sought a replacement with either a larger yield or equivalent destructive power. The result was the W-58 warhead used in a "cluster" of three warheads for the Polaris A-3, the final model of the Polaris missile. One of the initial problems the Navy faced in creating an SLBM was that the sea moves, while a launch platform on land does not. Waves and swells rocking the boat or submarine, as well as possible flexing of the ship's hull, had to be taken into account to properly aim the missile. The Polaris development was kept on a tight schedule and the only influence that changed this was the USSR's launching of SPUTNIK on October 4, 1957. This caused many working on the project to want to accelerate development. The launch of a second Russian satellite and pressing public and government opinions caused Secretary Wilson to move the project along more quickly. The Navy favored an underwater launch of an IRBM, although the project began with an above-water launch goal. They decided to continue the development of an underwater launch, and developed two ideas for this launch: wet and dry. Dry launch meant encasing the missile in a shell that would peel away when the missile reached the water's surface. Wet launch meant shooting the missile through the water without a casing. While the Navy was in favor of a wet launch, they developed both methods as a failsafe. They did this with the development of gas and air propulsion of the missile out of the submerged tube as well. The first Polaris missile tests were given the names “AX-#” and later renamed “A1X-#”. Testing of the missiles occurred: September 24, 1958: AX-1, at Cape Canaveral from a launch pad; the missile was destroyed, after it failed to turn into the correct trajectory following a programming-error. October 1958: AX-2, at Cape Canaveral from a launch pad; exploded on the launch pad. December 30, 1958: AX-3, at Cape Canaveral from a launch pad; launched correctly, but was destroyed because of the fuel overheating. January 19, 1959: AX-4, at Cape Canaveral from launch pad: launched correctly but began to behave erratically and was destroyed. February 27, 1959: AX-5, at Cape Canaveral from launch pad: launched correctly but began to behave erratically and was destroyed. April 20, 1959: AX-6, at Cape Canaveral from launch pad: this test was a success. The missile launched, separated, and