Comments on: Architects of preservation http://airminded.org/2008/07/29/architects-of-preservation/ Airpower and British society, 1908-1941 Fri, 09 Jan 2009 13:15:37 +0000 http://wordpress.org/?v=2.6.5 By: Brett Holman http://airminded.org/2008/07/29/architects-of-preservation/#comment-79197 Brett Holman Tue, 29 Jul 2008 12:27:25 +0000 http://airminded.org/?p=534#comment-79197 Actually, I'm not sure where that figure of 30' came from! Looking at it again, the roof is only 13.5' (7 feet of earth, 6.5 of -- presumably -- reinforced concrete) thick. Below that is the entrance level, which is 8.5' high. I was assuming that would be empty (not sure why, actually) but still that offers no extra protection. And then after that the floor of the ramp is only 0.5' thick, which seems very thin indeed! Still, the roof was layered (earth, concrete, earth, concrete), which accorded with the latest thinking on best protection. And they did provide thicker walls on the sides at the top, to give extra protection against glancing blows. No, I haven't seen anything about experimental data on blast damage etc, that I can recall. (There is some stuff on gas protection from civilian scientists.) You have to wonder why -- it seems like an obvious thing to do. But operational research was still in its infancy;and the RAF didn't set up its first bombing development unit until September 1939! Actually, I’m not sure where that figure of 30′ came from! Looking at it again, the roof is only 13.5′ (7 feet of earth, 6.5 of — presumably — reinforced concrete) thick. Below that is the entrance level, which is 8.5′ high. I was assuming that would be empty (not sure why, actually) but still that offers no extra protection. And then after that the floor of the ramp is only 0.5′ thick, which seems very thin indeed! Still, the roof was layered (earth, concrete, earth, concrete), which accorded with the latest thinking on best protection. And they did provide thicker walls on the sides at the top, to give extra protection against glancing blows.

No, I haven’t seen anything about experimental data on blast damage etc, that I can recall. (There is some stuff on gas protection from civilian scientists.) You have to wonder why — it seems like an obvious thing to do. But operational research was still in its infancy;and the RAF didn’t set up its first bombing development unit until September 1939!

]]> By: Jakob http://airminded.org/2008/07/29/architects-of-preservation/#comment-79186 Jakob Tue, 29 Jul 2008 11:17:24 +0000 http://airminded.org/?p=534#comment-79186 30 feet seems quite deep to me, especially as GP bombs didn't have any great ground-penetrating capability, but I have no idea what the blast effect of (eg.) a 1000kg bomb on top of the shelter would be. I'd guess that the shockwave would be mostly dissipated by the earth, but that's not supported by any actual evidence :) Thinking more about this: have you found any damage data that were based on actual tests rather than extrapolated from a previous war? I'm thinking of things like the nuclear bomb effects slide rules that I've seen in civil defence books - I vaguely recall someone has even built a webpage that lets you enter details and survey the destruction... As for cost-effective, that shelter looks huge - I can see the one-off capital outlay needed for one of those being off-putting to government compared with the slow trickle needed to dig trenches and reinforce cellars, but again this is just musing. Of course for cost-effectiveness tube stations were very hard to beat. 30 feet seems quite deep to me, especially as GP bombs didn’t have any great ground-penetrating capability, but I have no idea what the blast effect of (eg.) a 1000kg bomb on top of the shelter would be. I’d guess that the shockwave would be mostly dissipated by the earth, but that’s not supported by any actual evidence :)

Thinking more about this: have you found any damage data that were based on actual tests rather than extrapolated from a previous war? I’m thinking of things like the nuclear bomb effects slide rules that I’ve seen in civil defence books - I vaguely recall someone has even built a webpage that lets you enter details and survey the destruction…

As for cost-effective, that shelter looks huge - I can see the one-off capital outlay needed for one of those being off-putting to government compared with the slow trickle needed to dig trenches and reinforce cellars, but again this is just musing. Of course for cost-effectiveness tube stations were very hard to beat.

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