Things that might have been

One of those things was a molten-salt reactor.  Another one was the nuclear thermal rocket.

One thing that did get built was a partially reusable launch system---the Shuttle.  However, the Shuttle could have and should have been better.

There was a plan to use the Saturn V rocket engines in a design for the Shuttle.  The lower stage of the Saturn V would be converted in order that it could return to the launch site.  The conversion was to make it into a type of rocket plane/booster that could lift the Shuttle to a certain altitude and velocity, then separate, and return to the launch site.  It could have worked and the moonwalking astronaut, Edwin Aldrin, was in support of it, if I am not mistaken.

However, it never got built.  The government, in all its wisdom, decided to build a new rocket engine and solid rocket boosters instead.  With that decision, they pretty much doomed the idea of a fully reusable rocket launch system.

Elon Musk is using that same idea with his Grasshopper concept.  It won't be the same as what was envisioned, but the concept is similar in that the first stage will return to the launch site.  Instead of flying back, it will power itself back as a rocket, and land vertically.

Musk's system is much lighter weight and much less ambitious.  The Shuttle, in contrast, was much too big.  As I've discovered in my study of the rocket equation, mass is the big enemy of space flight.  You MUST get the weight down.  The Shuttle weighed over 200k pounds.  Much, too much weight.

Instead of what they built, they could have built a smaller Shuttle with much less payload capacity.  The smaller shuttle would need a smaller booster to get to the needed altitude and a nuclear thermal engine would have been able to get the Shuttle itself the rest of the way, PROVIDED THAT IT DIDN"T GET TOO HEAVY.

All of this was possible 40 years ago.  Our leadership failed us when they came up with a system that was much more expensive and less capable than what it could have been.

Am I reaching anybody out there?

Hope so.