In short, meals on Apollo had to keep the astronauts happy, healthy, and had to not gum up the spacecraft if they floated around. Before each mission, astronauts got to pick their favourite foods, and their choices were then assembled into roughly 2,500 calorie, nutritionally balanced meals. There were four different meals for each breakfast, lunch, and dinner, and the mission schedule cycled through them in sequence, so meals were repeated during a flight. And one staple throughout the program was bacon. Or, more specifically, bacon cubes.