
The Cannons on the B-29 Bomber - seer
http://www.popularmechanics.com/military/weapons/a18343/the-cannons-on-the-b-29-bomber-were-a-mid-century-engineering-masterpiece/
======
madaxe_again
This article makes it out like gunning computers as a whole were some kind of
new and revolutionary technology - while it's a feat of miniaturisation and
lovely engineering, some of the earliest computers (either mechanical or
electromechanical) were specifically for gunnery. Firing an artillery or naval
shell 20 miles requires some pretty complex (well, if you're in a firefight -
it's not that hard but it's not "oh let me think about that a moment") maths
to compensate for aerodynamic effects, spin, and the Coriolis effect.

[https://en.wikipedia.org/wiki/Rangekeeper](https://en.wikipedia.org/wiki/Rangekeeper)
has a decent summary of the development of this tech.

~~~
Bjartr
Speaking of targeting computers, one of my favorite videos on YouTube is a
training film describing the theory of operation behind a purely mechanical
fire control computer by the US Navy circa 1953
[https://youtu.be/s1i-dnAH9Y4](https://youtu.be/s1i-dnAH9Y4)

~~~
bcoates
I love that film, but it's kind of weird that it doesn't mention what's
probably the most important invention that makes this type of computer
possible: The torque amplifier.

All the devices shown suffer power losses between input and output, some of
them severe. A torque amplifier has two shafts that are 1:1 geared for speed
but the output shaft has extra power taken from a third supply shaft, like the
supply to a logic gate that lets it drive more output power than it draws from
its inputs.

[https://en.wikipedia.org/wiki/Torque_amplifier](https://en.wikipedia.org/wiki/Torque_amplifier)

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jessaustin
This confirms for me a complaint I've always had about the Millennium Falcon.
A ship equipped with hyperdrive would certainly have had targeting systems as
good as a B-29. There would have been no need for the midships ladders to the
gun stations.

~~~
JoeAltmaier
But the best part of old WWII movies were the dogfighting scenes. And the
movie you reference was cribbed from there. So, poetic license.

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alricb
They're talking about M2 .50 heavy machine guns; the B-29 didn't have what are
considered "cannons" (usually 20 mm or more).

For the most part, defensive guns on bombers weren't all that useful; even
with a fire-control computer aiding you, it's very hard to hit a (possibly
maneuvering) moving plane from another moving plane. It would probably have
been better to omit those heavy guns and turrets and to leave those gunners on
the ground to save weight, lives, and resources.

~~~
hydrogen18
The guns on a bomber were never really meant for engaging aircraft. They're
meant to deter fighters from ever getting near the bomber. Not many pilots are
willing to sit directly in the path of machine gun fire, even if it is not
very accurate. German anti-aircraft figured this out as well. They switched to
shooting mostly tracer rounds. You aren't going to hit anything in the first
place, so you might as well just scare the crap out of them.

There were some WWII 'gunship' style modifications of planes, but that was not
that common.

For a more modern comparison, consider that the Bradley fighting vehicle
carries anti tank missiles. Sending a group of Bradleys directly against tanks
would be suicidal. The Bradley has aluminum for armor. A well trained set of
tank crews operating even WWII vintage vehicles would decimate them. Instead,
the misiles are there to deter tanks from engaging them. It also provides the
crew with an enormous psychological benefit. That benefit is they at least
have the benefit of being able to respond to an enemy tank with a potentially
lethal weapons system. Ironically of course the TOW missiles on the Bradley
destroyed more Iraqi tanks the M1 tank ever did in the Gulf war. But that is
because Iraqi tank crews either had no experience or had armored vehicles in
horrible condition.

~~~
Tloewald
Given that the Bradley was designed to fight Eastern Bloc forces on the plains
of Germany (which comprises rolling terrain, closely spaced villages, streams,
etc.) a vehicle that can be tucked behind cover and fire lethal anti-tank
missiles isn't just decoration.

One of the most interesting cold war AFVs was an M113 chassis with a cherry
picker and 15 TOW missiles on it. Armor is nice, but a hill is even nicer.

The problem is that the US army is still equipping itself superbly to fight
the Eastern Bloc in 1985.

~~~
gherkin0
> One of the most interesting cold war AFVs was an M113 chassis with a cherry
> picker and 15 TOW missiles on it. Armor is nice, but a hill is even nicer.

Is this what you're talking about? [http://russian-tanks.com/the-m901-armored-
missile-vehicle.ph...](http://russian-tanks.com/the-m901-armored-missile-
vehicle.php)

------
_Codemonkeyism
And Germany - and the world at large - was at the edge of ground-air missles
[1], making cannons on bombers obsolete.

[1]

[https://en.wikipedia.org/wiki/Rheintochter](https://en.wikipedia.org/wiki/Rheintochter)

[https://en.wikipedia.org/wiki/List_of_German_guided_weapons_...](https://en.wikipedia.org/wiki/List_of_German_guided_weapons_of_World_War_II#Surface-
to-air_missiles)

~~~
ZanyProgrammer
The "edge" as in "napkin weapons that would've never have been able to have
been deployed and worked, effectively"

~~~
VLM
It was called flak and was quite effective. The Germans also deployed air to
air missiles that were basically rockets with flak warheads on them. See the
bomber guns had an effective range of 1000 yards or whatever so if you stood
off 1200 yards in your ME-109 and launched rockets that blew up in 1200 yards
that worked pretty well.

I've read a couple memoirs of WWII pilots, interesting stuff. I'm pretty sure
they're all dead now, whats documented out there is all we'll ever have.

As for effectiveness, well, bomber aircraft losses were tremendous until the
end of the war, yet they lost the war anyway. So its hard to say. If you can
down 10% of the B-17 per bombing run against ball bearing factories, but still
lose the war, was it effective or not? Or looking at the staggering economic
and logistics costs of the air war, skipping the air war and focusing on
shipping over tanks that don't suck might have ended the war in '44 or
earlier, so maybe it was ineffective. Imagine if the winter battle of the
bulge never happened because the war was already over by winter rather than
lasting till spring. Or maybe no bombing would have meant more hardware would
have meant the D-day invasion getting pushed back into the sea Dunkirk II
style. Its an evenly balanced enough argument that academics will never lack
for discussion topics.

~~~
mtdewcmu
I have a theory that even though the bombers didn't necessarily always hit
what they were aiming at, the bombing campaign was important in tying up the
Luftwaffe and degrading its capabilities through attrition, thereby hastening
achieving air superiority, which provided a major advantage in the later
ground war. I'm not sure that better tanks would have made as much difference;
and, furthermore, I suspect that the US was able to absorb the costs of the
air war without much difficulty, so it wasn't really siphoning resources away
from things like tanks.

I'm not sure what to make of the Sherman tank. On the one hand, it was
famously under-armored and under-gunned; on the other hand, it was fast,
maneuverable, reliable, fuel efficient, cheap to produce, and perhaps easier
to ship across the ocean than heavier German-style tanks would have been. So,
in the final accounting, I'm not sure if it was really a bad tank or if its
shortcomings were justified in the big picture.

I'm not any kind of WWII expert, so please fill me in on what I don't know.

~~~
douche
The really crazy thing is just how much more massive the scale of the war on
the eastern front was. Some of the Luftwaffe fighter aces racked up 100 or
200+ confirmed kills, primarily against the Soviets. Other pilots who flew
close air support on the Eastern Front flew thousands of combat missions,
destroying hundreds or thousands of tanks, artillery pieces, and other
vehicles.

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rplnt
That "share on pinterest" feature sure is annoying when it blocks text.

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dandare
Can someone please explain how the gunner/computer established the range and
speed of enemy aircraft? The article says "a gunner would focus a series of
dots" but unless at least two gunners are focusing the same plane I have no
idea how they calculated range and speed. Thanks.

~~~
marktangotango
I used to be a gunner on an M1A1, and although we had laser range finders, we
also practiced with the old style optical sights that were installed alongside
the main gun. How range finding works with optical sites is you usually have a
series of marks in the viewfinder that you use to physically measure what
you're aiming at, so if the tank/plane/whatever is between particular two pips
(or whatever; edit iirc the M1 had two curved lines you would placer over the
target) you know that it's about x meters away. The pips are calculated
knowing the average length of the object, so this is, in practice, close
enough.

The procedure is; measure the target, then use cross marks on the cross hairs
to raise the gun tube to the appropriate level, manually guess lead and
defilade, fire, on the way. It obviously takes practice to get good at. I
found it curious that the US Army continued to teach/train/use this method, as
well as land navigation with compass/mapp instead of gps. The idea is to not
rely on technology entirely.

Edit: turns out I am describing stadiametric rangefinding:

[https://en.wikipedia.org/wiki/Stadiametric_rangefinding](https://en.wikipedia.org/wiki/Stadiametric_rangefinding)

~~~
sa46
Regarding teaching land navigation by compass:

I teach light infantry tactics to new lieutenants for the US Army. There's a
couple reasons to use old-school methods over relying on your GPS:

* Using a compass and a map gives you a much better feel for terrain. One of the common problems with lieutenants is a disregard for advantages and disadvantages of specific terrain. I feel that this is by far the most important point. Understanding and visualizing terrain from a map is a hugely valuable skill that impacts most points of an operation, specifically route planning, where to place your machine guns, and where to attack the objective from.

* GPS can be jammed. This point was driven home hard by the novel Ghost Fleet. Ghost Fleet is a white paper turned into a novel (because no one would read a whitepaper) on what a future war with China would look like. I'm pretty sure Ghost Fleet is also the impetus for the Naval Academy re-adding celestial navigation to their classwork.

* GPS doesn't always work, or takes a while to get enough satellites to get a fix. You know what really sucks: taking fire and not knowing where you are.

* Batteries are heavy. Yes, tech is improving and you typically only need AA batteries. But soldier weight for light infantry is and continues to be a challenge.

~~~
Tloewald
In the early aughts I wrote a simulation for training infantry to call in
artillery strikes. It relied on compasses and maps for exactly these reasons.
Another point is that understanding what the automatic tools are doing for you
makes you better at understanding the automatic tools (and why they're failing
when they fail).

------
Mvandenbergh
Some more links on the electromechanical fire computers of the B-29:

[http://www.twinbeech.com/CFCsystem.htm](http://www.twinbeech.com/CFCsystem.htm)
(scroll down for technical information from the user manual)

[http://www.glennsmuseum.com/bombsights/everything.html#B-29_...](http://www.glennsmuseum.com/bombsights/everything.html#B-29_Central_Fire_Control_Computer)
(great pictures)

[http://web.mit.edu/STS.035/www/PDFs/Newell.pdf](http://web.mit.edu/STS.035/www/PDFs/Newell.pdf)
A bonus link, review paper on WWII electromechanical fire control computers.

------
Blackthorn
I was quite surprised to learn recently how the B-29 was (A) about as
expensive a project as the atomic bomb and (B) almost a complete failure
(until the firebombing of Japan) due to no one knowing about the jet stream.

~~~
arethuza
I believe there was also the prospect that if the B-29 hadn't been available
the atomic bombs would have to been dropped from the British Lancaster - which
was the only other bomber capable of carrying them at the time.

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etangent
Out of curiosity (and possibly a dumb question), what is the main constraint
preventing modern (subsonic) bombers from carrying CIWS-type defense system
against missiles? Is it size, weight, recoil, aerodynamics, or special radar
requirements? The initial push behind removing gun systems appears to have
been development of AA missiles and increased reliance on fighter escorts. Yet
modern CIWS on sea vessels have become so effective against missiles that they
significantly upped the cost and requirements of anti-ship warfare, to the
point that a single missile fired at a ship is not expected to be successful.
Given advanced enough CIWS (using directed energy in near future?) one
basically doesn't need stealth or other fancy/expensive/less reliable
features.

~~~
ckozlowski
I'm just guessing here, but I'm going to bet that defensive ECM is probably
deemed better effective per pound that CWIS.

It's worth noting here that CWIS' effectiveness hasn't really been proven. But
what is certain is that it's theoretical effectiveness is being questioned as
missiles get faster. The original 20mm CWIS had a pretty limited range. The
Europeans went to 30mm with Goalkeeper, and now both are set to be replaced
with either directed energy weapons (faster tracking, better accuracy) or
systems like SeaRAM, which can engage further by switching to point defense
missiles instead of guns.

I can see how directed energy weapons could be attractive to aircraft once the
power density issues are solved, but right now they're simply too heavy.

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pippy
How did they do this without transistors? The only thing I can find is this
diagram here which looks like a small box:
[http://www.twinbeech.com/images/TURRETS/cfc/CFC%20computer19...](http://www.twinbeech.com/images/TURRETS/cfc/CFC%20computer197web.JPG)
which is smaller than a vacuum tube. I'd assume you'd need vector calculus to
calculate the path of a bullet?

~~~
monknomo
The first thing to keep in mind is that these are not general purpose
machines. They only do one thing, which is estimate the trajectory of a
particular type of bullet, given several inputs.

This lets the designer do a lot of precalculation, so they might use a series
of cams that approximate known curves or differentials some known ratio.

Useful google terms are things like "mechanical fire control computer" or
"mechanical tide predictor".

Check out "Old Brass Brains" it might give you an idea of how to approach this
kind of problem mechanically; or at least how sophisticated a mechanical
approach can be.

------
Pyxl101
I had no idea that fire control computers in airplanes were so sophisticated
in the 1940s. Truly amazing! I don't know what I thought, but I guess I
assumed that air battles back then relied primarily on line-of-sight and
tracers to compensate.

It's amazing how effective automation can completely transform an activity and
elevate it to a new plane of effectiveness. I'll channel Andreessen and say:
technology is eating the world.

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rangibaby
Linkbait title. They built something complex, but who knows if it was good or
not?

~~~
Kurtz79
"​It was a plane so advanced, we wrote in June 1945 about how one crew fought
off 79 fighter planes, downing 7 of them, during a bombing run on Kyushu,
Japan. Its weapons platform was so dominant that fighter escorts were no
longer strictly necessary—as Major General Curtis LeMay put it simply: "These
big boys can take care of themselves."

~~~
rangibaby
Remember that the war was basically over at that point, and they were fighting
against an enemy starved of resources and experienced manpower, particularly
pilots (cf. kamikaze tactics).

The "79 fighter planes" claim doesn't pass the sniff test to me either.
Remember that two months after this, the Japanese didn't even bother sending
fighters to even try to intercept the planes that bombed Hiroshima (for
example).

I'm not saying that the claim is definitely false, but I wouldn't take
anything written in the press during the actual war at face value.

~~~
hydrogen18
I always figured the Japanese assumed the plane in the case of Hiroshima was a
reconnaissance plane gathered ground photographs and checking on the weather.
As you correctly noted, they didn't have many resources. I'd figure a lone
reconnaissance plane would rank pretty low on the list of targets they were
trying to intercept.

~~~
Raphmedia
Even a lone bomber plane would not have been that much of a threat at this
point. Bomb the weapon factories, the war is over. If they had known what was
coming they would have deployed a lot more and evacuated the civilians.

We all know what happened instead.

