via Sikorsky History Blog.
Sikorsky won a U. S. Navy contract to build a prototype ASPB (Assault Support Patrol Boat) boat. Sikorsky designed the ASPB for its environment, the ASPB warship was in reality a floating tank, and much more. It was approximately 50 feet long and 20 feet wide and powered by three Pratt & Whitney PT-6 turbine engines connected to three water-jet pumps. On smooth river water the ASPB could reach speeds of 50 miles per hour and maneuver in only water 4 feet deep. Also this type of drive system allowed the ASPB to turn rapidly, maneuverability was critical because of limited space within the delta rivers.The United States Navy was involved in protracted warfare in the Deltas of Vietnam and along its coasts.
It had a central turret with a 105 millimeter howitzer and two 20 millimeter automatic cannons. The howitzer was the most command artillery piece in the Army's inventory and parts and ammunition was readily available. The howitzer is capable of firing directly at an enemy or indirectly at high angles over obstacles in support of our ground troops. The 20 millimeter cannons were rapid fire machine guns for short range attacks and also they were used to defend the ASPB. Both weapons allowed the ASPB to lay down fire outside the range of the Viet Cong's 300 meter range of their rocket propelled grenades. Also a small machine gun was installed in the bow of the ASPB for quick reaction defense in case of an ambush.
A unique armor system was designed for the ASPB called "bar armor". It is a light steel bar grill mounted 3 to 4 feet away from the hull and superstructure. This armor defeated the Viet Cong's rocket grenade by exploding the grenades armor piercing warhead against the "bars" before it reached the ASPB. The use of this armor allowed the ASPB to be designed with a lighter armored hull reducing the ASPB's overall weight.
The ASPB was delivered to the U. S. Navy at the end of 1969, but never saw operational use because the war ended. However the ASPB was used by the Special Forces to train for riverine warfare until 1980 when it was taken out of service.
In reaction to that fight they developed small boats that mounted 105mm Howitzers, 20mm Cannons and a 50 cal machine gun.
Fast forward to today and the US Navy expects to be engaged in battle along coastlines in what it now calls the littoral zone. Its answer to that fight now is to develop a ship that mounts a 57mm cannon, two 30mm cannons weighs over 1500 tons and has a flight deck.
Who is right? The Navy of the past or the Navy of today?
