''Star Trek.'' For 20 years the name has conjured up a masculine world - Natty Bumppo and Chingachgook exploring the wilderness of the final frontier. In three endlessly rerun seasons of prime-time television episodes, one and a half seasons of Saturday morning cartoons, three movies and an apparently never-ending series of paperbacks issued now by Pocket Books, Capt. James T. Kirk and his first officer, Mr. Spock, have traveled the universe righting wrongs and defending truth, justice and the middle-class American way. And the adventure continues. Last month Paramount Television announced it would produce a new ''Star Trek'' series, to premiere next September; fans are celebrating the 20th anniversary of the series with a convention in Boston this weekend; and another movie, ''Star Trek IV: The Voyage Home,'' will be released Nov. 26. BUT there is another world of ''Star Trek.'' Close to 10,000 fans, most of them women, have created over 30,000 pieces of fiction, poetry, song, criticism, commentary and graphic art based on the television show, movies and the writing of other fans. The work appears in amateur publications called fanzines, distributed at conventions and through the mail. Because they use the copyrighted products of others as a basis for their art but do not pay for that use, writers in the community are legally constrained from making a profit.

This partially explains the predominance of women in the community: male fans of the show generally balk at the restriction and prefer to engage in activities such as costuming or crafts, for which payment is not a traditional reward. Women, who traditionally spend large portions of their lives working in relative isolation for little or no pay, bring a different set of motivations to their writing and art. They want to talk to other women, to express themselves in the science fiction form that until recently has all but excluded them. The writers cannot sell their work, but they don't have to meet commercial criteria for success either: they must please only the predominantly female ''Star Trek'' fan community. For the past 10 years, at least, women have accounted for over 90 percent of the writing and graphic arts and for almost all the editing of the ''Star Trek'' fan publications. Together the writers, editors, artists and reader-critics form an artistic community that shares work and appreciation.

The first thing I discovered about ''Star Trek'' is that individual, ''unique'' creation is not as important to these women as sharing a fantasy universe in which real-life concerns such as sexuality and equality can be discussed in the metaphorical language of ''Star Trek.'' This sharing may take the form of a story tree, a group of stories, poems, pieces of artwork, or novels by one or more authors. The most characteristic feature of the story tree is that the stories do not fall in a linear sequence. A root story may offer unresolved situations, secondary characters whose actions during the main events are not described or a resolution that is unsatisfactory to some readers. Writers then branch out from that story, completing dropped subplots, exploring the reactions of minor characters to major events. Differences of opinion do occur: a writer may reconstruct someone's story from a new perspective or offer a completely different ending. Raising the dead has long been a popular option in the latter category.

ONE example of a story tree is the ''Kraith'' universe, created by Jacqueline Lichtenberg in 1968. In a few short stories written as group, Ms. Lichtenberg set up the basic cultural milieu and the course of events the story tree would follow. The Kraith is a cup, a religious symbol integral to the most important rituals on Vulcan, the home planet of Sarek, who is the father of the half-alien Spock. In the basic story line, the cup has been lost, and Sarek has been kidnapped. Though he is only a minor character in the television series and in the third movie, in the ''Kraith'' universe he becomes, as so often happens in story trees, a central figure.

Ms. Lichtenberg created both the cup and the rituals, yet she depended on her readers' knowledge of Vulcan culture and physiology (as established in the television episode ''Amok Time'') and the relationship between Spock and his father (as established in another episode, ''Journey to Babel'') to ground the new material in the familiar. A classic Grail quest might have followed from the author's invention, but she resolved that quest early in the series. Sarek and then the cup are found, and what for Ms. Lichtenberg is the real quest, to discover the self as it grows in relationships with others, openly moves to the fore. ''Star Trek'' provides the metaphorical means Continued on page 28 for it to do so. Fan writers explore telepathy both as an integral part of Vulcan culture and as a device to examine relationships between characters. In the ''Kraith'' series, Captain Kirk, a highly intuitive military officer, develops into a telepath. Spock's family adopts the captain to train him in Vulcan techniques for controlling his talent. To ''Kraith'' writers this development of one of Spock's more important relationships, his friendship with Captain Kirk, was inevitable. But telepathy means more to them than this. It represents the possibility of complete understanding of another person, of incorporating into the self that other being with all its strangeness and of exposing the self to the stranger. The theme of the individual in tension with the whole is never far from the surface here.