The SpaceX Polaris Dawn mission crew began the first-ever commercial space walk early Thursday.

Two crew members -- commander Jared Isaacman and mission specialist Sarah Gillis -- were expected to exit the Dragon spacecraft on the "extravehicular activity," as SpaceX described it. Pilot Scott Poteet and mission specialist Anna Menon planned to stay inside the capsule to support the operation.

All crew members are now considered "spacewalkers" as the capsule was depressurized for the outing, thus exposing all four crew to the vacuum of space.

The mission plan said Isaacman and Gillis would both leave the capsule for 10 minutes each. The astronauts will hold a handrail system -- called Skywalker and are on 8-foot tethers -- significantly shorter than NASA spacewalkers have traditionally used.

Isaacman and Gillis plan to "perform a series of mobility tests in the newly-designed SpaceX EVA suit" during the spacewalk, SpaceX said on its website, where the operation was live streamed.

The entire spacewalk is expected to take around two hours, SpaceX said.

ABC News' Gina Sunseri contributed to this report.