We all know aircraft carriers are big. Really, really big. But the runways simply aren’t long enough for most planes to generate sufficient lift before they tumble off into the water. For almost as long as aircraft carriers have been built, they’ve used steam-powered catapults to launch the fighters and bombers they carry. That’s a pretty old-fashioned technology when you’re launching supersonic or stealth aircraft that cost $20 million or more each.
Current steam catapults gives naval aircraft the extra boost they need to gain enough lift with a launch footprint of only a few hundred feet. Steam catapult systems use about 1,350 pounds of steam for each aircraft launch, which is usually delivered by piping it from the nuclear reactor. Add the required hydraulics and oils, the water required to brake the catapult, and associated pumps, motors and control systems. The result is a large, heavy, maintenance-intensive system that operates without feedback control. The sudden shock shortens airframe lifespans for carrier-based aircraft. But for the time being, steam is the only option for launching aircraft from carrier decks.
The US Navy is now testing a replacement system called the Electromagnetic Aircraft Launch System, or EMALS. The first at-sea test platform is currently being installed on the USS Gerald R. Ford. It uses a pulse of electromagnetic energy to launch planes much more smoothly and efficiently than the old steam catapults. Suprisingly, the EMALS uses less power than steam catapults. The switch to an electromagnetic linear motor drive means smooth acceleration, improved reliability, and a much more efficient design.
EMALS uses an approach analogous to an electro-magnetic rail gun, in order to accelerate the shuttle that holds the aircraft. EMALS has been tested with the F/A-18, E2D Advanced Hawkey, and upcoming F-35 among others. One important aspect of this system is that operators can adjust the launch speed based on the weight of the aircraft.
The ground-based EMALS tests have all been successful, but the upcoming tests aboard the USS Ford will be the main event. If all goes as planned. the US Navy could permanently move away from the archaic steam catapult.
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