There are a number of entries on the HB for various spaceships powered by a daisy chain of explosions - usually nuclear but, sadly, no underwater craft. Therefore, I am putting forward a suggestion of building a torpedo shape craft with a rocket nozzle or combustion chamber at the rear into which small pellets of sodium are injected.

Sodium, which reacts very enthusiastically with water, is not a pollutant once it is mixed back with seawater so would there would be no hydrocarbon byproducts or leakage. I'm not sure of the energy density of Na compared to petroleum products or batteries but suspect it would be good enough. This device would be noisy, inefficient and quite dangerous but could be marginally viable which has always been good enough for me. I find that low standards make life easier anyway.

"Create sodium pellets and pour water over them."
-- AusCan531, May 10 2012

Kursk submarine explosion http://en.wikipedia...ine_Kursk_explosion
Not good [8th of 7, May 10 2012]

VA-111 Shkval http://en.wikipedia.../wiki/VA-111_Shkval
interesting ... [8th of 7, May 10 2012]

Supercavitation http://en.wikipedia...iki/Supercavitating
Also interesting. [8th of 7, May 10 2012]

Reactions of sodium and Potassium with Water http://www.youtube....watch?v=l9z5-mJ8NZk
Maxwell Buchanan is correct of course about K being more reactive the Na [AusCan531, May 11 2012]

Verrry interesting report on dropping alkali metals into water http://www.theodore...aliBangs/index.html
(And the resultant bangs) [AusCan531, May 11 2012]

I think you will find that when sodium reacts with water, the main result is sodium hydroxide (lye). Yes, it dissolves in seawater nicely. But it likely still counts as a pollutant.
-- Vernon, May 10 2012


Is the reaction violent enough? I suppose it might be of the sodium were finely divided, but I'd recommend potassium instead.
-- MaxwellBuchanan, May 10 2012


Instead of pellets, the machine could extrude a solid rod of sodium from its rear end.
-- pocmloc, May 10 2012


has anyone ever attempted to superheat the water at the front of the submarine?
-- theircompetitor, May 10 2012


I recall a vogue for francium on the HB some years ago.
-- bungston, May 10 2012


// has anyone ever attempted to superheat the water at the front of the submarine? //

"Kursk" ...

<links>
-- 8th of 7, May 10 2012


Those links are indeed interesting [8th]. The claimed speeds for underwater objects are astonishing. P'raps I should amend my Sub-m-Orion design to be propelled by a combustion chamber at the rear, as initially postulated, but additionally have a small amount of the sodium (or potassium) extruded out the front to create the super cavitation effect.

I don't think it would exactly have a 'silent running' mode but it might go like the clappers.

In reply to [theircompetitor], most of the effort has heretofore been spent on trying to superheat the water in front of, and generally all around, the other guy's submarine.
-- AusCan531, May 10 2012


For which there are two approaches …

(a) Arrive so fast that your opponent has no time to react, deploy countermeasures, or take evasive action;

or,

(b) Arrive slowly, but so quietly and inconspicuously that your opponent has no time to react, deploy countermeasures, or take evasive action.

Choose either option (a) or option (b); they are, by and large, mutually exclusive.
-- 8th of 7, May 10 2012


Agreed. Although kinetic bombardment from orbit might qualify as something arriving quickly, quietly and inconspicuously.

One of my favourite sayings is that there is 'good', 'quick' and 'cheap' - you can pick any two. Especially when I am quoting on projects.
-- AusCan531, May 10 2012


The Kursk suffered a little problem with torpedo propellant cooking off in the forward torpedo compartment, didn't it? Peroxide and kerosene, or similar, went bang and cooked the front off the sub.

The remainder of the crew were trapped in an aft compartment and a CO2 scrubber set the atmosphere on fire when it came into contact with water in the compartment?

It's been a while since I read the story.
-- UnaBubba, May 11 2012


It might be a little difficult to convince the Navy that carrying a massive block of sodium metal around, underwater, is a good idea.
-- UnaBubba, May 11 2012


They do carry nuclear weapons and sundry combustibles underwater. And it wouldn't be a massive block of sodium anyway (just a massive bunch of little pellets of sodium).

To be fair, I did say in the post that it would noisy, inefficient and quite dangerous.
-- AusCan531, May 11 2012


Sodium hydroxide is indeed nasty, but it would be converted to harmless carbonate/bicarbonate over a few hours or so.

Look up liquid metal nuclear reactors for a precedent for carrying significant amounts of sodium metal around underwater.
-- spidermother, May 11 2012


<pedant>

Liquid-metal cooled nuclear reactors

</pedant>

And it's actually NaK, a eutectic Sodium- Potassium alloy.
-- 8th of 7, May 11 2012


//Sodium hydroxide is indeed nasty, but it would be converted to harmless carbonate/bicarbonate//

You lye! (Sorry, I was just being caustic)
-- AusCan531, May 11 2012


//And it's actually NaK, a eutectic Sodium- Potassium alloy//

...And I see that anything from 40-90% potassium is liquid at room temperature. Well then, isn't liquid NaK the perfect fuel for this project? If it's being used as a coolant in nuclear reactors, then all of the phase chemistry will be well worked out, compatibility with piping materials, welding, etc. It's allready been done.

Hypergolic (with seawater) Liquid fueled torpedo anyone?
-- Custardguts, May 21 2014


Thermite is the obvious choice here. Aluminum and rust are stable and safe for the sub and its sailors. Reaction is just fine in water environment.
-- bungston, May 21 2014



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