Originally Posted by
Less Hair
The Tu-4 bomber, a high priority carbon copy of the B-29 in metric dimensions and the first nuke capable bomber the Soviet Union had, even copied the battle damage repairs of the original US aircraft that had emergency landed in the far east.
There's a story behind that. Essentially it boils down to the engineers tasked with copying the B-29 being (a) afraid for their lives if they got it wrong and did not deliver; and (b) interpreting Stalin's instructions, who said he wanted an
exact copy. If the battle damage repair were not replicated exactly, the question would arise why Stalin's instructions for an
exact copy were disobeyed. Not following Stalin's instructions tended to be bad for one's health, possible your family's health, and even the health of co-workers.
It might also have been Stalin's way of assuring quality control, in much the same way as the well known
story of David Lee Roth of Van Halen and the brown M&Ms. So long as people don't know what you are going to check up on, they have to make sure everything (including the important bits) meets the specifications; and if something minor doesn't meet the specification, you know attention to detail has been lacking.
There's a lot more down the rabbit-hole hole of copying high technology. Sometimes seemingly nonsense or trivial design decision have underlying reasons that are important (such as the research needed to replicate the manufacture of Space Shuttle tiles, which hinged upon discovering an apparently unimportant impurity in one of the chemicals used in the process affected the outcome, so using purer raw materials failed in getting the correct end-product* & **), or deliberate bits of nonsense included to show that a copy is in fact a copy rather than an original design. Copies are sometimes made because the copier does not understand the underlying engineering sufficiently to make a functional replica from the ground-up, as opposed to an exact replica. And, even if you have the original, and even know the manufacturing process used to make it, you can still miss important elements if your product depends upon specific raw materials or undocumented practices executed by experienced technical personnel.
*It's alluded to on page 7a of this very old presentation:
Producing the High Temperature Reusable Surface Insulation for the Thermal Protection System of the Space Shuttle (Kevin Forgsberg) - while some contaminants/impurities were definitely not needed, it turned out when moving from the lab to full production that certain others were.
**It turns out I mixed up two stories here. I'm leaving the Space Shuttle Tile Manufacture presentation in, as it is interesting, but what my memory mixed up was the
FOGBANK story:
Nuclear Weapons Journal, issue 2, 2009 p20: Fogbank: Lost Knowledge Regained.
When investigating historical records with respect to impurity levels during the Fogbank purification process, personnel discovered that in some cases the current impurity levels were much lower than historical values. Typically, lower impurity levels lead to better product quality. For Fogbank, however, the presence of a specific impurity is essential.