"We're not looking for just a pilot," says Captain Williams, who retains her commission in the US Navy. "They're up there for six months, and they owe the taxpayers a productive day."
Keeping penned-up astronauts productive also means giving them time for personal pursuits – from playing guitar to watching movies. Cady Coleman, currently serving on the station, packed a flute and wound up playing a duet recently with earthbound flutist Ian Anderson from the rock group Jethro Tull to mark the 50th anniversary of the first human in space (Russian Yuri Gagarin). It conjures up images of a possible new single, "Thick as a Shuttle Brick," that could go on a CD titled "Astrolung."
Beyond the need for a generalist's hands-on skills, astronauts accustomed to shuttle operations face starkly different conditions as they prepare for space-station work. Those differences can weigh heavily in their decision about whether to remain in the corps.
Mike Fossum, a veteran of two shuttle missions since the Columbia tragedy, heads to the ISS in May. He is in a fairly unique position: Over those two shuttle missions he took part in spacewalks that helped assemble the station; now he's going to live in it.