The Big Bang Theory Season 5 Episode 23
The Launch Acceleration
Howard's trip to space is canceled and he is happy about that. He is afraid of going into space. The guys go to get their tuxedos for Howard and Bernadette's wedding.
Amy decides that she is going to persuade Sheldon to get closer to her by tempting him with his favorite things. And, it works.
Leonard and Penny decide to move their relationship to the next level and sleep together. But, Leonard messes it up by asking her during sex to marry him. Penny doesn't break up with him, but she says "no" to his proposal.
Howard finds out that he is rescheduled for another trip to space, but it is before he is supposed to marry Bernadette. She wants him to go to space, but he insists on staying for the wedding due to his fear of space. Even Bernadette's father wants him to go to space. Is he going into space or will he stay for his wedding?