30.08.10Conventional aircraft can take off the deck in two ways – by catapult (traditional steam or perspective electromagnetic one) and by free-run method (from ski-ramp). Tertium non datur. Both methods have pros and cons, and – thereafter – opponents and supporters.
Text: RusNavy.com, D. Yerofeev
Combat Capability [42%], Role and Missions, Structure of the Navy, in-service ships, surface ships, submarines, chronology.
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Home / Science / Scientific problems of shipbuilding / How should Russian flattop look like? / Part V. Catapult or ski-ramp?
Part V. Catapult or ski-ramp?
Soviet Navy never had a catapult-equipped carrier. There's a bunch of reasons for that, both technical and "political". On the one hand, being tasked to develop steam catapults, the Proletarsky Factory coped with that mission, mildly speaking, incompletely. The plant faced problems related with cylinders' bore, their sealing and lubrication systems, catapult heating in wintertime etc. After long drudgery only one pilot sample of catapult was mounted on ground-based aircraft training system NITKA which was constructed in Novo-Fedorovka, Crimea. The construction of NITKA simulator was kicked off in 1977. It was classified as special importance object, and work progress was under personal control of Navy Commander-in-Chief. Nevertheless, that catapult (then called "speedup device") had never shot an airplane …
Instead of this, the attention was refocused on ski-ramp takeoff which was found more preferable (and above all, incomparably simpler and cheaper) alternative to catapult. An order was made to shut down all development works on catapult. There are different opinions about the reasons of such controversial decision. In particular, they talked of cost cutting, time lag in development of full-fledged catapult, and even intentional desire to prevent reassignment of financial flow in defense expenditure structure oriented on land forces if classic aircraft carriers would appear.
Deck-based fighter MiG-29K.
By all appearances, statement of directors of Sukhoi and Mikoyan design bureaus also played not insignificant role. They assured that their aircrafts – shipborne versions of Su-27 and MiG-29 fighters with high thrust/weight ratio – would be swimmingly operated even without catapults, just with ski-ramps. As a matter of fact, the decision to apply ski-ramp for conventional aircrafts was unique, as in the West ramps were used only by VTOL planes.
At first glance, a ski-ramp really has a huge number of advantages. It is inexpensive and doesn't need steam-generating plant, maintenance and repairs. Finally, it saves effective capacities and weight, which affects a carrier's displacement and cost.
However, all those advantages of ski-ramp are pale in comparison with its drawbacks. First and foremost advantage of catapult is its low threshold of sensitivity to takeoff conditions. Roughly speaking, a catapult-equipped aircraft carrier can continue takeoff operations in such ship's motion/wind/sea disturbance conditions when ramp-equipped carrier can not.
The second essential advantage of catapult is higher takeoff rate. Let us assume that maximum amount of planes must be in the air as soon as possible. With its four catapults, a US carrier is capable to shoot one aircraft in every 15 seconds. Kuznetsov has only three takeoff tracks. Moreover, two bow tracks are not intended for fully-loaded aircrafts! They can take off Kuznetsov only from one track which starts far behind the midship, i.e. an aircraft must run almost the whole flight deck! Comparing to catapult, takeoff rate of ski-ramp is at least twice lower.
It must be kept in mind that ski-ramp takeoff implies high requirements to thrust/weight ratio. Engines start working at full-thrust (afterburner) mode before an aircraft runs out; this leads to premature end of service life and increased fuel consumption. Besides, lower takeoff rate makes aircrafts wait longer in assembly point, which also means waste of fuel, reduction of operational radius etc.
Thus, if we want to build an adequate aircraft carrier but not "shorties" like Giuseppe Garibaldi or Principe de Asturias, we should design a catapult.
In this context it would be relevant to develop electromagnetic catapult, which is more advanced than steam one. Take note that development work on such catapult started in our country as early as 80's, well before the U.S. The Institute of High Temperatures in cooperation with Central Aerohydrodynamics Institute and Mikoyan Design Bureau had been holding research project named Shampun (lasted almost 15 years) oriented on electromagnetic takeoff and landing system. Supposedly, that system was designed for future aircraft-carrying ships and ground-based mobile airfields.
HMS Daring (D-32) air defense destroyer.
It must be borne in mind that such energy-intensive equipment requires that a carrier must have more powerful electric generators. This makes it easier to use entirely electric power plant. We recall that the first fully electric surface warship – HMS Daring (total displacement is 8,010 tons) – was commissioned into the Royal Navy on November, 2008. Five more ships of such class are also planned to be delivered by 2012. Moreover, French engineers from THALES have come to grips with creation of electric aircraft carrier. By the way, THALES exhibit booth presented at EURONAVAL-2008 attracted great attention of Russian Navy Commander-in-Chief Vladimir Vysotsky.
Table of contents
Part I. The story of Soviet carriers
Part II. Ideological bomb
Part III. And so the need was swelling…
Part IV. What kind of carriers and fighters do we need?
Part V. Catapult or ski-ramp?
Part VI. Choosing designer and shipyard
Part VII. Renewed Navy headed by a carrier