Hi All

Combine the best of choppers and balloons - a dirigible like JP Aerospace's V-ship Ascender would be ideal, especially since blue skies are at extreme altitudes on Venus and Titan. And a sample return from Venus would need to be an airship for part of the "launch" because the atmospheric drag would be too high for a rocket.

A Titan airship could distill methane from the air and use it, lightly warmed, as a lifting gas since the main constituent is nitrogen. A Venus ship could freeze out the CO2 to extract the nitrogen for a lifting gas. A Venus "lander" - though "floater" would be better - could use compressed hydrogen as lifting gas in the lower reaches, then use it in a jet using CO2 as oxidiser with hydrogen higher up. A solid[?] rocket would provide the final boost to orbit. Or the booster could loiter in the cooler upper air.

All the big planets would need to be "hot" hydrogen balloons - room temperature gas would do pretty well. Personally I think the probable turbulence would kill anything other than nuclear ramjets - several good designs exist for such.

Adam