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 afifteen-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-widemoving 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 youcan 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
‘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-widemoving 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 youcan 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
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