As part of the Space Launch System (SLS) program, NASA had been running the Advanced Booster Competition, which was scheduled to end with the selection of a winning booster configuration in 2015. In 2012, Pratt & Whitney Rocketdyne (PWR) proposed using a derivative of the F-1 engine in the competition as a liquid rocket booster. In 2013, engineers at the Marshall Space Flight Center began tests with an original F-1, serial number F-6049, which was removed from Apollo 11 due to a glitch. The engine was never used, and for many years it was at the Smithsonian Institution. The tests are designed to refamiliarize NASA with the design and propellants of the F-1 in anticipation of using an evolved version of the engine in future deep-space flight applications.