Computers, bodies warm up DOD's cold mountain

The Cheyenne Mountain complex near Colorado Springs, Colo., the Defense
Department’s underground nerve center for detecting missile launches around the
world, has a novel way of keeping its staff warm in the subterranean environment.

Nestled in a cavern fortress safe from earthquakes and nuclear explosions, the 1,500 or
so military and civilian employees who work in this hardened bunker are warmed by the heat
generated by the complex’s computers.

The complex inside Cheyenne Mountain, covered by about 2,000 feet of solid rock, has no
furnaces or heaters. Although the cave’s natural rock temperature ranges between 50
and 55 degrees, the complex’s computers help generate the heat needed to keep its
buildings at a comfortable 70 to 72 degrees.

The complex houses more than 450 PCs, 40 high-end workstations and 50 mainframes in its
15 steel-welded buildings, and takes full advantage of the cave’s internal
thermodynamics. But it’s not just the computers that generate the heat—other
machinery and body heat also contribute warmth.

In fact, with plenty of people and machinery operating in the same workspace, keeping
the complex heated is not a problem. The difficulty lies in keeping things cool.

“For the most part all we do is cool the buildings,” said Ben Borth, deputy
base civil engineer at Cheyenne Mountain. “We rely on body heat, computers and
industrial heat from compressors and rotating equipment that keep us at the temperature we

“Computers generate heat in a room and we are constantly bringing fresh air into
the room and circulating it with diffusers,” Borth said. “In some cases, if we
don’t have optimal circulation of the fresh air, then sometimes we have hot and cold
spots within a room.

“If the computers are distributed evenly and there’s good air flow in the
building space then there isn’t a problem,” Borth said. “Typically, there
is a problem when we have a concentration of computers at one end of a room.

“Years ago we had these huge IBM mainframes that put out tremendous quantities of
heat,” Borth said. “But as we replaced these mainframes with desktop computers
we started to see drops in temperature so we had to slow down fans and adjust diffusers to
reduce the amount of cooling.”

Cheyenne Mountain has 2,250 tons of air conditioning equipment to keep building
thermostats out of the hot zone. These “chillers” send cold water to mechanical
rooms in each of the 15 two- and three-story buildings, which convert the chilled water
into cold air.

“We know how much heat is being generated out of a given building and we adjust
the amount of air flow and incoming air conditioner temperature offsets the heat generated
by the people and the machinery,” Borth said.

DOD built Cheyenne Mountain in the 1960s at the height of the Cold War to serve as a
secure command and control center in the event of a Soviet nuclear attack against the
United States. The complex began operations in 1966.

The hardened bunker, the “office building” for personnel drawn from the North
American Aerospace Defense Command, U.S. Space Command and Air Force Space Command, is
impervious to the effects of electromagnetic pulses from a nuclear blast, shielding its
computers and electronic components from damage.

Cheyenne Mountain’s 15 buildings sit on 1,300 coil springs. The springs weigh a
half ton each and are designed to absorb the shock of an earthquake or nuclear explosion.
The shock absorbers can reduce seismic hits from 13Gs of force to just 1G.

Standard operating procedure in the early days of Cheyenne Mountain was to tie the
complex’s original vacuum-tube computers to the floor to cushion them from a blast
and prevent them from tipping over, Borth said. With the advent of smaller, more resilient
PCs, that practice has been discarded, he said.

Rock bolts—110,000 of them ranging from 6 to 36 feet in length—ensure that
the walls of the cave do not collapse onto the complex.

“These bolts allow the rocks to feel like there’s never been a hole dug
inside of them,” Borth said.

The mountain fortress is powered by multi-megawatt power plant generators, capable of
running a small town. The complex, which gets its water from an underground spring, has
enough food and water to sustain hundreds of people for more than a month.

Defense spent $142 million in 1961 to build the complex. The General Accounting Office
estimated that it would cost $18 billion to do the same construction job today.

DOD engineers used 1.5 million pounds of explosives to remove 690,000 tons of rock from
Cheyenne Mountain to excavate 4.5 acres of space for the complex, Borth said.

Stay Connected

Sign up for our newsletter.

I agree to this site's Privacy Policy.