A lot of science museums and parks feature something called an acoustic mirror. The one at Houston’s Discovery Green park is called the listening vessels. [Doug Hollis] created two acoustic mirrors 70 feet apart, pointing at each other. If you stand or sit near one of the vessels, you can hear a whisper from someone near the other vessel. The limestone installations (see right) are concave and focus sound like a parabolic mirror will focus light.
Just a science curiosity, right? Maybe today, but not always. The story of these devices runs through World War II and is an object lesson in how new technology requires new ways of thinking about things.
Continue reading “Acoustic Mirrors: How to Find Planes without RADAR”
When the USA entered World War Two, they lacked a powerful mobile communications unit. To plug this gap they engaged Hallicrafters, prewar manufacturers of amateur radio transmitters and receivers, who adapted and ruggedized one of their existing products for the application.
The resulting transmitter was something of a success, with production running into many thousands of units. Hallicrafters were justifiably proud of it, so commissioned a short two-part film on its development which is the subject of this article.
The transmitter itself was a very high quality device for the era, but even with the film’s brief insight into operating back in the AM era the radio aspect is not what should capture your interest. Instead of the radio it is the in-depth tour of an electronics manufacturing plant in the war years that makes this film, from the development process of a military product from a civilian one through all the stages of production to the units finally being fitted to Chevrolet K-51 panel vans and shipped to the front. Chassis-based electronics requiring electric hoists to move from bench to bench are a world away from today’s surface-mount micro-circuitry.
So sit back and enjoy the film, both parts are below the break.
Continue reading “Retrotechtacular: Hallicrafters Goes To War”
Boeing’s B-17 was the most numerous heavy bomber of World War II, and its reputation of being nigh indestructible in the face of Messerschmidts and flak cannons is stuff of legend. The first flight of the B-17 was in 1935, and a decade later at the close of World War II, the B-17 would begin to show its age. It could only carry 6,000 pounds of ordnance; the first atomic bombs, Little Boy and Fat Man, weighed 9,700 pounds and 10,300 pounds, respectively. The Avro Lancaster notwithstanding, a new aircraft would be needed for the Allied invasion of Japan. This aircraft would be the Boeing B-29 Superfortress.
On paper, the B-29 nearly holds its own against all but the most modern bombers of aviation history. Yes, the B-29 is slow, but that’s only because jet engines were in their infancy in 1944. This bomber was a forgotten super weapon of World War II, and everyone – Japan, German, Great Britain and the USSR – wanted their own. Only the Soviets would go as far to build their own B-29, reverse engineering the technology from crashed and ditched American bombers.
Continue reading “Stolen Tech: The Soviet Superfortress”
Winston Churchill once told Joseph Stalin “In wartime, truth is so precious that she should always be attended by a bodyguard of lies”. During World War II, the power of these bodyguards, in the form of military deception, became strikingly apparent. The German military was the most technologically advanced force ever encountered. The Germans were the first to use jet-powered aircraft on the battlefield. They created the enigma machine, which proved to be an extremely difficult system to break. How could the Allies possibly fool them? The answer was a mix of technology and some incredibly talented soldiers.
The men were the 23rd Headquarters Special Troops, better known as the Ghost Army. This unit was the first of its kind specifically created to deceive the enemy. Through multiple operations, they did exactly that. These 1100 soldiers created a diversion that drew German attention and gunfire to them, instead of the thousands of Allied troops they were impersonating.
The Ghost Army consisted of 4 distinct groups:
- The 406th Engineer Combat Company Special were 166 “regular” soldiers – these men handled security, construction, and demolition.
- 603rd Camouflage Engineers were the largest group at 379. As the name implies, the 603rd was created to engineer camouflage.
- 3132 Signal Service Company consisted of 145 men in charge of half-tracks loaded down with massive 500 watt speakers which could be heard for 15 miles.
- The Signal Company Special Formerly the 244th signal company, The 296 men of the Signal Company Special handled spoof radio communications. The Germans heavily relied on captured and decoded radio messages to determine the Allies’ next move.
Continue reading “Rubber Tanks and Sonic Trucks: The Ghost Army of World War II”
Look closely above and you’ll see there’s a section of track missing. There are actually two, a section from each side has been plucked out with a pair of eight-ounce plastic explosive charges — and yet the train keeps barreling onward. The World War II era reel is demonstrating some military testing of the effect of damaged tracks on a train. The amount of missing track the train can stand up to came as quite a surprise for us!
The test setup itself is neat. An old derelict locomotive is used. It, as well as a number of trailing cars, is pushed by a functioning engine from behind. Once up to about 26 MPH the pusher stops and the rest keep going. There are many tests, starting with just a few inches of track missing from one side. This gap is increased, then gaps are added both sides, then the two sides are offset. Even a 5-foot gap is crossed easily by the locomotive. The weak link turns out to be the empty cars. We suppose their mass is small enough that they can’t rely on inertia to keep them on the straight path.
If you don’t appreciate the destructive nature of this Retrotechtacular installment, you can still get your train fix. There is another offering which shows off the modernization of a signaling system.
Continue reading “Retrotectacular: The Science of Derailing Trains”
[Timo] tipped us off about a War Monument that has been… upgraded. The story starts when a monument was erected in Cherkassy, Ukraine to commemorate the ultimate sacrifice that was made by Russian soldiers during World War II. The huge statue and expansive plaza were capped off by an eternal flame. Unfortunately, when the Soviet Block broke up, the natural gas that had been provided by the government became a luxury so the flame was extinguished.
The eternal flame sat unlit, a sad commentary to the remembrance of the dead. But how to fix this issue? As cell phone companies came into the area, a need for cell phone towers arose. At some point a solution was reached; a cell phone tower was built in the bowl of the eternal flame and then wrapped with an LED marquee. The marquee now displays the image of a flame in perpetuity.
We’re not quite sure what to think about this. After some adjustment, the substitution of LEDs for flames will probably become accepted. The monument is now providing a useful purpose for the living, and once again shows a flame. We think that having something there showing that the memory is still alive is much better than the message an unkempt derelict sends.