STS 51F, also known as Challenger (STS 51-F), is a winged orbiter spacecraft launched by NASA on July 29, 1985, from Launch Complex 39A at the Kennedy Space Center using a Space Shuttle launch vehicle. The spacecraft measures 37.3 meters in length and span with a diameter of 23.8 meters. It has a dry mass of 85,615 kilograms and a launch mass of 95,229 kilograms. STS 51F was manufactured by RWI for JSC and serves as a crewed spacecraft equipped with fuel cells and batteries for power. The mission orbiter (OV-099) features a shape described as "Box + 2 Wing + Fin" and is equipped with two OME (AJ10-190) motors for propulsion, along with an RCS system rated at 225.29 units.