Wednesday, February 10, 2010

EXCLUSIVE: Naval Design Head's Paper On Aircraft Carrier

Cmde AK Khetan, Principle Director at the Department of Naval Design, has been closely associated with the Indiangenous Aircraft Carrier programme and was the project director during the crucial phase of design finalisation, equipment ordering and the contract signing with Cochin Shipyards for its construction. The following is the paper he presented earlier today at the National Maritime Foundation seminar on Aircraft Carriers in the 21st Century:

1.1 Aircraft Carrier is considered to be the most versatile ship combining the role of a sophisticated warship with that of fighter aircraft. The first function of a carrier is obviously to deploy aircraft far from the home land. Depending on the country’s goal and maritime objectives, this deployment may be required under severe weather conditions, worldwide far from the home land, in peace as well as in war, and as promptly as possible.

1.2 The carrier is used for different missions, i.e. launched strikes against military and economic targets, naval and surface warfare, pre-strategic nuclear strikes against land and naval targets, protection of sea lanes and humanitarian aids. Aircraft carriers are also recognized show of country’s might for exercising influence on foreign policy.

1.3 These ships are indeed the pinnacle of design complexity and engineering marvel involving practically all facets of technology. Accordingly, these are also the costliest ships requiring versatile infrastructure for its construction, upkeep, maintenance and operation. Therefore, realization of an aircraft carrier necessitates strong technological base and huge financial commitments. It is because of this that only very few leading nations of the world operate aircraft carriers range of which is extensive from a 13,800 tonne STOVL Italian Garibaldi to an 1,05,000 tonneCTOL US Navy CVAN.

1.4 India is one of the few nations operating an aircraft carrier STOVL Viraat, ex Hermes. 45,000 tonne STOBAR Vikramaditya, erstwhile Gorshkov, presently being refurbished at Russian shipyard Sevmash is likely to join the Indian Navy in 2012. 40,000 tonne STOBAR Indigenous Aircraft Carrier, designed in house by Navy’s own design organization and being built at Cochin Shipyard, is scheduled to join the Indian Navy by end 2014.

2.1 Economical, Industrial and regulatory constraints combined with mission requirements define the aircraft carrier size, type, number and aircraft mix to be operated from it. Cost, as for many projects, remains to be a major driver.

2.2 Aircraft Carrier is not intended to operate alone, along with the aircraft carrier comes a number of aircraft and helicopters, different types of warships ranging from cruiser to frigate, submarines and a varieties of support vessels. The combination of which depends on the mission of a Carrier Strike Group (CSG). The cost of acquisition therefore is much more than that of an aircraft carrier alone. This demand gets further increased if cost of running, support, upkeep and maintenance facilities for the aircraft carrier and aircraft are included.

2.3 It is because of the above, that even while recognizing the strategic necessity of aircraft carrier for its usefulness and forward basing, there exists strong debate in favourof shrinking its number and size world over to contain spending. The reasoning has also been supported by technological advancements in avionics, extended ranges of operation by the aircraft view in flight fuelling and better intelligence gathering.

2.4 If recent publications are to be believed, even Pentagon is considering a proposal to decrease the number of aircraft carriers from today’s 11 to 8 or 9 in order to save on much more than USD 47 billion over 30 years considering savings from the non-procurement of associated supply ships, carrier air wings and operation cost etc.

2.5 UK Govt. in spite of contemplating to replace their old small carriers since a decade by medium sized two in number 60,000-65,000 tonne aircraft carriers under CVF programme, have finally decided to go ahead with only one Queen Elizabeth to be in service in 2016. The second proposed carrier is expected to be converted to an amphibious commando ship with helicopters on board in lieu of JSF aircraft.

2.6 The French Govt. inspite of contemplating to have an additional medium sized carrier and accordingly participating in CVF programmehave finally pulled out considering enormous cost of acquisition. Other nations such as Russia, Brazil, Italy and Spain have no known plans to add to their aircraft carrier numbers.

3.1 In an aircraft carrier, the complex interface between the ship and the fixed wing aircraft it operates drives both the design of the aircraft carrier and the operating aircraft. All present and future aircraft carrier programmesare focused around operation of fixed wing aircraft, as it encapsulates most of the attributes of sea based airpower.

3.2 A CTOL (Conventional Takeoff and Landing) carrier requires an angled deck to maximize separation between aircraft launch and recovery operations, high speed to generate additional wind across the flight deck, fresh water and steam generation facilities for catapult system. This arrangement facilitates simultaneous launch, recovery and high sortie generation but requires a plant to generate steam, achievable more conveniently for a ship with steam or nuclear propulsion.

3.3 Similarly, a STOBAR (Short Takeoff ButArrested Recovery) carrier requires a ski jump for short takeoff, a separated angled deck for arrested recovery and high speed to generate additional wind across the flight deck. STOBAR however has limitations, as the requirement of an angled deck recovery and a long takeoff run, make flight deck space demands that can only be satisfied by pretty restrictive cyclical flight operations. This however permits greater flexibility in the choice of propulsion system, i.e. steam, gas turbine, electrical or nuclear.

3.4 STOVL (Short Takeoff and Vertical Landing) concept was found with the invent of Navy Sea Harrier FRS MK51. This concept though very cost affective for small carriers, has severe limitation of aircraft AUW and range.

4.1.1 The aviation aspects that dominate flight deck configuration are aircraft type and number, sortie generation rate and formation requirements. This would decide launch, recovery, supporting equipment, parking, number and size of aircraft lifts and thus to an extent the sizing of the carrier. The related parameters influencing the sizing of the flight deck, the ship and its cost are as follows: -

Number and lengths of catapults in case of CTOL carrier. Length and width of takeoff runway and extent of ski jump in case of STOBAR carrier. The area occupied by ski jump cannot be utilized for parking and the raise of ski jump vis-à-vis flight deck level would require higher clearance for the aircraft while bolteringthus higher angle for the angled deck.

Length and width of recovery area depending on the aircraft and arrestor wire systems (3 or 4 wire).

Parking area including refueling/ servicing and rearming areas.

Primary operation aspects (Sortie generation rate/ simultaneous launch and recovery/ maintenance of combat air patrol/ multi role operations – CAP/ ASW Helos/ AEW). Number of sorties, formation type and aircraft operating range would decide quantity of aviation fuel to be carried and thus tankage and size of the ship.

Aircraft lift’s number, size and capacity.

Requirement to recover the aircraft on flight deck in case of arrester hook failure would entail providing crash barrier, therefore, increasing the length of the runway and flight deck. In larger carriers, the length of the landing runway invariably is adequate for accommodating the crash barrier. However, for smaller carriers this would imply increase in length, and thus added costs. A thorough cost and safety benefit analysis is a must while finalising such requirements as this can be met by alternative means such as recovering the aircraft on land, if required by refuelling in air.

4.1.2 An optimisation and rationalisation of above aspects has a significant bearing on the carrier sizing and cost. Therefore, many of the features though desirable need to be rationalised for operational requirements vis-a-vis cost effectiveness.

4.2 Choice of Sustained Top Speed, Endurance and Flexibility in Choice of the Propulsion Plant.

A fundamental driver in the choice of propulsion plant is a requirement for sustained top speed. Choice of very high sustained top speed in the name of aircraft operations, would restrict the choice of type of propulsion in medium and large carriers. The speed of the vessel has a direct bearing on the powering requirements and increment of every additional ‘knot’ increases powering requirements exponentially. Using thumb rule analysis, for a 65,000t carrier, the powering requirements can be brought down from 145 MW to 85 MW, i.e. by 40%, for a sustained top speed reduction from 30 to 25 knots. Reduced power would lead to reduced size and weight of propulsion plant, shafting, associated auxiliaries, uptakes and intakes. Thereby alternative options for choice of propulsion system based on economy and size of the ship.

Similarly, endurance requirement of ship and specific fuel consumption rate of engine would directly influence fuel tankage requirements, thereby size and cost.

In case of CATOBAR carrier, in addition to sustained top speed, requirement of steam also becomes a governing factor for choice of propulsion plant. The steam propulsion plant therefore becomes preferred choice. The choice between conventional and Nuclear plants for generating this steam, is primarily strategic associated with industrial base and regulatory position.

The choice of nuclear reactors as prime movers has many consequences on the design of the carrier: -

Nuclear plants are bulky with associated secondary machinery and shielding and therefore extremely difficult to accommodate.

It has less impact than fossil-fuelled prime movers on the hangar and flight deck configuration, with no need for large intakes and uptakes. However, the relatively infrequent reactor core refuelling demands can still compromise the carrier layout above the reactor plant.

Nuclear powered carriers though have no requirement for propulsion fuel tanks but this does not diminish the dependency of the carrier for afloat support to maintain the bunkerage of aviation fuel and the replenishment of stores for the large complement of people and aircraft.

In case of STOBAR carriers, other propulsion options are feasible due to no requirement of steam. Indian programme IAC with GT propulsion, Vikramaditya and Russian Kuznetsovwith steam propulsion are carriers falling in this category.

Therefore, rationalisation of top speed can have a significant impact on the choice of propulsion system commensurate to the requirement of aircraft operation, design (simpler layouts and simpler propulsion trains) and therefore, major impact on the ship acquisition and sustaining costs. Rationalisation of endurance would permit designer to have reduced fuel tankageand ship size.

4.3.1 The single, biggest decision to govern the size of the hangarage and associated workshop facility is the proportion of the aircraft complement to be accommodated in the hangar, varieties of aircraft and the extent of maintenance envisaged onboard. Specific aircraft and requirement of precision in its maintenance would also affect these aspects.

Significant space, usually located forward and possibly outboard of the hangar, is the mass of workshops and stowage areas. These are of a very high standard given the sophistication of modern aircraft, their avionics and include diagnostics, repair testing and tuning of airframe, engines, air systems and avionics for several aircraft types and, to a degree, the weapons they carry. In addition there is a multiplicity of aircraft and weapon handling/ testing trolleys and the duplication of many of the services in the flight deck walkways. Therefore, the level of onboard maintenance perceived for aircraft needs to be rationalized with care in order to bring down the demand for these spaces and inventory of equipment / trolleys fitted therein. There is little advantage accrued in penalizing the ship sizing by catering for routines whose probability of occurrence is low and can be deferred for attending easily ashore.

4.4.1 Aircraft carrier generally for its missions sails with its group consisting of air wing, guided missiles cruisers, guided missile destroyers, attack submarines, frigates, other smaller ships and support vessels. Therefore, providing multi role military capability in the name of self defence needs to be examined rationally by Naval Staff as this has significant bearing on the complexity of architecture and sizing of aircraft carrier and resultant cost. The aircraft carrier therefore needs to be rationalised for provisioning of weapon and sensors commensurate to its role for aircraft operations and self defence considered as bare necessity.

4.5.1 The decision for equipment specification to comply military standards (mainly high shock, vibration and Ingress protection Rating compliances) or commercial,needs to be rationally weighed with due diligence based on VED (Vital, Essential and Desirable) analysis for its functioning and combat requirement onboard ship. The COTS equipment have the obvious advantages of being cheaper, ready availability, clear dimensional definitions, and easier to maintain etc. This in turn reduces Yard effort immensely and also reduces time of procurement and therefore accrues major cost savings. On the other hand equipment to military standards considered highly reliable in war scenario are required to be specifically developed/manufactured,as the size and capacity required for the carrier are unique. Military standard equipment due to requirement of shock and low vibration requirements at times cost 4 to 5 times that of commercial standard equipment of the same capacity. Requirement of low radiant noise leads to double mounting arrangements resulting in increasedsize of equipment and thereby compartment congestion. Availability of very few equipment manufacturers capable of meeting these requirements and need for long deliberations to make them understand the same,invariably leads to long procurement time and high cost.

As aircraft carriers are expected to operate for a period exceeding 30-40 years, life cycle cost for equipment upkeep and maintenance becomes vital in reducing the budget cost. Equipment to commercial standards may obviate storage of large inventory of spares, as the same would be readily available in the market, alternatively it would be feasible to change the equipment itself easily as with time there is improvement in technology and these equipment are becoming compact and more power effective. On the other hand equipment to military standard, as specifically developed, would require blocking of large investments in procurement, storage and preservation of large inventory of spares, thereby extra financial burden on the project.

4.6 Use of Matured Technology vis-a-vis Development Items. Choice of an existing proven equipment and matured technology ensures availability of binding data for detailed design andthe item itself in time. On the other hand, equipment under development in the name of improved performance and technology leads to time and cost over runs. The imponderables associated with such development are non availability of realistic binding data leading to non finalisation of detailed design, rework to accommodate the final parameters and non availability of the equipment itself in time delays the project, the financial impact of which is much higher than the cost of equipment. It is, therefore, necessary that to the extent feasible use of only matured technology be envisaged and developmental items be considered only if it weighs heavily in favour of operational or strategic requirements.

4.7.1 Survivability has always been a major design consideration for the aircraft carrier being highly expensive and carrier of high value aircraft. Further, the carrier is one of a few major assets which politically “cannot be lost" to keep the moral of the country high especially during wars. However, without compromising on survivability, considerable economy of cost can be achieved if a rational approach is adopted by providing higher protection and redundancy only forvital areas of the ship, i.e. main machinery compartments, magazines etc.

4.7.2 In the name of safety and redundancy, an overkill approach for equipment and system is considered for vital systems. It is pertinent to mention that the additional equipment and systems in the form of reserve also necessitate associated auxiliaries and systems. Over capacity of the equipment leads to their under utilisation and at times uneconomical operation. A simple example in case of warships is providing reserve to the extent of 100% of DG sets for power generation and meeting full requirement of action load without use of reserve. This leads to undue higher capacity and number of DG sets cluttering the premium machinery space of the ship. On the other hand rational estimates of action load and reserve would bring down the capacity and number of DG sets making the machinery space more user friendly.

Though the safety and redundancy is important, due diligence would be necessary for rationalising the reserve. This would lead to de-clutter the ship, save on internal volume; reduce the ship size, Capital expenditure and costs. Use of reserve can be severely curtailed, if reliable technology/equipment and systems are used.

4.8 Addressing Monopoly in Aviation Equipment. There are number of critical aviation equipment that have specific interface requirements with the aircraft. Therefore, the aircraft dictates the choice of the equipment. Arresting gear, hydraulic chocks, online aircraft engine diagnostic equipment are specific examples to this. The sourcing of such critical and cost intensive equipment becomes restrictive and monopolistic in the hands of equipment OEM. Refusal to provide theseequipment in time by these OEMs can derail the project. In order to obviate such situation, it is best that the carrier or land based equipment that are aircraft specific, be negotiated with the aircraft acquisition. This can accrue benefits of competitive bidding and will go a long way in controlling aircraft carrier costs.

4.9 Cost Surveillance. Our experience shows that in a warship more than 60% of the cost is for procurement of material, equipment and systems. Therefore, in order to build an aircraft carrier within budget, cost optimisation of these items is must. Basing our choice therefore is not to be only on technology need, but with a joint evaluation of technology and cost, each being given due weightage. Requirement of high end/ latest technology can be dispensed in favour of a technology meeting the functional need if comes at a much lower cost. Cost surveillance of requiredmaterial, equipment and systems over wide range of spectrum within the country and abroad would facilitate acquisition at economy.

4.10 Outsourcing/Collaborative Approach. Use of outsourcing / collaborative approach is utilised to improve quality and meet time lines so as to make the project cost effective. In this strength areas of the other organisations are identified and contracted for outsourcing / collaboration. This would optimise investment and use of human resource. This however has its own pitfalls, view dependability and vested interest of partners/outsourced organisation when at cross roads.

4.11 Requirement of Infrastructure. Whilst assessing cost of an aircraft carrier, investment required for infrastructure augmentation for its lifecycle running, upkeep and maintenance also needs to be addressed. Therefore, the choice of equipment and system fit needs be governed with these considerations also, so as to be economically supportable. Aircraft Carrier being a warship, in house capability for such activities also need to be weighed for a war scenario or sanctions/ obstacles due to restrictive technological regimes.

4.12 Series Production and Construction Technology. Series production / ordering of more than one carrier at a time would greatly offset the costs of design, detailed engineering and development etc. This would also encourage shipyard to adopt integrated construction technology and optimum production methodology for various ship components, systems and economy of material consumption to ensure economy of cost and yard effort. Additionally, the experience/ expertise gained on the first ship can be implemented on follow on ships to make them better and more cost effective. This would also make equipment/systems production and procurement more cost effective. It is emphasised here that ship construction involves large pool of human resource, highly skilled and unskilled. Series production results isfamiliarity, understanding of drawings and work by this groups and therefore saving on time in execution.

Effective Planning. Adetailed fully mature plan for the project needs to be in place before its commencement. The critical activities affecting the project have to be provided with alternatives. The ordering of material/ equipment and their availability needs to be dovetailed with the overall schedule. If the equipment is received early, revenue is lost view blockage of investment and loss of interest, and additionally, money has to be spent in inventory management, handling, preservation and extension of warranty/guarantee validation. Alternatively, any delay in receipt of equipment can have a cascading affect on the follow on activities, thus offsetting time lines and increased costs. We must try to achieve the highly desirable ‘Just in Time’ principle to effectively control costs. This is key in achieving economy of cost.

Invention in Carrier Capable Aircraft. As the size of the carrier is directly related to interfacing requirement of aircraft operating from it, any major technological breakthrough in aircraft development leading to requirement of reduced runway for takeoff, landing, maintenance and operation onboard would definitely reduce the size and complexity of the carrier. An invention of vertical takeoff and landing capable sea harriers by UK had dispensed arrester wire and replaced catapult by ski jump. This reduced the carrier size, complexity and cost;making it affordable for smaller nations.

6. Empowerment of Decision Making. Decision making always remains the key for the successful execution of aproject according to the timelines within the budgeted cost. Therefore, the project team entrusted with responsibility of executing aircraft carrier programme involving large capital investments, dealing with various organisations and diverse technologies, needs to be entrusted to an empowered Project Team with authority to take expeditious administrative, financial and technical decisions as necessary in the interest of the project. The present set up of collective decision making, lacks accountability and priority, thus leading to time and cost over runs. The minor advantage accrued in individual systems / equipment in terms of cost due to lengthy deliberations would be easily over run due to its influence on project delaysand resultant cost escalation. Therefore, cost benefit decisions have to be based on holistic approach and not on individual equipment / component / system.

7. Human Resource. Human resource is back bone to the programme. A knowledgeable, well trained and motivated human resource can provide out of box solutions to complicated tasks, achieve high quality and significant savings in time and cost. Shortage of required man power may lead to short cuts, thus compromise on quality resulting in time and cost over runs. Therefore, it is necessary that whilst budgeting the project, cost implication of human resource is adequately factored in.

8.1. Aircraft carriers are the costliest ships requiring versatile infrastructure for its construction, upkeep, maintenance and operation. A major focus world over is to build these ships in limited budget. Time and cost over runs are common phenomena world over in warship building and so is the case for aircraft carriers. Time and cost over runs are expected even in USA’s latest CVN 78 carrier programme inspite of having vast experience in designing, building and operating aircraft carriers over five decades. The same is the case of CVF programmeof UK.

8.2. Rationalising requirement of Naval Staff, ship parameters, equipment specifications, safety and redundancy by use of reliable equipment/technology, would bring down the costs considerably. Increased use of COTS equipment and items for non vital requirements, matured technology in lieu of items under development would contain build period and economy of expenditure. Basing our choice for procurement is to be guided on joint evaluation of technology and cost, each being given due weightage.

8.3. Use of outsourcing/collaborative approach need to be adopted for areas wherein availability of technology and human resource is time and cost effective.

8.4. Series production in lieu of only one of type would encourage shipyards adopting integrated construction technology; development of optimum production methodology for various ships components, systems and economy of material consumption. This would also facilitate use of experience/expertise gained on the first ship for implementation on follow on, to make them better, faster and thus more cost of effective. Further, in this case increased volume would make the material, equipment and systems procurement more cost effective.

8.5. Investment in human resource for design, construction and management; effective detailed planning and delegation of decision making commensurate to the responsibility would lead to unhindered programmeexecution thus meeting the time lines within the limited budget. Inadequate efforts in these areas though not directly visible have cascading effects, resulting in time and cost over runs.

Photo by Shiv Aroor / Kochi

8 comments :

Anonymous said...

Great! We should increase the capability to build two carriers at the same money. We should invest more on Indian shipyards.

Gorshkov was a disaster. It was not meant to serve as dedicated aircraft carrier.

Shailendra said...

Shiv,
I am computer engineer by profession. I have so many cousins in my family who wants to join some aviation or naval design or any weapon design stream. All are very much motivated for serving nation by means of Engineering. Can you please post some articles how to build a carrier in defense engineering ?

natt said...

shailendra, I hope you make a career in defense engineering before making a carrier.. :))

Anonymous said...

"2.5 UK Govt. in spite of contemplating to replace their old small carriers since a decade by medium sized two in number 60,000-65,000 tonne aircraft carriers under CVF programme, have finally decided to go ahead with only one Queen Elizabeth to be in service in 2016. The second proposed carrier is expected to be converted to an amphibious commando ship with helicopters on board in lieu of JSF aircraft"


This hasnt be decided upon yet, the conservatives wont allow this- typicaly indian reporting.

Avinash said...

I am not an expert but just want to share my point of view -
With this design I think you can't land and take off jets at the same time. In a real war scenario I think it will be required to do both landing and take off at the same time.
I like the US carriers which has a 13 degree angular runways which you can do both landing and takeoff at the same time....

rajan.shimlacools said...

@ sharendra, if u have a B.Tech(Mech. or Electronics/CS/IT) degree u could apply almost 10 times a year in Armed Forces. Biggest hurdle to cross is SSB.

Anonymous said...

Then develop capabilities to serial produce a thousand aircraft carriers like paper ships for export. While china builds a thousand merchant ships lets build a few thousand more aircraft carriers.

Anonymous said...

Superb article shiv .i went searching the web about the mig 29k i found that the weapons payload is 5500kg which is very low for a multirole carrier aircraft and also read that the k cant take off with max payload is it true?