This concept model depicts an alternative arrangement of the space shuttle's main engines. The three engines arranged in a row would be attached to the external fuel tank while firing and then be raised and stowed in the aft section of the orbiter after ascent was completed. This arrangement put the main engines close to the same level as the solid rocket boosters on each side and kept propellants and their plumbing out of the orbiter. In the final design the three main engines were clustered in a triangle in the aft end of the orbiter, and propellants were routed into the orbiter to feed the engines. NASA transferred various concept models to the Museum after settling on the final space shuttle design.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.