The is an 8AS-200 JATO (Jet-Assisted-Take-Off) rocket motor, developed and built by the Aerojet Engineering Corporation to help lift light planes or for rescue work. The motor produced 200 pounds of thrust for eight seconds. The 8AS-200 JATO was an early development, dating to late 1942, but was not widely used because of its low thrust and short duration.
It was used from 1942-1943, mainly for tests, and was a precursor to Aerojet's later JATO Junior of 250 pounds thrust for 12 seconds that was much more successful. This model shown here appears to be a production model of of the 8AS-200 of ca. 1947. This object was donated to the Smithsonian in 1948 by the Aerojet Engineering Corp.
This object is on display in Rockets & Missiles at the Steven F. Udvar-Hazy Center in Chantilly, VA.