2nd ATOM BOMB

[SPIT]

Hi
According to all the books the First Atom Bomb was fused manualy in the aiccraft whilst it was in flight. My question is Was the SECOND BOMB fused manualy whilst the aircraft was en-route ???:confused::confused:

[hoodie]

Reference 41 (https://en.wikipedia.org/wiki/Fat_Man#cite_note-FOOTNOTERhodes1986740-41) on the Wikipedia page is quoted as saying:


Bockscar lifted off at 03:47 on the morning of 9 August 1945, with Kokura as the primary target and Nagasaki the secondary target. The weapon was already armed, but with the green electrical safety plugs still engaged. Ashworth changed them to red after ten minutes so that Sweeney could climb to 17,000 feet (5,200 m) in order to get above storm clouds.

[KenV]

The Fat Man bomb aboard Bockscar was armed (the spherical "physics package" was installed) at takeoff. The green safety plugs on the bomb's electrical initiators were installed at takeoff and the red arming plugs were installed about 10 minutes after take off.

[Airbubba]

Here's an account of an alleged dramatic problem with the inflight arming accompanied by a Hollywood style blinking red light:

At 7:00 a.m., after about three hours in the air, Ashworth told me that his assistant weaponeer, Lt. Philip M. Barnes, awakened him.

We don’t know to a 100 percent certainty what was said next, but Ashworth recalls the following exchange. What happened does not seem to have appeared in any official histories, but Ashworth swore to me it was true. [Now, this is no s**t... :) - Airbubba]

“Hey, Commander, Ashworth, Dick.” Barnes called him first by rank, then last name, then first name, with increasing terror. “Hey, we got something wrong here. We got a red light going off like the bomb is going to explode right now. Armed, it’s armed. Fully armed, look at this. Can you take a look, what is going on with this?”

A red light that had been blinking steadily suddenly sped up, flashing a dire warming.

Ashworth said he shook himself awake. “Are you sure? Oh my God.” He saw the red light. “There is something … do you have the blueprints? This bomb can pre-detonate if we drop below a predetermined level. What’s our altitude? Where are the blueprints?”

Barnes and Ashworth unrolled the blueprints and started checking. They took the casing off the bomb, and scrutinized the switches. After 10 tense minutes, they saw the problem. Two switches had been reversed, a mistake in the arming process. Barnes flipped the two tiny switches into their proper positions and the red light stopped blinking.

Ashworth went back to sleep. Barnes sat on a small stool in front of the bomb and never took his eyes off the light. When asked why, Barnes later said that as long as it stayed steady, everything was okay with the bomb. If it started to blink rapidly again or if they dropped too low, Fat Man would detonate.

The harrowing story of the Nagasaki bombing mission | Bulletin of the Atomic Scientists (http://thebulletin.org/harrowing-story-nagasaki-bombing-mission8592)

One account of the initial arming in flight:

Thirteen minutes after takeoff, at 4 A.M. Tinian time, the weaponeer made his way aft and removed two green safing plugs from the bomb, replacing them with red arming plugs: it was now live.

What About the Bombing of Nagasaki? - The New Yorker (http://www.newyorker.com/tech/elements/nagasaki-the-last-bomb)

Richard Rhodes, a Yalie historian who writes by the pound ;), describes the inflight arming similarly in The Making of the Atomic Bomb (1986):

Fat Man was fully armed at takeoff except for its green plugs, which Ashworth changed to red only ten minutes into the mission so that Sweeney could cruise above the squalls at 17,000 feet, St. Elmo’s fire glowing on the propellers of his plane.

Rhodes cites Commander Ashworth's log as published by Dr. Norman Ramsey in 1946 as a reference for his account of the red and green plugs.

[MPN11]

The scenario qualifies for a post here >>> "Did you ever have a "moment" when flying?" (http://www.pprune.org/military-aviation/591655-did-you-ever-have-moment-when-flying.html)

[camelspyyder]

Of course, the 2 were completely different weapons. However, Fat Man did have the unique benefit of a previous test firing in New Mexico... I admit, since visiting the test site, I have often wondered why the unproven Little Boy was used first on Ops.

[oggers]

^^^...I think it was because the uranium bomb was inherently much simpler and also there wasn't enough uranium available to test it....

There is a good about the development of the bomb called "Of Men and Atoms" that I read many years ago now.

[wiggy]

As I understand it ( "Ruin from the Air, Enola Gay", Gordon Thomas and Max Morgan-Witts) Little Boy had the detonator and cordite charges for the gun inserted shortly after take-off, the electrical plugs were done later in the flight, shortly before climb to bombing altitude. Because of the significant design differences between the two weapons on Fat Man the only arming in flight that was possible was the aforementioned plugs.

OTOH I have often wondered why the unproven Little Boy was used first on Ops.

I think the very simple reason was Little Boy was ready first.

FWIW it wasn't a tested design simply because as oggers has mentioned there wasn't enough enriched Uranium available to produce a second "round" for quite some time and the Physicists considered it so simple a design - basically and roughly speaking one block off weapons grade uranium fired by a gun into another block - that opinion was it was bound to work if the fusing system produced a firing pulse at the right time..

OTOH if you look at the history of the Fat Man design ( Plutonium Implosion) you'll see it was a nightmare ( both the Physics and engineering) for the scientists to get the implosion of the Pu core to work predictably and satisfactorily (unlike enriched uranium you needed the Plutonium core compressed to get significant fission) so the scientists decided they needed a test of that design, and at by that point in proceedings they also had the luxury of enough weapons grade plutonium coming out of the reactors to mean there was more than enough spare for subsequent Fat Man rounds.

If you really want to get round the history of this I'd second Airbubba's mention of Richard Rhodes's work, especially in this context "The Making of the Atomic Bomb", but also second the comment that Rhodes writes by the pound...and it helps if you have at least a nodding aquaintince with some of the Physics.

[camelspyyder]

Little Boy was ready first?
Fat Man was test fired a month before Hiroshima, AFAIK.

[cornish-stormrider]

IIRC it mentions in Command and Control that the ACTUAL amount of material that fissioned weighed less than a dollar bill before the explosive forces ripped the critical mass apart. Little boy was a very very inefficient method of boom.

the physics is interesting, the reality of it all is scary, and I am bloody glad we have made it this far without any more used thank you..... lets keep it that way please??

[ORAC]

Things to keep you awake at night. From "Making of the Atomic Bomb" by Rhodes.

Fat Man, unit F31 was the second unit assembled. unit F33 with a non-nuclear core was due to be dropped on 5th Aug but was finally dropped on 8th Aug as the test drop crew were delivering Little Boy to Tinian.

Fat Man was due to be dropped on 11th Aug, but bad weather was forecast over the target for 5 days after the 9th so Tibbet persuaded them to bring it forward to the 9th. In order to do a lot of pre-planned checkout procedures were taken out of the assembly process.

On the night of 7th Aug an ensign, Bernard O'Keefe, had the task of doing the final check of the bomb before it was encased in armour and became unreadable. Part of the checkout required connecting the firing unit on the front of the bomb to the with the radar units in the tail with a cable which wound around the implosion sphere. When he went to do so he found two male connectors at one end and two female at the other - the cable had been installed the wrong way round, and reversing it would mean dismantling the bomb taking days.

So, without telling anyone, he called a technician, ran 2 extension leads from adjacent lab, and unsoldered, reversed and resoldered the plugs on the lead; ran some continuity checks - then tidied everything up, finished connecting everything up and finished sealing the bomb. He didn't tell anyone till after the war......

[ORAC]

Description of the full mission - a FUBAR from start to finish......

The harrowing story of the Nagasaki bombing mission | Bulletin of the Atomic Scientists (http://thebulletin.org/harrowing-story-nagasaki-bombing-mission8592)

"....Unlike the Enola Gay that had bombed Hiroshima, Bockscar was not greeted on its return with fanfare and praise. The military did not push the Bockscar story or decorate the men who flew the mission—unlike what happened with the Enola Gay’s crew. There was talk that Sweeney should be court-martialed for disobeying orders, but nothing came of it. We had won the war. There was no point in making the military look bad........"

[wiggy]

Camelspyyder

Little Boy was ready first?
Fat Man was test fired a month before Hiroshima, AFAIK.


Yes, as you say, Trinity was a test of the Fat Man design (to prove the implosion method really worked). The completed but simpler Little Boy wasn't "lab" tested, for reasons already mentioned, so I'm not sure you can make any readiness comparison simply based on Trinity.

That Trinity test didn't mean Fat Mans started rolling off a production line, far from it. They'd used one device and the build rate for subsequent weapons was dependant on the rate of supply of Plutonium, then, once the weapons were almost complete they were shipped to the field (Tinian in the 509ths case) in pieces to be finally assembled on site by a small group of engineers (as ORAC described). OTOH because Little Boy was a one off, ""just do it", it's components started being shipped to the Pacific before the Fat Man was even tested - according to some sources the USS Indianapolis left San Francisco for Tinian carrying major Little Boy components the very same morning as the Trinity test.

As a result history shows the single available Little Boy was cleared for use, assembled and available for the 509th on Tinian to use several days before the first Fat Man war round...so regardless of tests, it is difficult to draw any other conclusion other than the single Little Boy was the first nuclear weapon ready for use in theatre.

[West Coast]

Good find ORAC, interesting reading.

[goudie]

The second mission by the Bockscar crew is one of the most compelling stories I've ever read. Its got everything, technical problems rendovue problems, near misses critical fuel states, hairy landing to name a few.If anyone deserved a medal they certainly did

[Airbubba]

Of course, the 2 were completely different weapons. However, Fat Man did have the unique benefit of a previous test firing in New Mexico... I admit, since visiting the test site, I have often wondered why the unproven Little Boy was used first on Ops.

I've never been to the Trinity Site but my wife's sister has. At Los Alamos there is the nice little free Bradbury Science Museum. The Gadget, its components and pertinent historical correspondence are featured prominently in the Historical Gallery. I don't remember seeing much about Little Boy, maybe that device is covered in better detail in the Smithsonian or USAF Museum exhibits.

I've read the first couple of books in Richard Rhodes' nuclear tetralogy more than once over the years. I'm trying to plow through Arsenals of Folly but I feel like I've been stuck on a communist collective farm with the Gorbachev's for the last hundred pages. ;)

[Evalu8ter]

Airbubba,
I'm with you in Rhodes' gulag...I loved the first two but just can't get on with Arsenals. Command and Control however, is a very readable book and contains much new information to digest - and, at times, horrify. The investment in Plutonium refinement for the aborted "Thin Man" gun-type weapon (issues with reactor bred Pu and spontaneous fission IIRC) led to the sudden focus on implosion, which would not work with Uranium. A simple gun-type bomb would fission with enough Uranium, but would be horribly inefficient in terms of the amount of material that would fission before the bomb blew itself apart. Given the amount of refined U235 available, and the Physics that suggested it would work, LB was developed, assembled and dropped. As suspected, it was woefully inefficient - if 15Kt can be described as such. LB type weapons were also resurrected briefly post war after issues with Pu reactors.......

[Bergerie1]

Evalu8ter,
What is the title of the book you mention on 'Command and Control'? And is it also by Richard Rhodes?

[Molemot]

If you want to see how WE did it, allow me to recommend this book....
https://www.amazon.co.uk/d/Books/Test-Greatness-Britains-Struggle-Atomic/0719552257

"Test of Greatness" details the British struggle for independant nuclear weapons. It is, by turns, fascinating, horrifying and very funny. You can get it on Kindle for nothing, these days.....

[KenV]

Little Boy was ready first?
Fat Man was test fired a month before Hiroshima, AFAIK. Yes, and when that test was being readied, Little Boy was already on its way to Tinian. So a gun-type war round was on its way to the theater while an implosion type test round was being readied.

[Tocsin]

Bergerie1 - it's not by Richard Rhodes, but Eric Schlosser:

https://www.amazon.co.uk/Command-Control-Eric-Schlosser-ebook/dp/B00CDBZ6NA/ref=sr_1_1?s=books&ie=UTF8&qid=1489414570&sr=1-1&keywords=command+and+control

ISTR it's a bit episodic, but still a lot of intersting info.

[ColinB]

It appears Deke Parsons armed it on the ground and the weaponeer, Fred Ashworth, pulled the safety plugs at 4 am
I wrote a review of books of this era which may be helpful In The period covering the genesis and production of the first atomic bombs is well served by literature. The initial British efforts are elegantly described in three books by Margaret Gowing, the official description of the US efforts were covered by Hewlett and Anderson in The New World and this was updated by Richard Rhodes' magisterial The Making of The Atomic Bomb which rightly won the Pulitzer Prize.
In The Manhattan Project Stephen Groueff covered the industrial problems in a most accessible book and I found Stalin and the Bomb by David Holloway most rewarding.

The later US developments were covered by U.S. Nuclear Weapons: The Secret History by Chuck Hansen

[Bergerie1]

Thanks Tocsin

[Airbubba]

Command and Control however, is a very readable book and contains much new information to digest - and, at times, horrify.

I agree, it is a worthy successor to Schlosser's Fast Food Nation and Reefer Madness. ;)

I've actually never read the other titles but Command and Control is well done and I also would recommend it. :ok:

[5645andym]

As I understand it the Uranium bomb design had been tested beforehand but it was not necessary to actually explode a device in order to do so.
The bomb achieved critical mass by firing a cylindrical “bullet” of uranium down a converted gun barrel into a circular uranium target – by slowly sliding the bullet down the barrel and measuring the increase in the flow of neutrons as it approached the target.
They were able to go to something over 99% of critical mass and measure precisely how and when the bomb would explode without actually setting the bomb off so they could be sure that it would work when dropped operationally.
With the Plutonium design there were technical reasons why the “gun” method could not be used and an implosion design was the only viable alternative - that could not be tested other than by detonating a live weapon.