MAGAZINES have always been the lifeblood of science fiction. Writers as famous, and different, as Ursula Le Guin, Robert Heinlein and Thomas M. Disch started their careers with work in The Magazine of Fantasy and Science Fiction, Astounding and similar publications. Indeed, most critics would say that the best and most inventive science fiction takes place in its short forms, the story and the novella.

Consider, for instance, Howard Waldrop's comic and touching "Ike at the Mike," which first appeared in Omni. What if a young man from Kansas, on his way to enroll in West Point, had run into an old black musician while the train was chugging north? Waldrop tells his story in a series of flashbacks as the now-legendary bluesman Dwight Eisenhower performs at the White House. Seated in the audience, Senator Elvis Presley regrets that residential ambitions cut short his own dreams of a musical career.

A Washingtonian wishing to get a sense of science fiction could hardly do better than to read Isaac Asimov's Science Fiction Magazine, F&SF, Amazing, and Analog. Fiction, convention notes, book reviews, letters, author profiles, even advertisements -- what local editor Ted White calls the "epiphenomena" of the field -- are all there.

For the serious enthusiast, Locus, Fantasy Review and Science Fiction Chronicle provide regular news of writers, publishing and conventions.

During the past year, two important magazines have been based in Washington. Thrust, edited by Doug Fratz, began its life as an undergraduate magazine at the University of Maryland but is now a semi-professional publication specializing in author profiles, criticism and polemics.

Thrust appears twice yearly, with back issues readily available. (Write to Thrust, 8217 Langport Terrace, Gaithersburg, MD 20877, or telephone: 301/948-2514). The current isue includes interviews with Larry Niven, best known for the hard- tech novel "Ringworld," and Jack Dann ( whose book "The Man Who Melted" was up for a recent Nebula); columns of polemic and criticism by well-known critics Darrell Schweitzer and Ted White; editorials by Fratz; as well as book reviews, letters and the results of an award contest for the most disappointing sf of last year. Despite its infrequent appearance, Thrust remains an important source of sf commentary.

After only four issues under the editorial direction of Ted White and David Bischoff, Stardate, "the multi-media science fiction magazine," looked like a hit. Combining fiction, essays, gaming news and comics, the slick magazine had the sharp, clean looks of Omni, while it attracted the best of the younger generation of writers. The first four issues carried an interview with Frank Herbert by science fiction's chief gadfly, Charles Platt; fiction by Rudy Rucker, Somtow Sucharitkul and William Gibson, as well as superior stories from less well-known figures; and editor Bischoff contributed a three-part series on the TV program "Doctor Who."

Cover illustrations were painted by distinguished sf artists such as Carl Lundgren. The staff planned to expand, ideas were in the air for spin-off magazines, and then the Stardate galaxy went nova. According to White, the chief financial backer pulled out just when profit was in sight. So the April issue, just out on the newsstands, will be the last, unless publisher Dana Lombardy can find new backing. Even if he can't, Washington readers should at least check out the past four, exceptional issues.