The Cold War was a strange time. Any economist will tell you that nothing makes human beings spend money irrationally and excessively quite like strong emotion, in this case fear. Some absolutely absurd, astronomically expensive plans to one-up the Soviets were being floated at the time...many of which were actually funded and built.
The "Beetle Mobile Manipulator" was designed to work on the engines of nuclear powered bombers. Accordingly the cockpit was shielded by 30cm of lead. Yes, this was piloted directly from within the robot rather than remotely. This is the closest real world equivalent to Pacific Rim.
Built on the chassis of a M42 40-mm. gun carrier, it was not terribly fast (electric drive speed was 15 feet per minute, using gas it could go a whopping 10mph) but it's a giant fucking robot. Powered by an onboard nuclear reactor, no less! You can bet the fellow inside was some mixture of thrilled and terrified, peering out from several layers of radiation hardened glass.
It was scrapped not for any of the obvious reasons. Not because no nuclear bombers ever materialized, not because of its impracticality and high cost. Rather because it spent most of its time broken. It was a monstrously complex machine, with over 400 miles of wiring. Just when one issue was fixed, another would manifest.
The whole upper body could extend or retract vertically on hydraulics. The torso, weighing 50 tons, can rotate freely. Each of its arms has the same number of joints and degrees of freedom as a human arm, save for the rudimentary end effectors. The cockpit could be closed off entirely from the outside air, life support then supplied from an 8 hour bottle of Oxygen and a CO2 scrubbing system similar to those found on submersibles.
Dextrous enough to handle an egg without cracking it, the Beetle was surely capable of its intended job, though it would never be used that way. As nuclear bomber prototype projects wound down, the Beetle found itself without a purpose. The idea was floated that it could be used to clear large debris and rescue survivors after a nuclear blast, though how to get the damned thing cross-country was a big question mark.
Smaller variations on it were designed which could be air lifted, and which were remote controlled so they didn't have to carry so much lead shielding. These mini-Beetles may have solved the transport and other practical problems of their larger predecessor, but mercifully the conditions never came about for which they were designed.
Is there any place for a giant robot in today's military? How tempting it is to find or invent one! But seldom is there any use for the robotic manipulator arms, and everything else the Beetle was capable of could also have been done by a tank. With a lower profile, too: The Bettle, jutting up from the rubble, would make an easy target.
As it stands, the Beetle was just another crazy product of an even crazier time. A time when nuclear bomb propelled warships were on the table. In the modern era, there is little conceivable use for a piloted nuclear powered giant robot unless Kaiju show up. A man can hope!
Edit: Air Force, not Navy. I'm stupid