Hi All

Larry... below you replied to my post about aerocapture by the "Leonov" from "2010". In my calculations I assumed the trajectory was parabolic from Earth - i.e. solar escape velocity. Quicker than Hohmann velocity by ~ 190 days. At Jupiter the hyperbolic excess relative to Jupiter was about 9.2 km/s, which became 62 km/s in the upper atmosphere, but a mere 49.5 km/s relative to the clouds because of Jupiter's spin. The ellipse back out to Io needs ~ 55 km/s, hence the "Leonov" needed to shave off 7 km/s, but to then match orbital velocity with Io it needed ~ 8.0 km/s.

A direct orbit with hyperbolic excess of 9.2 km/s at Io's radius needs a dv of ~ 8.85 km/s to circularise - no mere Hohmann transfer but a full parabolic transfer orbit. In the novel the "Tsien" was quicker [not by much though] than the "Leonov" because it blew its return fuel by sprinting and then landing on Europa to refuel - with unexpected results. The "Discovery" was quicker than either (originally) and had return fuel for a Hohmann back [a dv of ~ 7.82 km/s.]

Io's orbital radius is 5.905 Jupiter radii, or 421,600 km, and its orbital velocity ~ 17.34 km/s. A Hohmann from Earth takes 2.73 years/ 997 days, while a parabolic takes ~ 2.2 years/809 days if we assume a tangential departure from Earth's orbit.

Adam