Saturday, 5 July 2014

Guest post part 2 - The 'new' Horse Under Water

A horse, indeed, under water
I’ve always been very fond of Deighton’s novel, Horse Under Water. This despite the fact that I could never quite bring myself to believe that a submersible weather buoy from 1945 would still be working when Harry Palmer and Petty Officer Edwards scoop it out of the sea at the end of the novel.

It seems that no modern energy storage system, never mind a 1945 system, could allow such a device to surface every 12 hours. Len doesn’t go into details but I assumed that such a machine would be like a small submarine with a floodable chamber to make it sink and a compressed air cylinder to clear that chamber of water to make it surface again. The air cylinder would then have to be replenished, on the surface, ready for the next dive/surface cycle 12 hours later. So the system would need either a diesel engine or a large electric motor in order to recharge the compressed air tank. Either way the required supply of diesel, and/or battery power stretched my credibility.

However, the image of this tireless machine traveling twice a day from the sea bed up to the surface is really too striking to abandon. So it’s fun to speculate what the Horse in the ‘lost‘ Harry Palmer film would be like. So when was the book set? Having retrieved the thing they have to chisel a couple of bolts off, ‘but that’s only to be expected after more than a decade under water’. So, is there a way to keep a submersible weather buoy going until 1963, when the book was published?

The text also explains that the submerged buoy, or Horse, could be ‘summoned’ to the surface by the use of a special, Very Long-Wave radio system. Very Long-Wave signals are needed to communicate with submerged vessels. In 1962 America was experimenting with VLW radio so that, for example, firing orders could be sent to submerged Ballistic missile carrying submarines.

In the new introduction Len Deighton says that he was helping to catalogue some of the finds in the War Museum when he found the technology that goes into Horse. Well, not knowing exactly what Len found in the archives of the War Museum I’ve tried to work it out for myself. It’s taken me about 45 years but I think I’ve finally figured out how to do it! Some readers might find the technology I’ve found interesting, especially as it touches upon modern weaponry and espionage technology.

First of all it’s necessary to find a different way to make the buoy repeatedly surface and dive. Today there are underwater vehicles that use a mechanical system called ‘displacement adjustment’. These are called Slocum Gliders. These machines look like winged torpedoes and they can travel very long distances without recourse to propellers. A chamber is caused to fill or empty of water through the movement of a piston. Repeated dive/surface cycles are made by moving the piston in its cylinder.

This system requires far less energy than repeated cycles of compressed air.

Such a machine can also convert some of the energy of its ascent and decent into forward motion, just as an airborne glider does. Indeed, some Slocum gliders can exploit the thermal gradients of the ocean to ascend in the same way fashion as airborne gliders. This page describes a Slocum Glider.
An autonomous Slocum Glider made a transatlantic crossing about 5 years ago.

Still more interesting is a military application of underwater gliders. These are designed to autonomously track diesel/electric submarines. Perhaps it also has ‘sniffer’ sensors for diesel fumes. These devices surface periodically to take GPS fixes and call home via satellite radio. Moreover, these machines are extremely stealthy in operation - they have no propellor noise to give the game away.

So now perhaps we can create something close to the long lived weather buoy described in Horse.The one in the book appears to be free floating - once PO Edwardes gets a line around it they haul it straight up into the helicopter. But, in order to make my system work let’s assume that there is a cable anchoring it to the sea bed near Cape Santa Maria. My tethered buoy uses the Slocum glider system of a piston and cylinder. And, being tethered, the energy of the tide can be used to turn a propellor to power a generator. This could provide sufficient electrical power to keep the system working. As a bonus it can power the radio and send a radio signal every time it surfaces - the regular report of local weather conditions that is the primary function of the weather buoy.

That transmitter that Austin Butterworth pulls out of da Cunha’s safe is supposed to send a VLW (Very Long-Wave) signal to the submerged buoy. A VLW transmitter, even made with the early stone age electronics of 1944, is not a huge problem, but VLW transmitters need very long aerials to work properly and these need to be oriented correctly. Such aerials are many thousands of feet long. Moreover, the VLW signals do not reach far below the surface. The subs with VLW receivers generally tow an antenna behind them which is arranged to float just below the surface.

This VLW signal, according to the book, is used to cause the buoy leave the seabed and surface for maintenance. I think I’d just wait until the buoy surfaced, as it does every 12 hours anyway, and then send it a command to stay on the surface using normal HF radio. This command signal can be encoded, to stop any passing radio ham with a morse key from taking control of my weather buoy.

So, my weather buoy looks like this - It’s about the shape and size of an oil drum but made of thicker steel. Although it is anchored to the sea bed the cable is long enough so that it can float with one circular end a out of the water, enough to get the radio aerial clear of the sea. It is divided into three sections by horizontal bulkheads. In the upper compartment, where the instruments go, is the sealed tin with the Weiss list. Below this is a compartment containing lead acid batteries, the radio transmitter and receiver and the control system(which is just a mechanical timer and some relays). There’s an electric motor and gearbox which pushes a threaded rod, connected to the piston, which is in the third and lowest compartment. This compartment is open to the sea at the bottom and the piston sweeps its entire volume. When it must dive the piston retracts compressing the air behind it and letting the water flow in. When the buoy must surface the piston pushes all the water out of the lower compartment. A shrouded propeller is turned as the tide flows in and out past the tethered buoy. The propellor turns a generator that keeps the batteries charged and keeps the whole system working until something breaks.

So there we have it, at last I’ve convinced myself that those cunning Deutsch engineers could have created a submersible weather buoy that would still be going ‘more than a decade’ later. (Given superb German engineering). Now I’ll have to re-read Horse Under Water to see how well my version of the Horse fits in with the action. But that’s no hardship and I’ve been looking for an excuse anyway!


  1. I enjoyed your technical analysis of a meteorological buoy very interesting. It hadn't occurred to me that it was on the technological forefront, I had always thought that the "horse" was the heroin. I also am happy for Mr. Deighton to take liberties with reality. My favorite is in Ipcress File when he opens a door with a pencil. Footnoted "This method of opening a lock with a pencil has been withdrawn from the MS."!!


    Richard Corles

  2. Hi Richard,

    The question I didn't try to answer is why it is necessary to go to all the trouble of making a weather buoy able to submerge?

    There might actually have been some advantage to leaving it on the surface. Such a thing would be big enough to appear on the anti-shipping radar that the RAF were deploying at the time. It would probably have created a radar return about as big as the snorkle of a submerged sub. And if the RAF wasted depth charges on it, and even destroyed it, rather than on an actual German U-boat, that might be considered a net gain. But not, presumably, to the man in charge of gathering weather information!

    I'm glad you my 'horse'. I enjoyed dreaming it up.

  3. I have long loved the Len Deighton novels.

    The only niggles I recall are:

    - Can you really kill a man with a skyrocket and a bottle of "rum"? - FIB

    - Why would the US military invite a bunch of British spies to observe a nuclear test in the South Pacific including a suspected double-agent? - TIF

    - Why hide invaluable incriminating material in a dodgy WW2 underwater buoy, rather than in a vault? - HUW