Non-Nuclear Submarine Propulsion Thread

http://www.bmtdsl.co.uk/default.htm?ID=1

SSGT DRAWS ADMIRING CROWDS AT PACIFIC 2004

BMT Defence Services Ltd unveiled its concept for a high mobility submarine at the Pacific 2004 maritime exhibition in Sydney, Australia, at the start of February.

A model of the SSGT (Ship Submersible Gas Turbine) was displayed on the BMT Defence Services stand at the show, attracting interest from naval delegations and defence sector professionals from many Pacific Rim regions and countries including Australia and New Zealand; south-east Asia, Canada and the USA during the four day event that began on 3rd February 2004.

Marketing Director for BMT Defence Services, John Davis, explained the key benefits of the design to those viewing the disruptively-patterned submarine model: “SSGT is designed to provide effective mobility approaching that of an SSN without the financial and political costs of ownership associated with having a nuclear reactor onboard”.

Conceived by design engineers at BMT Defence Services in Bath, UK, the SSGT sees the first serious proposal for using gas turbines in a conventional submarine. Though gas turbines can be very compact they are voracious consumers of air and submarine designers have to date been unable to arrange sufficient volumes of air to feed gas turbines buried inside the hull of a submarine.

The innovation proposed by BMT Defence Services, in consultation with gas turbine specialists Rolls Royce, is to locate two independent gas turbine-electric alternator sets in individual containments located in a bulb at the top of the submarine fin where they can draw sufficient air through an 8m tall induction mast. When operating on gas turbines, the submarine runs semi-submerged, with just the gas turbine bulb above the sea surface. In this mode, SSGT is able to travel up to 6,000 nautical miles at 20 knots, far in excess of the capability of a conventional diesel-electric submarine.

The SSGT design trades off tactical covertness of the submarine against strategic mobility on the assumption that the submarine will meet few, if any, threats during transit. Once in-theatre, SSGT shuts down its gas turbines, dives and can operate fully covertly for up to 25 days in an Air Independent Propulsion mode (AIP). A mixture of fuel cells and advanced ZEBRA batteries provide power for systems and permit submerged operations up to 10 knots and short tactical sprints at 30 knots respectively. Kerosene is used to fuel the gas turbines and (via reformers) the fuel cells thus giving deep flexibility between transit and in theatre operations. Liquid oxygen is stored to enable the fuel cells to operate when the boat is submerged. SSGT may also run its fuel cells at the surface taking air using a conventional snort mast. In this way the boat may be more covert whilst in transit and preserve the stored liquid oxygen to maximise discretion in theatre.

Well resourced in onboard power, SSGT supports a highly capable and comprehensive combat suite including chin, fin and flank sonar arrays, six heavyweight torpedo tubes, eight vertical launch missile tubes and stowage for four large unmanned underwater vehicles (UUV) or swimmer delivery vehicles (SDV). Accommodation for up to 12 special forces personnel and a six-man lock-in lock-out chamber complete a flexible design capable of undertaking a range of high and low level missions.

Here is a picture and some additional facts I found about the new German generation of submarines – the U 212 class:

tonnage: 1500 tons
lenght: 56 m
height: 11.5 m
pressure vessel diameter: 7 m
navigable diving depth: > 450 m
crew: 24 men

The U 212 is a next generation submarine because of the completely new power system. The U 212 has an hybrid engine. One possiblity is to produce electricity in fuell cells only with oxygen and hydrogen, which is very quiet and allows almost soundless diving. The tanks for the fuell cells are outside the pressure vessel. With these system the submarine can stay under water for several weeks or even months without coming up. Also the submarine can be powered with a normal 16 cylinder MTU diesel engine, which still needs oxygen from outside of course. The material for the pressure vessel is a special developed non magnetic steel (Werkstoffnr. 1.3964). It’s a very solid and highly elastic kind of steel – which is quite useful in case of a ground contact. The German navy has ordered four of them up to now – with the first one already delivered, but due to the fact that the first submarine’s performance was outstanding during the trials, others will probably follow soon.

Weapons and Sensors:

– 6 torpedo tubes (asymmetrical two 3 tube rows)
– heavy DM 2 A 4 torpedos (launched with a water ram = less noise …)
– towed-array sonar (long range, low frequencies)
– flank-array sonar (low and medium frequencies)
– “Zylinderbasis” (passive, medium frequencies)
– Passive Ranging Sonar (PRS) Basis (bearing and range)
– Intercept Basis (interception of other sonar emitters)
– ESM Fl1800
– attack periscope SERO 14
– normal periscope SERO 15

Can anyone explain the Stirling engine … I never understand why an engine using the striling thermodynamic cycle would be an AIP. It will also need a comburant like Oxygen …

Well from what I know subs with Stirling AIP do indeed carry a load of LOx
to use as comburant. I think they burn diesel to heat up the gas (Helium?)
inside closed chambers with piston(s) inducing their motion with heating and cooling cycles. Why is this advantageous over closed cycle diesels?
I don’t
know for sure but I think it maybe related to noise. If it burns the fuel without
the detonations of the diesel cycle it could be a way to reduce vibrations,
but that is beyond my knowlege.

I am not sure but maybe the different shipyard have different concept for their submarines …

For instance, german submarines were firstly conceived for the german navy, which used to see the baltic as its main fighting zone. This would lead to specific characteristics on range, endurance and usefull depth. The fuel cells are thus needed to stay underwater silent more time.

French and russian submarines are surely meant to operate far from their bases after a long journey. They are probably more adapted to open ocean. A noisier MESMA engine is not so an inconvenient because it would be used after attacking, when the submarine is fleeing retorsion at full submerged speed, like a nuclear one. Great power output is thus needed.

Can anyone explain the Stirling engine … I never understand why an engine using the striling thermodynamic cycle would be an AIP. It will also need a comburant like Oxygen …

I also think that the placement of the LOx tank inside the pressure hull,
like in the 214, is not a very good idea safetywise. Rubin should have opted for the 212 design
solution with the tanks outside the pressure hull.

Considering the size of the LOX tank I doubt it would matter very much where in the sub it was placed. Much like detonating the entire torpedo load of the Kursk meant its double hull design couldn’t save it I doubt it would matter where you put a very large tank of Liquid oxygen.

tks man, hey if u got sectional diagrams plz do post it, i like sectionals very much 😀 ….

but i did not yet got any replys from anyone else on the diesel engines, its layout, etc etc ….

and also pic request of Scorpene that was launched for chile (in Scorpene thread) …

Unfortunately I don’t have any new sectional diagrams or pix of Scorpene. 🙁
Anyway, today there is a thread on Amur’s best selling point:
http://forum.airforces.info/showthread.php?t=28832

tks man, hey if u got sectional diagrams plz do post it, i like sectionals very much 😀 ….

but i did not yet got any replys from anyone else on the diesel engines, its layout, etc etc ….

and also pic request of Scorpene that was launched for chile (in Scorpene thread) …

Nice thread, Blackcat.

I would like to begin with some considerations regarding the 4 AIP technologies currently available:

– Fuell cell – this is currently the most advanced and promissing technology. As it
has no major moving parts and drives directly the electric motor in the vessel, its quiteness is unmatched by the
other current AIP systems. Its disadvantage is the presence of LOx and LH2 containers
inside a vessel where a fire or an explosion can mean the loss of the whole crew.
Related to this is the disavantage of having to store and handle 2 completely different
types of fuel inside the sub.
Marketed in Gemany by HDW for the Type 212/214, and in Russia by Rubin for its
project 677/ Amur 1650.

– MESMA – closed cycle ethanol/LOx steam turbine. noisier than fuel cells because of
its moving parts and the disposal of the LOx/ethanol combustion gases. Has a high level of power output but, like the fuel cells requires a different fuel type stored
in the vessel and the aditional plumbing required.
Marketed in France By DCN for Agosta 90 and Scorpene subs. Not very bright development
prospects since there are rumors that DCN is studying the option of incorporating a fuel cell in the Scorpene.

Stirling Engine – Oldest AIP system. Quiet, although is said to be louder than
the fuel cells due to the piston motion. More than decade of operation in the Swedish
navy shows its maturity and reliability, although its not very high level of power output puts a question mark in its
ability to compete with more modern and performant technologies.
Marketed in Sweden by Kokums, that has been recently bought by HDW…

Closed Cycle Diesel – Diesel engine that can use LOx as oxydizer as well as atmospheric
oxygen. Does without the aditional storage volume and plumbing of other systems that
use 2 fuels. Problem is that when you need high underwater speed the diesel will
have to take over the electric propulsion and your enemy will be listening…
There is also the problem of the diesel’s exhaust underwater.
Marketed by Dutch and German companies whose names I don’t recall.

Now for the Subs:

Scorpene – made in France by DCN, it has a very good sensors/weapons combo.
it’s main drawback is that the MESMA AIP is widely regarded as noisier than the
fuel cells. Should DCN go ahead in making a fuel cell option available, it could
become much more competitive in relation to the HDW products.

Amur – The replacement for the highly successful Kilo in the Rubin Design Bureau
product line. It is rumored to be very stealthy, could be even quieter than the
212/214, although ambitious conceptual targets could prove elusive when the
real hardware will be put to test. The sensors and data processing systems should
lag behind its western competitors. OTOH it can deploy the Klub missile, whose range
is unmatched by Exocet or Harpoon. Scorpene and 214 will have to wait for the Scalp-Naval. I also think that the placement of the LOx tank inside the pressure hull,
like in the 214, is not a very good idea safetywise. Rubin should have opted for the 212 design
solution with the tanks outside the pressure hull.

Since I am on this subject I would like to add, regarding the supposedly new chinese
diesel sub, that the stepped structure above the hull, that many see as an influence
of the Kilo design, could instead be the place where the LOx tanks of the AIP system
are located, having them outside the pressure hull like on the type 212.

Type 212/214 – Very good combat systems, fuel Cell AIP and decades of experience
in diesel sub design, makes the 212/214 the most competitive design currently on
the market. As I mentioned above I don’t like the way the LOx tanks were placed
in the 214, but that is the about the only criticism that I can maake to that design.

Moray – Could be more competitive if it had a less noisier AIP than the closed
cycle diesel. As it is, it is not very probable that this design will ever be successfull
in the export maket.