• NASA’s latest attempt to fuel its huge moon rocket for a countdown test was thwarted on April 14 by a hazardous hydrogen leak, the latest in a series of vexing equipment trouble.
  • This was NASA’s third shot at a dress rehearsal, a required step ahead of a test flight to the moon.
  • Two previous countdown attempts were marred by balky fans and a large hand-operated valve that workers mistakenly left closed at the pad last week.