Comment Re:As with all space missions: (Score 1) 200
A circumnavigation of Venus would test our ability to function in deep space, to enter a planet's gravitational influence, to create robust shielding for the higher radiation at Venus's relatively close proximity to the sun, to devise zero-g strategies for long-duration flights -- all of which would bolster us for an even longer journey to Mars.
We've already done most of those things. Function in deep space? We've sent many successful probes all over the place, adding a human payload doesn't change the physics. Enter a planet's gravitational influence? Ditto. Create robust shielding? We need to figure that one out before leaving the Earth-Moon system, and test it on a probe before committing people to it. Devise zero-g strategies for long duration flights? Been working on it ever since Skylab, no need to even leave Earth orbit to study the effects.
None of these things require or even benefit from using Venus as a target, nor does Venus make a good testbed for missions elsewhere. With the Moon or Mars, the problems on the surface are very similar to the problems on the journey: Low pressure, low gravity, exposure to radiation. With Venus the problems are exactly the opposite of those on the journey. High pressure, high heat, corrosive atmosphere. Venus is a pressure cooker full of sulfuric acid. That makes Venus a lousy analog of anywhere else in the solar system, with the possible exception of Io. If we're going to spend the effort on surviving Venus there has to be some reason for it that's unique to that planet. "Practice" ain't it.