Fixing the Sky (25 page)

A story in
Time
in 1934 described a test of Houghton's chemical “fog broom,” conducted at the private airfield of eccentric millionaire Colonel Edward Howland Robinson Green on his Round Hill estate overlooking Buzzards Bay. Houghton had erected a large scaffold across the runway to support a maze of piping and nozzles, “patterned after the business end of a skunk,” that he claimed offered “the first practically-tested way of artificially dissipating fog over local areas” (figure 4.5). As a bank of thick fog rolled in from the ocean, Houghton powered up his “secret” apparatus. As the
Time
reporter described it, “Centrifugal pumps sent a
high-pressure stream of liquid through the overhead pipe. Its nozzles hissed, and jets of Mr. Houghton's chemical cut into the fog like rapiers. The white sea seemed to divide, roll back like the Red Sea before Moses. Soon the watchers were looking through a half-mile tunnel of clear air, 30 feet high, 100 feet wide.”
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4.5 Henry G. Houghton standing on the chemical fog dissipation apparatus at the MIT research station near South Dartmouth, Massachusetts. Colonel Edward Howland Robinson Green's mansion and the mast of a whaling ship can be seen in the background. (NATIONAL ARCHIVES PHOTO 27-G-1A-8–48)

Houghton's research supported the goals of military chemists who were seeking effective smoke screen agents and possible chemical neutralizing agents for use during poison gas attacks. He learned that titanium or zinc chloride could be used in generating smoke screens, but calcium chloride (CaCl
₂
) acted as a hygroscopic drying agent, or desiccant. Calcium chloride is a non-toxic exothermic compound that lowers the freezing point of water. It is used as a water softener, to suppress dust on dirt roads, to melt ice, and as a drying agent in concrete. It can be used as a food preservative, but can also be a powerful abrasive irritant on moist skin tissue and in the eyes, nose, mouth, throat, and lungs. When burned, it produces toxic and corrosive fumes. It attacks zinc in the presence of water to form highly flammable hydrogen gas, and it corrodes steel rebar. Experiments conducted in a laboratory cloud chamber indicated that 1 gram of calcium chloride could clear 3 cubic meters of foggy air, possibly by lowering the vapor pressure of water. Houghton hoped his chemical sprays might be used to clear fog at airports and to add a margin of safety for ocean liners using it to sweep their paths clear. He had basically designed a huge chemical dehumidifier.
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Working against the practical adoption of this technique was the enormous amount of chemical needed to keep open even a moderate-sized hole in the fog. Since the ocean fog kept rolling in and re-forming, a constant chemical spray of about 400 pounds a second (!) would have been needed to maintain a half mile opening during the Round Hill experiment. Moreover, as the researchers admitted, “Apparatus of the type described cannot readily be made portable and its size makes it a rather serious obstruction for some applications, notably at airports.” As mentioned, the electrified, high-pressure calcium chloride spray was corrosive to metals. It tended to clog the spray nozzles and had to be washed off any metal objects it contacted, especially electrical systems, but also the piping and even the airplanes and ships it was designed to serve. It was also dangerous to personnel, producing skin rashes if not rinsed off, and it killed vegetation (it was sold as a weed killer). The navy had some unfortunate experiences with the chemical and ultimately decided not to use it on its airplane carriers.
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Reminiscent of the later distinction between cloud physics and weather modification—perhaps also between basic research and practical applications—MIT researchers were quick to point out that fog research, not fog control, was their ultimate aim: “The end result, whatever the practical application of local fog
dissipation, has been a substantial increase in knowledge of the physical properties of fog and of the means for conveniently determining these properties, as well as a more thorough quantitative knowledge of the transmission of electromagnetic waves through fog, whether they be radio, light, or long infrared.”
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Still, the list of institutions acknowledged for their support in the MIT report reads like a who's who of the military–industrial complex in 1934: Colonel Green for the use of his estate; the American Philosophical Society for a research grant; and the U.S. Navy Bureau of Aeronautics, the U.S. Army Air Corps, and the Bureau of Air Commerce of the Department of Commerce for their support. Huge amounts of chemicals were provided free of charge by the Michigan and Columbia alkali companies and the Dow Chemical Company. Edison Electric of Boston lent the experimenters a large power transformer. This combination of government, commercial, and private philanthropic support was part of a persistent pattern of patronage (6–7).

It is undoubtedly true that a 30-foot-high barrier made of metal pipes and stretched across a runway is dangerous to airplanes landing and taking off, especially in conditions of low visibility. Houghton's chemical mix, although promising, was also impractical, being dangerous and corrosive. More substantial was his basic research on the formation and evaporation of small droplets, on the optical properties of fog, and on the search for possible hygroscopic chemicals to disperse it. Houghton's greatest contribution, however, involved the idea that cloud physics research, as distinct from but related to operational weather modification, had a place in the modern university.

Foggy weather kept aviators grounded in World War I, but by 1921 British meteorologist Sir Napier Shaw discussed the possibility of clearing fog at an airfield by heating it, concluding, “I would not like to say it is impossible with unlimited funds and coal.” He noted, however, that “air in the open is very slippery stuff and it has all sorts of ways of evading control that are very disappointing.”
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Professor Frederick A. Lindemann (later Lord Cherwell) agreed with Shaw and chose to emphasize blind landing techniques. Other possibilities, although none of them were proved, included sprays of electrified water, air, or sand (Warren), chemical treatments (Houghton), vigorous fanning, and coating rivers with oil. Yet the brute-force technology of heating the runway was the only one certain to work—although it appeared at the time to be prohibitively expensive.

In 1926 Humphreys estimated that it would require the combustion of 6,600 gallons of oil (or 35 tons of coal) an hour to clear a layer of fog about 150 feet thick from a typical airfield—a cost that he deemed far too large. David Brunt, Shaw's successor at the Imperial College of Science and Technology, revisited the issue in 1939. He estimated that clearing a layer of fog about 300 feet thick would require an average temperature increase of 3.5°C (6°F) (twice this at the ground) and suggested that smokeless burners supplied by an oil pipeline along an airfield could be designed to do the job. Brunt's ideas were field-tested in the winter of 1938/1939, but the results were not promising.
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As World War II escalated, fog became an obstacle to successful bombing raids. With more raids scheduled, a surging accident rate, and the large number of flying hours lost to fog, the problem became one of “extreme urgency.” In 1942 Prime Minister Winston Churchill directed his scientific adviser, Lord Cherwell, to address the matter and issued the following statement: “It is of great importance to find means to disperse fog at aerodromes so that aircraft can land safely. Let full experiments to this end be put in hand by the Petroleum Warfare Department with all expedition. They should be given every support.”
⁴⁰

Under the leadership of Britain's minister of fuel and power, Sir Geoffrey Lloyd, and Major-General Sir Donald Banks, the scientific research establishment and industry joined forces to tackle the problem. The Petroleum Warfare Department (PWD), an agency created in 1940 to consider “the possibilities inherent in the use of burning oil as an offensive and defensive weapon in warfare,” was charged with developing a reliable, if expensive, brute-force method of clearing fogs over airfields, a system it called Fog Investigation and Dispersal Operation. FIDO was one of the most spectacular but least publicized secret weapons of the war. According to Banks, “We had been making vast preparations to cook the Germans. We would see whether we could cook the atmosphere!”
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It was a massive undertaking. The FIDO project brought together pilots, engineers, fuel scientists, industrialists, government bureaucrats, and meteorologists. Given the urgency of the situation, normal research and development plans were shelved in favor of an all-out attack by research teams from the National Physical Laboratory, Imperial College of Science and Technology, Royal Aircraft Establishment, Armament Research Department, and such industries as the Anglo-Iranian Oil Company, Gas Light and Coke Company, General Electric, Imperial Chemical Industries, London Midland and Scottish Railway, and the Metropolitan Water Board. According to Lloyd, the project director, “each was told to get on with the job with the fullest support and freedom of action.”
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FIDO consisted of a system of tanks, pipes, and burners surrounding British airfields and designed to deliver petroleum that, when ignited, raised the ambient temperature by several degrees—enough to disperse fog and light the way for aircraft operations. The first large-scale test of a FIDO system was conducted in a field and did not involve aircraft takeoffs or landings. With strong radiation fog predicted for the morning of November 4, 1942, the FIDO team assembled at Moody Down, Hampshire. An 80-foot fire escape ladder was positioned between two FIDO burners 200 yards in length and 100 yards apart. As a local fireman climbed to the top of the ladder, he disappeared into the fog. When the burners were lit, the fog began to clear and the fireman came into view. To verify the result, the burners were turned down and the fog reappeared. The burners were again ignited, and the fog dissipated. With typical British reserve, it was reported that Lloyd “
almost
whooped for joy” (emphasis added).
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On the same day, experiments were also conducted at the airfield in Staines, Surrey, using coke-burning braziers shuttled by miniature rail cars along tracks paralleling the runways. While an even denser fog was cleared with less smoke, the coke took longer to light and required more effort to replenish. Gasoline was much easier to pipe to airfields and ultimately became the fuel of choice for FIDO. The urgency of the situation did not allow much time for further experimentation and research. As a result, the petroleum burner setup at Graveley airfield, Hertfordshire, served as the prototype for other FIDO systems ultimately installed at fourteen Royal Air Force (RAF) fields.

On February 5, 1943, Air Vice Marshal Donald C. Bennett landed a Gypsy Major at Graveley in a midday FIDO light-up. Thirteen days later, in the first night test, he again landed, in a Lancaster. Although it was not foggy, visibility was poor. Bennett recounted seeing the blazing runway when he was still 60 miles out. As he made his approach, he recalled, “I had vague thoughts of seeing lions jumping through a hoop of flames at the circus. The glare was certainly considerable and there was some turbulence, but it was nothing to worry about.”
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Except wildfires. A demonstration test for aircrews on February 23 resulted in grass, hedges, trees, and telegraph poles near the burners going up in flame. All hands, in addition to local bomb spotters and fire companies, were called in to fight the blaze. The first opportunity to land an aircraft in actually foggy conditions occurred in July 1943. A thick fog, approximately 300 to 400 feet deep, blanketed the runway, with visibility less than 200 yards. The FIDO burners were lit at five o'clock in the morning, and within seven minutes, an area 1,500 yards long and 200 yards wide was cleared of fog. Aircraft were then able to land successfully at fifteen-minute intervals.
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The futurist Arthur C. Clarke once witnessed a FIDO test in Cornwall: