In an attempt to reduce costs the CVF design will utilise the economic mix of commercial and military construction standards defined under new Lloyds Register Naval Ship Rules, an approach first used with HMS Ocean. By simultaneously minimising on-board weapons and C3I capabilities it was originally hoped (1997) that it would be possible for the CVF's to meet an initially budgeted building cost of £740 million each, this is not much more each in real terms than the £167 million that HMS Invincible cost in 1976. However by 1999 the MoD had accepted (e.g. memo dated 10 May 1999) the conclusions of preliminary industry studies that indicated a building cost "of around £2 billion" for both was more realistic. Other official comments at the time of SDR indicated a CVF Project budget of £2.2 billion. In May 2000 the Defence Procurement Agency said that the lifetime cost of the two new aircraft carriers will be about £5.5bn, given the expected forty year service life this implies an annual running cost (including refits) of just £44 million per ship - considerably less than an Invincible at £60-70 million. In early 2001 it was officially stated that the cost of the CVF programme was now estimated at a minimum of £2.3 billion and a maximum of £2.9 billion - the former figure probably being for a STOVL solution and the later for a CTOL solution. In May 2001 the Defence Select Committee was told by the MoD that "We envisage a total acquisition cost for the two carriers of £2.7 billion at outturn prices (EP 2001), including combat system and initial support costs, but excluding the aircraft. The peak years of expenditure are likely to be between 2008 and 2012."
In November 2001 the National Accounting Office stated in its Major Projects Report 2001 that the CVF Demonstration and Manufacture Phase would cost £3,047 million, with a 90% range of £2,654 m to £3,363 m. It also stated that the CVF Assessment Phase would cost £105 million, but this was determined before the announcement of the revised procurement strategy and the Phase costs have increased slightly.
Selection of the adaptable carrier design has added about £150 million to the costs.
After examining propulsion and power engineering
architectures, an integrated full-electric propulsion (IFEP) package
with gas turbines and diesels as prime movers, similar to that planned
for the DARING class will be offered by both consortia. The leading
contender will be the inter-cooled, recuperated Northrop Grumman/Rolls
Royce WR21 gas turbine which recycles hot exhaust gases both to reduce
the IR signature and to provide fairly uniform fuel consumption at high
or low power. Alternatives are the General Electric LM 2500+ and the
Rolls Royce marinaded TRENT. The gas turbine's and diesel engines will
power alternators fencing propulsion electric motors, offering the
potential to replace the conventional propeller shafts with two or four
podded propulsors with significant savings in space. Indeed, the Thales
team has formally indicated the choice of a podded drive propulsion
configuration. while BAE Systems plans a hybrid solution with a central
shaft and two podded drives.
The Thales consortium quickly committed to IFEP for CVF and they have brought Alstom on board as part of their team to provide expertise in electric propulsion and power distribution, bringing to bear their experience on Type 45 destroyers and elsewhere. Thales' note that the adoption of an IFEP system allows the ship's electrical generators to be dispersed throughout the vessel giving improved survivability. IFEP also opens the way to using podded drive propulsors ("pods"), a technology now common in modern cruise ships such as Queen Mary 2.
In conventional systems, electric motors are located
inside the ship's hull. With the new system, the motors are installed in
pods fastened to the hull, which eliminates long shaft-lines. Each
pod includes a propeller. The pods can rotate a full 360°, so they do
not only propel the ship - they handle manoeuvring as well. A ship can
have two or more pods.
Jointly developed by Alstom and Rolls-Royce, the popular Mermaid pod unit is a hydrodynamically optimised body, housing an electric motor, providing 360° azimuthing propulsion. The QM2 will have four 21.5MW pods (two fixed, two azimuthing) totalling 85MW, the Mermaid can be designed to reach up to 30MW, although 25MW is currently the top of the range.
"Pods are a proven commercial solution and they offer us a lot of advantages, notably manoeuvrability and the flexibility they bring to the shipbuilding programme," says Thales' Robertson. "But there are some outstanding shock and signature issues." BAE Systems takes a similar view. "We are looking closely at podded propulsion because it holds a number of attractions," explains chief engineer Scott Whiteford. "But it is a technology not yet proven for the military environment. One option we are considering is a hybrid arrangement with a conventional centre shaftline and two podded drives."
The CVF's will be by far the largest gas turbine prime mover driven warships in the world. Since the late 1990's it has been expected that the core of the IFEP system will probably be four Rolls Royce/Northrop Grumman WR-21 intercooled and recuperated (ICR) gas turbine generator units, although alternatives have always been considered including the 25MW General Electric LM2500+ gas turbine (preferred by the French) and diesels.
Recently, with the growth of the size of the CVF design, the new Rolls-Royce Marine Trent MT30 has become increasingly favoured over the WR-21 because it is significantly more powerful (36MW compared with 25MW), thus less GTA units are required for achieving the required power.
The optimum location for the position of the main propulsion system is being examined, with the need to maximize the hangar space below decks a major consideration. The gas turbine generator units could be mounted in the superstructure, this would require a large island and reduce the flight deck area, but by avoiding volumous air intake/venting trunking to low machinery spaces will enable a larger and wider hanger. The comparative advantages of the two layouts has been extensively debated within the DPA and the two competing industrial teams, it now seems that operational analysis and aviation generation studies have demonstrated that the extra flight deck space associated with a small island will be more valuable than the extra hanger space, so a traditional main hull located engine room now seems most probable.
Battery's and several large diesel generators will provide emergency power if the prime movers fail for any reason.
The maximum designed speed for CVF will be at least 25 knots.
It is expected that unlike the Invincible's, CVF will be fitted with Jet Blast Deflectors (JBD's). These are necessary because of the very high and potentially dangerous and destructive thrust that the F-135 engine in the JSF generates when running at maximum thrust for launch. It is hoped that with modern materials it will be possible to avoid the cost and complexity of having to use sea water to cool these - the expected use or otherwise of afterburners during launch will be a big factor in this decision.
The adopted CVF STOVL designs will probably have two JBD positions on the STO launch run, at perhaps 120 and 180 m from the bow. The former is for lightly loaded aircraft (e.g. configured for air-to-air warfare), while the later position enables a heavily loaded STOVL JSF to launch at it maximum take-off weight (MTOW) given reasonable (30kts?) actual wind over deck (WOD). Also, both positions could be used by lightly loaded aircraft to allow very rapid launch events.
Neither team is in any doubt over the importance of the ship/air interface. "The carrier air group is the CVF primary weapon system, and CVF exists to deliver offensive air capability," says Peter Fish, an ex-RN aviator and head of aviation systems and interface for BAE Systems' CVF team. "The carrier is, therefore, critical to making sure we return the investment in FJCA."
The rival contractors have each built up specialist aviation teams, drawing on US, UK and French experience, to optimise the interface between the carrier and its air group. Sortie generation is the all-important metric: the URD aspires to a peak of 130 sorties per day, revised downward from an original target of 150.
The complex process of aircraft handling, movement, preparation, launch and recovery has been the subject of extensive analysis and modelling, bearing in mind that CVF should be able to simultaneously launch and recover aircraft, concurrent with fixed- and rotary-wing operations. In turn, these analyses of aircraft cycling have influenced flight deck operating and parking areas, island footprint, hangar layout, aircraft and weapon lifts, and siting of support services.
BAE Systems and Thales have each developed sortie-generation models respectively known as SURGE and SAILOR. In turn, the DPA has its own model known as CAPSTAN.
Work has also been carried out to map the heat and acoustic footprints on deck. Noise is a major issue, as health and safety considerations are likely to restrict the allowable tolerance to high levels of acoustic energy.
Both teams are embracing so-called 'pit-stop' servicing in a bid to reduce aircraft turnaround time. Thales' aviation systems team leader Gene Tucker, a former USN carrier aviator, explains: "What we envisage is one-stop servicing stations on the edge of the flight deck to minimise aircraft turnaround time and cut the number of personnel on deck. These service stations will prove for refuelling, re-arming, quick maintenance, and an interface into the ship's IT infrastructure."
The flight-deck island arrangement, however, is one area where the rival teams have departed in their approaches. In an effort to maximise flight-deck area, and taking into account uptake/downtake constraints, Thales adopted a radical two-island design for both the STOVL and CV carrier variants on the grounds it minimises island footprint on the deck. According to Peter Robertson, "positioning the flying control centre on the aft island improves operational control and flight-deck safety." He adds that wind-tunnel testing and CFD analyses of the twin-island configuration has dispelled concerns over airflow anomalies. Thales has also adopted a novel extended centre line runway option, that will be used on occasions when it is necessary for JSF to carry increased payloads.
The two teams have also taken differing approaches to aircraft lifts. While both have adopted deck-edge elevators, the Thales design features two large lifts each able to accommodate two FJCA-size aircraft. BAE Systems, on the other hand, has equipped its designs with three lifts, each sized for one aircraft.. Its STOVL carrier featured a single island and aft 'mack', but the adopted CV design joins together these two structures to surmount one of three deck-edge aircraft lifts, one of which emerges in the middle of the island. "We are considering the use of composite structures in the 'arch' that will sit above the lift," says BAE's Peter Fish. "This would provide additional estate for the numerous antenna elements that must be accommodated topside."
Fish says that CVF and JSF offer the chance to improve STOVL operation significantly over today's Sea Harrier FA.2/Harrier GR.7A. Options for the vertical landing element include approaching over the ships stern rather than coming alongside and manoeuvering over the landing spot. This offers an improved landing rate and addresses environmental issues - such as the jet exhaust down blast associated with landing on. The F-35's improved STOVL handling and control will be a factor n allowing this, while the aircrafts electro-optical sensors offer opportunities to present the pilot with improved cueing.
Another feature of the BAE Systems CVF design that Fish points out is the highly flared hullform. "Traditionally, carriers have had vertical sides with box-shaped sponsons attached, but this generates both signature and internal layout problems. The flared hullform we have adopted offers much better use of internal volume, and also lowers radar cross-section."
The ship will be fitted with a large hanger deck, able to accommodate about 30 aircraft depending on type. The hanger deck will be high enough to ensure that any aircraft embarked can be maintained anywhere, eliminating the need to move airframes around during maintenance.
If the carriers are ever converted to a CTOL configuration is adopted for CVF this will the addition of a catapult launching system. One of the central engineering and design problems posed to the rival CVF design teams is how best to power and integrate such aircraft catapults.
Steam catapults, in the form of the C13-2 system employed in all the US Navy's carriers, represent a proven baseline solution. But requirements for high volumes of steam and water present problems for a non-nuclear carrier like CVF, and there is a strong disinclination towards steam within the RN given its through-life cost implications. And a problem facing designers is that the traditional steam catapult is not compatible with the IFEP system planned for the CVF. A separate and expensive auxiliary steam plant with considerable output therefore would be required.
The answer could lie in the maturation of the electromagnetic catapult (EMCAT), a technology today on the cusp of being transitioned from the physics lab to an engineering reality. If the concept can be realised, EMCAT offers the prospect of significant life-cycle cost benefits (in terms of reduced maintenance and crew workload) and would also offer benefits for aircraft operations and flight-deck operability. EMCAT's should increase launch performance and make significant reductions in installed weight, volume, and manning workload requirements. Initial studies by DERA and the USN indicate that a 90MW 300ft long linear motor EMCAT able to accelerate every 45 seconds a 100,000 lb. airplane to over 130 knots, or a lighter aircraft (such as UAV's) to 200 knots, would seem to be viable.
Across the Atlantic, the USN is now planning for an Electromagnetic Aircraft Launch System (EMALS) to enter service aboard the projected CVNX-1, due in service in 2013, a comparable timeframe to CVF. The EMALS system will use a 300ft-plus-long linear electric motor to accelerate aircraft over the flight deck, employing rotational energy storage alternators to supply high-frequency power to the linear motor through a PWM inverter. The linear motor takes the average power from the inverter and releases it in a short pulse, which accelerates the aircraft for launch.
Under parallel programme-definition and risk-reduction
contracts awarded in December 1999, teams led by General Atomics and
Northrop Grumman are each developing and building full-scale,
reduced-length prototype systems. Following hardware demonstrations, one
contractor will be downselected to pursue system design and development,
and subsequently production for CVNX-1.
The initial phase of work covers building a static test
rig to measure the performance of a linear induction motor design.
Further development of EMCAT depends on the DPA taking up additional
staged contract options: a contract clause also enables the novation of
EMCAT technology to the CVF prime contractor in due course.
"Steam exists, and the C13-2 catapult is the launch system against which the JSF CV variant is being built," said a senior member of the BAE Systems ship/air interface team. "Its performance characteristics are going to be matched around that technology."
What both teams have proposed is that the CVF should be built to accommodate a potential EMCAT/EMALS backfit. That would incur some additional cost at build, but would help 'future proof' the carrier design to accommodate new aircraft and air vehicles through life.
Some early BAE graphics appeared to show radars and VLS silo's for the Eurosam SAAM or PAAMS air defence missile system But this has apparently been dropped, presumably on cost grounds.
The rival teams acknowledge the importance the MOD attaches to ship availability and through-life support. The MoD wants at least a six-year interval between dockings, and a maximum upkeep period of no more than six months. BAE and Thales are required to guarantee the continuous availability of at least one ship, and a total availability including both ships of 584 ship days a year! This is demanding new and innovative approaches to warship maintenance and support.
Traditionally the life of major warships is punctuated by infrequent (perhaps every 5 years) but major refits, which last 18-24 months. But this approach would sometimes mean a whole year with just one ship available, and obviously the 585 ship/day requirement could not then be met. Also, with just two ships there is a risk of the situation developing where one carrier is deep in a major refit while the other becomes non-operational for some reason (e.g. a major fire or mechanical failure), causing a prolonged capability gap with no CVF available.
Therefore in order to ensure that one CVF is always operational, or can quickly be made so, BAE and Thales are proposing that their ships will have more frequent but shorter refits lasting not more than 6 months.
In order to allow major work to be carried during such a short refit period, the ships are highly modularised. Repairs and upgrades will be done by replacement, even the big WR-21 gas turbines will have access routes to allow their removal and replacement within a few days work
Proposed Anglo-French Carrier Force
However after some initial interest and positive comments from the Defence Secretary, Mr Geoffrey Hoon, UK thinking seems to have quickly cooled towards the proposal. On 2 March 2001 when asked by the Select Committee on Defence: "How is the Anglo-French carrier force coming along?" Admiral Sir Michael Boyce replied "I am not aware of any Anglo-French carrier force." And in response to questions he was also posed on 28 March 2001 by the Select Committee on Defence about the French statements, the Anglo-French Carrier Force and a possible Anglo-French carrier, the Defence Secretary said: "There are discussions under way between us and France about co-operation as far as our carriers are concerned but there are no formal proposals that I am aware of to develop a joint force along the lines that your question might suggest. ... . I suspect that the quotation that you have cited rather overstates the degree of development that has so far been achieved. ... I am not aware of any plans for there to be developed a joint aircraft carrier. I am sure that there have been from time to time conversations and discussions about that and it is clearly in the fullness of time a possible option, but it is not something that we are working on as of today."
Despite the depressing UK response, in early 2002 French Navy Chief of Staff Admiral Jean-Louis Battet again noted that European cooperation (with the UK in particular) would go some way to resolving the limitation of only one French aircraft carrier ... provided that the Royal Navy opts for the CTOL (actually CV) variant of the F-35 for its two future CVF's, which will be in the same 40,000t class as the Charles-de-Gaulle. If they do, says Battet: "it could be conceivable to add a third ship to the series for the French Navy." Such a solution, he underlines, would be considerably less expensive than the Charles-de-Gaulle (which cost €3 billion) and would make sense since "the overall European requirement for ships in this class is estimated at 4-5".
The main problem in the period up to mid-2002 was that the scope for collaboration on a joint design was very limited given the difference in the two nations requirements. Many aspects of CdeG and her proposed companion are CTOL-related, while the United Kingdom has inclined to opt for the STOVL version of the Joint Strike Fighter for its JCA requirement. However by also deciding on 30 September 2002 to opt for STOVL'ised CTOL carrier design for CVF, the UK suddenly opened the possibility of collaboration - if the UK is willing to accept the associated delays.
In early July 2002 the French Ministry of Defense was reported as having formally approached its British counterpart as regards possible collaboration on the CVF project to build future aircraft carriers for both navies (2 carriers for the UK and 1 for France), however senior UK officials quickly played down press speculation that the UK would join a collaborative carrier programme with France. For example, Admiral Sir Alan West, Commander-in-Chief Fleet, told Janes Defence Weekly in July 2002: "We do talk to the French but we don't want a collaborative programme that ties you in. .... We want to co-operate [with the French], it could be very attractive to order three sets of engines and other [major components] and there could be a lot of benefit from co-operation. We do not envisage a big programme with the French - all it would do is slow things down."
While a joint Anglo-French carrier project may be politically attractive to the UK, clearly some elements within the MOD and RN feel that it may be have become too late to incorporate French requirements in to the existing CVF project without incurring unacceptable delays and cost increases. It is also far from certain that the French will be willing to genuinely open up their new carrier project to overseas companies such as BAE Systems in the same way that the UK has opened up CVF. However, the march towards just such as joint projects suddenly seems to be accelerating....
After over a decade of delays, on 11 September 2002 a French Cabinet Meeting chaired by President Jacques Chirac finally approved plans for a second aircraft carrier - equivalent to Initial Gate. A decision on the hull type, nuclear or conventionally propulsion and overall capability package will be taken in June 2002, it will be ordered in 2005 and is expected to be be operational by 2015. Asked about possible construction of the new carrier with Britain, the Defence Ministry's Bureau said: "This is a dossier that is clearly on the agenda for French-British cooperation.". He added that Defence Minister Michele Alliot-Marie and her British counterpart Geoff Hoon reviewed the issue recently, but did not make any decisions. On 13 September French Defence Minister Michele Alliot-Marie said on Europe 1 radio "We would certainly welcome collaboration (with Britain). We need to know whether the British will choose vertical take-off aircraft - which would mean a short runway - or more classic models such as ours."
On the 2 October 2002, the British Ministry of Defence said that the potential for greater collaboration with France had been acknowledged, and the following day a spokesman for the French defence ministry, Jean-Francois Rivasseau, said that cooperation between Britain and France in the aircraft carrier construction projects underway in each country was "totally on the table" ... and that Britain's decision to build two "adaptable" aircraft carriers to go into service in 2012 and 2015 meant that they could be altered to handle both French and British warplanes.
Press reports of high level government meetings held in October 2002 to discuss the proposed Anglo-French carrier indicated that Thales Naval had been become the strong favourite to win the UK's early 2003 CVF down-selection decision, it being accept as inconceivable that France could accept a British company as prime contractor for its new carrier. Work share and management issues are likely to come quickly to the fore, the French demanding more than their 33% share of the funding would suggest, but the British are unlikely to concede to the French the leading role that they feel their experience with CdeG entitles them to. Also the French are unlikely to happy with the relatively risky assembly plan being proposed by the UK, and the suggestion that all 3 hulls are built in France is likely to be back on the table.
Probably neither Navy would be over disappointed if efforts to agree on a joint Anglo-French carrier project fail. A common collaborative Anglo-French carrier project would be very attractive politically, and should theoretically be cheaper to each partner than a purely national design. However, recent Anglo-French collaborative defence projects (e.g. the Horizon CNGF) have been notably unsuccessful, with timescales slipping many years (5-10) and costs soaring (40-100% above the cost of a purely national project according to a NAO report published in 2001). Subsequent British parliamentary "post-mortems" have concluded that the problems were largely due to French insistence on un-equitable and unworkable management and industrial structures, while simultaneously the systems specification became ever less suited to UK needs. It's difficult to believe that a French dominated joint carrier project would have more favourable results for the UK. Certainly French officials at the DGA have already made no secret of the fact that they believe they should have the leading role in any joint Anglo-French carrier project because of their more recent experience with CdeG, and apparently the design being proposed by the French to the British as the basis for joint construction is a slightly lengthened variant of Charles de Gaulle, but with electric propulsion rather than nuclear propulsion.
Note: Links open in new windows
Future Aircraft Carriers (a website sponsored by BAE Systems)
Article in the RAF magazine Air Power [Adobe PDF format] - "To Sea or Not to Sea?"
Last revised: 17 January,
© 2004-13 Richard Beedall unless otherwise indicated.