Tom Durkin

NASA

This morning’s scheduled launch of NASA’s next generation Orion spacecraft was scrapped, but officials will try again Friday.  No one will be aboard when it launches, but Orion is designed to take astronauts into deep space, including Mars. NASA wants to test the most risky systems before flying with a crew.

The last time a spacecraft designed for human travel left Low Earth Orbit was the 1972 Apollo 17 mission, which was also the last time astronauts walked on the moon.