Assault on the Gods — Stephen Goldin

Ardeva Korrell, captain of a small interstellar trading ship, has fought prejudice, both because she's a woman and because she's an Eoan, a native of a world with an unpopular religion. Now she's fighting the god-like rulers of a backward planet to save not only her crew, but the entire native population as well. Their mission is straightforward: to storm the gates of Heaven itself.