BMT SSGT (Ship Submersible Gas Turbine)

[Triton]

From February 2004, BMT Defence Systems unveiled the concept of the SSGT (Ship Submersible Gas Turbine):

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.

http://forum.keypublishing.co.uk/archive/index.php?t-28700.html

BMT white paper on the SSGT:
http://www.bmtdsl.co.uk/BMT/bmt_media/bmt_media/33/2007-09-26Concept-SSGTDataSheet.pdf

 

[amsci99]

Saw this some years back and nothing heard since. Appears doomed to be a paper project, the prospect of having 3rd world navies running a gas turbine drive versus a diesel one is rather unattractive, me thinks.

 

[Abraham Gubler]

The SSGT is not conceived as a replacement for conventional diesel-electric SSKs operated by nations with short deployment ranges. But rather an alternative to long range fleet submarines; diesel-electrics like the Collins class SSG and nuclear powered SSNs. The idea is the semi-submersible SSGT would use the higher power of a gas turbine to sustain a high transit speed to quickly get to the patrol area and then revert to more conventional battery-snorting patrolling.

 

[Triton]

Thanks for the feedback Abraham. Do you believe that the BMT SSGT would be attractive to the Royal Navy, Royal Australian Navy, and Armed Forces Canada?

 

[Abraham Gubler]

Thanks for the feedback Abraham. Do you believe that the BMT SSGT would be attractive to the Royal Navy, Royal Australian Navy, and Armed Forces Canada?

The SSGT was more of an exploration of concepts - how to get SSN type transit speed without bouncing neutrons around the ship. Because of the very high air flow requirements of gas turbines (compared to diesels) it needs to keep the top of the fin above water. I doubt (well I know) this isn't very attractive to submariners.

BMT has shelved the SSGT and focused on the technology that is really exciting to future conventional submarines. That is high power density batteries (Li-Ion, Molten Salt, etc) and high temperature super conductors (HTS). With this kind of technology the next generation of diesel-electrics will be much faster and be able to stay under water much longer. On paper not in the league of an SSN but tactically very, very close (not including the CSG ASW mission) and without the high noise levels of running a reactor.

 

[Aeroengineer1]

Abraham,

You speak with some certainty on this project and the company; do you happen to have anymore information on the project? I enjoy modeling submarines from scratch (currently working on a 1:144th LA Class) for radio control. I have searched for information on this boat, and have only found a few papers on it, with only small not very detailed drawings. All efforts to contact the people that are listed in the papers have not responded back. (Yeah, I know sounds like the typical spy fishing story, though that I am not, just a modeler that is anal about getting things to look right on the outside).

Adam

 

[Abraham Gubler]

All I know about the BMT SSGT is in the context of their presentations to the Pacific 2005 (SSGT) and Pacific 2007 (Vidar) naval technology conferences and further discussions with their staff in relation to the Vidar design concept. You're not going to get much more out of BMT in relation to the SSGT other than what's in the data sheet linked above. It was expressed to me that SSGT was very much their radical outside the box exercise to get their design team thinking laterally and seeing what emerges from such an exercise for more conventional submarine technology.

However just like diesel electrics have spent the past 100 years coasting of all the investment in lead acid batteries thanks to the car/truck industry and alternator/generator technology thanks to the power industry they can now look forward to the next 100 years coasting of the technology investment in high density batteries thanks to the personal electronics industry and compact alternator/generators thanks to the hybrid car industry.

 

[Triton]

Do I understand correctly that the maximum patrol endurance of the Upholder/Chicoutimi-class SSK is 56 days with a maximum continuous-submerged endurance without snorkeling of ten days? A maximum range of 8,000nm at 8 knots?

While the SSGT has a patrol endurance of 60 days and a continuous-submerged endurance, via Air Independent Propulsion, of twenty-five days? A maximum range of 6,000nm at 20 knots and 13,000 nm at 10 knots?

The SSGT seems superior to SSK. Also sounds like it offers some of the capabilities of an SSN at a lower unit and operational cost. It would probably be attractive to navies running diesel boats and a lower-cost supplement to a navy with an SSN force.

 

[Abraham Gubler]

Do I understand correctly

You can certainly quote some open source figures but the way you string them together indicates you don't understand how a submarine operates, what those figures mean and what is important and what not. I'm not about to spend the next five hours of my life explaining those things to you so perhaps you should start reading about submarine operations, watch some TV documentaries or even better find a sympathetic submariner with some time to spare and get a good understanding of the dynamics before quoting figures that are not related as if they are.

 

[red admiral]

There's an excellent model of the SSGT in BMT's offices in Bath. From speaking to some of the engineers there, the current focus is more on cheap modular designs that are able to actually be sold to countries like South Korea. The SSGT was a nice exercise but is pretty much just BMT advertising what they are able to do.

 

[Aeroengineer1]

It is unfortunate that there is not more information available on this concept. I guess that if I ever do it, I will just have to extrapolate the data from what I have. Thanks for the interesting info Abraham.

Adam

 

[jacob]

On SSGT, I have a very interesting PP presentation in PDF format I found in the web three or four years ago. It has some detailed data of the concept and several good pictures. If you are interested give me a mail address and a couple of days...

Regards

 

[Brickmuppet]

I'm a part time surface puke and I don't have much (read any) training or knowledge in sub ops but a few points about the SSGT strike me as problematic.

Gas Turbines require a LOT of air. The designers SEEM to have dealt with this via the perfectly straightforward technique of making the intake really really big. This however means that instead of a snort/snorkel protruding, a good bit of the sail is above the waterline....which would seem to kill the stealth features that is a submarines reason for being. The high O2 consumption would seem to have another downside. A diesel boat that is snorkeling can deal with the air intake being occasionally covered up by a wave in a high sea state, closing up the boat for a moment with a gas turbine running could lead a dangerous loss of pressure in the boat very quickly. There are probably work arounds for this but it seems like a non trivial issue to me.

Gas Turbines are HOT. This means exhaust shouting "Hi IR sensors! Kill me please!" Again, there are ways to mitigate this but as I understand it from open source references they generally require space and running water...which is noisy...which is another blow against stealth.

The blurb says that the turbines are for transit but one of the strengths of submarines is that no one knows where the hell they are. The heat plumes from gas turbines associated with wakes of surfaced sails at 20 kts would likely be very observable from the air or orbit. Satellites are unlikely to be rare birds in the future. Aircraft in theater or IR sensors on a mountain would extend the area that is "in theater" considerably. Even if the sub went quiet a hundred miles out it might have announced its entry into play....reducing its advantage

The big sail looks like it might add to generated noise.

The blurb mentions the higher power capacity of the boat, but if that is due to the very high generation capacity of the turbine powered dynamoes then it is illusory as the turbine is not something you'd want to light off in a war zone unless it was to flee...on the surface...which would indicate that the sub had failed in its mission (be sneaky) and would likely do exactly no good except give a good IR image to facilitate the killing blow.

On the other hand the kerosene based fuel cell, if it works, would seem to be a real boon to submersibles. Even without the O2 tanks the fuel cell would seem to afford a huge reduction in noise while snorting over a diesel. The addition of O2 tanks would seem to give some flexibility. I'd say forget the turbine and put the fuel cell in an off the shelf SSK.

Just my two cents.

 

[Abraham Gubler]

Just my two cents.

Spot on. The 24 hours a day in transit sail above water would completely change the radar detection dynamic of a conventional submarine. Not to mention the air flow and IR signature issues. A typical diesel electric submarine needs to keep its snorkel up for around 8 hours a day in transit (night time) which is an extremely difficult radar target. To detect a submarine mast you need a very high scan rate radar at a very acute angle to the surface (ie low altitude) and even then detection ranges are 5-15 NM. The speed boat sized gas turbine sail structure would be detectable by a high flying aircraft with conventional radar. Making detection and tracking of the transiting submarine as easy as detecting and tracking a corvette.

Knowing when and where the submarine has deployed to the operational theatre takes away its strategic and operational surprise. The enemy can deploy their ASW assets and take other countermeasures. The Falklands War showed how important strategic and operational stealth for submarines is with the Royal Navy's submarines destroying the Argentinian surface fleet while thanks to an intelligence leak the patrol box of the Argentinian submarine was known to the British completely defeating its effort. Its a testament to the silence of a diesel electric submarine in littoral waters that the Argentinian Type 209 boat was able to survive the war considering how much the British threw at it knowing the area it was in.

 

[Yellow Palace]

From what I recall of speaking to some of those responsible for the SSGT a year to eighteen months ago, the gas turbines themselves are in the 'bulb' at the top of the fin. Which solves the problem with fitting the uptakes and downtakes in the fin, at any rate. Probably doesn't do many favours with the centre of gravity though, and I suspect that it could use all the help it could get there.

It was, as Red Admiral says, basically an exercise in pushing the limits of the state of the art, as well as demonstrating the design team's capabilities. As I recall, the main hull was conceived to run at speed just below the surface of the water, which is a regime that nothing much else (if anything at all) is designed for. Which meant of course that the whole thing had to be designed from scratch, making it a great way of demonstrating what you can do.

 

[ouroboros]

If gas turbines typically have higher power density, couldn't you run in a profile similar to a conventional diesel-electric boat with a short surface runtime at night? If the power increase is significant, couldn't you also shorten the exposure time itself? Though it's hard to get away from the IR signature problem, short of dousing the exhaust with pumped seawater. Well, unless you are crazy enough to try to do a heat recovery via a steam generator in the turbine exhaust like a land based coal power plant.


I wonder if there is any merit to using a small snorkel mast and precharging the necessary air into storage, similar to AIP? There's a related bit of technology in development now for a gas turbine that replaces the combustor with a fuel cell, using the compressor to get air up to the pressures needed for the fuel cell, then running the exhaust through a conventional turbine section. Instead of using a conventional matched gas turbine compressor, you use something that better matches a small snorkel's mass flow requirements and precharge your air storage. If the turbine runtime for equivalent energy output is substantially below a diesel, the idea may have legs.

A setup like that does create some problems though. You would have two masts unless you are willing to take the operational flexibility hit of exclusively requiring precharged air to run the turbine. There is the related problem of the mass flow of the exhaust. The provided images show the turbine housing as a bulb at or above sea level. I assume there are some very difficult engineering problems with trying to keep the the turbine running below sea level. You would either use a thick snorkel and pipe the exhaust way up (which puts you back into the thick snorkel/surfaced turbine bulb problem), or have some sort of annular blocking valve and keep the exhaust below sea level. If the exhaust can be kept below sea level, then the thin snorkel precharge could have merit as it's possible to have a conventional sub's profile (well, short of the enormously loud gas turbine exhaust dumping directly into the ocean), but it wouldn't necessarily solve the turbine bulb exposure transit problem.

I wounder why the turbines aren't mounted vertically, either inside the fore or aft part of the sail, rather than a top mounted bulb?


Someone pointed out to me an interesting gas turbine technology being developed by a company called RamGen. It's basically a ramjet mounted on the edge of a disk, slightly angled so it intakes air from the top of the disk and exhausts towards the bottom of the disk. The idea being you spin up the disk so the intake is supersonic, so the ramjet inlet can compress intake air, shove the air through a ramjet combustor, then exhaust through a ramjet exhaust to increase the speed of the exhaust to supersonic speeds. Since it's a rotating frame of reference, the exhaust usually ends up being subsonic. Efficiency and compactness is very interesting, in the case where it's a full ramjet on the edge of the disk, including combustor (the company has been recently focusing work solely on the ram compressor stage for use in gas compression projects since that seems to be a faster path to money). There was some side talk that tweaking the exhaust nozzle could drop the exhaust temperature significantly, due to simple gas dynamics.

 

[Triton]

Artist's impression of BMT SSGT.

Source:
http://www.militar.org.ua/foro/submarinos-y-mas-submarinos-t3751-225.html

 

[Scott Kenny]

Problem is, you can't drive very fast at periscope depth without showing a lot of wake, and you will run into control issues keeping depth.

You're NOT going to do 20 knots broached like that. You'll be lucky to do 14, and even going that fast will beat the crap out of the screw from cavitation and let everyone in the world know where you are via radar and wake.

 

[shin_getter]

I was just thinking about the K-Class submarines, and it hits me.

Was there fleet submarine concepts using gas turbines in the 40~50s? Would it be a thing if nuclear technology wasn't developed as the next big new thing due to the war?

 

[Grey Havoc]

Here was one such concept for the Royal Navy:

Submarines

To avoid detection by surface ships, in the mid-1960s Wallis proposed a fast, deep-diving submarine. The high pressures would be met by a novel Wallis hull structure based on several interconnecting cylinders of small diameter, rather than the single large cylindrical pressure hull used on contemporary (and modern) submarines. Propulsion would be provided by a closed-system gas turbine, the engine breathing liquid oxygen from tanks on board, and recycling the condensed exhaust gases back into the empty tanks. Both the hull form and propulsion systems were investigated in detail, but were not thought to offer significant advantages, and were not taken up.

View attachment 661129

Sir Barnes Wallis - Other Projects

Sir Barnes Wallis

www.sirbarneswallis.com

 

[Scott Kenny]

I was just thinking about the K-Class submarines, and it hits me.

Was there fleet submarine concepts using gas turbines in the 40~50s? Would it be a thing if nuclear technology wasn't developed as the next big new thing due to the war?

I dunno.

GTs need 4x the amount of air that an equivalently-powerful diesel engine needs to ingest. So instead of say an 18" diameter snorkel mast on a 688/774 class, they'd need a 36" diameter snorkel mast.

Not impossible, but that is a scary large hole that needs to shut really quickly if it gets wet.

 

[acelanceloet]

And since gas turbines cannot have back pressure, you also need an exhaust that comes out of the snorkel itself with a similar diameter. Which is a lot harder to make undetectable.

 

[Nicknick]

I don’t see the point in replacing a Diesel elektric system with gas turbines. I’m guessing, that regenerative gas turbines are intended, because other wise the part load efficiency would be catastrophic. Even then, the efficiency would be significantly lower than that of Diesel engines (even the relative truck engines achieve more than 50% nowadays!) and the air mass flowing in/out and through the sub would be much higher with bulkier piping going through the sub. Gas turbines also tend to loose more efficiency with pressure losses in the intake/exhaust system than Diesels, so there are very good reasons, why nobody built a gas turbine driven sub.

 

[A Tentative Fleet Plan]

IIRC, @RP1 said the purpose of the design was to provide SSKs with similar transit speeds to SSNs.

Edit: Described in the original papers:

 

[Scott Kenny]

And since gas turbines cannot have back pressure, you also need an exhaust that comes out of the snorkel itself with a similar diameter. Which is a lot harder to make undetectable.

Eh, just stick a huge Roots blower in the exhaust stream. or 4x smaller ones. Though "smaller" is distinctly a relative term. The single big diesel on an Ohio has a 7500cfm blower, the blowers we use to dry out the ballast tanks are 2500cfm.

And that diesel on an Ohio is 1 of 4 that were fitted to a WW2 Fleet sub or the Barbel class. So you'd need something absurd like 16x 7500cfm blowers.

 

[Nicknick]

Reducing the expansion of the turbine ratio so that it fits to an higher back pressure would be simpler and even more efficient

 

[acelanceloet]

Roots blower? so basically suck out the exhaust stream so the backpressure is zero or even negative? does that not take a lot of power for the amount of hot air we are talking about here?

 

[acelanceloet]

Reducing the expansion of the turbine ratio so that it fits to an higher back pressure would be simpler and even more efficient

I wonder how much power loss that would lead to. Assuming a 10 meter water depth, it would double the atmospheric backpressure it would otherwise get. What would the internal pressure be between the gas generator and the power turbine? so much that such an backpressure would be almost insignificant and could be solved by just letting the power turbine take less power?

 

[Scott Kenny]

Roots blower? so basically suck out the exhaust stream so the backpressure is zero or even negative? does that not take a lot of power for the amount of hot air we are talking about here?

Yes. (I'm coming from nuclear power, so the idea of needing to worry about every watt is a bit new)

Not ideal, and it's why several of the SSGT designs had the GTs up in the sail entirely with the GTs only running while broached. No snorkeling at all.

 

[Nicknick]

I wonder how much power loss that would lead to. Assuming a 10 meter water depth, it would double the atmospheric backpressure it would otherwise get. What would the internal pressure be between the gas generator and the power turbine? so much that such an backpressure would be almost insignificant and could be solved by just letting the power turbine take less power?

When you pipe the exhaust above the water level, the 10 m water pressure doesn't matter at all. Please note, that the turbine power depend on the pressure ratio, not the arethmetic difference, so 1bar back pressue will reduce the power output very significantly. For regenerative turbines this would be especially critical, since the overall pressure ratio is quite low (about 4:1). The turbine power is proportional to (p1/p2)^((k-1)/k). p1 is the entry pressure (absolute) and ps is the pressure directly behind the turbine (absolute). I assume k to be arount 1.3 for the exhaust gases. Note that the impact on the net power output is even higher, since the compressor power has be substracted.

 

[acelanceloet]

When you pipe the exhaust above the water level, the 10 m water pressure doesn't matter at all. Please note, that the turbine power depend on the pressure ratio, not the arethmetic difference, so 1bar back pressue will reduce the power output very significantly. For regenerative turbines this would be especially critical, since the overall pressure ratio is quite low (about 4:1). The turbine power is proportional to (p1/p2)^((k-1)/k). p1 is the entry pressure (absolute) and ps is the pressure directly behind the turbine (absolute). I assume k to be arount 1.3 for the exhaust gases. Note that the impact on the net power output is even higher, since the compressor power has be substracted.

You misunderstand me

The 10 meter water difference would be if I chose a less efficient power turbine, leaving some more power in the exhaust gas from the turbine installation so I could vent it below the waterline without backpressure issues. I assumed that was what you meant with your post?

 

[1635yankee]

To continue piling onto this concept....

A friend (who retired as a destroyer captain from the USN) described diesel-electric submarines as mobile minefields (this may not be original to him). He also reported that modern DE boats running on battery are more difficult to detect than nuclear boats, as nuclear boats are larger and they have more moving parts in the reactor, turbines, and reduction gears than in the batteries and motor(s) of a diesel boat.

Of course, a close-cycle gas turbine could be practical, possibly a nuclear CCGT, the latter once one spends the few hundreds of million in R&D to get one working (in defense of this concept, sometime in the deep, dark past, there was an article in one of ASME's journals proposing a nuclear CCGT plant for nuclear-powered surface ships, as it would be lighter and more compact than a PWR-based system. Alas, I no longer have either ASME membership or the journal).

 

[Scott Kenny]

To continue piling onto this concept....

A friend (who retired as a destroyer captain from the USN) described diesel-electric submarines as mobile minefields (this may not be original to him).

Not a bad description, though it may actually date to WW2. Definitely dates to the Type XXI "e-boot" in post-war testing and Nautilus.

He also reported that modern DE boats running on battery are more difficult to detect than nuclear boats, as nuclear boats are larger and they have more moving parts in the reactor, turbines, and reduction gears than in the batteries and motor(s) of a diesel boat.

Yes, that's one of the advantages of turbo-electric drive like the French use. No reduction gears to make noise.

Then there's other bits and pieces you can do to further quiet nuke boats:

• But even the Ohios or Seawolves could not run at full power on Natural Circulation. I believe that the new Columbia class and Ford class can run at full power on natural circulation, however. Took a while to work that out.
• Then you add scoop injection main seawater, so you don't need pumps to cool the secondary. That's how the Narwhal SSN671 worked, but it required violating the rules on SubSafe valve sizes (scoops are a LOT bigger than what you need for pumps). IIRC the Soviet Typhoon class also uses scoops.
• I _think_ there's a way to get the secondary loop to run without needing pumps, but I'd need to sit down and sketch a lot to even come up with an idea.

Until you apply all that stuff, a good SSK or AIP boat is quieter.

Of course, a close-cycle gas turbine could be practical, possibly a nuclear CCGT, the latter once one spends the few hundreds of million in R&D to get one working (in defense of this concept, sometime in the deep, dark past, there was an article in one of ASME's journals proposing a nuclear CCGT plant for nuclear-powered surface ships, as it would be lighter and more compact than a PWR-based system. Alas, I no longer have either ASME membership or the journal).

I'm not entirely sure how well that'd work with getting enough heat out of the GT for the nuclear plant.

But if someone can find a copy of that article I'd love to hear more about the proposal!

 

[TomS]

Not a bad description, though it may actually date to WW2. Definitely dates to the Type XXI "e-boot" in post-war testing and Nautilus.



Yes, that's one of the advantages of turbo-electric drive like the French use. No reduction gears to make noise.

Then there's other bits and pieces you can do to further quiet nuke boats:

• But even the Ohios or Seawolves could not run at full power on Natural Circulation. I believe that the new Columbia class and Ford class can run at full power on natural circulation, however. Took a while to work that out.
• Then you add scoop injection main seawater, so you don't need pumps to cool the secondary. That's how the Narwhal SSN671 worked, but it required violating the rules on SubSafe valve sizes (scoops are a LOT bigger than what you need for pumps). IIRC the Soviet Typhoon class also uses scoops.
• I _think_ there's a way to get the secondary loop to run without needing pumps, but I'd need to sit down and sketch a lot to even come up with an idea.

Until you apply all that stuff, a good SSK or AIP boat is quieter.



I'm not entirely sure how well that'd work with getting enough heat out of the GT for the nuclear plant.

But if someone can find a copy of that article I'd love to hear more about the proposal!

Here are a couple of less technical articles on CCGTs for submarine applications.

HTGR GAS TURBINE POWER PLANT FOR SUBMARINE PROPULSION IN THE 21st CENTURY - NSL Archive

Pressurized light water reactor plants have provided an effective, safe and reliable submarine propulsion system for over three decades. The next generation of nuclear submarines…

archive.navalsubleague.org

https://www.usni.org/magazines/proceedings/1994/june/submarine-engines-future

And a listing for the Naval Engineers Journal article I'd really want to read:

Closed Cycle Gas Turbine Nuclear Power Plant for Submarine Propul...: Ingenta Connect

www.ingentaconnect.com

 

[Scott Kenny]

Here are a couple of less technical articles on CCGTs for submarine applications.

HTGR GAS TURBINE POWER PLANT FOR SUBMARINE PROPULSION IN THE 21st CENTURY - NSL Archive

Pressurized light water reactor plants have provided an effective, safe and reliable submarine propulsion system for over three decades. The next generation of nuclear submarines…

archive.navalsubleague.org

https://www.usni.org/magazines/proceedings/1994/june/submarine-engines-future

Hrm. I still think the submarine version will need to dump some waste heat into the ocean, but I mostly follow the design concepts now.

And a listing for the Naval Engineers Journal article I'd really want to read:

Closed Cycle Gas Turbine Nuclear Power Plant for Submarine Propul...: Ingenta Connect

www.ingentaconnect.com

Wanna split the cost?

 

[Yellow Palace]

A friend (who retired as a destroyer captain from the USN) described diesel-electric submarines as mobile minefields (this may not be original to him). He also reported that modern DE boats running on battery are more difficult to detect than nuclear boats, as nuclear boats are larger and they have more moving parts in the reactor, turbines, and reduction gears than in the batteries and motor(s) of a diesel boat.

Think of the SSGT as a diesel boat with the strategic mobility of a nuclear boat, and the ability to recharge its batteries very quickly.

The CONOPS called for fast transits in a semisubmerged mode (the top of the fin above water, the remainder of the hull submerged), with an air induction mast extending above it. In this mode, it would be clearly detectable, but able to advance at 20 knots. The weird hullform was designed to facilitate this mode of operation.

In the area of operations, it would be a large, advanced AIP boat - noting that it's a concept design from 20 years ago - capable of all the normal AIP boat things, but having enough power to approach nuclear boat performance.

The designers weren't amateurs and had considered the objections raised in this thread. The paper you want for all the operational details is 'SSGT - "In Step" High Mobility Submarine' from the Warship 2004 conference.

 

[A Tentative Fleet Plan]

The designers weren't amateurs and had considered the objections raised in this thread. The paper you want for all the operational details is 'SSGT - "In Step" High Mobility Submarine' from the Warship 2004 conference.

For those who are interested:

https://www.jstor.org/stable/48600755

 

[Nik]

Those monster RN 'Cruiser' subs with their steam-powered surface engines cast a long, lonng shadow.

Okay, torpedoes were big and quirky, and there was a hard limit to how many reloads you could carry compared to eg shells for a deck-gun wrought monstrous. Cruise on surface, submerge for stalk, pop up, shoot target amidships, be gone before debris came down...

Snag, of course, is that hull openings must be many and large, so 'Murphy Bait'. Hence cruel run of mishaps and out-right disasters...

Do we know if a self-contained deck-pod was considered, deploying, a second, telescopic sail with only control and electric power connections to main hull ??
--
Tangential, there was mention in earlier posts about USSR subs that could deploy 'scoops' to assist cooling: Is this related to the infamous 'Caterpillar' drive featured in eg 'Hunt For' ??

 

[Firefinder]

Another question for me be does the turbine need to be big enough to actaully DRIVE the sub.

As in have the... Full 7000 horsepower rating from 3 diesels going by the Collins.

or Can you use a smaller single turbine used to charge the Batteries?

Like there is serouis talk of making a pure battery power attack sub thanks to new batteries having enough power to make that feasible. Heck tge Japanese newest subs do away with their AIP systems to double up on batteries so the AIP unneed. So take that concept...

But can you use a smaller turbine to extend the range instead of a similar rated diesel to save weight or space? With that savings being used for more batteries or fuel.

 

[A Tentative Fleet Plan]

Another question for me be does the turbine need to be big enough to actaully DRIVE the sub.

As in have the... Full 7000 horsepower rating from 3 diesels going by the Collins.

or Can you use a smaller single turbine used to charge the Batteries?

Like there is serouis talk of making a pure battery power attack sub thanks to new batteries having enough power to make that feasible. Heck tge Japanese newest subs do away with their AIP systems to double up on batteries so the AIP unneed. So take that concept...

But can you use a smaller turbine to extend the range instead of a similar rated diesel to save weight or space? With that savings being used for more batteries or fuel.

The turbines are there to give the sub 20 knot transit speed.

As per the Warship 2004 Conference paper, the turbines are described as being "from the "low" power end of the aerospace practice and would be based on naval helicopter units for their robustness". Initial plans were for 16,000rpm 1.8 MW, with the hope that 2.7MW, and a growth option of 3MW and 20,000rpm sets would be feasible in the next 15 years.