Complex sentence: In the early 1970s, the C-5 was considered for the role of Shuttle Carrier Aircraft to transport the Space Shuttle to Kennedy Space Center by NASA, but rejected in favor of the Boeing 747 due in part to the 747's low-wing design.
Split into simpler sentences: In the early 1970s, NASA considered the C-5 for the Shuttle Carrier Aircraft role, to transport the Space Shuttle to Kennedy Space Center. However, they rejected it in favor of the Boeing 747, in part due to the 747's low-wing design.