The Lancaster as a potential nuclear bomber in 1945

[FLYBOYJ]

From Wiki:

Silverplate operational units[edit]
Including the Pullman B-29, a total of 46 Silverplate B-29s were produced during World War II. Of these, 29 were assigned to the 509th Composite Group during World War II, with 15 used to carry out the atomic bombings of Hiroshima and Nagasaki. An additional 19 Silverplate B-29s were ordered in July 1945, which were delivered between the end of the war, and the end of 1947. By this time only 13 of the original 46 were still operational. Thus, a total of 65 Silverplate B-29s were made, of which 32 were operational at the start of 1948.[27] Martin-Omaha produced 57 Silverplate B-29s. The other 8 were built by Boeing-Wichita. Of these 65 bombers, 31 were eventually converted to other configurations, 16 were placed in storage and later scrapped, and 12 were lost in accidents (including four of the Tinian bombers). The pair of historic weapons delivery aircraft, named Enola Gay and Bockscar, are today displayed in museums.[28][29][30]

The only other United States Air Force combat unit to use the Silverplate B-29 was the 97th Bombardment Wing at Biggs Air Force Base in El Paso, Texas. In mid-1949 it received 27 of the aircraft from the 509th Bombardment Wing when the latter transitioned to B-50D bombers.[31] The re-equipment of the 97th Bombardment Wing was part of an expansion of the atomic strike force to ten wings during 1949.[32] Within a year all were converted to TB-29 trainers. One other Silverplate B-29, on temporary assignment in the United Kingdom, was converted into a weather reconnaissance aircraft (WB-29) and transferred to the 9th Bombardment Wing at Travis Air Force Base in California.[31] The last Silverplate B-29 in service as a nuclear weapons carrier was reassigned to another role in November 1951, ending Silverplate after nearly eight years.[33]

 

[nuuumannn]

Yup, have read that page on the Silverplate B-29s on Wiki. Interesting stuff.

 

[wuzak]

If we know for certain that Little Boy was actually considered for carriage by Lancasters, that will give us a bit better idea as to what might have been a legitimate target. Little Boy was bigger than Thin Man, which would have had an impact on the Lancaster's range etc; that we know from the figures provided here already, so what did those guys who considered the Lancaster have in mind for its use?

Little Boy was smaller, in both diameter and length, than Thin Man.

Little Boy: 28" diameter 10ft long
Thin Man: 38" diameter 17ft long

Little Boy would fit in a Mosquito's bulged bomb bay, if a British style round tail unit had been used instead of the US style box tail.

 

[wuzak]

Silverplate - Wikipedia

The Silverplate project was initiated in June 1943 when Dr. Norman F. Ramsey from the Los Alamos Laboratory's E-7 Group identified the Boeing B-29 Superfortress as the only airplane in the United States inventory capable of carrying either type of the proposed weapons shapes: the tubular shape of the Thin Man, or the oval shape of the Fat Man.[1]

Prior to the decision to use the B-29, serious consideration was given to using the British Avro Lancaster with its cavernous 33-foot (10 m) bomb bay to deliver the weapon. It would have required much less modification, but would have required additional crew training for the USAAF crews. Major General Leslie R. Groves Jr., the director of the Manhattan Project, and General Henry H. Arnold, the Chief of United States Army Air Forces (USAAF), wished to use an American plane, if this was at all possible.[2]

The first B-29 was delivered to the USAAF on 1 July 1943,[3] and Groves met with Arnold later that month. Groves briefed Arnold on the Manhattan Project, and asked for his help in testing the ballistics of the Project's proposed bomb shapes. Arnold and the head of the Ordnance Division at Los Alamos, Captain William S. Parsons, arranged for tests to be carried out at the Naval Proving Ground in Dahlgren, Virginia, in August 1943. No aircraft was available that could carry the 17-foot (5.2 m) long Thin Man, so a 9-foot (2.7 m) scale model was used. The results were disappointing – the bomb fell in a flat spin – but the need for a thorough test program was demonstrated.[3][4]

Groves met with Arnold again in September 1943. He informed Arnold that there was now a second bomb shape under consideration, the Fat Man, and formally requested that further tests be carried out, that not more than three B-29s be modified to carry the weapons, and that the USAAF form and train a special unit to deliver the bombs. Arnold delegated responsibility for this to Major General Oliver P. Echols. In turn, Echols designated Colonel Roscoe C. Wilson as the Project Officer.[5]

Silverplate - Wikipedia

The USAAF sent instructions to its Army Air Forces Materiel Command at Wright Field, Ohio, on 30 November 1943, for a highly classified B-29 modification project.[1] The Manhattan Project would deliver full-sized mockups of the weapons shapes to Wright Field by mid-December, where Army Air Forces Materiel Command would modify an aircraft and deliver it for use in bomb flight testing at Muroc Army Air Field in California. B-29-5-BW 42-6259 (referred to as the "Pullman airplane" from an internal code name assigned it by the Engineering Division of Army Air Forces Materiel Command) was delivered to the 468th Bombardment Group at Smoky Hill AAB, Kansas, on 30 November 1943, and flown to Wright Field on 2 December.[8]

Modifications to the bomb bays of 42-6259 were extensive and time-consuming. Its four 12-foot (3.7 m) bomb bay doors and the fuselage section between the bays were removed and a single 33-foot (10 m) bomb bay configured. The length of the initial gun-type bomb shape was approximately 17 feet (5.2 m), necessitating that it be carried in the aft bomb bay, with some of its length protruding into the forward bay. The implosion-type bomb was mounted in the forward bay.[8] New bomb suspensions and bracing were attached for both shape types, and separate twin-release mechanisms were mounted in each bay, using modified glider tow-cable attach-and-release mechanisms.[9

Similar to what has been posted by others.

So, to summarise, the Lancaster was initially considered to carry the A-bomb because of the size and shape of Thin Man.
Thin Man failed and led to the development of Little Boy.
Only one Silverplate B-29 was configured to carry Thin Man, because it was cancelled in early 1944.

 

[nuuumannn]

So, to summarise, the Lancaster was initially considered to carry the A-bomb because of the size and shape of Thin Man.

Primarily because it could be carried internally, by the looks of things from Ramsay's report. The B-29 was always going to be the nuclear bomber though, Gen Groves and Hap Arnold wanted an American aircraft, so it was always a long shot that it be actually converted (I'm curious to find out what the text Joe linked to that states that the Lanc was 'seriously considered' refers to and to what extent).

 

[GrauGeist]

Grant, here's an overview of the Silverplate project on the Atomic Heritage Foundation's website.

Project Silverplate

It briefly covers the prospect of the Avro being used

 

[nuuumannn]

Thanks Dave, that's what Joe posted back a bit. I'm keen to find out what 'seriously considered' actually means. From the passages in the book that I posted it looks like the Lancaster was only listed by Ramsay because other than the B-29, it was the only bomber that might be able to carry a Thin Man internally, with less modification than the B-29.

 

[railroader]

On the B-29 the bomb bay was accessible in flight. The Hiroshima Little Boy was in fact armed, that is the detonation charges installed, while in flight. Would this have been possible to do in a Lancaster?

 

[GrauGeist]

On the B-29 the bomb bay was accessible in flight. The Hiroshima Little Boy was in fact armed, that is the detonation charges installed, while in flight. Would this have been possible to do in a Lancaster?

There was a bomb bay access door at the Engineer's station, so it would have been possible.

 

[Greyman]

I think that 'access' was just for visual checks. I think to actually fiddle with a bomb some further modification would be required (Grand Slam pictured).

 

[GrauGeist]

I think that 'access' was just for visual checks. I think to actually fiddle with a bomb some further modification would be required (Grand Slam pictured).


View attachment 528584

Agreed...the Lancaster's bomb bay was noting like American designs, so access would have been possible, but I don't think practical.

 

[CorsairLarry]

Dave, the Lanc doesn't have the range to fly from Tinian. Okinawa would be the only realistic option. RAF Tiger Force was looking at Okinawa as a base for ops with Lincolns and Lancs, but the A bombs were dropped before this plan got underway.

Tiger Force (air) - Wikipedia

The other problem with using the Lanc and indeed the Lincoln as nuclear bombers is the fact they could only carry the Little Boy. Fat Man was, well, too fat. This severely limits the flexibility of the mission. Fat Man ws ordered into production, Little Boy was initially unique, although after the war production on a limited scale was undertaken, but not to the same numbers as Fat Man. Also, timewise, the Lincoln entered service in August 1945 with 57 Sqn receiving 3 of them (!), so that rules it out of the equation if the original timeline of this is to be honoured.

It's possible that had the B-29 program suffered some calamity, the the US would have turned to it's slightly less advanced stablemate the B-32

 

[Kevin J]

It's possible that had the B-29 program suffered some calamity, the the US would have turned to it's slightly less advanced stablemate the B-32

Lets be frank here. To drop an atomic bomb on Tokyo, Japan, you only need a limited production run of a pressurised bomber that has to fly outward from Tinian 1500 miles and back to Iwo Jima another 750 miles to refuel, take off again and return to Tinian. That's 2250 miles on the first leg, 3000 overall but not the 3000 there and back that the Superforts did. The only other pressurised high altitude bomber is the Vickers Windsor which had a range of 2890 miles carrying 8000 lbs of bombs when powered by Merlin 65's. As I see it, the Windsor is the only viable alternative. You only need a limited production run, so no problem.

 

[special ed]

The B-32 most likely would not have been structurally able to make the demanding turn and dive to get away from the shock wave. Another commander came to Tinian to try to take over the 509th and fly the mission. Tibbets, who had been practicing since Wendover invited him on one of the dummy missions over Japan to show him what he would need to do with the B-29 after bomb drop. The book said the wanna be turned white at the wing over and once back at base disappeared.

 

[special ed]

In addition, the man who armed the bomb had to get into very close proximity to the front of the weapon. He was incidentally a Naval Lt. Commander who came over with the device on the Indianapolis, if my memory serves.

 

[GrauGeist]

Just a thought, but the USAAF did have a prospective alternate if the B-29 wasn't available.

The Douglas B-19A had the ability to lift a max. load over 37,000 pounds with a max. ceiling of 39,000 feet. It's top speed was 265mph and had a range of 4,200 miles (with a load of 18,000 pounds).

In 1944/45, it was literally sitting out the war on a ramp.

 

[nuuumannn]

The B-32 most likely would not have been structurally able to make the demanding turn and dive

The Lancaster could make the turn and dive, as bomber crews practised such a manoeuvre as defence against night fighters. That's no suggestion it was anyway more suited for this than what we already know, though.

The Douglas B-19A had the ability to lift a max. load over 37,000 pounds with a max. ceiling of 39,000 feet. It's top speed was 265mph and had a range of 4,200 miles (with a load of 18,000 pounds).

Gee, that's some performance. How big was the bomb bay?

 

[GrauGeist]

Gee, that's some performance. How big was the bomb bay?

Not sure of the actual dimensions of the bomb bay, but the B-19 was huge.
Wingspan was 212 feet (64.6m), length was over 132 feet (40.0m) and height was almost 43 feet (13m) and the tires on it's main gear were 8 feet tall.

Here's a shot of the command deck (looking back from the co-pilot's seat. Center is the engineer's station.

Here's a shot of it at Douglas, note the man standing in front of the starboard main gear...

 

[wuzak]

The performance quote was the XB-19A with the V-3420 engines.

The XB-19, shown in that last picture, had lower performance.

 

[wuzak]

Gee, that's some performance. How big was the bomb bay?

Not that big.

Check out some pictures from the Aviation Pictures forum.

Douglas XB-19

In terms of performance, it had a slightly lower top speed than the Lancaster, but was about 100mph slower than the B-29.

With the same engines as the XB-19A, the XB-39 had a top speed of ~400mph.