Originally Posted by Romanus

My guesses, just for fun:

1.) We will have landed on Mars, but will have no colonies there.

2.) We will have small, expensive, useless facilities with rotating staff on the Moon. Nobody will care, but I think interesting science will be done (primarily selenological). At least two or three other countries besides the U.S. will have sent humans there.

3.) I'm cautiously optimistic about space tourism. I say cautiously, because a single disaster early in the program could put the whammy on the whole concept; notice that dirigibles are still not carrying trans-Atlantic passengers since the Hindenburg? If it can weather the first disaster--and it *will* happen--then I see a bright future for it in 2051.

4.) Almost all the basic astrophysical questions--the mass-luminosity relation, binary stars, black holes, SN rates, extragalactic distances--outside of cosmology will be answered due to missions like GAIA, JWST, SIM, and the like. I think this will subtly change astrophysical research, making it increasingly theoretical.

5.) We will have a rough idea of how common terrestrial planets are versus gas giants, and will know of thousands--maybe even tens of thousands--of each. We will also know if earthlike--those with intriguing spectroscopic signatures--planets are common or not.

6.) We will have sent an orbiter to every major planet, and possibly a lander/atmosphere probe as well. Ditto for Titan, Europa, and Enceladus.

7.) Advanced propulsion methods outside of ion propulsion (solar sails, nuclear thermal, VASIMR, etc.) will still be woefully understudied and underfunded.

8.) We will finally have CATS, from something in the Falcon strain.