Trivia: An interesting scene to watch is when Heywood Floyd is talking to his associate on the bench in front of the White House, there is a long shot when you can see a person feeding pigeons. It is none other than Arthur C. Clarke in a cameo appearance. (00:10:59)
Trivia: While it's well-known the voice of HAL in "2001: A Space Odyssey" is Canadian actor Douglas Rain, who returned to reprise his role in this film, it's less known that the voice of SAL is credited to "Olga Mallsnerd" which is a false name used by none other than Candice Bergen. (00:14:05)
Trivia: In the nursing home scene, the nurse at the desk is reading Time magazine. The cover concerns the US/Soviet conflict integral to the plot. If you look closely, the US President's picture is a colored drawing of Arthur C. Clarke and the Soviet Premier's picture is a colored drawing of the director of 2001, Stanley Kubrick. (01:17:18)
Trivia: In the scene where they are Airbraking , they are hauling super fast around the planet , but you can see stuff dripping from the fireball straight down.
Answer: If they didn't, any further manoeuvring would require much more fuel. They would be moving the mass of two ships.