Author Topic: VASIMR Engine  (Read 155287 times)

Offline Elmar Moelzer

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Re: VASIMR Engine
« Reply #240 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.

Offline Star One

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Re: VASIMR Engine
« Reply #241 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?

Offline Nilof

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Re: VASIMR Engine
« Reply #242 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.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Robotbeat

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Re: VASIMR Engine
« Reply #243 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).
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Offline Robotbeat

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Re: VASIMR Engine
« Reply #244 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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline A_M_Swallow

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Re: VASIMR Engine
« Reply #245 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.

Offline Star One

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Re: VASIMR Engine
« Reply #246 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.
« Last Edit: 04/02/2015 06:41 AM by Star One »

Offline Raj2014

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Re: VASIMR Engine
« Reply #247 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.   

Offline Nilof

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Re: VASIMR Engine
« Reply #248 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.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline aceshigh

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Re: VASIMR Engine
« Reply #249 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, itīs not much different than other electric propulsion schemes.

Offline Asteroza

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Re: VASIMR Engine
« Reply #250 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.

Offline Impaler

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Re: VASIMR Engine
« Reply #251 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.
« Last Edit: 04/03/2015 06:06 AM by Impaler »

Offline spacenut

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Re: VASIMR Engine
« Reply #252 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? 

Online catdlr

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Re: VASIMR Engine
« Reply #253 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
Tony De La Rosa

Offline Star One

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Re: VASIMR Engine
« Reply #254 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?

Offline QuantumG

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Re: VASIMR Engine
« Reply #255 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.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline tchernik

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Re: VASIMR Engine
« Reply #256 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?

Offline Jimmy Murdok

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Re: VASIMR Engine
« Reply #257 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.

Offline QuantumG

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Re: VASIMR Engine
« Reply #258 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.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Star One

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Re: VASIMR Engine
« Reply #259 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.

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