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View Full Version : Plasma Engine Could Open Up Space Exploration



Fraser
2005-Dec-13, 08:59 PM
SUMMARY: The European Space Agency is developing a new thruster based on the same physics that power the northern and southern auroras. This new plasma thruster could eventually deliver more power than the efficient ion engines which have been installed on several spacecraft. ESA engineers calculate that a plasma engine could deliver several times more thrust from a similar sized ion engine, but still be as fuel efficient.

View full article (http://www.universetoday.com/am/publish/esa_new__plasma_thruster.html)
What do you think about this story? post your comments below.

Gullible Jones
2005-Dec-14, 12:33 AM
Wow, that's an interesting mechanism. Hadn't heard that about auroras before... Anyway, is there anything a bit more detailed about how the mechanism works - how the plasmas are kept apart, how and why they differ, etc.? Also, would it be possible to make a MPD thruster (http://en.wikipedia.org/wiki/Magnetoplasmadynamic_thruster) using layers of plasma, and no electrodes?

William_Thompson
2005-Dec-14, 01:15 AM
I work for EADS !!
I wonder if they are going to let us in on this since we are close cousins of the ESA.

GOURDHEAD
2005-Dec-14, 01:43 AM
Hurrah!! Looks like the drift is my direction. Plasma engines and collimated high power photon beams is the only way to go. Now to get the particle beams to work at a range of 5 light years.

IsaacKuo
2005-Dec-14, 05:30 AM
Does anyone have a link to a graphical description of how a helicon plasma thruster works? All I can tell is that it involves one or more helical RF antennas which heat the plasma and then...???

I like the concept, as well as pulsed theta-pinch thrusters, because they don't involve physical contact between the plasma and electrodes. My gut feeling is that MHDs, arcjets, and the like which have physical contact between the plasma and electrodes will be too difficult to make durable. Plasma arcs aren't friendly to metal!

Archa
2005-Dec-14, 05:36 PM
-well,Ill get to the point: if plasma charges during the passage between layers of diffirent charges,now imagine what would happen if we put it in a controlled enviroment with a generator (dinamos,etc..) in it,a generator which generates a field of variable electrical charge,-plasma charges,and again,and again,you get the picture,now if we do it in closed enviroment,we get rather nasty explosion because charged plasma has to go somwere,or trough something,now if we put an exsaust system we should get plasma powered engine,the greater the electrical field frequency,the greater power output,even if we should use it in the exsaust systems,now we all know the principles of engines,gas explodes-engine moves etc..,the similar thing should happen here (if not the same),only the results would be far better,a shuttle with that kind of engine would spend much less fuel and gain much more speed.Well that would be it,sorry for mystakes-which are plenty i presume,please if you hae any remarks,advices,suggestions or even critics,- I welcome them...
-scientia est potentia...

korjik
2005-Dec-14, 05:57 PM
IssacKuo, I'll try to see where our public web site is when I am at work tomorrow. If that dosent work I will try to post one of our descriptions on how the VASIMR works. VASIMR is a helicon thruster with an ICRH boost stage to get the 10k+ isps.

This article looks like what we were doing 2-3 years ago.

iantresman
2005-Dec-14, 07:28 PM
You can find a bit more about Double Layers, including a couple of links on the Helicon Double Layer Thruster, on the Wikipedia Double Layers page (http://en.wikipedia.org/wiki/Double_layer).

Regards,
Ian Tresman

korjik
2005-Dec-15, 07:05 PM
check here for more info on helicon thrusters

www.adastrarocket.com

Archa
2005-Dec-15, 09:30 PM
-well,Ill get to the point:
-scientia est potentia...-well I did it,I managed to make a fool aut of myself,VASIR engine explains everithing I babbled about,and I learned it too late,at least I wasnt completly wrong,well i just hope they are pretty sure with those magnetic fields,as I understaned it would be a disaster if one of them fails.
A question:what about ion engines I also read about?, What is the diffirence between VASIMIR and ion engine?

Fraser
2005-Dec-15, 09:57 PM
I just did an interview with the inventor last night. I should have the podcast live in a few days.

publiusr
2005-Dec-15, 10:25 PM
See if you can do an interview with Stan Borowski. Ask him what he thinks of electric drives and why NTR gets no love.

Contact info should be in one of these links:

http://trajectory.grc.nasa.gov/projects/ntp/index.shtml
http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/MarsRef/addendum/A5.htm

http://www.dogpile.com/info.dogpl/search/web/Stan%2BBorowski%2BNTR/1/-/1/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/107/right?&rn=57

Gullible Jones
2005-Dec-16, 12:13 AM
Nuclear thermal rocket is good, but not as efficient as VASIMR.

Of course, I'll bet you could have a dual-stage rocket... In ascent from orbit you could have the reactor put out exhaust directly, then once interplanetary you'd reduce the exhaust flow and use the reactor to power the VASIMR stage and everything else on the spacecraft...

IsaacKuo
2005-Dec-16, 01:54 AM
Okay, so correct me if I misunderstand, but this is the gist of what I get:

A VASIMR or helicon thruster essentially creates and heats up plasma sort of like a microwave oven. Then the hot plasma expands out the exhaust nozzle, in a manner similar to a thermal rocket. The difference is that instead of being constrained by a chamber/nozzle made out of solid walls, it's constrainted by magnetic field lines.

Is that basically how it works?

Gullible Jones
2005-Dec-16, 02:16 AM
Yes, and the exhaust velocity is very, very high.

wayneee
2005-Dec-16, 03:37 AM
Reaction thrusters will never get us to the stars. Might get us to Mars though, and thats pretty good. Stop thinking about the Stars and concern yourself with the solar system. We got plenty right here to keep us busy.

korjik
2005-Dec-16, 08:14 AM
Okay, so correct me if I misunderstand, but this is the gist of what I get:

A VASIMR or helicon thruster essentially creates and heats up plasma sort of like a microwave oven. Then the hot plasma expands out the exhaust nozzle, in a manner similar to a thermal rocket. The difference is that instead of being constrained by a chamber/nozzle made out of solid walls, it's constrainted by magnetic field lines.

Is that basically how it works?

Basically. the plasma dosent stay on the field lines tho. When the field drops low enough the plasma jumps the lines. Otherwise it would just wrap around and hit the front of the ship.

korjik
2005-Dec-16, 08:18 AM
-well I did it,I managed to make a fool aut of myself,VASIR engine explains everithing I babbled about,and I learned it too late,at least I wasnt completly wrong,well i just hope they are pretty sure with those magnetic fields,as I understaned it would be a disaster if one of them fails.
A question:what about ion engines I also read about?, What is the diffirence between VASIMIR and ion engine?

basically, and ion engine uses electric potentials to generate thrust. Most plasma rockets heat a magnetically confined plasma to generate thrust

iantresman
2005-Dec-16, 01:54 PM
Okay, so correct me if I misunderstand, but this is the gist of what I get:

A VASIMR or helicon thruster essentially creates and heats up plasma sort of like a microwave oven. Then the hot plasma expands out the exhaust nozzle, in a manner similar to a thermal rocket. The difference is that instead of being constrained by a chamber/nozzle made out of solid walls, it's constrainted by magnetic field lines.

Is that basically how it works?

No, that is not my understanding. The unique feature of this rocket engine is inferred by its name, a "Double layer" rocket. It is the double layer that does the work using an electric field to accelerate the ions [1 (http://en.wikipedia.org/wiki/Hall_effect_thruster)], although this also does make the plasma hotter.

This very efficient use of electric fields to accelerate plasma ions is why Hannes Alfvén made such a big deal about cosmic double layers [2 (http://en.wikipedia.org/wiki/Double_layer)], which he showed accelerates ions in the ionosphere to power the Earth's aurora, and is suggested by some as being responsible for powering solar flares [3 (http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978Ap%26SS..56...89H&db_key=AST&link_type=ABSTRACT&high=42ca922c9c28323) 4 (http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989PASAu...8...29K&db_key=AST&link_type=ABSTRACT&high=42ca922c9c28323) 5 (http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994ApJS...90..589V&db_key=AST&link_type=ABSTRACT&high=42ca922c9c28323)], and other cosmic phenomenn [6 (http://en.wikipedia.org/wiki/Double_layer)].

Regards,
Ian Tresman

ASEI
2005-Dec-16, 01:56 PM
So this is basically a more efficient version of an electrostatic engine? They've replaced the electrode meshes with some sort of suspended plasma? (Still, it's cool).

IsaacKuo
2005-Dec-16, 02:39 PM
I don't really understand how the "double layer" idea either helps or hurts a helicon or VASIMR thruster. The double layer is laid out linearly, with a hot side to the fore and a cold side to the rear, right? Thermal electrons from the hot side go toward the cold side, setting up a charge differential which accelerates the positively charged ions along for the ride, right?

I don't see how that effect adds or reduces the effectiveness of the drive. To me, it seems like the bulk effect is essentially governed by thermal expansion--it's just that thermal electrons move faster than the ions, setting up a charge gradient as a side effect.

iantresman
2005-Dec-16, 06:16 PM
I don't really understand how the "double layer" idea either helps or hurts a helicon or VASIMR thruster. The double layer is laid out linearly, with a hot side to the fore and a cold side to the rear, right? Thermal electrons from the hot side go toward the cold side, setting up a charge differential which accelerates the positively charged ions along for the ride, right?

I don't see how that effect adds or reduces the effectiveness of the drive. To me, it seems like the bulk effect is essentially governed by thermal expansion--it's just that thermal electrons move faster than the ions, setting up a charge gradient as a side effect.

That's not my understanding. If you read the Hall effect thruster (http://en.wikipedia.org/wiki/Hall_effect_thruster) page on Wikipedia, it does not even mention thermal expansion (and I read that as indicating that it is negligable!), and the article mentions that:


"One way to think of how the thruster produces thrust is to consider the Hall current electrons as a virtual negative grid at the exit plane of the thruster. The ions in the channel are pulled towards this grid and exit the channel at high velocity. The reaction force is the electrons being pulled towards the ions."

That is why Hannes Alfven said that double layers (http://en.wikipedia.org/wiki/Double_layer) are so important in astronomy, why he emphasises using the term "plasma" (20th century terminology) as opposed to an "ionized gas" (19th century).

Regards,
Ian Tresman

IsaacKuo
2005-Dec-16, 06:21 PM
I'm not asking about how a Hall effect thruster works, but specifically about helicon thrusters and VASIMR.

iantresman
2005-Dec-16, 07:41 PM
I'm not asking about how a Hall effect thruster works, but specifically about helicon thrusters and VASIMR.

Does this Helicon Double Layer Thruster study (http://www.esa.int/gsp/ACT/propulsion/helicon_double_layer.htm) page have the information you are looking for?

Regards,
Ian Tresman

IsaacKuo
2005-Dec-16, 08:26 PM
I had read that before, when I was trying to understand how helicon thrusters work. It confused me. It says ions are accelerated by an electrostatic potential difference, but it also says that it accelerates equal amounts of electrons and positive ions. The same electrostatic potential difference which would help pull along positive ions hurts pushes away electrons.

But now I understand, I think. The actual source of the thrust is essentially thermal expansion. The electrostatic potential difference is simply a side effect of the fact that thermal electrons expand away from the hot plasma faster than the heavier ions.

Imagine a bunch of ping-pong balls attached to heavy ball bearings by stretchy springs. You accelerate them with a strong wind. The ping-pong balls get blown away by the wind, and indirectly drag along the ball bearings by the stretchy springs. The strong wind is like the thermal energy of the plasma. The ping-pong balls are the lightweight electrons. The ball bearings are the heavy ions. And the stretchy springs is electrostatic force.

Now, you COULD describe what's happening in terms of the stretchy springs. You could say that it's the stretchy springs that accelerate the ball bearings, ignoring the fact that those same springs want to accelerate the ping-pong balls the other way by the exact same amount. But I think that's just confusing things, and ignoring the real thing providing the motion.

korjik
2005-Dec-17, 08:25 AM
Most helicon thrusters dont use the double layer much, That is why the article that started this thread is new.

VASIMR dosent use the double layer. We do see it when we are running at low density and power, but it gets washed out at higher power.

For VASIMR the helicon source is essentally only thermal. When running helicon only we heat the plasma with the helicon and then the plasma goes out the magnetic nozzle.

I do wonder what they are doing in the picture in the article. That plasma looks alot more like He than Ar

Archa
2005-Dec-17, 05:28 PM
Well,I just learned basicly everything I wanted to know about ion and VASIMIR engines,now,does anyone know how did the testing end for VASIMIR engine,I read it was a pass,but what next? Did anyone said something about installing the engine on a shuttle or a sattelite,whats the next step in all this aniway??

Gullible Jones
2005-Dec-17, 05:41 PM
I had read that before, when I was trying to understand how helicon thrusters work. It confused me. It says ions are accelerated by an electrostatic potential difference, but it also says that it accelerates equal amounts of electrons and positive ions. The same electrostatic potential difference which would help pull along positive ions hurts pushes away electrons.

Wake-field acceleration?

jkmccrann
2005-Dec-18, 12:38 PM
Very interesting development, one of which kinda relates back to the issue I raised in Rockets around the Solar System thread. I hope the reasearch into this area continues apace.

iantresman
2006-Jan-12, 12:43 PM
But now I understand, I think. The actual source of the thrust is essentially thermal expansion. The electrostatic potential difference is simply a side effect of the fact that thermal electrons expand away from the hot plasma faster than the heavier ions.

I just emailed Professor Rod Boswell who is mentioned in the contact details on the Helicon Double Layer Thruster Development (http://prl.anu.edu.au/020research/130SP3/020research/HDLT/index_html/view) Web page:

Ian Tresman wrote (12 Jan 2006):

I read with interest about the Helicon Double Layer Thruster, and have a question.

Does the thrust come from (a) the double layers accelerating the ions (b) the plasma being heated and expanding out of the nozzle (c) Or both, and if so, what proportion of each?

Rod Boswell replies (12 Jan 2006):

The thrust comes from the ions being accelerated by the electric field of the double layer. You can think of a marble rolling down an incline that is supported on a wheeled trolley. As the marble goes down in one direction, the trolley moves in the other direction.

Regards,
Ian Tresman

IsaacKuo
2006-Jan-12, 02:02 PM
Ok, so I'm confused again. What is the marble and what is the trolley? And why is the double-layer set up to "point" in one direction instead of the opposite direction?

And most particularly, are the marbles positively charged or negatively charged? In either case, how come the exhaust is neutrally charged?

It doesn't make any sense, to me.

iantresman
2006-Jan-12, 08:07 PM
My understanding is the a double layer will accelerate ligher electrons in one direction, and heavier ions in another. Equal numbers of oppositely charged ions are accelerated in opposite direction.

But because ions are at least 1836 times heavier than electrons (if the ions were protons), and because of equal and opposite reactions, as the heavier ions are accelerated in one direction, the spacecraft engine reacts by moving in the opposite direction.

So the analogy with a marble has the spacecraft's electric field being the counterpart of gravity. And as we know, electromagnetic forces are 10^39 times more powerful than gravity. So while an ion is "falling" through the double layer, a constant force is applied push, and the engine reacts in the opposite direction.

And this is why Hannes Alfvén made such a big deal about cosmic double layers [Ref (http://en.wikipedia.org/wiki/Double_layer)].

Regards,
Ian Tresman