a modern Sno-Cat

Polar vehicles get ice traction

Moving large quantities of supplies around Antarctica - especially overland - can be a logistical nightmare. But recent developments in vehicle design have taken some of the heavy lifting out of getting equipment from A to B.

It was far too comfortable to be proper polar exploring. As I rested my coffee mug in a conveniently placed holder, adjusted the position of my heated driver’s seat and turned up the music on a six-speaker audio system, I looked out at the mesmerising Orvin Mountains of Queen Maud Land in East Antarctica that were rolling rapidly past the windows. I was driving back to the remote Princess Astrid Coast of Antarctica from the South Pole as part of a four-vehicle convoy having completed a 6000km round-trip across the continent to provide logistical support for a TV documentary project. At first glance, the vehicles we were driving appeared to be a regular 171hp Toyota Hi-Lux but with oversized wheels. Each tyre was 112cm in diameter, with a width three times that of a normal car tyre, and was inflated with such minimal air pressure, just 0.2bar, that it looked as if we were driving on flats. The extremely low ground pressure and greater surface area of the seemingly flat tyres allows them to ‘float’ over the snow surface rather than digging in and getting stuck.

Bigger tyres, better traction

This revolutionary technique for driving on snow was developed in the 1980s on the glaciers of Iceland and it is an Icelandic company, Arctic Trucks that has been pioneering the use of wheeled vehicles in Antarctica throughout the last decade. Gísli Jonsson, lead designer of the Antarctic fleet at Arctic Trucks, points out that in addition to big tyres there are many unseen modifications that have had to evolve along the way. “The main challenge is making space for a bigger tyre without interfering with the suspension or steering of the vehicle,” he explains. “The frame, suspension and drive train also need to be strengthened to deal with the extra loads that result from larger tyres.”

Two of the vehicles in our convoy were four-wheel-drive (4WD) but the remainder, including the vehicle I used, were a newly developed six-wheel-drive (6WD). It had a third driven axle with the effect that the two extra tyres provided up to 50 per cent additional flotation and traction, greatly increasing the load capacity.

Like other Antarctic vehicles, the modified 4WD and 6WD Hi-Lux feature an engine pre-heater that circulates warm coolant around the engine’s moving parts before ignition, special lubricant that freezes at a much lower temperature than standard and air intakes that are altered for snow conditions. Able to travel over snow at average speeds of 30km/h and with impressive range thanks to the extremely low fuel consumption of production 3L engines built to the latest EUR5 standards, the modified Toyotas mark a radical departure from traditional thinking on Antarctic vehicles. “They will not replace heavy machinery which will always be needed for towing cargo and jobs like that,” says Jonsson of the lighter vehicles. “But they can provide greater reach and access, significant fuel savings and more flexibility.”

Previously, ground transport around the continent has been a slow and heavyweight affair relying on bulldozers, tractors and plant machinery. Several science facilities isolated on the hard to access inland regions of Antarctica rely on overland tractor-trains from the coast for resupply. Arguably the most famous of these epic undertakings is the South Pole Operations Traverse (SPOT). Since 2005 the National Science Foundation of the US Antarctic programme has established a 1650km overland route between McMurdo station on the coast and the Amundsen-Scott South Pole station located roughly at the centre of the continent. Every year some 100 tonnes of cargo is transported along this route by a convoy of some of the largest tractors in production. The vehicles chosen for the job are Agco Challenger MT865s and the slightly heavier Case IH QuadTracs. Both machines use 91cm-wide rubber tracks to provide traction on the snow rather than wheels. The main difference between them is that the Challenger, which is specifically designed for using tracks, drives on just two belts, while the QuadTrac, which is converted from a wheeled model, has four belts, each one individually driven.

These 500hp, 20-tonne behemoths have proven successful at hauling vast loads over the Antarctic snow surface but at average speeds of just 8km/h. A return SPOT trip from coast to Pole currently takes around 46 days. Developments are under way to cut this time using ‘lead-follow’ technology. The aim of work carried out in recent Antarctic seasons by Carnegie Mellon University, Lockheed Martin and the US Army Cold Regions Research and Engineering Laboratory (CRREL) is to create a suite of robotic sensors that would enable unmanned vehicles in the SPOT tractor train to partially drive themselves by autonomously following a manned tractor at the front. The aim is to enable a reduced number of drivers to work in two shifts around the clock. “By running two shifts, you would almost halve the time to South Pole,” suggests Jim Lever, a mechanical engineer at CRREL.

Rolling resistance

Unmanned tractor trains navigating themselves by GPS across the continent might still be the realm of science fiction - just - but the use of the humble tractor in Antarctica has a long and distinguished history. In 1957, as part of the Commonwealth Trans-Antarctic Expedition, Sir Edmund Hillary’s party set out for the South Pole in three Massey Ferguson TE20 tractors. In tribute to this landmark expedition, Massey Ferguson set out for the South Pole again last year but this time in one of its newest production tractors, the MF5610. Interestingly, the decision was made to use wheels rather than tracks.

With no precedent in Antarctica of such a large vehicle operating on wheels, Massey Ferguson trialled a ‘twin-tyred’ version of its Antarctic-bound tractor on the glaciers of Iceland. It had four tyres on each of its two axles. Using two or three tyres on an axle is not uncommon on agricultural tractors but initial tests on snow weren’t promising. Test engineers found that to compress the snow in four tyre tracks rather than the normal two, the MF5610 needed more power and therefore more fuel for little significant gain.

As a result, Massey Ferguson turned to tyre experts Trelleborg. “The most important challenge was to assure at least 20km/h speed on the soft snow,” says Piero Mancinelli, research and development director of agricultural and forestry tyres at Trelleborg. “Grip, flotation and low fuel consumption were necessary all at once. Also challenging was to assure tyre integrity at such a low pressure as 0.5bar. To work at lower pressure than standard means to have tyres with a stronger carcass and bead resistance.”

Mancinelli explains that the difficulty in creating ever larger tyres is that while big wheels are capable of greater flotation, they also generate greater rolling resistance, which needs more power. The tractor might float over the snow, but its speed would be dramatically affected.

The breakthrough came when Trelleborg adapted an existing tyre with a double lug that operates on the ground at different times, progressively releasing higher traction when and where required. “We opted to adapt the tread pattern, reducing the height and rounding the tread at the shoulder,” describes Mancinelli. “This made the tyre better suited to run on soft ground.”

Trelleborg also developed a special rim profile, ensuring a safe bead position to prevent slippage and rim roll-off. “Not only did the tyres not freeze, but they remained soft ensuring reliability and driver comfort throughout,” summarises Mancinelli.

The Antarctic-readied MF5610 successfully arrived at the South Pole in December 2014, achieving average speeds of 8km/h throughout the 6000km return journey from the coast - which matches the speeds achieved by the larger tracked vehicles.

Tyre technology is simultaneously developing at the Poles in another way: fat bikes. Having first appeared on the market around 2005, fat bikes (as you might guess from the name) have extra-large tyres, wide rims and a frame with slightly altered dimensions to allow for enlarged wheels. The tyres are at least twice as wide as standard mountain bike tyres. This creates better grip and traction, but also allows for lower tyre pressure. Riders can use tyre pressures of less than 0.7bar to create the same flotation effect experienced by the modified vehicles. As a result, fat bikes have become increasingly popular in all kinds of terrain, including Antarctica. Staff at Union Glacier, one of two commercial bases on the continent, use them to get around the camp (see photo essay p46). In recent years there have been a number of cycle expeditions to the South Pole by fat bike, including one by British rider Maria Leijerstram in 2013 on a recumbent fat-trike.

As we approach the 60th anniversary of the Commonwealth Trans-Antarctic expedition, we should remember that Sir Edmund Hillary’s tractors weren’t the only vehicles involved. Sir Ed’s part in the adventure was to lay supply depots for Sir Vivian Fuchs’s team, which set out from the opposite side of Antarctica to traverse the entire landmass. The workhorse of Fuchs’s journey was the Tucker Sno-Cat. Half a century later, these iconic vehicles remain a firm favourite for Antarctic ground transportation and the Tucker Sno-Cat Corporation professes itself to be the oldest successful manufacturer of snow vehicles in the world. Then, as now, Tucker Sno-Cats employ four individually driven tracks rather than wheels. But whereas the Sno-Cats were originally built with steel tracks and later rubber tracks with steel cleats, the latest Terra 1600 Sno-Cats to be sent to Antarctica use tracks that are completely rubber. This greatly reduces the weight of the vehicle, making it much easier to transport and more fuel efficient.

The Tucker Sno-Cat features in one of the most memorable images of modern Antarctic exploration. Taken during the commonwealth Trans-Antarctic expedition, the image depicts one of the convoy’s vibrant orange Sno-Cats sitting precariously wedged between the walls of a crevasse. Its four tracks tilt at violent angles as if the vehicle is on the brink of slipping completely into the blue abyss below.

Even today, crevasses remain the biggest threat to ground transport in Antarctica. These are deep fissures that form in the thick ice sheet that coats the southern continent. They can be hundreds of metres deep and equally wide. They can form anywhere and are most usually covered by a relatively thin layer of snow and ice, rendering them completely unobservable from the surface.

Crevasse bars are increasingly fitted as standard on all types of Antarctic vehicle. These are simply tubular steel bars secured to the front of the vehicle to increase its length by at least a metre. The rationale is that the crevasse bars might arrest the fall of the vehicle into a crevasse so that it remains on the surface where it is easier to recover. If a vehicle disappears completely into a fissure, there is more likely to be catastrophic damage to both vehicle and passengers.

Ground penetrating radar

Another ubiquitous development is the use of ground penetrating radar (GPR). Every system used is made up of two parts; the antenna which travels over the snow surface to emit and receive small electromagnetic radar pulses at microwave frequencies, and the display unit which receives and analyses the returned data. Any subsurface disturbance or change in density shows up on the display as a discernible feature. However, interpreting which of these features might be crevasses is a skill made complex by the fact that three-dimensional data appears on a flat screen. The process is acutely vulnerable to human error.

To maximise the amount of time available to interpret the often vague and confusing data, the antenna is usually mounted on a long boom attached to the front of the leading vehicle. The modified Hi-Luxes have a 6m long boom made of tubular aluminium protruding from the front so that the GPR antenna travels over ground slightly ahead of the vehicle. However, even when the vehicles are travelling at very modest speeds of 10km/h, by the time a potential crevasse has been identified on the display, the vehicle is already on top of it.

Gísli Jonsson of Arctic Trucks argues that identifying specific crevasses isn’t the true value of GPR. “When we start seeing small crevasses, it doesn’t matter that we drive over them,” he explains. “But they are important as an indication that we are entering a crevassed area and that there might be bigger crevasses nearby.”

The lighter vehicles have the advantage of being able to safely travel over relatively thin bridges of snow and ice that cover crevasses. Larger vehicles run a greater risk of breaking through much thicker snow bridges. The SPOT convoy addresses the problem by sending ahead a Pisten Bully with a GPR antenna on a 10m boom. While the Pisten Bully is no featherweight, it weighs in at less than 10 tonnes, making it better than half the weight of any other vehicle in the convoy.

However, there are developments under way that might see this Pisten Bully vanguard replaced by a robot. Professor Laura Ray leads a group from the Thayer School of Engineering at Dartmouth College in the US that has created a 4WD rover-type robot called Yeti. Rising no more than knee-height above the ground and weighing just 68kg, Yeti is small enough to travel safely across any unseen crevasses but has the capability to haul GPR equipment across Antarctic terrain ahead of a convoy. Currently Yeti only collects the GPR data, which then needs to be examined on a display, but Professor Ray and her team are working on autonomous crevasse detection software that would enable real-time warnings of subsurface hazards. “What we’re trying to do with Yeti is obviously not eliminate the operator,” says Ray. “But you can send a robot out to pre-survey a route that you are intending to survey.”

Yeti has already successfully undergone trials in Antarctica with the SPOT convoy and in Greenland. The only drawback uncovered was the lifespan of Yeti’s military-rated batteries which generally ran out after around three hours or some 15km of travel. Ray’s team are already developing an improved version, Cool Robot, which is solar powered.

Solar power is particularly suitable for the polar regions where long overland journeys only occur in the warmer summer season when the sun is above the horizon 24 hours a day. So it is perhaps surprising that there is still no significant use of any renewable energy sources for ground vehicles in Antarctica. Numerous concept vehicles have arrived on the continent, been tested, failed and promptly disappeared. “The technology just isn’t there yet,” summarises Jonsson. “Renewable energy still can’t reliably produce the large amounts of power needed for large vehicles.” Until the technology moves on, vehicles in Antarctica must rely on aviation fuel or diesel.

This isn’t all bad news. Back in the cab of my modified 6WD Hi-Lux, fuelled by Jet A1, I use a dash-mounted GPS unit to calculate that our convoy will reach the safety of our destination within a few hours. Reaching for my coffee mug and reflecting on the astonishing distances we have covered without damage or injury, it feels like we may already be enjoying a golden age of Antarctic travel. *

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