Submarine Propulsion

taylaron

sounds like the movie "the abyss" by james cameron.
in this movie i think they use liquid oxygen or something along those lines to "breathe a liquid for insane depths."
but i was talking about mini remote controlled subs. i suggest filling one up with a non conductive liquid and sealing it shut. wouldent this let the rover go much deeper?

taylaron

hey,
in a submarine nuclear power plant, one of the forms of radiation is alpha radiation correct and it is identical to helium correct? but does it have orbiting electrons?
it doesnt say so in wikipedia's
although it does say it consists of 2 protons and 2 neutrons. no electrons? or did they leave those out for some strange reason?

i think this is where im wrong
dispite that probability, i'll go on with my idea

couldent you take those helium particles and strip the elctrons from them like in the process used by fuel cells? or the same thing by using the beta emissions (high energy, high speed electrons) to produce electricity.

i think im really screwed up here......

zeta

It's probably not wise me blowing what little captial I have at this forum being a newb and all, but I put in an SBIR proposal after grad school for a propulsion system, based around manipulating the dipole moments of water using electric field gradients. The system as proposed was too small to be practical and I suppose what was gained in noise suppresion was lost in creating a massive EM signature :)

Morbius

tayaron,

No - the alpha particles that come out of a radioactive nuclide DON'T have electrons.

That's why alpha radiation is so harmful - the fact that the alpha particle doesn't have
electrons, means that it is charged. It's actually "doubly charged" - there are 2 protons;
i.e. 2 "+" charges, without electrons to balance that out.

The alpha particle is a charged particle, and as it traverses through matter, there is an
attractive force between the alpha and the electrons. The alpha also has a lot of
energy, so it can, in essence; "pull" electrons away from where they were. That leaves
an ion where the alpha has pulled an electron away.

That's why high energy alpha radiation is "ionizing radiation". It "messes up" the
electron structure of the material through which it traverses. If that material happens
to be proteins or DNA of a living organism - the organism is damaged - potentially
lethaly, as in the case of the spy that was "poisoned".

Fortunately, because alpha particles react so strongly, they lose their energy rather
quickly - so they don't have much of a range and can be easily shielded. You can
shield yourself from alphas with a sheet of paper. The alpha will deposit all its energy
in the paper, and come to rest.

Alpha particles can't get through the dead layer of skin on your body. So alpha particles
outside the body are no problem. But if they ever get IN you - like the spy - then you
have problems.

Obviously in a submarine reactor; alpha particles are ZERO problem. The sub reactor
has enough shielding to stop the gamma, and alphas can be stopped by a sheet of paper.

Dr. Gregory Greenman
Physicist

theCandyman

While we're on the subject of electrons, do plasma ions have all of their electrons stripped? All I keep reading is that plasmas are made of positivly charged ions and electrons. I don't know if that means the ions are just missing one electron or all of them (for cases other than Hydrogen).

Astronuc

In the case of a hydrogen plasma, the electrons are free of the protons (H as 1 p (d or t) and 1 e). Plasma infers that a gas is ionized. Remember the binding energy of a ground state electron in H is 13.6 eV - but plasmas are heated into the keV range - at least on earth. The electrons and nuclei have more kinetic energy than binding energy.

In He, the first ionziation energy is 24.6 ev, as compared to alpha particles which have kinetic energy of several MeV. However, alpha particles collide with surrouding matter, which is ionized, and quickly loose kinetic energy until they slow down and stop where they pickup two electrons.

When an alpha particle is emitted form a nucleus, the charge on the nuclear decreases by 2e. Two electrons then leave the atom and go off in search of a positive charge. Meanwhile the alpha particle is picking up two electrons from some other atom, to there is a cascade of moving electrons.

To have a reliable electric current, one would need a lot of alpha decays, and that is not practical for an electrical source for that and several other reasons.

berkeman

Yes! That was the movie. But it was oxygenated Flourinert. Even though I'm a scuba diver, I don't think I could acclimate to breathing a liquid.

Morbius

Candyman,

Depends on how hot the plasma is.

If you have an atom with atomic number Z, you can strip off one electron, and
have an ion that consists of a nucleus with a charge of +Z, and an electron cloud
of charge -(Z-1) for a net charge of +1.

The quantity Z* [ "Z-star"] tells you what the effective ionization level is. The
higher the Z* the more ionized the atoms.

Dr. Gregory Greenman
Physicist

sid_galt

This is not related to nuclear physics but do you have any idea why the Trident does not just fish for food to give potentially unlimited time underwater until the fuel is exhausted?

theCandyman

How would you like to eat fish everyday for years on end?

Morbius

sid,

A Trident submarine doesn't exhaust its fuel for 20 years!!!

In fact the Trident doesn't even have a hatch over the reactor to facilitate refueling the sub.
After 20 years, when it is time to refuel the reactor, the Navy actually cuts a hole in the
hull of the sub and repairs the hull after refueling. The sub will probably only be refueled
once, and at most twice; in its lifetime.

I confirmed this with the crew when I toured a Trident, the U.S.S. Georgia at what was
then called Subase Bangor in Washington state about 10 years ago. The Georgia has
recently undergone a conversion from a ballistic missile sub to a guided missile sub;
SSBN --> SSGN:

http://www.navy.mil/navydata/fact_di...0&tid=300&ct=4

In regards to fishing, I doubt that they want to open the hull to bring anything inside.
You also don't want to have anything "passing through" the pressure hull; otherwise
you are asking for trouble.

The sub could fish on the surface, but a Trident stays underwater pretty much thourgh out
the mission in order to avoid detection by satellite.

Dr. Gregory Greenman
Physicist

IAMOLBG

what about a small submarine. What would it take for something like that to reach fairly high speeds. It's be submerged for only hours to a day. Manned though. It would be nice if it wasn't nuclear because of size limitations and health hazards.

taylaron

you will need to provide the energy to displace the water around the craft; the energy required for that at 'high speeds' (more specific please) im afraid would be too much at current practical energy/kg metric. a slipstream craft would be best, although the issue is packing enough power in the given space to achieve the minimum speed is a concerning issue. whither its using a propeller or some other method will effect your efficiency. and that's just to propel the device, you need power for the passengers as well. small, sounds relatively large to me.

chayced

Slight change in topic, but I am amazed that the US hasn't invested in Stirling engines for sub propulsion. It seems pretty logical to me, you have primary coolant providing heat directly to the heat engine with a piston and hydrogen between it and the circ water. Maybe it's cost, maybe its size requirements.

Read about a Swedish company that builds Stirling powered submarines, but they are liquid 02 cooled and probably have a high temperature differential.

Oh and the 20 year lifespan of a reactor core is based around alternating at sea times of low power and in port periods of shutdown. If a boat is running at high power for extended periods of time that number can quickly fall. Then again if a boat was driven that hard for that long, it would be time for a complete overhaul anyway.

mgb_phys

They aren't liquid oxygen cooled, they burn diesel fuel and the liquid oxygen is just a compact way of storing O2. The stirling engine can run from the diesel and stored O2 while submerged - the exhaust is dissolved directly into the sea water.
When the O2 runs out you still have a regular diesel electric boat. I assume they could also carry plants to make more LOX while at sea and surfaced. The advantage is that you get much better submerged endurance combined with diesel electric quiet, and you don't have any of that icky nuclear stuff to dispose of.

Nuclear boats are never completely quiet because of the coolant circuit. The Polaris boats were described by an-ex submariner technician as sounding like a "pair of skeletons ****ing in a metal trash can" - I assume they have improved since then.

taylaron

downside to that technique is you can track a submarine that is cooled by the surrounding water by measuring the surrounding temperature of the water. kind of like a hunting dog does a scent. without using the surrounding water to dissipate the heat from the source, you would need a lot of liquid He or O2 or N2 to do anything practical.

chayced

I believe the Stirling's in question were liquid oxygen cooled, just diesel and oxygen fired. It would be a waste to do it otherwise. Guess my comment was a bit ambiguous.

The coolant loop in a nuclear sub is only loud at high driven flowrates. In a natural circulation mode the loudest thing would be the reduction gear and main engine followed by the generators and pumps.

So yes, they have improved since the Polaris boats. From what I understand Trident boats are silent and easier to find by looking for the quiet spot than by looking for the noise they make. Until sonar technology improves its pretty pointless in making a quieter boat, unless of course it can go quietly at high speeds.