DEFYING GRAVITY, Brown Couch Theatre Company, at the Athenaeum. This meditation on flight as a metaphor for human efforts to encounter God never quite reaches the profundity of its predecessor The Little Prince. But when author Jane Anderson forgets her tight little scheme long enough to present relationships between the characters, she creates some wonderful moments. She tells the story of teacher Christa McAuliffe's death on the Challenger through scenes between the astronaut and her daughter, an elderly husband and wife who travel to Florida to see the launch, and a NASA maintenance man and his girlfriend. Anderson has a fine ear for conversation but undermines it with ridiculous devices like narration by a time-traveling Claude Monet, whose fascination with light's movement across the sky is supposed to connect him to the story but doesn't. His monologues and those of the other characters form an indigestible lump midplay, representing the triumph of exposition over action and theme over plot. Naturally, then, the strongest performances come from those with the fewest soliloquies. As the elderly couple, Dennie Sherer and Kate Winters are perfection: they repeat the same story in different words, interrupt each other, spat, but stay together. Suzanne Lang Fodor conveys the thought processes of McAuliffe's six-year-old daughter without preciousness. And Aimee Whitmore's slide design provides an evocative backdrop. The play's the weakest thing--but Anderson may produce something really worth watching once she lets go of the homilies and emphasizes her sure sense of how people complete one another.