NASA hasn't built a human-rated spacecraft since 1991, when Endeavour left the factory. But this week, workers at NASA's Michoud Assembly Facility in New Orleans made the first weld on the first space-bound Orion Multi-Purpose Crew Vehicle.

This is a big deal. It's a major step towards accomplishing some of the ambitious exploration goals that President Obama and Congress have laid out for the United States. There are Orion MPCV mockups at Johnson Space Center in Houston, for training and design purposes, but this is the first one actually meant for more than earth-bound testing. This MPCV will fly in space.

Once the welding is complete, the capsule will be shipped to Kennedy Space Center in Florida, where its heat shield will be installed. It'll then get finishing touches and be checked out for spaceflight.

Orion is meant to replace the now-retired Space Shuttle program. It can carry a crew of up to six people and is meant for exploration beyond low-earth orbit. That is to say, it can go farther than the International Space Station. The MPCV will be launched atop a heavy-lift rocket (think Apollo) and return to earth blunt-end down to splash down in an ocean, instead of landing like an airplane.

For more on the MPCV, head on over to NASA's site.