<p>Main Hall of the Smithsonian Air and Space Museum in Washington, D.C.  The smaller missile is an inert Pershing II; the taller one is an inert SS-20.  The plane is the Bell XP-59A Airacomet, the first American jet fighter aircraft.  On the floor of the main hall is Gemini IV -- the first space capsule to host a spacewalk by an American astronaut.
</p><p>The tailfin and rear rocket exhaust of a North American X-15 juts into view from the left.
</p><p>The Pershing rockets were solid-fueled, two-stage, medium-range ballistic missiles designed and built by Martin Marietta.  They replaced the Redstone missile (developed in the early 1950s) as the U.S. Army's primary theater-level missile capable of delivering nucear weapons.
</p><p>The Army began studying a replacement for the Redstone in 1956.  It wanted a ballistic missile (one that reached outer space before coming back down to earth) with a range of 580 to 860 miles.
</p><p>The first Pershing was launched on February 25, 1960. The missile was designed to use an erector towed by a tracked truck.  The first launch from an erector occurred in January 1962. The Pershing used two Thiokol solid-propellant engines in each stage.  It was steered by vanes in the rocket exhaust nozzles and fins on the exterior of the missile.  The guidance system was an on-board analog computer and an inertial navigation system.  It carried a single nuclear warhead.
</p><p>Crews needed to set up surveying instruments (theodolites) to make sure the missile was aimed EXACTLY in the right direction, and at the right azimuth.  Launching took just seconds, but the aiming was very time-consuming.
</p><p>In 1964, the Army sought ways to make the Pershing more reliable.  The Pershing IA was the upgraded version.  It was first deployed in May 1969 and all Pershing I missiles were replaced by it by December 1970.  The analog computer was replaced with a digital one, the power plant was replaced with a solid-state one, and a new guidance system installed.  The new guidance system used a laser to determine azimuth and a north-seeking gyroscopic guidance system to guide it during flight.  (This got rid of the need for time-consuming theodolites.)
</p><p>In 1973, the Army began researching a new version of the Pershing.  It actually wanted to use a smaller nuclear warhead, which would allow for surgical nuclear strikes.  Martin Marietta went to work on the missile in 1975 and test launches occurred in 1977.  Unlike previous Pershings, the Pershing II had a maneuveable re-entry vehicle that actively looked at the ground with radar.  An on-board computer compared the radar image with the radar map in its databanks, and guided the re-entry vehicle to its target.  The Pershing II still used the Pershing I rocket engines.
</p><p>While research was going on, the Soviet Union deployed its SS-20 intermediate-range nuclear missile.  The SS-20 had a range of 2,700 miles, so the Pershing II's range was increased to 900 miles.  But this still could not reach Russian soil.  So NATO made its infamous "double-track decision" to deploy the Pershing II as well as the longer range but slower Gryphon ground-launched cruise missile.
</p><p>To give the Pershing II longer ranger, the Pershing I rocket engines were removed and new rocket motors built by Hercules added. Its weight was reduced (giving it more range) by using a Kevlar casing instead of aluminum.
</p><p>The Pershing II used a gyroscopic intertial guidance system and pure physics (a ballistic arc) to get the missile close to its target.  The re-entry vehicle (RV) did the actual work of targeting, however.  The RV used a Goodyear Aerospace active radar guidance system which greatly improved accuracy over the Pershing IA. The Pershing II could deliver a warhead to within 100 feet of the actual target.
</p><p>On December 12, 1979, NATO deployed 108 Pershing IIs and 464 Gryphons in western Europe.  The first Pershing IIs reached West Germany  in late November 1983, and deployment was completed throughout Europe in late 1985.
</p><p>Faced with a horrifically costly new arms race in intermediate- and short-range nuclear missiles, the Soviet Union and United States agreed to withdraw the SS-20 and Pershing II.  The Intermediate-Range Nuclear Forces (INF) Treaty of 1988 governed their withdrawal and destruction.
</p>
The INF Treaty allowed for inert Pershing II missiles to be retained for display purposes.  One is on display in the Smithsonian, and the other is at the Central Armed Forces Museum in Moscow.  (A handful of inert Pershing I and Pershing IA missiles are also displayed in the U.S. and Germany.)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/23165290@N00">Tim Evanson</a> from Cleveland Heights, Ohio, USA
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/timevanson/7271321560/">Pershing II foreground - SS-20 background - Bell XP-59A Airacomet - Smithsonian Air and Space Museum - 2012-05-15</a>