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A martian base on Earth

Nearly sixty years ago the US Army built a remarkable nuclear powered polar base in Greenland, the rival of anything conceived by Ian Fleming or George Lucas. Begun as an experiment in polar engineering it went on to revolutionise glacialology, continues to have a legacy in how we do, and don’t, build in polar regions; and most surprisingly may well influence the settlement of the solar system.

The concept of an Army base in the middle of the Greenland Ice Cap conjures up images of the hardships experienced by polar explorers. But Camp Century, 225 kilometres east of Thule Air Base in northern Greenland, was initiated in 1957 to demonstrate that technology would allow the construction and operation of a complete, reasonably comfortable, military base in a lethal environment. To help prove this two Boy Scouts, one American, one Danish, were invited to experience wintering over, at the age of seventeen and without any special Arctic training.

Søren Gregersen was the Danish Scout. “It was exciting, flying over the Atlantic to briefings in Washington DC, then a military flight northwards to Thule in the autumn of 1960; there we exchanged our scout uniforms for Arctic military clothes and survival gear. The vehicles which took us to Camp Century looked like light tanks with 6 seats in each. Behind nearly all of them were hauled sledges with various supplies, largely of fresh food. It took close to a day and a night and we had to follow a marked trail free of holes and crevasses; for many hours we saw only the endless snow-covered area, and were told that the ice thickness under us increased to close to 2 kilometres. After seeing just snow and the trail stakes for nearly 24 hours the excitement was high when many more stakes and about 15 two-meter broad escape hatches could be distinguished.”

Indeed there was not much to see of Camp Century, for it was built into the icecap itself; just one meteorology hut was situated on the surface next to a communication mast. A 400 meter long main trench and fifteen 100-meter side trenches had been cut to a depth of nearly 10 meters by Swiss snow millers, usually used for clearing deep snow from alpine roads. These tunnels were then roofed with corrugated metal arches and recovered with snow. Prefabricated insulated wooden huts were then built in the side tunnels for the living quarters and working facilities.

In all a network of 23 trenches were dug, covered; within which a little piece of prefabricated America was built in the high Arctic. At its peak the base housed 225 people, and as well as the living facilities, offices and shops they had a recreation hall, cinema and a library on hand in an effort to relieve the gloom of working in a tunnel for months on end. All this activity was heated, lit, powered and even provided with drinking water by a portable nuclear reactor.

Part of a project to provide Army bases with portable power stations, Century's reactor was slid across the snow in modules and assembled in 1960. An Army documentary recorded personnel unpacking the reactor and manually lowering the fuel rods into its protective pool. Once complete the reactivity was increased in stages and the progress announced throughout the base. After commissioning it proved an effective and reliable power source delivering up to 2MW, but the larger tunnels built to accommodate it were the first to reveal the weaknesses in the camp design.

Part of the motivation for a subsurface base, beyond simple camouflage, was to avoid the problem of snow accumulation; this is a challenge wherever structures are built on permanent snow fields and most of the current generation of permanent Antarctic snow field bases are now built as elevated pods on jackable legs, so as to rise above the annual accumulation. The Greenland Ice Cap can be particularly challenging, receiving in some places well over a metre of new snow a year. At Century the larger arches over the reactor protruded above the surface causing snow drifts to form on them; this extra load made some buckle and they had to be excavated and raised. Eventually it was decided to remove the reactor and its reliability was much missed by the camp when it left in 1964.

Wayne Tobiasson of CRREL started a long career in polar engineering monitoring the performance of Century. “It was learned the hard way that an elastic material such as steel and a viscoelastic, creepy material such as snow cannot, over time, share load. All the snow load is taken by the metal and that load can be far in excess of the load directly above the arch, since the snow alongside the metal densifies adding additional load to the unyielding metal arch.” Leading directly on from the Camp Century experience most trenches are now roofed over with flat material and snow allowed too drift over the top.

Tobiasson was also involved developing methods for casting snow into structures and foundations at Century. “Finely milled natural snow can be dumped into wooden shuttering, like concrete, where it rapidly sinters into a stronger material. However, today snow millers are not much used. Instead, natural snow is processed by multiple passes of heavy equipment to create a stronger material for foundations, roads and runways."

To compound the problem of accumulating snow Century also revealed how quickly the icecap would close-up the tunnels. It was expected and Century was planned to have a design life of ten years, but the tunnels started to change remarkably quickly. The tunnels had been created with undercut walls, in places by up to 2 metres, and after only two years a team of 50 personnel were taken up trimming back the overhanging snow as it crept ominously downward. The floors began to camber up into the trenches, distorting some of the prefab buildings; while the metal arches deformed above. The root cause of this increase in tunnel closure was due to warming of the surrounding snow from heat lost from the buildings in the tunnels. Subsurface structures are still used today, but following Century's experience they are most often used where heating is not required, for fuel storage, workshops for ice core research and ancillary buildings.

Another crucial polar amenity pioneered at Century and in current use at the US South Pole Base is the Rodrigez Water Well, named for the engineer who established Century’s water supply. While previously snow would be dumped into a snow melter on the surface, the “Rod Well” exploits the nature of the icecap to create a more convenient water source. Steam is injected into the snow, near the surface the snow is permeable and the melt water flows away, the steam nozzle continues melting a shaft into the snow until it reaches a depth where it is so compacted it becomes impermeable; approximately 36 metres. The melt water then forms a pool, and as further steam is injected the pools broadens and deepens. Water can now be drawn off for use, heat is continually added to gradually melt the bottom of the pool to make up the difference and the pool slowly descends into the icecap. Once the pool becomes too deep another well can be created nearby; an unexpected spin-off of this in Antarctica is that meteorites lying within the snow collect in the pond as it descends and CRREL researchers have invented devices to collect them.

For all its hard lessons on polar design though, Century's greatest and ongoing legacy has been in the field of ice core research, and the climate science it informs. Ice coring started at Century as part of CRREL’s ongoing research and the Century team succeeded in making the first coring all the way through the Greenland ice cap in July 1966.

Historian Janet Marten-Nielsen of Aarhus University in Denmark has studied the history of research in Greenland “The Century ice core yielded a unique and powerful window to the Earth’s past: by providing unbroken physical access to more than 100,000 years of history, the core imparted. Far greater, and far more direct, climatological detail than any hitherto known method”. Indeed the Camp Century ice cores are still part of the archive collected by CRREL

But as well as a helping found climate science, Century is developing another surprising legacy; one that could aid in the colonisation of the solar system. In 2008 Professor Charles Cockell from the UK centre for Astrobiology, led a British Interplanetary Society (BIS) design study for a Martian polar base, Project Boreas. “Camp Century provides us with a wonderful example of how a base can be built, in a lethal environment, with in-situ materials.” Building into the Martian icecap would hold many advantages. “You can build a bigger base; the water ice would provide excellent radiation shielding, protection from meteorites and possibly more secure pressure boundaries.” Boreas was also designed to have a nuclear reactor. “One of Century’s most practical lessons is how to handle portable fission power, and the amount really needed by a significant base.”

This may sound unlikely given Century’s fate, but it appears the Martian icecap might be easier to deal with. Despite being a substantial icecap it isn’t expected to flow particularly, and the only accumulation of snow is light fluffy Carbon Dioxide flakes that could be sublimed away with waste reactor heat. Indeed, in Martian even the ice sublimes, rather than melts, which could make construction much easier. Only time will tell, but it seems Camp Century's legacy may have only just started.