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For SLS a group looked into making boosters powered by modernized F-1's... Turns out a lot of knowledge about welding them had been lost. They managed to get an old unflown F-1A to work, but it's a bit unclear how much they managed to do with the new design, the F-1B. Wikipedia[0] has a few details and some links, but it falls short of telling the end fate of this effort.

Obviously, the F-1B booster wasn't picked for the SLS and they went with the improved 5-segment SRBs[1].

[0] https://en.wikipedia.org/wiki/Rocketdyne_F-1#F-1B_booster

[1] https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Boo...

> Actually doing it is important. “I can go to the moon anytime I want” stops being true after a solid generation of not doing it. There is institutional knowledge in doing something in the present world. Further, specs and documents are nice, but rarely sufficient. A famous example is the F-1 engine. Every one of them was made off spec and if you took the factory drawings alone you would never make a working engine. You need builders who understand the design and modify it

And I'd argue that's exactly why I'd argue the fundamental approach of the 60s/70s rocket engineers was fundamentally flawed. It was a vanity project and so it died after vanity was satisfied.

The assembly line and standardisation approach SpaceX takes is much superior and much more sustainable.

I agree. Importantly Space-X’s engines are actually cutting edge. They are the best performers man has made, so we’re not walking backwards. However, that progress was not guaranteed and if we stopped all space travel for fifty years there would need to be another monumental effort to relearn how to build rockets.

I play with CRTs as a hobby. It’s popular these days, but it will never be popular enough to manufacture another CRT. The last assembly lines closed a decade ago. The physics knowledge is there, and electronics have gotten better, but it would take many iterations to make a trinitron equivalent in another 20 years. The people who understood the magnetics (ie how horizontal output transistor and flyback transformer characteristics interacted with the impedance of the steering coils) are dead or retired. The same for the experts in mask manufacturing. We can figure it all out again and do it better than ever, but it would be a lot more work than if we had continued making them.

Again, it’ll never happen because they’re too big and require too much material compared to other display technologies. It’s just interesting how fast they disappeared when they were an integral part of human society for nearly all of the 20th century.

I agree that there’s probably not much value in just retreading the old specs, but I’d argue that just having the knowledge that it has been achieved in practice still puts you ahead of the engineers in 1961, and that the intervening decades of progress put you even further ahead.

There’s no reason to think that an equally well funded greenfield effort couldn’t land on the moon from a standing start within a decade; it’s not like we’re living in the shadow of an ancient advanced civilisation with no present day industrial capacity.

No and I agree. Saying that we’ve regressed in rocket science or concrete in any capacity is a fantasy. However, if things go stale then we could be forced to invest a lot of money to discover things we’ve already discovered.

Yes, that’s true. Knowledge-how will go stale relatively quickly as you point out.