Pershing 1 and 1a: Thrust Reversal Ports, the Land Train and Zero Defects

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The MGM-31 Pershing was a two-stage, solid-fueled theater ballistic missile, and solid fuel posed a hard problem: once lit, the motor cannot be shut off. Before engineers could solve that, the Army had to get past a memo from Defense Secretary Charles Wilson limiting it to missiles under 200 miles, a cap lifted in 1958. Army Secretary Wilber Brucker, a former Michigan governor, pushed to give the contract to Chrysler, but General John Medaris and Dr. Arthur Rudolph defended an engineering-based choice, and the Martin Company won. First called Redstone S, the missile was renamed for General John J. Pershing. Martin quality manager Phil Crosby applied a zero defects standard to a weapon carrying the W50 warhead, selectable at 60, 200 or 400 kilotons.

To end powered flight on time, the guidance computer fired explosive bolts to release the warhead while charges blew open thrust reversal ports at the front of the second stage, pushing the motor backward. Flight tests showed the empty casing still drafting behind the warhead and bumping it, so engineers added charges to blow a hole in its side. Pershing 1 replaced the Redstone's 20-vehicle convoy with a four-vehicle tracked "land train" that 14 Chinook helicopters could airlift. The 1969 Pershing 1a moved to wheeled tractors and digital computers, and 1976 upgrades let crews launch from unsurveyed sites in minutes.

• Each firing platoon used four M474 tracked vehicles: launcher, warhead carrier, computer and power unit, and a communications vehicle with an inflatable dish antenna.
• A 1961 Pegasus proposal suggested adding a third stage to put a 60-pound payload into orbit from mobile launchers in Europe.
• Pershing 1a battalions grew from 8 launchers to 36 and could use West German highways on Ford M757 tractors.
• The Automatic Reference System used north-seeking gyroscopes to find true north, and a sequential launch adapter let one station fire three missiles.
• After the 1988 INF Treaty, the last motors were static-fired at Texas's Longhorn Army Ammunition Plant in May 1991 and crushed, and West Germany destroyed its own.