Why no Gas Turbines for AIP-SSKs?

[santi]

I suppose you know about the exotic BMT SSGT concept of 3-4 years ago. It’s the most serious approach I know to a GT propelled sub.
I left the link to a pair of doc’s and to some images. Up to the moment no one seems to have showed public interest on it, but…

The docs:
http://www.bmtdsl.co.uk/BMT/bmt_media/bmt_media/33/2007-09-26Concept-SSGTDataSheet.pdf

http://www.bmtdsl.co.uk/BMT/bmt_media/bmt_media/33/SSGTcasestudyformatted.pdf

The images:
http://i5.photobucket.com/albums/y168/rgc/SSGT_2.jpg
http://i5.photobucket.com/albums/y168/rgc/SSGT.jpg
http://i5.photobucket.com/albums/y168/rgc/SSGT_5.jpg

Regrads

 

[Distiller]

What do you mean by surface ops????
Distiller have you ever been on a submarine at sea let alone in rough weather?
It is not a nice place to be.
People get hurt, equipment get damaged It is not an acceptable trade-off.
Current submarine batteries are lead acid which are a very temperamental battery.
The navy was looking at trying a dry cell battery but with any battery you are limited in your charging and discharging currents.
Which effects such things as how long you can run at high speed for and charging rates.

...

No, I'm an airforce guy.
But I'm aware of the limitations of light vessels in rough seas.

With "restrictions" I basically meant "don't go there" when it's bad and avoidable (with a fast-transit capability you could go around the worst part), or dive. I guess a diesel SSK doesn't like to surface during a storm either. I had the effects of spray and breakers on the GT air supply in mind.


@ the BMT concept. I'm afraid placing GTs up on the sail would cause severe imbalance. A GT/generator complex capable of pushing the boat to 30kts would have to have at least 5000kW, which probably would put one tonnes up there. My idea is to dimension it strictly for the battery charging process and keep the surface speed up by minimizing drag. A little more than 20kts surfaced.

 

[santi]

Well, it seems that SSGT design was conceived in order to minimize the drag sailing in surface or “semi-submersed”.
This is one of the problems with subs. They are thought to sail submersed and the design needed for that it’s a bit incompatible with good characteristics surfaced, so you need a lot of power if you want high speeds.
If you need high battery power you need, if possible, high power on diesel (or TG in our case) to reduce charging time. For a 4 Kw battery set not less that 3 Kw on diesel (or TG) would be needed, so you can sail in surface (or snorting) with enough surplus for recharge it in an optimal way. Of course, you can use batteries in surface sail but the max speed would be ever lower than submersed (the natural environment of a sub) and you spent precious energy needed under the sea.

SSGT has a 5.4 Mw GT plant, more or less the same output than in a CH-47F helo. I don’t know how much that supposes in weight, one or two tons? may be, but, is it a big trouble in a 4.000 t ship?
Of course, the sail is one of the big burdens on this design but I think that more concerning its behaviour in “semi-submersed” mode than for “severe imbalance”.

Regards

 

[Lofty_DBF]

Distiller...... a Collins class submarine displaces 3300 tons of water when its dived it is not a small submarine.
At periscope depth in rough weather it is extremely hard to keep depth you can feel the effects of rough weather even down to depths of 100m.