 Thruster problems on Boeing's Starliner spacecraft is why two astronauts are at the International Space Station three weeks longer than planned. Butch Wilmore and Sonny Williams say they will return home once thruster testing on Earth is completed. CBS News space consultant Bill Harwood. You have to keep in mind that this is the first piloted flight of the Starliner. They've never had it up with people during a full-up mission. And so they're really kind of trying to wring it out. They think the thrusters will actually work fine.