Video: Russian cargo ship spinning

Space station commander Peggy Whitson and astronaut Jack Fischer are set for a two-and-a-half hour spacewalk Tuesday, a quickly-planned excursion to replace a recently installed external computer that failed Saturday.

After a two-day readiness review, NASA managers gave a green light Friday for SpaceX to proceed with final preparations for launch next Wednesday, May 27, of a commercial spaceship carrying astronauts Doug Hurley and Bob Behnken to the International Space Station on the first orbital spaceflight from U.S. soil since 2011.

NASA has signed a $490 million agreement with the Russian government to ferry U.S. astronauts to and from the International Space Station in 2018 and 2019 as a hedge in case of delays to Boeing and SpaceX crew capsules.