The make-believe exploits of Star Trek's Capt. James Kirk don't stand a chance against the real-life heroism of the engineering officer, Lt. Comdr. Scott.

Scotty, as he is known to millions, is the only member of the USS Enterprise crew with any actual combat experience, and now that the starship is making its greatest voyage in a $25-million film, Scotty will be able to notch a few more battlefield experiences.

At 59, Scotty shows so little sign of aging that the ship's Dr. McCoy wants to get him in for a complete physical.

But it's a harder task than McCoy imagined. Scotty keeps slipping on and off ship through time warps. He usually is an actor named James Doohan living with his wife, Carol, their two childen, a couple of dogs and a cat in a ranch-style home in 20th-centruy Los Angeles.

Even with all this traveling he shows no signs of aging. "I've been married three times," he said, "and I'm on my second family. I've got a 3-year-old son and a 9-month-old son who take up most of my time in this dimension."

And few people in the far reaches of space patrolled by the Enterprise know of Scotty's World War II record, or that he is old enough to have two children and four grandchildren by his first marriage.

"I must admit, I'm not Scottish at all. I'm really an Irish-Canadian from Vancouver. Even though I have been living in American since the war, I still hold Canadian citizenship.

"And it was partly because of that citizenship and my feeling toward Britain that I enlisted in the army when Britain declared war. I remember I signed up Sept. 3, 1939."

In the six years that followed, Doohhan rose to be a commander post officer in the artillery. He went ashore in the first wave at Juno Beach in Normandy, was hit by eight bullets from a German machine-gun burst and eventually wound up an artillery observation pilot for the Royal Canadian Air Force.

"Luckily, the bullet that hit my chest never got to me. It was stopped by a silver case I got for my brother's wedding." He did lose his right middle finger, something that no one has detected in all the years Scotty has been working with the complex circuitry of the Enterprise.

"I landed in Britain two weeks before Dunkirk and was stationed there for the duration of the war, so I gained quite a feeling and love for the country. That's where I learned how to speak with a Scottish accent."

In fact, Scotty, or Doohan, can speak with almost any accent in the English language. He was able to practice and polish this ability in 4,000 radio drama episodes with the Canadian Broadcasting Corp. after the war.

"Recently, however, I played a very proper English barrister in a play called "The Trial of James McNeill Whistler.' I have a good ear for accents.

"But, I must admit, if they would let me I would transform Scotty into a Cornishman . . . I like the West County accent the best. It's the most noncommercial. You don't hear it that much."

"Star Trek" has been a mixed blessing for Doohan. It has given him international fame on a TV series that has become a classic even though it played only three seasons and was canceled in 1969.

On the other hand, as an actor with firm roots in Hollywood, he is doomed to be the world's greatest Trekkie. As he says. "Hollywood has decided I'm a Scottish character actor, even though I'm not Scottish. And there is no sense in even talking to them about doing other type movies."

There have been roles in a few films, but ever since the demise of "Star Trek" as a TV series, Doohan has been touring "Star Trek" conventions in the United States and Britain.

"Besides that," he says, "I go to a lot of college campuses and deliver a program I call 'Star Trekking with Scotty.'

"There is a big demand for the show. I'm a big supporter of the U.S. space program. And I usually go there and give a talk about the space shuttle the government named the Enterprise."

Doohan says the shows alone give him a comfortable living. Residual payments from the TV series have long since stopped. And according to him, his financial security may be enhanced by the movie.

"You know they will make sequels, I don't care what they say now. When all the money comes pouring in, they will make others.

"And, no matter if you thought the TV series was kid stuff or not, when you see the film you will be amazed."

Ever since Paramount began shooting the movie, security on the film set has been as tight as on a genuine space project.

"There is one thing we have been careful about, that is not to do special effects just to do them. The effects are only there when they are absolutely necessary.

"We are not trying to out-effect any other film. I saw 'Battlestar Galactica.' All it was was the 'Gunfight at OK Corral' with spaceships.

"star Wars' was great entertainment and a lot of fun. But it was fantasy and not "Star Trek,' which today is getting closer to reality than fiction."

Doohan has been with "Star Trek" from the beginning. And partly because he didn't have many other places to go, he has stuck by the Enterprise through the 10 years since U.S. television tried to kill the show.

But he refused to let it die. "I personally see between 150,000 and 200,000 people a year. These are people who believe in the show."

It s this support for a dead TV series that has made "Star Trek" the most successful failure ever produced in Hollywood. The money the show has made, and still makes through worldwide syndication, is more than it could have made as a network show for the normal five-year run.

Why then did it take so long for a feature film to be made?

"Well, for one thing, it wasn't on account of problems with the stars. It was a conflict at Paramount Pictures," Doohan said. "They didn't know what the hell they wanted to do.

"First of all they didn't believe "Star Trek' could come out again years later as another TV series or as a movie.

"When NBC dropped the show it caused Paramount to disbelieve so much that the actors wound up working on the final series at the same pay scale we were given for the second series. They told us to take it or leave it."

At that point Doohan took a quick look at his ship's comunicator tucked neatly beneath his belt. "If you will excuse me," he said, "I'm being paged by Dr. McCoy. And it's a long way off."