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Completely impossible to build a B-52 in 1944 even with the blueprints. The technology to make the engines did not exist, and it would take years to develop.
In that series they also explained - without going into detail - that they used the technology from 2021 to build highly automated factories, which were compared to The Terminator movies in sophistication. The B-52 was designed circa 1950-51. I recall unfolding a B-52 component drawing, looking at the data on it, and telling the other engineers there that I could not work on it because it predated my birth (they were unimpressed with my reasoning but advised me not to drool on the drawings).
In terms of materials and other technology of 1942 the B-52 and its J-57 engines could be built. You need aluminum, steel, stainless steel and nickle alloys and all were available in abundance. No TI or composites required. Presumably they could have gone direct to the B-52 and J-57 and avoided the B-50, B-36, B-47, and numerous development steps and missteps along the way.
Do it in essentially 2 years? I donno. But five years is dead easy and three years very likely.
By the way, they also built a lot of F-86's, UH-1's, and AC-47's.
The US Navy has computer controlled manufacturing capabilities on its ships right now, and have had for decades. They have Haas computer controlled machines on board, which makes a sailor who is able to read a manual a pretty good machinist.
But they could have taken the technology they had available and built computer controlled manufacturing equipment. They had automated manufacturing equipment in WWII as it was. Biggest problem with anything they did would be how much to improve it versus leaving it alone. For example, I think I'd build the B-49 rather than the B-52. The computer controlled stability augmentation systems likely would have solved the problems with the flying wing. Going straight to the B-2 would be hard to do, but the B-49 should be pretty easy.
I've often wondered what I could do to help if I went back to 1942. What could I do other than telling them what to focus on that they were soon going to do anyway? Now, a whole force of advanced ships showing up is a different situation.
I have no idea what they'd need to make the J57 engines, though. Would you be willing to hazard a guess?
There was a movie made along these lines a couple of decades or so ago, where a CVN weirdly intruded into
the waters of Hawaii in early Dec `41, & the skipper had to agonise about not using F-14s to waste Nagumo's fleet..
Similar with 1950s and 60s jet engines. The materials used and temps and pressures achieved didn't happen overnight. It came from an evolutionary process that began before WW2, therefore things needed to happen first. Running before you can crawl never works. There are examples in history of technological advance way ahead of its time failing. AA Griffith's compressor designs for RR are an example. RR built one and found they couldn't get it to work because the materials were not up to the task of doing what was required. You can't build the Space Shuttle without having built the A4 rocket first.
The processes involved in manufacturing the turbine and compressor blades was not really available in the US in 1942, or anywhere. These processes were in the very early stages of development in 1942.