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General Discussion => Advanced Concepts => Topic started by: dbooker on 05/20/2014 05:04 PM

Title: VASIMR Engine
Post by: dbooker on 05/20/2014 05:04 PM
Anyone have any info on Ad Astra's VASIMR engine and schedule?  Have the abandoned this project?  Have they run into engineering issues?  There are virtually no status updates on their web site.  Look like they are more interested in hydrogen generation and electricity generation using wind.  No updates on flight unit in years.
Title: Re: VASIMR Engine
Post by: aceshigh on 05/20/2014 05:55 PM
from Wikipedia, this seems to be the last news:

Quote
Testing on the space station[edit]
On December 8, 2008, Ad Astra signed an agreement with NASA to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station (ISS).[24] As of June 2012, its launch is anticipated to be in 2015;[25] the Antares rocket has been reported as the "top contender" for the launch vehicle.[26] Since the available power from the ISS is less than 200 kW, the ISS VASIMR will include a trickle-charged battery system allowing for 15 min pulses of thrust.

Testing of the engine on ISS is valuable because it orbits at a relatively low altitude and experiences fairly high levels of atmospheric drag, making periodic boosts of altitude necessary. Currently, altitude reboosting by chemical rockets fulfills this requirement. The VASIMR test on the ISS may lead to a capability of maintaining the ISS or a similar space station in a stable orbit at 1/20th of the approximately $210 million/year present estimated cost.[12]

Ad Astra held a formal PDR for the VF-200 with NASA on 26 June 2013


so it seems VASIMR development can only move forward after they test it on the Space Station. But that will only (luckily) happen after in 2015.
Title: Re: VASIMR Engine
Post by: Burninate on 05/21/2014 07:41 AM
I'm rather confused about why we can't run https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion or some other COTS ion thruster option.

Zubrin has in the past  (https://www.youtube.com/watch?v=myYs4DCCZts)accused VASIMR of being essentially a "Wait until advanced propulsion is ready" perennial excuse to delay a Mars mission (and contingent spending) decade after decade, when in reality the math doesn't work out at all, by several orders of magnitude, for the powersource they assume.  It is not in fact an enabling factor for a Mars mission if alpha=100, as demonstrated, instead of alpha=1.  VASIMR has failed to even keep up with competing ion thrusters on actual demonstrated tech specs, and Congress has failed to fund VASIMR at a level consistent with them caring about its immediate success.

So what stops smaller ion thrusters which don't need to be paired with a trickle-charged battery, from being used on the ISS?  Or said batteries, with a large cluster of ion thrusters?
Title: Re: VASIMR Engine
Post by: avollhar on 05/21/2014 07:53 AM
The problem with even-lower-thrust engines than VASIMR is that burn times get really long. So you are not in zero-G anymore. Which may or may not disturb some of the scientific experiments which are done in the ISS for precisely that environmental factor.
Title: Re: VASIMR Engine
Post by: Burninate on 05/21/2014 08:26 AM
1) The microgravity experiments they do are sort of a joke.  Make-work stuff that doesn't really achieve much.  The pointful part of having them up there is to further develop the engineering capacity for human spaceflight.
2) The ISS is already a very vibration-prone structure, due to the number of humans bumping around in it.
3) The need to burn to maintain altitude is and has always been present, regardless of the fact that it is an acceleration that disrupts their microgravity substantially with chemical propulsion.  So far IIRC they do tend to do 1/300th of a G burns for order 30-90 seconds.
3) VASIMR is way overpowered for the miniscule wattage ops has decided they have available to spare on the ISS, so they talk about charging up the batteries and turning them on a small fraction of the day.  The proper way to address this would likely be to fly a few more solar panels.
4) The amount of acceleration we're talking for steady-state thrust is tiny - 0.055m/s per day, about 300mN of thrust, last time I did the back-of-napkin calculations (97m per day lost at 416km altitude presently).  65 nano-G's.  Scarcely distinguishable from 0 G.
5) The acceleration is actually *currently happening*, due to drag against the outer wisps of atmosphere.  This is already a deviation from zero G.  A thruster is needed to *correct this* and lower the acceleration felt.

On page 8 of the September 2004 HiPEP report NASA/TM—2004-213194 says the pre-prototype HiPEP produced 670 mN of thrust at a power level of 39.3 kW using 7.0 mg/s of fuel giving a specific impulse of 9620 s.

If 20kW is available (IIRC VASIMR is getting 5-10), then a HiPEP derivative should be able to solve the reboost problem entirely on order 100-300kg of xenon fuel per year.
Title: Re: VASIMR Engine
Post by: Muska on 05/21/2014 08:55 AM
One question: What are the advantages of untested VASIMR engine compared to well tested array of Hall thrusters? Individual Hall thruster is of course weaker than VF-200, but they are very cheap, reliable and they can be stacked into array in parallel.

One comment: As Russians threatened to shut down ISS by 2020 by shutting down Russian chemical propulsion module. This should put some pressure to deliver adequate solar electric propulsion module into ISS. And possibly some additional solar panels in order to increase power production.
Title: Re: VASIMR Engine
Post by: Nomadd on 05/21/2014 11:14 AM
The problem with even-lower-thrust engines than VASIMR is that burn times get really long. So you are not in zero-G anymore. Which may or may not disturb some of the scientific experiments which are done in the ISS for precisely that environmental factor.
It could be just the opposite if they had the power. Low thrust engines could run continuously, just negating drag and making for a better zero-g environment.
Title: Re: VASIMR Engine
Post by: Burninate on 05/21/2014 02:41 PM
One question: What are the advantages of untested VASIMR engine compared to well tested array of Hall thrusters?

This is salient in the ISS's role as a laboratory.

Why have we been manning a laboratory for 20 years that's been running on diesel generators, with fuel refilled weekly?  Why are we hooking up an experimental micro-nuclear-reactor being tested in the lab to keep the lights on, when there's been a conventional option of hooking up to the power grid, a utility pole away?

One of the things that lent a bit of credence to the notion that this was all some kind of red herring conspiracy hoax, was when Ad Astra stated their desire to perform testing on the full-scale version on a moonbase before putting it into operation, to get a vacuum and a stable test platform.

Sidenote, I missed this before: The plans Ad Astra have for testing on the ISS involve a miniscule plane-change maneuver, 15 minutes at a time(once per day?) for 6 newtons, not actual drag-cancelling propulsion.  So long as this is their mode of operation, the ISS will require the same degree of chemical fuel for station-keeping.  As such, VASIMR and an array of more conventional ion thrusters are not mutually exclusive.

-Q&A portion of https://www.youtube.com/watch?v=-nyepvfuHho
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 05/21/2014 03:23 PM
{snip}
Sidenote, I missed this before: The plans Ad Astra have for testing on the ISS involve a miniscule plane-change maneuver, 15 minutes at a time(once per day?) for 6 newtons, not actual drag-cancelling propulsion.  So long as this is their mode of operation, the ISS will require the same degree of chemical fuel for station-keeping.  As such, VASIMR and an array of more conventional ion thrusters are not mutually exclusive.


When preparing a conspiracy theory always check money.  Ad Astra are a small company doing this with their own money.  They cannot afford a billion dollars worth of space rated solar panels needed for an all day burn.
Title: Re: VASIMR Engine
Post by: halfshallow on 05/22/2014 05:43 PM
Zubrin has in the past  (https://www.youtube.com/watch?v=myYs4DCCZts)accused VASIMR of being essentially a "Wait until advanced propulsion is ready" perennial excuse to delay a Mars mission...
Whilst Zubrin seems to endure a certain amount of criticism for his 'calm and measured manner of speech', I've never heard anyone refute the things he claims about VASIMR in the speech you linked. I think he is probably right. And I definately agree with his stance that, whilst we should be developing new (non-hoax) propulsion technology, we shouldn't be waiting for it to be developed before actually exploring space with people.
Title: Re: VASIMR Engine
Post by: bad_astra on 05/22/2014 05:49 PM
Not to go off topic, but putting people in the solar system with chemical rocket upper stages is like settling America with dugout canoes when we've got caravelles on the drawing board. VASIMIR or some other advanced technology is absolutely necessary. Can it be done with out it? Of course, but why not make the investment to do it right.
Title: Re: VASIMR Engine
Post by: Elmar Moelzer on 05/22/2014 05:51 PM
Zubrin just wants to get to mars ASAP, which would be a one shot stunt mission, too expensive to try again for another 60 years... We have done that with the moon. It put the space program on an unsustainable course. NASA is finally trying to leave that course with commercial crew, now so we should not get on it again with a one shot mars mission.
Title: Re: VASIMR Engine
Post by: cordwainer on 05/23/2014 02:23 AM
Settlement of Americas is a bad analogy. Since most of the early settlement was done by Amerind peoples long before the invention of the Caravel and some of that was done via a coastal route using dugouts. It's very possible we could do Mars exploration with a large enough chemical upper stage capable of carrying sufficient resources for long term settlement. Where advanced propulsion systems like VASIMR and MNSWR come in is to provide the capability for mass transit of materials rapidly to Mars over a wider range of launch windows and allowing for low priority supply missions via a Mars cycler.

 Heavy Lift chemical systems and near term advanced propulsion systems actually complement one another since you need those large upper stages to transport VASIMR and MSNWR liner fusion vehicles to LEO. When considering cost though chemical rockets are cheaper so using them in the meantime until other technologies are fully developed makes sense. In the past I have been critical of Mars "colonization" and Zubrin's Mars-centric views but it's hard to argue against the approach that Elon Musk is taking with his Mars Colonial Transport. With sufficient funding and investment such an approach could work. 

I would also point out that even with the current crop of advanced propulsion systems you wouldn't be able to send people on a continuous basis, you would still be limited to specific launch windows it's just that those windows would be made wider. Your Mars settlement would still have to have a great deal of self-sufficiency regardless of whether your just staying there for a few months or longer due to the limits in payload and launch windows.
Title: Re: VASIMR Engine
Post by: Vultur on 05/23/2014 05:13 AM
. VASIMIR or some other advanced technology is absolutely necessary. Can it be done with out it? Of course,

These statements are inconsistent.

I don't think there's a problem with using chemical rockets (EDIT: and just accepting long travel times) if you a) bring a solar flare shelter and b) are willing to accept a few percent (like 5% I think) increase in cancer risk decades down the road (by which point medical technology may well mean the risk is much less significant). Also, I think those risks are calculated with the linear-no-threshold model of radiation cancer risk (that's the normal 'regulatory' one) which may well be far too pessimistic.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 05/23/2014 09:50 AM
. VASIMIR or some other advanced technology is absolutely necessary. Can it be done with out it? Of course,

These statements are inconsistent.

I don't think there's a problem with using chemical rockets (EDIT: and just accepting long travel times) if you a) bring a solar flare shelter and b) are willing to accept a few percent (like 5% I think) increase in cancer risk decades down the road (by which point medical technology may well mean the risk is much less significant). Also, I think those risks are calculated with the linear-no-threshold model of radiation cancer risk (that's the normal 'regulatory' one) which may well be far too pessimistic.

And you are willing to pay the extra to launch many more tons of propellant.
Title: Re: VASIMR Engine
Post by: cordwainer on 05/26/2014 06:29 AM
Are you willing to pay the extra cost in payload for the powerplant necessary to power VASIMR? Space travel costs money, VASIMR is not about saving fuel costs it's about more efficient use of fuel to allow for greater range and continuous thrust over the vehicles flight regime.
Title: Re: VASIMR Engine
Post by: Jim on 05/27/2014 01:20 AM
1) The microgravity experiments they do are sort of a joke.  Make-work stuff that doesn't really achieve much.  The pointful part of having them up there is to further develop the engineering capacity for human spaceflight.
2) The ISS is already a very vibration-prone structure, due to the number of humans bumping around in it.


And your sources are?

And adding more solar arrays is a non starter
Title: Re: VASIMR Engine
Post by: Jim on 05/27/2014 02:48 AM

If NASA really does actually really truly want to focus on the asteroid missions for the near term, I'd love to see a VASIMR concept on the front stage with Dr. Chang Diaz organizing the whole show. 


Not going to happen, it would be a conflict of interest and also, it is not the role of the NASA administrator to perform such a role.
Title: Re: VASIMR Engine
Post by: docmordrid on 05/27/2014 05:15 AM
Wow!  Didn't Werner von Braun play that role... which is designer and administrator?

von Braun was never NASA administrator.

http://en.m.wikipedia.org/wiki/List_of_Administrators_and_Deputy_Administrators_of_NASA

but IIRC he was the first director of Marshall.

Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 05/27/2014 05:26 AM
Wow!  Didn't Werner von Braun play that role... which is designer and administrator?

von Braun was never NASA administrator.

http://en.m.wikipedia.org/wiki/List_of_Administrators_and_Deputy_Administrators_of_NASA

but IIRC he was the first director of Marshall.

Yeah, and more to the point von Braun didn't have his own outside company developing and pushing a particular technology.  That's the conflict of interest Jim was referring to.
Title: Re: VASIMR Engine
Post by: Jim on 05/27/2014 11:29 AM
Wow!  Didn't Werner von Braun play that role... which is designer and administrator?

And he
Wow!  Didn't Werner von Braun play that role... which is designer and administrator?

von Braun was never NASA administrator.

http://en.m.wikipedia.org/wiki/List_of_Administrators_and_Deputy_Administrators_of_NASA

but IIRC he was the first director of Marshall.


And he wasn't a designer as the head of Marshall.  He managed the people who were.
Title: Re: VASIMR Engine
Post by: Mecatroid on 05/29/2014 06:52 AM
Hello everybody.

Well, to answer the initial question, I would say that many people are interested in VASIMR propulsion or more generally electric based propulsion.

But, instead of VASIMR, that is not yet ready to fly (as far as I know, sorry of I'm wrong), I would rather focus on the Snecma PPS series that is really flying since september 2003 and the SMART-1 mission to the moon.

More informations here : http://www.snecma.com/IMG/files/gammeplasmiqueen_modulvoir_file_fr.pdf

The PPS-20000 seems to be very interesting to me, when compared to VASIMIR figures. Let me know your opinion ...
Title: Re: VASIMR Engine
Post by: Profwoot on 06/04/2014 09:37 PM
Hello everybody.

Well, to answer the initial question, I would say that many people are interested in VASIMR propulsion or more generally electric based propulsion.

But, instead of VASIMR, that is not yet ready to fly (as far as I know, sorry of I'm wrong), I would rather focus on the Snecma PPS series that is really flying since september 2003 and the SMART-1 mission to the moon.

More informations here : http://www.snecma.com/IMG/files/gammeplasmiqueen_modulvoir_file_fr.pdf

The PPS-20000 seems to be very interesting to me, when compared to VASIMIR figures. Let me know your opinion ...

Even the largest one has a thrust of 1N. Not sure that'll help any manned mission, especially since I don't know it would get enough power to actually run. I can't find mass figures for any but the 1350 either.
Title: Re: VASIMR Engine
Post by: manboy on 11/30/2014 10:37 PM
""We are kind of stuck," says Franklin Chang-Diaz, Ad Astra CEO and president. The company's current SAA expires in early December. Chang-Diaz says the project is unlikely to advance further without a NASA-funded SAA successor, one the company would prefer to structure like the 2005 Commercial Orbital Transportation Services initiative that spawned Falcon 9/Dragon and Orbital Sciences' Antares/Cygnus ISS resupply services."  (http://awin.aviationweek.com/portals/awin/cmsfiles/media/pdf/as_pdf/2014/06/19/asd_06_19_2014.pdf) - June 2014, Aviation Week

Apparently they need about $11 million.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 12/01/2014 12:17 AM
""We are kind of stuck," says Franklin Chang-Diaz, Ad Astra CEO and president. The company's current SAA expires in early December. Chang-Diaz says the project is unlikely to advance further without a NASA-funded SAA successor, one the company would prefer to structure like the 2005 Commercial Orbital Transportation Services initiative that spawned Falcon 9/Dragon and Orbital Sciences' Antares/Cygnus ISS resupply services."  (http://awin.aviationweek.com/portals/awin/cmsfiles/media/pdf/as_pdf/2014/06/19/asd_06_19_2014.pdf) - June 2014, Aviation Week

Apparently they need about $11 million.

So sad!  NASA is wasting billions of dollars on SLS without a mission but can't find $11 million for something that could be truly useful for BEO exploration.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/01/2014 06:51 PM
Has Franklin Chang Diaz asked other aerospace companies to test VASIMR? Does he have enough money to make a small spacecraft to test the VX-200?. If NASA can not give funding, I think Franklin should ask Elon Musk or ask other aerospace companies for funding e.g. ESA for funding or international funding.
Title: Re: VASIMR Engine
Post by: MATTBLAK on 12/01/2014 07:15 PM
""We are kind of stuck," says Franklin Chang-Diaz, Ad Astra CEO and president. The company's current SAA expires in early December. Chang-Diaz says the project is unlikely to advance further without a NASA-funded SAA successor, one the company would prefer to structure like the 2005 Commercial Orbital Transportation Services initiative that spawned Falcon 9/Dragon and Orbital Sciences' Antares/Cygnus ISS resupply services."  (http://awin.aviationweek.com/portals/awin/cmsfiles/media/pdf/as_pdf/2014/06/19/asd_06_19_2014.pdf) - June 2014, Aviation Week

Apparently they need about $11 million.

So sad!  NASA is wasting billions of dollars on SLS without a mission but can't find $11 million for something that could be truly useful for BEO exploration.


Yes, but VASIMR and similar concepts on a full operational scale - pushing around spacecraft massing tens of tons - are going to need power sources of very large scale. Solar arrays as large as ISS (or bigger) or nuclear reactors of sufficient mass have two separate problems. The solar arrays of such scale need a solid funded program to proceed - like NASA's SEP exploration concepts which are floating around in the ether at the moment and have an uncertain future. Even inactive, fairly safe nuclear reactors would fight the hardest political uphill battle to even get their funding in the first place. They will literally never get to fly. RTG/Stirling power systems might get in under the radar of public opinion. But I can't see how such systems would ever be much use for anything other than planetary surface power systems. A mixture of SEP and chemical propulsion could accomplish a lot in exploration missions.
Title: Re: VASIMR Engine
Post by: manboy on 12/01/2014 10:54 PM
The solar arrays of such scale need a solid funded program to proceed - like NASA's SEP exploration concepts which are floating around in the ether at the moment and have an uncertain future.
Hasn't DSS' Mega-ROSA and ATK's MegaFlex both received a decent amount of funding?
Title: Re: VASIMR Engine
Post by: MATTBLAK on 12/02/2014 05:15 AM
A Megaflex that produces hundreds of kilowatts of power? All the artist impressions I've seen for Exploration propulsion 'buses' are the huge, ISS blanket types.
Title: Re: VASIMR Engine
Post by: manboy on 12/02/2014 07:43 AM
A Megaflex that produces hundreds of kilowatts of power?
Both MegaFlex and Mega-ROSA teams are aiming for a +300 kW system. Mega-ROSA can allegedly be scaled to a several MW system. The ISS solar arrays apparently generate roughly 110 kW.
Title: Re: VASIMR Engine
Post by: MATTBLAK on 12/02/2014 08:22 AM
Good one! I'm learning something every day.
Title: Re: VASIMR Engine
Post by: fast on 12/02/2014 08:26 AM
A Megaflex that produces hundreds of kilowatts of power?
Both MegaFlex and Mega-ROSA teams are aiming for a +300 kW system. Mega-ROSA can allegedly be scaled to a several MW system. The ISS solar arrays apparently generate roughly 110 kW.

IIRC it was 64kW each of 4 sets. So total of about 260kW.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/02/2014 12:40 PM
A Megaflex that produces hundreds of kilowatts of power?
Both MegaFlex and Mega-ROSA teams are aiming for a +300 kW system. Mega-ROSA can allegedly be scaled to a several MW system. The ISS solar arrays apparently generate roughly 110 kW.

IMHO it was 60KW each of 4 sets

How efficient are ATK's solar arrays? The solar arrays being used in space today, are they strong enough against micrometeorites? I read that a company in Germany has developed a solar panel with an efficiency of 46%, the name of the company is called Fraunhofer ISE. Also researchers have discovered that using blu-ray disks, it can increase solar panels efficiency by 22%.     
Title: Re: VASIMR Engine
Post by: JasonAW3 on 12/02/2014 12:57 PM
Slightly off topic...

     Dumb question; Assuming similar sized liquid based solar panels, whould it be possible to heat a reaction mass fluid directly to the point of giving a thrust level similar to that of an Ion or Vasmir drive, using the same amount of fuel, without the electronic boost?
Title: Re: VASIMR Engine
Post by: IslandPlaya on 12/02/2014 06:23 PM
Thrust level? Sure, easily...
To give the same Isp? I'd say no, but am not completely sure.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 12/02/2014 06:59 PM
Slightly off topic...

     Dumb question; Assuming similar sized liquid based solar panels, whould it be possible to heat a reaction mass fluid directly to the point of giving a thrust level similar to that of an Ion or Vasmir drive, using the same amount of fuel, without the electronic boost?

For the same amount of sunlight solar thermal has a higher thrust but significantly lower Isp.  Isp is in the range 800 - 1200 seconds.
Title: Re: VASIMR Engine
Post by: IslandPlaya on 12/02/2014 08:28 PM
What I said...
Title: Re: VASIMR Engine
Post by: TrevorMonty on 12/02/2014 08:38 PM
Check out Tethers Unlimited' s  Spiderfab, for building large solar arrays in space.

Unfortunately for VASIMR the large solar arrays and power systems required to drive it are still a while away. Even when these technologies are ready there will probably not be a mission or budget for a large solar powered tug.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/02/2014 09:22 PM
Well you can power a Vasimr two ways (effectively that is.) Solar arrays which i like less that the second option. But they will work. I don't think that they really need further technical development or mechanical engineering. You can make up folding arrays of the requisite size. There have been folding solar sails designed, folding sun shields the size of tennis courts designed.  If they have to use solar arrays  they could do so.

The other way is nuclear. Either fusion of fission. Fusion may be near term (more or less) but fission is ready. GE Mitsubishi and others already have mini reactors the size of curbside garbage cans or at least the size of a large fridgerator. the tech is ready or right next to it.

VASIMR could get done. right now. But it lacks a powerful sponsor capable of cracking the whip and also buying the pieces. Dr Diaz does not have the power to do this quickly and i doubt he can buy and get approved a GE or Mitsubishi mini reactor. if not he is doing it the only way he can go about it. Slowly getting it tested and vetted on the ISS even though it has been delayed and delayed.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/02/2014 09:35 PM
You know...it's been years since i read those articles and i got the company and the dimensions wrong. But it's still small enough for launch and it produces power for 40 years before you need to do anything to it.

Here is one article on the type of reactor in general I was talking about:

http://www.wired.com/2007/12/toshibas-home-n/
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 12/03/2014 09:33 AM
Has Franklin Chang Diaz asked other aerospace companies to test VASIMR? Does he have enough money to make a small spacecraft to test the VX-200?. If NASA can not give funding, I think Franklin should ask Elon Musk or ask other aerospace companies for funding e.g. ESA for funding or international funding.

No other aerospace company is interested in funding VASIMR.  Except for SpaceX, other aerospace companies fall into one of two categories:

1. They have money to spend but take decisions based largely on making money.
2. They might be interested in spending money for reasons other than making money, but have almost no money of their own and are desperately seeking investors.

There's no money to be made from VASIMR, so category 1 companies won't spend money on it, and category 2 companies don't have any money to spend.

SpaceX is the anomaly.  But Elon's statements seem to indicate a lack of interest in VASIMR.  He seems committed to chemical propulsion for colonizing Mars.

As to the ESA or any other non-US government: they are generally only interested in spending money at home, where they can justify their existence by saying they are creating jobs.  There's no way they'd want to fund a foreign country's private company's R&D.
Title: Re: VASIMR Engine
Post by: truth is life on 12/10/2014 01:19 PM
As to the ESA or any other non-US government: they are generally only interested in spending money at home, where they can justify their existence by saying they are creating jobs.  There's no way they'd want to fund a foreign country's private company's R&D.
To be fair, they could be interested in technology transfer, but that would require moving Ad Astra to whatever country is paying for it, in essence.
Title: Re: VASIMR Engine
Post by: Star One on 12/10/2014 04:59 PM
Is there any way the technology could be varied so that it could be used in atmosphere as well as outside it?
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/10/2014 05:42 PM
if i understand it properly it's strong suite is efficiency not raw power. it cannot make it out of a gravity well.
Title: Re: VASIMR Engine
Post by: Star One on 12/10/2014 07:17 PM
if i understand it properly it's strong suite is efficiency not raw power. it cannot make it out of a gravity well.
So it couldn't be used for a purely terrestrial vehicle then. Just wondered if this was another avenue open to them.
Title: Re: VASIMR Engine
Post by: Asteroza on 12/10/2014 10:03 PM
As to the ESA or any other non-US government: they are generally only interested in spending money at home, where they can justify their existence by saying they are creating jobs.  There's no way they'd want to fund a foreign country's private company's R&D.
To be fair, they could be interested in technology transfer, but that would require moving Ad Astra to whatever country is paying for it, in essence.

That would involve ITAR and US State Department/DoD clearance to export, as it's probably (still) classified as a controlled item.
Title: Re: VASIMR Engine
Post by: truth is life on 12/10/2014 10:55 PM
That would involve ITAR and US State Department/DoD clearance to export, as it's probably (still) classified as a controlled item.

This is also true, and I can't figure out why I forgot to mention it. Logically, it wouldn't be a big deal because all of the theory is known, anyone who wants could probably develop it themselves (though it would take a while), and it's not really particularly useful for any military uses that I'm aware of, but these things rarely seem to have much to do with logic.
Title: Re: VASIMR Engine
Post by: nadreck on 12/10/2014 11:37 PM
That would involve ITAR and US State Department/DoD clearance to export, as it's probably (still) classified as a controlled item.

This is also true, and I can't figure out why I forgot to mention it. Logically, it wouldn't be a big deal because all of the theory is known, anyone who wants could probably develop it themselves (though it would take a while), and it's not really particularly useful for any military uses that I'm aware of, but these things rarely seem to have much to do with logic.
IMNSHO, especially at altitude, something like a VASIMIR engine could be weaponized
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/11/2014 12:38 AM
it's plasma so if the VASIMR can be weaponized then this is a better candidate for a pew pew type weapon:

BELLA Table Top plasma accelerator

http://www.sciencedaily.com/releases/2014/12/141208135641.htm

4.25 Giga electron volts in about 6 inches.

Title: Re: VASIMR Engine
Post by: A_M_Swallow on 12/11/2014 01:32 AM
if i understand it properly it's strong suite is efficiency not raw power. it cannot make it out of a gravity well.
So it couldn't be used for a purely terrestrial vehicle then. Just wondered if this was another avenue open to them.

No.  These sort of thrusters only work in a vacuum.
Title: Re: VASIMR Engine
Post by: Star One on 12/11/2014 06:38 AM

if i understand it properly it's strong suite is efficiency not raw power. it cannot make it out of a gravity well.
So it couldn't be used for a purely terrestrial vehicle then. Just wondered if this was another avenue open to them.

No.  These sort of thrusters only work in a vacuum.

Thank you for that clarification on the matter.
Title: Re: VASIMR Engine
Post by: rusty on 12/13/2014 08:22 AM
...
There's no money to be made from VASIMR ...
As to the ESA or any other non-US government: they are generally only interested in spending money at home, where they can justify their existence by saying they are creating jobs.  There's no way they'd want to fund a foreign country's private company's R&D.
Near-term, it's primary use would be as a lunar tug and only profitable as a separate company with a COTS-like arrangement. Since Little-O srcubbed the Moon, that's a non-option for years. Another option could be hurling asteroids toward Earth for Doomsday or scientific "prestige" reasons, but that's understandably a terrible route.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/13/2014 10:11 AM
Has Franklin Chang Diaz asked other aerospace companies to test VASIMR? Does he have enough money to make a small spacecraft to test the VX-200?. If NASA can not give funding, I think Franklin should ask Elon Musk or ask other aerospace companies for funding e.g. ESA for funding or international funding.

No other aerospace company is interested in funding VASIMR.  Except for SpaceX, other aerospace companies fall into one of two categories:

1. They have money to spend but take decisions based largely on making money.
2. They might be interested in spending money for reasons other than making money, but have almost no money of their own and are desperately seeking investors.

There's no money to be made from VASIMR, so category 1 companies won't spend money on it, and category 2 companies don't have any money to spend.

SpaceX is the anomaly.  But Elon's statements seem to indicate a lack of interest in VASIMR.  He seems committed to chemical propulsion for colonizing Mars.

As to the ESA or any other non-US government: they are generally only interested in spending money at home, where they can justify their existence by saying they are creating jobs.  There's no way they'd want to fund a foreign country's private company's R&D.

One of the ideas for VASIMR is to use it to collect space debris. They could make money this way and test the engine. Also the engine could be used for robotic probes. Other than waiting to test on the ISS, could they build a small spacecraft to test the engine in Space, to see how well it is in a real space environment. I know they have tested in a vacuum at their facility. Also NASA is going to get an increase in their budget, maybe they could give some of it to Adastra, if there is enough money.   
Title: Re: VASIMR Engine
Post by: alexterrell on 12/13/2014 04:27 PM


SpaceX is the anomaly.  But Elon's statements seem to indicate a lack of interest in VASIMR.  He seems committed to chemical propulsion for colonizing Mars.


I have a spreadsheet of numbers somewhere - but they basically showed very little benefit in using electric propulsion to get from High Earth Orbit (e.g. Earth-Moon L1) to Mars, because SEP cannot use the Oberth effect and cannot use aero-capture at Mars.

Using these effects, a minimum delta-V from HEO to Mars Aeocapture entry is only 700m/s. Getting from LEO to HEO is the major delta-V challenge (about 4km/s). A SEP could be useful here provided it can handle the Van Allen radiation environment. It could be used to lift all the mission mass to HEO, apart from crew. And it could be reusable - a genuine space tug.

I assume SpaceX reckon their launch cost will be low enough that they won't need this. Just launch from LEO and keep it simple. Zubrin would agree. VASIMR will just complicate things, even if it does reduce in orbit mass. And complexity = cost.

Two other potential benefits of SEP:
- If using to haul water from LEO to HEO, you then have lots of power to electrolyse your fuel on demand.
- If going all the way to Mars, you have a lot of power in Mars orbit. So you could look at laser beamed power for your surface operations.
Title: Re: VASIMR Engine
Post by: HailColumbia on 12/13/2014 04:35 PM


I have a spreadsheet of numbers somewhere - but they basically showed very little benefit in using electric propulsion to get from High Earth Orbit (e.g. Earth-Moon L1) to Mars, because SEP cannot use the Oberth effect and cannot use aero-capture at Mars.


Why can't you aerocapture with VASIMR?  I think you would want a small chemical engine to circularize your orbit. Doesn't areocapture mostly come down to hitting a planets atmosphere at the correct angle? Seems like VASIMR should be able to do that.
Title: Re: VASIMR Engine
Post by: Hanelyp on 12/13/2014 05:48 PM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.
Title: Re: VASIMR Engine
Post by: MP99 on 12/13/2014 07:02 PM


SpaceX is the anomaly.  But Elon's statements seem to indicate a lack of interest in VASIMR.  He seems committed to chemical propulsion for colonizing Mars.


I have a spreadsheet of numbers somewhere - but they basically showed very little benefit in using electric propulsion to get from High Earth Orbit (e.g. Earth-Moon L1) to Mars, because SEP cannot use the Oberth effect and cannot use aero-capture at Mars.

Using these effects, a minimum delta-V from HEO to Mars Aeocapture entry is only 700m/s. Getting from LEO to HEO is the major delta-V challenge (about 4km/s). A SEP could be useful here provided it can handle the Van Allen radiation environment. It could be used to lift all the mission mass to HEO, apart from crew. And it could be reusable - a genuine space tug.

Using a Weak Stability Boundary Transfer, Chemical can get you to EML2 in 3 months for ~3.2 km/s, but that's using Oberth assistance at TLI.

I think you need to recalculate the dV required for SEP to slog it's way out to EML when it can't take advantage of Oberth - I think you've under-estimated it quite a bit.

OTOH, I believe your 0.7 km/s from EML through TMI is low - you'll use about half that just leaving EML (the perigee lowering burn as you pass the Moon), so you can do an Oberth burn at earth. But the Oberth burn itself can be around 1 km/s (or some of the numbers appropriate for cargo mission do seem to be lower, as per your estimate).



I assume SpaceX reckon their launch cost will be low enough that they won't need this. Just launch from LEO and keep it simple. Zubrin would agree. VASIMR will just complicate things, even if it does reduce in orbit mass. And complexity = cost.

I agree re an "abundant chemical" architecture.

The Earth end works even better if you have a massive Mars Transfer Vehicle, do a small Oberth braking burn at LEO, then store the rest of the gravitational potential energy by positioning it at EML ready for the next mission.

It's worth mentioning for EML2 that 1-1.5 km/s of chemical burn with Oberth assist would need to be matched by at least 3-5 km/s by VASIMR in order to achieve the same interplanetary speeds.

cheers, Martin
Title: Re: VASIMR Engine
Post by: Alf Fass on 12/13/2014 10:37 PM
G. Nordley has a table for delta V's and transit times to Mars here:

http://www.gdnordley.com/_files/Going_to_Mars.html

As can be seen, chemical propulsion can get you there in ~80 days with reasonable propellant mass ratios(this was demonstrated by New Horizons on its way to Pluto, about 80 days to reach Mars orbit).

To compete with this electric propulsion would need to be faster and/or cheaper, something that I think is unlikely to happen with a fission or fusion energy source.

The Adastra VASIMR concept suggests 39 days is possible, interestingly this article, http://www.fromquarkstoquasars.com/vasimr-impulse-engine/

admits:
Quote
Currently the VASIMR engines are operating over 60% efficiency; however, we have hit a wall on how to power the unit while in space.  To achieve the amounts of power required for such a powerful engine, we would need to design some form of nuclear reactor, fusion reactor, or matter-antimatter reactor as a supply of power in space.  Theoretically, you could use large solar panels as well; however, the weight for such panels would pose an issue at launch.


Which is Why concentrating a lot of Sunlight onto a small area of cooled PV cells is necessary, solar reflectors are theoretically able to be made as light as 0.02g/m2
Quote
At a thickness of 20 nm, lithium has an areal density of 0.011 g/m2. A high-performance sail could be made of lithium alone at 20 nm (no emission layer). It would have to be fabricated in space and not used to approach the sun. In the limit, a sail craft might be constructed with a total areal density of around 0.02 g/m2, giving it a lightness number of 67 and ac of about 400 mm/s2. Magnesium and beryllium are also potential materials for high-performance sails. These 3 metals can be alloyed with each other and with aluminium.[2]
http://en.wikipedia.org/wiki/Solar_sail#Materials

Such a lightweight reflector, able to concentrate a GW(!) at an AU from the Sun might be built weighing only 20kg, I think it possible its parabolic shape could be retained at ship accelerations of up to around 0.05g by the pressure of the Sunlight and by slowly rotating of the reflector.

Title: Re: VASIMR Engine
Post by: alexterrell on 12/13/2014 10:47 PM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.
Title: Re: VASIMR Engine
Post by: HailColumbia on 12/14/2014 12:13 AM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?
Title: Re: VASIMR Engine
Post by: Alf Fass on 12/14/2014 12:20 AM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

If you're going to the trouble of using electric propulsion you need to justify it with much higher delta V's, when that happens aerocapture becomes proportionately less useful.
Title: Re: VASIMR Engine
Post by: HailColumbia on 12/14/2014 12:25 AM

If you're going to the trouble of using electric propulsion you need to justify it with much higher delta V's, when that happens aerocapture becomes proportionately less useful.

Don't you still get to spend less time decelerating regardless? Seems like aerocapture would always be the most efficient option, assuming your spacecraft is not made of aluminum foil and twine.
Title: Re: VASIMR Engine
Post by: Alf Fass on 12/14/2014 12:39 AM
To go faster your craft needs to be lighter, if we use an exhaust velocity of 100km/sec as an example, kg for kg extra propellant will get you a quicker trip than that mass in the form of PicaX (the Dragon heatshield material) assuming the power supply problems in hand.
Title: Re: VASIMR Engine
Post by: Dalhousie on 12/14/2014 01:48 AM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

And with nuclear electric getting the radiators to do the same.
Title: Re: VASIMR Engine
Post by: savuporo on 12/14/2014 03:15 AM
it bears to mention that todays practical chemical propulsion beyond earth departure burns is around 325 ISP or so. storable hyprgolics only.

so when comparing theoretical benefits of SEP vs VASIMR vs chemical, this has to be kept in mind.
Title: Re: VASIMR Engine
Post by: guckyfan on 12/14/2014 08:06 AM
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.

Title: Re: VASIMR Engine
Post by: MP99 on 12/14/2014 05:38 PM


The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.

gf,

I really should pay more attention to the posts I'm replying to. I just composed exactly that suggestion. At least I re-read your post before I submitted. With it understood that you beat me to it, I might as well post it anyway:-

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin
Title: Re: VASIMR Engine
Post by: TrevorMonty on 12/14/2014 06:43 PM


The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.

gf,

I really should pay more attention to the posts I'm replying to. I just composed exactly that suggestion. At least I re-read your post before I submitted. With it understood that you beat me to it, I might as well post it anyway:-

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin
Separating payload for aero capture makes sense.

There was a comment earlier about solar arrays designed for launch being to heavy. Technologies are in development to enable solar arrays to be built in space. See Tethers Unlimited Spider truss. In space assembly means support structures can be feather light as forces on them are <0.1g especially for SEP.
Title: Re: VASIMR Engine
Post by: TrevorMonty on 12/14/2014 07:47 PM
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.


http://www.spacefuture.com/archive/early_commercial_demonstration_of_space_solar_power_using_ultra_lightweight_arrays.shtml


Title: Re: VASIMR Engine
Post by: savuporo on 12/14/2014 07:58 PM
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.

http://cms.atk.com/SiteCollectionDocuments/ProductsAndServices/UltraFlex-2012.pdf

EDIT: in short, about 200w/kg. This has been scaled up to 8m diameter wings, called Megaflex
http://www.nasa.gov/offices/oct/home/feature_sas_prt.htm

The next step advancement can come from separating the deployment system from the actual arrays. Similar to how some terrestrial solar farms got rid of expensive per-panel tracker motors and leave it to a separate rail-running robotic device.

http://www.qbotix.com/rts/
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 12/14/2014 08:09 PM

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin

The second inspace tug could have brought cargo so it would have been discarded or returned empty.

If you are planning a series of missions then arrange to have an abort VASIMR waiting in Mars orbit.  The current tug becomes the next abort VASIMR.
Title: Re: VASIMR Engine
Post by: TrevorMonty on 12/14/2014 09:21 PM
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.

http://cms.atk.com/SiteCollectionDocuments/ProductsAndServices/UltraFlex-2012.pdf

EDIT: in short, about 200w/kg. This has been scaled up to 8m diameter wings, called Megaflex
http://www.nasa.gov/offices/oct/home/feature_sas_prt.htm

The next step advancement can come from separating the deployment system from the actual arrays. Similar to how some terrestrial solar farms got rid of expensive per-panel tracker motors and leave it to a separate rail-running robotic device.

http://www.qbotix.com/rts/
The Megaflex is designed to be compact and handle launch loads. A lot of their weight and expense is in structure plus they a limited by area efficiency (kw/m2 30%?) of solar arrays as they need to be compact.

Solar arrays that assembled in space can be less efficient by area 6-9% for rollable 4.5kw/kg example. The rolled up array ( think roll of paper) is still compact for launch as there is no structure. The idea is to add it to lightweight structure that is built in space. With in space assembly arrays of square kms is not an issue as the only load is SEP thrust. The article was quoting 1kW/kg for arrays, structure and power systems, that is 200kg for 200kw. We still a years away but not decades from in space assembly.
Title: Re: VASIMR Engine
Post by: savuporo on 12/14/2014 10:12 PM
i thought ISS was assembled in space last decade already. DEXTRE has demoed unmanned assembly and repair ops as well.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 12/14/2014 11:37 PM

The Megaflex is designed to be compact and handle launch loads. A lot of their weight and expense is in structure plus they a limited by area efficiency (kw/m2 30%?) of solar arrays as they need to be compact.

Solar arrays that assembled in space can be less efficient by area 6-9% for rollable 4.5kw/kg example. The rolled up array ( think roll of paper) is still compact for launch as there is no structure. The idea is to add it to lightweight structure that is built in space. With in space assembly arrays of square kms is not an issue as the only load is SEP thrust. The article was quoting 1kW/kg for arrays, structure and power systems, that is 200kg for 200kw. We still a years away but not decades from in space assembly.

So the biggest thrust is likely to be chemical thrusters in the RCS.  Easy to handle providing the designers are warned that the thrust is coming.
Title: Re: VASIMR Engine
Post by: L5Resident on 12/21/2014 08:07 PM
Is VASIMR still going on the station? I haven't heard much of anything recently.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 12/21/2014 09:12 PM
Is VASIMR still going on the station? I haven't heard much of anything recently.

I don't think so.

The last news we heard was the June 2014 Aviation Week article:

""We are kind of stuck," says Franklin Chang-Diaz, Ad Astra CEO and president. The company's current SAA expires in early December. Chang-Diaz says the project is unlikely to advance further without a NASA-funded SAA successor, one the company would prefer to structure like the 2005 Commercial Orbital Transportation Services initiative that spawned Falcon 9/Dragon and Orbital Sciences' Antares/Cygnus ISS resupply services."  (http://awin.aviationweek.com/portals/awin/cmsfiles/media/pdf/as_pdf/2014/06/19/asd_06_19_2014.pdf) - June 2014, Aviation Week

Apparently they need about $11 million.

This says the project needs more NASA money or it can't progress after early December.  Since we haven't heard them announcing any new money from NASA or anywhere else, the logical conclusion is that VASIMIR is dead and won't be going to the station.

It's a pity.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 10:08 PM
Dr Diaz did some crownd funding to get funds to keep the program going for a while and to produce a couple of promotional videos and develop mission plans. also the wiki still has the ISS mission but with pushed back dates.

http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket

Quote
Testing on the International Space Station

On December 8, 2008, Ad Astra signed an agreement with NASA to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station (ISS).[24] In early 2009, the earliest possible launch date was reported as 2012.[25] As of April 2014, its launch is anticipated to be in 2016.[26] The reason for the delays have been attributed to funding; and in June 2014, Franklin Chang-Diaz stated that the project is unlikely to proceed unless they're able to receive a funded-SAA from NASA.[27]
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 10:13 PM
Dr Diaz did some crownd funding

Just like Christopher Columbus!

To be fair, this has to be the longest running rocket development program - that hasn't produced anything - of all time.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/21/2014 10:35 PM
Dr Diaz did some crownd funding

Just like Christopher Columbus!

To be fair, this has to be the longest running rocket development program - that hasn't produced anything - of all time.

They have done a lot of work on the VASIMR. If you look on ad astra rocket website and youtube, you will see a lot of information and videos, which shows them testing VASIMR. VASIMR has been mentioned in a lot websites and documentaries. I hope they can raise the money they need to continue testing and hopefully it will lead to deep space travel. 
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 10:36 PM
They have done a lot of work on the VASIMR.

No doubt. What they haven't done is produce a rocket engine.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 10:52 PM
They have done a lot of work on the VASIMR.

No doubt. What they haven't done is produce a rocket engine.
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

http://upload.wikimedia.org/wikipedia/en/3/36/VX-200_operation_full_power.jpg

https://www.youtube.com/watch?v=GIg6pWwezEU
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 10:58 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

We've been through this. They haven't demonstrated exhaust separation. It doesn't produce thrust. After 37 years, that's pretty impressive!
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 10:59 PM
https://www.youtube.com/watch?v=GIg6pWwezEU
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 11:02 PM
What's your point? A rocket engine produces thrust. The VASIMR engine doesn't. My plasma cutter looks pretty impressive too but it's not a rocket engine. That's what they've produced: a plasma show.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 11:05 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

So NASA agreed to send a engine to space that produces no thrust? I don't think so. That does not sound likely.
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 11:07 PM
So NASA agreed to send a engine to space that produces no thrust? I don't think so. That does not sound likely.

That's the point of the test. To demonstrate exhaust separation. Also, NASA agreed to no such thing. Again, you're a sucker for press releases.
Title: Re: VASIMR Engine
Post by: RonM on 12/21/2014 11:20 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

I don't recall being through this. Please elaborate why you say VASIMR doesn't produce thrust and site your sources.
Title: Re: VASIMR Engine
Post by: QuantumG on 12/21/2014 11:29 PM
I don't recall being through this. Please elaborate why you say VASIMR doesn't produce thrust and site your sources.

http://forum.nasaspaceflight.com/index.php?topic=18382.msg487159#msg487159

If you want a source, how about this unfunded grant application for demonstrating plasma detachment: http://www.uh.edu/research/spg/uhdiagnostics.html

Or Ad Astra's computer simulation paper: http://www.adastrarocket.com/AndrewASS02.PDF

Quote
The described particle simulations in VASIMR
demonstrate plasma detachment from the magnetic
nozzle. Reasonable agreement between MHD and
particle simulation is observed in plasma beta
detachment analysis. The codes developed so far are
being validated in the VX-10 laboratory experiment
and assisting researchers in the design of a VASIMR
flight demonstration experiment.

There's no dispute, Ad Astra have yet to demonstrate that VASIMR produces thrust. They expect to demonstrate that on a flight mission, which hasn't been funded and for which no launch has been allocated.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 11:38 PM
I think anything that poops anything out one end (even if it's just blue glowy stuff) produces thrust. Even a rocket powered by beer is possible.

I believe the early early early VASIMR prototype produced 5 newtons at 67 percent efficiency. Now that does appear weak but its on the order of other ion engines; thrust-wise.

EDIT: Thrust was calculated at 5N. it was not tested WRT actual thrust.
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/21/2014 11:48 PM
it looks like QuantumG is *technically* correct.

http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket

Quote
One of the remaining untested issues was potential vs actual thrust; that is, whether the hot plasma actually detached from the rocket.

However; the notion that VASIMR will not work because of this seems ridiculous. i see little difference between VASIMR and countless other ion or plasma rockets.
Title: Re: VASIMR Engine
Post by: RonM on 12/22/2014 12:22 AM
I don't recall being through this. Please elaborate why you say VASIMR doesn't produce thrust and site your sources.

http://forum.nasaspaceflight.com/index.php?topic=18382.msg487159#msg487159

If you want a source, how about this unfunded grant application for demonstrating plasma detachment: http://www.uh.edu/research/spg/uhdiagnostics.html

Or Ad Astra's computer simulation paper: http://www.adastrarocket.com/AndrewASS02.PDF

Quote
The described particle simulations in VASIMR
demonstrate plasma detachment from the magnetic
nozzle. Reasonable agreement between MHD and
particle simulation is observed in plasma beta
detachment analysis. The codes developed so far are
being validated in the VX-10 laboratory experiment
and assisting researchers in the design of a VASIMR
flight demonstration experiment.

There's no dispute, Ad Astra have yet to demonstrate that VASIMR produces thrust. They expect to demonstrate that on a flight mission, which hasn't been funded and for which no launch has been allocated.

Thanks for the quick and thorough response. After looking at those links, I found a paper from January 2014.

http://w3fusion.ph.utexas.edu/ifs/ifsreports/977_Arefiev.pdf (http://w3fusion.ph.utexas.edu/ifs/ifsreports/977_Arefiev.pdf)

Looks like they are still working on it a decade after the first proposal.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 12/22/2014 02:03 AM
To spend money on something NASA has to go through complex bureaucratic processes.  This includes making announcements and issuing requests for bids.  Have a look at the small print in the NextSTEP Broad Agency announcement thread.

"Advanced Concepts
Next Space Technologies for Exploration Partnerships (NextSTEP) BROAD AGENCY

http://forum.nasaspaceflight.com/index.php?topic=36273.0 (http://forum.nasaspaceflight.com/index.php?topic=36273.0)"


Ref to NASA document
https://prod.nais.nasa.gov/eps/eps_data/163051-SOL-001-001.pdf (https://prod.nais.nasa.gov/eps/eps_data/163051-SOL-001-001.pdf)

That engine specification sounds like a VASIMR.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/23/2014 11:20 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

Here is a video showing a VASIMR  (https://www.youtube.com/watch?v=4F2Bxc5qavE)engine producing thrust.
Title: Re: VASIMR Engine
Post by: QuantumG on 12/23/2014 11:54 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

Here is a video showing a VASIMR  (https://www.youtube.com/watch?v=4F2Bxc5qavE)engine producing thrust.

No it isn't.

Go to your kitchen sink, fill it with water and swirl your hand around to create a vortex. Now stick a large flat spoon into the flow. You will feel a force, that's momentum response. To claim that your setup is producing net force would be silly, but to do it you'd need to make an argument about the detachment of the medium from the vessel. That is, you need to pull out the plug. As far as I'm aware, Ad Astra have never claimed they could demonstrate detachment of the plasma from the nozzle on the ground and have no plans to do so.
Title: Re: VASIMR Engine
Post by: momerathe on 12/24/2014 07:53 PM
As far as I'm aware, Ad Astra have never claimed they could demonstrate detachment of the plasma from the nozzle on the ground and have no plans to do so.
I don't think there's a vacuum chamber big enough.
Title: Re: VASIMR Engine
Post by: manboy on 12/24/2014 08:33 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

We've been through this. They haven't demonstrated exhaust separation. It doesn't produce thrust. After 37 years, that's pretty impressive!
Well given enough time maybe XCOR will beat that record.
Title: Re: VASIMR Engine
Post by: Garrett on 12/24/2014 09:02 PM
I think anything that poops anything out one end (even if it's just blue glowy stuff) produces thrust.
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.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/24/2014 09:12 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

Here is a video showing a VASIMR  (https://www.youtube.com/watch?v=4F2Bxc5qavE)engine producing thrust.

No it isn't.

Go to your kitchen sink, fill it with water and swirl your hand around to create a vortex. Now stick a large flat spoon into the flow. You will feel a force, that's momentum response. To claim that your setup is producing net force would be silly, but to do it you'd need to make an argument about the detachment of the medium from the vessel. That is, you need to pull out the plug. As far as I'm aware, Ad Astra have never claimed they could demonstrate detachment of the plasma from the nozzle on the ground and have no plans to do so.

You say the VASIMR does not produce thrust, yet in the video I posted, we can see the VASIMR move the Momentum/Impulse response target.
Title: Re: VASIMR Engine
Post by: QuantumG on 12/24/2014 09:20 PM
it is my understanding that the VF 200 is fully built and ground tested. what does it take other than that to "produce a rocket engine?"

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

Here is a video showing a VASIMR  (https://www.youtube.com/watch?v=4F2Bxc5qavE)engine producing thrust.

No it isn't.

Go to your kitchen sink, fill it with water and swirl your hand around to create a vortex. Now stick a large flat spoon into the flow. You will feel a force, that's momentum response. To claim that your setup is producing net force would be silly, but to do it you'd need to make an argument about the detachment of the medium from the vessel. That is, you need to pull out the plug. As far as I'm aware, Ad Astra have never claimed they could demonstrate detachment of the plasma from the nozzle on the ground and have no plans to do so.

You say the VASIMR does not produce thrust, yet in the video I posted, we can see the VASIMR move the Momentum/Impulse response target.

Which I just explained to you. I'm not sure what more I can do.
Title: Re: VASIMR Engine
Post by: Adaptation on 12/25/2014 06:14 AM
You say the VASIMR does not produce thrust, yet in the video I posted, we can see the VASIMR move the Momentum/Impulse response target.

Imagine ping pong balls attached to a board by rubber bands.  You make a fancy mechanism that will shoot them out really fast but unless you cut the rubber band they will come back and no net thrust will be produced.  Such a device could move a 'Momentum/Impulse response target' and still be useless in space.  I'm in no position to argue one way or the other but maybe it will help you understand QuantumG's take on the thing. 
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/25/2014 07:26 AM
i got what he said a few posts ago but your illustration is simple and clear. That said...

I think that NASA would tell even an ex astronaut to get bent if they thought he had no plasma separation. they just cannot afford to waste time and space on the ISS for something that they believe will not work. remember in addition to the world's most expensive hourly wages (figuratively) they are paying the astronauts, and consumables for the astronauts and station and premium equipment berthing real estate  the test engine will tap a significant portion of the electrical supply while charging up.

I also do not think Chang Diaz would overlook the plasma separation part of an engine or be unaware of it. Nor do i think he as CEO of his company which has other lucrative irons in  the fire and a rep to maintain if he wants to stay in business; would waste financial support on it if he did not think it would work.

Title: Re: VASIMR Engine
Post by: QuantumG on 12/25/2014 07:59 AM
I think that NASA would tell even an ex astronaut to get bent if they thought he had no plasma separation. they just cannot afford to waste time and space on the ISS for something that they believe will not work.

NASA doesn't have an opinion one way or another. That's why it's called an experiment.
Title: Re: VASIMR Engine
Post by: MP99 on 12/25/2014 08:31 AM
Quote
i got what he said a few posts ago but your illustration is simple and clear. That said...

I think that NASA would tell even an ex astronaut to get bent if they thought he had no plasma separation. they just cannot afford to waste time and space on the ISS for something that they believe will not work. remember in addition to the world's most expensive hourly wages (figuratively) they are paying the astronauts, and consumables for the astronauts and station and premium equipment berthing real estate  the test engine will tap a significant portion of the electrical supply while charging up.

I also do not think Chang Diaz would overlook the plasma separation part of an engine or be unaware of it. Nor do i think he as CEO of his company which has other lucrative irons in  the fire and a rep to maintain if he wants to stay in business; would waste financial support on it if he did not think it would work.
The plasma ejects through a magnetic nozzle, but magnetic fields form a loop away and then back.

They need the plasma to be guided by the nozzle in order to transfer momentum to the spacecraft (just like a chemical nozzle), but then detach from the magnetic field instead of following it back again.

They are absolutely aware of this as an issue, it's mentioned in papers, etc. They are convinced that their plasma will detach from their nozzle, but the ISS experiment is the first time that it can actually be demonstrated.

Cheers, Martin
Title: Re: VASIMR Engine
Post by: MP99 on 12/25/2014 08:40 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.

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.

Cheers, Martin
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/25/2014 11:20 AM
You say the VASIMR does not produce thrust, yet in the video I posted, we can see the VASIMR move the Momentum/Impulse response target.

Imagine ping pong balls attached to a board by rubber bands.  You make a fancy mechanism that will shoot them out really fast but unless you cut the rubber band they will come back and no net thrust will be produced.  Such a device could move a 'Momentum/Impulse response target' and still be useless in space.  I'm in no position to argue one way or the other but maybe it will help you understand QuantumG's take on the thing.

Thank you for that explanation, also to point out, VASIMR started out in NASA before it went to a private organisation. Also why would NASA approve of the testing on the ISS, if they it does not work. With the testing of VASIMR on ISS, ad astra rocket company are developing battery pack called Aurora (http://www.adastrarocket.com/aarc/VF-200), which will store the power needed, turn on VASIMR at 200 kilowatts for about 15 minutes before needing to be recharged. They could add some extra solar panels to the Aurora. 
Title: Re: VASIMR Engine
Post by: Nomadd on 12/25/2014 01:24 PM
 What can they prove at the ISS that a simple vacuum chamber wouldn't suffice for?
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/25/2014 01:52 PM
What can they prove at the ISS that a simple vacuum chamber wouldn't suffice for?

From the videos of VASIMR, we can see it apparently does work, which they have tested in a vacuum chamber. They will use it for station boosting and to see how well it will work in a real space environment.
Title: Re: VASIMR Engine
Post by: RonM on 12/25/2014 03:22 PM
What can they prove at the ISS that a simple vacuum chamber wouldn't suffice for?

From the videos of VASIMR, we can see it apparently does work, which they have tested in a vacuum chamber. They will use it for station boosting and to see how well it will work in a real space environment.

As previously mentioned, there probably isn't a vacuum chamber large enough to prove detachment will occur.

The blue glow proves VASIMR produces a plasma. The question is does the plasma continue on to produce a thrust or loops back along the magnetic field and does not produce a thrust. It is possible that the magnetic field will pull the electrons and ions in opposite directions before they recombine as neutral atoms, resulting in no thrust.

Theory says it will work, but they'll have to put it in space to prove it.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/25/2014 03:41 PM
What can they prove at the ISS that a simple vacuum chamber wouldn't suffice for?

From the videos of VASIMR, we can see it apparently does work, which they have tested in a vacuum chamber. They will use it for station boosting and to see how well it will work in a real space environment.

As previously mentioned, there probably isn't a vacuum chamber large enough to prove detachment will occur.

The blue glow proves VASIMR produces a plasma. The question is does the plasma continue on to produce a thrust or loops back along the magnetic field and does not produce a thrust. It is possible that the magnetic field will pull the electrons and ions in opposite directions before they recombine as neutral atoms, resulting in no thrust.

Theory says it will work, but they'll have to put it in space to prove it.


What about NASA's vacuum chamber? I read it is the largest in the world.
Title: Re: VASIMR Engine
Post by: Danderman on 12/25/2014 04:44 PM
What can they prove at the ISS that a simple vacuum chamber wouldn't suffice for?

The same could be asked for any rocket engine.  Why test it in flight if experimental tests on the ground show that the engine works?


Title: Re: VASIMR Engine
Post by: Stormbringer on 12/25/2014 05:07 PM
i think there is a difference in a system that must get from the surface of the earth to orbit. a fail there means a payload is destroyed at the very least. possibly human passengers. and a whole system has a whole lot more points of failure that the blue glowy poop trying to climb back aboard.
Title: Re: VASIMR Engine
Post by: RonM on 12/25/2014 06:12 PM
i think there is a difference in a system that must get from the surface of the earth to orbit. a fail there means a payload is destroyed at the very least. possibly human passengers. and a whole system has a whole lot more points of failure that the blue glowy poop trying to climb back aboard.

No, VASIMR, like any other rocket engine, will have to be tested in flight. That means in space for VASIMR, preferably on ISS. Until it is tested, they can't be sure if it works as intended.

NASA would not design an entire Mars campaign on an engine that might work. They will want to see the data first.
Title: Re: VASIMR Engine
Post by: Raj2014 on 12/26/2014 03:25 PM
Since apparently funding is what stopping them from continuing development of VASIMR, they could start a kickstarter campaign and a petition. I also read that VASIMR could also be used to shield astronauts and spacecraft from radiations, has this been confirmed?
Title: Re: VASIMR Engine
Post by: Stormbringer on 12/26/2014 06:48 PM
Since apparently funding is what stopping them from continuing development of VASIMR, they could start a kickstarter campaign and a petition. I also read that VASIMR could also be used to shield astronauts and spacecraft from radiations, has this been confirmed?

I have not heard that about VASIMR. I think you have conflated M2P2's intrinsic shielding with VASIMR. VASIMR does not want plasma looping around the ship structure. As QuantumG and others pointed out that would be bad for VASIMR. VASIMR needs the plasma to go away in order to work.

As to crowd funding; Dr Diaz has already ran one such campaign. so he may do another.
Title: Re: VASIMR Engine
Post by: momerathe on 12/26/2014 09:20 PM
iterestingly, vasimir may get some experimental support from kickstarter indirectly - a cubesat-sized plasma thruster called CAT: https://www.kickstarter.com/projects/longmier/cat-launch-a-water-propelled-satellite-into-deep-s

as far as I can tell it's a mini-vasimr - if it demonstrates detachment and/or works in orbit, it could provide evidence in support of it's bigger brother.
Title: Re: VASIMR Engine
Post by: MickQ on 12/28/2014 12:37 AM
Maybe a VASIMR test unit and an Aurora battery on a demonstrator flown as a secondary payload on a Falcon 9 or Antares ?

Mick.
Title: Re: VASIMR Engine
Post by: cordwainer on 12/28/2014 03:30 AM
Chemical rockets on the correct trajectory and launch windows or longer flight times with better shielding would work for manned missions to Mars just fine. Zubrin is correct in that the advantage of VASIMR is for unmanned cycler orbits to Mars of probes and supplies for colonists. Hi-PEP along with other technologies would be a better option for ISS and orbital ACS/RCS. The variable thrust that VASIMR technology provides would be much more suited to long and efficient cycler flights than ACS.
Title: Re: VASIMR Engine
Post by: savuporo on 12/28/2014 05:40 AM
VASIMR or this ? http://arc.aiaa.org/doi/abs/10.2514/1.B35250 ( published 2014 )


We had a thread on this (http://forum.nasaspaceflight.com/index.php?topic=15177.0), there is a previous publication (http://vixra.org/pdf/1301.0145v1.pdf) 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
Title: Re: VASIMR Engine
Post by: QuantumG on 12/28/2014 05:59 AM
Cancel the ISS experiment then, clearly it's not necessary. That's what Ad Astra are saying, right?
Title: Re: VASIMR Engine
Post by: savuporo on 12/28/2014 06:20 AM
Cancel the ISS experiment then, clearly it's not necessary. That's what Ad Astra are saying, right?

Huh ? ISS demo is sort of required to get it out of the TRL valley of death, otherwise it has no hopes of leaving earth orbit ever.
ISS happens to be the only suitable idea with sufficient power generation available for a meaningful TRL 7ish demo.
Title: Re: VASIMR Engine
Post by: QuantumG 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?
Title: Re: VASIMR Engine
Post by: savuporo 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.


Title: Re: VASIMR Engine
Post by: QuantumG on 12/28/2014 06:31 AM
Read what you just cited. I don't know what you're disagreeing about.
Title: Re: VASIMR Engine
Post by: guckyfan 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.
Title: Re: VASIMR Engine
Post by: savuporo 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.
Title: Re: VASIMR Engine
Post by: savuporo 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.
Title: Re: VASIMR Engine
Post by: QuantumG 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.
Title: Re: VASIMR Engine
Post by: guckyfan 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.

Title: Re: VASIMR Engine
Post by: savuporo 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 )
Title: Re: VASIMR Engine
Post by: Raj2014 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 (http://forum.nasaspaceflight.com/index.php?topic=15177.0), there is a previous publication (http://vixra.org/pdf/1301.0145v1.pdf) 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?
Title: Re: VASIMR Engine
Post by: Garrett 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 (http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6823704)
Title: Re: VASIMR Engine
Post by: savuporo 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.
Title: Re: VASIMR Engine
Post by: savuporo 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??
Title: Re: VASIMR Engine
Post by: savuporo 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 ..
Title: Re: VASIMR Engine
Post by: Raj2014 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.
Title: Re: VASIMR Engine
Post by: MP99 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 (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
Title: Re: VASIMR Engine
Post by: Stormbringer 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
Title: Re: VASIMR Engine
Post by: ThereIWas3 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".
Title: Re: VASIMR Engine
Post by: Stormbringer on 01/15/2015 02:56 AM
plasma detachement and other stuff:

http://www.adastrarocket.com/Jared-Space2014.pdf
Title: Re: VASIMR Engine
Post by: Moe Grills 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.
Title: Re: VASIMR Engine
Post by: Stormbringer on 01/21/2015 08:35 PM
1. It will work
2. yes.








3. The critics are full of... stuff.
Title: Re: VASIMR Engine
Post by: Raj2014 on 01/21/2015 10:47 PM
1. It will work
2. yes.








3. The critics are full of... stuff.

What Stormbringer said. Has there been an update from Ad Astra or Franklin Chang Diaz on VASIMR? What I know so far is that they are low on money, which they need to continue. They were planning to test VASIMR on ISS called VF-200 with a battery pack attached called Aurora.     
Title: Re: VASIMR Engine
Post by: abaddon on 02/27/2015 09:13 PM
Noticed these recent tweets today, linked from Wayne Hale's blog:

https://twitter.com/waynehale/statuses/570399963919704064
Quote
At the JSC-NAL dinner listening to Dr Franklin Chang Diaz discuss advanced space propulsion and his VASIMR rocket

https://twitter.com/waynehale/statuses/570415042874601472
Quote
Ad Astra ready to test fire their 200KW electric VASIMR rocket for 100 hours continuously. Planning to install it on ISS in a few years
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 02/27/2015 09:21 PM
Instead of putting the VASIMR on the ISS could it be added to a Dragonlab? Large solar panels will also be needed.

As a derivative of the Dragon space capsule the Dragonlab would come with RCS and navigation equipment.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 02/27/2015 09:31 PM
Instead of putting the VASIMR on the ISS could it be added to a Dragonlab? Large solar panels will also be needed.

As a derivative of the Dragon space capsule the Dragonlab would come with RCS and navigation equipment.

SpaceX likes to talk about DragonLab as if it's a done deal, but really it will only happen if they find paying customers for it.  So far, there's no evidence to indicate even a single paying customer.  So DragonLab keeps getting postponed indefinitely.

And ISS also has far larger solar panels.  I don't see any advantage to sending it on DragonLab versus ISS and lots of disadvantages.
Title: Re: VASIMR Engine
Post by: Stormbringer on 02/28/2015 12:33 AM
also if comments in the electric propulsion thread are true other electric thrusters have evolved to surpass VASIMR's projected specs. If those comments are true then Dr Diaz will need to significantly improve the technology in order to be competitive. This could be good for VASIMR if it is improved or catastrophic if it cannot be improved.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/01/2015 05:35 PM
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.

Ignoring power demands? Well okay, since you're assuming the use of Harry Potter's wand, 39 day trips to Mars are no problem.

But if you live in this world, the need for a 2kWe/kg power source is a definite show stopper.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 03/01/2015 07:35 PM
Instead of putting the VASIMR on the ISS could it be added to a Dragonlab? Large solar panels will also be needed.

As a derivative of the Dragon space capsule the Dragonlab would come with RCS and navigation equipment.

SpaceX likes to talk about DragonLab as if it's a done deal, but really it will only happen if they find paying customers for it.  So far, there's no evidence to indicate even a single paying customer.  So DragonLab keeps getting postponed indefinitely.

And ISS also has far larger solar panels.  I don't see any advantage to sending it on DragonLab versus ISS and lots of disadvantages.


A DragonLab with a VASIMR is a space ship rather than a spacestation - it can go places like a higher orbit. The ISS has other uses for the power from its so only occasional use will be permitted.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/01/2015 07:41 PM
I think anything that poops anything out one end (even if it's just blue glowy stuff) produces thrust.
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.
How is this still in question??

VASIMR has lots of problems, but this isn't one of them.

VASIMR is a big, expensive, complicated, heavy electric thruster. That is its main problem. I have no doubt that technically it could be made to work with enough money (I took a plasma physics course, and magnetic bottles is one of the things we studied). I am not, however, sure that it's worth it. Other electric thrusters may have less mass for the same power.
Title: Re: VASIMR Engine
Post by: Impaler on 03/02/2015 01:44 AM
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.

Ignoring power demands? Well okay, since you're assuming the use of Harry Potter's wand, 39 day trips to Mars are no problem.

But if you live in this world, the need for a 2kWe/kg power source is a definite show stopper.

Lets remember that anything <6 months is 'record time' because Chemical systems are running into brutal rocket-equation induced propellent fractions above that point and no one considers it practical to push Chemical that far.  For any Electric propulsion the power needs for 4-6 month transfers are well within reason both in total power and power density.

Ad-Astra has always presented the whole portfolio of how their engine produces different flight times when combined with a variety of power-systems over a range of power-densities.  These range from currently operational solar arrays to complete fantasy fusion reactors.  Claiming the system NEEDS a fantasy reactor is intellectually dishonest *cough Zubrin cough*  simply because they show what COULD be done if such a reactor existed.

No reasonable person claims 39 days is a bar we need to aim for now or ever.  Personally I think anything shorter then 3 months is complete overkill and very likely 6 months will be preferable as we will prefer the payload mass over the short transit time.

And lastly an alpha value (kW/kg) of 2 for the TOTAL propulsion system is actually quite reasonable, so long as you use thin-film solar and some thruster OTHER then VASIMR because it's so heavy.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/02/2015 02:25 AM
Nah, you can do WELL under 6 months with chemical rockets, especially if you fuel up at near C3=0 (like EML1/2 or something like that). Down to below 120 days transit, even. Doesn't mean it's ideal, but it IS definitely doable.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 03:10 AM
Claiming the system NEEDS a fantasy reactor is intellectually dishonest *cough Zubrin cough*  simply because they show what COULD be done if such a reactor existed.

*cough Sorensen (http://forum.nasaspaceflight.com/index.php?topic=1139.msg600043#msg600043) cough*

When the 39 day Mars trip story first came out I didn't notice the caveat it relied on a fantasy power source. Maybe it was in the fine print.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/02/2015 03:16 AM
Solar could actually do that level of performance, with the right structural concept. As Impaler said.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 03:35 AM
Solar could actually do that level of performance, with the right structural concept. As Impaler said.

You have an example? I seem to recall you saying some film on the solar sails of a venus probe achieved 1 kWe/kg.

I sounds to me these 2kWe/kg solar arrays are acres of Seran wrap or maybe Cellophane with little supporting structure.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 03:38 AM
Nah, you can do WELL under 6 months with chemical rockets, especially if you fuel up at near C3=0 (like EML1/2 or something like that). Down to below 120 days transit, even. Doesn't mean it's ideal, but it IS definitely doable.

Indeed. Assuming a propellent source at EML2, chemical can do transfers a lot faster than Hohmann.

(http://clowder.net/hop/TMI/EDSforMars.jpg)

(http://clowder.net/hop/TMI/EDSforMars%207.jpg)
Title: Re: VASIMR Engine
Post by: Nilof on 03/02/2015 09:25 AM
Though to be fair, 7 km/s is a pretty huge delta-v for a chemical rocket. Compared to the 5.7 month option, you'd be roughly tripling the mass ratio of the spacecraft for a 25% decrease in travel time. I think it's more or less fair to say that chemical can do a 5 month transfer, but pushing it beyond that really isn't worth it.
Title: Re: VASIMR Engine
Post by: clongton on 03/02/2015 11:48 AM
I think it's more or less fair to say that chemical can do a 5 month transfer, but pushing it beyond that really isn't worth it.

Depends entirely on whether the cargo is toilet paper or people.
Title: Re: VASIMR Engine
Post by: Stormbringer on 03/02/2015 12:47 PM
If its toilet paper it's got to be faster. The colonists would revolt if they had to wait in the bathroom for 5 months.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 01:43 PM
Though to be fair, 7 km/s is a pretty huge delta-v for a chemical rocket. Compared to the 5.7 month option, you'd be roughly tripling the mass ratio of the spacecraft for a 25% decrease in travel time. I think it's more or less fair to say that chemical can do a 5 month transfer, but pushing it beyond that really isn't worth it.

I'd like to see a combination of ion and chemical. Most ion Mars trips already assume use of chemical to haul humans to the edge of earth's sphere of influence and rendezvous with the ion MTV. This is to avoid subjecting human astronauts to a slow spiral through the Van Allen Belts.

A chemical reusable Earth Departure Stage (EDS) (http://hopsblog-hop.blogspot.com/2014/05/reusable-earth-departure-stage.html) could provide a hefty boost into a heliocentric transfer orbit and thus eliminate the slow spiral out of earth's gravity well and leave more reaction mass for the ion rocket.

Given a boost by a chemical EDS, large solar arrays with a good alpha become more plausible. Low earth orbit with it's high debris density and Van Allen belts would be tough on a solar array with a big cross section. It would be better if the ion space craft could unfurl it's solar arrays after leaving the tough neighborhood of low earth orbit.
Title: Re: VASIMR Engine
Post by: Impaler on 03/02/2015 04:49 PM
7 km/s Burns from EML1 are crazy high on their face but get even worse when you remember that it is 4 km/s just to get up to EML1 so your cumulative total is 11 km/s if your moving everything chemically, that is Earth launch level of DeltaV and is going to result in propellent fractions in the 90's (92% for HydroLox, 96% MethoLox).  That is completely untenable in my opinion as we would need thousands of tons IMLEO just to send small vehicles to Mars (or the even more unlikely massive Asteroid/Lunar based propellent production process).


Boosting a SEP stage with chemical is pointless, I do not see why anyone thinks this is a good idea.  First off mixing two different propulsion techs means we have to carry the mass of two completely separate engines which clobbers the efficiency of both.  We also have the combined risk of failure of both engines (the chemical is by far the more failure prone of the two).

The argument that we don't want to spiral out from Earth is only applicable for CREW and even then only for the first few Radii of the Earth where the Belt is.  We would send the bulk of the mission mass up to a high orbit and then after the crew arrives we just Spiral out some more for the Earth-Escape.  The initial escape velocity from Earth will be low but that is fine, we are going to be building velocity over months.  The speed that the Chemical departure from Earth would have gotten us (1 km/s which still costs a hefty 20% propellent fraction) will be obtained in mere 11 days at an acceleration of 1 mm/s^2.  We would much rather have 20% of our mass devoted to more EP dry-mass (power system) or propellent then to get a measly 1 km/s escape velocity, devoting that mass to EP will always get you to Mars faster.

Thus any in-space propulsion, unless it must be high thrust (such as an attempt to propulsive capture around a planet when your coming on a hyperbolic trajectory at high velocity) it is never a reason to hybridize EP and Chemical, they will just drag each other down.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 05:54 PM
7 km/s Burns from EML1 are crazy high on their face but get even worse when you remember that it is 4 km/s just to get up to EML1

Ah. You didn't bother to read the link. Here (http://hopsblog-hop.blogspot.com/2014/05/reusable-earth-departure-stage.html) it is again.

Earth isn't the only possible source of propellent. A propellent source high on the slopes of earth's gravity well changes the picture. It'd be helpful for chemical as well as ion rockets.

Title: Re: VASIMR Engine
Post by: Impaler on 03/02/2015 06:40 PM
Actually I did read your link and I commented that such a source or propellent is unlikely to materialize any time soon.  And if we had it we would not want to waste it on chemical propulsion or the even more wasteful hybrid-system you described earlier.

That said I do agree that a reusable chemical Earth-departure stage is a fine idea assuming I am going full chemical departure (indeed without them the all-chemical idea is unsustainable from a cost of hardware perspective) and have said so in the MCT speculation threads, I just think it will be employed from LEO, burn from LEO return to LEO and be refueled in LEO.  EML1 is a highly desirable stopping off point for SEP vehicles because of the transit time issues and crew rendezvous necessity on their way to departure, but it makes no sense to send chemical vehicles through it, direct departure from LEO will be preferable not least of which is that I can just send the crew to the vehicle by a simple LEO capsule like Dragon or CST-100.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 07:20 PM
Actually I did read your link

The link talked about the possibilities opened by other propellent sources.

So what does your 4 km/s from LEO to EML1 argument demonstrate? That you enjoy typing out a wall of text based on an irrelevant straw man.

and I commented that such a source or propellent is unlikely to materialize any time soon.

Well, I happen to believe developing extra-terrestrial propellent is more plausible than a 2kWe/kg energy source. But that is a separate argument.

If you want to argue other propellent sources are implausible that's one thing. But tossing out delta V budgets based on earth being the sole propellent source is a waste of my time.
Title: Re: VASIMR Engine
Post by: Impaler on 03/02/2015 08:18 PM
Well, I happen to believe developing extra-terrestrial propellent is more plausible than a 2kWe/kg energy source. But that is a separate argument.

If you want to argue other propellent sources are implausible that's one thing. But tossing out delta V budgets based on earth being the sole propellent source is a waste of my time.

Well Earth IS the only source of propellent right now so DeltaV from LEO is what any chemical system has to work under, so it is quite relevant.  As soon as you start talking about in-space propellent sources your into a HIGHLY speculative area and were weighing two different speculative ideas.

But it needs to be a fair comparison, you've comparing the power source density that makes 39 day trips to Mars possible (and that's after the VASMIR system sand-bags the vehicle as other thrusters have better density) vs an off world propellent source and chemical architecture that's makes a 4.3 - 5.7 month transits.

This is not even remotely in the same ball-park of difficulty.  If you want a EP system to do a comparable transit 4-6 month transit it's power density can be an order of magnitude lower, making it actually quite near term.  Thus your conclusion about relative nearness/plausibility is reversed, off world propellent is much less plausible then the power-density for an EQUIVALENT PERFORMANCE electric propulsion system.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/02/2015 10:20 PM
Well Earth IS the only source of propellent right now

Well a 2kWe/kg power source IS a fantasy right now.

The conventional wisdom is that chemical is inadequate. NTR, NEP or SEP are needed.

Which is completely untrue if there there is a source of chemical propellent near C3=0. Bringing about such a propellent source is one of the first goals of Planetary Resources. Not to mention Jeff Greason, Bill Stone, Paul Spudis and a lot of other folks.

And given a propellent source near C3=0, a chemical EDS could indeed lend a hand to ion engines.

Title: Re: VASIMR Engine
Post by: Impaler on 03/03/2015 07:53 AM
Ok Planetary Resources is going to get us to Mars, see you there in 100 year  ::)

Also did you not read the point that 2kw/kg is complete overkill and a not necessary or are you just ignoring that so you can continue making dishonest comparisons?

And lastly NO, using chemical propulsion from EML1 dose not 'lend a hand' to SEP any more then say taking a Hummer and having it push a Prius around would 'lend a hand', it wastes propellent that could otherwise be going into the SEP vehicle without reducing our transit time by any appreciable amount. 

That propellent is not going to be cheap no mater how advanced or large scale our fantasy production process becomes, we are going to want to send as much stuff to Mars per unit of our precious propellent as possible.  That rules out using chemical UNLESS we absolutely must because of high acceleration needs.
Title: Re: VASIMR Engine
Post by: RanulfC on 03/03/2015 05:34 PM
And lastly NO, using chemical propulsion from EML1 dose not 'lend a hand' to SEP any more then say taking a Hummer and having it push a Prius around would 'lend a hand', it wastes propellent that could otherwise be going into the SEP vehicle without reducing our transit time by any appreciable amount.

Really? 'cause just about every study I've seen if you JUST launch from EML-2 straight to an interplanetary trajectory its ok, but it you say do an Earth-flyby from EML 1/2 whatever drive you use for the injection at perigee is greatly enhance and chemical will do it better than straight SEP does. From EML-1 to interplanetary injection is a (to use your totally inadequate "cars" analogy :) ) is a Hummer pushing a Prius to the crest of a hill so the (supposedly under-powered and slow accelerating Prius doesn't take forever to get UP the hill in the first place) can then push itself over the crest and down the other side. In proper terms the chemical booster (which then remains near its source of propellants for ease of access) gives the SEP a very neat "kick-in-the-pants" to get it out of the local gravity field without the SEP having to waste propellant doing it for itself.

SEP is a low thrust system unless something changes drastically with future systems while chemical/nuclear are high thrust systems which trade propellant for time. SEP takes time to go anywhere and EVENTUALLY can reach some serious delta-v but it trades time for the higher efficiency and lower thrust.

Quote
That propellent is not going to be cheap no mater how advanced or large scale our fantasy production process becomes, we are going to want to send as much stuff to Mars per unit of our precious propellent as possible.  That rules out using chemical UNLESS we absolutely must because of high acceleration needs.

And therefore chemical by your argument, (and its one Elon Musk, Zubrin, etc have used) is superior to SEP because we in fact are limited on TIME and not propellant. Once out away from Earth, (and beyond the Van Allens) time is a bit more on our side but not that much.

if it sounds like I'm arguing AGAINST SEP then you don't understand the argument because I'm not. But it does take time and effort to get to the point where SEP is comparable with chemical for the final push to interplanetary trajectory. In the end getting the ship, personnel and all equipment to point around EML-1/2 is a prerequisite to using SEP efficiently. With just about as much effort you can also get propellant from the Moon so the two are far from mutually exclusive proposals.

Randy
Title: Re: VASIMR Engine
Post by: Impaler on 03/03/2015 09:51 PM
OK lets keep going with this Hummer/Prius analogy, it is kind of amusing.

The flaw in your hill analogy is that EML1 is not the top of a hill, it is more like the lip of the grand canyon with the canyon being the Earths gravity well (it's not literally C3=0 but its very close).  Once your up on the plateau (heliocentric space) it is perfectly flat and the Prius is free to accelerate.  If you were going to use a Hummer to push a Prius you would do it going up the side of the canyon UNTIL you got to the lip, not after that point. 


Your correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth.  And the DeltaV is VIRTUALLY THE SAME.  The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect.  But is in no way comes even remotely close to making them as efficient as Electric propulsion, when the ISP difference is an order of magnitude the tiny improvement in the chemical system is pathetic.

How do you claim that 'In the end getting the ship, personnel and all equipment to point around EML-1/2 is a prerequisite to using SEP efficiently' is 'With just about as much effort you can also get propellant from the Moon'.  That is absurd, the SEP vehicle simply spirals out for a few months, you know cause it is a VEHICLE designed to do exactly that, and then a capsule dose a rendezvous and transfers crew something that our capsules are very good at and do at ISS routinely, a rendezvous at EML1 will be adding a trans-lunar injection step which we did back under Apollo-8 and plan to do again with Orion.  This is simple operational and technologically.

Propellent production on the moon is outrageously harder to do, requiring a whole mining infrastructure operating autonomously at near absolute zero, storing it and then loading into tankers to orbit (which will burn ~80% of the propellents produced on the surface to deliver the 20% remainder to orbit and then land again).  No one in their right mind could equate these things in difficulty.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/03/2015 10:55 PM
The argument that we don't want to spiral out from Earth is only applicable for CREW and even then only for the first few Radii of the Earth where the Belt is.  We would send the bulk of the mission mass up to a high orbit and then after the crew arrives we just Spiral out some more for the Earth-Escape.  The initial escape velocity from Earth will be low but that is fine, we are going to be building velocity over months.  The speed that the Chemical departure from Earth would have gotten us (1 km/s which still costs a hefty 20% propellent fraction)

Incorrect.

Falling from EML2 will give you an extra 3.1 km/s at perigee. Not 1 km/s.

3.1 over the 7.7 km/s LEO speed is 10.8 km/s, a perigee velocity just a hair under escape.

At 10.8 km/s you wound have your burn enhanced by an healthy Oberth benefit. A .5 km/s burn at perigee will buy you 3 km/s Vinfinity.


will be obtained in mere 11 days at an acceleration of 1 mm/s^2.

Most proposed Mars Transfer Vehicles (MTV) I've seen mass 130 tonnes.

Spiraling from LEO to C3=0 takes about 7 km/s delta V. Then spiraling to Mars takes another 6 km/s. Assuming a 30 km/s exhaust velocity, it'd take 70 tonnes of xenon impart 13 km/s to a 130 tonne MTV.

So now we have 200 tonnes not counting the power source and ion rocket engines.

To give an acceleration of 1mm/s^2 to 200 tonnes requires a 200 newton ion engine.

Please describe the power source you have in mind for a 200 newton ion engine.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/03/2015 11:26 PM
Ok Planetary Resources is going to get us to Mars, see you there in 100 year

What? You want to colonize Mars in a few decades. And with the same breath you say extracting water from a Near Earth Asteroid is a bridge too far?

That's hilarious.

Also did you not read the point that 2kw/kg is complete overkill and a not necessary or are you just ignoring that so you can continue making dishonest comparisons?

To be fair you have distanced yourself from the 39 day VASIMR trips.

In an earlier post I had thought you were talking about an 11 day spiral out of earth's gravity well. So I thought you were still stuck on this magic alpha.

On a more careful reading I see you were talking about 11 days to accelerate 1 km/s.

So yes, it is wrong  for me to wave the 2kWe/kg in your face. My apologies.

And lastly NO, using chemical propulsion from EML1 dose not 'lend a hand' to SEP any more then say taking a Hummer and having it push a Prius around would 'lend a hand', it wastes propellent that could otherwise be going into the SEP vehicle without reducing our transit time by any appreciable amount.

This based on the assumption that burns totaling 1 km/s gets you 1 km/s delta V. Which is of course wrong.

The propellent and life support consumables from an asteroid would be high in earth's gravity well and have lots of potential energy. Nudges totaling .4 km/s suffice to send the ship to a low perigee where potential energy is converted to kinetic energy. At perigee the space ship would be moving 10.8 km/s. At this high speed the Oberth benefit is huge and another .5 km/s suffices for Trans Mars Insertion. Thus about 1 km/s suffices for TMI.

Spiraling from LEO to C3=0 takes about 7 km/s. If the acceleration is 1 km/s each 11 days, it'd take 77 days to spiral out of earth's gravity well. Falling from EML2, it'd take about 9 days to reach escape velocity.

And even if exhaust velocity is 30 km/s, 7 km/s to get out of earth's well is nothing to sneeze at.
exp(7/30)-1= .263.
Title: Re: VASIMR Engine
Post by: Burninate on 03/04/2015 12:08 AM
My attitude is that 39 day transits are nuts.  90 day transits are unrealistic.  ~200 day transits are realistic, but not spiralling out from HEO - it takes too long for a given power.

Spiral out to ~1LD on 4000s xenon over several years, then lower periapsis to ~400km over several months with xenon, then send a Crew Dragon on a methane transfer stage up to rendezvous, then Oberth burn the last of its 380s methane (~400m/s) to transition to a low energy Mars transfer, then spend three months coasting and four months burning xenon (a few hundred m/s) to capture.

You just arrived at Mars orbit rendezvous with a ~2/3 IMLEO mass fraction and an intact solar propulsion system without staging or aerocapture.

Ion propulsion doesn't give you speed, it gives you prepositioned assets on very low IMLEO.  A high elliptical Earth orbit transfer vehicle & fuel, which is >80% of the dV to Mars, is a prepositioned asset that human crew can inhabit and leave orbit with in a brief amount of time.
Title: Re: VASIMR Engine
Post by: Impaler on 03/04/2015 06:30 AM
Please describe the power source you have in mind for a 200 newton ion engine.

I'll describe both the thrusters and the power source.  20 Concentric Nested Hall thrusters (the X3 from University of Michigan in testing now) operating at 200 kw each and delivering 10 N each.  Total mass is 6,000 kg including power processing units.  Power would be 4MW provided by a solar array with a power density of 250W/kg (design goals of arrays in development now) and massing a total of 16,000 kg.  This gives a total propulsion system mass of 22,000 kg.  The alpha value is thus 5.5 kg/kw quite low and nothing spectacular.  And this is enough to do the job, in fact it may even be excessive, we can spiral out slower then 77 days at higher ISP to save propellents for the heliocentric phase of the journey.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/04/2015 03:34 PM
Please describe the power source you have in mind for a 200 newton ion engine.
I'll describe both the thrusters and the power source.  20 Concentric Nested Hall thrusters (the X3 from University of Michigan in testing now) operating at 200 kw each and delivering 10 N each.

20 kilowatt per newton Hall thrusters. Yes, that's plausible. In fact that's what I used in Catching an Asteroid (http://hopsblog-hop.blogspot.com/2013/04/catching-asteroid.html). The Keck vehicle would have 4 10 kw thrusters which I figured would provide two newtons.

Total mass is 6,000 kg including power processing units.  Power would be 4MW provided by a solar array with a power density of 250W/kg (design goals of arrays in development now) and massing a total of 16,000 kg.

I'd like to know more about these solar arrays in development. Could you provide a link?

One figure I'm interested in is watts per square meter. What would be the area of this 4 mega watt solar array?
Title: Re: VASIMR Engine
Post by: Nilof on 03/04/2015 04:33 PM

I'd like to know more about these solar arrays in development. Could you provide a link?

One figure I'm interested in is watts per square meter. What would be the area of this 4 mega watt solar array?

A rough approximate figure from the phase I ROSA winglets (http://www.nasa.gov/offices/oct/home/feature_sas.html) is ~3 square meter per kW.

If the design uses phase 1 winglets along a long boom which extends 15 meters each way, you get roughly ~30 square meters of arrays, or 10 kW, per meter of boom. That gives us ~400 m of trussings to support the winglets. For a cross shaped design this gives you four 100m booms.

This is big, but then again so is your 200 ton ship with a bigger payload than a BA 2100.  If you went with a ~50 ton ship pushing a Skylab sized BA-330 habitat that launches on a single SLS launch, you're looking at four ~25 meter booms, which is short enough to comfortably fit inside the largest SLS fairing.

In fact, this last ship design is something I've actually done in KSP with the realism overhaul modpack. See the attached screenshot for a an example ~60 ton ship with 2 MW of solar arrays, which was launched without a hitch with a single SLS.

It isn't a beauty since it was built out of parts that really weren't meant to be used together, but it does give you a rough idea of the relative sizes of the solar panels needed.
Title: Re: VASIMR Engine
Post by: Impaler on 03/04/2015 05:15 PM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3Dada444956&ei=E0b3VLmZAoapogSclYGYDw&usg=AFQjCNGIl9ZWrPlnvVDUGJO1T3-RcwZOOg&sig2=NOHULiIg5knnM_pVDUIBNA

http://www.nsti.org/Nanotech2009/abs.html?i=1497

Title: Re: VASIMR Engine
Post by: Stormbringer on 03/04/2015 05:37 PM
just throwing out a random thought... have you guys seen that recently deployed bowl shaped thing on SMAP:

http://www.space.com/28676-dirt-satellite-antenna-video.html

its 20 meter diameter.

and there is plans for this thing:

http://www.space.com/28650-space-telescope-tech-aragoscope.html

with a half a mile diameter. a half mile diameter.

arent there new solar cell materials that roll and unroll?
Title: Re: VASIMR Engine
Post by: tea monster on 03/04/2015 07:47 PM
As far as I'm aware, the rapdar stuff is rolable.

I'd be interested in some figures for the power to area as well. I'm thinking of doing a 3D model of one of these things. I was thinking that you could unfurl the solars in petals from the central core. You could even put a gentle spin on the ship to stabilize them.

On that subject, how much fuel would you need for an X3 hall thruster vehicle if you were to try to get to Mars in 40 days? It might be wasteful, but how does it compare to having to carry all the extra consumables for a crew for the extra months? Also, if you were an astronaut, and they told you you could get to Mars in 40 days, or you would have to spend an extra 6 months living in a balloon the size of a school bus, what would your reaction be?
Title: Re: VASIMR Engine
Post by: Hop_David on 03/04/2015 11:14 PM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

It's not rigid? How will you keep the surface perpendicular to the sun's rays?

The thrust vector would be perpendicular to the radius vector from earth's center, correct? and the thrust would have to be through the ship's cg.

So the ship and thrusters would be rotating 360º every 90 minutes when it's in low orbit and slower as the orbit rises.

But the solar arrays will need to remain pointed towards the sun.

Looking at the PDF I didn't see watts per square meter. At the moment I'm imagining this power source as a few hectares of Seran Wrap.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/04/2015 11:18 PM
On that subject, how much fuel would you need for an X3 hall thruster vehicle if you were to try to get to Mars in 40 days?

It's the 2kWe/kg alpha that Sorensen was objecting to. More fuel doesn't help that alpha.
Title: Re: VASIMR Engine
Post by: Solman on 03/05/2015 02:04 AM
Well Earth IS the only source of propellent right now

Well a 2kWe/kg power source IS a fantasy right now.

The conventional wisdom is that chemical is inadequate. NTR, NEP or SEP are needed.

Which is completely untrue if there there is a source of chemical propellent near C3=0. Bringing about such a propellent source is one of the first goals of Planetary Resources. Not to mention Jeff Greason, Bill Stone, Paul Spudis and a lot of other folks.

And given a propellent source near C3=0, a chemical EDS could indeed lend a hand to ion engines.

I think "fantasy" is perhaps a little strong with respect to 2kWe/kg but of course YMMV  :)
I realize that the solar concentrator based system I advocate does not currently exist as a TRL 9 space system but all the elements to build it do exist and have been separately tested or used in space and the system of large concentrator with actively cooled PV array for high solar concentration is being used by an outfit in Australia currently to generate electricity. With the 17 kW(thermal)/kg prototype concentrator developed by L'Garde it is difficult to see how it could do less than 5kW/kg.
A large concentrator facilitates solar thermal for LEO to escape with the PV moved into the focus to power SEP thereafter with only the mass penalty of the bread box sized STP engine.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 02:42 AM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

It's not rigid? How will you keep the surface perpendicular to the sun's rays?
...
It doesn't HAVE to be perfectly rigid. If you're off by a few degrees, there's only incredibly slight reduction in power. And it is deployed, so launch harmonics isn't a concern.

This is different from a traditional antenna or a concentrating solar array which DO have to be rigid because of their high pointing requirements (phased array antenna can compensate for this).
Title: Re: VASIMR Engine
Post by: Impaler on 03/05/2015 02:57 AM
When were orbiting the Earth ever 90 minutes the sun is shifting only 4 degrees per minute, a rate that we can easily match by rotating/pivoting the boom arm that the solar array is on without significant stress.  The RAPDAR is by no means Saran wrap it looks more like a sheet of plastic at least as thick as a milk-jug, Saran wrap would be IKAROS derived system 'solar sail' stuff which would be at least 4 times higher power density and which is a good deal more speculative but still not a fantasy.  I think an advanced total system alpha of 2 is the most optimistic view that dose not fall under fantasy, aka we can see a clear design that gets us their but know that it will be very hard, and I don't see such systems coming online for decades.

I went with systems that are currently in development to give us a very near term system with numbers we could be confident about as that seems to be a big hand up in the discussion, the idea that SEP is not viable without some BIG advancement that is so speculative that it may not ever happen.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 03:35 AM
Why would you characterize IKAROS as speculative? It already flew.

A fairer suggestion would be that it is an unorthodox space structure due to its very low stiffness, and thus would require more care than usual for designing your spacecraft correctly, but I don't believe "speculative" makes sense, there.

...and I'm sorry for jumping on that word (when in all likelihood we're in violent agreement), I just think it's an important distinction to make.

People have been testing (and preparing for launch) solar sail craft for a while, now. An IKAROS-esque solar array would be no more speculative than that sort of structure. Clearly wouldn't be characterized as fantasy.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 03:43 AM
I think a good proposal for a small-sat tech demo would be a "solar power sail" type craft with extremely good alpha.

IKAROS-style high voltage solar array (make it very long and skinny so that it demonstrates scalability) hooked directly up to a very high specific power thruster (built for high operating temperature so that extra heat rejection using a complicated radiator system is not required) using, say, solid-state relays. I bet you could demonstrate 1-2kW/kg OVERALL specific power (but with a system mass of, say, 100-200kg). It'd be a challenge, but should definitely be possible and would seriously change the whole calculus of SEP.

...then again, we're still waiting for even modest SEP propulsion tech on cubesats...
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 03:59 AM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3Dada444956&ei=E0b3VLmZAoapogSclYGYDw&usg=AFQjCNGIl9ZWrPlnvVDUGJO1T3-RcwZOOg&sig2=NOHULiIg5knnM_pVDUIBNA

http://www.nsti.org/Nanotech2009/abs.html?i=1497

More interesting, IMHO, is the MegaROSA concept, which can do 400-500W/kg (and hundreds of kW per wing). The smaller ROSA array is supposed to fly to ISS in 2016. (This is similar to but much, much better than Hubble's original solar arrays...)
http://www.keyt.com/news/goleta-based-company-could-power-nasa-to-mars/26754032


Or similarly, the MegaFlex array by ATK capable of 200-300W/kg and built on UltraFlex heritage:
https://www.youtube.com/watch?v=3dZuiYqcbXI
Title: Re: VASIMR Engine
Post by: Impaler on 03/05/2015 05:03 AM
Why would you characterize IKAROS as speculative? It already flew.

A fairer suggestion would be that it is an unorthodox space structure due to its very low stiffness, and thus would require more care than usual for designing your spacecraft correctly, but I don't believe "speculative" makes sense, there.

...and I'm sorry for jumping on that word (when in all likelihood we're in violent agreement), I just think it's an important distinction to make.

People have been testing (and preparing for launch) solar sail craft for a while, now. An IKAROS-esque solar array would be no more speculative than that sort of structure. Clearly wouldn't be characterized as fantasy.

I think we are generally in agreement, while IKAROS has flown the power system your extrapolating at 1 kw/kg is 'derived' from it and has some significant engineering challenges when being scaled up to the size (multiple MW) that would be the kind of total power needs that would be desired, demonstrating scale is a big part of making the specific power number relevant for SEP.  So I'm simply calling any specific power density goal which is not the design goal to a current development program a 'speculative' one. 

Essentially I assume all current development programs that are just refining current tech will meat their goals (admittedly optimistic) but anything outside of a program has some chance of not being delivered upon and thus is a 'speculation'.  Naturally their are huge ranges between very likely to be delivered upon and very unlikely to be delivered upon speculative systems.  When the speculation exceeds what even the best known materials or some very obvious thermodynamic or practicality limits then I'd call it fantasy, and I'd say that when it comes to solar power density the >2kw/kg can be called fantasy, 250W-2kw can be called speculative, and <250W/kg can be taken to the bank.

I had been trying to find the numbers on the MegaROSA and how it compared with original ROSA, I had thought the power density was much lower around 150W/kg for ROSA and couldn't find a number for MegaROSA, your link doesn't seem to have a reference to power density though, do you have one that dose?
Title: Re: VASIMR Engine
Post by: Earendil on 03/05/2015 05:34 AM
Maybe a bit off-topic question, but.. cout a VASIMIR engine be used to take the ISS to Mars? Not necessarily as a spacecraft.., but maybe as a support station in Mars orbit. Even if it takes 5-6 yrs to get there.. better than being decommissioned.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 03/05/2015 05:39 AM
As far as I'm aware, the rapdar stuff is rolable.

I'd be interested in some figures for the power to area as well. I'm thinking of doing a 3D model of one of these things. I was thinking that you could unfurl the solars in petals from the central core. You could even put a gentle spin on the ship to stabilize them.

On that subject, how much fuel would you need for an X3 hall thruster vehicle if you were to try to get to Mars in 40 days? It might be wasteful, but how does it compare to having to carry all the extra consumables for a crew for the extra months? Also, if you were an astronaut, and they told you you could get to Mars in 40 days, or you would have to spend an extra 6 months living in a balloon the size of a school bus, what would your reaction be?

It's not that you'd need much propellant for Hall thrusters, it's that you'd need lots and lots of them.  The mass of the thrusters themselves would dominate if you wanted enough thrust to get to Mars in 40 days.  Hence the idea for VASIMR -- better thrust-to-weight, at the cost of worse Isp (so more prop needed).
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 03/05/2015 06:18 AM
I think a good proposal for a small-sat tech demo would be a "solar power sail" type craft with extremely good alpha.

IKAROS-style high voltage solar array (make it very long and skinny so that it demonstrates scalability) hooked directly up to a very high specific power thruster (built for high operating temperature so that extra heat rejection using a complicated radiator system is not required) using, say, solid-state relays. I bet you could demonstrate 1-2kW/kg OVERALL specific power (but with a system mass of, say, 100-200kg). It'd be a challenge, but should definitely be possible and would seriously change the whole calculus of SEP.

...then again, we're still waiting for even modest SEP propulsion tech on cubesats...

The CAT thruster from the University of Michigan is a SEP for cubesats. It is due to be launched within the next year. The thruster takes 10W and fits in a 3U cubesat. The 20W solar panels on the current spacecraft could be replaced by experimental solar arrays in later launches.

http://pepl.engin.umich.edu/thrusters/CAT.html (http://pepl.engin.umich.edu/thrusters/CAT.html)
Title: Re: VASIMR Engine
Post by: Impaler on 03/05/2015 06:41 AM
As far as I'm aware, the rapdar stuff is rolable.

I'd be interested in some figures for the power to area as well. I'm thinking of doing a 3D model of one of these things. I was thinking that you could unfurl the solars in petals from the central core. You could even put a gentle spin on the ship to stabilize them.

On that subject, how much fuel would you need for an X3 hall thruster vehicle if you were to try to get to Mars in 40 days? It might be wasteful, but how does it compare to having to carry all the extra consumables for a crew for the extra months? Also, if you were an astronaut, and they told you you could get to Mars in 40 days, or you would have to spend an extra 6 months living in a balloon the size of a school bus, what would your reaction be?

It's not that you'd need much propellant for Hall thrusters, it's that you'd need lots and lots of them.  The mass of the thrusters themselves would dominate if you wanted enough thrust to get to Mars in 40 days.  Hence the idea for VASIMR -- better thrust-to-weight, at the cost of worse Isp (so more prop needed).

That's backwards, Halls have higher power to mass then VASIMR.  VASIMR has higher ISP range but in the area where the ISP ranges overlap (the low end of VASIMR, the High end of Hall) the Hall has better thrust to mass ratio.  VASIMR would be the choice for a very slow trajectory with minimal propellent usage by utilizing it at near the maximum ISP it's capable of.

And seriously the 40 day stuff is total overkill, even the VASMIR designs that did this used huge amount of propellent (400-600 MT if I recall) and pathetically small payloads to do it on top of the absurd amounts of power.  The extra crew consumables for a slower transit would be orders of magnitude less, I think crew consumables worst case are ~10 kg a day for everything (food, water, sanitation), so ~2 MT for a crew of 6 for a whole month.

SEP will certainly run up against some barrier at long transit times where savings in propellent mass are offsets by growing crew consumable mass but it will be out somewhere in the multiple months time frame and our life-support and recycling get better the cross over point gets pushed further out in time and becomes less of a factor.  Desire for fast transits has always been driven by radiation and health concerns, not consumable masses.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 03/05/2015 06:47 AM
As far as I'm aware, the rapdar stuff is rolable.

I'd be interested in some figures for the power to area as well. I'm thinking of doing a 3D model of one of these things. I was thinking that you could unfurl the solars in petals from the central core. You could even put a gentle spin on the ship to stabilize them.

On that subject, how much fuel would you need for an X3 hall thruster vehicle if you were to try to get to Mars in 40 days? It might be wasteful, but how does it compare to having to carry all the extra consumables for a crew for the extra months? Also, if you were an astronaut, and they told you you could get to Mars in 40 days, or you would have to spend an extra 6 months living in a balloon the size of a school bus, what would your reaction be?

It's not that you'd need much propellant for Hall thrusters, it's that you'd need lots and lots of them.  The mass of the thrusters themselves would dominate if you wanted enough thrust to get to Mars in 40 days.  Hence the idea for VASIMR -- better thrust-to-weight, at the cost of worse Isp (so more prop needed).

That's backwards, Halls have higher power to mass then VASIMR.  VASIMR has higher ISP range but in the area where the ISP ranges overlap (the low end of VASIMR, the High end of Hall) the Hall has better thrust to mass ratio.  VASIMR would be the choice for a very slow trajectory with minimal propellent usage by utilizing it at near the maximum ISP it's capable of.

No, it's not backwards.  What I said is exactly right.  Of course in the low thrust range Hall has a better thrust to mass ratio.  But we aren't talking about the low thrust range.  The question was how to get to Mars in 40 days.  That requires high thrust.  So VASIMR operating in high-thrust mode is what we are comparing to the Hall thrusters here.  And in high-thrust mode, VASIMR has better thrust to weight.
Title: Re: VASIMR Engine
Post by: KelvinZero on 03/05/2015 07:53 AM
Maybe a bit off-topic question, but.. cout a VASIMIR engine be used to take the ISS to Mars? Not necessarily as a spacecraft.., but maybe as a support station in Mars orbit. Even if it takes 5-6 yrs to get there.. better than being decommissioned.

Yeah that has been a subject a few times. There are a bunch of reasons against it, apparently.
This thread looks like it also lists a bunch of other threads:
http://forum.nasaspaceflight.com/index.php?topic=29003.msg906340#msg906340
Title: Re: VASIMR Engine
Post by: Impaler on 03/05/2015 07:59 AM
No your still completely backwards, ISP and thrust are inversely proportional, the high ISP range is thus the low thrust range.  HALL is low to medium ISP, VASMIR is medium to high ISP.

At the medium ISP where an apples to apples comparison can be made HALL has better thrust to mass, this has been pointed out by multiple people already in this thread and in the electric propulsion thread, VASIMR is a very massive system with an impressive ISP range and high maximum ISP, but at the low end it's not competitive with a modern HALL.
Title: Re: VASIMR Engine
Post by: ChrisWilson68 on 03/05/2015 08:09 AM
No your still completely backwards, ISP and thrust are inversely proportional, the high ISP range is thus the low thrust range.  HALL is low to medium ISP, VASMIR is medium to high ISP.

At the medium ISP where an apples to apples comparison can be made HALL has better thrust to mass, this has been pointed out by multiple people already in this thread and in the electric propulsion thread, VASIMR is a very massive system with an impressive ISP range and high maximum ISP, but at the low end it's not competitive with a modern HALL.

Oops, you're right, thanks.
Title: Re: VASIMR Engine
Post by: Nilof on 03/05/2015 12:13 PM
I had been trying to find the numbers on the MegaROSA and how it compared with original ROSA, I had thought the power density was much lower around 150W/kg for ROSA and couldn't find a number for MegaROSA, your link doesn't seem to have a reference to power density though, do you have one that dose?

You can get the power output per square meter in the link I gave in my earlier post:
http://www.nasa.gov/offices/oct/home/feature_sas.html

where power output and exact dimensions of the wing are given. For mass, there is this official figure (http://www.dss-space.com/pdf/nasa_tech_brief_fact_mega-rosa_solarosa_110112.pdf) of 200-400W/kg BOL at the wing level depending on the particular blanket technology used.

The 2 MW KSP example ship I showed earlier has arrays based on the MEGAROSA with correct sizes and a pessimistic 180 W/kg power density at the wing sixpack level. Each of the sixteen arrays on the booms are packs of six 20 kW winglets. So sizes are correctly accounted for making it a good way to get a rough idea of the relative sizes of the solar arrays.
Title: Re: VASIMR Engine
Post by: jgreason on 03/05/2015 12:39 PM
While I won't speak to this specific design, more generally I am quite convinced that thin film solar approaches at 1 kW/kg are definitely possible near term.  However there is very little serious work going on, and packaging such systems for launch and then deploying them without spoiling the mass is not at all trivial

But do keep thinking -- it is not crazy, at least at 1kW/kg rather than two

Thin film solar is extremely fragile, however, so the packaging is really challenging.
Title: Re: VASIMR Engine
Post by: tea monster on 03/05/2015 02:40 PM
I was thinking that this would be an excellent case for a Lagrange point 'Gateway Station'. You could set up a station there with a propellent depot and a manipulator telerobot. If the Telerobot was good enough, you may not even have to have the station permanently manned.

Ships and probes to the planets could be boosted directly there from Earth on launch and could go through check out at the station before boosting to their outbound destinations. Any unpacking or assembly would take place at the station with manipulator arms, and in a worse case scenario, a ship with a fault could be repaired by humans before it boosted off to Mars. It would eliminate tom-foolery like what happened to the Gallileo probe's antenna. A large chunk of the station's cost could be recouped by saving one flagship probe project from a post-launch glitch.
Title: Re: VASIMR Engine
Post by: Chris Bergin on 03/05/2015 02:45 PM
Big welcome to the site's forum to Mr. Greason, two posts back!

I was thinking that this would be an excellent case for a Lagrange point 'Gateway Station'. You could set up a station there with a propellent depot and a manipulator telerobot. If the Telerobot was good enough, you may not even have to have the station permanently manned.


Gateway you say? :)

http://www.nasaspaceflight.com/tag/gateway/
Title: Re: VASIMR Engine
Post by: Burninate on 03/05/2015 10:32 PM
No your still completely backwards, ISP and thrust are inversely proportional, the high ISP range is thus the low thrust range.  HALL is low to medium ISP, VASMIR is medium to high ISP.
This is an insufficient statement. Isp and thrust are not inversely proportional.  They are inversely proportional given fixed propulsive power (propulsive power being the product of propulsive thermal efficiency and actual system power).  Doubling Isp while keeping mass flow constant, doubles thrust but it increases the kinetic energy of the rocket exhaust per second, the propulsive power, by a factor of 4.  With double Isp but fixed propulsive power, you need to cut mass flow by a factor of four and thus cut thrust in half.

You cannot assume across technologies, however, that propulsive thermal efficiency will be the same, and system power is an arbitrary variable set by the engineers in designing the scale of the device.

PS: For people not doused in the terminology, Isp is simply a constant (1/9.81m/s^2) multiplied by the exhaust velocity
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 10:38 PM
Propulsive efficiency is roughly the same, though. You may be comparing 60% to 80% efficiency, but a 2000s vs 3500s Isp.
Title: Re: VASIMR Engine
Post by: Solman on 03/05/2015 10:42 PM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

It's not rigid? How will you keep the surface perpendicular to the sun's rays?
...
It doesn't HAVE to be perfectly rigid. If you're off by a few degrees, there's only incredibly slight reduction in power. And it is deployed, so launch harmonics isn't a concern.

This is different from a traditional antenna or a concentrating solar array which DO have to be rigid because of their high pointing requirements (phased array antenna can compensate for this).
I would think the concern would be thermally induced occilation. Parts of the array that are a few degrees off would be cooler than those that aren't. Might this not result in disaster if there is no means such as actuators to keep harmonic flexing from increasing like the Hubble arrays demonstrated?
The inference seems to be that concentrators need so much greater rigidity that their more than an order of magnitude advantage (as demonstrated by the L'Garde prototype) would somehow be eaten up by added structure. This makes no sense to me.   
Title: Re: VASIMR Engine
Post by: Burninate on 03/05/2015 10:49 PM
Big welcome to the site's forum to Mr. Greason, two posts back!

I was thinking that this would be an excellent case for a Lagrange point 'Gateway Station'. You could set up a station there with a propellent depot and a manipulator telerobot. If the Telerobot was good enough, you may not even have to have the station permanently manned.


Gateway you say? :)

http://www.nasaspaceflight.com/tag/gateway/

Always nice to have more industry figures around.

On the gateway: There are two main plans on this line of thinking that I've come to, which involve spiralling out, then leaving.  One relies on L2 for parking, a chemical kick to lower periapsis to Earth, and another chemical kick to escape Earth.  The second relies on some distant Earth orbit that isn't in close proximity to Luna, then a solar-electric thrust to lower periapsis to Earth, and a chemical kick to escape Earth.  This second cuts propellant usage substantially, but has departure windows that are orbital+synodic instead of monthly+synodic, and does not offer an orbital location that is reusable across synods, as far as I can tell: One departure mission, one station.
Title: Re: VASIMR Engine
Post by: Solman on 03/05/2015 11:06 PM
Why would you characterize IKAROS as speculative? It already flew.

A fairer suggestion would be that it is an unorthodox space structure due to its very low stiffness, and thus would require more care than usual for designing your spacecraft correctly, but I don't believe "speculative" makes sense, there.

...and I'm sorry for jumping on that word (when in all likelihood we're in violent agreement), I just think it's an important distinction to make.

People have been testing (and preparing for launch) solar sail craft for a while, now. An IKAROS-esque solar array would be no more speculative than that sort of structure. Clearly wouldn't be characterized as fantasy.

I think we are generally in agreement, while IKAROS has flown the power system your extrapolating at 1 kw/kg is 'derived' from it and has some significant engineering challenges when being scaled up to the size (multiple MW) that would be the kind of total power needs that would be desired, demonstrating scale is a big part of making the specific power number relevant for SEP.  So I'm simply calling any specific power density goal which is not the design goal to a current development program a 'speculative' one. 

Essentially I assume all current development programs that are just refining current tech will meat their goals (admittedly optimistic) but anything outside of a program has some chance of not being delivered upon and thus is a 'speculation'.  Naturally their are huge ranges between very likely to be delivered upon and very unlikely to be delivered upon speculative systems.  When the speculation exceeds what even the best known materials or some very obvious thermodynamic or practicality limits then I'd call it fantasy, and I'd say that when it comes to solar power density the >2kw/kg can be called fantasy, 250W-2kw can be called speculative, and <250W/kg can be taken to the bank.

I had been trying to find the numbers on the MegaROSA and how it compared with original ROSA, I had thought the power density was much lower around 150W/kg for ROSA and couldn't find a number for MegaROSA, your link doesn't seem to have a reference to power density though, do you have one that dose?

 Speaking of numbers I would say that an extraordinary claim such as >2kwe/kg for solar exceeds material or thermodynamic limits requires extraordinary proof or at the very least some numbers.
The concentrator I'm describing has been built after all.
I think people have failed to wrap their heads around the implications of having available solar cells that can exceed 40% efficiency at 900 Suns. These cells have very low mass per unit power produced and higher efficiency than any thin film cells. This efficiency means that the concentrator would be much smaller in area than a thin film array and so can have a more massive structure per unit area and still have much lower total mass per power produced. This added to the lower mass per area of reflective film as compared to thin film cells and the conducting wires they require, makes a solid case for concentrator's superiority IMO. Oh and the support structure of aluminum tubes can provide the needed radiator area at little mass penalty.
If the argument being made is that unless a tech is currently being developed it is fantasy then this tech which uses already developed parts in a new combination is no more a fantasy than any system using VASIMR is it?
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/05/2015 11:13 PM
Here is the solar array, it's from the Airforce and is called RAPDAR (Roll-out And Passively Deployed Array).

It appears to be is a thin-film solar membrane on a memory shape material that unrolls in the warmth of the sun.

It's not rigid? How will you keep the surface perpendicular to the sun's rays?
...
It doesn't HAVE to be perfectly rigid. If you're off by a few degrees, there's only incredibly slight reduction in power. And it is deployed, so launch harmonics isn't a concern.

This is different from a traditional antenna or a concentrating solar array which DO have to be rigid because of their high pointing requirements (phased array antenna can compensate for this).
I would think the concern would be thermally induced occilation. Parts of the array that are a few degrees off would be cooler than those that aren't. Might this not result in disaster if there is no means such as actuators to keep harmonic flexing from increasing like the Hubble arrays demonstrated?
The inference seems to be that concentrators need so much greater rigidity that their more than an order of magnitude advantage (as demonstrated by the L'Garde prototype) would somehow be eaten up by added structure. This makes no sense to me.

Makes no sense to you or not, it's true. Stiffness costs mass. And, in fact, a LOT of aerospace structures are stiffness-limited (due to pointing requirements or launch requirements), and "specific modulus" is a useful figure-of-merit in those cases.

And yes, there are ways to damp out larger oscillations. Besides, Hubble is a space telescope so necessarily has high pointing requirements, making low-stiffness arrays a poor choice anyway.
Title: Re: VASIMR Engine
Post by: Solman on 03/06/2015 12:27 AM
 Thanks for the response Chris, but the point I was attempting to make is that the difference in the mass to achieve the structural stiffness required to prevent thermally induced movements or the mass of actuators to damp them out as they arise reduces any difference in mass per unit area that might be required for a concentrator vs. thin film - perhaps to zero.
That when added to the much smaller size required for the concentrator per unit power owing to the higher efficiency of concentrator type PV(about 4X higher at present) and the lower mass/area of reflective material vs. thin film cells should result in a much higher overall specific power for the concentrator system.
Title: Re: VASIMR Engine
Post by: Impaler on 03/06/2015 01:41 AM
This second cuts propellant usage substantially, but has departure windows that are orbital+synodic instead of monthly+synodic, and does not offer an orbital location that is reusable across synods, as far as I can tell: One departure mission, one station.

While I am skeptical that SEP would remotely benefit from a periapsis drop and kick-stage burn (better to use the propellent mass in the SEP system normally).  This departure timing dose not seem too hard to overcome, the low DeltaV window for transit for a conventional rocket is nearly a month long so we should be able to consistently get a departure, though admittedly it is an instantaneous window which can be dicy.  Also depending on which side of the Earth we go around we have two possible exit trajectories which are rotating around so one should be passing any desired direction every 15 days if they are equally spaced (no clue if they are).
Title: Re: VASIMR Engine
Post by: Burninate on 03/06/2015 03:27 AM
This second cuts propellant usage substantially, but has departure windows that are orbital+synodic instead of monthly+synodic, and does not offer an orbital location that is reusable across synods, as far as I can tell: One departure mission, one station.

While I am skeptical that SEP would remotely benefit from a periapsis drop and kick-stage burn (better to use the propellent mass in the SEP system normally).  This departure timing dose not seem too hard to overcome, the low DeltaV window for transit for a conventional rocket is nearly a month long so we should be able to consistently get a departure, though admittedly it is an instantaneous window which can be dicy.  Also depending on which side of the Earth we go around we have two possible exit trajectories which are rotating around so one should be passing any desired direction every 15 days if they are equally spaced (no clue if they are).

The distinction is between 1) a periapsis drop from L2 using chemical and then an Oberth departure burn using chemical, and 2) A periapsis drop from high circular orbit using SEP and then an Oberth departure burn using chemical.  The distinction exists because I think the complex dynamics of the orbit around the Lagrange point may pose problems for a pure SEP periapsis drop at low thrust, while a non-EML orbit can perform this maneuver at leisure over as many orbits as required;  I'm not sure 100% this is a big deal.
Title: Re: VASIMR Engine
Post by: Nilof on 03/06/2015 09:46 AM
The utillity of a kick stage really depends on how strong your SEP acceleration is. In the 1 mm/s/s range, a departure from a lunar altitude orbit would more or less look impulsive.

So the question is, is the kick stage going to provide more delta-v per reaction mass using the Oberth effect at 300s Isp than the SEP system at 3000+ seconds Isp?
Title: Re: VASIMR Engine
Post by: Impaler on 03/06/2015 06:50 PM
Yes that's my point Oberth is good but it's not going to close that kind of ISP gap.

To crunch the numbers we need to know C3 at EML1/2 (they are approximately the same are they not).  And then determine our target C3 for the Mars trajectory for the kick stage to achieve and then look at what it costs the SEP to match that all by itself.

When I look at this idea to provide propellent at EML1/2 from some elaborate mining operation I just don't see any practicality.  The Oberth effect from the drop is all just potential energy conversion to get your velocity up as you swing by the Earth and your going about 3 kms faster then orbital speed.  But I could simply have had a big booster starting in LEO accelerate me thouse 3 kms and then drop off the back of my vehicle.  Now my remaining vehicle is traveling 3 kms in excess of orbital velocity and is interchangeable with and gets every bit of Oberth benefit for the remaining escape burn (how ever large or small it may be) as someone coming from EML1.

The booster would need to have a mass equal to the whole rest of the vehicle it was pushing (I'm assuming HydroLox 450 ISP) yes so it is a big booster, but this one big booster just substituted for the entire in-space propellent production, the need to send my payload up to EML1 rendezvous with some station, refuel it etc etc.  The simplification is enormous and it establishes a cap on the value of EML1 propellent mass, it's worth at most twice what LEO propellent is worth even if we ignore every operational difficulty in using it.  So our in-space production process can cost no more then twice what our launch costs are. 

The higher my ISP goes the more this multiplier is reduced, say I had something like a NTR, doubling the ISP, now the throw away LEO booster is only 30% of the mass of the rest of the vehicle.  So EML1/2 propellents are now worth only 1.3 times LEO propellents.
Title: Re: VASIMR Engine
Post by: Nilof on 03/06/2015 07:06 PM
I think the main value of ISRU propellant in lunar orbit/EML is for transportation in for transportation in cislunar space and lunar landings. With magnetoshell areobraking you could have a "fetcher" craft that brakes down to LEO, docks with a payload, and goes back up to lunar orbit with the payload. For lunar exploration you can similarly have a fully reusable lunar lander that runs on ISRU propellant.

This can enable very cheap access to the moon, where the only launching needed is a commercial resupply and a commercial crew equivalent.

For Mars, while a mature cislunar infrastructure can certainly help, I think a pure SEP craft is probably the more practical option.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/09/2015 03:53 PM
A rough approximate figure from the phase I ROSA winglets (http://www.nasa.gov/offices/oct/home/feature_sas.html) is ~3 square meter per kW.

I don't know if this is the same RAPDAR stuff impaler is talking about. But I'll go with it.

So about 12000 square meters to provide 4 megawatts? If my arithmetic's right that's about 4 times the total area of the ISS Solar Array Wings (SAWs).

I seem to recall Impaler say the solar cells he envisions are about the thickness of the plastic in milk jugs. How about the supporting structure? Is the mast about the thickness of a coat hanger?

The ISS demonstrates it's doable to rotate the SAWs each orbit to keep them pointed towards the sun. And if the ion driven Mars Transfer Vehicle is in the ecliptic plane, there's no need for a beta gimbal.

To minimize aerodynamic drag the ISS SAWs will go into Night Glider mode (http://en.wikipedia.org/wiki/Night_Glider_mode).  Our MTV seems to have a mass less than half the I.S.S. but a cross sectional area 4 times greater. At 400 km altitude, the MTV would have aerodynamic deceleration about Eight times what the I.S.S. endures.

Delta V for low thrust spirals is about the difference in the speeds between departure and destination orbits. The difference between a 7.7 km/s LEO and 3.07 km/s GEO is about 4.6 km/s. At a millimeter per second^2 acceleration, it takes 11.6 days to accelerate 1 km/s. So I get 53 days to spiral from LEO to GEO. But 10% of that is in earth's shadow. So More like 60 days.

(http://clowder.net/hop/TMI/LeoToGeoIonSpiral.png)

To avoid subjecting the passengers to long periods of high radiation, Impaler has suggested a chemical ferry take the astronauts to GEO where they can rendezvous with the MTV after it's passed through the Van Allen Belts.

Besides a two month trip through the Van Allen Belts this is also a 60 day spiral through the LEO and GEO orbital debris with a 12000 square meter cross section. Impaler's GEO rendezvous scheme spares the human passengers but the MTV is still subjected to some wear and tear.


Title: Re: VASIMR Engine
Post by: Hop_David on 03/09/2015 04:53 PM
Why would you characterize IKAROS as speculative? It already flew.

Sunlight's power density at Venus is more than double than at 1 A.U.

And at 1.52 A.U. Mars distance, it's less than half, more like 2/5.

So I don't know how applicable Ikaros' 1 kWe/kg is to solar arrays on an MTV.

Also at perihelion from an earth to Venus Hohmann, the mast need only move at 2 degrees per day to stay aligned with the sun. In LEO a mast would need to move 4 degrees per minute.

Title: Re: VASIMR Engine
Post by: Robotbeat on 03/10/2015 01:01 AM
Why would you characterize IKAROS as speculative? It already flew.

Sunlight's power density at Venus is more than double than at 1 A.U.

And at 1.52 A.U. Mars distance, it's less than half, more like 2/5.

So I don't know how applicable Ikaros' 1 kWe/kg is to solar arrays on an MTV.

Also at perihelion from an earth to Venus Hohmann, the mast need only move at 2 degrees per day to stay aligned with the sun. In LEO a mast would need to move 4 degrees per minute.
Nah, the 1kWe/kg was calculated (by me, just so we're clear...) assuming 1 AU, not Venus' orbit.

And yeah, the mast for a solar array would not be a "coat hanger" thick, but the components would! Like a solar sail structure.
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/10/2015 01:08 AM
I.e. this sort of thing, but with very thin solar cells operating at high voltage:

https://www.youtube.com/watch?v=4F97NdwvmUM

(The mass of that thing is just 20kg for 1000 m^2 of area... solar cells would add to the weight as would the thruster, but that can be calculated in a relatively straightforward manner.)
Title: Re: VASIMR Engine
Post by: Nilof on 03/10/2015 10:04 AM
I.e. this sort of thing, but with very thin solar cells operating at high voltage:

https://www.youtube.com/watch?v=4F97NdwvmUM

(The mass of that thing is just 20kg for 1000 m^2 of area... solar cells would add to the weight as would the thruster, but that can be calculated in a relatively straightforward manner.)

There are a few issues with non-stiff structures though. For example, how do you dock with a spacecraft like this one? How do you do quickly change thrust direction during an approach maneuver?

The cost of stiffness can be reduced dramatically with in-space construction of trusses, so I'm not convinced that abandoning stiff structures is necessarily the best way to go about things.
Title: Re: VASIMR Engine
Post by: Hop_David on 03/10/2015 03:52 PM
Nah, the 1kWe/kg was calculated (by me, just so we're clear...) assuming 1 AU, not Venus' orbit.

I'd like to see these calculations.

The solar sail material in that vid is 3 microns thick. Seran Wrap's 12 microns.
Title: Re: VASIMR Engine
Post by: cdleonard on 03/11/2015 12:31 PM
Plans to test VASIMR on ISS apparently cancelled. Paywalled source: http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 03/11/2015 01:19 PM
Plans to test VASIMR on ISS apparently cancelled. Paywalled source: http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station

Either kill the VASIMR or find a way to attach it and solar panes to a spacecraft. Since they have navigation and RCS a Dragon or Cygnus would do nicely.
Title: Re: VASIMR Engine
Post by: Nilof on 03/11/2015 02:55 PM
Plans to test VASIMR on ISS apparently cancelled. Paywalled source: http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station

Either kill the VASIMR or find a way to attach it and solar panes to a spacecraft. Since they have navigation and RCS a Dragon or Cygnus would do nicely.

This has been discussed before. The Dragon is simply way too underpowered to test a full VASIMR system. The new Cygnus will have ultraflex arrays though, so there may be a chance that it can be equipped with ultraflex megaflex arrays for the test and later BEO servicing missions(waiting for Jim to correct me).
Title: Re: VASIMR Engine
Post by: Robotbeat on 03/11/2015 03:21 PM
Use batteries. Plenty of power, then.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 03/11/2015 08:36 PM
Plans to test VASIMR on ISS apparently cancelled. Paywalled source: http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station

Either kill the VASIMR or find a way to attach it and solar panes to a spacecraft. Since they have navigation and RCS a Dragon or Cygnus would do nicely.

This has been discussed before. The Dragon is simply way too underpowered to test a full VASIMR system. The new Cygnus will have ultraflex arrays though, so there may be a chance that it can be equipped with ultraflex arrays for the test and later BEO servicing missions(waiting for Jim to correct me).

The VASIMR will have to bring its own 200kW solar panels. Borrowing the ISS's solar panels for an experiment was a nice idea but did not work.
Title: Re: VASIMR Engine
Post by: guckyfan on 03/11/2015 08:54 PM
Use batteries. Plenty of power, then.

That was the plan for the ISS. Should work with Dragon or Cygnus too.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 03/11/2015 09:29 PM
Does anyone want to flight test any 200kW solar panels?
Title: Re: VASIMR Engine
Post by: nadreck on 03/11/2015 09:36 PM
Does anyone want to flight test any 200kW solar panels?

There might be some synergy between this and a couple of other threads discussing gating technology.  I propose that some gets me the thin film solar panels we were discussing for ISRU propellant stuff on Mars. Then someone else can arrange a ride for me on an early prototype D2 (with a fair bit of extra life support).  Someone else needs to get me a working EVA suit that can fit through one of the two hatches on  a D2.  Oh, and hey and lets test I can switch between suits and that the D2 is depresurization/represurization friendly before we go.  Anyway, I figure we mount the Vasimir on the aft end of the trunk and I try to fly it to the moon and back. I just need people to arrange all the stuff and help me develop the deployment plan, oh, and some ground support and guidance help would be nice.
Title: Re: VASIMR Engine
Post by: Raj2014 on 03/11/2015 10:52 PM
Found this web page on VASIMR (https://ukti.blog.gov.uk/2015/03/06/british-expertise-helps-the-us-and-costa-rica-into-the-forefront-of-space-innovation/).
Title: Re: VASIMR Engine
Post by: Burninate on 03/12/2015 12:05 AM
Plans to test VASIMR on ISS apparently cancelled. Paywalled source: http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station

Can anyone excerpt more detail from this?
Title: Re: VASIMR Engine
Post by: Raj2014 on 03/31/2015 06:09 PM
Has there been any new news on VASIMR? All I could find still was the ISS VASIMR cancelled.
Title: Re: VASIMR Engine
Post by: philw1776 on 03/31/2015 07:01 PM
Has there been any new news on VASIMR? All I could find still was the ISS VASIMR cancelled.

It's dead, Jim.
Title: Re: VASIMR Engine
Post by: TrevorMonty on 03/31/2015 07:29 PM
It may not be dead. Ad Astra are still receiving funding from NASA.

http://www.parabolicarc.com/2015/03/30/nasa-announces-12-nextstep-partnerships/
Title: Re: VASIMR Engine
Post by: QuantumG on 03/31/2015 10:58 PM
Here's the press release.

http://adastrarocket.com/AdAstraRelease033115final.pdf

$10M, more lab tests.

Title: Re: VASIMR Engine
Post by: Nilof on 03/31/2015 11:40 PM
...and here's the NASA announcement. Apparently MSNW also got a contract.
Title: Re: VASIMR Engine
Post by: momerathe on 04/01/2015 08:30 AM
Feels like a consolation prize to me, compared to the ISS test.
Title: Re: VASIMR Engine
Post by: Star One on 04/01/2015 08:38 AM

Feels like a consolation prize to me, compared to the ISS test.

But it does rather prove wrong those declaring its death.
Title: Re: VASIMR Engine
Post by: QuantumG on 04/01/2015 10:41 AM
But it does rather prove wrong those declaring its death.

You mean Ad Astra? Just seems like their call for public support worked.
Title: Re: VASIMR Engine
Post by: Star One on 04/01/2015 11:40 AM

But it does rather prove wrong those declaring its death.

You mean Ad Astra? Just seems like their call for public support worked.

Both the company & the technology I suppose.
Title: Re: VASIMR Engine
Post by: momerathe on 04/01/2015 11:47 AM
It's hard to know how to interpret it. It could be "we don't have the budget/will to put it on the ISS, but here's a bone to tide you over", or "you're not ready for prime time... yet".
Title: Re: VASIMR Engine
Post by: QuantumG on 04/01/2015 12:16 PM
There was never an agreement to put it on the ISS. It was just an aspiration.

Title: Re: VASIMR Engine
Post by: Raj2014 on 04/01/2015 04:56 PM
It may not be dead. Ad Astra are still receiving funding from NASA.

http://www.parabolicarc.com/2015/03/30/nasa-announces-12-nextstep-partnerships/

I am reading this right now, it recently posted on facebook. It is from the NASA (http://www.nasa.gov/press/2015/march/nasa-announces-new-partnerships-with-us-industry-for-key-deep-space-capabilities/#.VRwh-vnF95F) website.
Title: Re: VASIMR Engine
Post by: JasonAW3 on 04/01/2015 05:16 PM
The question I have is pretty simple;

How efficent is the VASMIR compared to;

1) Chemical Rockets (Duh!  pretty good I imagine, but not booster material).
2) Basic NERVA rocket engine (Solid core or gaseous.  Similar figures as I understand it)
3) Ion drives (Slow as heck, but REALLY good for continious thrust)
4) Solar Electric Propulsion (Pretty much the same as the Ion Drive, I imagine.  But I'm likely wrong on this point)

One of the major advantages VASMIR has over NERVA is mass.  Whether or not a Thorium based NERVA is possible is problematic at best, as a Thorium reaction requires far less shielding than a standard nuclear reactor, although I suspect it would still be pretty massive.

Overall; How much fuel does each use to get to speed?  How long does it take to build up enough velocity to escape Earth's gravity well? Can they run continiously for a fair acceleration?  And what are the advantages and disadvantages for each versus a manned space flight.

     The Vasmir seems to have an advantage over pretty much all of these designs, but I'd like a bit better comparison if anyone knows.

    BTW; Chemical rockets were only included for this question to provide a baseline for comparison.
Title: Re: VASIMR Engine
Post by: Raj2014 on 04/01/2015 05:30 PM
The question I have is pretty simple;

How efficent is the VASMIR compared to;

1) Chemical Rockets (Duh!  pretty good I imagine, but not booster material).
2) Basic NERVA rocket engine (Solid core or gaseous.  Similar figures as I understand it)
3) Ion drives (Slow as heck, but REALLY good for continious thrust)
4) Solar Electric Propulsion (Pretty much the same as the Ion Drive, I imagine.  But I'm likely wrong on this point)

One of the major advantages VASMIR has over NERVA is mass.  Whether or not a Thorium based NERVA is possible is problematic at best, as a Thorium reaction requires far less shielding than a standard nuclear reactor, although I suspect it would still be pretty massive.

Overall; How much fuel does each use to get to speed?  How long does it take to build up enough velocity to escape Earth's gravity well? Can they run continiously for a fair acceleration?  And what are the advantages and disadvantages for each versus a manned space flight.

     The Vasmir seems to have an advantage over pretty much all of these designs, but I'd like a bit better comparison if anyone knows.

    BTW; Chemical rockets were only included for this question to provide a baseline for comparison.

What I know about VASIMR (http://www.adastrarocket.com/aarc/VASIMR) is that it is a electric propulsion, which use plasma to produce thrust. I think it can produce 5N of thruster with a specific impulse of 5000s+. It can produce an exhaust velocity of 180,000 KPH. Has no electrodes, which it can last longer. Can be scaled up. Use different types of fuel, Argon is the best apparently. Can switch mode, for more velocity or go longer distance. Reduced mass.  More information here, on the FAQ (http://www.adastrarocket.com/aarc/FAQ) section. 
Title: Re: VASIMR Engine
Post by: Elmar Moelzer on 04/01/2015 06:29 PM
Well, you always have to add the mass of the power source to VASIMIR. Hopefully solar panels get more efficient.
Title: Re: VASIMR Engine
Post by: Star One on 04/01/2015 06:45 PM
For a layman what is proving the main obstacle in developing it to a usable state, is it purely technological issues or a matter of funding?
Title: Re: VASIMR Engine
Post by: Nilof on 04/01/2015 09:40 PM
For a layman what is proving the main obstacle in developing it to a usable state, is it purely technological issues or a matter of funding?

The long term business case is certainly iffy. VASIMR's stats looked impressive compared to grid ion, electrothermal thrusters and early Halls, but it has a much harder time competing against more recent Hall thrusters. The erosion issues of Halls have been more or less solved and they can now reach Isp's in the 4000s range while also being more lightweight and far more compact.

The niche of being the new "most high tech" technology on the block is also gone, and that niche now belongs to MSNW's ELF thrusters. Regarding variable Isp, most advanced SEP proposals(such as concentric halls) do have that so it isn't unique to VASIMR.
Title: Re: VASIMR Engine
Post by: Robotbeat on 04/02/2015 12:08 AM
VASIMR is mostly the same as other electric propulsion technologies, though it doesn't scale down very well so you kind of need to have hundreds of kilowatts to run it effectively. It does have some interesting aspects, but mostly it's the same sort of trade-offs as other electric propulsion tech (mostly gridded ion and hall thrusters).
Title: Re: VASIMR Engine
Post by: Robotbeat on 04/02/2015 12:10 AM
For a layman what is proving the main obstacle in developing it to a usable state, is it purely technological issues or a matter of funding?
Part of the issue is the fact is that it doesn't scale down very well to fit on commercial satellites, and it's really not that different from existing electric propulsion tech even if it could.

Also, it pretty much requires superconductors to run, which makes it kind of expensive and more complicated than other types of electric propulsion.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 04/02/2015 05:04 AM
If the VASIMR is not going on the ISS then it needs putting on a medium sized spacecraft. Something with 200 kW of solar power, an RCS, navigation and a dummy payload.

To get a 100 hour burn out of the VASIMR Ad Astra will have to invent a vacuum chamber able to handle gas at 1,000,000 degrees for 100 hours.
Title: Re: VASIMR Engine
Post by: Star One on 04/02/2015 06:39 AM
For a layman what is proving the main obstacle in developing it to a usable state, is it purely technological issues or a matter of funding?
Part of the issue is the fact is that it doesn't scale down very well to fit on commercial satellites, and it's really not that different from existing electric propulsion tech even if it could.

Also, it pretty much requires superconductors to run, which makes it kind of expensive and more complicated than other types of electric propulsion.

So could it be argued that it's a technology that's already been surpassed by others in the field, or is that not a fair summation. If it is the case it has been surpassed you have to wonder if this funding will take it anywhere.
Title: Re: VASIMR Engine
Post by: Raj2014 on 04/02/2015 08:17 AM
If the VASIMR is not going on the ISS then it needs putting on a medium sized spacecraft. Something with 200 kW of solar power, an RCS, navigation and a dummy payload.

To get a 100 hour burn out of the VASIMR Ad Astra will have to invent a vacuum chamber able to handle gas at 1,000,000 degrees for 100 hours.

That is what I have been saying for a while, either do both, ISS and spacecraft or spacecraft, if they have the funding. Have it go around the Earth and Moon or longer distance. Also have an chemical rocket, lightweight, which can bring the spacecraft back in case the something goes wrong with VASIMR or something else.   
Title: Re: VASIMR Engine
Post by: Nilof on 04/02/2015 12:43 PM
VASIMR's main advantage as I see it is that it can work at much higher Isps than Halls, while having a higher power density than grid ion engines which have inherent limitations. The main issue is that you need to go further out than Mars to justify running it at higher Isp. In theory it would be the best current candidate for reaching objects in the asteroid belt with extreme inclinations to the ecliptic(where variable Isp is also quite useful), or for large outer planets missions.

With that said, by the time ELF thrusters advance enough in TRL level they should be capable of doing that even better. So Ad Astra needs to move fairly quickly if they want to capitalize on the niches they still have.
Title: Re: VASIMR Engine
Post by: aceshigh on 04/02/2015 10:09 PM
imho, VASIMR main challenge is to find it a power source that can provide 200 MW and be light enough at the same time, to reach Mars in 40 days.

Aside that, it´s not much different than other electric propulsion schemes.
Title: Re: VASIMR Engine
Post by: Asteroza on 04/02/2015 11:29 PM
VASIMR's appeal to me is the conceptual compatibility with multiple propellant gases, and the possibility that with a suitable helicon design the engine itself might actually be multifuel. If a PROFAC style system is actively harvesting nitrogen from LEO/VLEO, VASIMR can use it. Most other electric thrusters consume rare noble gases or other oddball propellants, which are harder to come by from ISRU systems in bulk.
Title: Re: VASIMR Engine
Post by: Impaler on 04/03/2015 06:04 AM
ELF can digest any propellent that VASIMR can, and HALLS can run on a just about anything too so long as it some Nobles are sprinkled in to kick-start the ionization process.  The only tech that is inherently limited in propellent types is the Gridded Ion thruster.

Currently everyone would WANT to use Nobles in nearly all current applications even if the thruster could use lighter mass propellents because Nobles yield low ISP and high thrust.  If we were trying to get to Mars with VASIMR we would be best off putting Xenon in it too.
Title: Re: VASIMR Engine
Post by: spacenut on 04/06/2015 04:13 PM
How would VASIMR scale to say hauling 100 tons of cargo to Mars?  How large would the solar panel area be for such a ship?  How fast could it make the transfer? 
Title: Re: VASIMR Engine
Post by: catdlr on 04/06/2015 09:32 PM
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Title: Re: VASIMR Engine
Post by: Star One on 04/06/2015 09:45 PM
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Why is it that Zubrin seems to have taken personal umbrage with this technology?
Title: Re: VASIMR Engine
Post by: QuantumG on 04/06/2015 10:03 PM
Why is it that Zubrin seems to have taken personal umbrage with this technology?

The current NASA administration sees electric propulsion as a gatekeeper technology to sending humans to Mars and Bob doesn't agree. VASIMR is the easy target for attacking electric propulsion as they continue to make absurd claims.
Title: Re: VASIMR Engine
Post by: tchernik on 04/06/2015 10:25 PM
Why is it that Zubrin seems to have taken personal umbrage with this technology?

The current NASA administration sees electric propulsion as a gatekeeper technology to sending humans to Mars and Bob doesn't agree. VASIMR is the easy target for attacking electric propulsion as they continue to make absurd claims.

I'm an ignorant person from the Internet, so I better ask: do you have a link to a comment or an overview of the absurd claims you refer?
Title: Re: VASIMR Engine
Post by: Jimmy Murdok on 04/06/2015 10:56 PM
I'm an ignorant person from the Internet, so I better ask: do you have a link to a comment or an overview of the absurd claims you refer?

The article above is a good example. There is actually no practical way to produce the huge ammount of energy required for this short trip. If I'm not wrong for something like 100T you would need a power source around 200 megawatt.
The most efficient and practical way to obtain this energy is solar.  The ISS USA solar panels produce 130kW so you would need around 1500 times what ISS have to be able to power that engine. But then the solar panels would weight a lot as well and be a monstruous headache.

Basially electric propulsion even if it can produce a lot of thrust will always need huge ammounts of power, so now is quite limitted to slow satellites and could be a good complement for crewed trips.
Title: Re: VASIMR Engine
Post by: QuantumG on 04/06/2015 10:58 PM
I'm an ignorant person from the Internet, so I better ask: do you have a link to a comment or an overview of the absurd claims you refer?

www.adastrarocket.com/AandS_July_2006_UCD.pdf
www.adastrarocket.com/VASIMR_for_flexible_space_exploration.pdf
www.adastrarocket.com/Andrew-SPESIF-2011.pdf
www.adastrarocket.com/CW102spacefinal.pdf

.. and many many quotes in the press with the 39 day travel claim.

Is it an absurd claim? Why yes, I think so. In order for it to not be absurd you have to postulate the existence of an in-space nuclear reactor that simply doesn't exist and for which there's no development program. Ya might as well be talking about what the rocket could do if it was mounted on Santa's sleigh.
Title: Re: VASIMR Engine
Post by: Star One on 04/06/2015 11:49 PM
I'm an ignorant person from the Internet, so I better ask: do you have a link to a comment or an overview of the absurd claims you refer?

www.adastrarocket.com/AandS_July_2006_UCD.pdf
www.adastrarocket.com/VASIMR_for_flexible_space_exploration.pdf
www.adastrarocket.com/Andrew-SPESIF-2011.pdf
www.adastrarocket.com/CW102spacefinal.pdf

.. and many many quotes in the press with the 39 day travel claim.

Is it an absurd claim? Why yes, I think so. In order for it to not be absurd you have to postulate the existence of an in-space nuclear reactor that simply doesn't exist and for which there's no development program. Ya might as well be talking about what the rocket could do if it was mounted on Santa's sleigh.
While not wishing to get into a debate on this that might take this thread to far off topic it depends if you want to adopt that cynical approach to the future of power generation.
Title: Re: VASIMR Engine
Post by: QuantumG on 04/07/2015 12:13 AM
While not wishing to get into a debate on this that might take this thread to far off topic it depends if you want to adopt that cynical approach to the future of power generation.

It's not about cynicism. What it comes down to is whether you want to think about sending humans to Mars as "something that happens in the future", which typically means you always think about it that way, or whether you actually want to do it.
Title: Re: VASIMR Engine
Post by: Impaler on 04/07/2015 12:31 AM
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Why is it that Zubrin seems to have taken personal umbrage with this technology?

Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.
Title: Re: VASIMR Engine
Post by: Robotbeat on 04/07/2015 12:47 AM
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Why is it that Zubrin seems to have taken personal umbrage with this technology?

Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.
Which is actually quite odd, then, that he supports nuclear power but not solar electric propulsion, since solar-electric propulsion is FAR more mature (not to mention cheaper).
Title: Re: VASIMR Engine
Post by: QuantumG on 04/07/2015 12:52 AM
Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.

I don't think that's true. I think the objection here is that Bob and Frank both agree that space nuclear reactors are a good idea but that's not what NASA is working on. It's cart before the horse, and in this case they're advertising the cart as being super-fast when pulled by a unicorn.
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/07/2015 02:37 AM
erm; why does NASA got to do it? I have seen articles that say two or three big companies are ready to make, not design, make mini reactors that are self contained, no maintenance, safe, small and light and that would only cost a few million apiece. That's fission.

Next LM and well as at least a half a dozen other companies are working on fusion with at least three of those ready to put up or shut up about it.

Why does NASA need to do anything more than buy one of those fission reactors from either  the Japanese or GE and pimp slap the normal government regulatory crap out of the way? Tell the EPA that the whole lot of them can stop emitting Co2 at their earliest convenience. Same thing for the DOE and anyone else that wants to be their usual helpful selves.
Title: Re: VASIMR Engine
Post by: Tetrakis on 04/07/2015 03:06 AM
1. Ready to make? Advertised the possibility of making, yes. Actually deploying in the immediate future, no.

2. Reactors designed for use on earth can't just be launched into orbit. All coolant has to be actively pumped, waste heat has to be expensively removed (there is no river of cold water next to the reactor in space).
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/07/2015 03:17 AM
these are reactors of advanced design from garbage can sized to small CONEX sized. I think there were two Japanese companies offering them and also GE said they had one. I don't see how a garbage can sized reactor needs a river by it.

This is one of the various mini reactors I have read about in recent years:

http://www.ft.com/cms/s/0/22c1b17a-1f71-11e0-87ca-00144feab49a.html#axzz3WaeylOlG

It uses molten lead and bismuth as a coolant and I'd wager as radiation shielding too. Still... it says the ancilliary equipment takes up an acre. But that is for turbines and the like. What about thermo-electric converters?

and there were others.

http://en.wikipedia.org/wiki/Toshiba_4S

and there are still more.
Title: Re: VASIMR Engine
Post by: QuantumG on 04/07/2015 03:43 AM
Space reactors and ground reactors are not even slightly related. They don't even use the same fuel.
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/07/2015 03:44 AM
At the moment there isn't a such thing as a space reactor so how can you tell? :D
Title: Re: VASIMR Engine
Post by: QuantumG on 04/07/2015 03:45 AM
Of course there is.. ya know, when you're in a hole, you really should stop digging.
Title: Re: VASIMR Engine
Post by: Jimmy Murdok on 04/07/2015 03:46 AM
At the moment there isn't a such thing as a space reactor so how can you tell? :D

There are dozens of Russian reactors and few american ones that were launched to space between the 60's to late 80's.
Same discussion few days ago.
http://forum.nasaspaceflight.com/index.php?topic=36805.120
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/07/2015 03:53 AM
In that case then there are space rated nuclear reactors...so what were we arguing about again?  ;D
Title: Re: VASIMR Engine
Post by: Jimmy Murdok on 04/07/2015 05:30 AM
In that case then there are space rated nuclear reactors...so what were we arguing about again?  ;D
They did exist and russia is making the biggest one in history (1MW & 7T). But if you need 200MW  :o ... well no need to justify.
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/09/2015 04:31 AM
:)

http://www.sciencedaily.com/releases/2001/01/010103073253.htm

Title: Re: VASIMR Engine
Post by: Nilof on 04/09/2015 11:54 AM
:)

http://www.sciencedaily.com/releases/2001/01/010103073253.htm

That would require huge amounts of an exotic isomer of americium.

If that was available in the large quantities needed for a reactor, I think you'd be better off doing nuclear pulse propulsion instead. Though the possibility of a nuke in a hand-grenade form factor terrifies me as far as Earth applications are concerned.
Title: Re: VASIMR Engine
Post by: Stormbringer on 04/09/2015 01:53 PM
Yeah, that's the draw back with any type of advanced fission tech. At least fusion reactors aren't immediately a weaponization threat. Though anything that can approach relativistic speed or even just orbital speed is by default a terrible potential for misuse.
Title: Re: VASIMR Engine
Post by: nadreck on 04/09/2015 04:49 PM
Yeah, that's the draw back with any type of advanced fission tech. At least fusion reactors aren't immediately a weaponization threat. Though anything that can approach relativistic speed or even just orbital speed is by default a terrible potential for misuse.

Basically the higher the exhaust velocity, then the better weapon just the engine itself can make. Ion cannons are just ion engines pointed at someone ;-)
Title: Re: VASIMR Engine
Post by: Hanelyp on 04/09/2015 05:23 PM
That would require huge amounts of an exotic isomer of americium.

If that was available in the large quantities needed for a reactor, I think you'd be better off doing nuclear pulse propulsion instead. Though the possibility of a nuke in a hand-grenade form factor terrifies me as far as Earth applications are concerned.
My understanding is that the irreducible minimum quantity of nuclear material for a single bomb is about what you need for a reactor of some designs.  A steady state reactor needs cooling, which increases volume and fuel needed for a critical mass, but can use moderating reflectors which reduce the fuel needed.
Title: Re: VASIMR Engine
Post by: Kansan52 on 04/09/2015 06:13 PM
Solar Thermal. May still have the McDonnell Douglas glossy color handout of their space based, microwave beamed SPS from 1970's (if memory serves).

It was solar concentractor reflecting to a tube running the lenght of the reflector trough. It steamed mercury and ran a steam turbine. Dumped the excess heat, repeat. If the mass could be controlled, a trough along the length of the vehicle might accomplish the job.

3D solar cells. Didn't they test those on ISS (or are)? Basic idea is a layer that reflects the sunlight to the solar cell even at extreme angles.

BASP-Beamer. A big a** solar power station that beams the energy to the vehicle. This assumes the colectors for the beamed energy can be much smaller that solar panel.
Title: Re: VASIMR Engine
Post by: Hop_David on 05/07/2015 05:41 AM
OK lets keep going with this Hummer/Prius analogy, it is kind of amusing.

You're easily amused.

The flaw in your hill analogy is that EML1 is not the top of a hill, it is more like the lip of the grand canyon with the canyon being the Earths gravity well (it's not literally C3=0 but its very close).  Once your up on the plateau (heliocentric space) it is perfectly flat and the Prius is free to accelerate.  If you were going to use a Hummer to push a Prius you would do it going up the side of the canyon UNTIL you got to the lip, not after that point.
 

It's a flat plateau after you reach C3=0? Um, no. Your Grand Canyon metaphor is way off base. Once you reach reach the edge of earth's Hill Sphere you still need another 3 km/s to raise your aphelion to 1.52 A.U.

(http://clowder.net/hop/TMI/ImpalerPlateau.jpg)

Your correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth.  And the DeltaV is VIRTUALLY THE SAME.  The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect.


Wrong.

Falling from a high apogee you'd be moving 10.8 km/s at perigee.

At that speed, a .5 km/s burn will give you 3 km/s Vinfinity.

 (http://clowder.net/hop/TMI/HummerPrius.jpg)

.4 km/s to drop from EML2 and a .5 km/s perigee burn for TMI. The delta V from EML2 to TMI is only .9 km/s. So the booster stage can be a lot smaller than the MTV. Accordingly I ditched your Hummer for the more appropriate Moped.

After separation it will take the Moped another .9 km/s to get back to EML2 but this will take a lot less propellent since the Moped has much less dry mass. With an .18 km/s delta V budget and no need to endure an 8 km/s atmospheric re-entry, the Moped's reuse becomes a little more plausible.

In the mean time the MTV is on its way to mars without the mass of the moped.

If a one km/s acceleration takes 11 days, that LITTLE boost saves 33 days.

Of course mining and infrastructure capable of making hydrogen/oxygen bipropellent would also be able to make water that can be used for drinking, sanitation and radiation shielding. Also oxygen to breathe. If half of the MTV's mass is loaded at EML2, that halves the GLOW from earth's surface.
Title: Re: VASIMR Engine
Post by: Hop_David on 05/08/2015 02:59 AM
OTOH, I believe your 0.7 km/s from EML through TMI is low - you'll use about half that just leaving EML (the perigee lowering burn as you pass the Moon), so you can do an Oberth burn at earth. But the Oberth burn itself can be around 1 km/s (or some of the numbers appropriate for cargo mission do seem to be lower, as per your estimate).

.15 km/s suffices to drop from EML2 to a 111 km altitude perilune. At perilune it's traveling near lunar escape and so enjoys an Oberth benefit. A .18 km/s perilune burn will drop the ship to a deep perigee.

At perigee the ship is traveling 10.8 km/s. Hyperbolic velocity for Trans Mars Insertion is 11.3 km/s. So a .5 km/s perigee burn sends the ship on its way to Mars.

.15 + .18 + .5 = .83. From EML2 to TMI is about .8 km/s.
Title: Re: VASIMR Engine
Post by: Impaler on 05/09/2015 05:34 AM

You're easily amused.

Yes, I don't need to go through the trouble of resurrecting some point from months ago for my kicks.

It's a flat plateau after you reach C3=0? Um, no. Your Grand Canyon metaphor is way off base. Once you reach reach the edge of earth's Hill Sphere you still need another 3 km/s to raise your aphelion to 1.52 A.U.

It should have been obvious that slope in the canyon analogy referred to the gravity well of Earth and the need for high thrust to make use of the Oberth effect inside that well, not the DeltaV which was expressed as actual accelerating the car.  I made it quite clear that their was more acceleration to be done beyond C3=0, what's off base is your mangling of the analogy.

Your correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth.  And the DeltaV is VIRTUALLY THE SAME.  The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect.

Wrong.

Falling from a high apogee you'd be moving 10.8 km/s at perigee.

At that speed, a .5 km/s burn will give you 3 km/s Vinfinity.



You've simply repeated your figures from several months prior, I didn't directly reply because the discussion rapidly moved into your challenge of how a SEP vehicle could be powered, which I answered forthwith.  While I did badly underestimate the Oberth effect the overall mission architecture of kick-stages for SEP vehicles is still not compelling.

The ratio of burn to Vinfinity is 6 and assuming best case Hydrolox ISP of 450 we could replace all the propellent expended in the .5 km/s burn (or any amount burned at perigee) 1:1 with SEP propellents operating at 2700s ISP.  All the mass of that kick stages engine, along wither all the propellent retained for the kick stage reuse is just a dead-weight loss.  And 3000s is really the low end of what any likely SEP vehicle is going to do, 5000s is more likely to what your competing with.

.4 km/s to drop from EML2 and a .5 km/s perigee burn for TMI. The delta V from EML2 to TMI is only .9 km/s. So the booster stage can be a lot smaller than the MTV. Accordingly I ditched your Hummer for the more appropriate Moped.

After separation it will take the Moped another .9 km/s to get back to EML2 but this will take a lot less propellent since the Moped has much less dry mass. With an .18 km/s delta V budget and no need to endure an 8 km/s atmospheric re-entry, the Moped's reuse becomes a little more plausible.

In the mean time the MTV is on its way to mars without the mass of the moped.

If a one km/s acceleration takes 11 days, that LITTLE boost saves 33 days.

First off you yourself said the drop from EML2 to Earth perigee took 9 days so the saving would be 21 days not 33.  Our trip to Mars using SEP is months (cause fast trips are wasteful even if we had amazing alpha) so were hardly changing the length of the journey, in fact many low thrust Mars transfers cut the engine off during the middle phase of the journey so we may end up with no savings at all.

Kick stages for SEP are like very large carrier aircraft for launch vehicles.  Technically they squeeze a bit of performance out of the thing they are assisting, but it's not remotely worth the cost and complexity.  Like the old Elon quote "just make the rocket 10% bigger" and you have completely replaced the whole system of multiple vehicles, multiple propellents, multiple docking and in-situ propellents collected at tremendous cost.  I know your 'gung-ho' for lunar/asteroid derived propellents but your proposal is just trying to shoe-horn them into places they aren't useful.  If your not showing clear order-of-magnitude reduction in launch masses then forget about in-situ propellents, the production costs and infrastructure will eat up anything less then that.

Once Electric propulsion came on the scene it basically made chemical engines for in-space use obsolete and all the H2O molecules in asteroids and comets got rendered obsolete at the same time.  We can do so much better with the heavy noble gasses as propellents that we would only be interested in standard fuel/oxidizer bi-propellents when we are on a planetary surface such as the classic hydrocarbon production on Mars concept (which DOSE show a clear order of magnitude reduction in launch mass).

The only way things like water are going to be good in-space propellents again is if we get Electric thrusters that can utilize them.  This is a definite possibility, HALL thrusters can operate on a mixture of light elements so long as they have some heavy noble gasses to catalyze the ionization process, but they take an efficiency hit from higher ionization energy needs.  The most promising concept is the Electrode-less Lorentz Force thruster (ELF) which might be able to inject un-ionized gas into it's exhaust and hugely reduce the parasitic loss of ionization which would make the light elements far more attractive.  If such things can be developed then comet and asteroid 'bag and bake' methodologies may prove viable.
Title: Re: VASIMR Engine
Post by: dkovacic on 05/28/2015 11:57 AM
Very interesting progress update on ISDC 2015, presented by Dr. Franklin Chang Diaz

https://www.youtube.com/watch?v=5Aoa0waHiHk (https://www.youtube.com/watch?v=5Aoa0waHiHk)

Highlights:
1. Ions and electrons in the same plume, no neutralization needed
2. Primarily using argon, 6N thrust level achieved (estimated isp 3000s)
3. More than 10000 firings of VX-200
4. 70% efficiency with argon and ISP of 5000s.
5. With krypton, they could reach 75% efficiency.
6. CDR milestone beginning 2016.
7. ISS flight milestone beginning of 2018.
8. ISS reboost currently requires 7t of fuel and 210 million USD per year
9. Smaller 80kW unit would require 1/10 of this cost
10. various application specific animations shown
Title: Re: VASIMR Engine
Post by: Raj2014 on 05/28/2015 12:51 PM
Very interesting progress update on ISDC 2015, presented by Dr. Franklin Chang Diaz

https://www.youtube.com/watch?v=5Aoa0waHiHk (https://www.youtube.com/watch?v=5Aoa0waHiHk)

Highlights:
1. Ions and electrons in the same plume, no neutralization needed
2. Primarily using argon, 6N thrust level achieved (estimated isp 3000s)
3. More than 10000 firings of VX-200
4. 70% efficiency with argon and ISP of 5000s.
5. With krypton, they could reach 75% efficiency.
6. CDR milestone beginning 2016.
7. ISS flight milestone beginning of 2018.
8. ISS reboost currently requires 7t of fuel and 210 million USD per year
9. Smaller 80kW unit would require 1/10 of this cost
10. various application specific animations shown

I was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission.  VASIMR will be also a good choice to use.
Title: Re: VASIMR Engine
Post by: dkovacic on 05/29/2015 09:33 AM

I was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission.  VASIMR will be also a good choice to use.

VASIMR is still TRL6, and it will not be TRL9 until 2018, so that is a probable reason why it is not considered. Besides, Hall thrusters have much more actual flight heritage. But the main reason is that for ARM you don't really need variable ISP so much.

In my opinion, 70% efficiency is the real breakthrough, because it simplifies cooling requirements. I would expect that most of the losses are dissipated as heat inside the engine which has to be removed somehow. As far as I know, VASIMR has the highest thrust among electric propulsion devices produced so far.
Title: Re: VASIMR Engine
Post by: Nilof on 05/29/2015 02:52 PM

I was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission.  VASIMR will be also a good choice to use.

VASIMR is still TRL6, and it will not be TRL9 until 2018, so that is a probable reason why it is not considered. Besides, Hall thrusters have much more actual flight heritage. But the main reason is that for ARM you don't really need variable ISP so much.

In my opinion, 70% efficiency is the real breakthrough, because it simplifies cooling requirements. I would expect that most of the losses are dissipated as heat inside the engine which has to be removed somehow. As far as I know, VASIMR has the highest thrust among electric propulsion devices produced so far.

Well, OTOH the X-3 nested hall thruster was tested at about 2 N of thrust in 2013-2014, and was planning to double that "soon" roughly a year ago. I don't know about any SEP engine with a noticeably higher test stand thrust than the VX-200 though.

The possibility of using Krypton on Vasimr for better performance (and denser storage with a higher mass ratio) is also great news, and makes comparing different engines easier.
Title: Re: VASIMR Engine
Post by: Impaler on 05/29/2015 05:57 PM
VASIMR dose not compare favorably with the X3 HALL thruster, it has a much lower thrust:weight ratio
Title: Re: VASIMR Engine
Post by: Nilof on 05/29/2015 07:41 PM
Well, since the efficiency numbers have gone up, thrust per weight for a given Isp may have gone up as well. I'd be interested to see some updated numbers on VASIMR's thrust to weight ratio. In previous comparisons it was heavier than some other systems, but it certainly still has the performance needed to be used in something similar to the COMPASS spacecraft. Looking beyond mass, it is certainly bulkier than Halls though.

With that said, in the long run everything will eventually be obsolete. Ad astra currently has the advantage of having the largest single thruster that can fly within a short timeframe. With the latest numbers, it also seems to have a noticeably higher efficiency than Halls which is great in the current situation of power-limited spacecraft.

While it might not keep the advantages it has for long and should already be outmatched in T/W by other systems, it may be rather useful over the next decade, especially for unmanned missions going farther out than Mars.
Title: Re: VASIMR Engine
Post by: Raj2014 on 05/30/2015 10:56 PM
After the VX-200 SS, in the power point is it showing in the video a diagram, will Ad Astra make the VF-200 1 still for the ISS at a later date?
Title: Re: VASIMR Engine
Post by: Raj2014 on 07/18/2015 10:35 PM

I was just now going to post the link to that video. Comparing VX-200 to other electric propulsions for example hall effect thruster, VASIMR is looking good. I read that NASA is going to use hall effect thrusters for the ARM mission.  VASIMR will be also a good choice to use.

VASIMR is still TRL6, and it will not be TRL9 until 2018, so that is a probable reason why it is not considered. Besides, Hall thrusters have much more actual flight heritage. But the main reason is that for ARM you don't really need variable ISP so much.

In my opinion, 70% efficiency is the real breakthrough, because it simplifies cooling requirements. I would expect that most of the losses are dissipated as heat inside the engine which has to be removed somehow. As far as I know, VASIMR has the highest thrust among electric propulsion devices produced so far.

Here is an update on VASIMR (http://www.nacion.com/vivir/ciencia/Franklin-Motor-avanza-prueba-Tierra_0_1498250167.html). You will need to translate it if you can not read Spanish.
Title: Re: VASIMR Engine
Post by: MP99 on 07/20/2015 06:53 AM


OTOH, I believe your 0.7 km/s from EML through TMI is low - you'll use about half that just leaving EML (the perigee lowering burn as you pass the Moon), so you can do an Oberth burn at earth. But the Oberth burn itself can be around 1 km/s (or some of the numbers appropriate for cargo mission do seem to be lower, as per your estimate).

.15 km/s suffices to drop from EML2 to a 111 km altitude perilune. At perilune it's traveling near lunar escape and so enjoys an Oberth benefit. A .18 km/s perilune burn will drop the ship to a deep perigee.

At perigee the ship is traveling 10.8 km/s. Hyperbolic velocity for Trans Mars Insertion is 11.3 km/s. So a .5 km/s perigee burn sends the ship on its way to Mars.

.15 + .18 + .5 = .83. From EML2 to TMI is about .8 km/s.

I'm late to the party here, but thanks for the corrections. (Looks like I'd mis-remembered the ~1 km/s as the Earth perigee burn, instead of the total dV budget.)

Cheers, Martin
Title: Re: VASIMR Engine
Post by: manboy on 07/20/2015 07:32 AM
Here is an update on VASIMR (http://www.nacion.com/vivir/ciencia/Franklin-Motor-avanza-prueba-Tierra_0_1498250167.html). You will need to translate it if you can not read Spanish.
In March they got $10 mill from NASA. They plan to test the engine for a continuous 100 hours. May be ready to fly in late 2017. The International Space Station is mentioned by I'm unsure if VASIMR is still planned to be tested there.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 07/20/2015 01:39 PM
Is there an existing bus and guidance system that the VASIMR can use as a payload?

Solar panels will also be needed. 200 kW for a continuous burn or by trickle charging the battery pack in 15 minute bursts.
Title: Re: VASIMR Engine
Post by: Raj2014 on 07/20/2015 04:09 PM
Here is an update on VASIMR (http://www.nacion.com/vivir/ciencia/Franklin-Motor-avanza-prueba-Tierra_0_1498250167.html). You will need to translate it if you can not read Spanish.
In March they got $10 mill from NASA. They plan to test the engine for a continuous 100 hours. May be ready to fly in late 2017. The International Space Station is mentioned by I'm unsure if VASIMR is still planned to be tested there.

Yes I know. Thank you for telling me the information I already know. The link I posted was written on the 7th July and the test started on the 1st July. As for the ISS VASIMR, apparently it has been cancelled. 
Title: Re: VASIMR Engine
Post by: docmordrid on 08/12/2015 09:42 AM
Quote
Ad Astra Rocket Company and NASA move to execution phase of NextSTEP VASIMR partnership

Press Release From: Ad Astra Rocket Company

Posted: Monday, August 10, 2015

Ad Astra Rocket Company and NASA have successfully completed contract negotiations on the company's Next Space Technology Exploration Partnerships (NextSTEP) award, announced on March 31, 2015, and now enter the execution phase of the project.

The parties executed the contract, a three-year, fixed price agreement, on August 7, 2015 for a total value of just over $9 million. The agreement is structured as a one-year contract with two additional one-year extensions based on the accomplishment of mutually agreed upon progress milestones.

NASA's Advanced Exploration Systems Program sponsors NextSTEP awards in a 50/50 cost partnership with industry. Under this award, Ad Astra will conduct a long duration, high power test of an upgraded version of the VX-200TM VASIMR prototype, the VX-200SSTM (for steady state), for a minimum of 100 hours continuously at a power level of 100 kW. These experiments aim to demonstrate the engine's new proprietary core design and thermal control subsystem and to better estimate component lifetime. The tests will be conducted in Ad Astra's large, state-of-the-art vacuum chamber in the company's Texas facility.

Since its inception in 2005, Ad Astra has continued to advance the technology readiness level (TRL) of the VASIMR engine almost exclusively with private funding. This funding enabled the company to complete more than 10,000 successful high power firings, demonstrating the engine's excellent reliability and performance (6 N thrust, 5000 sec Isp at greater than 70% efficiency) with no measurable signs of engine wear.
To optimize company resources, these tests were of short duration (less than 1 minute), but sufficiently long to reliably establish the rocket's performance and measure thermal loads. Now, a longer duration test is needed to validate the new rocket core design for extended operation in space. Going forward in partnership with NASA under the NextSTEP award, Ad Astra continues the technology maturation of the VASIMR to a TRL level greater than 5, a step closer to flight.

"We are proud of our accomplishments and thrilled by this announcement, which gives us a big boost toward space," said Dr. Mark D. Carter, Ad Astra's Sr. VP, Technology Development. "I am proud to be a be part of this project, an example of a progressive commercial-NASA partnership, seeking to advance the United States' electric propulsion capability for the future of spaceflight," said Dr. Jared P. Squire, Ad Astra's Sr. VP, Research. Drs. Carter and Squire are leading the project at Ad Astra as Principal and Co-Principal Investigators respectively.

ABOUT THE TECHNOLOGY

Short for Variable Specific Impulse Magnetoplasma Rocket, VASIMR works with plasma, an electrically charged gas that can be heated to extreme temperatures by radio waves and controlled and guided by strong magnetic fields. The magnetic field also insulates nearby structures so exhaust temperatures well beyond the melting point of materials can be achieved. In rocket propulsion, the higher the temperature of the exhaust gases, the higher their velocity and the higher the fuel efficiency. Plasma rockets feature exhaust velocities far above those achievable by their chemical cousins, so their fuel consumption is extremely low.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 08/12/2015 01:48 PM
Does NASA have a use for the VASIMR in mind?
Or is this a general research project?
Title: Re: VASIMR Engine
Post by: Raj2014 on 08/12/2015 03:32 PM
Does NASA have a use for the VASIMR in mind?
Or is this a general research project?

Either way it is good news for VASIMR. I hope they do have a use for VASIMR if not I am sure many people could find uses for it. I can think of some right now.
Title: Re: VASIMR Engine
Post by: kdhilliard on 08/14/2015 10:30 PM
It's no secret that Robert Zubrin has a beef with Chang Díaz and VASIMR, but I was amused that he would take the opportunity to get another jab in while introducing the MIT students vs. Mars One debate last night at the Mars Society Convention.

Quote from: Robert Zubrin
This is a very controversial proposition and we're going to debate it.  And, I must say, that both sides here are to be congratulated for having the integrity and courage to come out and defend their point of view in clear and open debate face to face.  [Applause]  Because we've had too much in the space business of people going around saying stuff behind other people's back and not coming out in the open to say it openly and confront it.  Or other people saying things openly to the press but not being willing to come and defend their point of view.  We of course had the incident of Franklin Chang Díaz saying very detrimental things, that radiation is a show stopper on the way to Mars so we must go to Mars much quicker than is currently possible and only the VASIMR drive can enable this and thus you can't go to Mars until the Warp VASIMR is developed and you can't do your program until we do his program.  And he's been challenged to come and defend these statements repeatedly and not done it, which should tell you something that not only are his statements not defensible, but he doesn't consider them defensible.

In this case one of these two parties are wrong.  [Laughter]  But they're honest and they're willing to come out and say it.

~Kirk

Edit: Here is a link to the YouTube video (https://www.youtube.com/watch?v=O0BBdhbvBkg) of the debate.  The quoted remarks above start at 2:00.
Title: Re: VASIMR Engine
Post by: Stormbringer on 08/25/2015 01:16 PM
an article reiterating docmordrid's post's information:

http://www.space.com/30221-plasma-rocket-technology-nasa-funding.html
Title: Re: VASIMR Engine
Post by: sketchflygirl on 12/03/2015 03:04 AM
So, I am a comic book artist working on a science fiction comic book and I need help. I want to kind of base my space ships design on the VASIMR system but need help in understand how it actually works. I am a physicist and studying engineering so I have kind of an idea. But what I really want to know if the VASIMR propulsion system design can be changed for different space craft designing or if the system has to be built the way it is designed for it to actually work.

L. Monroy
MonroyART
monroyart.net
Title: Re: VASIMR Engine
Post by: TakeOff on 12/03/2015 07:50 AM
In case you've missed it, this presentation might give you clues and lead ons:
http://spirit.as.utexas.edu/~fiso/telecon/Carter_10-29-14/

(And I'm pretending to talk to guys' on my own level of ignorance. I'm not the educator in this game.)
Title: Re: VASIMR Engine
Post by: Cinder on 12/03/2015 08:03 PM
http://www.projectrho.com/public_html/rocket/  !  Dive in, it's worth it.
Its VASIMR section is here:
http://www.projectrho.com/public_html/rocket/enginelist.php#vasimr
Title: Re: VASIMR Engine
Post by: AegeanBlue on 03/07/2016 02:27 AM
I missed it originally but Planetary Radio visited Ad Astra Rocket Company and had a report:

http://www.planetary.org/multimedia/planetary-radio/show/2016/0104-2016_review.html
Title: Re: VASIMR Engine
Post by: qraal on 03/22/2016 09:10 AM
What do you want to change, and I can tell you if it's possible.

Adam

So, I am a comic book artist working on a science fiction comic book and I need help. I want to kind of base my space ships design on the VASIMR system but need help in understand how it actually works. I am a physicist and studying engineering so I have kind of an idea. But what I really want to know if the VASIMR propulsion system design can be changed for different space craft designing or if the system has to be built the way it is designed for it to actually work.

L. Monroy
MonroyART
monroyart.net
Title: Re: VASIMR Engine
Post by: Nilof on 03/22/2016 09:46 AM
So, I am a comic book artist working on a science fiction comic book and I need help. I want to kind of base my space ships design on the VASIMR system but need help in understand how it actually works. I am a physicist and studying engineering so I have kind of an idea. But what I really want to know if the VASIMR propulsion system design can be changed for different space craft designing or if the system has to be built the way it is designed for it to actually work.

L. Monroy
MonroyART
monroyart.net

You might also be interested in these two threads from a year ago on solar electric propulsion.

http://forum.nasaspaceflight.com/index.php?topic=36787
http://forum.nasaspaceflight.com/index.php?topic=36789.0

I believe some people were posting artwork there too and asking the community about technical details.

VASIMR is only one of many concepts, it just happens to have gotten a lot of press and currently the VX-200 is the biggest electric thruster available. This may change in the near future since Hall effect thrusters have become a lot better, and new options such as electrodeless lorentz force thrusters could eventually become better than VASIMR in every way.
Title: Re: VASIMR Engine
Post by: leovinus on 02/24/2017 04:12 AM
Hadn't heard from VASIMR for a while and came across this. Nice overview and description of 100kw/100hour test to come up. https://arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off/ (https://arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off/)
Title: Re: VASIMR Engine
Post by: Archibald on 02/24/2017 05:53 AM
Even Andy Weir succumbed to the 2012 VASIMR-hype. The ship in the Martin is VASIMR-powered :p
Title: Re: VASIMR Engine
Post by: tea monster on 02/24/2017 10:48 AM
Hadn't heard from VASIMR for a while and came across this. Nice overview and description of 100kw/100hour test to come up. https://arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off/ (https://arstechnica.com/science/2017/02/nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off/)

I was the guy asking about technical details for artwork. Here is the ship I came up with: https://www.turbosquid.com/3d-models/maya-manned-mars-ion-drive/944674

Although some of the newer SEP systems can be technically superior, AdAstra are the only people currently working on producing a space-worthy high-power thruster.

Ironically, the Asteroid Redirect mission looks like it is going to be cancelled, largely due to having 'not enough to do with going to Mars'. This is a big shame as it would have given us a space-worthy high power SEP system, which is widely regarded as a vital puzzle piece for manned travel around the solar system. Because they want to concentrate on 'Going straight to Mars' (which at this point has no mission planned or direct funding) we are now back to looking at power point presentations and research papers rather than building flight hardware. Sigh.
Title: Re: VASIMR Engine
Post by: savuporo on 05/28/2017 01:39 AM
Two relevant materials for the ongoing test campaign

http://adastrarocket.com/technical-articles/JPC%20AIAA-2016-4950.pdf
https://www.slideshare.net/ChrisHays4/final-technical-report-70423826

Title: Re: VASIMR Engine
Post by: Raj2014 on 05/28/2017 07:57 PM
Two relevant materials for the ongoing test campaign

http://adastrarocket.com/technical-articles/JPC%20AIAA-2016-4950.pdf
https://www.slideshare.net/ChrisHays4/final-technical-report-70423826

Fascinating to see but why is progress on V.A.S.I.M.R slow? 
Title: Re: VASIMR Engine
Post by: savuporo on 05/28/2017 08:03 PM
Fascinating to see but why is progress on V.A.S.I.M.R slow? 

speed = F(money)

Title: Re: VASIMR Engine
Post by: Robotbeat on 05/28/2017 08:17 PM
And because VASIMR is an overly complicated way of doing electric propulsion (needs superconducting magnetic coils, which are expensive to keep cool) and really isn't viable at commercial commsat scale.
Title: Re: VASIMR Engine
Post by: Raj2014 on 05/28/2017 10:56 PM
But did Ad Astra get more funding from N.A.S.A for V.A.S.I.M.R? I read many articles saying that Ad Astra got more funding to go towards V.A.S.I.M.R or was that not enough or are the articles false? I also do know that Ad Astra has other projects they are working on.     
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 06/03/2017 10:41 PM
But did Ad Astra get more funding from N.A.S.A for V.A.S.I.M.R? I read many articles saying that Ad Astra got more funding to go towards V.A.S.I.M.R or was that not enough or are the articles false? I also do know that Ad Astra has other projects they are working on.     

In 2015 NASA gave Ad Astra more money to develop a 100kW VASIMR under the NextSTEP program.
https://www.nasa.gov/sites/default/files/atoms/files/moore_aes_tagged.pdf (https://www.nasa.gov/sites/default/files/atoms/files/moore_aes_tagged.pdf)
Title: Re: VASIMR Engine
Post by: Asteroza on 06/05/2017 12:07 AM
And because VASIMR is an overly complicated way of doing electric propulsion (needs superconducting magnetic coils, which are expensive to keep cool) and really isn't viable at commercial commsat scale.

Which is why the CAT thruster that will be flying on a cubesat demo is interesting, since it is principally the same, just using a comparatively large permanent magnet (which is feasible at this scale, but probably unattractive at larger scales, hence VASIMR's superconducting magnets).

http://www.phasefour.io/ (http://www.phasefour.io/)

These guys also did a kickstarter to fund early work as well.

https://www.kickstarter.com/projects/longmier/cat-launch-a-water-propelled-satellite-into-deep-s (https://www.kickstarter.com/projects/longmier/cat-launch-a-water-propelled-satellite-into-deep-s)

http://pepl.engin.umich.edu/thrusters/CAT.html (http://pepl.engin.umich.edu/thrusters/CAT.html)

Though CAT has a fixed magnetic configuration, so it can't shift between high thrust and high efficiency modes like VASIMR can?
Title: Re: VASIMR Engine
Post by: spacenut on 06/05/2017 06:46 PM
Why not cluster a lot of smaller cheaper VASIMR engines for a larger vehicle?  Kind of like a Falcon 9 vs a Zenith.  Both about the same thrust but Falcon 9 cheaper or still in operation. 
Title: Re: VASIMR Engine
Post by: Raj2014 on 06/06/2017 11:20 PM
But did Ad Astra get more funding from N.A.S.A for V.A.S.I.M.R? I read many articles saying that Ad Astra got more funding to go towards V.A.S.I.M.R or was that not enough or are the articles false? I also do know that Ad Astra has other projects they are working on.     

In 2015 NASA gave Ad Astra more money to develop a 100kW VASIMR under the NextSTEP program.
https://www.nasa.gov/sites/default/files/atoms/files/moore_aes_tagged.pdf (https://www.nasa.gov/sites/default/files/atoms/files/moore_aes_tagged.pdf)

Yes, I have seen this before. Was the funding Ad Astra received not enough? After they have finished working on VASIMR for 100 hours what is the next step?     
Title: VASIMR Engine
Post by: Star One on 08/10/2017 07:49 PM
NASA’s plasma rocket making progress toward a 100-hour firing

Now, the company is firing VASIMR for about five minutes at a time.

Quote
This week, Ad Astra reported that it remains on target toward that goal. The company completed a successful performance review with NASA after its second year of the contract, and it has now fired the engine for a total of 10 hours while making significant modifications to its large vacuum chamber to handle the thermal load produced by the rocket engine.

Quote
When Ars visited the company early in 2017, the company was pulsing its rocket for about 30 seconds at a time. Now, the company is firing VASIMR for about five minutes at a time, founder Franklin Chang-Diaz told Ars. "The limitation right now is moisture outgassing from all the new hardware in both the rocket and the vacuum chamber," he said. "This overwhelms the pumps, so there is a lot of conditioning that has to be done little by little."

https://arstechnica.com/science/2017/08/nasas-plasma-rocket-making-progress-toward-a-100-hour-firing/
Title: Re: VASIMR Engine
Post by: Katana on 08/11/2017 04:44 AM
Why not cluster a lot of smaller cheaper VASIMR engines for a larger vehicle?  Kind of like a Falcon 9 vs a Zenith.  Both about the same thrust but Falcon 9 cheaper or still in operation.
Clustering even more hall thrusters could reach similiar performance easier.

This is one downside of VASMIR.
Title: Re: VASIMR Engine
Post by: Stormbringer on 08/16/2017 11:34 AM
^ on that note...

https://phys.org/news/2017-08-thruster-efficiency-future-spaceflight.html

1.  Will this mean HETs will be able to produce velocities of over 100,000 miles per hour soon? (assuming the high end of the efficiency increase of this new design plus the articles assertion that current hall effect thrusters can produce velocities of about 70K miles per hour.)

Quote
Plasma ejected from the exhaust end of the thruster can deliver great speeds, typically around 70,000 mph.


and

Quote
In particular, the specific impulse of the thruster increased by 1.1 to 53.5 percent when the discharge voltage was in the range of 100 to 200 Volts.


53.5 X 70,000=37450

37,450+70,000=107,450

2.  probably, -similar refinements in VASIMR design could probably increase it's efficiency too. after all refinement of modeling of magnetic nozzles resulted in an more than doubling of the max theoretical velocity of Antimatter engines and this translated into advancements of other propulsion sustems that used magnetic nozzles.
Title: Re: VASIMR Engine
Post by: corneliussulla on 08/25/2017 10:48 AM
Anew book out written by Erik seedhouse and franklin chang Diaz. It has the upto date story on Vasimr and the upcoming 100 hr test which should lead to test in space by 2020.   https://www.amazon.co.uk/Mars-Beyond-Fast-Revolutionize-Exploration/dp/3319229176
Title: Re: VASIMR Engine
Post by: Kryten on 10/25/2017 03:17 PM
http://akaerospace.com/news/commercial-rocket-launches-coming-kodiak-island
Quote
Ad Astra, a Texas-based aerospace company specializing in advanced plasma rocket propulsion technology, is contracted to launch from PSCA in late January or early February, he said. He said Kodiak may see “robust activity” from the company moving forward.
Title: Re: VASIMR Engine
Post by: A_M_Swallow on 10/25/2017 07:53 PM
http://akaerospace.com/news/commercial-rocket-launches-coming-kodiak-island
Quote
Ad Astra, a Texas-based aerospace company specializing in advanced plasma rocket propulsion technology, is contracted to launch from PSCA in late January or early February, he said. He said Kodiak may see “robust activity” from the company moving forward.

Have they got the right year on this launch?
The VASIMR 100 hour ground test is due in February 2018. The money for launch has to be acquired and construction of the propulsion module needs to occur.
Title: Re: VASIMR Engine
Post by: john smith 19 on 11/05/2017 09:39 AM
http://akaerospace.com/news/commercial-rocket-launches-coming-kodiak-island
Quote
Ad Astra, a Texas-based aerospace company specializing in advanced plasma rocket propulsion technology, is contracted to launch from PSCA in late January or early February, he said. He said Kodiak may see “robust activity” from the company moving forward.

Have they got the right year on this launch?
The VASIMR 100 hour ground test is due in February 2018. The money for launch has to be acquired and construction of the propulsion module needs to occur.
Indeed.

That timeline for 2018 only works out if the results have been very consistent and an investor group is happy to go ahead without it running to completion.

Which is a good investor to have, if you can find such people. They tend to be quite rare.
Title: Re: VASIMR Engine
Post by: Raj2014 on 11/05/2017 05:01 PM
http://akaerospace.com/news/commercial-rocket-launches-coming-kodiak-island
Quote
Ad Astra, a Texas-based aerospace company specializing in advanced plasma rocket propulsion technology, is contracted to launch from PSCA in late January or early February, he said. He said Kodiak may see “robust activity” from the company moving forward.

Have they got the right year on this launch?
The VASIMR 100 hour ground test is due in February 2018. The money for launch has to be acquired and construction of the propulsion module needs to occur.
Indeed.

That timeline for 2018 only works out if the results have been very consistent and an investor group is happy to go ahead without it running to completion.

Which is a good investor to have, if you can find such people. They tend to be quite rare.

So does they mean, Ad Astra will (finally) have V.A.S.I.M.R launched into space? I hope this is true.
Title: Re: VASIMR Engine
Post by: john smith 19 on 11/05/2017 06:25 PM

So does they mean, Ad Astra will (finally) have V.A.S.I.M.R launched into space? I hope this is true.
The implication is that yes they will launch something next year. Beyond that, who knows?