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Royal Navy 1960s Depot Ship Design for East of Suez

A Tentative Fleet Plan

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As a result of a December 1964 request from the Indian Prime Minister Lal Bahadur Shustri in London for a joint US-Soviet nuclear guarantee, the UK Foreign Office drew up a discussion paper with the Ministry of Defence on British nuclear forces outside of the NATO area. A follow-up Foreign Office Planning Staff submission argued that Britain should maintain a nuclear capability East of Suez, but recognised that the tenure of the Singapore Base could not be guaranteed indefinitely, and that an alternative means of maintaining this capability should be studied.

An initial Navy Department study on Polaris Deployment East of Suez in January 1965 found that with 5 boats it would be possible to maintain one submarine on patrol on the Indian or Pacific Ocean. However with a reduction to 4 boats, this could not be maintained "without very expensive support facilities which at the present do not exist nor are planned."

A new depot ship to support the Polaris submarines would cost £18-20 Million and would take six years to build and deploy and the force would require a suitable base, one of the options being Fremantle, Australia. At the end of January, the 5th Submarine was cancelled, and as a result of the high cost of the depot ship, the subject received little thought for several months.

In June 1965, the Navy Department pointed out that was already planned for use by other submarines East of Suez, and was intended to be ordered in October 1968 and available in July 1972. If the ship was fitted "for but not with" the handling facilities for Polaris with the addition of only £0.5 million to the final cost. With two years of notice, and £4 Million for fitting out the depot ship would enable deployment of Polaris submarines East of Suez. The Chiefs of Staff (COS) recommended that this be pursued, to which Denis Healey agreed.

In January 1966, Harold Wilson requested that the Overseas Policy and Defence Committee (OPD) to draw up a paper. This identified several issues with the scheme, including that the submarines would not be in range of their targets in transit, the difficulties of setting up communications providing relief crews and siting the depot ship. There were also complications with West Germany over the proposed Atlantic Nuclear Force, of which the Polaris submarines were intended to be part of.

Around the same time a COS memorandum argued that from 1969, when all Polaris submarines were in service, and using Britain as a base, it would be possible to maintain one East of Suez for 6 months in an emergency. Maintaining this on a permanent basis would require the Depot ship or a base (possibly in Guam, which would require dollar expenditure).

The design for the depot ship had now increased to £3-5 million with a decision to proceed being required by May. The OPD Official Committee felt that this option was too expensive, and the depot ship should be built without Polaris facilities. However, further studies showed that the two designs considered (with and without Polaris) were not as incompatible as assumed earlier, and the total cost difference was reduced back to £0.5 million.

The scheme gained a degree of relevance when as part of the February 1966 Defence White Paper, CVA-01 was cancelled. It was suggested that sending submarines East of Suez could be a viable means of maintaining British prestige East of Suez at low cost.

In January 1968, it was decided to withdraw from East of Suez by March 1971. Despite this, the plan to maintain the capability to send Polaris East of Suez survived as a result of continued support from the scheme by the Harold Wilson and several other Ministers.

In March 1968, the Navy cancelled the planned Indian Ocean Depot ship, as existing ships could support could support their European committments.

The deployment of the Polaris East of Suez would now cost £35 million in capital, and £5 million to maintain.
Despite this, the scheme continued to persist, and it was conceded to Wilson that the deployment option could be revived with 5 years notice, and the construction of the depot ship.

It was only in June of 1968, that Denis Healey informed OPD that the option to keep open to deploy Polaris East of Suez would no longer be maintained.

Source: Professor Matthew Jones "Polaris, East of Suez: British plans for a Nuclear Force in the Indo-Pacific, 1964-68"
 
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JFC Fuller

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The design of the ship was complete at the point of cancellation. According to lore the engines (Ruston diesels) had been ordered and were ultimately used in the first three Rover class oilers instead, in which they proved so troublesome they subsequently had to be replaced.
 

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uk 75

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Interesting to compare a drawing of the Rover class funnel
 

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Hood

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Interesting that the helideck could accomodate Chinook.
Of course Chinook was still in leading contention until May 1965, so when the tender was designed it would have seemed natural enough that the Chinook would enter service.
It raises the question if provision was there to allow a Chinook to do some ASW screening for the Resolution-class submarine when it departed. SSBNs like to leave harbour undetected so they are not tracked in shallower waters where its harder to hide. Presumably operating from a tender miles away from good MPA coverage and supporting escorts might have made it harder to properly screen there were no Soviet subs lurking around before the SSBN departed to begin its mission.

It also raises the question if the RN saw the Chinook as potentially fulfilling a heavy-lift function too, which OR.358 seemed to leave to RAF interest in Chinook.
 

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Sizewise, evidently fairly comparable to the USN's contemporary EMORY S. LAND class, and slightly earlier SIMON LAKE class which had Polaris handling capability. This ship would presumably have replaced one or both of HMS FORTH and HMS MAIDSTONE - noting that MAIDSTONE paid off whilst the discussions about the new ship were ongoing.

Comment over on the Ships Nostalgia forum discussing the engines suggests that the depot ship was to be diesel-electric with eight Ruston AO-series V16 engines. The diesel-electric plant corresponds to the inboard profile posted by JFC Fuller, with engine rooms forward and a 'propulsion machinery space' aft which would presumably have contained the propulsion motors.

Eight engines sounds improbable, though. The AO16 produced about 8,000bhp, which would imply 64,000bhp installed. Considering that the comparable USN ships had a 20,000shp steam turbine plant, this is wildly excessive. Given two equal-sized engine rooms, I'd suggest a plant of either two or four engines more likely: the four-engine configuration is probably still overpowered, but this might make sense if the main machinery was also expected to supply electrical power for ships services. Two engines would likely provide sufficient propulsion power - the slightly smaller ADAMANT only had 8,000shp steam turbines - but I'd expect to see just one engine room in that case. The only way I can see eight engines making sense is if two ships were planned with four engines each, but I'd expect to see mention of a second ship if that were the case.

My assumption would be that the flight deck is purely for cargo and freight transfer. It doesn't really look like there's provision for the necessary features to support an ASW helicopter, certainly not permanently embarked which would probably be necessary if required for delousing. I'd expect such requirements to be met by shorebased aircraft - taking Fremantle as the kind of place intended, operating a detachment of MPAs wouldn't be prohibitive, and it's not like Kinloss or St Mawgan are on the Clyde. It would make sense to provide for the largest probable heavy-lift helicopter to land on, so I think it's more likely that compatibility with the OR.358 type was required. Which, as noted, would realistically have meant Chinook.

Incidentally, the reliability issues with the AO16 do not bode well for the various diesel-powered frigate and corvette proposals of the mid-1960s planned around that engine.
 

JFC Fuller

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Eight engines sounds improbable, though. The AO16 produced about 8,000bhp, which would imply 64,000bhp installed. Considering that the comparable USN ships had a 20,000shp steam turbine plant, this is wildly excessive. Given two equal-sized engine rooms, I'd suggest a plant of either two or four engines more likely: the four-engine configuration is probably still overpowered, but this might make sense if the main machinery was also expected to supply electrical power for ships services. Two engines would likely provide sufficient propulsion power - the slightly smaller ADAMANT only had 8,000shp steam turbines - but I'd expect to see just one engine room in that case. The only way I can see eight engines making sense is if two ships were planned with four engines each, but I'd expect to see mention of a second ship if that were the case.

Incidentally, the reliability issues with the AO16 do not bode well for the various diesel-powered frigate and corvette proposals of the mid-1960s planned around that engine.

Lore, not for the first time, has perhaps misremembered actual history. The Rover class initially used a pair of 8,000hp AO16s (V16s) for 16,000hp in each each ship. The submarine tender was to use eight AO6s (inline 6 cylinder) of 3000hp for 24,000 hp. Engines from the same family but not the same engines.

There is a note in the relevant file stating an expectation that the AO series could be uprated to 625hp per cylinder in the future. Initially though, Director Marine Engineering (DME) had recommended that each engine be downrated to 2,400hp in total. There was only a single shaft and the maximum power design point was to be 16,000shp, the rest of the available power being used for services etc.
 
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RLBH

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Lore, not for the first time, has perhaps misremembered actual history.
A point which we should all be very aware of, especially when trying to make sense of oral history. It's very easy to accept the word of old hands as gospel since they were there - but often they weren't there, and even if they were memories can easily be distorted. One common form of this (not the case here though!) is for 'or' to become 'and' in lists of equipment.

Eight AO6s and 16,000shp makes perfect sense; means in turn that the ROVER class engines were only incidentally linked - they can't have been the same engines, and were presumably a bigger order so wouldnt make sense as 'compensation' for a lost order. But if the AO series was seen as the Next Big Thing it makes sense that they should have been preferred for a lot of projects.
 

Thorvic

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The design of the ship was complete at the point of cancellation. According to lore the engines (Ruston diesels) had been ordered and were ultimately used in the first three Rover class oilers instead, in which they proved so troublesome they subsequently had to be replaced.

Is there a plan view and/or dimensions as this would make for an interesting build as a cancelled project, I'm guessing the size and look would be similar to the Fort Austin class RFA ships. Of interest is that it shows the Chinook but there appears to be no Hanger
 

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For the benefit of anyone who hasn't twigged yet - the drawing is titled S/M Depot Ship A.S. 01 - the ship being designated 'AS' in the USN-style system the RN started using internally from the mid-1950s.

More interestingly, I was looking up the FFWP commando carrier in Hobbs's British Aircraft Carriers. He observes that the ship was to be based on a proposed submarine depot ship to be built to Lloyds Rules. The commando carrier was to have a displacement of 20,000 tons and have a 25,000shp steam plant for 20 knots. I find it curious that steam was proposed given that the basis ship was diesel-powered, and the FFWP made extensive use of diesel engines in other ships.

Logically, the submarine depot ship in question must have been that under discussion here. That further supports a displacement of about 20,000 tons, and suggests a speed of about 17 knots - not that that's terribly important for a depot ship!
 

RLBH

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One thing that's very evident is that maintaining a Polaris capability east of Suez would be exclusive with maintaining that capability in home waters, given a fleet of four or five submarines. It does occur to me that the nine-boat force considered - and dismissed - very early in the programme (discussed in The Silent Deep) would be compatible with maintaining four boats each in the Atlantic and Indian Oceans, with the ninth boat under refit at Rosyth.

The missile freighters discussed in COS 11/66 Annex A as being conversions of existing ships would presumably be RFAs BACCHUS and HEBE, which were employed as cargo liners transporting naval stores between the UK and bases in the Mediterranean and east of Suez. Given their general configuration, the conversion would presumably see the loss of one of their three holds for general cargo.
 

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