Internal Combustion Catapult
Internal Combustion Catapult is a launch-assist mechanism utilizing liquid propellant as the energy source instead of steam. Benefits include elimination of steam system components; and reduced weight, airframe stresses and mainten-ance. This technology is similar to that used in automotive air bags.
The steam generation system may be replaced and a plurality of combustors positioned at the aft end of the launch tube facing the trailing end of the piston. Each of these combustors includes an injector assembly for supplying a combustible propellant. At least one igniter is operatively positioned with respect to the combustor to ignite the combustible propellant to form hot launch gases at high pressure to project the piston down the launch tube to launch the aircraft.
A water manifold injects water into the combustion gases to cool them and form steam to propel the piston down the launch tube. The propellant may be a propellant composed of, for example, hydroxylammonium nitrate and a hydrocarbon fuel or a bipropellant system using a combustible fuel composed of organic substances and an oxidizer such as ammonium nitrate, hydroxylammonium nitrate, hydrazine, nitrogen tetroxide and liquid oxygen.
The internal combustion catapult should be a closed-loop control system in contrast to the conventional steam catapult that is open-loop control. Ideally the system is easily retrofitted to existing steam catapult launchers. It is also desirable that the launch system sense transient conditions such as loss of power from the launching aircraft due to engine failure and compensate by increasing launch force to assure the desired launch end speed. These and many other requirements cannot be met with a conventional steam launching system utilizing the steam from the ship's propulsion system.
The C14 Internal Combustion Catapult was developed in the 1950s and successfully launched planes. It used the same launch engine as the steam catapult, but was more powerful than the steam catapult. Used JP5 and compressed air burned in a single large combustor. It was difficult to establish consistent flame fronts and consistent launch end speeds. IT suffered from lack of security oversight and man-caused faults. Originally intended for CVN65 Enterprise.
Inability of C14 catapult to deliver consistent end speeds to launched aircraft and “manmade reliability issues” removed it from consideration for USS Enterprise. Replaced by the C13 steam catapult aboard the USS Enterprise at new construction. Bank of large air compressors intended to supply the C14 catapult still aboard the Enterprise. The 1950’s technology ready to support the ICCALS catapult technology in spite of “reliability issues” and 2010’s technology is ready to support an internal combustion catapult superior to either the steam catapult or EMALS.
Technology changes have been made to improve the technical viability and performance of the Internal Combustion Catapult. More efficient oxidizer and oxidizer management. Subdivision of the combustion event into multiple combustors which average out combustion instabilities to deliver a smooth and controllable highly variable mass flow of combustion gas and steam from the combustor assembly to the launch engine. A controlled constant or increasing launch acceleration pressure during the launch event over the length of the launch stroke.
In May of 1998, NNS management decided that it would be more desirable to the Navy for NNS to support EMALS, thus NNS terminated the ICCALS program and assumed the role of systems integrator. The ICCALS program was producing and testing hardware when it was terminated, leaving only the General Atomics electromagnetic catapult in competition as a systems supplier in place of the C13-2 steam catapult.
ICCALS is backfittable at low cost to all of the C13-1 and C13-2 operational carriers, providing a great increase to the fleet in capability, both offensive and defensive and range of planes launched. EMALS is not backfittable to the Nimitz Class cariers.
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