USE STEEL FOR THE ADVANCED AMPHIBIOUS ASSAULT VEHICLE
Carlton Meyer
Aluminum is much lighter than steel and relatively strong. Since it doesn't rust, it seems like the ideal metal for ships. However, no one uses aluminum for fighting ships, for the same reasons that the Marine Corps should require a steel hull for the Advanced Amphibious Assault Vehicle (AAAV).
Firstly, steel is stronger and more resistant to damage. A single .50 cal HMG round, RPG, or surf-zone or land mine striking a steel hull makes a hole and causes damage inside. However, cast aluminum shatters like a plate glass window. Hits cause large holes as hundreds of aluminum fragments blast forward causing casualties. The U.S. Army learned this when it tested early versions of the aluminum hull Bradley infantry fighting vehicle. Only after heavy criticism did changes occur. (see "The Pentagon Wars", by J. Burton, pp. 136-193) A steel armor coat was added and "spall liners" were installed inside to catch fragments. The latest model of the Bradley has an all-steel body.
A second problem is that aluminum can catch fire and produce intense heat that cannot be extinguished with water or regular fire extinguishers. Therefore, a small HEAT round may cause only minor damage, but can ignite a fuel tank that could heat an aluminum AAAV enough to burn it to the ground. In addition, burning aluminum produces deadly fumes which can instantly kill anyone inside. The British built a few frigates with aluminum in the 1970s. During the Falklands war, one of these ships, the HMS Sheffield, was hit by a single Exocet Anti-Ship Missile (ASM). The damage was not fatal since the ASM didn't explode, but the ASM's rocket fuel burned out of control so the Sheffield's aluminum hull caught fire and burned until it sank. In contrast, the steel hull frigate USS Stark was hit by two Iraqi Exocet missiles in 1988 and survived.
Perhaps the AAAV could use a plastic or composite armor hull. However, a steel hull is probably the best, even though its weight would reduce water speed. Greater crew protection and survivability is more important than a little more water speed, especially since AAAVs will operate ashore 99% of the time.
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