South Pole Diaries 2001/02

   

   


Tuesday 22nd January

From John Storey.....

This morning I awoke to find an email had arrived from the good folk who make our Stirling engine. The gist of it was that the symptoms all seemed dreadfully consistent with the control software being in "test" mode, rather than to something more useful. In test mode, the engine just runs flat out all the time in an effort to prove just how tough it really is. The human equivalent is, I imagine, something like running a marathon at the South Pole. Fortunately we had got the computer control of the engine working yesterday, and it was a simple matter to change a parameter from a value of 45 to 2, and after that everything
worked perfectly. Even the circuits that control the speed of the fans, and hence the coolant temperature, sprang into life - as evidenced by a large square-wave on the oscilloscope. Duane was so stoked that he took a photo of the oscilloscope.

Meanwhile the Eurotherm temperature controller is vying with the Stirling engine for the title of smartest thing in the AASTO. (Duane and I aren't even going to enter the contest.) The Eurotherm's job is to monitor the room temperature and adjust the duty cycle of some exhaust fans in order to keep us at a comfy 20C. As air is exhausted from the AASTO, fresh air is sucked in through a vent. This air, being at -25 C (it will drop below -75 C later in the year), cools things down in a big hurry. Meanwhile, the Stirling engine is dumping between 2 and 3 kW of heat in to the room to make sure we don't get too cold.

The clever bit about the Eurotherm is that it not only looks at the current room temperature, it also looks at how fast it's changing and how far it's deviated from the ideal in the past. It then works out all by itself how long to keep the exhaust fans on, and constantly strives to improve its own performance. It's as if you had a graduate student working full-time just on this task. To an engineer such a thing is called an auto-tuning PID controller and, whilst they've been around for a while, it is a still a wondrous thing to see in action.

The morning was also cheered by some blue skies and sunshine, but sadly we were completely overcast again by lunchtime. The weather has been shocking this year.

At lunchtime the station manager handed me a small box with dangerous-looking signs on it saying "Oxidizing Agent" and graphic pictures of a ring of fire like tigers used to jump through at circuses. Yes! It was the magnesium perchlorate, carefully packaged up for us by a kindly soul in McMurdo and put on one of the inbound Hercules. We can now add some of it to Summit, and finally install the instrument on the roof of the AASTO.

Finding something to put the magnesium perchlorate in was not simple, as it attacks just about everything. If it were a person it would wear one of those T-shirts that say "Does not play well with others." In the end we settled for an old glass coffee jar as a container, with some fibreglass stuffed in the top. You can't go far wrong with glass.

After lunch we had a quick look at the Bassler DC3 that had arrived to pick up any of the marathoners who actually finished. These are an extraordinary aircraft, reborn out of an original 1930's airframe and fitted with modern avionics and turbine engines. Oh yes, and skis.

The Twin Otters also have skis, which they keep at more or less the right angle with respect to the snow when landing by means of bungy cords. It is not a system that inspires confidence, and would certainly not win any industrial design awards for styling. The DC3, on the other hand, has a small wing attached to the back of each ski, so that the skis "fly" at the correct angle. The pilot was very proud of his machine, and pointed out that it was better than a Twin Otter because it has a tail wheel rather than a nose skid, the latter having a tendency to punch up into the cabin between the pilots in the event of a hard landing.

Just before dinner the first of the marathoners began to arrive. We would have gone to welcome them except that would have meant missing out on a tour of the new station, so we didn't. The new station is scheduled for part-occupation next year. Already we are using the new generators, three 750 kW Caterpillar diesels that run on JP-8, just like everything else around here. The most impressive thing about the new station is the extraordinary effort that has been made to use all of the possible waste heat to warm the building. Not only the diesels, but even the lights in the greenhouse have glycol cooling loops running through them to feed numerous heat exchangers. As Duane has just completed a Mechanical Engineering degree at UNSW, with an emphasis on thermal design, he was in seventh heaven. (All right, he was stoked.)

All in all this was a very successful day. However, the Supervisor computer has now taken an unfortunate dislike to the keyboard we had teamed it up with, and refuses to talk to it. Although an intermittent fault was apparent from the beginning, the breakdown in the relationship now appears to be irretrievable. So now the Supervisor won't boot past the stage where it says "keyboard missing - press F1 to continue" - a suggestion so asinine it could only have come from the richest man on earth.

John

 

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