Steel worker reveals blocking view of U.S. aircraft on day of atomic bombing | Hacker News Reader

Steel worker reveals blocking view of U.S. aircraft on day of atomic bombing

mainichi.jp

155 pointsdevchuk41 comments

I wanted to know if this was plausible, so I located the Yawata Steel Works (the source of the smoke screen) and the Kokura Arsenal (the aiming point for the bomb) on a map. They were about 4.4km apart.

http://i.imgur.com/nJaJtH7.png (the site of the Steel Works is on the left)

Interesting, but I still don't know if it's true.

edit: Wikipedia's page on Smokescreens says "One 50 gallon drum of fog oil can obscure 60 miles (97 km) of land in 15 minutes", so I suppose it was easily possible for them to have hidden the target if the wind direction was right

Google Maps link: https://www.google.com/maps/place/%E4%B8%AD%E5%A4%96%E7%82%8...

97 square kilometers? 97 kilometer radius? tsk tsk Wikipedia…

I assume it means 97 square kilometers, because covering a circle of 97 km radius in 15 minutes would require a 776 km/hour wind :)

But it is written very unclearly, and it's not clear what is wikipedia's source, sadly.

It just seemed plausible that there could be plenty of smoke coverage for the scenario under discussion

Yeah, i'm not even sure that specifying just one unit is even sufficient for me to understand what they mean.

Presumably plume size is determined by a variety of factors, not just fuel?

So I read this as "within 15 minutes, land up to 60 miles downwind of the generator is obscured."

Wouldn't that require 240mph winds, though?

... yeah. Oops. Guess that reading's out.

What's wrong with the second one?

hit the edit button

Hard to edit when I don't know what it's supposed to say.

Are you really 'tsk'-ing at wikipedia? You know it's not guaranteed to be accurate on any topic at all don't you?

Is anything guaranteed to be accurate on any topic?

Seems to me that the official report would have mentioned "a giant smoke plume clearly originating from this one site was obscuring the target area" rather than reports of smoke and clouds covering the whole city.

It seems reasonable to me that the attempt may have been made, but I doubt it was responsible for actually averting the attack.

A couple of photos of what a smokescreen covering a city looks like http://449th.org/ploesti.php

It's for a German city, but it is the same idea.

correction: for a Romanian city - http://en.wikipedia.org/wiki/Ploie%C8%99ti

Does the Trolley problem apply here? (i.e. diverting the enemy from your town, if you know it is likely they will just attack the next town over) http://en.wikipedia.org/wiki/Trolley_problem

Maybe we can see it as a type of market in which participants simply tried to keep bombers away from their own city, without considering the effects on other cities? Over time, competition within this macabre market would produce increasingly efficient and effective means of repelling bombers. If the cities had cooperated, rather than competing, maybe they would have not evolved such efficient countermeasures?

A competitive strategy could produce a net benefit for all the cities, because diverted bombers might be less likely to carry out an effective attack on their secondary target.

In fact, that's what happened in this case (assuming the smokescreen had an effect). By the time the bomber diverted from Kokura to Nagasaki, it was so short of fuel that it could only attempt one bombing run. Visibility was poor, and the bomb detonated off target above a valley, with the result that parts of the city were shielded. The death toll of 40-80,000 was 'only' about half that of Hiroshima, despite the bomb being more powerful

edit: The outcome could have been even better, because the orders for the mission stated that they had to clearly see the target. If not, they were to return with the bomb. Really, it sounds like they ignored these orders, perhaps because they didn't have enough fuel to carry the bomb back.

I don't think so exactly, if you prevent the bombing on your city you're increasing the chance they get shot down, they get lost, they return to base, they run out of fuel etc etc.

No. This guy was saving his own life and there was no certainty the bomb would be dropped on someone else - or whom or how many.

You are never on the tracks. That would change the experiment, right? It would be self-defense and not much of a moral dilemma (that many people would struggle with or hold against you, I assume).

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

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

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.

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

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.

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_

Note that this wasn't due to trouble with calculating groundspeed, it just turned out that figuring out where a bomb would hit requires way more than just altitude, groundspeed, and position. Still, the fact that it's complicated is quite relevant here, especially since the bomb was dropped with a parachute. Somewhat counterintuitively, bombing accuracy was a pretty big driver behind a lot of the nuclear arms race, and improving accuracy is why bombs increased in power rapidly up to the 60s, then gradually declined.

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.

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

edit2: Bomber crew member's diary which explains what happened over Kokura - http://www.mphpa.org/classic/COLLECTIONS/CG-ASPI/01/Pages/CG...

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.

I'm reading this page here: 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

So, in addition to the nuclear models, they dropped identical conventional bombs of that type as well. Never knew that.

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/CG...

The mass murder, yeah, great stuff.

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.

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.

It's interesting to read Wikipedia's entry on this matter (claiming it was caused by a huge firebombing raid):

http://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_an...

"The delay at the rendezvous had resulted in clouds and drifting smoke from fires started by a major firebombing raid by 224 B-29s on nearby Yahata the previous day covering 70% of the area over Kokura, obscuring the aiming point."

Yep, one of the reasons Hiroshima and Nagasaki were selected as targets was because they were one of the few major Japanese cities that /hadn't/ been firebombed in the preceding weeks. People forget that the deadliest 24 hours in the Second World War was not either of the atomic bombings (which killed c. 120,000 people), but the firebombing of Tokyo, which burned down 12 square miles of a city which had average population density of 100,000 people per square mile.

Also, Kyoto was one of the original targets but because of its cultural significance it was replaced with Nagasaki.

Thank goodness, though. The bombings were a bad idea, but at least they didn't bomb Kyoto!

Ok, so the target area was blocked. So what? This was not a precision ammo, it was an a-bomb! Even those early designs could just be detonated in the general area and still destroy the target and everything else.

Why did the bombers have to switch targets then?

This is not quite true; the Nagasaki bomb missed its target by almost two miles because of cloud cover, and as a result only half the number of people were killed compared to Hiroshima. Even with an atomic bomb you had to be /relatively/ precise. (Source: https://www.youtube.com/watch?v=kYphE841lfY)

I am guessing here but I believe the bombings of Hiroshima and Nagasaki were also weapons tests. And you want a clear field of vision to perform a precise test.

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