Unfortunately for "Battle Beyond the Stars," a new low-budget space Western, at least one area theater at which it's now showing precedes it with the trailer for "The Empire Strikes Back," one of the most sensational and inviting pieces of "coming attraction" art ever. "Battle" is bound to look seedy and tatty after that, and does.

But it probably would anyway, since the level of fantasy maintained in this Roger Corman production isn't very rich or zesty. Children at a Saturday matinee indicated they found the action sequences amusing but took to ridiculing and mimicking the deadly dialogue that tied them together. A smutty innuendo or two -- such as a double-entendre reference to a "torque bar" -- and the arrestingly undraped and mythologically constructed actress Sybil Danning are probably not enough to keep adults engrossed while the kids squirm.

The John Sayles screenplay puts the plot of the Japanese film classic "The Seven Samurai," later Hollywoodized into "The Magnificent Seven," in an outer-space setting. The timid and tidy little planet of Akir -- where everything is solar-powered (though the sun never seems to be shining) and the people get to stay in their pajamas all day long -- is menaced from beyond by the vile megalomaniac Sador. He hovers over Akir one day to announce from his spaceship, "I possess a stellar converter, the most powerful weapon in the universe. You cannot resist me."

It would seem a trifling conquest, since the entire population of the planet isn't much larger than the cast of "Barney Miller." But the Akira, in self-defense, send one of their young men out in a spaceship to round up some mercenaries as bodyguards for their planet. All the moral implications of the original fable are resoundingly ignored and the story becomes simply a matter of finding the vigilantes and fighting the big battle.

Among other maladies, the picture suffers from chronic miscasting. Richard Thomas is at his neurotic wimpiest as the young hero, so ineffectual and limp on camera that it's impossible to root for him. Mistaken for an android at one of his stops and told by an alarmed captor that he's "warm," Thomas replies, "Of course I'm warm, I'm organic," but it sounds fishy to us.

George Peppard, very long in every tooth, especially for a beach-boy-blond haircut, slumbers around the screen as Cowboy, a tiresome cliche from, and an affront to the dignity of the planet Earth. Robert Vaughn, clearly aware he is above this sort of thing, looks peeved and weary as an outlaw called Gelt; you can practically see his actor's paycheck sticking out of his pocket. John Saxon makes Sador a purely perfunctory raving maniac.

Everyone else is pretty terrible, too, except for Danning as the hilariously voluptuous St. Exmin, pride of the Valkyries. She is a creation worthy of Frank Frazetta at this most lustily fanciful.

Other more exotic life forms enlisted for the crusades include a tribe of clones who speak in the collective "we" and can all taste the hot dog one of them eats (the kind of touch the movie should have more of), and a sort of fish-face humanoid called Cayman. Cutesiest of all is a computer on board the hero's spaceship who has been given the voice of a sassy female but sometimes sounds merely like the all-too-proverbial Jewish mother.

The model and miniature work, considering the economy with which the film was undoubtedly made, is pretty good -- except that in the climactic battle it is not easy, and perhap impossible, to tell who is blowing whom into atoms. For some peculiar reason, the hero's saggy-baggy spaceship looks mammarial from some shots and scrotal in others. And the deathstar of the picture, Saxon's moon buggy, resembles a very large Midas muffler.

Nothing in the film appears capable of seriously freightening even the youngest of children, and the picture aspires to the sophisticated innocence of "Star Wars," though never achieves it. Director Jimmy T. Murakami was not very resourceful at hiding the seams, especially in the studio interior shots, where the effect is of a bunch of actors standing round in silly outfits. He also has no clear idea of how to animate a scene and thinks the picture will appear speedy if he just flees from each piece of deadwood like a hit-and-run driver.

Any movie with characters named "Zed," "Mol," "Feh," "Lux," "Pok," "Dab," "Gar," "Cush" "Pez" and "Wok" can't, as the saying goes, be all bad, but "Battle Beyond the Stars" bravely goes only where lots of men have already gone before, proving you can blow up all the planets you want and still not be a world-beater.