Terminal velocity of Little Boy, and Enola Gay's speed, August 6, 1945.

[GythaOgg]

@Machine_Elf

They were off by 1.9 miles, which is considerably greater than the quarter mile I indicated. Moreover, it’s not clear from the Wikipedia article whether they were aiming for their original planned target, or the nearest thing they could see with the given cloud cover.

From what I have read (and I own an extensive book collection on the subject of the bombings and the US atomic program), they were looking for any visual sighting they could get at Nagasaki, no matter what it was. They were low on fuel, did not want to land or crash with the bomb on board, and Major Sweeney had already decided to drop the thing on Nagasaki by radar if he had to, which was in direct contradiction to the strict orders he’d been given to do a visual drop only. So the Nagasaki bomb was dropped basically over a suburb instead of the city center. And even at that, the crew barely made it home.

The original aiming point at Hiroshima was the Aioi Bridge near the center of the city. The bomb there ended up only roughly 200 meters away, over the Shima Hospital…pretty accurate actually.

[mlees]

@treis

It’s not like it was a precision weapon. Would missing the target by a mile really make much of a difference?

It may have made a difference at Bikini. (Operation Crossroads, Test Able) link

@wiki

However, the main cause of less-than-expected ship carnage was that the bomb missed its aim point by 710 yards (649 m).[44] The ship the bomb was aimed at failed to sink. The miss resulted in a government investigation of the flight crew of the B-29 bomber. Eventually, it was agreed that a flaw in the bomb’s tail stabilizer had caused the miss, and the flight crew was cleared of responsibility.

That’s half a mile because of the tail assembly. The difference being that the ship below survived (or not) based on how close, and what orientation they had, to the blast.

[CurtC]

@Fubaya

The turn made after dropping the bombs was actually a 155 degree turn. Due to the turning radius of the B-29, they could turn 155 degrees and step on the gas and get farther away than if they had turned 180 degrees.

Thanks - that makes sense.

If they turned instantly and headed the other way at 200mph, they would be 9 miles from ground zero 45 seconds later. Of course, my numbers aren’t exact, the turn took time and they certainly accelerated too, but there’s how you get your 9 miles separation from the bomb.

According to my quick calculations, at 300 mph, a 155 degree turn at 2g would take 21.5 s. Seems like to me a 2g turn in a B29 would qualify as “hard” (that’s a 60-degree bank holding altitude).

So anyway, at the end of that turn, they’d be at the same distance from ground zero as when they started the turn, then they’d have the other 23.5 seconds to increase their distance.

If the bomb was moving horizontally at 270 mph on average, then in 45 seconds it went 3.4 miles (like Machine Elf said). The B29, travelling 300 mph for 23.5 seconds, would travel just under 2 miles, so that’s 5.4 miles of horizontal distance. Combine that with the 30,000 feet of vertical distance, and the distance between the plane and the bomb at detonation would be 7.8 miles.

[TroutMan]

@CurtC

…
If the bomb was moving horizontally at 270 mph on average, then in 45 seconds it went 3.4 miles (like Machine Elf said). The B29, travelling 300 mph for 23.5 seconds, would travel just under 2 miles, so that’s 5.4 miles of horizontal distance. Combine that with the 30,000 feet of vertical distance, and the distance between the plane and the bomb at detonation would be 7.8 miles.

If we really want to make this complicated, it isn’t entirely accurate to sum the distances the bomb and plane travel. After a 155 degree turn, the plane isn’t moving in the exact opposite direction.

Plus add wind speed to the plane’s distance, assuming the plane retreated with the wind (a fair assumption, given the planning that went into the drop). I’d think 100 mph or more is a reasonable wind speed at that elevation?

[CurtC]

@TroutMan

If we really want to make this complicated, it isn’t entirely accurate to sum the distances the bomb and plane travel. After a 155 degree turn, the plane isn’t moving in the exact opposite direction.

Yes, it should be, that was the point of making a 155-degree turn. If you draw this out on a sheet of paper, it makes sense - after a turn of less than 180 degrees the plane would then be heading straight away from ground zero, because of the radius of the turn.

Plus add wind speed to the plane’s distance, assuming the plane retreated with the wind (a fair assumption, given the planning that went into the drop). I’d think 100 mph or more is a reasonable wind speed at that elevation?

Yeah, then again, if the wind speed is constant at all altitudes, that would completely cancel out (all the calculations would be in a reference frame that moves with the wind). If the wind speed varies with altitude (which it certainly does), then you’d want to release the bomb on an upwind trajectory, but I think it partially cancels out anyway.

[GusNSpot]

After reading this thread I see that ignorance is not being fought very well because folks are still coming late and saying they could not do it or the math was wrong or something.

They dropped it.
It went off.
They lived.

Not much to argue about.

Could the pilot be wrong about a number from how many years ago while giving a talk?

Wiki is a hard cite that can stop all questions? Since when?

For every driving a car story you like to tell you are always 100% accurate about the speeds of each?

I have seen several planes do things that the designers & engineers said they could not do. Do not forget the human element and the ‘some’ that have talent way in excess of what the slide ruler class think is possible.

Carry on …

[Fubaya]

@CurtC

Yes, it should be, that was the point of making a 155-degree turn. If you draw this out on a sheet of paper, it makes sense - after a turn of less than 180 degrees the plane would then be heading straight away from ground zero, because of the radius of the turn.

Illustration here. There should be a cool name for this aerial maneuver, like zero doppler turns and lag rolls, but if “Gay turn” hasn’t caught on after 67 years, I guess it never will.

[Kevbo]

In later years some more advanced drop protocols were developed…though of course never used with live weapons. By pulling upward prior to release, the bomb can be lobbed upward, and the reduced airspeed allows the airplane to turn at a faster angular rate for a given G-loading, and then dive away from the blast. (this is routinely exploited by pylon racers) This was mainly envisioned as a low-altitude “under the radar” tactic, and parachutes for the bombs were also developed to allow additional escape time.

Aside for those with morbid fascination of this and similar topics: The National Atomic Museum is located in Albuquerque, NM; just outside Sandia National Lab. It is worth a visit if you are in, or passing through town, but I wouldn’t make a special trip. They have actual casings from the Fat Man and Little Boy devices (made as spares) on display, as well as a lot of cold war memorabilia. If you should visit, I work a few blocks away (not at the lab) and am usually available for lunch, or at least can recommend local eateries and watering holes depending on what you are hungry or thirsty for.

[Zebra]

They almost used a parachute type bomb on Japan. The incredible true story of using bats to set Japanese cities on fire.

[ralph124c]

When the Russians dropped the 100 Megaton “Tsar Bomba” over Novaya Zemylya, the bomber barely escaped.
Are there any accounts (by the pilots) of what the experience was like?
The Hirosma andNagasaki bombs were pretty small in comparison.

[Malacandra]

@ralph124c

When the Russians dropped the 100 Megaton “Tsar Bomba” over Novaya Zemylya, the bomber barely escaped.
Are there any accounts (by the pilots) of what the experience was like?
The Hirosma andNagasaki bombs were pretty small in comparison.

That they were - as Little Boy was to a Grand Slam (Brit 10-ton HE bomb) so was the Tsar to Little Boy, roughly. Incidentally, Tsar Bomba was scaled back to a beggarly 57 megatons for the test drop for exactly the reason above

[Tonytryke]

possible for the Enola Gay and much more!!!

I know this post is a few months late,but I just found this thread and thought I might add a few thoughts from an actual witness of the Enola Gay’s test flight!!!

First,some backgroud info.My late uncle was a Warbird mechanic in the European and Burma theaters in WW2.Towards the end of the war,he ferried planes from Dallas Tex to the Arizona graveyard.He hated the P39 but loved the P51,P38 and his favorite Warbird was the P47 Jug.“It was a damn tank that could take unbelieveable battle damage and still fly and it flew like a scalded dog”.

What I’m telling you now was Top Secret in 1945 but now,almost 70yrs later?? It’s old news

The only similarity between the Enola Gay and it’s twin,Bockscar that bombed Nagasaki and a “normal"B29” was that they looked the same!!!

Any specs you see anywhere relating to Enola Gay’s speed are those of a “normal” B29.Enola Gay was not a normal B-29! Enola Gay was taken off the assembly line and totally stripped of any armor and ordnance.It was essentially a flying,empty shell!

Each one of those huge R2800 radials was painstakingly blueprinted and were probably closer to 3000 hp each vs 2000 for a stock B-29!

Towards the end of the war,my uncle went to Omaha,Neb where he set up a P47 Jug for an important flight.That important flight was the test flight of Enola Gay and that Jug was the chase plane that shadowed Enola Gay when she flew.He actually saw the test flight.

Top speed for the B29 was as said,about 365mph.My uncle said the Jug would do about 435mph topped out at 30,000 ft.To the best of my knowledge,no top speeds were ever released relating to the test flight but my uncle knew what he saw and heard!

He estimated the planes were at about 20-25,000ft where the Jug would have been capable of around 420mph or so.This was an experienced warbird mechanic that knew what a Jug sounded like at full throttle.“The Jug was on the Gay’s tail and I could hear it was full throttle”.

“Then the pilot opened up the Gay’s throttles and left the Jug like it was standing still.If the Jug was doing 420,the Gay was doing well over450,probably the fastest damn prop plane of the war”!!!

There you have it!!!