This is the Nike-Ajax booster for the Nike-Cajun, a two-stage, solid-fuel sounding or upper-atmospheric research rocket. It could carry 10-100 pounds of scientific instruments up to 100 miles altitute for experiments like analyzing the composition of the upper atmosphere or obtaining data on radiation, weather, and solar phenomena.
The Nike-Cajun used a standard Nike-Ajax missile booster as the first stage and a Cajun as the second stage. It was one of the most widely used sounding rockets. Operational in 1956, they saw service during the International Geophysicial Year of 1957-1958. This object was donated to the Smithsonian in 1958 by the National Advisory Committee for Aeronautics (NACA).
This object is on display in Rockets & Missiles at the Steven F. Udvar-Hazy Center in Chantilly, VA.