If you like the SR-71, the U-2 CIA spy plane is at least as fascinating. All this was retired because of advancements in satellite technology.

https://en.wikipedia.org/wiki/Lockheed_U-2

« what we must have 'secretly' concocted » — Secrets are often dirty, which is why they're secret. Not for public consumption. Like, what is the secret behind Wikileaks Bradley Manning's “conversion” into “Chelsea” after whistleblowing secret dirty videos showing the world how dirty it really is in there? In that military? Did they castrate him in custody?

Rather than wondering about “secret tech”, boyish fantasies fueled by Pentagon sponsored Hollywood movies glorifying guns and violence and blasting enemies (they always need enemies), ask yourself whether all of the stuff publicly and conspicuously trumpeted about (not only in past decades) did and does actually work and exist. ;)