Author Topic: Electronegative plasma thruster  (Read 4138 times)

Offline Garrett

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Electronegative plasma thruster
« on: 06/12/2010 02:48 pm »
Just doing a bit of advertising for the research work of my former colleagues  8)

http://www.lpp.fr/?Plasmas-pour-la-propulsion&lang=en

Quote
The electronegative plasma thruster PEGASES belongs to the electrostatic thruster family. The main innovation is to use both positive and negative ions for thrust. This is done by creating a high density electronegative plasma (a plasma with both positive and negative ions and electrons). A magnetic field is used to filter away the electrons, such that an electron free region is formed at the periphery of the plasma. This electron free region is called an ion-ion plasma where only positive and negative ions are present. It is in this extractor area the positive and negative ions will be accelerated to provide the thrust.

This link may also be of interest to some:
ESA accelerates towards a new space thruster (more about a double layer thruster than the electronegative thruster)

EDIT: added pdf file of the patent application for the electronegative plasma thruster
« Last Edit: 06/14/2010 08:04 am by Garrett »
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline JasonAW3

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Re: Electronegative plasma thruster
« Reply #1 on: 06/13/2010 05:30 am »
Just doing a bit of advertising for the research work of my former colleagues  8)

http://www.lpp.fr/?Plasmas-pour-la-propulsion&lang=en

Quote
The electronegative plasma thruster PEGASES belongs to the electrostatic thruster family. The main innovation is to use both positive and negative ions for thrust. This is done by creating a high density electronegative plasma (a plasma with both positive and negative ions and electrons). A magnetic field is used to filter away the electrons, such that an electron free region is formed at the periphery of the plasma. This electron free region is called an ion-ion plasma where only positive and negative ions are present. It is in this extractor area the positive and negative ions will be accelerated to provide the thrust.

Interesting.

     How long can this thruster be run at a time befor thruster erosion becomes an issue?  How long can it maintain the 102 Km/s thrust before it has to be shut down? (Overheating, static electrical buildup, etc).  How much actual thrust does this motor put out thus far?  in kilograms or pounds?

     This sounds like a promising technology, but without a bit more specifics, it's hard to judge the utility of this system.

Jason
My God!  It's full of universes!

Offline kraisee

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Re: Electronegative plasma thruster
« Reply #2 on: 06/13/2010 05:52 am »
On first blush this sounds like a fairly similar technique to that used by ELWING.

They've effectively eradicated the problem of thruster erosion with their flight systems -- which have flown on a number of payloads already.

Ross.
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Offline Garrett

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Re: Electronegative plasma thruster
« Reply #3 on: 06/14/2010 07:39 am »
Just doing a bit of advertising for the research work of my former colleagues  8)

http://www.lpp.fr/?Plasmas-pour-la-propulsion&lang=en

Quote
The electronegative plasma thruster PEGASES belongs to the electrostatic thruster family. The main innovation is to use both positive and negative ions for thrust. This is done by creating a high density electronegative plasma (a plasma with both positive and negative ions and electrons). A magnetic field is used to filter away the electrons, such that an electron free region is formed at the periphery of the plasma. This electron free region is called an ion-ion plasma where only positive and negative ions are present. It is in this extractor area the positive and negative ions will be accelerated to provide the thrust.

Interesting.

     How long can this thruster be run at a time befor thruster erosion becomes an issue?  How long can it maintain the 102 Km/s thrust before it has to be shut down? (Overheating, static electrical buildup, etc).  How much actual thrust does this motor put out thus far?  in kilograms or pounds?

     This sounds like a promising technology, but without a bit more specifics, it's hard to judge the utility of this system.

Jason
This thruster concept is in the absolute early stages of development. At the moment it's a lab experiment being run by two researchers and one Ph.D. student. There may be a post-doc on the team also. No thrust measurements have been performed yet as far as I know. The 102 km/s figure is for electric thrusters in general, probably a gridded ion thruster or a Hall thruster.
It really is an advanced concept, with many years of research yet to be performed before it's known if it is truly a viable thruster option.

Cheers
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline Garrett

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Re: Electronegative plasma thruster
« Reply #4 on: 06/14/2010 07:50 am »
On first blush this sounds like a fairly similar technique to that used by ELWING.

They've effectively eradicated the problem of thruster erosion with their flight systems -- which have flown on a number of payloads already.

Ross.
The double-layer thruster quoted in the ESA article may have some similarities with that of the Elwing company.

However, the electronegative plasma thruster is NOT a grid free thruster, as is the case with the Elwing, double-layer and Hall effect thrusters. The principal advantage of the electronegative thruster is that it should not require an electron gun to neutralise the plasma plume (positive ion stream) leaving the engine, which is the case for the other thrusters.

It is hoped to accomplish this by producing alternate plumes of negative ions and positive ions (of xenon or iodine (I2) for example), which provide the thrust and then neutralise one another.

EDIT: modified the first post of this thread to include a pdf file of the patent application for the electronegative plasma thruster
EDIT 2: struck out xenon as a possible propellant. Xenon does not produce negative ions! Silly mistake on my part!
« Last Edit: 06/15/2010 08:00 am by Garrett »
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline JasonAW3

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Re: Electronegative plasma thruster
« Reply #5 on: 06/15/2010 02:56 am »
Just doing a bit of advertising for the research work of my former colleagues  8)

http://www.lpp.fr/?Plasmas-pour-la-propulsion&lang=en

Quote
The electronegative plasma thruster PEGASES belongs to the electrostatic thruster family. The main innovation is to use both positive and negative ions for thrust. This is done by creating a high density electronegative plasma (a plasma with both positive and negative ions and electrons). A magnetic field is used to filter away the electrons, such that an electron free region is formed at the periphery of the plasma. This electron free region is called an ion-ion plasma where only positive and negative ions are present. It is in this extractor area the positive and negative ions will be accelerated to provide the thrust.

Interesting.

     How long can this thruster be run at a time befor thruster erosion becomes an issue?  How long can it maintain the 102 Km/s thrust before it has to be shut down? (Overheating, static electrical buildup, etc).  How much actual thrust does this motor put out thus far?  in kilograms or pounds?

     This sounds like a promising technology, but without a bit more specifics, it's hard to judge the utility of this system.

Jason
This thruster concept is in the absolute early stages of development. At the moment it's a lab experiment being run by two researchers and one Ph.D. student. There may be a post-doc on the team also. No thrust measurements have been performed yet as far as I know. The 102 km/s figure is for electric thrusters in general, probably a gridded ion thruster or a Hall thruster.
It really is an advanced concept, with many years of research yet to be performed before it's known if it is truly a viable thruster option.

Cheers

So, no real world tests as yet?  How about at least some computer simulations?

Jason
My God!  It's full of universes!

Offline Garrett

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Re: Electronegative plasma thruster
« Reply #6 on: 06/15/2010 08:31 am »
So, no real world tests as yet?  How about at least some computer simulations?

Jason
My friend's Ph.D. thesis on the project nicely summarizes most of the work that has been done so far (theoretical and experimental). It can be downloaded in PDF at the following address:
http://pastel.paristech.org/5935/

The thesis is in English, except for the title page.
« Last Edit: 06/15/2010 08:32 am by Garrett »
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline Garrett

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Re: Electronegative plasma thruster
« Reply #7 on: 12/13/2011 08:20 am »
An article has been published in the magazine Europhysics News with some details on this thruster concept:

Space Exploration Technologies Pegases - A new promising electric propulsion concept
http://www.europhysicsnews.org/articles/epn/abs/2011/06/epn2011426p28/epn2011426p28.html

The full article is downloadable for free as a PDF from that website, but to save you time I've included it here as an attachment.
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline StephM

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Re: Electronegative plasma thruster
« Reply #8 on: 12/14/2011 04:12 pm »
Hi Guys.

Nice to see some people are interested in the PEGASES thruste concept.
Just a few comments:
- the thrust and thrust efficiency have not been assessed yet (we plan to do that next year),
- PEGASES, like the australian double-layer thruster is a cathode-free device. That's not the only advantage. Due to the fast recombination of positive and negative ions behind the grid system, the plasma density in the plume is low. That means less charged-particle in the spacecraft environment.
- the Elwing company thruster relies on the ponderomotive force. Contrary to what was mentioned on this site this thruster has never been mounted onto a spacecraft. I even don't know if there is currently a lab model.

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