Before the Project Apollo Moon landing in 1969, NASA began studies of Space Shuttle designs as early as October 1968. The early studies were denoted "Phase A", and in June 1970, "Phase B", which were more detailed and specific. The primary intended use of the Space Shuttle was supporting the future space station, ferrying a minimum crew of four and about 20,000 pounds (9,100 kg) of cargo, and able to be rapidly turned around for future flights.