoms have been stripped of electrons.
Copying a little bit of nature:
"Essentially the concept exploits a natural phenomenon we see taking place in space,"
When the solar wind, a plasma of electrified gas released by the Sun, hits the magnetic field of the Earth, it creates a boundary consisting of two plasma layers.
"Each layer has differing electrical properties, and this can accelerate some particles of the solar wind across the boundary
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I just wish I could get more folks talking NTR
More on NTR
http://trajectory.grc.nasa.gov/projects/ntp/index.shtml
http://ares.jsc.nasa.gov/HumanExplore/E … dum/A5.htm
http://www.dogpile.com/info.dogpl/searc … ght?&rn=57
Misc. links:
http://www.newscientistspace.com/articl … lites.html
http://www.geocities.com/nielspapermodels/
(Yet another) comeback?
http://www.spacewar.com/news/uav-05zzzzzzh.html
Mini-sub
http://www.beyondtomorrow.com.au/storie … arine.html
http://www.spacewar.com/news/uav-05zzzzzzh.html
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Considering the higher boil off rate, the large fuel tanks, and the mass of the engine (and its radiation shield), a practical solid-core NTR engine will need roughly 1/3 to 1/2 less fuel to get to Mars with a similar payload.
The NASA DRM-III mission plan calls for an NTR rocket stage to push the ship(s) out of Earth orbit and to Mars, which will weigh 80MT, about ~55MT of which is fuel.
The big maximal 125MT SDV heavy lifter could put a chemical powerd rocket stage, assuming 10MT savings on lighter engines and reduced boiloff, on orbit with ~95MT of fuel.
That would be enough to achieve the same mission without using nuclear engines... mind you, I think we ought to develop NTR engines anyway, since it would let us get away with the lighter no-EDS version of the heavy lifter and pave the way to advanced vapor-core reactors...
...but it could be done with chemical. It would be cheaper in the short term too, if that were a major issue.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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That suits me just fine.
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update: http://www.physorg.com/news9535.html
Technology invented by ANU physicists could see expeditions to Mars become a reality, with the European Space Agency (ESA) announcing it will begin full-scale trials next year.
Not much new stuff, other than they saying how simple it is (!)
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How simple it is is all great and stuff, but the thing preventing ion drive or any electricly driven engine from being practical for manned Mars use is and continues to be the power supply. Thanks to the rocket equation, for a given power output you can either have high thrust or or high fuel efficiency without a massive power supply... but not both. Current means of generating electricity could produce enough power for manned trips, but not without becomming so heavy that it largely counteracts the bennefits of an electric engine.
Some kind of advance, like a vapor core nuclear reactor or an ultralight solar array or at least an advanced high temperature turbine-driven solid core reactor.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Super-powerful new ion engine revealed
A new design for an ion engine promises up to 10 times the fuel-efficiency of existing electric propulsion engines, according to tests by the European Space Agency.
Tests on a prototype called the Dual-Stage 4-Grid (DS4G) thruster, at ESA’s Electric Propulsion Laboratory in the Netherlands showed that DS4G’s two-step process produces an ion exhaust plume that travelled at 210 kilometres per second – more than 10 times faster than possible with the engine in SMART-1, and four times faster than the latest prototype ion engine designs.
A 2 stage ion grid with the voltage difference between them being as great as possible.
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Which is great and all, but now you need many times the power to make this engine produce similar thrusts as DS-1 to take advantage of this fuel efficiency... and how much does this power source weigh?
Don't get me wrong, the ESA invention is a great thing, but it only solves half the problem. This will ensure that the engine is limited to space probes for the most part.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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So, a tenfold increase in ion-velocity... That's a hundredfold increase of power needed...
(that's ten squared = hundred)
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Yes something like that
In which case, does a power plant 100X the output weigh less then the fuel you save with a 10X improvement in specific impulse?
The power plant is the real killer
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Yes something like that
In which case, does a power plant 100X the output weigh less then the fuel you save with a 10X improvement in specific impulse?
The power plant is the real killer
This would depend on how far you are traveling and how quick you want to get there right?
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Yes, it depends on the total Delta-V you want. Keep in mind though, solar power output varies strongly with solar distance, so any simple calculations won't work for it.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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