Spinning off from another thread.
Space exploration threads tend to spiral down into the "oh we could have put men on Mars by now" manned space exploration / colonization attractor. Let's try to avoid that.
Assume instead that with a [handwave] POD around 1970, humanity decides to roughly double its budget for *unmanned* space exploration. What would we have by now?
Possibilities:
-- a balloon probe drifting in the atmosphere of Jupiter
-- a powered zeppelin in the atmosphere of Venus
-- a lander on at least one moon of Jupiter, probably Europa
-- rovers all over the Moon; in particular, rovers examining the volatile deposits and other interesting stuff at the poles
-- a couple of Mercury orbiters; possibly a Mercury lander
-- Pluto flyby already (OTL en route with a 2015 ETA)
-- A close (<0.25 au) solar orbiter (OTL planned for 2015 launch)
-- a solar polar orbiter (inclination >45 degrees)
-- Galileo / Cassini-style missions to Uranus and possibly Neptune
In terms of drive technologies:
-- widespread use of ion drives for missions to the outer solar system
-- solar sails past the prototype stage
-- tether for LEO / HEO orbital momentum transfer in the planning stage
Things I don't think we would plausibly have seen by now: sample returns from the outer solar system, rovers outside the orbit of Jupiter, a rover on the surface of Venus, widespread use of solar sails, actual deployment of a working tether.
Thoughts?
Doug M.