Fun toy the Navy could add with a Polywell-equipped fleet

scareduck · Post by **scareduck** » Mon Jan 28, 2008 9:27 pm

The Navy just accepted delivery of a 32 MJ rail gun. Sounds cool and all, but they're not too helpful if you don't have a shipboard power source that can drive 3M amps. The Polywell could change that (usual caveats apply).

Roger · Post by **Roger** » Mon Jan 28, 2008 10:29 pm

(NJ CLass ?)Those big US battleships of WW2 were pushed sideways when they fired all of their guns at once......

Someday they will make a ground based rail gun, ground based, because its too big for a Naval ship. :/

Keegan · Post by **Keegan** » Mon Feb 11, 2008 8:00 am

This article makes me so angry...

At 32 megajoules, this new system appears to be the most powerful rail gun ever built,
and the Office of Naval Research is installing additional capacitors at the Dahlgren facility to support it.

Seriously how many millions of dollars do you think the ONR have spent developing this system over the years to get it where it is now ? Yet they completely snubbed the polywell, which is one of the few systems that could hope to power its bigger tactical successors, oh yeah and solve the worlds energy problems.

What for ? Now we can shoot dem trrists with hypervelocity slugs, ontop of our arsenal of SMART missiles and laser guided artillerily which are already proving less effective against the guerrilla based warfare seen in this century.

Congratulations, another fine use of tax payer's money.

scareduck · Post by **scareduck** » Mon Feb 11, 2008 4:12 pm

The ONR gave limited funding to the Polywell for politically sound reasons. Had they tried for substantially more money, the answer would have been "no" outright, because the Department of Energy would claim jurisdiction over any fusion programs. Once the tokamak guys got hold of it, it would have been dead after the publication of Rider's thesis in 1995.

JD · Post by JD » Mon Feb 11, 2008 8:36 pm

The various branches have mandates concerning the areas they can fiddle with. Normally this serves us very well and prevents a huge amount of repetitive and blatantly wasteful projects. As observed the Navy cannot be the main researcher in energy sources and could only support Bussard's project to any degree because of implications for naval uses. This is much like the Air Force when they delved into reactor research back in the 50's and 60's. Their justification was nuclear powered air transport (they actually produced something that could have worked by the way).

The EM gun systems are an example as well. They have prime justification, just as the Army does, for developing such weapons. The hard ceiling for practical tube artillery is around 6000 fps as I remember. Current tank main guns hit around 5200 fps firing a 10 lb sabot encased long rod penetrator at about 7.5 Mj's. That's taken years of refinement and there's not a lot of potential for noticeable increase. This is the justification for working on rail gun development where they're already achieving velocities of over 7k fps.

If the project succeeds and the Navy puts down money for a full scale demonstrator it will be attempting to produce something that could fit within a naval vessel. Even if it works, if it becomes apparent that it would be impossible to fit it within even a large ship the Navy will have to pass on the research to another agency. It's not their mandate to produce commercial power plants. Hopefully the project will have proven itself to a degree that even the Department of Energy couldn't bork it up.

MSimon · Post by **MSimon** » Mon Feb 11, 2008 9:35 pm

In the 50s the AEC and Naval Reactors were one.

His name was Rickover.

Keegan · Post by **Keegan** » Tue Feb 12, 2008 1:10 pm

^ Rickover. Respect.

Wikipedia wrote:
The imagination, drive, creativity and engineering expertise demonstrated by Rickover and his team during that time-frame resulted in a highly reliable nuclear reactor in a form-factor that would fit into a submarine hull with no more than a 28-foot beam. These were substantial technical achievements:

* In the early 1950s, a megawatt-scale nuclear reactor took up an area roughly the size of a city block.

* The prototype for the Nautilus propulsion plant was the world's first high-temperature nuclear reactor.

* The basic physics data needed for the reactor design were as yet unavailable.

* The reactor design methods had yet to be developed.

* There were no available engineering data on the performance of water-exposed metals that were simultaneously experiencing high temperatures, pressures and multi-spectral radiation levels.

* No nuclear power plant of any kind had ever been designed to produce steam.

* No steam propulsion plant had ever been designed for use in the widely varying sea temperatures and pressures experienced by the condenser during submarine operations.

* Components from difficult, exotic materials such as zirconium and hafnium would have to be extracted and manufactured with precision via techniques that were as yet unknown.

Hmmmm sound familiar.......?

scareduck · Post by **scareduck** » Tue Feb 12, 2008 5:41 pm

Keegan wrote:Hmmmm sound familiar.......?

Certainly. On the other hand, we still don't know if

Bussard was right on the scaling laws, and in particular if the loss mechanisms won't scale with the device.
whether ion thermalization and upscattering are indeed major loss mechanisms. Ditto for bremsstrahlung.
the core for a 1.5m radius machine be dense enough to get to Q=1.
a production machine can tolerate neutrons from a D-D reactor. (This is important if p-11B is infeasible.)

By comparison, the heating, cooling, and control mechanisms look like child's play.

MSimon · Post by **MSimon** » Tue Feb 12, 2008 7:26 pm

Bussard was right on the scaling laws, and in particular if the loss mechanisms won't scale with the device.

The power scaling laws are inherent in the physics and are uncontroversial. It is the losses where the differences of opinion come in.

* a production machine can tolerate neutrons from a D-D reactor. (This is important if p-11B is infeasible.)

It may be possible to get 6 months to a year of MgB11 superconductor operating time where natural Boron would get you a few hours.

I can even tell you how to shield the superconductors with B10, if you can tell me what to do with the heat generated by neutron absorption (2.8 MeV per thermal neutron).

BTW nice way to boost thermal output if you are going with a thermal plant. It adds 1/4 to 1/3 to the energy output.

By comparison, the heating, cooling, and control mechanisms look like child's play.

Except that there is nothing you can do if the physics doesn't work out.

If the physics says that you can theoretically have an economic machine the good interrelation of all those elements is the difference between profit and loss.

BTW heat transfer of 1 Mw per sq m is not child's play. Especially if you have to keep a volume 6" away at 20K. .3 Mw per sq m is considered "normal".

culthero · Post by **culthero** » Wed Jun 18, 2008 10:42 pm

BTW heat transfer of 1 Mw per sq m is not child's play. Especially if you have to keep a volume 6" away at 20K. .3 Mw per sq m is considered "normal".

How much water / coolant would be needed to rush through that square meter per second to transfer the heat?

MSimon · Post by **MSimon** » Wed Jun 18, 2008 10:55 pm

culthero wrote:BTW heat transfer of 1 Mw per sq m is not child's play. Especially if you have to keep a volume 6" away at 20K. .3 Mw per sq m is considered "normal".

How much water / coolant would be needed to rush through that square meter per second to transfer the heat?

100 to 200 gpm or about 400 to 800 l/min

Billy Catringer · Post by **Billy Catringer** » Tue Feb 03, 2009 8:36 pm

MSimon wrote:
culthero wrote:BTW heat transfer of 1 Mw per sq m is not child's play. Especially if you have to keep a volume 6" away at 20K. .3 Mw per sq m is considered "normal".

How much water / coolant would be needed to rush through that square meter per second to transfer the heat?
100 to 200 gpm or about 400 to 800 l/min

Why use demin water? There are a number non-conducting coolants, mineral oil and sulphur hexafluoride come to mind almost immediately, but even kerosene would likely be better than water. Would such coolants cause a problem with the particles in the machine?

MSimon · Post by **MSimon** » Tue Feb 03, 2009 9:48 pm

Billy Catringer wrote:
MSimon wrote:
culthero wrote:BTW heat transfer of 1 Mw per sq m is not child's play. Especially if you have to keep a volume 6" away at 20K. .3 Mw per sq m is considered "normal".

How much water / coolant would be needed to rush through that square meter per second to transfer the heat?
100 to 200 gpm or about 400 to 800 l/min

Why use demin water? There are a number non-conducting coolants, mineral oil and sulphur hexafluoride come to mind almost immediately, but even kerosene would likely be better than water. Would such coolants cause a problem with the particles in the machine?

Water is cheap. It is well understood. And it doesn't break down into sludge under neutron bombardment.

Billy Catringer · Post by **Billy Catringer** » Wed Feb 04, 2009 12:25 am

Fair enough! Just remember that you will have to change that water out regularly or run it through treatment every day or so. Demin water likes metals. It starts dissolving them fairly quickly.