Mostly, they loom. My entire conversation with the engineer occurs in this brittle space of carefully monitored availability, a tape recorder wielded by the press escort waggling in the air between us whenever one of us opens our mouth.

So when we get outside in the fresh air and the gaggle of officials moves off to the railing, I immediately start talking to the chef. Soon we are touching upon slow-cooked pork barbecue, and I feel like I have been temporarily beamed back to planet Earth. Of course, the chef can't cook real BBQ here on board -- all he's got is this standard grill, the kind you might buy at Lowe's.

The primary fascination the backyard grill has for me is, simply, that it exists. Like most Americans, I have been stuck with this sense that missile defense -- Ronald Reagan's dream of a security dome armed with an array of rockets and lasers and space-age interceptors that could shoot down any incoming missile launched by the Evil Empire -- is still mostly theory, blue-sky notions doodled on a whiteboard somewhere, nothing more than a gnarly policy dispute on the Sunday-morning talk shows. I had no real idea just how real, hardware real, the entire thing has gotten.

America's missile defense shield is, in a manner o speaking, up and running. One of the little-heralded achievements of the Bush administration was his order in 2002 that instructed the Defense Department to quit wasting so much time testing the shield to see if it will actually work and just deploy the damn thing already. The SBX is the part of the syste that, according to its designers, will pinpoint an incoming ICBM's trajectory and direct into its flight path high-speed interceptor missiles, which also exist and are now on standby in silos in Alaska and California.

Last summer, when the North Koreans fired some missiles, America turned the shield on. Th system is a go. The interceptor silos in Alaska are manned by a permanent National Guard unit. Type "missile defense" into hotjobs.yahoo.com to apply for one of the 187 jobs currently open. The SBX has two full crews that roll into work every few weeks on staggered rotations. They've moved into their quarters and put their socks in the bureau drawers. They have a well-equipped gym, and word just got out that a flat-screen TV is on the way. They're at home on board, comfortable here.

This is my point. The missile defense shield has a backyard grill.