IN A TOWN that pays so much attention to air and space, you'd expect to find a corps of aviation enthusiasts. And you'd be right. There are people like Chris Gama from Gaithersburg, who collects space patches -- more than 300, so far. He got his first on a trip to Cape Canaveral as a kid, when "some guy with a Russian accent asked me if I wanted a patch. I had no idea how valuable it was," he says of that cosmonaut patch.

Gama, now 36, has "friends in NASA" who send him patches from each manned mission, but he says anyone can start a good collection simply by going to the gift shop at the Goddard Space Flight Center in Greenbelt.

Then there's David Blair, a man of 32 with more than 200 aviation stamps, most of them first-day covers. "I'm a real groupie," says Blair, who wangles invitations to NASA press conferences, and plans to spend his summer vacation at the space camp in Huntsville, Alabama

The camp, sponsored by an Alabama museum, chiefly caters to kids completing sixth, seventh and eighth grades whose science teachers recommend them. They learn to walk without gravity, go through part of the astronaut training and conduct simulated space shuttle missions. The camp costs $350 for a one-week session; sessions run from March to mid-November. (For information, write the U.S. Space Camp, The Space & Rocket Center, Tranquility Base, Huntsville, AL 35807. Phone 205/837-3400.)

While relatively few can afford or qualify for the space camp, thousands of elementary and junior high kids nationwide are getting involved in the Young Astronaut Program, a corporate- sponsored endeavor that helps youngsters study math and science through the "excitement of the space program," says a spokesman. Chapters, which receive curriculum and project guidance, are usually formed in schools, though church and youth organizations are also signing on, says the spokesman. It costs $20 per chapter. (For information, write P.O. Box 65432, Washington, DC 20036, or call 682-1985.)

There's no "Old Astronauts" group for adults, but many aviation groupies in this area do gather in, well, groups like the Washington Airline Society. They discuss "airlines every month, believe it or not," says member Bill Roy. "Hey, I don't drink, I don't do drugs -- I talk airlines," he explains.

The club meets monthly at the Air & Space Museum, says member Ron Davies, who also serves as curator of air transport there. "These are people who are wonderful at airline trivia," he says, including himself, "and some of them do models." That's scale models -- the kind the Smithsonian likes to put on display. (For information, call Davies at work, 357- 2515, or Roger Bentley at home, 593-2242.)

Finally, hardcore aeronautic types indulge their fantasies by visiting the Nostalgic Aviator, at 1215 King Street in Alexandria. It started as a place to get out-of-print aviation books. Now the store (684-5118) has things like old kits, parts of wings, propellers and old lithographs to tickle a pilot's fancy.