Some very high performance hot-rod platforms the Navy has been using for heavy duty acceleration testing highlight a new request for information from the service’s Naval Air Warfare Center Aircraft Division (Navair), which is pondering electromagnetic rails or other technologies to replace or augment two very cool legacy thrusting systems in two locations on opposite shores –- Jet sleds in Lakewood, New Jersey that use Pratt & Whitney J-57 jet engines (same ones that power the 707 and B-52) and rocket-powered sleds powered by Zuni motors at China Lake in California. "Current supplies of jet engines at [the jet car track site] and rocket motors at [the supersonic naval ordinance research tracks] are depleting," says the Navy in a recent request for information (RFI). Included with the RFI are some nice pictures of the jet sled.
The Navy uses three 1.5mi-long tracks in Lakewood, New Jersey, at the Jet Car Track Site (JCTS) to test arresting gear.
Google shows five tracks, but either two are out of commission or used for other purposes. The Navy says each track has a jet car that holds as many as four J-57 engines (see picture) producing up to 42,000 lb. of thrust to accelerate the car up to 250 kt. The car pushes a "deadload" with a tail hook that continues down the track after the car stops, capturing the arresting gear to simulate aircraft carrier operations. The deadload simulates an aircraft weighing between 15,730 lb. to 90,000 lb., with maximum speeds ranging from 162 kt. to 190 kt., respectively. The "operational tempo", or time between shots, is 45 min., a period the Navy would like to reduce to 10 min. with the replacement technology.
In China Lake, the Navy has a 4.1 mi-long track and a 3,000 ft.-long track at the Supersonic Naval Ordnance Research Tracks (Snort) to test weapons functionality and ejection seats. Each track uses a sled that holds Zuni rockets or other larger rocket engines that can accelerate payloads on sleds from 700-75,000 lb. to as fast as Mach 5. A "typical" payload, says the Navy, weighs 3,000 lb. and is accelerated to 1,100 feet per second (652 kt.). Some payloads stay on the sled; others use a second-stage sled with 2-4 additional Zuni rockets to accelerate further.
"Navair understands that one launcher system may not be a direct replacement for both the jet engines for testing at JCTS and rockets for testing at SNORT," the RFI states, adding that solutions can be part of a "hybrid approach" with other propulsion systems, although the Navy would prefer a propulsion technology that is scalable and can meed the needs of both locations.
The Navy says the RFI is part of a trade study to determine "what other electromagnetic propulsion technology could be used to replace the use of jet engines, including but not limited to electric motors, magnetic levitation (maglev) and a hybrid of multiple propulsion technologies".