by Steve Weintz
The invention of syntactic foam, a buoyant material made of tiny air-filled glass beads embedded in plastic, spelled the end of the bathyscaphe and its dangerous, fragile gasoline balloon. Trieste II entered retirement as a museum display at the Naval Undersea Museum. The last remaining KH-9 satellite, an engineering prototype, was to have become a centerpiece of the National Air and Space Museum's new exhibit space, but don't hold your breath waiting to see it anytime soon.
http://nationalinterest.org/blog/paul-pillar/revealed-the-us-militarys-super-secret-deep-sea-spy-22473
