Retrotechtacular: Radar Jamming

It’s been said that the best defense is a good offense. When aloft and en route to deliver a harmful payload to the enemy, the best defense is to plan your approach and your exit carefully, and to interfere with their methods of detection. If they can’t find you, they can’t shoot you.

As of May 1962, the United States military was using three major classifications of radar jamming technology as described in this week’s film: the AN/ALQ-35 multiple target repeater, the AN/ALQ-55 communications link disrupter, and the AN/ALQ-41 and -51 track breakers. The most important role of these pieces of equipment is to buy time, a precious resource in all kinds of warfare.

The AN/ALQ-35 target repeater consists of a tuner, pulse generator, transmitter, and control panel working in concert to display multiple false positives on the enemy’s PPI scopes. The unit receives the incoming enemy pulse, amplifies it greatly, repeats it, and sends them back with random delays.

The AN/ALQ-55 comm disrupter operates in the 100-210MHz band. It distinguishes the threatening enemy communication bands from those of beacons and civilians, evaluates them, and jams them with a signal that’s non-continuous, which helps avoid detection.

Finally, the AN/ALQ-41 and -51 track breakers are designed to break enemy lock-on and to give false information. It provides simultaneous protection against pulse ranging, FM-CW, conical, and monopulse radar in different ways, based on each method’s angle and range.

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Retrotechtacular: Stateside Assembly and Launch of V-2 Rockets

At the end of World War II, the United States engaged in Operation Paperclip to round up German V-2 rockets and their engineers. The destination for these rockets? White Sands Proving Grounds in the New Mexico desert, where they would be launched 100 miles above the Earth for the purpose of high altitude research.

This 1947 War Department Film Bulletin takes a look inside the activities at White Sands. Here, V-2 rockets are assembled from 98% German-made parts constructed before V-E day. The hull of each rocket is lined with glass wool insulation by men without masks. The alcohol and liquid oxygen tanks are connected together, and skins are fitted around them to keep fuel from leaking out. Once the hull is in place around the fuel tanks, the ends are packed with more glass wool. Now the rocket is ready for its propulsion unit.

In the course of operation, alcohol and liquid oxygen are pumped through a series of eighteen jets to the combustion chamber. The centrifugal fuel pump is powered by steam, which is generated separately by the reaction between hydrogen peroxide and sodium permanganate.

A series of antennas are affixed to the rocket’s fins. Instead of explosives, the warhead is packed with instruments to report on high altitude conditions. Prior to launch, the rocket’s tare weight is roughly five tons. It will be filled with nine tons of fuel once it is erected and unclamped.

At the launch site, a gantry crane is used to add the alcohol, the liquid oxygen, and the steam turbine fuels after the controls are wired up. The launch crew assembles in a blockhouse with a 27-foot-thick roof of reinforced concrete and runs through the protocol. Once the rocket has returned to Earth, they track down the pieces using radar, scouting planes, and jeeps to recover the instruments.

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Retrotechtacular: Using the Jet Stream for Aerial Warfare

Unmanned Aerial Vehicles (UAV) are all the rage these days. But while today’s combative UAV technology is as modern as possible, the idea itself is not a new one. Austria floated bomb-laden balloons at Venice in the middle 1800s. About a hundred years later during WWII, the Japanese used their new-found knowledge of the jet stream to send balloons to the US and Canada.

Each balloon took about four days to reach the western coast of North America. They carried both incendiary and anti-personnel devices as a payload, and included a self-destruct. On the “business end” of the balloons was the battery, the demolition block, and a box containing four aneroid barometers to monitor altitude. In order to keep the balloons within the 8,000 ft. vertical range of the jet stream, they were designed to drop ballast sandbags beginning one day into flight using a system of blow plugs and fuses. In theory, the balloon has made it to North American air space on day four with nothing left hanging but the incendiaries and the central anti-personnel payload.

Although the program was short-lived, the Japanese launched some 9,300 of these fire balloons between November 1944 and April 1945. Several of them didn’t make it to land. Others were shot down or landed in remote areas. Several made the journey just fine, and two even floated all the way to Michigan. Not bad for a rice paper gas bag.

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Retrotechtacular: The Bessemer Converter

Here’s a rose-colored look into the steelworks at Workington, Cumbria in northern England. At the time of filming in 1974, this plant had been manufacturing steel nonstop for 102 years using the Bessemer process. [Sir Henry Bessemer]’s method for turning pig iron into steel was a great boon to industry because it made production faster and more cost-effective.

hot ingotsMore importantly, [Bessemer]’s process resulted in steel that was ten times stronger than that made with the crucible-steel method. Basically, oxygen is blown through molten iron to burn out the impurities. The silicon and manganese burn first, adding more heat on top of what the oxygen brings. As the temperature rises to 1600°C, the converter gently rocks back and forth. From its mouth come showers of sparks and a flame that burns with an “eye-searing intensity”. Once the blow stage is complete, the steel is poured into ingot molds. The average ingot weighs four tons, although the largest mold holds six tons. The ingots are kept warm until they are made into rail.

The foreman explains that Workington Works would soon be switching over to a more modern process. As it was, Workington ran a pair of Bessemer converters on a 40-minute schedule, ensuring constant steel production from ore to rail. Between 1872 and 1974, these converters created an estimated 25 million metric tons of steel.

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Retrotechtacular: Wising Up with the SAGE System

The birth of the supersonic jet made the United States’ airstrike defenses look antiquated. And so, during the Cold War, the government contracted a number of institutions and vendors to create and maintain the Semi-Automatic Ground Environment (SAGE) aircraft detection system with Western Electric as project manager.

SAGE was developed at MIT’s Lincoln Laboratory on computers built by IBM. It used the AN/FSQ-7 in fact, which was The Largest Computer Ever Built. SAGE operated as a network of defense sectors that divided the continental U.S. and Canada. Each of these sectors contained a directional center, which was a four-story concrete blockhouse that protected and operated a ‘Q7 through its own dedicated power station. The SAGE computers employed hot standby processors for maximum uptime and would fail over to nearby direction centers when necessary.

Information is fed into each directional center from many radar sources on land, in the air, and at sea. The findings are evaluated on scopes in dimly-lit rooms on the front end and stored on magnetic cores on the back end. Unidentifiable aircraft traces processed in the air surveillance room of the directional center are sent to the ID room where they are judged for friendliness. If found unfriendly, they are sent to the weapons direction room for possible consequences.

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Retrotechtacular: Basic Telephony in the Field

Here is a great introduction to a practical application of electromagnetic theory—the field telephone. It’s a training film from 1961 that covers the sound-powered, local battery, and common battery systems along with the six basic components they use: generators, ringers, transmitters, receivers, induction coils, and capacitors.

Clear illustrations and smart narration are the hallmarks of these Army training films, and this one begins with a great explanation of generator theory. The phone’s ringer uses electromagnetic attraction and repulsion to do the mechanical work of striking the bells. Similarly, the sound waves generated by a caller’s speech move an armature to create an alternating electrical current that is transmitted and converted back to sound waves on the receiving end.

In the local battery system, the battery pushes pulsating DC to carry the voice transmission. An induction coil increases the capabilities of this system, but capacitors are required to filter out the frequencies that would overload the receiver, passing only the higher speech frequencies.

In order for several stations to communicate, the use of a switchboard is required to patch the calls through. There are many advantages of a common battery system with regard to call switching: no local battery is necessary, nor is a generator needed at each station. Calls are easier to place, and communication is much faster.

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Retrotechtacular: On the Wings of Goodyear

At the opposite end of the spectrum from the various blimp and rigid-hull airships Goodyear has created over the years stands the Goodyear Inflatoplane, the company’s foray into experimental inflatable aircraft. Goodyear had recently created a rubberized nylon material they called Airmat, the faces of which were connected internally by nylon threads. This material was originally developed during research into the viability of emergency airplane wings.

The United States military became interested in the Inflatoplane after Goodyear had performed successful testing of demonstration model GA-33. They believed that the Inflatoplane could be dropped from the air in a rigid container to facilitate an emergency rescue, or trucked around with the rest of the cargo as a last resort for just exactly the right situation. It seems like a good idea on paper. The Inflatoplane could stay packed into a fairly small container until it was needed. The GA-468 one-seater model could go almost 400 miles on 20 gallons of fuel, and required less pressure to inflate than the average car tire.

This episode of the Discovery Channel series WINGS includes a real-time demonstration of taking an Inflatoplane from crate to air set to late ’80s montage music. It takes the pilot a full five minutes to unfurl and  the plane, and he does it on a nice and level grassy spot by a lake that looks more like a cozy picnic spot than threatening enemy territory. While it’s better than not having an inflatable emergency aircraft, it just isn’t that practical.

Goodyear had all kinds of plans for future improvements, such as a vertical takeoff model and a rocket-powered version. But the Inflatoplane military initiative was grounded around the time that someone speaking for the Army deadpanned that they “could not find a valid military use for an aircraft that could be taken down by a well-aimed bow and arrow.”

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