This is the Scout D, a low-cost, all-solid fuel, four-stage U.S. launch vehicle for boosting small payloads into low-Earth orbits. This specimen is cutaway on the top to reveal its dual payloads, the Injun V (Explorer 40) and Explorer 39 satellites that were launched in 1968. The satellites shown here were backups of the original satellites.
The first Scout was launched in 1960. The vehicle continued to evolve over the years with upgraded motors. The D model Scout appeared in 1972. The last Scout was launched in 1994. This rocket was donated to the Smithsonian in 1977 by the NASA Wallops Island, Virginia, facility.