Ice Station Zebra. Alistair MacLean

to remain maximum fourteen.”’ He turned to me and said: ‘If we can’t find them in that time …’ and left the sentence unfinished.

      I nodded, and he went on: ‘“Many thanks for your splendid co-operation. Good luck and a safe trip home.”’ As the signalman’s lamp started chattering out its message, he said wonderingly: ‘Do those fishermen trawl up in the Arctic the entire winter?’

      ‘They do.’

      ‘The whole winter. Fifteen minutes and I’m about dead. Just a bunch of decadent Limeys, that’s what they are.’ A lamp aboard the Morning Star flickered for some seconds and Swanson said: ‘What reply?’

      ‘“Mind your heads under that ice. Good luck and goodbye.”’

      ‘Everybody below,’ Swanson said. As the signalman began to strip the canvas dodger I dropped down a ladder into a small compartment beneath, wriggled through a hatch and down a second ladder to the pressure hull of the submarine, another hatch, a third ladder and then I was on the control deck of the Dolphin. Swanson and the signalman followed, then last of all Hansen, who had to close the two heavy watertight doors above.

      Commander Swanson’s diving technique would have proved a vast disappointment to those brought up on a diet of movie submarines. No frenzied activity, no tense steely-eyed men hovering over controls, no Tannoy calls of ‘Dive, dive, dive,’ no blaring of klaxons. Swanson reached down a steel-spring microphone, said quietly: ‘This is the captain. We are about to move under the ice. Diving now,’ hung up and said: ‘Three hundred feet.’

      The chief electronics technician leisurely checked the rows of lights indicating all hatches, surface openings and valves closed to the sea. The disc lights were out: the slot lights burned brightly. Just as leisurely he re-checked them, glanced at Swanson and said: ‘Straight line shut, sir.’ Swanson nodded. Air hissed loudly out of the ballast tanks, and that was it. We were on our way. It was about as wildly exciting as watching a man push a wheelbarrow. And there was something oddly reassuring about it all.

      Ten minutes later Swanson came up to me. In the past two days I’d come to know Commander Swanson fairly well, like him a lot and respect him tremendously. The crew had complete and implicit faith in him. I was beginning to have the same thing. He was a kindly genial man with a vast knowledge of every aspect of submarining, a remarkable eye for detail, an even more remarkably acute mind and an imperturbability that remained absolute under all conditions. Hansen, his executive officer and clearly no respecter of persons, had said flatly that Swanson was the best submarine officer in the Navy. I hoped he was right, that was the kind of man I wanted around in conditions like those.

      ‘We’re about to move under the ice now, Dr Carpenter,’ he said. ‘How do you feel about it?’

      ‘I’d feel better if I could see where we were going.’

      ‘We can see,’ he said. ‘We’ve the best eyes in the world aboard the Dolphin. We’ve got eyes that look down, around, ahead and straight up. Our downward eye is the fathometer or echo-sounder that tells us just how deep the water below our keel is – and as we have about five thousand feet of water below our keel at this particular spot we’re hardly likely to bump into underwater projections and its use right now is purely a formality. But no responsible navigation officer would ever think of switching it off. We have two sonar eyes for looking around and ahead, one sweeping the ship, another searching out a fifteen-degree path on either side of the bow. Sees everything, hears everything. You drop a spanner on a warship twenty miles away and we know all about it. Fact. Again it seems purely a formality. The sonar is searching for underwater ice stalactites forced down by the pressure of rafted ice above, but in five trips under the ice and two to the Pole I’ve never seen underwater stalactites or ridges deeper than 200 feet, and we’re at 300 feet now. But we still keep them on.’

      ‘You might bump into a whale?’ I suggested.

      ‘We might bump into another submarine.’ He wasn’t smiling. ‘And that would be the end of both of us. What with the Russian and our own nuclear submarines busy criss-crossing to and fro across the top of the world the underside of the polar ice-cap is getting more like Times Square every day.’

      ‘But surely the chances –’

      ‘What are the chances of mid-air collision to the only two aircraft occupying ten thousand square miles of sky? On paper, they don’t exist. There have been three such collisions this year already. So we keep the sonar pinging. But the really important eye, when you’re under the ice, is the one that looks up. Come and have a squint at it.’

      He led the way to the after starboard end of the control room where Dr Benson and another man were busy studying a glassed-in eye-level machine which outwardly consisted of a seven-inch-wide moving ribbon of paper and an inked stylus that was tracing a narrow straight black line along it. Benson was engrossed in adjusting some of the calibrated controls.

      ‘The surface fathometer,’ Swanson said. ‘Better known as the ice-machine. It’s not really Dr Benson’s machine at all, we have two trained operators aboard, but as we see no way of separating him from it without actually court-martialling him, we take the easy way out and let him be.’ Benson grinned, but his eye didn’t leave the line traced by the stylus. ‘Same principle as the echo-sounding machine, it just bounces an echo back from the ice – when there is any. That thin black line you see means open water above. When we move under the ice the stylus has an added vertical motion which not only indicates the presence of ice but also gives us its thickness.’

      ‘Ingenious,’ I said.

      ‘It’s more than that. Under the ice it can be life or death for the Dolphin. It certainly means life or death for Drift Station Zebra. If we ever get its position we can’t get at it until we break through the ice and this is the only machine that can tell us where the ice is thinnest.’

      ‘No open water at this time of year? No leads?’

      ‘Polynyas, we call them. None. Mind you, the ice-pack is never static, not even in winter, and surface pressure changes can very occasionally tear the ice apart and expose open water. With air temperatures such as you get in winter you can guess how long the open water stays in a liquid condition. There’s a skin of ice on it in five minutes, an inch in an hour and a foot inside two days. If we get to one of those frozen over polynyas inside, say, three days, we’ve a fair chance of breaking through.’

      ‘With the conning-tower?’

      ‘That’s it. The sail. All new nuclear subs have specially strengthened sails designed for one purpose only – breaking through Arctic ice. Even so we have to go pretty gently as the shock, of course, is transmitted to the pressure hull.’

      I thought about this a bit then said: ‘What happens to the pressure hull if you come up too fast – as I understand may happen with a sudden change in salinity and sea temperature – and you find out at the last minute that you’ve drifted away from the indicated area of thin ice and have ten solid feet of the stuff above you?’

      ‘That’s it,’ he said. ‘Like you say, it’s the last minute. Don’t even think about such things, far less talk about them: I can’t afford to have nightmares on this job.’ I looked at him closely, but he wasn’t smiling any more. He lowered his voice. ‘I don’t honestly think that there is one member of the crew of the Dolphin who doesn’t get a little bit scared when we move in under the ice. I know I do. I think this is the finest ship in the world, Dr Carpenter, but there are still a hundred things that can go wrong with it and if anything happens to the reactor or the steam turbines or the electrical generators – then we’re already in our coffin and the lid screwed down. The ice-pack above is the coffin lid. In the open sea most of those things don’t matter a damn – we just surface or go to snorkel depth and proceed on our diesels. But for diesels you need air – and there’s no air under the ice-pack. So if anything happens we either find a polynya to surface in, one chance in ten thousand at this time of year, before our standby battery packs up or – well, that’s it.’

      ‘This is all very encouraging,’