The BAS ship RRS Ernest Shackleton is now heading north after another busy summer season at Halley - the last before the beginning of the construction of Halley VI next year. For the Halley VI team this was our last chance to complete testing and start preparing the station for construction - and there was a lot to do.
Martin’s new vehicle fleet were quick to get stuck into the job of moving cargo from the ship to the station. Soon after they had been offloaded they took over the job of relief from the snocat fleet. We will be relying on these huge vehicles next season to move all the construction materials from the ship to the station, so we were pleased to see they were up to the task. The Challengers where able to pull up to 48 tonnes at speeds of 20km/h, compared to 10 tonnes at 10km/h for a snocat. The John Deere tractors proved invaluable as multipurposes vehicles, pulling cargo, lifting containers and palettes of cargo or grooming roadways.
With relief out of the way we were able to turn our attention to the summer work programme. In order to reduce travel times next season the garage and summer accommodation buildings were to be moved closer to the rest of the site. With each building weighing 60 tonnes, the new vehicles again proved useful, but even this was just a warm up - the big test was yet to come.
The new station relies on a series of ski based modules, each of which can be towed across the ice shelf. To ease construction the new station will actually be built at the site of Halley V, then towed 15km away to its final destination. Of course we need to be sure that the vehicles will be capable of towing the structures we are going to build, and with modules weighing up to 140 tonnes, that’s no small feat.
To be sure they were up to the job we built a second steel sledge, to join to the smaller one that was built last year for the initial vehicle testing. These sledges have the same sort of skis as the modules will, so they represent a similar challenge to move. The test sledges were loaded with everything we could find to get them up to weight then towed over a variety of surfaces (fresh snow, groomed snow, heavily compacted snow). Once again the new vehicles proved themselves to be up to the task - at their peak they were pulling a load of 155 tonnes!
On a completely different scale, 1:50 models of the current Laws platform, along with three of the Halley VI modules were brought in this year to study the effect of snow accumulation on the new base. The data will be used to complement data from numerical models and will help us to understand the snow management that will be required at Halley VI. The model of the Laws platform showed us that the wind tails produced by the small models accurately represent what actually happens on station. The Halley VI models suggested that the more aerodynamic shape of the new buildings will lead to smaller wind tails than are produced at Halley V. A second positive benefit is that the legs of the new buildings appear to remain clear of snow, which should make the jacking procedure more straightforward.
With the Halley V site due to become a construction site next year we spent some time marking out the areas where the building work would take place, as well as where the completed modules would be parked up for the winter once they were finished. At the same time the Halley VI site was also being marked out. Next year the foundations for the masts need to be placed so the locations of many of the buildings needed to be calculated.
This gave us an opportunity to visit the site that will become Halley VI over the next few years. At present it is flat ice like the rest of the ice shelf, with the only distinguishing feature being an automatic weather station that is collecting data on the new site.
Finally there was a great deal of planning and preparation work to be done - removing unnecessary stock and working out exactly what would happen to all the equipment that is currently on base. Rod Downie was visiting from the Environment Division to look at the amount of waste that would be generated by the removal of Halley V, so that we can look into recycling as much of it as possible.