NASA's new moon rocket sits on Launch Pad 39-B hours ahead of a planned launch at the Kennedy Space Center Saturday, Sept. 3, 2022, in Cape Canaveral, Fla. NASA's new moon rocket sprang another hazardous leak Saturday, as the launch team began fueling it for liftoff on a test flight that must go well before astronauts climb aboard. Credit: Joel Kowsky / NASA via AP

CAPE CANAVERAL, Fla. — NASA’s new moon rocket sprang another dangerous fuel leak Saturday, forcing launch controllers to call off their second attempt to send a crew capsule into lunar orbit with test dummies.

The first attempt earlier in the week was also marred by escaping hydrogen, but those leaks were elsewhere on the 322-foot rocket, the most powerful ever built by NASA.

Launch director Charlie Blackwell-Thompson and her team tried to plug Saturday’s leak the way they did the last time: stopping and restarting the flow of super-cold liquid hydrogen in hopes of removing the gap around a seal in the supply line. They tried that twice, in fact, and also flushed helium through the line. But the leak persisted.

Blackwell-Thompson finally halted the countdown after three to four hours of futile effort.