Sitting there in his Crystal City hotel room, his gentle bulkiness strapped in by blue suspenders, is the man who made "Star Trek": Gene Roddenberry. The man who gave birth to the USS Enterprise, Kirk, Spock, and a TV five-year mission that became syndicated eternity. Some 18 floors beneath him a flood of Trekkies is beaming from room to room to see fanzines, books, badges, old shows, plus other Star Trekia at the 17th annual "Star Trek" convention. Roddenberry, who looks more like your friendly fireman than the father of a pop culture, will address the fans in a bit, but for now he has a little time to remember the show's origins.

"I don't enjoy conventions," says the writer/producer, former Los Angeles cop and Pan-Am pilot. "I'm not an actor. But I like to see what's happening and stay in touch . . . You can't be a writer in a hidden garret."

It wasn't Isaac Asimov or "The Day the Earth Stood Still" that sparked the "Star Trek" idea, he says, so much as Jonathan Swift.

"When Swift wanted to comment on his time, crooked prime ministers and insane kings and queens and all the things in his time, he would have gotten his head chopped off for it if he'd written straight . . . So in "Star Trek" I did much the same thing. I talked about things you couldn't talk about . . . sex, religion, union management, labor, all that stuff . . . "

The demented monarchs, in Roddenberry's case, were the TV network executives. Roddenberry had been head writer for "Have Gun, Will Travel," and had written shows for "Dragnet," as well as New York-based live TV programs, such as "The Kaiser Aluminum Hour" and "Playhouse 90." And he wanted out.

"As TV became more powerful, they censored it more and more," says Roddenberry. "You couldn't mention gas ovens because it might make people think of Nazis. Your character couldn't order a Porterhouse steak because they were afraid the veal advertisers, the pork lobby, would get you . . . They would actually come in with a ruler and measure the cleavage on a woman's breast. I said, 'I gotta get out of this or I'll go crazy' . . . "

So he wrote a TV pilot about a space crew, which he presented to NBC in 1965, with some bold components. Among other things, it had a female second in command (this was the '60s, remember) and a half-breed human/Vulcan officer with pointed ears. It was rejected for being too cerebral, says Roddenberry.

" 'Get rid of her, the audience won't believe that,' they said. 'And the guy with the pointy ears, get rid of him.' "

But an NBC executive told Roddenberry the show was the first he had ever seen to convey the feeling of being in a spaceship. So Roddenberry was given more dollars to develop a second episode. He jettisoned the woman and put her computer-like brain into the Vulcan officer and then brought the Vulcan up to No. 2 status as the character Spock. He brought in actors William Shatner, DeForest Kelley, Jimmy Doohan and Nichelle Nichols. The rest is pop-culture avalanche.

After NBC accepted the show in 1966, it ceremoniously dumped it in 1969. But, thanks to the letter-writing clout of the fans the show had already accumulated, "Star Trek" has run nonstop in syndication for 16 years, on more than 150 American stations and in more than 50 foreign countries. There have been three multimillion-dollar "Star Trek" films, and a fourth is due to start production this December.

"Treating the TV audience like an intelligent species pays off," says Roddenberry. "The marvelous thing is I talked about all these things that you couldn't talk about. It went right over the networks' heads. But all the 14- and 16-year-olds in the audience knew exactly what I was talking about."

Fans can line themselves up behind at least two subdivisions: Trekkers and Trekkies. The former, a more serious species of devotee, tend to look down their noses at the latter, who are considered shallow because they wear "Star Trek" costumes and tend to get overexcited at conventions. At this year's convention, however, there seem to be few of the Trekkie order, although some have T-shirts that say "Beam Me Up Scotty, There's No Intelligent Life Down Here."

"You get some who wear Captain Kirk suits," says Roddenberry, "who jump up and down and scream. But at conventions like these you'll also meet prominent surgeons and schoolteachers . . . Some are absolutely brilliant computer wizards and some, fine artists. A dozen of them have become well-known writers, artists and photographers."

At an unnamed midwestern university, the distinguished head of the sociology department was to introduce Roddenberry before a lecture: "So at 8 o'clock, this gentleman, gray-haired, comes out wearing a Captain Kirk suit. I did not know how to relate to him."

The allure of the show, as anyone worth his Trekker salt will tell you, is not the hardware. It's the show's characters and optimistic ideas that count. Roddenberry has created a space Round Table of knights with a noble mission: to preach democratic, multiracial enlightenment to whichever aliens decide to invade their ship, from space traveling Vikings to Klingons.

No doubt, you know those knights: Capt. Kirk, the stalwart commander, who uses more pauses in his speeches than 50 Richard Burtons ("Spock . . . you . . . have not . . . changed"); Spock, the Vulcan-human, who battles to keep his emotions under wraps and strives for what is logical; Bones, the doctor, whose five-year mission is to tell Spock he's just a machine without emotion; Scotty, the engineer, who tells the captain every week the ship's engine can no longer take the strain of all the asteroid buffeting; Lt. Uhura, the first black woman officer in TV space; Chekov, the Russian; and Mr. Sulu, the Oriental, help complete this Utopian work crew.

Down on Earth, Roddenberry is reflecting the same insoluble optimism, like some liberal Herman Kahn, as he talks about today's Earth of clashing ideologies and Pershing IIs. "I think Utopia is Right Now," he says. "Right now, things are absolutely going the way they should go. It's a marvelous game out there, with riches to win and traps to catch you. And terrible pain and torture and enormous rewards. If you could invent a game like August 1985 Earth, you could sell it for millions of dollars for the sheer excitement of it.

"We're living in a science fiction world. The computer, more and more, will change our lives . . . Within 20 years, if humans are intelligent, there won't be any pockets of ignorance. Because of satellites and computers, bushmen in Australia can take college courses. If anything, because of the science fiction world we live in, the world will be simpler and simpler."

It's the same theme he uses for the cheering, applauding Trek-persons who rise to their feet when he enters the ballroom to speak. They are the children of the future, after all.

"There's much more evidence of good news than bad," he tells the audience, a variety of old and young, male and female. "There is a positive human future . . . if we can be mature enough to make it into the next century and into the challenge and happiness of the solar system that is our own back yard.

"It's time to master our own solar system."

But you can only preach for so long, even to intelligent TV people. After the call for public space flight and peaceful positivism, Roddenberry brings on two film reels full of "Star Trek" bloopers, to the obvious delight of the audience. In the films, crew members walk into automatic sliding doors that don't open. The normally laconic Spock hams for the camera. Kirk cannot keep from laughing during a dramatic moment. Scotty stumbles like Jerry Lewis on the steps of a dungeon . . .

Then it's time for the cre me de la cre me. Roddenberry shows the original pilot for the series and makes their day. Yes, he tells them all later, there will be a "Star Trek IV." Roddenberry is at work as executive consultant on the project and is "waiting for the final script, which I expect next week." All the main actors will be in the movie and Leonard Nimoy (Spock) will direct the film. ("They are professional actors in a professional medium. They're not going to turn down the salaries they will get for this," he has said previously in the hotel room.)

The importance of "Star Trek," says Roddenberry, is "you can't be a citizen of the universe without being a citizen of the world. You can't be on friendly terms with Vulcans and also divide the world up. Our crew is made up of all colors. Our viewers are not interested in colors so much as life forms."