As Discovery prepares for her last space shuttle launch, NASA's human spaceflight program shifts from space station ferry-service to missions to the moon, Mars, and beyond.
Joe Skipper / Reuters
After 27 years and more than 143 million miles, the space shuttle Discovery is poised for her final countdown.
The ship is carrying an Italian-built cargo carrier re-engineered to provide extra storage space on the International Space Station. In addition, the orbiter is lofting some 5 tons of supplies and Robonaut 2, which designers envision as an eventual humanoid helpmate for future space-station crews.
Discovery's launch marks the first of three curtain calls – one for each of the remaining vessels in the shuttle fleet – as NASA's human spaceflight program enters a period of profound transition.
NASA is handing off the responsibility of ferrying goods and US astronauts to and from the station to private launch companies.