In the 2001 novel, Discovery’s original mission parameters were to explore Jupiter. It had been five years of preparation, construction, and the resulting launch of Discovery. Shorlty after embarking on the Jovian system, a last minute directive is privately transmitted to HAL 9000, the Discovery’s onboard supercomputer. The new mission directive: investigate an anomalous radio energy signal—targeted precisely at Saturn. It would take two years before just arriving to the Jovian system. Upon arriving, HAL is directed to initiate a flyby of Jupiter, using gravity assist to slingshot the Discovery spacecraft into orbital range of Saturn’s moon system.
The new mission objective to Saturn’s moon system was considered a calculated risk into the unknown. Discovery would essentially consume its return home fuel for a trip to Saturn, and would have to rely on a type of “rescue” mission, to bring the crew back home. Thus, Discovery 2 began construction to do just that—bring Discovery’s crew home. However, the wait could be seven to eight years, before even seeing a rescue ship.
Bowman later determines that the anomalous signal that triggered the re-direct, was pointed at one of Saturn’s moons, Iapetus, where a monolith (designated TMA-2), sat upright on the moon just like that of the TMA-1 discovered in 1999, in the Tycho crater, on Earth's moon. In the film adaption, once the Discovery arrives to the Jovian system, the mission objective (TMA-2) suddenly appears in space, in the proximity of Jupiter's moon Io.[note 1]
- The following calaculations attempt to give a somewhat realistic Space Odyssey timeline, but is considered fanon, because, according to Arthur C. Clarke, his excuse for inconstancies was “parallel universes”.
The following calculations are based on Arthur C. Clarke’s time frames given in 2001: A Space Odyssey and current scientific data. However, Clarke had only given general timeframes, and was not overly concerned about trying to make his Space Odyssey stories fit in perfect timelines. Clarke even made a comment to Peter Hyams (in the email correspondance diaries), that he thought that maybe it was year 2001, when they discovered the TMA-1 on Earth’s moon.
- Project Jupiter
Clarke: 2 year trip on Discovery
- Distance from Earth to Jupiter: 588000000 kilometers (3.931 astronomical units)
- Est. timeframe: 2 years
- Mission redirect
Clarke: Use Jupiter as a sling to Saturn’s orbit
- Distance from Jupiter to Saturn: 655000000 kilometers (4.378 astronomical units)
- Calculation: If it takes two years to travel 4 AUs, maybe with Jupiter’s slingshot coupled with the Return Home propulsion fuel, Discovery could cut travel-time, by half, to get to Saturn.
- Est. timeframe: 1 year
- Signal at Iapetus
Clarke: Discovery to orbit Saturn
- Distance from Saturn to Iapetus: 3560851 kilometers (0.0238 astronomical unit)
- Est. timeframe: shaves off a fraction from the redirect trip.
> Calculations: Monolithic events in mid 2001 minus 3 year journey (2 years to Jupiter, 1 to Saturn) = mid 1998 launch date.