Author Topic: Nuclear Salt Water Propulsion  (Read 30224 times)

Offline SpaceGeek123

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Nuclear Salt Water Propulsion
« on: 02/07/2012 12:05 am »
Robert Zurin's  proposal for a Nuclear Salt water engine seems to solve this problem. The Transit time is quite fast (over 3.6% the speed of Light) and its relatively low tech (no Antimatter or Fusion).

So what's your view on the system.
Links:
http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket
http://www.npl.washington.edu/av/altvw56.html

PS:this is my first post on this forum

Offline QuantumG

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Re: Nuclear Salt Water Propulsion
« Reply #1 on: 02/07/2012 12:09 am »
Welcome to the forum!
Human spaceflight is basically just LARPing now.

Offline strangequark

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Re: Nuclear Salt Water Propulsion
« Reply #2 on: 02/07/2012 12:23 am »
Robert Zurin's  proposal for a Nuclear Salt water engine seems to solve this problem. The Transit time is quite fast (over 3.6% the speed of Light) and its relatively low tech (no Antimatter or Fusion).

So what's your view on the system.
Links:
http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket
http://www.npl.washington.edu/av/altvw56.html

PS:this is my first post on this forum

Creating a chamber/nozzle that will not melt (or even boil) is a huge, not to be underestimated challenge. It may seem low tech, but the devil-in-the-details problems are liable to make fusion easier.

Offline SpaceGeek123

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Re: Nuclear Salt Water Propulsion
« Reply #3 on: 02/07/2012 03:10 am »
Were talking about advanced version of Nuclear Thermal Rockets (NTR).
I'm not saying this is something congress could fund tomorrow. I'm saying its a promising technology thats been overlooked.

Fusion suffers many technological problems as well. First off there are currently no fusion reactors that have made more energy than they consume. Even if it does just obtaining any energy from fusion requires megawatt size laser and other complicated technology.

NSWP Is a doable project low cost program. ( more than the ISS, less than one year of us military spending)

Don't get me wrong I like fusion. Its probably the best way in the long run for manned interstellar travel. But its expensive, complecated and difficult. NSWP is cheap, simple and possible with near term (within 100 years) tech.

Offline Jim

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Re: Nuclear Salt Water Propulsion
« Reply #4 on: 02/07/2012 03:16 am »

 less than one year of us military spending)


Strawman.  Meaningless comparison.  Money is not available to NASA.  It has to come out of NASA current budget levels

Offline Jim

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Re: Nuclear Salt Water Propulsion
« Reply #5 on: 02/07/2012 03:17 am »

NSWP Is a doable project low cost program.

Doable is not a given and it is not low cost if it more than the ISS.

Offline SpaceGeek123

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Re: Nuclear Salt Water Propulsion
« Reply #6 on: 02/07/2012 03:23 am »
Like I said this isn't something the US congress will fund tomorrow. Its also not something NASA can do within there budget. I was comparing it to Fusion. Fusion power which would bankrupt the world economy. (the daedalus probe was estimated at $100 trillion)

Offline cuddihy

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Re: Nuclear Salt Water Propulsion
« Reply #7 on: 02/07/2012 04:35 am »
Salt water to nukes is like garlic to a vampire. You start a conversation with anyone who knows anything about nuke power you lose them at the words "salt water". It's not fair, but US nuclear folks are pretty much all Pressurized Water reactor types and you will never convince them that salt water should be anywhere near a primary or secondary coolant system.

Offline Andrew_W

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Re: Nuclear Salt Water Propulsion
« Reply #8 on: 02/07/2012 05:18 am »
The storage of the nuclear material as described by wiki seems to be a major problem, I wonder if the concept would work as an accelerator driven system.
« Last Edit: 02/07/2012 04:29 pm by Chris Bergin »
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Offline Andrew_W

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Re: Nuclear Salt Water Propulsion
« Reply #9 on: 02/07/2012 05:43 am »
Salt water to nukes is like garlic to a vampire. You start a conversation with anyone who knows anything about nuke power you lose them at the words "salt water". It's not fair, but US nuclear folks are pretty much all Pressurized Water reactor types and you will never convince them that salt water should be anywhere near a primary or secondary coolant system.

Keep in mind that we're not talking NaCl.
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline LegendCJS

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Re: Nuclear Salt Water Propulsion
« Reply #10 on: 02/07/2012 12:46 pm »
Salt water to nukes is like garlic to a vampire. You start a conversation with anyone who knows anything about nuke power you lose them at the words "salt water". It's not fair, but US nuclear folks are pretty much all Pressurized Water reactor types and you will never convince them that salt water should be anywhere near a primary or secondary coolant system.

(1) Three things: 

(2) What does fairness have to do with the US being pressurized Water reactor focused

(3) You didn't read the proposal very well if at all.
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline scienceguy

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Re: Nuclear Salt Water Propulsion
« Reply #11 on: 02/07/2012 03:29 pm »
I appreciate Jim's back-to-reality comments.
e^(pi*i) = -1

Offline Chris Bergin

Re: Nuclear Salt Water Propulsion
« Reply #12 on: 02/07/2012 04:38 pm »
Right, here's the deal people.

1) Welcome to the site's forum SG123.
2) Be very careful with the subject matter, as I was tempted to delete this thread based on the "less than one year of us military spending" (do not go there).
3) If this thread needs some reality, do it in a civil way or lose your posts - I don't care who you are.
4) Do not then turn this thread into a "let him talk about nonsense, don't be so nasty" - report to mod and we can deal with it.

Anyone breaching the above on this thread will get kicked off site on a timeout, yes, just like Nanny 911.

Carry on.
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Offline Lurker Steve

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Re: Nuclear Salt Water Propulsion
« Reply #13 on: 02/07/2012 05:19 pm »

 less than one year of us military spending)


Strawman.  Meaningless comparison.  Money is not available to NASA.  It has to come out of NASA current budget levels

Since when has anything compared to 1 year of defense spending qualified as low cost ?

Offline strangequark

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Re: Nuclear Salt Water Propulsion
« Reply #14 on: 02/07/2012 05:41 pm »
Were talking about advanced version of Nuclear Thermal Rockets (NTR).
I'm not saying this is something congress could fund tomorrow. I'm saying its a promising technology thats been overlooked.
It’s not just an advanced NTR. To get the Isps talked about, the temperature is somewhere in the 100,000s to 1,000,000s of degrees F. Current engines struggle at 7000 deg. There are no materials which will sustain that kind of temp. That means you have some kind of crazy cooling scheme, or magnetic confinement. Either one makes this a fairly daunting endeavor.

Quote
Fusion suffers many technological problems as well. First off there are currently no fusion reactors that have made more energy than they consume. Even if it does just obtaining any energy from fusion requires megawatt size laser and other complicated technology.
I was using fusion as an example of something else that is phenomenally hard, to explain just how difficult the NSWR really is. As for the rest, this is the wrong forum to give a PopSci description of fusion. Many of us are engineers, and there’s even a plasma physicist or two lurking. Your description reveals that you need to do some more homework before explaining fusion to other people.

Quote
NSWP Is a doable project low cost program. ( more than the ISS, less than one year of us military spending)
It may or may not be doable. The technology required is pretty hypothetical, even if it looks straightforward at the 30,000 ft level. You also don’t have any basis for that estimate, other than pulling it as a wild guess (Zubrin doesn’t either, if you’re quoting).

Quote
Don't get me wrong I like fusion. Its probably the best way in the long run for manned interstellar travel. But its expensive, complecated and difficult. NSWP is cheap, simple and possible with near term (within 100 years) tech.
Again, no basis for your comments that it is cheap, simple, and possible. Also, there are tons of fusion concepts out there, and you have no valid metric to compare these two concepts. There are too many unknowns.

It’s not that this is a bad idea, but it is pretty hypothetical, and it is very premature to be making any concrete absolute statements like you have. That will get you kicked in the tail faster than anything around here. Also, you need to accept criticism of the concept. There are some very sharp people on here, and the right response most of the time is to listen and learn, not to attack because the forum was not wowed by how the idea you posted will change everything.

Sorry for the harsh introduction to the forum, but a lot of newbies follow this unfortunate pattern:

Newbie: Check out this cool idea, it would revolutionize spaceflight!

Forum Vet: Not as easy as you think because of X, Y, and Z.

What Newbie Should Say: Hmm, tell me more about X. I didn't think about that.

What Newbie Does Say: Pfft, you must be wrong. This is revolutionary! All we need is unobtanium.

Forum Vet: ::Why do I post on Advanced Concepts?::

Newbie (optional): SpaceX is probably working on it. I bet Elon will announce it when he lands on Mars next year.

Offline Patchouli

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Re: Nuclear Salt Water Propulsion
« Reply #15 on: 02/07/2012 05:45 pm »
This is the type of stuff NASA should be funding vs SLS as it's out of the reach of most commercial entities but very high pay off.

Anyone with a few hundred million laying around can go build a capsule or chemical launch vehicle as the R&D for these is within reach,the red tape is not unnavigable and they have immediate commercial applications.

But the propulsion needed for serious deep space exploration can be very expensive, does not have clear commercial applications like a Falcon 9 rocket, and in the case of nuclear engines it's a red tape nightmare for anyone but government entities.
« Last Edit: 02/07/2012 05:51 pm by Patchouli »

Offline Sohl

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Re: Nuclear Salt Water Propulsion
« Reply #16 on: 02/07/2012 05:56 pm »
I like this NSWP idea a lot.  Talk about your "shockwave rider!"

Researching and attempting some early development of this concept is what I would really like to see NASA doing.  Testing this on the ground would be problematic, much moreso than NERVA.

Thumbnail development program:

1) Detailed study, with design and heavy numerical simulation of a "small" demo thruster (smallest feasible that would sustain criticality), assess risks and refine costs for later development program steps ... a few $million

2) Subsystem/materials demonstrators - build examples of needed subsystems and novel materials and test them with subcritial reactions, possibly underground, develop a detailed plan to scale-up the thruster to a full working version... tens of $millions  (MAKE SURE THE THERMAL ISSUES CAN BE HANDLED!)

3) MEO/GEO demonstration thruster firing - complete design and then build a minimally-practical demonstrator thruster that can be lofted to orbit on a conventional launch vehicle, test fire in a direction that the exaust won't likely impact Earth... a few hundred $million, with perhaps multiple demonstrators built and flown with increasing total impulse (thrust level and/or duration)

3) Deep space demonstration mission -  increase the robustness of the thruster for sustained deep space mission, perhaps also increase the spec. impulse performance and/or thrust to mass ratio, demonstrate on a worthwhile exploration mission (Uranas orbiter, Europa lander, ?) ... maybe half a $billion (not counting payload probe)

4) Man-rate the thruster and improve reliabilty and safety for human exploration missions (Mars, etc.) and launch a demonstrator from L2 ... a few $billion.

...
Longer term, FOCAL telescope to image a promising exoplanet system... manned mission to Mars... under-ice robot submarines to Europa, Encedalus, etc. etc.  :-)

By the time NASA spent $50 million, we might have a pretty good assessment if the idea will prove practical or not.

Offline rushdrums

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Re: Nuclear Salt Water Propulsion
« Reply #17 on: 02/07/2012 07:25 pm »
Not that I use Wiki as a reliable source, but this page does seem to authoritatively clarify all of the different Molten Salt and Salt Water reactor types:
http://en.wikipedia.org/wiki/Molten_salt_reactor

Could a MS reactor be made powerful enough for deep space use? Even if it is only powered up after it's launched by boring old chemical rockets?

MS reactor tech seems within our current technological grasp, but I'm not informed enough to know if it meets the power requirements that long distance HSF requires...

(okay. chemical rockets are not boring. they're awesome too   ;o) )

-Rush

Thoughts?

Offline blasphemer

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Re: Nuclear Salt Water Propulsion
« Reply #18 on: 02/07/2012 08:01 pm »
Nuclear salt-water rocket is really a very intriguing concept to me, one of a few semi-realistic proposals on how to achieve both high thrust and high specific impulse propulsion.

The other one is nuclear pulse propulsion (project Orion).

All the other advanced propulsion schemes I encountered on the internet are either low-thrust or require some great technological breakthrough (such as control of nuclear fusion, antimatter or warp drive).

Offline ArbitraryConstant

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Re: Nuclear Salt Water Propulsion
« Reply #19 on: 02/08/2012 11:57 am »
Could a MS reactor be made powerful enough for deep space use?
What advantages of this technology do you think carry over effectively to space?

It seems to me space reactors would be much better off using technology more similar to naval reactors. These mostly use HEU fuel. Space likely favors a different choice of coolant instead of water, probably molten metal or gas.

The advantages molten salt advocates (they are numerous and vocal) like to talk about aren't really relevant in space. For small, high performance reactors, HEU gets the advantages without the scaling and proliferation concerns of using HEU in civilian use.

Salt water to nukes is like garlic to a vampire. You start a conversation with anyone who knows anything about nuke power you lose them at the words "salt water". It's not fair, but US nuclear folks are pretty much all Pressurized Water reactor types and you will never convince them that salt water should be anywhere near a primary or secondary coolant system.
You should perhaps review the concept in a little more detail before dismissing it on this basis, I suspect you'll find better grounds to object.

The concept doesn't have what you would recognize as coolant loops, primary or otherwise.

The storage of the nuclear material as described by wiki seems to be a major problem, I wonder if the concept would work as an accelerator driven system.
I think that's sorta tangent to the problem, and I don't really think it's a major one.

For fission reactions, it's not just a critical mass you're worried about, but also a critical geometry. Imagine a long thin wire of Uranium. Now imagine a neutron being emitted in a random direction. Most paths leave the wire quickly, and very few neutrons will be emitted in a path that stays within the wire long enough to generate more neutrons. So this geometry is not critical even though there can be many critical masses. Now picture a sphere. Obviously, more paths stay inside the Uranium for longer. That's how you can get a critical geometry.

An accelerator does not avoid the need to have many critical masses of fuel on board, simply because the vehicle has to sustain the reaction for many seconds without using up all its fuel at once (it's not a bomb).

So it has to have many critical masses on board, without any critical geometries (except the one in the engine, and that needs to be possible to shut down). But the most efficient way to store a fluid is in a spherical or cylindrical tank. So that's your problem, that's also a geometry that can go critical. So that's where the neutron absorbing rods come in.

Now, additionally, the way accelerator driven reactors work is that they're very close to criticality. Imagine 1000 neutrons, then 999, then 998, etc. Only a very small number of neutrons have to be contributed, and the reactor is running at a steady state so exactly breaking even with a very small contribution from the accelerator is okay.

Now if you picture the fuel entering the reaction chamber of a NSWR, this is unacceptable. You want a huge neutron surplus to increase each generation rapidly and have it go from a cool liquid to plasma shooting out the engine in a tiny fraction of a second. No accelerator could possibly supply that kind of neutron input. You may want an external neutron source to make sure the reaction reliably starts where you want it to, but that's a separate problem, and still not that many neutrons. That can be an accelerator, but would more typically be an isotope with a high spontaneous neutron rate.

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