Friday, July 6, 2012

Nukes on Ice

Those Magnificent Men and Their Atomic Machines

Nukes on Ice: ICEWORM and the Army's Quest for Strategic Nuclear Weapons

In the late 50s and early 60s, the US military faced a major problem. The Soviet Union had begun to deploy nuclear-armed ballistic missiles with intercontinental range. The ICBM was the dreadnought of the early Cold War: a radically new technology that made the previous methods of delivering hellfire, via cruise missiles and manned bombers, obsolete.

The US built its own ICBMs in response, Atlas and Titan, and eventually Minuteman. But, in the eyes of the US Army, these missiles had two major failings. First, they were deployed in relatively “soft” shelters that were vulnerable to a near-miss from a nuclear warhead, and only protected by the enemy's inaccuracy. Missile accuracy was only going to improve, and it was clear that, if the missiles remained as they were, the USSR would eventually be able to target and destroy them in a first strike. Second, and even more worryingly, Atlas and Titan were marked with a blue SAC stripe, which struck the US Army as completely unacceptable.

This question of ownership may strike the modern reader as a petty complaint, but it was a matter of the utmost importance to the Army. The 50s were the years of Massive Retaliation and nuclear everything, when the US built an atomic arsenal so we wouldn't need a conventional one. The Army's missile programs, like the Jupiter Medium-Range Ballistic Missile (MRBMs), were being taken away and given to the Air Force and NASA. The Army's budget had fallen to less than a quarter of total defense spending, and the service feared being reduced to security guards for missile bases. Or worse: according to some analysts, the Army's only real purpose was to be killed in a Soviet invasion of Europe, thereby ensuring the Soviets wouldn't be able to use nuclear blackmail to keep the US from intervening. Dying ingloriously did not appeal to the Army leadership as a military strategy.

Therefore, if the Army aspired to be more than a speedbump, they needed their own strategic nuclear weapons. The Army had tactical nukes in plenty, but it needed a way back in to the field of long-range, strategic missiles. Enter ICEWORM.

ICEWORM was proposed by the Army Engineer Studies Center in 1960. ICEWORM would consist of 600 “ICEMAN” Intermediate Range Ballistic Missiles (IRBMs) stationed in thousands of miles of tunnels to be dug under the Greenland ice cap. The ice would both keep the Soviets from locating the missiles, and act as armor even if they did. ICEWORM would, according to the Army, be less vulnerable than the Air Force's missile silos, have more secure communications than the Navy's Polaris submarines, and be more accurate and have greater yield than any of its service competitors.

The US Military in Greenland
The US military first arrived in Greenland during World War II, when American forces occupied the island to keep it out of German hands. Greenland assumed even greater strategic importance with the beginning of the Cold War, as it lies on air routes between the US and Europe, including western Russia. It offered a position for staging American bombers and reconnaissance aircraft heading towards Russia, and for detection of and forward defense against Soviet aircraft heading the other way.
Greenland was of such importance the US offered to buy it from Denmark in 1946. While Denmark was not inclined to sell, they were willing to allow the US to build military bases, and the first post-war agreement was signed in 1951. In a deliberate omission that later assumed great significance, the agreement made no mention of storing nuclear weapons at the base, either to permit or deny them.

Figure 1: Aerial View of Thule AFB

Working in Greenland was and is difficult. 81% of the island is covered by a thick ice cap, with only coastal fringes ice free. Temperatures in the capital, Nuuk, average -9 to 7 C. Greenland is so far north that the sun does not set in summer or rise in winter for months at a time.

But Greenland's critical location overrode these difficulties. The US military built three airbases, of which Thule AFB in the far northwest would be the most critical. The first American presence at Thule was in the 40s, but construction of a modern air base began in 1951 and was finished in 1953. In the event of war, American B-36 and B-47 bombers would stage through Thule on their way to targets in western Russia.

The US interest in basing nuclear weapons at Thule dated from before the signing of the treaty. Initially, the plan was that Thule could also serve as a rearming base for strategic bombers returning from strikes on Russia. Another possibility was suggested in 1957, when a retired officer of the Air Force proposed basing IRBMs in Greenland in an editorial in the New York Herald-Tribune, in what Denmark understood to be an official unofficial suggestion. To the Defense Department's annoyance, the Danes expressed a strong disinclination to see nuclear weapons on their territory.

However, while the Danes' might object in public, their views were less rigid in private. In November of 1957, the US ambassador to Denmark privately approached Danish Prime Minister H. C. Hansen, and asked if Denmark wished to be informed if the US stationed nuclear weapons in Greenland. Five days later, Prime Minister Hansen replied that he thought the ambassador's remarks did not “give rise to any comments from my side.”

The US correctly understood this to mean that the Danish government did not want to know what the US was doing in the far north. What they misunderstood was that, while the Danes were willing to overlook the clandestine storage of small numbers of weapons at Thule AFB, they were not inclined to permit a major, public presence of American nuclear firepower.

This was the background to Project ICEWORM: a strategic concern over the vulnerability of US ICBMs, a political need for the Army to acquire its own long-range missile capability, and an American misperception that the Danes could be persuaded to permit a large nuclear arsenal in Greenland.

ICEWORM began in 1960 with a study by the Planning Studies Division of the US Army Engineer Studies Center, the Army's equivalent of the Air Force's RAND Corporation think tank. The study proposed building a network of thousands of miles of tunnels under the ice, excavated as trenches and then covered over again. The tunnels would link together launch stations, each a minimum of four miles from any other and with at least three feet of ice cover, giving protection up to 30 psi overpressure. Overpressure is a measure of blast strength – 1 psi overpressure will shatter glass, 3 psi will collapse a wood frame house, and 5 psi will destroy all buildings save those made of reinforced concrete.

Six hundred ICEMAN IRBMs, enough to destroy 80% of the target list in the Soviet Union and eastern Europe, would be shuttled between launch stations through the tunnels, probably on trains. The network would be controlled by sixty launch control centers (LCCs), each with 100 psi overpressure protection. Small nuclear reactors would provide power to the LCCs and launch sites. The whole complex would cover 52,000 square miles, beginning 300 miles east of Thule.

The 30 psi protection of the launch sites would be less than the 300 psi of early Minuteman silos, but the real armor of the missiles would be their invisibility beneath the ice cap. The Russians would need an estimated 3,500 eight-megaton warheads to destroy the system after construction – or, if the distance between launch sites was increased to 9.8 miles, 550 100-megaton warheads. Not only that, but new excavation could be kept constantly ongoing, expanding to 2,100 launch points five years after deployment. The Soviets would never be able to build missiles faster than we could excavate new launch sites.

Figure 2: ICEWORM Launch Site

The ICEMAN missiles would be modified Minuteman ICBMs, shortened to two stages. They would have a 3,300 nm range, a CEP of 0.8 nm, and a 2.4 megaton warhead, potentially upgradeable to 4 megatons. The system would have a 20 minute response time after receiving orders to launch, or 40 to 60 minutes if under attack.

11,000 men would be required to operate, supply, and protect the system, including 400 Arctic Rangers and 200 Nike-Hercules SAM operators. The remote LCCs would be resupplied from Thule via ski-equipped aircraft.

This was a truly monumental engineering project, Ozymandian in scope. ICEWORM would have covered an area the size of Alabama - there are countries smaller than ICEWORM would have been. ICEWORM used sheer size to try to cope with the scale of the war it was intended to fight. It wouldn't have been a structure or base or even a city, it wasn't architecture; ICEWORM was geology, it was terrain. It was reengineering the entire landscape for human purposes.

Figure 3: Map of ICEWORM Deployment Area

Despite this, the Army estimated that construction would take only three years and a mere $2.37 billion ($17.25 billion today), with operating costs of $409 million per year ($2.98 billion). The primary technical difficulties were thought to lie in the difficulty of adapting both men and missiles to the extreme cold, but these seemed surmountable.

The Air Force and Navy, needless to say, decried the proposal as redundant with the Air Force's Minuteman ICBMs and the Navy's Polaris SLBMs, and vulnerable to attack by airborne forces. The Army's counterargument was that, compared to the Minutemen, the system was isolated from populated areas, reducing civilian casualties in the event of a Russian strike, and offered better protection than the Air Force's missile silos. Unlike the submarines, ICEWORM would be “on-station” at all times, more accurate since it launched from a fixed location, and, since it could use buried landlines rather than radios, would have more secure communications. Finally, the ICEMAN missiles would have greater yield and better accuracy than either of the main competitors. While difficulties were foreseen with the Danes, it was generally felt that they could be brought around.

Camp Century
If the Army wanted to deploy atomic weapons under the Greenland ice cap, it needed to know how to live there. In June of 1959, it started learning, with the beginning of construction on Camp Century, a research station built under the ice 150 miles east of Thule AFB.

This was the Army's second sub-ice research station, and the first to be occupied year-round. Construction was finished in October of 1960. The site was forbidding, a plateau two kilometers above sea level, blown by winds that occasionally exceeded 125 mph. The mean temperature was a balmy -10 Celsius, occasionally dropping as low as -70.

Figures 4a and 4b: Camp Century Under Construction

Three giant Swiss “Peter Plow” rotary snow blowers dug trenches in the snow. The Peter Plows could excavate 1200 cubic feet of snow per hour, and could blow snow clear of the trench even from its bottom. Once the trenches were excavated, the Army workers covered them with sheet metal roofs and buried them under snow. Then, the Army erected prefabricated wood frame buildings in the tunnels.

The finished camp featured a theater, infirmary, scientific laboratory, chapel, barbershop, and a small nuclear reactor from the Army Nuclear Power Program. To minimize melting, the buildings were kept several feet clear of the trench walls and air shafts were dug from the surface to introduce cooler air. Camp Century was inhabited year-round by up to 200 people, including a visit by two boy scouts in 1960.

Figures 5a and 5b: Interior of Camp Century

The camp reactor, PM-2A, was a 1.56-MWe reactor operating on highly enriched uranium. It was the first modular reactor in the world, weighing only 400 tons, disassembled for transit and reassembled in situ. Built by ALCO Products, Inc., at the time it was the most expensive cargo that had ever been shipped from Buffalo Port, and accounted for $5.7 million of the camp's $7.29 million construction cost.

PM-2A was one of a series of pressurized water reactors the Army Nuclear Power Program was developing to power remote camps and bases such as the DEW line RADAR sites. It used 37 plate-type fuel rods arranged in a 7x7 grid with the corners missing. The fuel plates were made of highly-enriched uranium dioxide and beryllium carbide in a clad stainless steel matrix. Europium oxide plates were added to five of the fuel rods, so that they could be used as control rods.

In addition to electricity, PM-2A would also produce 1,000 lbs. of process steam per hour that could be pumped into a “Rodriguez Well,” a shaft in the ice with a cavity at the bottom. The steam would melt ice at the bottom, which would then be pumped back up, providing up to 10,000 gallons of fresh water daily.

But first PM-2A had to be made to work, and bugs plagued its early operations. A manufacturing error in the vapor container delayed reactor powerup for a month. More worryingly, radiation levels in the reactor tunnel were significantly higher than design limits. The engineers had to jury-rig additional shielding by stacking lead bricks on the primary shield tank and spraying the tunnel walls with boric acid. With these modifications, the reactor finally reached full power in March of 1961, only to be shut down again in August for three months for repairs to the turbine generator. This repair finally cured the reactor's jinx, and PM-2A proceeded to set several records for continuous operation, including one of 2,502 hours.

Figure 6: PM-2A Nuclear Reactor Being Loaded

The focus of Camp Century was deep ice drilling, and its ice cores are still regularly cited in scientific journals on climatology. But, while ICEWORM was never mentioned in public as a reason for Camp Century, the camp also served to develop the necessary construction techniques. Camp Century's “Main Street” central tunnel was identical to the proposed ICEWORM tunnels in dimensions and construction, and the PM-2A reactor was very similar to the systems intended to power the LCCs and launch sites. Camp facilities even included a small U-shaped underground railway, ridden by a truck fitted with train wheels.

Figure 7: All the Comforts of Home

The Multilateral ICEWORM
By early 1962, interest in ICEWORM had shifted. The Defense Department was disinclined to add a fourth leg to the nuclear triad just to give the Army something to do, but ICEWORM seemed like it could be used in a different way: to reassure Europe.

European confidence in the willingness of the US to defend Europe had been shaken by the development of ICBMs in the late 50s. Before Sputnik, the US enjoyed clear strategic superiority over the Soviet Union; in a nuclear war, the US might not win, but it could at least avoid losing. Therefore, the US could be relied on to respond with nuclear weapons if Russia invaded Europe. European countries could rely on the American nuclear umbrella for protection, and did not need their own deterrents.

The development of ICBMs shook that confidence. The USSR, it was thought, now had the ability to absorb an American strike and still reply with a devastating counterblow. (We now know the ICBM threat was severely exaggerated, and would not materialize in fact until the late 60s, but at the time this was not widely realized.) In the event of invasion, would the US be willing to risk its very existence to save western Europe? Memories were still fresh of Eisenhower's seemingly blasé response to Khrushchev's nuclear threats in the Suez Crisis. If Soviet tanks crossed the border, and the Russians threatened nuclear war if the US intervened, would America actually live up to its commitments? Should the European nations seek their own nuclear deterrents – or even a separate peace with Russia?

In order to address these concerns, the US sought ways to “share” its nuclear weapons with NATO. It would be illegal under the McMahon Act for the US to actually transfer ownership of nuclear weapons, but as long as the warheads themselves remained legally American, the US could share control of the launch system through joint crewing and planning and dual-key launch control. The Defense Department presented two options for joint operations of strategic nuclear weapons: a force of mobile Medium-Range Ballistic Missiles (MRBMs) based in continental Europe, or a NATO Multilateral Fleet of Polaris-armed submarines or ships.

The Kennedy administration was unhappy with both plans. They wanted to both share the deterrent with Europe, and to simultaneously maintain their control over the West's nuclear arsenal. Aside from control issues, they were concerned the MRBM program would lead to West Germany acquiring a nuclear capability, which was a wholly unacceptable proposition. A third suggestion, to place five American Polaris submarines under NATO command and planning but retain American control over launch authorization, seemed unlikely to relieve Europe's concerns.

It was here that Assistant Secretary of Defense Paul Nitze remembered ICEWORM. In December 1961, Nitze sent a memo to the State Department's Policy Planning Council requesting they look into ICEWORM as a possible solution. A small State-Defense task force was set up in January of 1962 to study the concept. Critically, the group included six State Department personnel, one Navy officer, and two Army officers, but no one from the Air Force.

The group concluded that ICEWORM was relatively secure from destruction, offered a reliable second strike capability, and that it would be easier to set up as a multilateral force than either the mobile MRBM concept or the Multilateral Fleet concept. First, unlike MRBMs, it would not be based in politically sensitive areas. Second, it would be easier to solve the problems of mixed force units, such as finding a common language, in ICEWORM's compact, stationary LCCs than on ships or roving missile batteries. However, unlike Polaris, ICEWORM's Greenland base would be vulnerable to conventional invasion, and the difficulties of building and operating the force in the severe Greenland weather would be substantial.

Nonetheless, the group concluded that ICEWORM held the edge, at least over the mobile MRBM force. While the Air Force wasn't happy, the Navy was willing to be persuaded to view ICEWORM as a complement with rather than a competitor to their own Polaris missiles. The political difficulties with NATO and the USSR were thought to be significant, but not insolvable. The report was extraordinarily optimistic with regards to Denmark. After all, they reasoned, the Danes' stated non-nuclear policy might not apply to Greenland – hadn't the US been basing atomic weapons at Thule for years, without objections?

The Worm Turns
Despite all this planning and study, the US never actually broached ICEWORM to the Danish government, let alone the Danish public. If it had, the program would probably have ended sooner. There can be no question that the Danes would never have consented to the ICEWORM scheme. While they were willing to overlook a few nuclear weapons held in storage bunkers at Thule, they were never going to agree to turning the northern third of Greenland into a gigantic missile base.

But it did not come to that; the Danes did not kill ICEWORM. ICEWORM's fell to the same thing that would have been its strength: the ice.

By 1962 Camp Century had been operating for two years. By this time it was apparent that the ice shifted more than the Army planners had realized, and considerable effort was needed to keep the tunnels from pinching shut. The integrity of Camp Century's reactor tunnel was suffering, forcing repeated reactor shutdowns to repair the roof. More than 120 tons of ice and snow had to be removed from the tunnel walls each month to keep them open. And Camp Century had only three kilometers of tunnels; ICEWORM would have had thousands, requiring the removal of millions of tons of snow per year.

Budget cuts to the the Army's polar research and development program reduced the camp to summer occupancy after 1963, and the PM-2A reactor was removed. By 1966 Camp Century was abandoned entirely.

By that time, ICEWORM was long gone. It had been a long shot for the NATO nuclear role in any event, which was eventually filled by the Navy's Multilateral Fleet proposal. The Kennedy and Johnson administrations pushed the MLF, until it too foundered in 1965 due to general half-heartedness and disinterest.

While ICEWORM fell into obscurity, the essential idea – securing nuclear missiles against attack by shuttling them between different launch sites – remained, and would be revived in the 70s and 80s as the MX Racetrack. This time the Air Force were the sponsors, and the scheme would last considerably longer, but Racetrack faced many of the same problems as ICEWORM: the local population was resolutely opposed to the idea. The Navy was opposed to it as competition for its own Trident SLBM. And there were severe questions as to whether it could work at all, although Peacekeeper's failings lay in its inability to guarantee concealment from Soviet satellites rather than issues of ice physics. And, like ICEWORM, Racetrack would never be built – Peacekeeper would go in the silos, just like Minuteman.

It was not until 1997 that Denmark and the public learned of ICEWORM, when the Danish Institute of International Affairs (DUPI) accidentally discovered it while doing archival research for their book Grønland under den kolde krig, Greenland during the Cold War. The discovery provoked considerable consternation in Copenhagen – it had been known since 1968 that the US had based nuclear weapons in Greenland, but the scale of American ambitions had not previously been realized. But the level of outrage was muted by the passage of 35 years, and the matter rested there.


Baldwin, William C. History of the US Army Engineer Studies Center. US Army Engineer Studies Center, 1985.
Deployment of NATO MRBMs in the Greenland Icecap: The US Army's Iceworm Concept. Found in Grønland under den kolde krig (Greenland during the Cold War), Danish Institute of International Affairs, 1997.
Petersen, Nikolaj. “The Iceman That Never Came.” Scandinavian Journal of History, Vol. 33, No. 1, 2008.
Weiss, Erik D. “Cold War Under the Ice: The Army's Bid for a Long-Range Nuclear Role, 1959-1963.” Journal of Cold War Studies, Vol. 3, No. 3, pp. 31-58, Fall 2001.

Camp Century
Clark, Elmer F. Camp Century Evolution of Concept and History of Design, Construction, and Performance. US Army Materiel Command, Cold Regions Research & Engineering Laboratory, Technical Report No. 174.

PM-2A and Army Nuclear Power Program
Belson, John D. Military Nuclear Power Plants. Air Force Weapons Laboratory, Research and Technology Division. Technical Documentary Report No. WL TDR-64-25.
Suid, Lawrence H. The Army's Nuclear Power Program: The Evolution of a Support Agency. Contributions in Military Studies, No. 98. Greenwood Press, 1990.

Imagery Sources

Figure 1: US Government. Found on wikipedia.
Figure 2: US Government.
Figure 3: Created by author as modification of base image. I've forgotten where I found the base image, except that it was either public domain or Creative Commons Licensed.   Image is hereby released under an Attribution-Noncommercial-Share Alike 3.0 Creative Commons License, on the condition that any page displaying this picture must contain a link to this page.
Figure 4a, 4b, 5a, 5b, 6, and 7: US Government. Screen capture taken from Progress Report #6: Camp Century.


  1. Hi Mark,

    Excellent piece! I believe this adventurous project was a nuclear bridge too far, given the knowledge and limited experience with such small nuclear power plants. The SL-1 incident, with the explosion and meltdown of a similar small reactor, only one year after Camp Century's PM-2A went critical shows that a catastrophe with such small plants was only a question of numbers and odds. I'm glad the Army Nuclear Power Program, after activating eight such reactors, halted the program in 1977. It would be great if you wrote a report/analysis about the SL-1 incident (see my last blog) and the ANPP program. Reading your other posts, I'm sure it would produce an excellent read.

    Keep up the good work!

    Dirk Rijmenants

    Cipher Machines & Cryptology

    1. First, thank you for saying so.

      Regarding ANPP, I'm not so sure. First, if you're going to have an accident, the middle of Greenland under a ton of ice - or in the middle of remotest Idaho - is one of the best places to have it. Second, these miniature reactors had the advantage that there just isn't that much radioactive material in them compared to a central station power plant, so the consequences of an accident would be proportionately less - PM-2A was about 2 MWe; a modern reactor is about 1,000 MWe. Third, although I'm not sure if ANPP went this route, small reactors have some significant potential safety advantages - it's easier to dispose of waste heat etc. if there's just less heat to deal with. I guess what I'm saying is, we did a lot of... less than wise stuff back in the day, and this ranks pretty low on the list. (Try Googling "Aircraft Nuclear Propulsion").

      Ultimately, the real problem with these mini-reactors was that there just wasn't much point to them. Somebody called it "a solution in search of a problem"; that seems like an accurate description to me. If it's not even cheaper than diesel, why bother?

      Regarding an article about SL-1, maybe at some point, but at the moment I have a bunch of other projects I have to get through first.

      Anyway, thanks for reading!

  2. Thanks for your feedback, Mark.

    I agree that those small BWR's have some interesting properties and since they use water as moderator, overheating or lack of water automatically decreases the reactor power or even halts the fission, a major safety plus. However, the pioneering work in the 1950s was one with a pretty dangerous learning curve. Even today, small power plants, designed with current technology and knowledge on safety, still provide a viable alternative in remote and hard to reach places.

    I believe that it was a wise decision from ANPP back then to halt the small reactors program, not only for economical reasons. They weren't mature enough and imagine they became popular and wider spread, and accidents would occur in not so desolate places (the SL-1 incidents still was pretty polluting). Reminds me of those RTG's that seemed a "safe" alternative for lighthouses. History has proven otherwise and they are now a mess to clean up.

    Don't get me wrong, I'm a supporter of nuclear energy. If properly exploited, it’s economically and environmentally the best solution to feed our greed for energy. Unfortunately for the environmentalists, there's no alternative, and they love their electricity just as much as the pro-nuclears.

    Sadly, although nuclear energy in itself is very safe and – yes - also clean, the lessons were often learned the hard way. Today, we’re good in it! However, the biggest problem now is not technology, but the human factor. Chernobyl and Fukushima were perfectly avoidable. However, profits, rigid bureaucrats, corporations deaf for scientists, and short term views undermined safety more than once, giving unjustified support to the opponents of nuclear energy. I’d say, if you want to take action, do it against the people who misuse it, not against the technology. It’s like blaming the plane for the plane crash while the pilot fell asleep.

    Thanks for sharing!

    1. I hear what you're saying. But I guess I'm just conditioned by all the reading I've done about stuff like Project Plowshare or the Aircraft Nuclear Propulsion program - after something like that, sticking a couple of mini-reactors in the frozen north seems positively mundane!

    2. You're right. The four nukes of the B-52 crash at Thule were much more poluting than the PM-A2 could have been if it exploded. It's hair raising how many nuke carrying planes came down during, and even after Chrome Dome. Likewise, many reactor driven subs never came back up, or were just left corrosing away. Despite some idiots inventing exotic ways to contaminate earth, and contrary to general belief, nuclear reactors are pretty safe today and, from that point of view, the SL-1 is definitely only a little hick-up. In the end, even those nuclear-free-policy Danes eventually agreed on planting a base and reactor on the holy Greenland and only the B-52 fall-out (both literally and figuratively) gave them a serious indigestion.

      I hope the Atomic Skies blog name wasn't inspired by operations like Head Start or Chrome Dome ;-)

    3. The name Atomic Skies was actually inspired by the Aircraft Nuclear Propulsion Program. (And just the whole atomic optimism, Jetson-future thing.)

      I know, intellectually, that ANP was a bad idea. But an atomic-powered airplane is just so cool that I can't be objective about it.

    4. Btw, I stumbled onto a blog that might interest you, called Nuclear Secrecy (if you haven't already discovered it yourself). Like yours, and interesting read.

    5. Alex Wellerstein is a personal hero of mine, I've been reading his blog since way back. : )

  3. That doesn't surprise me. A fascinating "archive rat"!

    To understand your blog's title, I downloaded the APEX documents. Well, I knew that some had extraordinary ideas about how to use nuclear energy, but those documents stunned me :-O

    Let's call it the 50's optimism for a fascinating new technology, untamed like a Mustang. It reminds me of all those wonderful 50s and 60s documentaries and public movies about nuclear energy and atom bombes. I tend to believe that we, the general public, has since become a bit smarter :-)