Nothing, says Mark Geyer, program manager for the fledgling Orion spacecraft development project, was easy about building the next-generation space transportation system planned to take astronauts -- and others -- into the deep reaches of space. "The pressure vessel, the heat shield, parachute system, avionics -- piecing all of that together into a working spacecraft is an accomplishment. Seeing it fly in three months is going to be amazing."

The National Aeronautics and Space Administration reports steady progress in preparation for Orion's inaugural test space flight in December, according to an agency news release.

After they finished building it, engineers attached the craft's crew module to the previously-completed service module, as well as an adapter that will connect Orion to its rocket, and transported the spacecraft to a new facility for fueling -- a 20-minute trip for the so-called module stack, from the Neil Armstrong Operations and Checkout Building at NASA's Kennedy Space Center in Florida to the Payload Hazardous Servicing Facility.

The move -- which you can see in a sped-up YouTube video at the bottom of this story -- took place Sept. 11.

Finishing the Orion crew module marks the completion of all major components of the spacecraft, Geyer said in the release.

The spacecraft's two other major elements -- the inert service module and the launch abort system -- were completed in January and December respectively.

The adapter, constructed by NASA's Marshall Space Flight Center in Huntsville, Alabama, will connect the Orion modules to the United Launch Alliance Delta IV Heavy rocket is currently undergoing testing for use with NASA's Space Launch System, the largest rocket ever developed, for future missions to deep space.

Having reached the servicing facility, Orion will now be fueled with ammonia and hyper-propellants for its upcoming flight test.

Then, the craft's launch abort system will be attached, after the fueling is complete, and then positioned atop the Delta IV Heavy rocket selected for the launch.

"Built to send humans farther than ever before, including to an asteroid and Mars ... Orion will provide living quarters for up to 21 days, while longer missions will incorporate an additional habitat to provide extra space," said a NASA statement. "Many of Orion's critical safety systems will be evaluated during December's mission, designated Exploration Flight Test-1, when the spacecraft travels about 3,600 miles into space."