The sign accompanying the Jupiter-C mockup. It reads
Geophysical Year was observed from July 1957 to December 1958. Its
scientific program included a proposal to launch satellites that would measure
Earth from space. Russia orbited Sputnik on
October 4, 1957, and four months later the United States launched
Explorer I aboard a Jupiter-C launch vehicle.
On January 31, 1958, a rocket configured as the one you see here was launched
from Cape Canaveral, Florida, by the U.S. Army. On top was the first U.S.
satellite. Its mission was to explore the unknown.
Using a small, but effective, package of instruments, this 31-pound sphere
returned data that produced the first major discovery in space ... the Van
Allen radiation belts. It also fulfilled America's commitment to the
International Geophysical Year.
Jupiter-C consists of a liquid-fueled first stage and three solid-fueled
stages. At liftoff, it developed 78,000 pounds of thrust. The first stage, as
the Mercury-Redstone, was also used in America's suborbital manned missions.
As you see it here, the rocket stands 68.5 feet tall.
Of course, the launch vehicle for the Explorer I satellite was
the similar Juno I launch
vehicle; the Juno I had three upper stages, while the Jupiter-C had only two.
Both launch vehicles used modified Redstone first stages, as did the
Mercury-Redstone, but the Jupiter-C/Juno I first stage differed in a number of
respect from the Mercury-Redstone.
And Explorer I was a cylinder, rather than a sphere.