sentences:  The plan is for a series of multiple launches to send various space transpiration, surface exploration hardware, and human crew to Mars, and to return the crew to Earth in the early 21st century.Various technologies are explored to launch the payloads into space, to send them to Mars, and to reduce overall weight of the mission by various technologies or techniques including nuclear, solar, aerobraking, and in-situ resource use
  
  The study was performed by the NASA Mars Exploration Team at the NASA's Johnson Space Center (JSC) in the 1990s.Personnel representing several NASA field centers formulated a "Reference Mission" addressing human exploration of Mars.