NASA has begun another practice launch countdown for its first moonshot in decades with astronauts. The first test was halted two weeks ago by dangerous hydrogen fuel leaks, bumping the flight from February into March. Launch teams replaced a pair of seals and a clogged filter at the Florida pad where the giant moon rocket stands, then started the countdown clocks Tuesday evening. The two-day test will culminate Thursday with the attempted fill-up of the rocket's fuel tanks. The mission's four astronauts will monitor the dress rehearsal from afar. A successful, leak-free test is needed before NASA will set a launch date.
