Polaris Dawn, a private space mission that aims to complete the first-ever civilian spacewalk, is expected to launch this week. SpaceX said it’s targeting Tuesday August 27 at 3:38AM ET for liftoff.

Four astronauts are ready to spend five days in orbit on a mission that includes the first attempted spacewalk by private astronauts.

The first mission of the Polaris Program, called Polaris Dawn, is expected to launch on Monday following weeks of delays. Some of them were weather-related; since the craft will not dock with a space station,