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Situated 3km beneath the ice of Antarctica is Lake Ellsworth, one of many sub-glacial lakes so far discovered in this desolate region, each with its own biological habitat.
However, exploring a sub-glacial lake the size of Lake Windermere remotely, and with no risk of contamination, is presenting scientists and engineers with a considerable physical and technological challenge.
As part of the Natural Environment Research Council funded Lake Ellsworth Consortium’s project to survey, measure and sample this unique environment, a 5m long probe has been designed and built at the National Oceanography Centre in Southampton. Manufactured from high grade titanium to ensure maximum sterility and strength, the probe will collect water samples at different lake depths and will also capture the top layer of sediments at the lake floor/water interface.
Later this year, a team of scientists and engineers will take three days using state of the art hot water drilling technology to melt a 360mm diameter borehole through the overlying ice. They will then lower the probe into the 150m deep lake to measure and sample the water, followed by a corer to extract sediment.
Ray Edun, Emlyn Jones and Geoff Shannon make up the precision engineering team at the National Oceanography Centre’s Liverpool facility that initially produced eight close tolerance titanium water sample bottles for testing and evaluation.
Forty more sample bottles have since been produced successfully from titanium grade 5, chosen for its combination of strength and excellent corrosion resistance. Now, with the project on schedule, Lake Ellsworth is expected to be the first of Antarctica's 387 known sub-glacial lakes to be sampled directly using space industry standard 'clean technology'.
Components for the 50m/litre capacity water sample bottles have been produced using carbide tooling on machine tools supplied by XYZ Machine Tools, including two 15kW/8,000rpm 710 VMC vertical machining centres equipped with Siemens CNC, a 3.75kW/5,000rpm ProtoTRAK SMX 3500 CNC/manual bed mill and a 7.5kW/2,500rpm ProTurn SLX 425 CNC/manual lathe.
All four machines are equipped with easy to program control systems: the ProtoTRAK CNC/manual control making use of ‘plain English prompts’ while the Siemens ShopMill’s simple conversational programming means the sequence from drawing to finished part takes the minimum of operator keystrokes.
“We don’t usually undertake production work here in Liverpool,” says Dave Jones, associate head of mechanical engineering. “Our engineers are usually focused on small batch, R&D and prototype items – which is why we opted for the XYZ machines. However, manufacturing all these sample bottles in house has guaranteed excellent quality control.”
Conformance to the close tolerance specification is crucial in terms of the project’s commitment to avoiding any possibility of accidental contamination or the introduction of microbes into the lake. On final assembly under clean room conditions of the probe itself, the fully tested and sterile water sample bottles will sit neatly between two pressure casings, one casing containing instrumentation and the other the power and communications systems.
The Lake Ellsworth Consortium is hoping that the exploration will yield vital clues about life on earth, climate change and future sea-level rise. According to its leader, Professor Martin Siegert from the University of Edinburgh, it is a benchmark in polar exploration, as it is only now that it is possible to drill through Antarctica's thickest ice and to collect samples without contaminating an untouched and pristine environment.
XYZ Machine Tools