Carrier Launch System Passes Initial Tests

Recent tests at NAS Lakehurst, N.J., should have builders of the USS Gerald R. Ford (CVN-78) sleeping more easily. The Navy’s risky bet in the design of the Ford—its reliance on an all-electric replacement for the steam catapult—appears to be paying off.

Problems and delays with the electromagnetic aircraft launch system (Emals) last year were a threat to the carrier, because its design and construction reached a point where reverting to steam would have been difficult and expensive. With Emals in mind, the Ford-class features a much more powerful electrical generation and distribution system than the predecessor Nimitz-class ships, along with the virtual elimination of steam-energized services such as heating, galleys and pumps and 10 km. (6 mi.) of steam lines.

The Navy has delayed delivery of the $11.5-billion carrier for budgetary reasons twice. (Commissioning is expected in September 2015.) The scheduled progress of Emals now matches the carrier’s build schedule but with so little slack in some areas that the Navy is continuing to monitor development of the system closely.

The land-based prototype of Emals at Lakehurst started high-speed “no load” test runs in April, and will start to accelerate with dead loads—ballast—at speeds increasing from 50-180 kt. At prime contractor General Atomics’ plant in Tupelo, Miss., prototypes of the Kato Engineering power modules are undergoing accelerated life testing, performing 6,800 power cycles. So far, tests show no signs that the powerful electrical surges cause electromagnetic interference with aircraft, ammunition or ejection seats. The first aircraft launch at Lakehurst is expected by year-end.

Progress! A couple of weeks ago Lakehurst reported an uncontrolled retraction on that cat which did some damage, but apparently not too much. Starting a no-load program is a significant step, and proceeding to deadloads will be even bigger.

The deadloads are enormous carts with multiple, large aircraft tires. They have a pair of friction brake assemblies that drag behind the vehicle in special tracks built into each side of the catapult track. The number of brake assemblies depends on the size of the deadload and the expected launch energies; I’ve seen 16 sets of brakes on a 110,000 pound deadload down there. The deadload vehicles are just enormous and are heavily instrumented to document all of the acceleration energies during the shot. That data is used to make tables that the ship will use to calibrate their installations.

When the launch is complete and the deadload passes the end of the catapult, the brake tracks suddenly transition to double the thickness and the brakes kick in and stop the deadload, the runout, or distance the deadload travels beyond the end of the catapult depends on how fast it’s going and how heavy it is. The tracks run out quite a way down the runway. When it stops, they take an aircraft tow tractor and push the deadload back to “battery”; pushing on the brakes makes them open and release.

Just in cast, at the end of the deadload tracks is a wire barrier that is set up high enough to engage the front of the deadload. On each end of that wire are several lengths of anchor chain, and the further you pull it out, they heavier it gets. Positive stopping power.

After I left the test sites, one of the crew at the cat site got really sloppy firing deadloads, gave confused hand signals to the deckedge operator, and ended up in front of a deadload when it launched. He rode the front of that deadload all the way down the cat track on the power stroke, but when the deadload brakes kicked in, it threw him skidding down the runway. On the way by, he struck one of the steel posts that held the emergency barrier up and it took his leg off above the knee. One of the civilians at the site was driving up the service road in a jeep and saw the whole thing unfolding, and was as the guys side immediately and saved him from bleeding out. He was extremely lucky to have lost just a leg (and a lot of skin...).

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