South Pole Diaries 1997/98

   

   


Thursday 20th November 1997 - Calm

From John Storey.......

It is recommended that, when in Antarctica, you try to learn something new. I'm sitting here learning "Pine". Mcba says is better than "mail" and he's right. Antony showed me how to switch it on. It doesn't use the mouse but you can move the cursor round with the arrow keys, just like in the good old days. If you get 4,000 copies of this message, or if it turns out to be one long line of 1,728 characters - sorry.

How wonderful it is to have the wind down to 10 knots - for the first time since we arrived. Suddenly it's quiet and peaceful, and it's possible to potter around outside without being instantly frozen stiff.

After I'd dashed off my message last night, I of course rushed out to help Ant clean the NISM. He had been so keen to get started on it that he'd gone and got a Sprite, and in fact I met him on the way out to the MAPO building. I guess he must have driven via Dome C as he was only just arriving when I got to MAPO; Ant assures me that it was by far the quickest way. Anyway, together we cleaned the NISM - a truly disgusting task not for the faint-hearted. By the time we'd finished we didn't have much enthusiasm left for anything, so we went and wrote postcards. (Actually we took the Sprite for a quick fang first.)

Ev has a nice little digital camera, and has taken shots of all the damage caused to the AASTO by the propane leak. He intended to put them on the net so that y'all could see it with your own eyes. Unfortunately, there seems to be an incompatibility between his Windows 95 compatible camera and his Windows 95 compatible computer, and the images won't transfer. I don't know much about PCs, but I suspect he's just used the wrong font when he set up the C:> system/cam/bios.$ram.config files. Or it might be just that his PC has the wrong serial number.

Additional entertainment here comes from the fact that they've started digging out the cargo arches in preparation for rebuilding South Pole Station. This has consisted mainly of using the bulldozers to carve great gouges in the landscape (snowscape?). However, they've discovered that the snow is compacted into ice on the side where the aircraft are, and is too hard for the biulldozers to penetrate. We offered them a jar of Brown Slime #1, but this was politely declined. Instead, they're using *dynamite*. There's a muffled bang and then snow all over the place. Over the next few weeks the station will come to resemble something like it was in 1973, before 25 of years of snow-fall buried it. Should be interesting.

This morning we busied oursleves installing the heavy-duty stepper motors in the NISM and MISM. We did the NISM first since, it was indoors and in bits. This was a moderately straightforward exercise, once we recalled the bizarre attributes of the stepper motor code. Our first problem was to be absolutely sure of the stepper motor rotation direction, since even the Tektronics oscilloscope was unable to calculate it from first principles. (The Fluke multimeter took a punt, but got it wrong.) Characteristics of the code that made this exercise unusually difficult include:

  1. Calibrate rotation direction CW or CCW? Goes CCW regardless of what you type.
  2. The limit switches only work if you hit the one the computer thinks the motor is travelling towards. This is actually very nasty, as if the motor is going the other way it won't stop until it tears the cables out. Things that can make the motor go the wrong direction include:

    a). Me, especially if taking advice from the Fluke.
    b) Running the motor at a step rate close to the fundamental resonance
    c) Having one phase fall off.

I suspect we're running an old version of the stepper motor code, as I'm sure these things were fixed a while back

As expected the rotator works beautifully, and the stepper motor couldn't care less if the thing is balanced or not. Calculation shows that if the rotator stalls (eg if it hits a limit switch that the software ignores), it will exert a lateral force of 2,000 N on the gearbox and on the teeth of the aluminium ring gear. I've put my money on the ring gear stripping; the Tektronics has backed the gearbox shattering at 3 to 1. No one is prepared to put any money at all on a non-destructive stall.

We're running the motor at the minimum current that I'm confident will overcome the detent torque (oh, how I loathe stepper motors), namely the same current that we ran the old motors at. (This also saves us having to change the circuit boards.)

Today all the rest of the boxes came; ie Abu, the 386 super replacement, the AASTO manual, and various goodies. All we await now are the replacement Sonnenschweins, coming as hazardous cargo (and they don't know the half of it!)

The Good Will power supply (seriously) that powers the super and charges the instrument batteries when the TEG is down appears to have gone belly-up. The left-hand 30V supply won't go above 15V and the right hand supply has "bad" written across the meter and in any case doesn't work at all. Only the 5V section seems to still work. However, today the super started spontaneously booting itself every few minutes for no good reason, just like it was doing last January. There are times when good will on its own is not enough, and the super is now powered up from a Lambda 20V, 3.3A supply. it will be interesting to see if the super continues to work.

I'm not inclined to bring the 386 in at this stage, as there's very little space in the AASTO. The existing super reliably boots off its floppy, and we'll have a go at the hard disk in a day or two. We'll bring the 386 in when there's a bit more room.

On a triumphant note, it's clear that there's *no* ice inside the instruments, the blackbody is completely free of ice, everything moves and rotates like it should, and there's only a teensy bit of snow that's got inside the yellow cover of the MISM. One side of the NISM cover split off; Ant has glued it back together and has it sitting in the MAPO shop weighed down with a rotary pump, a lathe chuck, and a few hundred pounds of odds and ends (the side is badly warped - it's not clear it's going to stick back successfully).

Andre; thanks for talking to Nick Roberts about the chemicals. We're bringing back samples - do you think he'd be prepared to look at them and tell us if its fluoride, chloride or sulphate? The possibility of sulphate from the batteries is an interesting one - Ev says the racks look "blacker" than you get from a standard TEG melt-down.

Thanks(?) also for the advice that we use the Stromlo MoS2 spray-on lubricant for the bearings. We fished the tin out and it was *stuffed*. We've placed it under the ANU poster... Ant found some teflon-based spray-on stuff in MAPO; seems to work a treat.

As a final task we installed the new stepper in the MISM. It's always a hard decision whether to work outside in the cold (with all those tiny screws, all different sizes), or go to the trouble of disassembling everything and bringing it indoors. We opted for the former - it took hours. Finally, when rotating the MISM by hand to check the balance there's something "rattling" inside. Quel horeur! If it's a washer, that's ok. If it's a lens, that's not so good. Ant says that since the MISM can see him, that's about as good as it gets. I guess it could be a piece of CVF. I'm happy to run with the existing CVF, at least until January.

Ant put all his clothes on to wash, only to have the water to the Elevated Dorm fail. He now has a whole collection of wet clothes. He's taking it well, but seems reluctant to go out and pull the AFOS off the tower in his pajamas.

Now, to send this I just do ctrl-alt-delete....

 

 

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