The ASTROBEE D III rocket is a modified version of Aerotech's Astrobee D that included 3 strap-on boosters as well as an electronics compartment in the aft section of the main booster.   The unique strap-on booster system allows the little booster rockets to drop away from the main vehicle during the flight had everything worked properly.  Unfortunately the three strap-on boosters failed to ignite during the lift-off and two of them were later recovered at the crash site several hundred yards away.  The ASTROBEE D III mail rocket was retired after only one flight however the overall configuration of the 1 1/2  stage rocket is considered a success.