Why the doubt? Motivation and money, say Bean and Cernan. Without the pressure of imminent international challenge, the astronauts say, the Constellation program — NASA’s next manned mission to the moon in 2020 — will lag. “We need some kind of stimulus, a commercial or international challenge to our standing in the free world,” says Cernan, 74.
http://www.time.com/time/specials/2007/article/0,28804,1723210_1723212_1737771,00.html