>The same is true for spaceflight, where the formulas for rocket propelled vehicles are well understood.
You are assuming there never will be a replacement for rocket technology. I think you're wrong.
The interval from Gargarin to now is 58 years. 58 years from 1914 puts us to 1972. By '72 we had turbofan jet airliners of all the current layouts including 4 under the wings, 2 under the wings, 2 in the tail, and different layouts of 3 in the tail. There had been the ill-fated Comet with 4 in the tail. The Concorde SST had done its first flight already in '69. There has been no comparable advance in space flight technology in the last 58 years.
Since '72 there has been cost reduction and refinement of the jet airliner, but prices also have come down due to higher volumes, more passengers per flight, and a reduction in service.
What is this new propulsion technology that you anticipate?
Because there was no incentive. Space was something governments did and after the USA won the space race, interest waned. SpaceX proved there is a commercial market. Now we are witnessing the start of a commercial space boom. https://en.wikipedia.org/wiki/List_of_private_spaceflight_co... Look at the number of launchers in development. Competition = innovation. And once space mining has been proven as a concept, then the real boom will begin. I'm optimistic and expect all of this to happen in the next 20 years.
>What is this new propulsion technology that you anticipate?
Ion drives?, scramjets?, something that hasn't been discovered yet?, ... I honestly don't know but I doubt we will still be stuck with chemical rockets a 100 years from now.