[gjkood]

The book/movie depicts Rich Purnell using some NASA/JPL supercomputers to verify his calculations.

Knowing nothing (or less than nothing if thats possible) about Celestial Mechanics, considering that the technique (gravitational assist/slinghsot maneauver???) was used in space probes as early as the 1970s, how much computing power would be needed to do these calculations?

I guess the faster the computing resources, the earlier you would get your solutions. But are these calculations that could be done on more run of the mill computing hardware?

[scigeek42]

In the book it describes how the difficulty with the calculation came from the fact that they were continuously firing the spacecraft thrusters (it was some form of drive that used a constant small acceleration). Thus far most all of our probes use short-term bursts to change their velocities. I'm not sure how many ion-engine equipped probes we have that have needed to calculate multiple slingshot manoeuvres.

In his interview with Adam Savage the author described how he wound up writing his own custom code to calculate the trajectories of their spacecraft. One could imagine that NASA would need to consider a lot more "real-world" variables than a sci-fi author, so it is somewhat reasonable to think time on a supercomputer could have come in handy.

[Ankaios]

There's no need for a supercomputer. :) Trajectory calculations of that sort are relatively routine, even including the use of ion propulsion, and can be run on a desktop in a reasonable amount of time. (Not to say you can't come up with trajectory calculations that wouldn't benefit from a big cluster, though.)

Also, the computer in the movie was Pleiades at NASA Ames.