Una noticia no muy fresca, pero con detalles interesantes...
Carrier Launch System Passes Initial Tests
Jun 7, 2010
By Bill Sweetman
Washington
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.
Initial Emals components for Ford are due at the Newport News shipyard in May 2011. The tightest schedule concerns the 12 power units, which are high-speed motor-generators weighing 80,000 lb. each and functioning as flywheel energy storage and release units. Some are not due at the yard until the day before they are installed.
Emals will deliver energy more flexibly than Nimitz-class steam catapults. The F-35C Joint Strike Fighter demands more launch energy than the F/A-18E/F, and Emals will allow the Ford to launch the JSF at maximum weight with less wind-over-deck.
Emals can also be set to lower energy levels than a steam catapult, allowing it to launch small, lightly loaded aircraft like unmanned aerial vehicles.
The Ford class features a new advanced arrester gear as well, also produced by General Atomics and replacing hydraulic rams with a water turbine and induction motor, permitting a finer setting of arresting force and reducing the need for manual adjustments between landings. Like Emals, it is expected to allow the carrier to operate heavier and lighter aircraft than the current Mk. 7 arrester gear. Unlike Emals, it is intended to be backfitted to Nimitz-class carriers.
The carrier will be part of the process of introducing a landing guidance system to the Navy: the Joint Precision Approach and Landing System (Jpals). It will be one of the first ships with Jpals, which is slated to be on all carriers and large amphibious transports by 2018. The second Ford-class ship, CVN-79, is due to be the first carrier without SPN-41 and SPN-46 radars, which provide carriers with an automatic landing capability.
Adoption of Jpals is urgent for the Navy because current radars will not be supportable after the early 2020s. Jpals is also associated with the F-35C, because the fighter’s reduced radar cross-section means that current radar-based autolanding systems cannot acquire it. The installation of Jpals on carriers will match service entry of the F-35C.
The first increment of Jpals will be qualified for flight guidance down to 200 ft. and 0.5-mi. visibility. Accuracy is intended to be sufficient for an automatic landing, and that capability is being demonstrated as part of the Northrop Grumman X-47B Navy Unmanned Combat Air System program.
The key to its accuracy is shipboard-relative GPS, which uses two GPS receivers—one forward of the island on the starboard side and the other on the portside stern. The space between the sensors and their relative location allows the system to measure the position of the ship accurately and track its movement—speed, pitch, roll and heave—with the aid of three Northrop Grumman LN-270 inertial reference units. Using the same differential GPS technique, Jpals also provides an accurate aircraft position. A data link allows the system to transmit automatic landing guidance.
Credit: US Navy
http://www.aviationweek.com/aw/generic/ ... 228803.xmlRemarco...
Adoption of Jpals is urgent for the Navy because current radars will not be supportable after the early 2020s. Jpals is also associated with the F-35C, because the fighter’s reduced radar cross-section means that current radar-based autolanding systems cannot acquire it.
Unlike Emals, it is intended to be backfitted to Nimitz-class carriers.
Tienen pensado backfittear Nimitz con EMALS y JPALS
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