Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

GCNRevenger · 2004-05-05 17:59:32

Thats the trick, you can't without getting electrodes in close proximity to the plasma, but if you do they'll melt.

ANTIcarrot. · 2004-05-05 18:22:10

Various fusion experiments around the world have shown that high tempreature plasma can be controlled (EG: kept away from walls) by magnetic fields.

ANTIcarrot.

ERRORIST · 2004-05-05 18:51:58

So what if you cool the electrode internally with water? That would be simple.

GCNRevenger · 2004-05-05 19:53:28

But a magnetic field can't be used to impart much extra flow to the plasma, the ultimate goal. It might be used as a nozzle to slightly increase the performance due to the naturally occuring ionization at that temperature, but I have my doubts if this would be worth the weight, complexity, etc.

Errorist, not sure you are getting the kinds of energies being talked about here... the low end is in the five thousand degrees region. Water won't help to cool much against that kind of heat coming off a running nuclear thermal engine, and the water would be very heavy too, ruining the performance.

Water with any contaminant, like disolved particles from the NTR engine or leftover reactor fuel from a GCNR, would also make the water conductive that would short an accelerator plate.

ERRORIST · 2004-05-05 20:01:11

Not talking about that much water to keep it cool less than five gallons could do it if you took it elsewhere to be cooled. Also,water with Zero micromhos is non conductive.

GCNRevenger · 2004-05-05 20:27:24

So you want to recycle the coolant water through the engine do you? Well unfortunatly I can't think of any practical way to do that, because of the vast amount of heat you have to remove from the water after it has been run through the engine. Getting rid of heat in space is hard for low-molar-mass substances, even getting rid of a few hundred degrees requires huge radiators. With the kinds of thermal flux involved in a nuclear thermal rocket, the radiators, pumps, plumbing etc would be far too large and too heavy.

And it would be counter-productive too, because every watt of heat you dump overboard from radiators, is another watt of heat that doesn't go into pushing rocket fuel. In the GCNR engine, liquid hydrogen is circulated around the walls of the engine and is boiled off intentionally out the nozzle so it contributes to the thrust of the engine. If you recycle the water, this doesn't happen.

The amount of water you would need in the first place is alot more than five gallons too... you need enough to absorb millions and millions of watts of energy from the engine walls.

And it gets worse

At these super-hot temperatures, especially for the GCNR engines, the hydrogen-oxygen bonds in water will simply break... The water will disintegrate, first into hydroxyl and hydrogen radicals (which can be very corrosive/explosive) and then into hydrogen and oxygen, which when cooled outside the engine, will also explode.

Water and most simple molecules don't hold up well to these kinds of temperatures, where everything starts to break down. Chemical bonds are only so strong, even the strongest will break when heated high enough, and the hotter the engine is the better... NTR engines only become efficent at the limits of the best materials is practical, compared to these, water is a flimsy easy-to-break molecule.

Edit: Oh yes! And when you do heat up pure water, and it begins to come apart, it may become electrically conductive too.

ERRORIST · 2004-05-05 20:33:35

Then use H2.

GCNRevenger · 2004-05-05 21:06:17

Hydrogen can't block enough heat from the inside without being too thick of a layer, and you can't recycle it easily (again, mega huge radiators) to cool from the outside of the system.

ERRORIST · 2004-05-05 22:49:54

Just run the heat exchanger in the shaded side of the spacecraft it is -250 degrees below zero in the shade.

ANTIcarrot. · 2004-05-06 02:35:07

MAgnets for dummies:
If they can push hard enough to keep the plasma away from the walls they can push hard enough to accelerate it down a tube. A plasma mass driver if you will. I don't know enough math to work how well it would work, but electric anything tends to be highly efficient.

ANTIcarrot.

GCNRevenger · 2004-05-06 05:14:48

Uhhuh, a magnetic pinch system... which will require extremely rapid current changes... in the exhaust stream of a continuously running nuclear rocket engine... i'm thinking no. Plus, only a small portion of the exhaust is ionized to begin with.

Errorist, 250 degrees ain't saying much... the kinds of heat loads are fantastic, it really is a slow-motion nuclear bomb going off that you pump rocket fuel through. The radiators needed for that kind of cooling would easily weigh more than the entire wet mass of the spacecraft.

ERRORIST · 2004-05-06 07:46:46

Elecectrical current changes can be made to switch on, and of much faster than femtosecond pulses. This means an ion will never strikes the wall of the chamber or nozzel. If the ion was traveling at the speed of light the ion would travel less than 1/2 the diameter of the ion in that amout of time.

How big of an area would the radiator take up?

GCNRevenger · 2004-05-06 08:05:15

Yes you can switch very fast... but not with the extreme currnets you are talking about. And although the plasma won't touch the walls of such an engine, the rest of the exhaust that isn't, will. Thermal ionization doesn't really kick in until well above the temperatures considerd for NTR engines, so it will still melt the engine.

The size of the radiators? I don't want to even think about it. A tiny little trash-can sized 300kWt reactor, which dumps 2/3rds of which as heat, needs radiators for its helium coolant that are football field sized. I'm talking nuclear reactors with outputs in the Millions or Billions of Watts. It ain't gonna happen.

ERRORIST · 2004-05-06 08:17:21

The walls of the h2 engine can be cooled by the very fuel it uses. The engine could serve a dual purpose role to both cool as a heat exchanger, and as a drive.
Since the the shade temperature in space is-250 degrees F the heat excanger won't have to be as big as the ones on Earth since the average temperatures are around +60 degrees F.They would be on the oreder of 5 times smaller in space well within the shade area of the spacecraft.

GCNRevenger · 2004-05-06 08:48:34

But in space, unlike on Earth, there is no air to conduct heat away, which is why its hard to stay cool in space. It would multiply the size of radiators you need many times. Look at the big ones on the ISS, and thats just to keep a few hundred meters of internal volume a hundred or two degrees cool from the heat of little sunlight, some electronics and a few warm bodies.

Compare this to a running multigigawatt nuclear reactor

Using LH2 as a shield gas? The GCNR engine does this already, nothing special about that... the trouble is with the magnetic acceleration drive is that its hard to impact any force on the exhaust since it isn't very ionized, and pushing it with a magnetic field in general is hard. Hard enough that the system would weigh more than the fuel that would be saved.

ERRORIST · 2004-05-06 09:01:41

Who's talking gigawatts were talking kilowatts or a few megawatts.
I have seen magnetic fields lift frogs against gravity in mid air here on Earth inside a tube chamber. Imagine what it on do to ions in the vacuum of space.

GCNRevenger · 2004-05-06 11:40:10

Nooo i'm not talking about the energy needed to run the magnets... i'm talking the amount of heat put off by the reactor which you have to design your system to be able to cope with. Basically, there isn't much of a practical way to do this and still come out with an engine that is lighter and more efficent then the fuel weight it would save

John Creighton · 2004-05-07 22:22:04

Well anyway there is a proposed system that starts with thermal trust and then accelerates the plasma with a magnetic wave. Apparently, the exhaust speed can reach the speed of light. Of course for more thrust a lower exhaust speed can be used.

http://niac.usra.edu/files/studies/fina … Slough.pdf

Of course this link is a topic of another thread. Maybe, I should read the paper before I continue with this thread.

jpeachman787 · 2004-06-03 18:11:45

Well anyway there is a proposed system that starts with thermal trust and then accelerates the plasma with a magnetic wave. Apparently, the exhaust speed can reach the speed of light. Of course for more thrust a lower exhaust speed can be used.

How can the exhaust reach the speed of light? I was under the impression thats impossible for all but light. Do you mean, perhaps, almost the speed of light? (i.e. 99%?) I'm pretty doubtful that this engine could accelerate a plasma to that speed anyways.. the energy required would be enormous...

(After skimming through the paper)

It says it may be able to reach a specific impulse of about 1 million. So the exhaust velocity would be about 9.8 million m/s, right? That's only 3.2% of the speed of light.

Yang Liwei Rocket · 2004-06-03 19:01:25

There are always new ideas for new types of drive, China is looking at better cheaper wyas of going to space, the people at NASA had some great ideas, Russia has had many projects and Europe has some new designs

Close-up view of SMART-1's stationary plasma thruster
http://esamultimedia.esa.int/images/spc … 4_high.jpg
Engineers at ESOC, the European Space Agency's control centre in Darmstadt, Germany, sent a command to begin the firing test
Electrons attracted into the discharge chamber collide with xenon atoms from the propellant gas supply, making charged atoms (ions). Current-carrying coils, inside and outside the doughnut-shaped discharge chamber, sustain a magnetic field oriented like the spokes of a wheel. By the Hall effect, ions and electrons swerving in opposite directions in the magnetic field create an electric field. This expels the xenon ions in a propulsive jet. Other emitted electrons then neutralize the xenon, producing the blue jet.
The SEPP consists of a single ion engine fuelled by xenon gas and powered by solar energy.
Blood-red Moon

May 2004
ESA's SMART-1 spacecraft has just made its 278th orbit, in good health and with all functions performing nominally

GCNRevenger · 2004-06-04 08:47:15

Smart-1's engine is a "classic" ion engine, and a fairly small one at that.

I'm a little dubious of the really high numbers about this MHD engine too.

Palomar · 2004-07-17 07:30:04

http://www.spaceref.com/news/viewpr.htm … 594]VASIMR

*Thought this short article might be of interest.

--Cindy

Grypd · 2004-07-17 14:43:19

Vasmir

It is one of the best engines to come under the heading electric engine. It seems to be very hard wearing as unlike Ion it does not suffer wear to the Cathodes. Another useful feature is it uses Hydrogen as a fuel source not the scarce rare gases. Frankly the fact it has two thrust type settings and can be high thrust or economical are hinting that it will be the engine of choice for spacecraft until fusion can be developed. It has only one shortfall it is an energy hog and needs the power supply to be a strong one and that means Nuclear.

Vasmir will be the engine of choice for the Space tugs to be built so if you want an engine that can do just about anything.

VOTE VASMIR

GCNRevenger · 2004-07-17 23:02:27

VASIMR is a great idea... on paper...

One of the big problems is how to control the million-degree plasma created, which we still aren't very good at modeling. Making the stuff and getting it to flow smoothly out of the engine without sacrificing performance is tricky.

Then you have to keep the magnets and microwave generators cool, which will be hard with the amount of energy being pumped through them, especially if you use superconducting cryomagnets that need cryogenic temperatures.

And finally the big hurdle... power. It isn't all that practical to build a little VASIMR since it would have too low of a thrust, and a big one would consume a truely monsterous amount of energy. The Prometheous project will wind up making reactors that maybe produce one megawatt of electric power tops, and thats down the road plus the thing will be dang heavy. The JIMO probe will only generate about 100 kilowatts of electricity... its unclear if the Prometheous project will be continued beyond small 100-300kWe reactors.

A large, efficent VASIMR will need a powerful, light-weight source of electricity to keep from defeating the purpose of making a super-engine, and for that you may need multiple megawatts of power... potentially in the hundreds of MW. There are only two ways to provide this sort of energy density...

1: Create a gas-core nuclear fission reactor, a somewhat esoteric concept of increasing the specific power of a fission reactor by merging the fuel and primary coolant, permitting it to reach operating temperatures around 3000K, and using magnetohydrodynamic generators to extract electricity from the steel-melting supersonic flow of Uranium/Coolant gas. The ultrahigh operating temperatures would also make the radiator mass lower.

2: Use Fusion. It is fair to say that the VASIMR concept is really a fusion engine jerry-rigged to be run off electrical power only. Use a nuclear fusion reactor to generate the plasma instead of high-power microwaves, and use leftover electricity to operate the magnets.

---

Or, "Plan A" was originally to use a restartable NTR engine as a space tug engine by the USAF or for the "Battlestar Galactica" NASA SEI Mars ship... the USAF Timberwind project investigated the concept of a pebble-bed or rolled-sheet reactor which would be much sturdier and core damage tollerant than the old NERVA thermal rockets, and reach Isp's in the 1000sec region... and could fire multiple times.

The current NASA DRM-III plan to get to Mars, sometimes referred to as "Mars Semi-Direct," launches 40MT payloads to Mars directly using a smaller version of the SDV and a TMI stage powerd by a trio of small 15,000lbs thrust NTR engines.

Mars_B4_Moon · 2023-08-12 08:10:35

I might bump an old thread and the news might fit here for new

Pulsar Fusion forms partnership with University of Michigan for electric propulsion

https://www.spacedaily.com/reports/Puls … n_999.html

Electric propulsion, with a specific focus on Hall effect thrusters, has long been recognized as a foundational technology for space missions. Recognizing its potential, the UK Space Agency has recently announced a collaboration with the Plasma dynamics and Electric Propulsion Lab at the University of Michigan, one of the premier Hall thruster research centres worldwide.

This international endeavor is further bolstered by the inclusion of renowned Hall thruster entities such as Pulsar Fusion from the UK, Starlight Engines from the US, and the University of Southampton from the UK.

NASA has previously underscored the importance of electric propulsion, spotlighting its role for the upcoming decade, especially when it comes to high-power electric propulsion and propellants. Hall thrusters have emerged as an essential component for various spacecraft missions. These missions span from geostationary satellites to more distant interplanetary endeavors.

Hall thrusters are notably utilized in robotic rendezvous missions. Established names in the field, such as Northrop Grumman and Astroscale, have incorporated them for critical operations, including spacecraft de-orbiting. These thrusters are also pivotal in interplanetary missions, with notable examples being the Lunar Gateway Space Station and the NASA Psyche mission.

New Mars Forums

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#26 2004-05-05 17:59:32

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#27 2004-05-05 18:22:10

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#28 2004-05-05 18:51:58

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#29 2004-05-05 19:53:28

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#30 2004-05-05 20:01:11

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#31 2004-05-05 20:27:24

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#32 2004-05-05 20:33:35

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#33 2004-05-05 21:06:17

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#34 2004-05-05 22:49:54

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#35 2004-05-06 02:35:07

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#36 2004-05-06 05:14:48

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#37 2004-05-06 07:46:46

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#38 2004-05-06 08:05:15

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#39 2004-05-06 08:17:21

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#40 2004-05-06 08:48:34

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#41 2004-05-06 09:01:41

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#42 2004-05-06 11:40:10

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#43 2004-05-07 22:22:04

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#44 2004-06-03 18:11:45

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#45 2004-06-03 19:01:25

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#46 2004-06-04 08:47:15

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#47 2004-07-17 07:30:04

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#48 2004-07-17 14:43:19

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#49 2004-07-17 23:02:27

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

#50 2023-08-12 08:10:35

Re: Ionization of Gas, Ion/plasma Acceleration, plasma - Containment and plasma Channeling

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