Author Topic: VASIMR Engine  (Read 155315 times)

Offline QuantumG

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Re: VASIMR Engine
« Reply #120 on: 12/28/2014 06:22 AM »
Huh ?

The purpose of the ISS experiment is to demonstrate plasma separation.

I really do feel like this thread is an experiment in patience detachment. Why is this so hard to understand?
« Last Edit: 12/28/2014 06:24 AM by QuantumG »
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Offline savuporo

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Re: VASIMR Engine
« Reply #121 on: 12/28/2014 06:28 AM »
Huh ?

The purpose of the ISS experiment is to demonstrate plasma separation.

I'm not sure where you are referencing this from. Cite ?

I'll provide another, earlier one from 2013
http://www.adastrarocket.com/AdAstraRelease02Feb2013.pdf
Quote
While theoretically predicted years ago, observation of plasma detachment from the VASIMR® magnetic nozzle has been difficult to measure in the laboratory due to physical constraints in the configuration and parameter range of previous experiments, as well as the vacuum chamber volume and vacuum level in which they were conducted. However, the unique conditions of the VX-200 device and Ad  Astra’s large vacuum facility and pumping capacity have made these investigations possible for the first time. These experiments are expected to continue. However the full
relevance of research on plasma flow in magnetic nozzles will be enabled by Astra’s planned VF-200 experiment on the International Space Station where the absence of chamber walls and virtually infinite vacuum will allow investigators to probe the full parameter space for these systems.


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Offline QuantumG

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Re: VASIMR Engine
« Reply #122 on: 12/28/2014 06:31 AM »
Read what you just cited. I don't know what you're disagreeing about.
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Offline guckyfan

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Re: VASIMR Engine
« Reply #123 on: 12/28/2014 06:33 AM »
ISS happens to be the only suitable idea with sufficient power generation available for a meaningful TRL 7ish demo.

I am not sure this is true. Getting any experiment on the ISS is a long term project and it is expensive. I think building a standalone experiment might be much cheaper and simpler. Put those batteries on and you can run it with standard COM-Sat solar panels. It may be though that it is easier to get funding for the ISS-project even if it is much more expensive. Otherwise it should not go to the ISS unless it is at least potentially useful for ISS operations.

Offline savuporo

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Re: VASIMR Engine
« Reply #124 on: 12/28/2014 06:43 AM »
Read what you just cited. I don't know what you're disagreeing about.
That's the point of the test. To demonstrate exhaust separation. ..

We've been through this. They haven't demonstrated exhaust separation. It doesn't produce thrust. After 37 years, that's pretty impressive!

The purpose of the ISS experiment is to demonstrate plasma separation.

As per this paper http://www.adastrarocket.com/CSOlsen%20IEPC13%202.2.pdf
An Experimental Study of Plasma Detachment from a Magnetic Nozzle in the Plume of the VASIMR® Engine
Co-authored by 11 people, 3 of them not from Ad Astra , which was presented on resented at the
33rd International Electric Propulsion Conference
, exhaust separation has been demonstrated - or the paper, the team and results presented are one hell of expensive scientific fraud.

The ISS demo is of course still required to prove the engineering of it in actual operating conditions and advance the scientific understanding with extended data and measurements, not for first-ever plasma plume separation test.

Sir, i think you are wrong.
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Offline savuporo

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Re: VASIMR Engine
« Reply #125 on: 12/28/2014 06:48 AM »
ISS happens to be the only suitable idea with sufficient power generation available for a meaningful TRL 7ish demo.
I am not sure this is true. Getting any experiment on the ISS is a long term project and it is expensive. I think building a standalone experiment might be much cheaper and simpler. Put those batteries on and you can run it with standard COM-Sat solar panels. It may be though that it is easier to get funding for the ISS-project even if it is much more expensive. Otherwise it should not go to the ISS unless it is at least potentially useful for ISS operations.
ISS is considered suitable for launching cubesats, for crying out loud. I think that kills your argument right there.
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Offline QuantumG

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Re: VASIMR Engine
« Reply #126 on: 12/28/2014 06:55 AM »
Sir, i think you are wrong.

I think you're right. That paper certainly does indicate they've done significantly more ground testing than they previously planned on doing. Thanks.
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Offline guckyfan

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Re: VASIMR Engine
« Reply #127 on: 12/28/2014 07:21 AM »
ISS happens to be the only suitable idea with sufficient power generation available for a meaningful TRL 7ish demo.
I am not sure this is true. Getting any experiment on the ISS is a long term project and it is expensive. I think building a standalone experiment might be much cheaper and simpler. Put those batteries on and you can run it with standard COM-Sat solar panels. It may be though that it is easier to get funding for the ISS-project even if it is much more expensive. Otherwise it should not go to the ISS unless it is at least potentially useful for ISS operations.
ISS is considered suitable for launching cubesats, for crying out loud. I think that kills your argument right there.

I don't think the two are comparable. Throwing a number of cubesats out of the window airlock is not the same as installing some major experiment with demand on ISS power and influence on ISS trajectory are comparable at all.

This said. I am not arguing it is so but putting up the idea a separate experiment would be better and cheaper except for the possibility it may be easier to get funding for an ISS project.


Offline savuporo

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Re: VASIMR Engine
« Reply #128 on: 12/28/2014 07:56 AM »
I don't think the two are comparable. Throwing a number of cubesats out of the window airlock is not the same as installing some major experiment with demand on ISS power and influence on ISS trajectory are comparable at all.

This said. I am not arguing it is so but putting up the idea a separate experiment would be better and cheaper except for the possibility it may be easier to get funding for an ISS project.
There are a few possible problems with free-flyer ( although i have not really read too much about how they are planning to test on ISS ) : you need a full independent spacecraft, with comms, tracking, attitude control. Otherwise propulsion testing will be impossible or useless. A significant investment even if it is possible to get "off the shelf" comsat bus. And then you still need meaningfully large power generation capacity, oversized arrays.

Second, ISS enables manned or telerobotic assembly, deployment, instrumentation and inspection  of the experiment, to study long term effects on the components, do possible tweaks and configuration changes as well. Recovering key components for follow-on earths-side study is possible.
On a free flyer, you have to design and build this in, increasing cost, complexity, non-mission related risks. Imagine for example, for the sake of science, you want to stick some sensors out on a deployed boom 10m from the engine nozzle to study the plume. Build a self-deploying boom just to do that ? And if you do, it would really suck if you actually get to the launch pad, survive the launch and then your solar panels didnt deploy ..

With ISS, you just fly your experiment up, with minimal, if any supporting equipment. On a free-flyer, you need to ship a full spacecraft, PLUS any and all support equipment that you may think of for your experiment.

ISS is a National Lab, why not use it ? Actually i cant think of a better use for ISS than to actually test future space technologies ( MISSE and DEXTRE are my all time favorites )
« Last Edit: 12/28/2014 07:57 AM by savuporo »
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Offline Raj2014

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Re: VASIMR Engine
« Reply #129 on: 12/28/2014 01:20 PM »
VASIMR or this ? http://arc.aiaa.org/doi/abs/10.2514/1.B35250 ( published 2014 )


We had a thread on this, there is a previous publication and some previous coverage too

http://www.nasa.gov/centers/langley/news/researchernews/rn_ColloquiumWinterberg.html


EDIT: while i was trawling AIAA of 2014 anyway, i came across VASIMR paper ( of course ) too , here
http://arc.aiaa.org/doi/abs/10.2514/6.2014-4173
Full version : http://www.adastrarocket.com/Jared-Space2014.pdf

Quote
Detailed mapping of the plasma plume has been accomplished at a power level of 100 kW in a volume extending more than 2 m  downstream of the exhaust exit, without significant neutral background interaction. This has led to a compelling demonstration of how the plasma effectively flows away from the magnetic nozzle of a VASIMR® type device.(4)

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6823704
Quote
Understanding the physics involved in plasma detachment from magnetic nozzles is well theorized, but lacking in large scale experimental support. We have undertaken an experiment using the 150-m³ variable specific impulse magnetoplasma rocket test facility and VX-200 thruster seeking evidence that detachment occurs and an understanding of the physical processes involved. It was found that the plasma jet in this experiment does indeed detach from the applied magnetic nozzle (peak field ~2 T) in a two part process

I am not a plasma scientist, but IEEE and AIAA have accepted these publications.

My favorite AIAA links this year :
http://arc.aiaa.org/doi/book/10.2514/MSPOPS14 ( all free PDF access )
http://arc.aiaa.org/doi/book/10.2514/MSPACE14

This is great news, as for the free flyer, for power generation they could use DSS or ATK solar panels, which are designed to give 30kW-300 kW of electricity and are very lightweight. Quoting from what you said savuporo, "you need a full independent spacecraft, with comms, tracking, attitude control", how much would all of this cost? Do they really need a full independent spacecraft?

Offline Garrett

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Re: VASIMR Engine
« Reply #130 on: 12/28/2014 07:52 PM »
Quote
You would be thinking wrong then. Plasma "poop" is made up of charged particles. If you just shoot out positive ions then a massive electric field will form that will be strong enough to pull those ions back to the rocket, thereby cancelling all thrust. That's why ion thrusters also have electron guns, to neutralize the ions, allowing them to leave the rocket system as neutral atoms.
Vasimr doesn't use such a neutralizing mechanism. In fact, I've never quite understood how the ions were to be neutralized efficiently. That's what will define how well the ions detach and whether their blue glowy stuff has any kick to it.
In an ion drive, the electrons are pulled away from a gas to leave behind ions, which are then accelerated by an electric field. Thus leaves a net charge on the spacecraft unless those stripped-off electrons are then disposed of via the electron gun.
Not sure about other electric propulsion drives, but for Hall Effect and gridded ion thrusters the electrons emitted (usually from a hollow cathode gun) are for neutralisation of the ion beam. 

Quote
VASIMR heats a neutral gas until some of the electrons separate from their host atoms (form a plasma), but the electrons are left mixed in with the ions, and the plasma overall is electrically neutral. When it is ejected, it carries away equal amounts of positive and negative charge, so no compensation is required.
That is true at the engine nozzle exit only. But because ions and electrons have different mass, they are not magnetized to the same extent. The electrons are highly magnetized and will follow the magnetic field lines much more closely than the ions. If the ions detach from the magnetic field lines, then they will need to drag the electrons with them to ensure neutrality. I've just scanned through the recent VASIMR article linked to by savupro*, and this is exactly what they see happening. The electrons do appear to be dragged away from the magnetic field lines through some form of "anomalous transport" as they term it. They don't go easily however, and the initial detachment process forms "turbulence, created by instabilities, where a fluctuating electric field facilitates competing interactions between detached ion and magnetized electrons"

A real-world experiment in space is ultimately required to settle the argument of VASIMR thrust.

*http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6823704
« Last Edit: 12/28/2014 07:53 PM by Garrett »
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Offline savuporo

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Re: VASIMR Engine
« Reply #131 on: 12/28/2014 08:45 PM »
The electrons do appear to be dragged away from the magnetic field lines through some form of "anomalous transport" as they term it. They don't go easily however, and the initial detachment process forms "turbulence, created by instabilities, where a fluctuating electric field facilitates competing interactions between detached ion and magnetized electrons"
There are still multiple theoretical explanations to the exact underlying physics of whats happening, specifically re electron detachment, and VASIMR team is not alone studying that.

For plasma physicists here, these might be interesting to peruse :
http://pepl.engin.umich.edu/pdf/sheehan_ambipolar_ICOPS2014.pdf ( poster summarization regarding the paper above )

Theoretical studies of plasma detachment in the VASIMR magnetic nozzle, Royal Institute of Technology (KTH), Masters thesis.
http://www.diva-portal.org/smash/get/diva2:562978/FULLTEXT01.pdf
Quote
The theory is that electrons and ions detach as a pair, which gives zero parallel electric field. However the more likely scenario is that the electrons will follow the magnetic field lines to a point where  it is weaker and then follow the ions from there, not detaching as a pair. Measuring the parallel electrical field would give answer to this question.

This one from the Micro - Cathode Arc Thruster (μCAT) team.
Investigation of Magnetic Nozzle Plasma Detachment Using Scaled Down Pulsed Micro - Thruster
http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2013index/0jlm67u0.pdf
Quote
The variations in the plasma also can determine how that plasma is able to detach itself from the magnetic field of the nozzle. For instance, in order for dense plasma to escape, the ions and electrons stay together in order to maintain quasineutrality. As listed by Sankaran (2007) [3], there are several ways to address the detachment problem. Firstly, there is resistive detachment, secondly kinetic detachment, thirdly recombination detachment, fourthly non adiabatic detachment, and fifthly electron inertia detachment.
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Offline savuporo

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Re: VASIMR Engine
« Reply #132 on: 12/28/2014 09:03 PM »
And one more
http://iopscience.iop.org/0963-0252/labtalk-article/57987
Quote
Importantly, this detachment scenario applies while the plasma remains quasineutral, and does not require a net electric current to flow in the magnetic nozzle (as needed for charge conservation of the thruster). In summary, these results prove that plasma detachment is a robust phenomenon based on well-known physical principles, enabling the magnetic nozzle to generate thrust with minimal backflow – a necessary milestone toward demonstrating the applicability of these devices in space plasma propulsion.

Magnetic nozzles may be poorly understood, but i think its beyond the doubt at this point that they actually do work and detachment occurs - hence, thrust.

And an illustrative poster of the same work
http://aero.uc3m.es/ep2/docs/publicaciones/meri12cPO.pdf

**ing magnetic nozzles, how do they work??
« Last Edit: 12/28/2014 09:10 PM by savuporo »
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Offline savuporo

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Re: VASIMR Engine
« Reply #133 on: 12/30/2014 11:29 PM »
And one more, setting aside the entire "no thrust" story.

Here are the latest mass estimates for flight units:

http://spirit.as.utexas.edu/~fiso/telecon/Carter_10-29-14/Carter_10-29-14.pdf
http://www.adastrarocket.com/IEPC13-149_JPSquire_submit.pdf

It appears the the ISS-bound unit would have to be around half-ton piece at 200kW. But the key takeaway is this :
Quote
VASIMR technology has advantages over Hall when jet power exceeds ~30KW

This is based on current flight units under construction and a lot of modeling. The biggest hall effect thruster in service , BPT-4000 is about 10 times smaller ..
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Offline Raj2014

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Re: VASIMR Engine
« Reply #134 on: 12/30/2014 11:56 PM »
And one more, setting aside the entire "no thrust" story.

Here are the latest mass estimates for flight units:

http://spirit.as.utexas.edu/~fiso/telecon/Carter_10-29-14/Carter_10-29-14.pdf
http://www.adastrarocket.com/IEPC13-149_JPSquire_submit.pdf

It appears the the ISS-bound unit would have to be around half-ton piece at 200kW. But the key takeaway is this :
Quote
VASIMR technology has advantages over Hall when jet power exceeds ~30KW

This is based on current flight units under construction and a lot of modeling. The biggest hall effect thruster in service , BPT-4000 is about 10 times smaller ..

The VF-200 and Aurora was bound for ISS, apparently from what I last read about VASIMR development, due to lack of funds they can not continue. Which is disappointing as VASIMR has a lot of potential.
« Last Edit: 12/30/2014 11:56 PM by Raj2014 »

Offline MP99

Re: VASIMR Engine
« Reply #135 on: 01/01/2015 11:37 AM »


Quote
You would be thinking wrong then. Plasma "poop" is made up of charged particles. If you just shoot out positive ions then a massive electric field will form that will be strong enough to pull those ions back to the rocket, thereby cancelling all thrust. That's why ion thrusters also have electron guns, to neutralize the ions, allowing them to leave the rocket system as neutral atoms.
Vasimr doesn't use such a neutralizing mechanism. In fact, I've never quite understood how the ions were to be neutralized efficiently. That's what will define how well the ions detach and whether their blue glowy stuff has any kick to it.
In an ion drive, the electrons are pulled away from a gas to leave behind ions, which are then accelerated by an electric field. Thus leaves a net charge on the spacecraft unless those stripped-off electrons are then disposed of via the electron gun.
Not sure about other electric propulsion drives, but for Hall Effect and gridded ion thrusters the electrons emitted (usually from a hollow cathode gun) are for neutralisation of the ion beam. 

That's just another perspective on the same thing.

The spacecraft starts out electrically neutral. Without the electron gun, the spacecraft would become more negative (and the ion beam is positive, of course).

While the electron beam may neutralise the ion beam, it also neutralises the spacecraft.


Quote
VASIMR heats a neutral gas until some of the electrons separate from their host atoms (form a plasma), but the electrons are left mixed in with the ions, and the plasma overall is electrically neutral. When it is ejected, it carries away equal amounts of positive and negative charge, so no compensation is required.
That is true at the engine nozzle exit only. But because ions and electrons have different mass, they are not magnetized to the same extent. The electrons are highly magnetized and will follow the magnetic field lines much more closely than the ions. If the ions detach from the magnetic field lines, then they will need to drag the electrons with them to ensure neutrality. I've just scanned through the recent VASIMR article linked to by savupro*, and this is exactly what they see happening. The electrons do appear to be dragged away from the magnetic field lines through some form of "anomalous transport" as they term it. They don't go easily however, and the initial detachment process forms "turbulence, created by instabilities, where a fluctuating electric field facilitates competing interactions between detached ion and magnetized electrons"

A real-world experiment in space is ultimately required to settle the argument of VASIMR thrust.

*http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6823704

ISTR Hayabusa (??) had component failures in its thrusters, and was only able to continue by operating the electron gun on a different thruster than was generating thrust.

ISTM the important metric is the complexity of the systems, and lifetime of the components. VASIMR makes some claims in this area (eg exposed grids), but it's not like two VASIMR engines could share the helicon of one with the heater of another.

I guess it will come down to real world reliability, if VASIMR ever reaches spaceflight.

Cheers, Martin

Online Stormbringer

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Re: VASIMR Engine
« Reply #136 on: 01/01/2015 12:58 PM »
And one more
http://iopscience.iop.org/0963-0252/labtalk-article/57987
Quote
Importantly, this detachment scenario applies while the plasma remains quasineutral, and does not require a net electric current to flow in the magnetic nozzle (as needed for charge conservation of the thruster). In summary, these results prove that plasma detachment is a robust phenomenon based on well-known physical principles, enabling the magnetic nozzle to generate thrust with minimal backflow – a necessary milestone toward demonstrating the applicability of these devices in space plasma propulsion.

Magnetic nozzles may be poorly understood, but i think its beyond the doubt at this point that they actually do work and detachment occurs - hence, thrust.

And an illustrative poster of the same work
http://aero.uc3m.es/ep2/docs/publicaciones/meri12cPO.pdf

**ing magnetic nozzles, how do they work??

Article on magnetic Nozzle optimization using CERN GEANT Software:

http://www.technologyreview.com/view/427923/antimatter-propulsion-engine-redesigned-using-cerns-particle-physics-simulation-toolkit/

Summary:  80 percent efficiency is achievable which translates to EV of 70 percent C for Antimatter. However this same sort of nozzle optimization should logically apply to any propulsion scheme involving plasma or charged particles in any way.


a review paper on magnetic nozzle physics including plasma separation fundamentals:

http://www.umich.edu/~peplweb/pdf/AIAA-2012-4274.pdf
« Last Edit: 01/01/2015 01:24 PM by Stormbringer »
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Offline ThereIWas3

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Re: VASIMR Engine
« Reply #137 on: 01/08/2015 05:46 PM »
ISTR Hayabusa (??) had component failures in its thrusters, and was only able to continue by operating the electron gun on a different thruster than was generating thrust.

I was watching the "Hayabusa" movie just last week, and you are right.  They called the electron guns "neutralizers".
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Online Stormbringer

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Re: VASIMR Engine
« Reply #138 on: 01/15/2015 02:56 AM »
plasma detachement and other stuff:

http://www.adastrarocket.com/Jared-Space2014.pdf
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Offline Moe Grills

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Re: VASIMR Engine
« Reply #139 on: 01/21/2015 05:00 PM »
  Let's clear this up, once and for all: do the latest concerns or criticisms of the VASIMR mean it is no longer a valid propulsion alternative?
1) is it going to work, or is it not?
2) ignoring power demands (nuclear, solar, fusion) will VASIMR be able to propel a manned spacecraft to Mars in record time or not?
Please answer using the KISS method.

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