How Things Work: Electromagnetic Catapults
From zero to 150 in less than a second.
- By Tim Wright
- Air & Space magazine, January 2007
PH3 Jason A. Fults / US Navy
(Page 2 of 2)
An electromagnetic catapult can launch every 45 seconds. Each three-second launch can consume as much as 100 million watts of electricity, about as much as a small town uses in the same amount of time. “A utility does that using an acre of equipment,” says lab engineer Mike Doyle, but due to shipboard space limitations, “we have to take that and fit it into a shoebox.” In shipboard generators developed for electromagnetic catapults, electrical power is stored kinetically in rotors spinning at 6,400 rpm. When a launch order is given, power is pulled from the generators in a two- to three-second pulse, like a burst of air being let out of a balloon. As power is drawn off, the generators slow down and the amount of electricity they produce steadily drops. But in the remaining 42 seconds between launches, the rotors spin back up to capacity, readying themselves to release another burst of energy.
Working from the scale model in the Naval Air Warfare lab, designers developed the electronic hardware and software needed to build an EMALS prototype, which can accelerate dead-weight test articles (massive metal frames on wheels) to 165 mph in three-quarters of a second on a track just 100 feet long.
Care has been taken to make the launch process as similar as possible to current steam systems to help launch crews ease into the new technology. Pilots, as they position their aircraft for a catapult shot, won’t be able to tell if they are launching with electromagnetics unless they happen to notice the absence of steam escaping from the deck.
Electromagnetic catapult technology already has the ability to launch any aircraft now in the Navy inventory and any the Navy has ordered. With the new launch system’s potential to achieve acceleration forces reaching 14 Gs, human endurance may be one of the few limitations it faces.