This is the first of a new catagory of posts related to 1936. The point of these is to gather interesting trivia about the 1930's period of the ROCKETMAN games I some times run with my friends. Any one who knows of similar arcane technological relics is welcome to bring them to my attention.
So, how do you detect enemy aircraft when you haven't gotten around to discovering radar yet? The answer is simple enough. You build big acoustic mirrors and you just listen for them. That was the cutting edge of air defence detection in the 1920's and early 1930's and the British in particular went to some lengths to establish an air detection network across their southern coasts. The above image shows the vast fully operational 200ft mirror at Dungeness (Kent) demonstrating perfectly the simple operational principle. The curve of the mirror reflects sound waves to a focus point where a microphone can pick up any sounds for further amplification. Simple. The British only seem to have built two really large mirrors (the other being on the Mediterranean island of Malta) and these had a range of 15-25 km. At Dungeness there are three different mirrors, each a different size, and many of the smaller mirrors, see image below, were built around England. Unfortunately, given the speed of aircraft at the period, these devices were only able to provide a maximum warning of about 4 minutes, and by the late 1930's they were already being made obsolete by the advent of radar which is in some ways merely the same principles taken to a higher level of sophistication. When the Second World War broke out the acoustic mirror network had already been rendered obsolete, but its legacy was such that despite the British radar system being technically inferior to the German system, the already established network of the Acoustic mirror system gave the British an operational edge.
http://www.ajg41.clara.co.uk/mirrors/dungeness.html
Naturally Kate Bush was already inspired by martial acoustic experiements...
http://www.songfacts.com/detail.php?id=4846
http://en.wikipedia.org/wiki/Experiment_IV
The second image below shows a similar acoustic detector. It is a Japanese 'War Tuba'. A portable listening device based on a different principle, but equally as arcane.
6 comments:
Wow!
That is really awesome. It's amazing what people will come up with when they really have to. It's amazing how much stuff we've invented in the last 100 years.
"War tubas" are you serious? Where they serious? I can see them trundling across the table now protected by a squad of troops as an airship floats into view.
Moif you are beginning to get me interested in a period I can't afford to play!
Heh ... They can't be any worse than Bag pipes! I hadn't actually condsidered using any 'War Tuba's' in ROCKETMAN... at least not in the upcoming cycle of games, but now that you mention airships...
Ya gotta love them though don't ya? With their cute little spoked wheels.
Oh Wow!
The mirrors are *passive* sonar, which sounds quite cool (for spotting battleships in fog [or Martian war-machines]? actually it might see 'over the horizon' over the surface of the sea, given the right frequencies... anybody know anything about modern passive sonar?).
So how the ### does a war tuba work?
I'm guessing its like a gigantic ear trumpet and you stick the narrow end in your ear...
Sounds dangerous.
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