SciTech Tuesday: Operation Outward

Last autumn my neighbors were having a birthday party in their front yard. The highlight of the decorations was a bundle of helium-filled mylar balloons. It was windy, and they worked themselves free. I was working in my yard, and looked over when I heard sounds of dismay, and I watched the balloons slowly drift towards the power pole across the street. The balloons contacted the transformer, there was a very loud bang, and all the lights on our block went out.

In England during WWII they had barrage balloons along the coast and over cities and military installations. They were large, tethered blimps, designed to make enemy aerial navigation difficult by placing obstacles in the way. Their long cables threatened to entangle encroaching aircraft.  The barrage balloons occasionally broke loose, like the mylar balloons I witnessed. But the defensive blimps, being anchored by heavy metal cables, caused much worse damage to electrical infrastructure.

In September of 1940 a large storm knocked loose a number of barrage balloons, which glided across the North Sea and caused considerable damage to power lines and radio antennas in Denmark and Sweden. After that, Churchill ordered that the possibility of using ballons like these as weapons be investigated. The Royal Air Force responded with a negative report, believing it to be too costly at a low likelihood of effect. The Navy responded enthusiastically.

Winds at high altitudes (>15,000 feet) tend to move from East to West over the North Sea and Europe, so the conditions were favorable, and the Royal Navy had a surplus of 100,000 weather balloons. Tests were conducted, and plans made.

These balloons were designed to be inflated to 8 ft in diameter. At launch a slow burning fuse was lit, and the balloons ascended rapidly, stopping at 25,000 ft as an internal band stopped further expansion. As the hydrogen used to inflate the balloons slowly leaked away they descended. The fuse would eventually release a small opening in a bucket of mineral oil, and as it leaked away the balloon descended faster.

About half the balloons carried a wire payload. The same fuse that released the mineral oil would also release a coil of wire held by hemp rope to the balloon. The balloon was calculated to maintain an altitude of at least 1,000 feet so that it would keep moving (below that the air can become very calm). In theory, the wire could short circuit high voltage lines, or break transformers.

The other half the balloons carried an incendiary payload. This was either cans of incendiary jelly, bottles of phosphorus grenades, or canvas tubes filled with explosive and fuses. These were all designed to create small fires. These also were items already on hand and easily and cheaply made.

There is a kind of genius in turning an accident, with knowledge, existing supplies, and some creativity, into a weapon.

In the latter half of 1942 the British launched between 1,000 and 1,800 balloons a day from a golf course in Felixstowe and a bay near Dover. All releases were clustered over 3 or 4 hours of a given day. Over 99,000 balloons were launched, and caused a great deal of havoc, confusion, and cost for the Germans. The biggest impact was from a balloon that hit a power line near Leipzig, and caused a fire that burned down the electrical station.

Launches were suspended during Allied bombing raids, for fear they would interfere with aircraft. In mid 1944, because of the great frequency of bombing raids, the release schedule was changed to single releases every 10 minutes during daylight hours. The last balloon was launched in September of 1944.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

SciTech Tuesday: Radar Research Led to Astronomical Discoveries

JS Hey died on 27 February of 2000, at the age of 81.

Born in Lancashire, England, he was the third son of a cotton manufacturer. He entered University of Manchester and got his degree in physics in 1930, and a masters in x-ray crystallography in 1931.

Hey taught physics at schools in Northern England until 1942, when he joined the Army Operational Research Group. We was assigned to work on radar jamming. At that point the Allies were using a form of radar with relatively long waves. Axis forces could not only detect this radar, but jam it. Using radar jamming two German warships had recently escaped through the English Channel. At the same time the Allies were losing an unsustainable tonnage of cargo to U-Boats in the Atlantic.

75 years ago this month Hey was monitoring radar jamming when he noticed a great deal of noise in the 4-8 m jamming Allied radar sets. Following the source, he noticed that it moved slowly, tracking the sun. Looking up meteorological data, he discovered that the Sun had a very active solar spot that day. Solar spots had been hypothesized to produce streams of ions and magnetic fields. Hey interpreted the phenomenon of the radar jamming as support of this hypothesis.

Development of radar using much shorter waves generated by the cavity magnetron allowed the Allies to avoid jamming by the Axis powers. Using this microwave radar Hey was tracking V2 rockets heading towards London in 1945 when he noticed transient radar echoes at about 60 miles of altitude. The echoes arrived at a rate of 5-10 per hour and persisted after the V2s were gone. It turned out the echoes were the vapor trails of meteors, and Hey showed that meteors could be tracked this way in the day when they were not visible to the eye.

JS Hey was not able to publish his results until after the war, for security reasons. Shortly after the war he was appointed to head the Army Operational Research Group, and he worked at the Royal Radar Establishment, where he continued his work in radio astronomy.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

SciTech Tuesday: The 75th Anniversary of the Battle of Los Angeles

The night of February 24, 1942, and the hours before dawn of the 25^th, the sky over Los Angeles was lit by search lights, the city was under a blackout, and more than 1.400 shells were shot from .50 caliber guns into the air. When the all-clear was sounded at 7:21 AM on the 25^th, the only casualties were buildings and cars hit by shell fragments, and 3 civilians killed in car accidents.

The immediate cause of the false alarm was a rogue weather balloon. When spotted from the ground by nervous watchers, lit from underneath by search lights, it was identified as an enemy aircraft.

The real cause was nervousness and a heightened watchfulness that resulted from events on the previous day, a short ways up the California coast.

On the evening of February 23, President Roosevelt delivered a fireside chat radio broadcast. Less than three months since the attack on Pearl Harbor, the nation was anxious, and in the midst of preparations for war. In the speech, Roosevelt said “…the broad oceans which have been heralded in the past as our protection from attack have become endless battlefields on which we are constantly being challenged by our enemies.’’ In the weeks since Pearl Harbor the United States had heard more bad news of advancing Japanese forces across the Pacific Ocean and Asia, and U-boat attacks from the German Navy in the Atlantic.

Perhaps as a means to undermine Roosevelt’s confident speech, a Japanese submarine patrolling the West Coast surfaced offshore north of Santa Barbara, and launched 13 shells towards oil wells and equipment in Ellwood, CA. It completely missed the gasoline plant there, caused minor damage to the piers and wells, and stayed 2,500 yards offshore, but the submarine’s impact on popular anxiety was great. The night of the shelling the Army Air Force sent a handful of pursuit planes and bombers to find the submarine, but was loath to commit more forces.

Intelligence supplied by loyal Japanese Americans had suggested that there might be some action to disturb the President’s speech. It also suggested that Los Angeles might be attacked the next night. The state of readiness itself led to the false alarm.

Confused reports from the night of the event, secrecy after it, and anxiety led to many conspiracy theories. This might even be counted as one of the first major events in the history of UFO conspiracies. Radar sightings of the objects triggering the artillery fire suggested they were moving far too slowly to have been planes. The use of radar for these purposes was new, and inexperienced operators may have been part of the problem. Visual sighting under night conditions is unreliable. Without context objects like weather balloons in the sky, especially with uncertain lighting, are difficult to scale.

The event led to better coordination of civilian and military defenses on the West Coast, and to more surveillance of activities and objects around plants and other installations near the shore. It might also have contributed to popular sentiment in support of Japanese Internment. Roosevelt had authorized Executive Order 9066 just days before.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

SciTech Tuesday: Radio and the Electromagnetic Spectrum

Today, TV screens are everywhere. There are several in most American homes, most restaurants and bars have them, they dominate the electronics sections of stores.

During WWII, radio filled that niche in electronics and mass communication. During national elections and other big events or disasters today, we gather around televisions to find out what is happening. During World War II, families gathered around radios. They had their days to hear their favorite programs, as I remember Sunday nights watching nature programs on TV with my family.

The technology underlying the radio and the television are basically the same. Manipulation of an electromagnetic field creates waves in a part of the electromagnetic spectrum at the transmitter. At some distance these waves are turned into an electrical current again by a receiver. In radios the receiver’s current makes a magnet attached to a paper or fabric cone move and generate sound waves. In the original televisions, the current was used in a cathode-ray tube (CRT) to make patterns on a phosphorescent screen. Today’s televisions put a current through a matrix of materials that responds to current by making different colors.

The original radio waves transmitted by Marconi in the 1890s could only travel a couple of miles. Since then, engineers have developed ways to make all sorts of different electromagnetic waves. These made radio better, but also made RADAR possible, and microwaves, and x-ray machines (the first x-rays were made with radioactive material but now they use electronically generated energy).

We are constantly in fields of anthropogenic electromagnetic waves. They come unintentionally from the electricity in the buildings we live in. The come intentionally from all sorts of devices. The many remote controls in a home, the cell phones, wireless phones, Wi-Fi routers, Bluetooth devices—all of these use electromagnetic waves to communicate at a distance. (As an aside, land-line phones and cable signals come into your home as electrical currents, but satellite services uses waves).

Much of the consumer technology of the last century has been about finding better and better ways to harness electromagnetic waves. Amplitude modulation (AM) of waves was replaced by Frequency Modulation (FM)—although AM is still used and has its uses. Broadcasters have recently been adding HD signals, which can contain more information in waves. That’s why multiple broadcast “stations” can be received at a single frequency of waves.

World War II was a huge time for the expansion of this engineering. Necessity then for portable radios drove miniaturization and vacuum-tube technology. RADAR development created shorter wavelength generation. Cleaning up radio reception led to the discovery of cosmic background radiation and also led to radio astronomy.

Compared to 75 years ago, the technology we use today to communicate and entertain may seem completely different. But in essence it is still the manipulation of electricity to make electromagnetic waves to be received at a distance.

You can find archived radio news broadcasts from WWII here.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum.