 The characters experience many emotions for the first time during the events of this story.  What emotion(s) push the characters through the door.
When nobody aboard ship remembers where it's going, how can they tell when it has arrived? But ever since the engines somewhere in the rear of the world had changed their tone, from the steady whining Rikud had heard all twenty-five years of his life, to the sullen roar that came to his ears now, the feelings had grown. But it came again, and each time it left him with a feeling he could not explain. Rikud knew that something which he could not explain had entered the elder man's head for a moment, but it had departed almost before Chuls knew of its existence. But something soft had cushioned the impact—something which had come into being just for the moment and then abruptly passed into non-being again, something which was as impalpable as air. There had been a revolt—again a term without any real meaning, a term that could have no reality outside of the reading machine—and the elders were overthrown. The people had decided that they did not know where they were going, or why, and that it was unfair that the elders alone had this authority. Much of this Rikud could not understand, but he knew enough to realize that the reading machine had sided with the people against the elders, and it said the people had won. "Variability," he told them, "is a contradictory term. Again there were inexplicable feelings—strange channelings of Rikud's energy in new and confusing directions.
 Hatred and anger.
 Sadness  Hatred and anger.  Excitement and curiosity.  Pure happiness.