Naval Air Systems Command Linear induction motors will power three new Ford-class carrier launch systems.

As plans for the new Gerald R. Ford-class aircraft carriers develop, a new launch system is being developed in Lakehurst, N.J. The electromagnetic aircraft launch system [EMALS] will use linear induction motors to handle heavier aircraft with higher takeoff velocities in a greater sortie rate using fewer people.

EMALS will supplant tried and tested steam catapults by 2014, when the new Ford-class ships are ready for deployment. They will not be retrofitted onto current Nimitz-class carriers. To start full-scale testing late next year, the Navy has been constructing, since 2004, a linked four-building complex at the Naval Engineering Station, Lakehurst, the Navy's center for steam catapults.

The $37-million, design-build project consists of a one-story, pre-engineered metal building to house the energy storage system and office space, a temporary Quonset hut sheltering the 348-ft-long launch-motor trough mock-up, an under-ground building for power conversion space and a steel integrated catapult control station. Douglas S. Swope, Naval Air Systems Command EMALS test site manager, says, "Initially, we will launch wheeled dead loads of 10,000 to 100,000 lb at typical aircraft launch speed." The loads will not leave the ground and will be arrested by cable. Eventually the full variety of carrier aircraft will be tested.

Douglas S. Swope Launch trough meets tight tolerances.

One of a Kind

For design-builder Hensel Phelps Construction Co., Greeley, Colo., the job has aspects that are one of a kind. "Essentially we are replicating shipboard conditions," says Jeff Brown, Hensel Phelps project manager. "Only instead of 900 ft of ballistic steel to distribute the launch force, we have to narrow it to a steel trough that is tied to reinforced concrete walls." The launch trough wall and floor is built in a wetlands area that required a cofferdam, dewatering and water treatment. "Our excavation was 18 ft deep, 15 ft below the water table. The steel trough is shaped like a flat-bottom Y for stiffness and consists of 1.5-in-thick, 50-ksi steel plate. The floor and walls are 40-in.-thick, 8,000-psi reinforced concrete for stiffness to hold the steel in place while the force of the launch travels from one end to the other. It's a shock-wave effect."

He also notes that the rails, which were installed in 20-ft segments, were covered during construction to modulate temperature because thermal expansion could disrupt the required 1⁄8-in. tolerance. Sippel Co., Ambridge, Pa., was the steel fabricator for the job. The steel trough was welded to an inbed in the top of the walls and bolted to the floor by millwrights.

For security reasons, the Navy would not discuss the full cost nor describe in detail the test equipment. On shipboard, the system would consist of six subsystems: prime power interface to draw and store energy, energy storage, energy distribution, power conversion, launch motor and launch control. It will deliver 90 Mft-lb of energy to launch all types of aircraft at a consistent acceleration. Fewer mechanical components means less wear and maintenance, and without the steam support system, space is freed up for other functions. Donald C. Winter, secretary of the Navy, calls this “one of the most significant advancements in aircraft-carrier technology since the development of nuclear power.”