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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