In terms of getting aircraft airborne, both the US Navy and the Royal Navy are looking at several options in the replacement of the steam catapult with an electromagnetic launch system.
In the USA, Kaman Electromagnetics is working on the Electro-Magnetic Aircraft Launch System (EMALS). Project officials believe that the EMALS could replace steam catapults on Nimitz-class carriers or be incorporated on a next-generation aircraft carrier. Amphibious assault ships, Invincible-class "ski-ramp" carriers and mobile offshore platforms are also candidates for the EMALS.
The EMALS concept uses linear motor technology to propel objects with electromotive forces. A proof-of-principle half-scale electromagnetic catapult was designed and built by Kaman in 1986. The laboratory demonstrator model showed promise, leading to continued US Navy support.
In the current critical-component-demonstration (CCD) phase, full-scale hardware will simulate the complete launch cycle. Electro-magnetic interference (EMI) is of prime concern because of proximity with aircraft avionics and weapons. The USN is addressing the issue.
The EMALS, which would be driven by a gas-turbine engine, is designed to fit within the confines of the existing steam catapult trough. Kaman expects 70% launcher efficiency, compared with about 6% launcher efficiency for the steam catapults. The EMALS would be able to launch an aircraft every 45s, say company officials.
The goal is to test the EMALS at the in-ground catapult site at Naval Air Warfare Center Lakehurst. The prototype could then be installed on an aircraft carrier for sea trials. A production decision could be made by 2007, with initial production deliveries following in three years.
INNOVATIVE CONCEPTS
As well as examining conventional-carrier technologies, the US Navy is also exploring some more arcane ideas. One concept involves creating a floating island consisting of linked oil platforms, which would hold considerable numbers of main battle tanks, fuel and other war-fighting supplies below deck. On top, cargo aircraft as large as the Lockheed C-130 would be supported.
The concept of strategically placing as many as three Mobile Offshore Bases (MOBs) near the world's trouble spots continues to garner interest from US military planners, who believe that the modified floating offshore oil platforms could be used to provide logistics and support functions for US military forces.
Six semi-submersible modules, each 165m long, 98m wide and 70m high, and including command, thruster, logistics depot and cargo transfer units, would be linked, creating 250,000m2 (2.7 million ft2) of environmentally controlled storage space for fuel, tanks, ammunition, spare parts and other war supplies.
On top of the huge structure would be a 900m (3,000ft)-long runway able to accommodate C-130 transports, short take-off and landing aircraft and helicopters. The MOB could be used to repair aircraft and as a staging base for special operations forces. (MOBs are also envisioned as launch sites for commercial satellites and as offshore commercial airports.)
Supporters believe that they could be fielded in as little as two years. The 40-year life-cycle cost of one six-module MOB is estimated to be $3.5 billion.
Proponents, including Adm William Owens, vice-chairman of the Joint Chiefs of Staff, say that the MOB - with a top speed of 10kt (18km/h) --should not be viewed as a threat to the aircraft carrier. Although able to handle tactical military transports, very short take-off and landing aircraft, carrier auxiliary aircraft and helicopters, the MOB is not designed to be a staging platform for high-performance combat aircraft.
Rather, it would serve as an offshore re-locatable air base - an alternative to foreign bases such as the Subic Bay Naval Complex, to which the USN lost access four years ago. (The concept was conceived when US forces were evicted from Clark AB and Subic Bay. As a result, the MOB has been dubbed "USS Subic Bay" by supporters, who feel that US naval forces should not be encumbered, by sovereignty issues.)
Edward Hickey, director of logistics operations for Brown & Root, a major international engineering and construction firm, developed the MOB concept under contract to the Pentagon's Advanced Research Projects Agency.
He says that the MOB, with limited self-defence capabilities and protected by naval combatants and tactical aircraft, is survivable. He says that it would be virtually impossible to sink and that the runway would be easily repairable. "It is far more survivable than an aircraft carrier or any other surface combatant," he concludes.
Hickey adds that scale-model testing at the David Taylor Research Center, Carderock, Maryland, shows that the MOB can ride out typhoons, hurricanes, and rough water up to sea-state nine.
Recently, oversight of the MOB project went from ARPA to the USN. The Office of Naval Research may inherit the programme, but the Naval Sea Systems Command (NAVSEA) said in early April that it is seeking contractors "...to participate in informal discussions with the Navy to assist in refining MOB concepts. The Navy's goal is to contract for concept and feasibility studies where it believes it is warranted."
Some would argue that NAVSEA is re-inventing the wheel, and Hickey believes that the solicitation "...makes very little sense". Hickey adds, "Nothing can be done under a NAVSEA contract that will add value to what we have already accomplished."
Source: Flight International
