NASA had to cancel a test flight of its new moon rocket without a crew because of fuel leaks.
The next attempt to launch will not happen until at least Friday.
On its first flight, the 322-foot-tall Space Launch System rocket was set to take off Monday morning with three test dummies on board. The mission was to send a capsule into orbit around the moon.
When it happens, the shakedown flight will be a big step toward America's goal of putting astronauts on the moon again for the first time since the Apollo program ended 50 years ago.
NASA wants to send four astronauts around the moon in 2024, and it wants to land people on the moon as soon as 2025.
