NASA Astronauts Carry Out 300th U.S. Spacewalk

Watch VideoTwo U.S. astronauts completed NASA's 300th spacewalk on Tuesday, venturing outside of the International Space Station some 200 miles above the Earth at around 17,000 miles per hour.

During the 5 1/2-hour excursion, astronauts Chris Cassidy and Robert Behnken performed a variety of maintenance tasks including...