Q&A with NASA Administrator Jim Bridenstine (members only)

Two astronauts floated outside the International Space Station early Friday for the first of four planned spacewalks to wrap up a complex multi-year job to replace 48 aging batteries in the lab’s solar power system with 24 more powerful lithium-ion units.

SpaceX founder Elon Musk said that their initial assessment is that there was “an oxygen/fuel leak in the cavity above the ship engine firewall that was large enough to build pressure in excess of the vent capacity.” The company is pursuing a launch in February, assuming the Federal Aviation Administration accepts their mishap investigation report.

The Starlink 17-11 mission included the 475th launch of a flight-proven booster. SpaceX achieved liftoff from pad 4E at Vandenberg Space Force Base at 9:26 p.m. PDT (12:26 a.m. EDT / 0426 UTC).