HOUSTON - Ron Dittemore simply cannot help himself. The shuttle program manager is clearly beside himself with grief, and yet he is also so keenly absorbed by discovering its genesis that from time to time, wonder will creep into his voice and raise it a notch. "It's not the absolute value of attitude change that is interesting," he said at one point yesterday, describing the pitch of the space shuttle Columbia's doomed flight last weekend. "What's becoming interesting to us now is the rate of change." At another moment, he said, of temperature increases captured at the mid-section of the...