JOHT 14: Secret Weapons

[stickmaker]

The Joy of High Tech

by

Rodford Edmiston

    Being the occasionally interesting ramblings of a major-league technophile.

Please note that while I am an engineer (BSCE) and do my research, I am not a professional in this field. Do not take anything here as gospel; check the facts I give. And if you find a mistake, please let me know about it.

Secret Weapons

    I'm sure many of you have read John W. Campbell's contention that the Romans had a secret weapon which was responsible for many of their military victories. It was something in plain sight, but outside the mindset of most of their enemies, so they literally didn't recognize its importance. Because to those enemies it was individual valor in fighting that was important. They believed that any one of them was worth at least two Legionnaires. They were likely right. Those short Roman swords just weren't as effective in single combat as the longer, heavier swords of - say - the Germanic tribes. However, as mentioned above, the Romans had a secret weapon. Something clearly visible to anyone able to look past the concept of fighting for personal glory. That weapon was group tactics. The Roman Legion's short swords, large shields and spears were ideal for the sort of closed-rank, up close, mutually supportive fighting practiced by the Legionnaires. 

    A secret weapon is anything which gives an advantage over an enemy, and which the enemy does not know about. (Though they may know of it.) It can be an actual, physical weapon. It can be a way of fighting, as described above. It can be something which indirectly supports military activity, such as a free market economy, in which competition weeds out inefficient manufacturers. It can be information. For a secret weapon to work, there must exist conditions which will allow it to be developed and employed without the enemy learning about it; or, if they know about it, they have a reason to discount it. The best secret weapons in history were the result of an innovative atmosphere which permitted them to come about, a willingness on the part of those in charge to try them, and the ability to keep the enemy from learning about them until too late. Closed minds and secret weapons rarely work well together. A prime example is the use of radar in the Second World War. (Much of the technology discussed here is from that era. That is long enough ago that most of the secret information has been declassified. Also, this was a period of frantic military invention unrivaled in history.)

    In the late Thirties the Germans had probably the best radars in the world, both fixed and portable units operating in the 50 centimeter band. This was a very short wavelength for the technology of the day. In 1939 the Germans noticed what appeared to be radio broadcast stations being erected along the British east coast, overlooking the Channel. The natural suspicion was that they were radar installations. However, these sites used tall towers set well apart, with wires strung between them, all wrong for shortwave radar. Those antenna - if they were antenna - couldn't even be aimed! The Germans wanted to know what these were. One method they used to check was to equip two military Zeppelins with radio receivers and fly them near the sites. They detected nothing beyond natural static and some remote radio noise. Yet the British technicians clearly saw the huge blips on their radar screens. Why did the Germans fail to even detect the powerful signals being put out by the British units? 

    The British radar sets were operating on extremely long wavelengths, in the 10 meter band. Something the Germans should have suspected because of the size of the antennas. However, because they assumed that British radar development had followed a course similar to their own, they didn't even have equipment on board the Zeppelins to detect emissions in those frequency ranges. (Note that this choice of frequency was not due to technical backwardness, but was deliberately selected for the role these stations were intended to play. The equipment was designed to cover as much of the coastline as possible with as few installations as possible, necessitating long wavelengths. The British later added to their coastal warning system radar sets operating in the 1.5 meter band for detecting low-flying aircraft.)

    Later in the War, the Germans made a similar mistake in the opposite direction, but this time the mistake was much more understandable.

    Physics tells us that - as a general rule - the shorter the wavelength used, the better the discrimination of the radar system. For practical reasons radiation in the microwave frequencies is generally the best choice. However, microwaves are difficult to produce with vacuum tubes. There had been some development in the Thirties, even demonstrations in which microwaves were used to cook food. However, when radar was being developed the researchers concentrated on longer radio waves, because everybody knew that it was too hard to produce a powerful enough beam in microwave frequencies. Tubes just weren't up to the job. (This is a matter of physics, not technology. Vacuum tube amplifiers are a significant portion of a microwave wavelength long, which leads to problems inside the tube.)

    In the winter of 1939-1940 British scientists Dr. (later Sir) John Randal and Dr. Harry Boot developed the cavity magnetron, which was a major improvement over the previously existing split-anode magnetron at producing microwave transmissions. This new device opened a whole new vista for Allied radar developers. Radar sets could be made smaller, more powerful, more accurate, more discerning, more reliable and given greater range. The first of these sets (including the famed H2S airborne radar) operated in the 10 cm range. Later WWII units went down to 3 cm. 

    Microwave radar sets were used both on the ground and in the air, the latter for bombing at night and through clouds; as well as in specialized fighters for shooting down enemy bombers in the dark. (Previous airborne radars used by both sides operated at longer wavelengths, which allowed them to spot aircraft but not resolve ground targets.) The sets worked wonderfully well, but the Allied commanders were worried. They knew the Germans still hadn't hit on the idea of the cavity magnetron. What if one of the bombers carrying a microwave set over Europe were shot down and the magnetron found?

    Various efforts at misdirection were used to maintain the secret. For instance, to explain the increasing accuracy of night bombing and the improved success the night fighters were having, a famous bit of flummery was instituted. One which continues - though unintentionally - to this day. Newsreels and newspapers carried stories about how bombardiers and pilots were being fed extra carrots to improve their night vision. In truth, while extra Vitamin A can help someone with night-blindness caused by a deficiency, someone who already has normal night vision will not experience any improvement. Just try telling that to millions of mothers, though!

    Still, the Allied commanders continued to worry. The Germans had some clever people, and all it would take was one good hint for them to figure out what was happening. Something as strange as a cavity magnetron, hooked up to what was obviously a radar set was a very good hint. Worse, the magnetron was essentially a milled block of copper, and very hard to damage enough to disguise its characteristics. It would probably survive a crash, and even a destruct charge. The new radar sets were too beneficial to not apply to the task, though, so their use continued.

    Eventually one of the planes carrying a microwave radar bomb aiming set was shot down. Inevitably, the mysterious electronic gadget with the even more mysterious device inside was turned over to German electronics experts. Their verdict was, "We don't know what this thing is, but we know for certain it has nothing to do with radar." Because they knew that microwaves could not be used for radar. They could tell from the construction of the rest of the device that it operated - or was meant to give the impression that is operated - at microwave frequencies. Therefore, this was not a radar set. It must be a clever bit of misdirection on the part of the Allies. 

    This was not a one-time mistake in regard to microwave radar on the part of German researchers. Another example comes from the work that some were doing on infrared night vision devices. When Allied warships and naval patrol bombers began sinking U-boats with disturbing regularity at night, while the submarines were on the surface recharging their batteries, the first idea from the Germans was that radar sets in the ships and planes were responsible. However, the long-wave and shortwave radar detectors (which had served to give warning previously, against older Allied radars) in the submarines didn't react. Therefore it was decided that the Allies must be using IR equipment to spot the warm conning tower against the cool sea. Many man-hours were wasted in creating, manufacturing and installing heat baffles on the conning towers. The submarines kept getting sunk, because the baffle material was transparent to radio waves. The baffles also meant the submarines had to move more slowly, or the supposed protection would be washed away.

    So the Schnorkle was adopted. This allowed the submarines to stay submerged while taking in air and exhausting fumes through the double pipe. They *still* got sunk by bombers. It wasn't IR. It wasn't radar (that they could detect, that is). What was it? 

    Of course, because the German radar experts knew that microwave radar was impossible, they didn't notice that the Schnorkle was a good length to resonate at microwave frequencies.

    The situation didn't last, of course. Eventually the Germans did capture a nearly complete H2S radar and decipher it, and put their own microwave radar into production. A radar-absorbent covering was developed for the Schnorkle, but it wasn't really practical. (It worked, but also washed away too easily.) The Germans also supplemented the Metox radar warning sets in the submarines with the Naxos unit, which could detect the 10 cm band radar. For the next two years the advantage see-sawed back and forth, but the German submarines never again were as effective against convoys as they had been during the early part of the Battle of the Atlantic. In part due to better tactics to protect the convoys.

    The Ultra secret is another example of how arrogant minds make arrogant mistakes. The German High Command was so impressed (and infatuated) with the Enigma code machine that they ignored the device's weaknesses. For instance, no letter could stand for itself. Also, all numbers had to be spelled out, since the machines had no number keys. These and other features gave Allied code breakers toeholds for working on the messages the Enigma machines encrypted. Eventually, after a couple of lucky breaks and a great deal of help from Polish and other operatives in occupied countries, the code breakers succeeded. (Several books could be - and have been - written on the development of fast, programmable computers made just to defeat Enigma and similar coding machines.) The German secret weapon had been defeated. (Despite what J. Michael Strazinski thinks, the story of Churchill letting Coventry be bombed to protect the secret of Ultra is a myth. However, it is true that officers using information provided by Ultra were under orders never to take action based on intelligence gained through it that could not have been obtained from other sources.)

    Note that there were several versions of the Enigma machine operated by the Nazis. They were in use for over two decades, constantly upgraded and with different models for different purposes. Also, the Army and Luftwaffe used one model and the Navy another. Neither type of Enigma could decode the messages of the other. This made things more complicated for the Allied code breakers, since they had to develop a method to break the coding of each machine separately. However, break these codes they did. They also broke the Japanese code. In fact, the only code in common use during WWII on any side which was not broken was that used by the Navajo Code Talkers.

    The Nazi leaders were so impressed with the numerical complexities of the Enigma machines, and by the constant upgrades made to them throughout the War, that they made it policy the Enigma code was unbreakable. When field commanders reported their suspicions that coded messages were being intercepted and decoded, they were told this was impossible. The intelligence leaks must be due to security problems on site. (Note that the possibility of a particular message eventually being decoded was accepted, but the assumption was that the effort required was so great that by the time an enemy had done so, the information in the message would be outdated. Remember the fast, programmable computers mentioned above? There were instances of the Allies getting translations of Enigma messages before the intended recipient.)

    Of course, the Germans weren't the only ones occasionally hampered by hubris. Recall their efforts with IR viewing systems. These resulted in the first night vision scopes, using IR lamps and a somewhat cumbersome electronic viewing device. This development came as rather an unpleasant surprise to the Allies. Their experts had told them this process was impossible, since it involved converting low energy, invisible photons to high energy, visible photons. Once in possession of the German devices, the Allies did develop their own such equipment, late in the war. This was primarily used for rifle sniperscopes.

    A more spectacular failure in Allied technical judgement occurred in regard to the V-2 rocket. Today it is almost amusing to read descriptions of the British experts discussing the mysterious series of explosions caused by the first V-2 rockets to land in Britain. There were so many reasons given so emphatically as to why none of the suggested methods (including large rockets) could possibly work that one almost expects to read that the committee concluded the explosions never actually happened! That the supersonic impact so thoroughly destroyed the V-2 that only scrap was left didn't help. All that unidentifiable debris could have been from something at the target site! Even arial reconnaissance photos showing a V-2 on a transport trailer were dismissed as being of a large torpedo.

Part of the problem was that the British experts being consulted were only familiar with solid-propellant rockets. They were quite correct that a rocket burning, say, cordite could not carry a significant payload. Certainly not for anything like the distance across the Channel!

    Sometimes a weapon can have effects that are secret even from the people using it. The Parachute and Cable (or PAC) was a British weapon intended to bring down German bombers. The idea was that a cable would be lifted into the air by a rocket into the path of the bomber. The bottom end of the cable carried an explosive device, and there was a parachute at the top, which was deployed when the rocket burned out. The parachute served two functions. The canopy slowed the cable's fall, and if the cable caught a bomber's wing the drag from the parachute would pull the cable across the wing until the explosive charge on the other end made contact and detonated. (Early versions simply had a second parachute at the bottom, with no explosive. They were intended to entangle propellers. Later variations included hanging the cables from barrage balloons.) Proponents of PAC expected Nazi bombers to drop from the skies in droves.

    At first the weapon seemed to have - at best - limited effectiveness. Some enemy aircraft were downed, but far more simply flew away after clear hits. PAC began to fall out of favor. Then interesting reports began coming in, from interrogations of captured German pilots, and conversations overheard by underground operatives. These accounts related horror stories of engines going dead, later to be found mysteriously tangled in what looked like huge lengths of piano wire. Worse, the cable had a parachute on one end, creating high drag on the side with the dead engine. As a final terror, on landing a dangling explosive charge could blow up the plane, damage the runway or both! Even if the cable didn't catch on something, but dragged across the wing, it sawed through the metal! (Several aircraft are documented as having a wing pulled off simply by the shock of impact with the cable, including a Wellington bomber used in early trials.)  

    Other accounts soon supported the effectiveness of the device. A few aircraft were unfortunate enough to pick up several PAC at once. These were rapidly dragged to a stall and literally fell out of the air! Imagine the effect seeing this had on the crews of other German bombers in the same formation. 

    So while the PAC wasn't nearly as effective at directly downing bombers as hoped, it definitely had an adverse effect on German aircrew morale. However, the PAC was not really a success at defending Britain. For one thing, it wasn't as accurate as traditional antiaircraft fire, which was steadily improving. Its effectiveness also received a big boost with the adoption of proximity fuses.

The PAC device never really worked like it should have, and even when it did there were unique problems associated with it. There were safety concerns, for example. The explosive charges were supposed to self-destruct before reaching the ground. Unfortunately, they didn't always, thus creating a hazard for unsuspecting civilians. There was also the problem of dropping steel cables across electrical transmission wires. All that steel could also be put to better use in other applications. 

    Sea-borne versions were less problematical in many of these respects, and so the PAC was much more often used aboard ships than on land. The ocean going PAC - placed mostly aboard small ships, such as merchant marine vessels, which didn't have the room or the crew for the heavy antiaircraft defenses of large military watercraft - is credited with downing 9 enemy aircraft.

    Though it started out as a secret weapon, the Parachute and Cable was too spectacular in its operation to remain one, and was actually taken off the Secret List in 1943. 

    Which brings us back to the problem of how to keep something secret when you need to use it. The developments of such devices as the V-2 ballistic rocket and the Me262 jet fighter were kept secret (though some clues inevitably leaked out, the Allies didn't really know many particulars and didn't always believe the ones they knew). Once the weapons were put to use they quickly became known. Still, the details involved in their construction and operation remained secret and much effort was expended by the other side attempting to learn them. Some of this work took the form of espionage, and some of scavenging. At one point, the Underground got to the crash site of a test V-2 before the Germans did and hid large portions of the wreckage. These parts were later shipped to England, where they provided important clues as to the capabilities of the V-2. 

    Even so, the Allies never developed anything like it. The airbreathing, unmanned drone plane known as the V-1 was duplicated (the American version was known as the Loon) but never saw much actual use. The V-2, though, was unique to the Germans. All of those used by the Allies after the war were captured, not copied. By the time Allied rocket technology was ready to consider building military ballistic missiles, the science of rocketry had advanced beyond the V-2. The same was true with the Me262 Swallow jet fighter. The first Allied jet fighters were much less advanced than the German jet; some were not even as fast as the best propellor fighters then available. The second generation was much more advanced, in large part due to what was learned from the Germans. So one way to keep the use of a secret weapon for yourself after it is no longer a secret is to use the period of secrecy to advance far enough ahead of your enemies to keep them from copying your weapon before the war is over. Of course, if you don't win...

    Another class of secret weapon is entirely the stuff of spy and espionage tales. The amount of equipment - and the wide variety of types of it - which has been placed in uniform buttons and boot heels, sewn into jacket linings and glued into book covers and game boards is astounding. However, this stuff is less secret than simply hidden. Everyone not only does the same things but expect it of the other side. So that class of object doesn't really come under the scope of this article. 

    The most famous secret weapon of all time is - of course - the fission bomb. Except that it was never really a secret. Nature is an impartial witness; ask the right question and you'll get a useful answer, no matter what your politics. It has been famously said that the only secret about the atom bomb is that it is possible.

    Otto Hahn was the first person to publish speculation on the possibility of a uranium nuclear chain reaction in a scientific journal. He was also involved in German nuclear research during the war. Several other renowned nuclear physicists - including Werner Heisenberg - were involved in German nuclear research. At that time the Germans had the best research and industrial chemists in the world. Small wonder Einstein and other Allied scientists were concerned about the possibility of the Nazis developing a nuclear bomb. Why didn't they? There is considerable evidence that Heisenberg quietly diverted German research in the wrong direction. Also, there was a war on, and the High Command could see that developing a nuclear weapon would take too long and require too many resources to be ready for use in the short war they expected. Therefore, German nuclear research focused on other potential uses. Such as creating large amounts of short-lived radioisotopes to use to poison enemy lands and facilities. (Alas for that plan, it took too long to get to the point of developing these in large amounts. By that time the Germans were unable to distribute them by bomber, and the V-2 was never reliable enough. It was too likely to blow up over conquered or friendly territory.)

    As for the Russians, some of their scientists were speculating on uranium chain reactions by 1939, following announcement of German experiments with neutron bombardment of uranium (performed by Hahn and Fritz Straussmann). They recognized the same problems which deterred the Germans, but the Soviets were expecting a long war. Moreover, they thought the Germans would also be planning for a long war, and therefore researching fission weapons. The official Soviet bomb research program was started in the middle of 1941, shortly after the German invasion. 

    Due to the dislocations this attack caused, most of the early Russian research was purely theoretical. (Ironically, the primary benefit of Soviet espionage into Allied bomb research was to verify ideas which the Soviets could not check out themselves, due to the lack of facilities. The possibility of a bomb was long known, and some Russian physicists deduced the existence of the Allied bomb program from the simple fact that physics journals were no longer carrying articles on nuclear fission!)

    There are a great many more secret weapons, from WWII and before and after. Most never went beyond the design stage. Most of those which reached trials never became operational. (It would have been interesting to see the faces of German soldiers defending the beaches of Normandy as a Great Panjandrum came roaring and flaming up the sand.) Many of those which did actually see service were soon dropped or replaced by something more conventional. Some were so successful that they still officially do not exist, remaining secret 10, 20, even sixty years later.