The arguably most complex technology of Space Shuttle was SSME. Also, arguably the most important part of LEO rocket technology is engine - as soon as engines m

The arguably most complex technology of Space Shuttle was SSME. Also, arguably the most important part of LEO rocket technology is engine - as soon as engines matured enough, space era started. Yes, there are gyros and superlight tanks, but Lambda-4S still does illustrate the importance. And hypersonic winged flight problems were greatly decreased in the Space Shuttle case by a "brute force" approach with ceramic tiles. SSME was more or less repeated in results by RD-0120, and rather soon. I'd argue RD-0410 was more complex. SR-71 engine works in two different modes, and even today is not really repeated elsewhere. I think that shows how awesome the SR-71 design was - especially, but not only, for its time. I'd appreciate a good analysis of design problems and solutions of SR-71 to decide which project was technically more complex.