PGM-11 Redstone: The V-2's Heir That Lifted Alan Shepard and Explorer 1

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On May 5, 1961, Alan Shepard became the first American in space atop a Mercury-Redstone, a rocket descended from a missile built to carry a 3.8-megaton W39 nuclear warhead. The PGM-11 Redstone, the first large American ballistic missile, was a short-range weapon developed from the German V-2 by Wernher von Braun's Operation Paperclip team at the Army Ballistic Missile Agency in Huntsville, Alabama. It was named in April 1952 after Redstone Arsenal, which took its name from the area's red rocks and soil. The first launch, from Cape Canaveral's Launch Complex 4A on August 20, 1953, ended in engine failure after one minute and 20 seconds. Turbopump cavitation was fixed for a 55-mile flight in January 1954, but on May 5, 1954, the engine cut off one second after liftoff and the missile fell back and exploded on the pad, drawing von Braun's famously blunt explanation to Major General Holger Toftoy.

Von Braun imposed strict workmanship standards, and the Army declared the Redstone operational in mid-1955. Built by Chrysler with a Rocketdyne engine, it stood over 69 feet tall, weighed more than 61,000 pounds and made 78,000 pounds of thrust burning 75 percent ethyl alcohol and 25 percent water with liquid oxygen, reaching Mach 5 to 6 and a range of up to 201 miles under the Ford Instrument ST-80 inertial guidance system. It was the first U.S. missile to carry a live nuclear warhead, in the 1958 Hardtack tests in the Pacific, and served with the 40th and 46th Field Artillery Groups in West Germany from 1958 to 1964, until slow liquid fueling made it obsolete against solid-fuel missiles like the Pershing. Surplus Redstones became the Jupiter-C, which as Juno I launched Explorer 1 in 1958, and the Mercury-Redstone, with tanks stretched six feet and a return to alcohol fuel.

• The Army wanted mobile tactical nuclear missiles to stop a Soviet ground invasion of Europe, while the Air Force championed intercontinental missiles.
• Von Braun told his team that missile reliability required "that the target area is more dangerous than the launch area."
• Water in the fuel lowered the combustion temperature enough to keep the engine from melting, and later versions used the more powerful, toxic hydyne.
• About 20 to 30 seconds after engine shutdown, the thrust unit separated, leaving the smaller missile body to fly a controlled ballistic arc to the target.
• In the Sparta program of 1966 and 1967, modified Redstones flew from Woomera, South Australia, and a donated spare launched Australia's first satellite, WRESAT, in November 1967.