The historic launch of Orion, NASA's much-heralded, next-generation spacecraft, was scrubbed Thursday because of faulty valves.

The decision came after repeated delays caused by strong winds and even an errant boat that appeared to move too close to the launch site.

Up until the final minutes before the close of the launch window, NASA officials held out hopes of testing the craft designed to ultimately bring humans to Mars.

But after a tense morning, several fuel and drain valves that did not function properly finally forced officials to postpone the mission. The next launch window is Friday at 7:05 a.m. But officials said there was only a "40 percent chance of favorable weather conditions" for a launch.

The uncrewed spacecraft had been scheduled to lift off at 7:05 a.m. Thursday from Cape Canaveral, Fla., aboard a Delta IV Heavy rocket, en route to a 41/2-hour flight that would take it twice around Earth and to an altitude of 3,600 miles - farther than any spacecraft designed for humans has traveled in more than 40 years.

As the morning unfolded, a NASA official had said on the agency's live Web stream that there have been a "number of minor issues," but no "show stoppers." At one point, the official said Orion "stands ready for launch" as crews waited for the wind to die down.

In a statement, the United Launch Alliance (ULA), the joint venture between Lockheed Martin and Boeing that makes the Delta IV rocket, said that while "the liquid hydrogen fill and drain valves . . . did not properly close within the allotted time," the spacecraft "has no technical or operational issues and remains ready for launch."

Daniel Collins, ULA's chief operating officer, told reporters Thursday afternoon that the valves "had gotten cold and a little sluggish in their performance."

He said that the team was "listening to everything the rocket was telling us. And it told us it wasn't ready to go today. So we'll go make sure we have a happy rocket. And as soon as we do that we're going to get back to the pad and send Orion off for a very successful test flight."