The Cold War arms race between the United States and the Soviet Union produced many innovative ideas on how best to ensure the survivability of each side’s nuclear deterrent.

Among the stranger ideas that emerged was a concept proposed by what was then the Aerospace Corporation under a program called Golden Arrow—launched in 1964. While most concepts being studied at the time looked at mobility, one of Aerospace Corporation’s concepts was to essentially hollow-out a mountain in the Sierra Nevada range to create a super-hardened fortress that could ride out a Soviet nuclear first strike and deliver an assured retaliatory second strike. The concept never got off the drawing board, but many of the ideas were later considered for the subsequent MX program.

The idea came about because as the Cold War progressed, ICBMs became progressively more accurate. If a land-based ICBM were to survive a first strike, both the silo and the launch control center had to withstand a direct hit. As the Soviet Union became ever more technologically capable, Moscow developed weapons that could target America’s nuclear arsenal accurately. Something had to be done and the Pentagon was looking for ideas.

“The team believed that superhard, a form of deep underground basing, provided almost total survivability by burying ICBMs in tunnels and shafts deep underground with a minimum of 5,000 feet of hard granite top cover,” former U.S. Air Force missile officer and historian Steven Pomeroy wrote in his Auburn University PhD dissertation in 2006.

“Aerospace thought that the Sierra Nevada Mountains were an excellent location for a base because this range met the requirements for linear exits and granite composition. This required burrowing into a mountain but doing so provided a level of hardness equivalent to 15,000 pounds per square inch. Aerospace proposed a total force of 100 missiles stationed at three superhard bases.”

As Pomeroy described, the proposed superhard bases would have resembled a “spider's web inside a mountain” with miles of underground tunnels. “Missiles contained within a transporter launcher moved within spoke-like tunnels to launch locations near the mountain's outer rim,” Pomeroy wrote.

“By carefully locating launch positions one mile apart in ravines or ensuring that ridges protruded between openings, the terrain protected against bonus kills.”

Perhaps what was most unusual about the concept was that the missile launch positions were buried under solid rock and would have had to been dug out for use. Thus, to launch the missiles, a lot of prep would have been required. As such, it would have only been good for a retaliatory strike.

“Before the war, the launch positions remained covered by rock, which meant that if a superhard-based missile had to launch, special machinery first dug through the ground, after which the missile, which was stored on its launcher in a central storage facility, moved into position,” Pomeroy wrote.

“A cantilever mechanism anchored itself into the tunnel's rock foundation, and the other end extended out over the mountain's slope. The missile moved longitudinally along the anchored cantilever and erected into a vertical position. After completing final checkout, the missile launched. Digging out after an attack required a great deal of time, probably up to several days, which meant that reaction time was slow and there was no reason to use a superhard-based missile as a counterforce weapon. It was purely a countervalue, post- attack weapon, that is, it existed to destroy whatever was left of an enemy state after the initial salvoes.”

The weapon the Aerospace Corporation proposed for the system was equally enormous—weighing well over a million pounds—or larger than an Airbus A380.

“To bring military capability into line with cost, Aerospace proposed a huge new missile known as ICBM-X, a weapon with destructive potential that matched well with the cost of superhard basing,” Pomeroy wrote. 

“Developed under a separate Golden Arrow investigation for a new hardened and dispersed missile, ICBM-X had a massive 156-inch diameter (Minuteman I was sixty-six inches at its widest), an unspecified number of stages, a CEP of .16 to .20 nautical miles, thixotropic propellants, a gross weight of 1,100,000 pounds, and multiple independently targetable reentry vehicles (MIRVs).”

The ICBM-X would have carried more than 20 warheads—and would have been more than twice the size of the Soviet R-36M2 Voevoda/SS-18 Satan, currently the world’s largest ICBM. It was by far the largest ICBM ever proposed.

“Given a payload capacity of 24,000 pounds, this meant that it could have carried twenty or more MIRVs, a staggering number,” Pomeroy wrote.

The cost of the entire system would have been astronomical. Unsurprisingly, even during the height of the Cold War arms race, the Pentagon did not opt for this Death Star-sized system.

“Aerospace believed that it could not provide accurate cost figures for the super hardened ICBM-X weapon system,” Pomeroy wrote.

“But construction efforts alone qualified the proposal as monumental architecture and made other options look relatively cheap. “

Ultimately, the ICBM-X remained on the drawing board—it simply was not worth the cost.

Dave Majumdar is the defense editor for The National Interest. You can follow him on Twitter: @Davemajumdar.

Image: Creative Commons.