Proton/UR-500 "Super" ICBM

[Delta Force]

The Proton is one of the world's most prominent heavy launch vehicle families. However, the rocket was originally planned as the UR-500 "super" ICBM, capable of delivering a 100 megaton warhead 13,000 kilometers away. That particular program was canceled due to the expense of building underground silos to house the massive missiles (Khrushchev quipped that they could either build communism or UR-500 silos), and the R-36/SS-18 Satan was selected to become the heavy ICBM of the Strategic Rocket Forces. A third stage was developed for the UR-500, and it became the Proton.

I'm wondering if anyone knows anything else about the UR-500, its planned warhead, and/or its planned silos. I've read that the launch pads for the Proton rocket were apparently constructed partially underground to help with development of the missile silos, but other than that there doesn't seem to be much more than general specifications for the missile.

 

[Michel Van]

The oldest story about the UR-500 ICBM
was to launch Nuclear warhead with 50 ~ 150 mega Ton load.

what killed the UR-500 concept was the gigantic cost of building the world biggest ICBM Silo.
With inner volume for ICBM of 50 meter deep and 8 meter in diameter
and that hundreds silos were needed.