EMALS: Next Gen Catapult


CVN 78 painting.jpg

The newly-named USS Gerald R. Ford (CVN 78) is the first of the next generation of U.S. Navy aircraft carriers, and with these ships are plans for the incorporation of radical new technology.

The most basic mission of an aircraft carrier is to launch and recover . . . duh . . . aircraft. The Electro-magnetic Aircraft Launch System is being fielded to take care of what we call the "shooting off the pointy end" or launch part.

In very basic terms, the legacy steam catapult system uses energy to "push" the shuttle down the track to launch aircraft. EMALS uses magnetic fields to "pull" the shuttle to affect the same end.


EMALS consists of four major subsystems:

Linear Induction Motor (LIM)

The LIM, developed in a configuration for the flight deck, is a compact, modular, integrated structure. The motor design will tolerate the range of conditions experienced in the flight deck environment and operating scenarios. The simple moving shuttle will interface with the aircraft in the same manner as the existing catapults.

Power Conversion Electronics

The power conversion electronics derive power from the energy store and convert this power to constant-current ac with increasing frequency and voltage to drive the shuttle along the launch stroke. Based on solid-state technology that GA uses in its line of commercial power equipment, the power electronics are packaged as compact modules in cabinets that are located below-deck in the carrier.

Shipboard Energy Store

The shipboard energy store consists of rotating energy storage machines connected to the power trains and LIM.

Control System

The EMALS achieves a peak-to-mean force ratio much lower than those of steam catapults by using a state-of-the-art control system to control the current into the LIM. (Source: General Atomics)

So what are the basic advantages of EMALS over the time-tested steam catapults? "We don't have all that steam piping running all over the ship," Capt. Steven Rorke, NAVAIR's program manager for shipboard launch and recovery systems, explained during a recent interview with DT. "The steam stays in the plant generating electricity and then the electricity runs around the ship."

The second major attribute is the growth potential of the system in terms of dealing with what Capt. Rorke called "the air wing of the future" including unmanned vehicles. "We can control the launch sequence much more precisely."

And lastly, Rorke claimed EMALS will require fewer Sailors to operate and maintain.

"The technology is proven," said Rorke. "We developed a full-scale but about half-length track that we tested at the Naval Engineering Station at Lakehurst to prove the control theory and the logic. We're in the phase now of building shipboard representative equipment."

But although "the technology is proven," like all good acquistions programs, issues remain unresolved. For EMALS the main issue is non-trivial: Will it fit on the carrier? "We're not the only customer on the ship," Rorke said. "Finding real estate to put everything in is a challenge."

And as with most aircraft development programs, keeping the weight of the system under control is a challenge.

In any case, the folks at General Atomics, NAVAIR, and NAVSEA have some time to figure it out. CVN 78 isn't scheduled to sail into harm's way until 2015.

And speaking of catapults:

(Remember that guy from "Fargo"?)

-- Ward

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