It's the second of two ISS spacewalks this week, 236th in the station's 20-year history

Two pairs of astronauts will replace batteries and cameras as well as install a new communication an

The mission marks the first time NASA has used a commercial rocket on a mission

The mission marks the first time NASA has used a commercial rocket on a mission

Astronauts Bob Behnken and Chris Cassidy floated out of International Space Station on their fourth

Working to finish upgrading the space station's power supply

Spacewalk continues mission begun last week to upgrade ISS batteries