NASA ran into a leak while fueling its new moon rocket Monday in one final make-or-break test that will determine when astronauts can launch on a lunar fly-around.

The launch team began loading the 322-foot (98-meter) rocket with super-cold hydrogen and oxygen at Kennedy Space Center at midday. More than 700,000 gallons (2.6 million liters) had to flow into the tanks and remain on board for several hours, mimicking the final stages of an actual countdown.

But just a couple hours into the daylong operation, excessive hydrogen was detected near the bottom of the rocket. Hydrogen loading was temporarily halted, with just half of the core stage filled.

The launch team scrambled to work around the problem using techniques developed during the only other Space Launch System rocket launch three years ago. That first test flight was plagued by hydrogen leaks before finally soaring.

The crew, three Americans and one Canadian, monitored the critical dress rehearsal from nearly 1,000 miles (1,600 kilometers) away in Houston, home to Johnson Space Center. They have been in quarantine for the past 1.5 weeks, awaiting the practice countdown's outcome.

The all-day operation will determine when they can blast off on the first lunar voyage by a crew in more than half a century.

Source:Ndtv