NASA offered their "vomit comet" plane that can create weightlessness, for filming (it was previously used in Apollo 13 (1995) for the weightless scenes). Clint Eastwood turned down the offer for fear that the older actors would be made too sick to film.
The "Asshole Centering Module" is a closed-circuit video system used during ground-based Shuttle astronaut training. It displays a view of the astronaut's posterior so they can remember the position they are in when using the Waste Collection System.
NASA jargon during the STS-200 ascent: "Negative Return" means that the Shuttle is beyond the point of being able to return to the Kennedy Space Center and the Shuttle Landing Facility. "Two Engines TAL" means that the Orbiter can reach the primary emergency Trans-Atlantic Landing (TAL) site in Merona, Spain even if one of its three Main Engines fails. "Press to ATO" means that if one engine fails, the crew will make every effort to Abort-To-Orbit instead of landing at the secondary emergency landing site in Zaragoza, Spain. After ATO, it may still be possible to perform the mission as planned if the orbit is close enough to nominal.
Clint Eastwood, James Garner, Tommy Lee Jones, and Donald Sutherland are all playing characters in the same age demographic. In actuality, only Eastwood and Garner are close in age, while Sutherland and especially Jones are too young to have been astronaut pilots in 1958 as mentioned in the script.
To create "weightlessness," the actors clung onto objects as if they were grounding themselves. Clint Eastwood opted against using the "Vomit Comet," the plane used to film weightlessness in Apollo 13 (1995).
The night scenes where Tommy Lee Jones and Marcia Gay Harden are alone together was filmed in the University of Houston - Downtown campus satellite parking lot; permission from the university was needed to film the night scenes. Clint Eastwood met with UHD president Dr. Maximillian Castillo in person in late 1998 before filming began.
The interview with Jay Leno was filmed in front of a real Tonight Show audience. Leno made monologue jokes about Viagra, Matlock (1986), and prostate problems. Leno ad-libbed with the actors like he would in a real interview.
The film reunites Clint Eastwood with Donald Sutherland, who starred alongside Eastwood in Kelly's Heroes (1970), and James Garner, who played Bret Maverick in the 1950's TV series Maverick, with Eastwood appearing in one episode, 'Duel at Sundown' (broadcast 1/2/59).
The trivia items below may give away important plot points.
As it approaches the Kennedy Space Center, the Daedalus Orbiter makes a double sonic boom. This is because the Orbiter creates two shock waves, the bow wave and the tail wave, which are heard as separate "booms."
The original script called for the IKON orbital weapons platform to be a top-secret NASA project. NASA refused to co-operate with the film's production, unless the script was changed to depict NASA as having no involvement in placing weapons in orbit.
Tommy Lee Jones' character is introduced feet-first, as the camera moves around the corner of the building, and he is seen seated in a reclining position. The movie ends with a nearly identical arrangement, where the camera pans around the corner of the wreckage on the Moon, and he is once again seen with his feet first then body reclining in death on the ground face up positioned towards the Earth.