Watching the atom bombs go off from ships

A question was raised elsewhere about Allied sailors watching the atom bombs going off from their ships off the coast of Japan.
Did any of them watch the explosions & report on them ?
Any photos of the explosions taken on board ship?

 

I never have either.

If there were any seaborne observations, they would be Japanese.

 

Interesting to find out how far the cloud could be seen...curvature of the earth etc etc...

 

If the Earth were an airless world like the Moon, the above calculations would be accurate. However, Earth has an atmosphere of air, whose density and refractive index vary considerably depending on the temperature and pressure. This makes the air refract light to varying extents, affecting the appearance of the horizon. Usually, the density of the air just above the surface of the Earth is greater than its density at greater altitudes. This makes its refractive index greater near the surface than higher, which causes light that is travelling roughly horizontally to be refracted downward. This makes the actual distance to the horizon greater than the distance calculated with geometrical formulas. With standard atmospheric conditions, the difference is about 8%. This changes the factor of 3.57, in the metric formulas used above, to about 3.86. This correction can be, and often is, applied as a fairly good approximation when conditions are close to standard. When conditions are unusual, this approximation fails. Refraction is strongly affected by temperature gradients, which can vary considerably from day to day, especially over water. In extreme cases, usually in springtime, when warm air overlies cold water, refraction can allow light to follow the Earth's surface for hundreds of kilometres. Opposite conditions occur, for example, in deserts, where the surface is very hot, so hot, low-density air is below cooler air. This causes light to be refracted upward, causing mirage effects that make the concept of the horizon somewhat meaningless.

 

Sooooo....how far could the cloud be seen?

 

Don't make the poor man do math. Using the voodoo (and 8% correction factor) presented by the gentleman from Norfolk Island:

Hiroshima: Assuming 17km height of mushroom cloud: visible from ~500km away.

Nagasaki: Assuming 16km height of mushroom cloud: visible from ~490km away.

Disclaimer: Of course, these are approximate and many not be even close to what the reality was on the mornings of the bombings.

 

Thanks for the replies chaps.
The person who raised the question that piqued my interest hasn't been back to where they asked it but I'm enjoying this thread.
I'm learning a bit from it too.

 

Well, for both the Hiroshima and Nagasaki drops, the 3d Fleet was no where nearby. The last strike day prior to that 6 August was 30 July. On 6 August the fleet was performing underway replenishment while heading north to planned 9 August strikes.

Quoting a narrative of the final TF-38 operations, penned by one CDR C E A Owen, RN, liaison to TF-38 staff here in my hot little hands, I’ll start on 30 July and end on 10 August:

"47. On the following day, TF 38 from a position 70 miles to the South East of Shikoku struck the Tokio area but unfortunately that part of Japan was all but weathered out. Strikes were shifted to the MAIZURU area which had not been attacked previously and on the whole despite the weather the results of the day were moderately successful. A total of 1200 offensive sorties were flown which dropped 400 tons of bombs and fired 3500 rockets. The MAIZURU Area was highly profitable and besides hitting the ex-Italian liner “Conte Verde” with 3-500 lb bombs 2 transports and a small oiler were sunk and a light cruiser, 3 freighter transports damaged. Altogether 20 vessels of 6000 tons were sunk and 56 ships of 73000 tons damaged. Because of the weather many bombs were dropped on targets of opportunity and industry railways and transport received heavy damage. A total of 258 aircraft were put out of action, 115 being destroyed and 142 damaged all on the ground. The Task Force which in the forenoon was only 35 miles from the island of IMAMBANSHIMA was not attacked. Our losses for the day were 11 aircraft and 8 pilots. The task force retired to the Southward that evening but remained within covering distance of a destroyer sweep which had been sent in to sweep Suguru Wan. No shipping was found but again Japan was bombarded. One destroyer on the screen complained of having been straffed during the night by a friendly fighter which on investigation turned out to be Japanese.

48. For a variety of reasons, including typhoons atomic bombs and finally fog, Task Force 38 did not strike again until 9th August. This interval was spent replenishing and carrying out limited flying and gunnery exercises in a position approximately 24o45' N and 137o30' E. The typhoon which passed close to Okinawa and West of Kyushu, was successfully avoided but it caused a postponement of the intended strike on Northern Kyushu and Korea of the 4th August. This plan was finally cancelled because the flying restrictions in the area caused by the atomic bomb operation. A plan to strike the Tokio area from the Southeast before the Task Force returned to Eniwetok also changed at the last moment by a CinCPac directive to strike Hokkaido and Northern Honshu on the 8th August, presumably because of the expected Russian entry into the war.

49. On 5th August TF 37 and TF 38 left their area and proceeded to the Northward fueling from their respective oilers on the 6th and 7th August. Their run to the flying off position for the 8th August was commenced on the previous day. The middle watch was enlivened by a plethora of bogies which emanated from King George V’s radars. So persistent and in such quantities were they, that Commander Third Fleet was forced to move a cruiser squadron and a destroyer flotilla to deal with this mirage.

50. As had been expected fog was prevalent over the whole area and flying operations could not take place. CTF 38 had suggested a second flying off position more to the Southward as a alternative if the weather reports the previous evening indicated possibility of fog but unfortunately if had been turned down. As it was, TF 38 was caught with no aircraft airborne and 3 enemy aircraft over head which fortunately did not make contact. Finally at 0915 the Task Force turned to the Southward and shortly after it was possible to fly off a limited CAP, which shot down 2 enemy aircraft overhead during the course of the afternoon, however our position appeared to remain unknown to the enemy.

51. The flying off position for the strikes on the 9th August was 120 miles to the East of KINKASAN, and was clear from fog but airfields n Northern Kyushu were again found to be mainly fogbound. The Task Force flew 5 to 6 strikes alternating between fighter bomber sweeps of 12 aircraft and escorted strikes of 15 bombers and 16 fighters from each CV, thus insuring against fog closing down unexpectedly by avoiding having large numbers of aircraft in the air which a normal flight program with 2 big strikes would have entailed.

52. For the first time during the course of these operations the Japs made a slight attempt at hitting back. The usual bogey activity developed t about 1215 which was being dealt with very effectively by the fighter defense as none penetrated very much nearer than 40 miles, but at 1315 2 groups of 3 planes each were not intercepted by 2 divisions of fighters controlled by the Southern Tomcat & in the subsequent attack on them the destroyer Borie was hit in the after side of the bridge and suffered 50 casualties, 20 of whom were killed or missing. Although her forward steering position was out of action, she remained on station and that evening was escorted to Task Group 30.8.

In the afternoon a wily Jap nearly succeeded in hitting Wasp by following one of our returning formations, he was seen just in time and shot down by fighters 400 yards astern.

53. TF 38 had a profitable day dropping 580 tons of bombs and firing 2250 rockets. A convoy consisting of 2 DD 3 DE and 1 merchant ship was annihilated by the combined efforts of aircraft from TF 37 and TG 38.3. 303 aircraft were put out of action which included 7 shot down n the air, 3 by Tomcats gunfire, 189 were destroyed on the ground and 102 damaged. Airfields, especially those at MATSUSHIMA and KORIYAMA suffered severely. With many aircraft unable to reach their assigned airfields because of the prevailing fog, they wandered around their areas causing havoc to transportation and shipping. Amongst the latter 15 ships were sunk and 54 damaged. Our losses for the day were 7 aircraft in combat and 14 operational 5 pilot and 2 aircrewmen being lost.

54. A second bombardment of the steel works at KAMAISHI took place at 1300 by 3 battleships of the South Dakota class, cruisers and destroyers, this group was supported by King George V, the Newfoundland, and Gambia. No photographs of the target have been available since but reports indicated that it had been very successful.

55. On the 10th August strikes were resumed in the same area again from a position about 120 miles off shore. TF 37 which had been moved to the southern end of the Task Group disposition, found difficulty in covering her allotted area because of the range of her aircraft, but CTF 38, presumably because of possible enemy reaction would not move nearer to the coast."


R

 

And, just to make the distance clear, 24o45' N and 137o30' E is about 670 miles ESE of Hiroshima.

 

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There was this issue, for what it's worth.