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A crowd in the Georgetown neighborhood of Seattle watches NASA's Super Guppy aircraft approach Boeing Field, carrying a key piece of a space shuttle mockup that will go on display at Seattle's Museum of Flight.

By Alan Boyle

SEATTLE — It may not be a real space shuttle, but it's ours.

Today NASA delivered a key piece of the mockup that astronauts used for space shuttle practice to the Museum of Flight in Seattle, my hometown. And it arrived aboard one of the most ungainly-looking airplanes ever built. The wingless mockup is known as the Full Fuselage Trainer, or FFT. The plane has a nickname that's more colorful: the Super Guppy.

The Super Guppy looks more like a Super Whale. The wide-body turboprop airplane has a cargo hold that's been built up into a bulbous shape, specifically to carry big stuff for outer space. Only five of the Guppies were ever produced, and they were used to cart spacecraft components around for the Gemini, Apollo, Skylab and shuttle programs. This Super Guppy is the only one of its kind still flying, and this week's odyssey with the most important piece of the Full Fuselage Trainer is one of the highest-profile flights the plane has ever taken.

For decades, the plywood-built FFT sat in a building at NASA's Johnson Space Center in Houston. The crew compartment — the part of the structure that was flown to Seattle today — was outfitted with all the buttons, switches, cockpit displays and middeck lockers that the real shuttles had. None of those gadgets worked, but they helped the astronauts get familiar with the layout before they started handling the real controls. Astronauts could also practice how they'd get out of the shuttle in the event of a landing-strip emergency.

With the end of the space shuttle era, NASA's Johnson Space Center no longer needed the FFT, so the space agency decided to donate it for display. The Seattle museum made a play for one of the flown shuttles, and even built a shuttle-sized, 15,500-square-foot Space Gallery to display it in. But Seattle lost out to Florida, California, New York and the "other Washington" in the competition for Atlantis, Endeavour, Enterprise and Discovery. The Full Fuselage Trainer served as the consolation prize.

Most of the FFT's plywood parts could be shipped up by traditional means for later assembly, but the shuttle crew compartment had to be transported all in one piece. That's why NASA's Super Guppy was called into service.

The airplane has a 25-foot-high, 25-foot-wide, 111-foot-long cargo compartment — big enough to hold the mockup's most awkward piece, even when it's bound up in shrink wrap and a protective steel frame. Over the past couple of days, the Super Guppy has been making a journey from its home at Ellington Air Force Base in Texas, over to California, and then up to Seattle at a top speed of around 200 knots. It wasn't exactly a record-setting pace — but what the Super Guppy lacks in speed, it more than makes up for in the "What the Heck Is That?" department.

The Guppy flew over my hometown and its surroundings with a Seattle-born astronaut, Greg Johnson, at the controls. Then it floated down to a landing right in front of the museum, which is adjacent to Boeing Field. One of the commentators at the museum called it a "beautifully ugly airplane."

Washington Gov. Christine Gregoire pointed to the craft with pride as the sky spit down rain. "When we get together in Washington state, we can land the big whale right behind me," she said.

Museum of Flight

NASA's Super Guppy and a chase plane fly above the mostly cloudy skies of Seattle.

Museum of Flight

After its touchdown at Seattle's Boeing Field, the turboprop-powered Super Guppy taxis over to the Museum of Flight next door.

Museum of Flight

The entire front of the Super Guppy swings open to reveal the cargo inside.

Museum of Flight

The 65,000-pound Tunner 60K aircraft cargo loader and transporter rolls toward the Super Guppy.

Museum of Flight

The cargo compartment for the Full Fuselage Trainer, wrapped in protective plastic, has been taken out of the Super Guppy for a short ride on the Tunner transporter to its new home in the Museum of Flight's Charles Simonyi Space Gallery.

Several thousand onlookers watched as the Super Guppy's entire front opened up to the side like a four-story-high door. 

"It's really cool that it's actually able to fly," Allison Kirkman, a 10-year-old student at Spirit Ridge Elementary School in Bellevue, Wash., told me as she watched from the tarmac. "It's an amazing plane, and how they built it is cool, too."

The shrink-wrapped shuttle crew compartment was moved out of the wide-yawning Super Guppy onto a 65,000-pound mobile transporter, then rolled over to the museum's Charles Simonyi Space Gallery. Over the next couple of months, the shuttle mockup will be assembled in a place of honor, alongside a Russian Soyuz capsule and a prototype lander that was used in Blue Origin's spacecraft development program. Museumgoers like Kirkman will be able to walk through the shuttle mockup's cargo bay — and they might even be able to crawl through the crew compartment, just like the astronauts did.

Kids, prepare to be amazed ... again.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.