Visiting a museum full of airplanes and rocket ships is a pretty awesome field trip. Now imagine camping out for a whole night in Smithsonian’s huge hangar outside Washington, D.C. You’re there with a few other lucky kids, some grownups, and aviation treasures like the space shuttle Discovery.

Sean Mclaughlin, 10, is one of those kids. He’s picking out his pilot code name — using the aviation alphabet: Alfa, Bravo, Charlie, Delta, Echo, Foxtrot. He reads each word aloud, sitting just to the side of a F8U Crusader — the first carrier-based jet fighter to exceed 1,000 miles per hour.

Sean finally settles on the perfect code name: Alpha Whiskey Yankee — the first step in his on boarding as a young pilot on this sleepover adventure at the Smithsonian’s massive Udvar-Hazy Center.

This was the first year the Smithsonian offered sleepovers at the center, also called the Smithsonian National Air and Space Museum’s annex near the runways of Washington Dulles International Airport. The cost? $135 if you’re not a museum member. Even though it was just about sold out this year, there are plans in the works for next summer.

In a building the size of three football fields — full of airplanes, parachutes, helicopters and space capsules — there’s plenty of room for activities.

The kids arrived early in the evening, once all the tourists had gone, and quickly spread out over the giant space on an all-night scavenger hunt and quiz. Stops along the way included: making helicopters and learning to wave a jetliner safely into the gate.

In the wing of the museum devoted to space exploration, I find Soraya Okely, 8. She says she’d like to be an astronaut some day.

“The things that I’ve done so far: Do all these quizzes,” Soraya explains. “I’ve worn the space gloves. It’s awkward and hard, but it’s also fun because after you de-construct a plane you get astronaut ice cream!”

She’d like to go to Mars one day and this sleepover, she says, is good training. And that’s kind of the point: There are volunteers throughout the museum offering tips and facts.

Volunteer Harold “Woody” Davis greets kids as they shuffle towards the glass case of items astronauts took into space. There’s a package that a group of boys claim is vomit — but it turns out it’s just chicken and gravy.

“What would you take to space?” asks Woody. “Would you take borscht? Would you take makeup? Pizza?

Sean Mclaughlin — aka Alpha Whiskey Yankee — says pizza for sure. Or maybe French fries. He lives in Virginia not too far from the museum, and he comes here all the time. But tonight, he says, is special because he can take his time and read every detail, soaking it in.

“It’s pretty cool when you’ve got the place all to yourself,” he says. ” ‘Cause no one else is here. Usually, when you come it’s really loud and there’s lots of screaming. I’m like, ‘I can’t read this!’ ”

The other magical things about tonight? You can fall asleep next to fighter planes from World War II.

Bed Time

As 11 p.m. approaches, kids and parents are getting tired. You can feel the energy level dropping.

The adults urge the younger ones to change their clothes and brush their teeth. It’s a familiar routine — the only hitch is the automatic faucets in the industrial bathroom, which make it a bit hard to brush your teeth and wash your face.

All the children must be accompanied by an adult. These chaperones are setting up the sleeping sleeping bags, air mattresses, cots. One dad even set up a free-standing hammock.

Soraya Okely changes into her space-themed PJs, printed with Saturn, the moon and the Big Dipper.

Soraya says that when she’s falling asleep, she might say good night to all the space ships: “I hope I venture in you one day.”

I ask her what she expects to see when she opens her eyes in the morning. “I’m gonna feel like I’m in my house,” she says, “but it’s been extended with spaceships.”

Finally, everyone is zipped in for the night: pillows fluffed and stuffed animals tucked in — all in the shadow of the space shuttle’s wing.

As the museum lights go dark — these spaceships dip into the dreams of the little discoverers.

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