In the March 2001 issue of US Naval Proceedings, Commander Joseph E. Skinner, US Navy, wrote:
"Catamaran and trimaran hull designs are faster, more stable in high sea states, have similar internal volumes as single-hull ships, and are more fuel-efficient than conventional hull designs. In addition, a trimaran's outriggers add stand-off range to the center hull, where vital equipment (computers, propulsion, living spaces) would be located. This stand-off range would make the ship more resistant to damage from attack."
This is a summation of what engineers have known for years. The Royal Navy has built a prototype, the HMS Triton (left), which was deemed very successful. However, the US Navy has refused to consider trimaran hulls. The key point made by Commander Skinner is that trimarans are more resistant to damage -- far more resistant. One missile or torpedo can disable and possibly sink a modern cruiser, destroyer, or frigate. However, a well-designed trimaran warship can withstand several hits and keep fighting.
Modern ships are extremely vulnerable to mass guided missile attacks. The US Navy's old solution is for carrier fighters to shoot down attack aircraft before they can launch missiles. However, modern cruise missiles can be fired beyond a carrier's aerial defensive ring, and ships must also operate near shore where ground launchers or attack helicopters may suddenly appear.
While anti-missile systems, stealth designs, and decoys are effective, they cannot provide 100% protection, especially against dozens of incoming missiles. Ships must be able to withstand hits and keep on fighting. In the past, navies relied on armored ships. The best protected ships were the Iowa battleships, which were nearly invulnerable to non-nuclear missile attack. They were struck with 5-inch (127mm) rounds and 152mm shells and suffered no damage. Armored ships may be reconsidered, but the best protection for smaller warships are "redundant" trimaran hulls.
The design of the HMS Triton is excellent, but should be modified to protect the entire ship. The outer hulls must extend the entire length of the ship, which is common on modern catamaran (twin hull) ferries. Another option is to construct a slat metal "fence" or "skirt" that extends forward from the outer hulls above the waterline that cause incoming missiles to explode before striking the center hull. These may be lowered into the water when operating at slow speeds in mine infested waters for added protection.
The outer hulls will be compartmentalized to limit flooding after a hit. In addition, the superstructure will be protected by a slat fence extending upward from the outer hulls. If this interferes with radar, slat fences can pop-up from the outer hulls when incoming missiles near. The missiles will blow a hole through the fence, but the explosion will occur too far from the superstructure to cause major internal damage.
The outer trimaran hulls will protect the main ship hull from torpedoes and sea mines as well. Many torpedoes and mines are designed to explode under a ship and cause a huge bubble of air which lifts the ship into the air and cracks the hull. However, outer hulls on a trimaran provide support for the main hull. Even if the main hull is heavily damaged and flooded, the outer hulls have plenty of buoyancy to keep the ship afloat. The outer hulls also shroud the infrared signature of the main engines. A final advantage of trimaran hulls is that the space between the hulls is ideal for carrying and supporting small boats and landing craft through large hatches in the deck. The numerous advantages of trimaran ships make proposals for building new single-hull warships outdated.
For more information, visit the DERA Triamaran Project website.