KENNEDY SPACE CENTER, Fla. — The spacecraft that serves as a cornerstone of NASA’s long-term human space exploration plans carried out nearly flawlessly a brief but critical first flight test Dec. 5.

A United Launch Alliance Delta 4 Heavy lifted off at 7:05 a.m. Dec. 5 from Space Launch Complex 37 at Cape Canaveral Air Force Station, at the beginning of a two-hour, 39-minute launch window. The rocket placed the Orion spacecraft into a transfer orbit of 185 by 888 kilometers about 17 minutes and 30 seconds after liftoff.

At 9 a.m., after completing one orbit, the Delta 4’s upper stage fired its engine again, placing the spacecraft into a highly elliptical orbit. Orion achieved a peak altitude of 5,800.4 kilometers at 10:11 a.m., as planned.

Orion splashed down in the Pacific Ocean 1,015 kilometers southwest of San Diego at 11:29 a.m. The capsule landed within a few kilometers of its planned location, where two U.S. Navy vessels were positioned to recover the capsule.

During the nearly four-and-a-half-hour mission, officially known as Exploration Flight Test (EFT)-1, flight controllers reported no problems with the spacecraft. “Every single system on this spacecraft functioned by the book from start to finish,” NASA spokesman Rob Navias said shortly after splashdown.

There was at least one problem with the system that inflates five airbags to keep the module upright after splashdown. Only three of those airbags inflated fully, but NASA suggested that was a relatively minor problem. “We didn’t see anything major, that’s clear,” said Mark Geyer, NASA Orion program manager, said at a post-splashdown briefing.

Orion was to be brought onboard the USS Anchorage, the primary recovery ship, which was then to return to San Diego. After arriving there, Orion will be trucked back to the Kennedy Space Center, returning here by Christmas.

NASA originally planned to launch Orion on Dec. 4, but that attempt suffered both weather and technical problems. The countdown was stopped twice with less than four minutes before liftoff when winds exceeded preset limits.

A third launch attempt, about halfway into the two-hour, 39-minute launch window, was also halted with just over three minutes before launch. Liquid hydrogen valves on two of the three booster cores that comprise the Delta 4 Heavy’s first stage failed to close, and the problem could not be resolved before the launch window closed.

The EFT-1 mission was the first flight test of the Orion spacecraft. NASA designed the mission to test several key systems on Orion, including its heat shield, parachutes, and the susceptibility of the spacecraft’s electronics to radiation as Orion passed through the lower portions of the Van Allen belts.

“It’s a test flight,” Geyer said during a pre-launch briefing here Dec. 3. “We are pushing the systems to make sure they work as we expect.”

Those tests will support further development of Orion, which is now expected to fly again in 2018 on the first launch of the Space Launch System heavy-lift rocket. That will be followed by first crewed Orion launch, also on the SLS, in 2021.

Development of both Orion and SLS will be the subject of a hearing by the House Science Committee’s space subcommittee Dec. 10. Rep. Lamar Smith (R-Texas), chairman of the full committee, mentioned the importance of keeping both programs on schedule in a statement issued shortly after the Orion splashdown.

“The Orion launch is a major milestone for U.S. space exploration and our efforts to travel further into our solar system than ever before,” said Smith. “That is why I place the highest priority on ensuring NASA remains on budget and on schedule with the Space Launch System.”