Watch live! SpaceX to launch Polaris Dawn spacewalk mission

SpaceX is about to launch four private astronauts farther than any human has flown since the end of the Apollo era. The crew will be on a mission to perform history's first commercial spacewalk. The mission, Polaris Dawn, will liftoff early Tuesday (Sept. 10) during a four-hour launch window that opens at at 3:38 a.m. ET (0738 GMT). Two additional launch opportunities are available within the four-hour window; one at 5:23 a.m. ET (0923 GMT) and another at 7:09 a.m. ET (1109 GMT). Backup launch opportunities are available on Wednesday (Sept. 11) at the same times, according to SpaceX.