Flight of the Pegasus

“Space Odyssey: Voyage to the Planets” was a 2004 BBC “mockumentary” which depicted a realistic “Grand Tour” of much of the Solar System. I’ve abstracted the following data from the motion picture – chiefly the day counts at different Encounters and a Date Schedule seen at Mission Control in Episode 1. Some of the dates aren’t internally consistent with the Day Counts. My interest is chiefly the kinds of orbital change required for each segment. The “Pegasus” is a nuclear-fusion propelled vehicle, which picks up extra propellant (LH2) from prepositioned tankers at each destination. Its maximum speed, achieved on its journey from Saturn to Pluto, is 80 km/s, though it does reach 300 km/s when diving near the Sun. Just how near it gets to the Sun isn’t quite explained, but a speed of 300 km/s is consistent with diving to a bit outside 4 Solar radii. Very close indeed.

For the initial short legs of the Grand Tour, from Earth-to-Venus, then Venus-to-Mars, the cruise speed needs only be the heliocentric parabolic velocity. A slightly hyperbolic orbit from Mars-to-Sun-to-Jupiter is required to fit in the given time-frame. From Jupiter to Saturn could be parabolic again, but the flight to Pluto and back is definitely at top-speed. I haven’t tried to fit the orbits depicted into a given time-frame, so the dates are only based on a quote that one of the characters had read “2010” (published in 1982) some “40 years” before. Thus the voyage is in the 2020s, at the earliest. Clearly an alternate world, as they launch into Low Earth Orbit on a Space Shuttle…

Voyage of the Pegasus
Day Event Date Day Count Delta-t
1 Leave Earth Orbit 19-Jan-2025 0
41 Venus Encounter 01-Mar-2025 41 41
55 Venus Departure 15-Mar-2025 55
117 Mars Encounter 17-May-2025 118 63
137 Mars Departure 06-Jun-2025 138
Mars-Sun-Jupiter Max V=300 km/s
411 Jupiter Aerobrake 21-Mar-2026 426 288
Max gee 9.7
748 Party
758 Saturn Encounter 16-Feb-2027 758
803 Saturn Orbit Insertion 02-Apr-2027 803 377
1372 Pluto Encounter 06-Nov-2028 1387 584
2003 Comet Landing 15-Jul-2030 2003 616
2033 Comet Departure 14-Aug-2030 2033
2241 Earth Return 10-Mar-2031 2241 208