4 ms·

How much coal tar would you need to burn to block an airplane's view?

ekianjo 12y ago
Not sure, but it seems a little bit unlikely that the smoke could be enough to obstruct the vision of a plane cruising at 30000+ feet.
- marvin 12y ago
  Smokescreens were widely used as a defensive tactic during World War 2. Assuming that the bombing crews are attempting to hit a target rather than just indiscriminately bomb an area of several square kilometers, they were very effective before the advent of infrared cameras all-weather radar. Smokescreens do require relatively calm winds though. You could e.g. read "Target Tirpitz" which is a historical account documenting among other things how smokescreens were used to defend Germany's biggest battleship against a large number of bombing runs. A battleship is pretty much the biggest target you could have on a battlefield, showing that this tactic is very effective against non-indiscriminate bombing.
- cleverjake 12y ago
  the visibility of the city isn't affected by the height of the plane. they weren't trying to smoke out the plane, just cover the place they lived.
- deleted 12y ago
  [deleted]
- FatalLogic 12y ago
  They only had to obscure the target zone, which was a very small area (a single factory complex, the Kokura Arsenal), and by chance it happened to be obscured during the 30 minutes or so that the plane was overhead. This wasn't a normal bombing run. It had elements of an experiment - they wanted to understand how the bomb worked, so they wanted to control the drop precisely and be able to observe the effects. The aiming points were very precise (a bridge in the case of Hiroshima), and they were chosen well in advance, and the mission orders were quite rigid. If the crew couldn't see the target clearly after several attempts, they didn't have the authority to randomly drop the bomb somewhere else - they had to go on to the next city. Ironically, after all that, I think they eventually missed the aiming point in Nagasaki by 2 km or so, because it was also obscured. By then, the plane was low on fuel though, so I guess they were forced to do the best they could. I've read that they weren't supposed to do that, according to the mission rules. The plane came very close to running out of fuel, which I guess might have made them drop the bomb to reduce weight. edit: This is Field Order 13 - for the attack on Hiroshima. It includes Kokura and Nagasaki as secondary targets, so you can see how precise they were about the aiming points. I'm pretty sure the target details would be exactly the same for the Nagasaki attack (Field Order 17, which I can't find online). https://www.flickr.com/photos/kafaikan/6693719785/sizes/l https://www.flickr.com/photos/kafaikan/6693719785/sizes/l edit2: Bomber crew member's diary which explains what happened over Kokura - http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-024.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG...
  - dangayle 12y ago
    That diary is a fantastic read. The language, the drama, the bird's eye view of one of the most pivotal moments in world history. Beats fiction any day.
    - mjfisher 12y ago
      Also interesting to note is the partial redaction of a sentence immediately after the bomb was dropped a few pages later. It's been literally cut out of the paper: http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-026.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG...
    - ckozlowski 12y ago
      I'm reading this page here: http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-030.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG... Just thought I'd share some of my puzzlement here; but it sounded as if they'd dropped a third atomic bomb. I though this unlikely, unless the diary is revealing a secret kept (the drop sounds as if it'd failed), but then I came across this: http://en.wikipedia.org/wiki/Pumpkin_bomb http://en.wikipedia.org/wiki/Pumpkin_bomb So, in addition to the nuclear models, they dropped identical conventional bombs of that type as well. Never knew that.
    - HNJohnC 12y ago
      The mass murder, yeah, great stuff.
deleted 12y ago
[deleted]
swalsh 12y ago
How good of a view do you need dropping a bomb with a 1.3 kilometer blast radius?
- Patrick_Devine 12y ago
  I would imagine a pretty decent one if you want any kind of precision when you're 10km up in the air. You need to take your own ground speed into consideration, as well as the windspeed as the bomb is going to be in free fall for around 3/4 of a minute. Getting your ground speed would have been a real pain since you would have to have calculated it from your indicated air speed and guessed at the air density and winds aloft. Or you can time it by using fixed reference points below you... except those were being obscured and are still remarkably easy to get wrong when you're 10KM away.
  - mikeash 12y ago
    You just need one reference point to measure your groundspeed, and you don't have to know what it is, you can just pick any arbitrary feature below you. With a known altitude, measuring the angular velocity of a ground feature gives you your groundspeed. There were mechanical systems available by the 1920s or 30s that could do this automatically, perhaps most famously the Norden bombsight: http://en.wikipedia.org/wiki/Norden_bombsight http://en.wikipedia.org/wiki/Norden_bombsight Still, if you want to hit a target like this, you have to be able to see it, and see enough context around it to be able to recognize it.
    - Patrick_Devine 12y ago
      That's a fascinating article. It does mention that they weren't particularly useful though: _Over Japan, bomber crews soon discovered strong winds at high altitudes, the so-called jet streams, but the Norden bombsight worked only for wind speeds with minimal wind shear. Additionally, the bombing altitude over Japan reached up to 9,100 metres (30,000 ft), but most of the testing had been done well below 6,100 metres (20,000 ft). This extra altitude compounded factors that could previously be ignored; the shape and even the paint of the bomb mantle greatly changed the aerodynamic properties of the weapon, and, at that time, nobody knew how to calculate the trajectory of bombs that reached supersonic speeds during their fall_

Not sure, but it seems a little bit unlikely that the smoke could be enough to obstruct the vision of a plane cruising at 30000+ feet.

marvin 12y ago
Smokescreens were widely used as a defensive tactic during World War 2. Assuming that the bombing crews are attempting to hit a target rather than just indiscriminately bomb an area of several square kilometers, they were very effective before the advent of infrared cameras all-weather radar. Smokescreens do require relatively calm winds though. You could e.g. read "Target Tirpitz" which is a historical account documenting among other things how smokescreens were used to defend Germany's biggest battleship against a large number of bombing runs. A battleship is pretty much the biggest target you could have on a battlefield, showing that this tactic is very effective against non-indiscriminate bombing.
cleverjake 12y ago
the visibility of the city isn't affected by the height of the plane. they weren't trying to smoke out the plane, just cover the place they lived.
deleted 12y ago
[deleted]
FatalLogic 12y ago
They only had to obscure the target zone, which was a very small area (a single factory complex, the Kokura Arsenal), and by chance it happened to be obscured during the 30 minutes or so that the plane was overhead. This wasn't a normal bombing run. It had elements of an experiment - they wanted to understand how the bomb worked, so they wanted to control the drop precisely and be able to observe the effects. The aiming points were very precise (a bridge in the case of Hiroshima), and they were chosen well in advance, and the mission orders were quite rigid. If the crew couldn't see the target clearly after several attempts, they didn't have the authority to randomly drop the bomb somewhere else - they had to go on to the next city. Ironically, after all that, I think they eventually missed the aiming point in Nagasaki by 2 km or so, because it was also obscured. By then, the plane was low on fuel though, so I guess they were forced to do the best they could. I've read that they weren't supposed to do that, according to the mission rules. The plane came very close to running out of fuel, which I guess might have made them drop the bomb to reduce weight. edit: This is Field Order 13 - for the attack on Hiroshima. It includes Kokura and Nagasaki as secondary targets, so you can see how precise they were about the aiming points. I'm pretty sure the target details would be exactly the same for the Nagasaki attack (Field Order 17, which I can't find online). https://www.flickr.com/photos/kafaikan/6693719785/sizes/l https://www.flickr.com/photos/kafaikan/6693719785/sizes/l edit2: Bomber crew member's diary which explains what happened over Kokura - http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-024.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG...
- dangayle 12y ago
  That diary is a fantastic read. The language, the drama, the bird's eye view of one of the most pivotal moments in world history. Beats fiction any day.
  - mjfisher 12y ago
    Also interesting to note is the partial redaction of a sentence immediately after the bomb was dropped a few pages later. It's been literally cut out of the paper: http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-026.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG...
  - ckozlowski 12y ago
    I'm reading this page here: http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CGP-ASPI-030.htm http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG... Just thought I'd share some of my puzzlement here; but it sounded as if they'd dropped a third atomic bomb. I though this unlikely, unless the diary is revealing a secret kept (the drop sounds as if it'd failed), but then I came across this: http://en.wikipedia.org/wiki/Pumpkin_bomb http://en.wikipedia.org/wiki/Pumpkin_bomb So, in addition to the nuclear models, they dropped identical conventional bombs of that type as well. Never knew that.
  - HNJohnC 12y ago
    The mass murder, yeah, great stuff.

deleted 12y ago

[deleted]

swalsh 12y ago

How good of a view do you need dropping a bomb with a 1.3 kilometer blast radius?

Patrick_Devine 12y ago
I would imagine a pretty decent one if you want any kind of precision when you're 10km up in the air. You need to take your own ground speed into consideration, as well as the windspeed as the bomb is going to be in free fall for around 3/4 of a minute. Getting your ground speed would have been a real pain since you would have to have calculated it from your indicated air speed and guessed at the air density and winds aloft. Or you can time it by using fixed reference points below you... except those were being obscured and are still remarkably easy to get wrong when you're 10KM away.
- mikeash 12y ago
  You just need one reference point to measure your groundspeed, and you don't have to know what it is, you can just pick any arbitrary feature below you. With a known altitude, measuring the angular velocity of a ground feature gives you your groundspeed. There were mechanical systems available by the 1920s or 30s that could do this automatically, perhaps most famously the Norden bombsight: http://en.wikipedia.org/wiki/Norden_bombsight http://en.wikipedia.org/wiki/Norden_bombsight Still, if you want to hit a target like this, you have to be able to see it, and see enough context around it to be able to recognize it.
  - Patrick_Devine 12y ago
    That's a fascinating article. It does mention that they weren't particularly useful though: _Over Japan, bomber crews soon discovered strong winds at high altitudes, the so-called jet streams, but the Norden bombsight worked only for wind speeds with minimal wind shear. Additionally, the bombing altitude over Japan reached up to 9,100 metres (30,000 ft), but most of the testing had been done well below 6,100 metres (20,000 ft). This extra altitude compounded factors that could previously be ignored; the shape and even the paint of the bomb mantle greatly changed the aerodynamic properties of the weapon, and, at that time, nobody knew how to calculate the trajectory of bombs that reached supersonic speeds during their fall_