High Altitude Heavy Bomber for RAF

A few things.

The Rex didn't have any AA guns
The B-17s didn't have any bombs
These B-17s were in the first 12 and didn't have turbos (no flying at high altitudes )

It was a proof on concept stunt.
It was May 1938.
The USAAF was in budget battles with the Navy and was trying to recover from some bad tests/publicity from the 1931 test of bombing of the USS Mount Shasta which took two tries 3 days apart, the bombers could not find the target although news photographer planes did on the the first try. The second try scored a few hits with 300lb and 600lb bombs but failed to the sink the hulk (freighter). Extent of damage is not listed by Wiki and the hulk was sunk by small caliber cannon (3/4in?) on a pair of Coast Guard tugboats. Unknown if the Shasta was slowly sinking or not without actual report and there may have been bias anyway.

The B-17 vs Rex stunt showed that it was possible to intercept a ship 600-650 miles away from land in poor weather conditions.
But that was all it showed.

You needed a lot more testing to figure out if you could actually hit (not theories)
And you need testing to figure out what size/type of bombs to use. (not theories)

Yes the Rex was steaming on the known course at pretty much a known speed but they were using a noon position report from the 11th (the expected night time position report was not received) for the interception just after noon on the 12th. Weather often force flight altitudes to under 1100ft and there were rain squalls.

There was a lot of theory around in the 1930s in a lot of air forces and navies. There was not a lot practical experience or even testing under controlled conditions. A number of exercises were done under biased conditions.
The AAF intercepted the Rex because the Navy failed to provide any ships at all for the 1938 war game that was supposed to simulate an attack on both coasts at the same time.
How was anybody supposed to evaluate an attack against a totally non-existent enemy fleet?
Both sides could claim whatever they wanted. The Army proved they could at least find a ship over 600 miles away.
This backfired with the Aug 1938 cancelation of orders for 67 B-17s and the cancelation of any research into long range bombers. They ordered smaller airplanes instead.
This was reversed/changed in Jan 1939.

Even better with B-24s.

I realize that my previous post has very little to do with the RAF high altitude bombers but many nations were NOT spending large sums of money on R&D in the 1930s and a lot of bombers were being designed on theory. Not just theory of aerodynamics and structures and propulsion but theories of actual bomb damage and theories of needed tonnage of bombs to damage certain targets or cause the 1930s theorist's favorite conclusion, panic in the streets by the public forcing the opposing government to surrender.
In Britain's case for most of the 1930s, this would be achieved by lots and lots of 250-500lb bombs.
Development and testing of the 1000GP bomb seems to have been put on hold from Aug 1932 until some time in 1938. It was not until June 1939 that orders were placed for experimental forged bomb bodies, but manufacturing capacity for forged bombes was hard to find and in Dec 1939 orders were placed for 2000 forged bombs and 9000 cast bombs.
Only 159 bombs were delivered in 1940. 11,662 were delivered in 1941.
The 1900lb GP was slower, there were no 1920s-1932 experiences or drawings in existence to draw on and the Jan 1939 requirement was not fulfilled until 1941 (504 bombs) and the 1900lb was not a good bomb, only 26% explosive by weight. Now some this was due to the original specification which called for a max diameter of 19in which tends to show the problems with some of the British bomb bays. Yes they can hold 18in torpedoes or even several of them. But they can't stack bombs vertically and they can't hold large HE bombs (2000lb +) internally.
The aircraft designers gave the Air Ministry what they asked for.
Now any high altitude bomber that was designed before the summer of 1939 has to deal with some of these bomb size restrictions or we are talking about a bomber that first sees pencil on paper in late 1939/early 1940 and that is going to be be very difficult to bring to service use in WW II.
Boeing submitted the model 345 design to the USAAC 11 May 1940. They had been working on the basic design for a number of months before that.

Alan Stevens said:

The 509th's 15 B-29s had Silverplate modifications and these are the only B-29s that should be charged to the Manhattan Project. The aircraft cost about $650,000 apiece.

While the 509th had more than 17 Silverplate aircraft assigned by the end of the war, only about 15 were operationally deployed to Tinian in time for the atomic missions.

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That grossly understates the number of "Silverplate" B-29s built. There were 65 in all.

A prototype B-29-5-BW converted between Dec 1943 & Feb 1944 to drop the "Thin Man" device whose development was stopped. It was damaged in Dec 1944 and then stored. This had a single enlarged bomb bay and was referred to as "The Pullman Aircraft".

There were then two batches from the B-29-5-MO to B-29-30-MO blocks totalling 17 aircraft. These were used by trials units and provided the initial 14 "Silverplate" B-29 equipment of the 393rd BS 509th CG. Deliveries of these aircraft modified to "Silverplate" standards began in Oct 1944.

By Spring 1945, B-29s were being produced with new features like reversible propellers, quick acting bomb doors etc. Rather than modify existing aircraft with the 393rd, a new batch of 28 "Silverplates" was built with earlier aircraft going to trials units or storage. Deliveries of 15 of these to the 393rd BS began in April 1945. It was these aircraft that they took to Tinian when they began to deploy in early June 1945.

A final batch of 19 was ordered in July 1945 with deliveries running through until 1947.

By the end of WW2 about 46 "Silverplates" had been completed to service the Manhatten Project with at least 29 serving with the 393rd BS at one time or another. Without all the testing that went on, there wouldn't have been a reliable A-bomb. So at the very least the cost of these 46 aircraft, if not all 65, is attributable to the Manhattan Project.

Frog said:

Even better with B-24s.

View attachment 836112

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Or the 1942 Augsburg Raid

EwenS said:

That grossly understates the number of "Silverplate" B-29s built. There were 65 in all.

A prototype B-29-5-BW converted between Dec 1943 & Feb 1944 to drop the "Thin Man" device whose development was stopped. It was damaged in Dec 1944 and then stored. This had a single enlarged bomb bay and was referred to as "The Pullman Aircraft".

There were then two batches from the B-29-5-MO to B-29-30-MO blocks totalling 17 aircraft. These were used by trials units and provided the initial 14 "Silverplate" B-29 equipment of the 393rd BS 509th CG. Deliveries of these aircraft modified to "Silverplate" standards began in Oct 1944.

By Spring 1945, B-29s were being produced with new features like reversible propellers, quick acting bomb doors etc. Rather than modify existing aircraft with the 393rd, a new batch of 28 "Silverplates" was built with earlier aircraft going to trials units or storage. Deliveries of 15 of these to the 393rd BS began in April 1945. It was these aircraft that they took to Tinian when they began to deploy in early June 1945.

A final batch of 19 was ordered in July 1945 with deliveries running through until 1947.

By the end of WW2 about 46 "Silverplates" had been completed to service the Manhatten Project with at least 29 serving with the 393rd BS at one time or another. Without all the testing that went on, there wouldn't have been a reliable A-bomb. So at the very least the cost of these 46 aircraft, if not all 65, is attributable to the Manhattan Project.

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Three of the first seventeen went to the 216th AAF Base Unit at Wendover and were used for tests. The forteen other went to the 393rd Bomb Squadron.

Alan Stevens said:

The 509th's 15 B-29s had Silverplate modifications and these are the only B-29s that should be charged to the Manhattan Project. The aircraft cost about $650,000 apiece.

While the 509th had more than 17 Silverplate aircraft assigned by the end of the war, only about 15 were operationally deployed to Tinian in time for the atomic missions.

Click to expand...

17 Silverplates were ordered in August of '44 for training followed by 28 more in early '45 for operational use.

Their unit cost as $814,000 each.

Alan Stevens said:

Flying a B-17 bombing mission at 200 feet AGL? Sounds rather reckless to me.

50cal and 20mm AA could get many hits on them and they could CFIT if they were not very careful.

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In the late 1930s, the "bomber boys" regularly executed flamboyant highly publicized and sometimes risky missions in the effort to promote heavy bombardment investment and their state of the art B-17 wonder-weapon. (see the Rex Interception in my avatar) Locating the fleet and dropping water balloons and flour sacks on the decks of maneuvering battleships made for good press. BUT, nobody was shooting back and none of the world's navies had adequate AA defenses in 1938. Just four years later it was a completely different situation and would be suicide without effective AA suppression.

In a partial response to Shortround6's post above, there's a good write-up available on Wiki:

GrauGeist said:

17 Silverplates were ordered in August of '44 for training followed by 28 more in early '45 for operational use.

Their unit cost as $814,000 each.

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But like I said, only about 15 were operationally deployed to Tinian in time for the atomic missions.
Unit cost quotes vary depending on the source.

But even 45 * $814 thousand = $36.63 million.
1.8% of the $2 billion given for the Manhattan Project.

Alan Stevens said:

But like I said, only about 15 were operationally deployed to Tinian in time for the atomic missions.
Unit cost quotes vary depending on the source.

But even 45 * $814 thousand = $36.63 million.
1.8% of the $2 billion given for the Manhattan Project.

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That's okay. The B-29 in whole demolished much more urban area than simply the two A-bombs and delivered an airplane that could drop the bomb from the Marianas. Well worth the three billion dollars.

I look at this sort of thing as a weapons-system thing. A 1300mph fighter is not very useful without guided missiles, a giant gun is not very useful without a tank or GMC to tote it around usefully on a field of combat. American subs were damned near useless until the MK14 debacle got sorted out. M-26 Pershings were slow to get to Europe in part because they took up a lot of space on cargo ships and LSTs. Systems.

B-29+Manhattan project was terribly expensive, but we had the money and it worked -- as a system. In that light, I don't mind putting MP and B-29 into the same expense pile. You needed one to feature the other.

One thing the Western Allies did very well (after a bit of sorting) is to develop systems to deliver firepower at the necessary point. Compare that to the chaos of Axis systems, in production, logistics, weapons, and delivery.

Alan Stevens said:

But like I said, only about 15 were operationally deployed to Tinian in time for the atomic missions.
Unit cost quotes vary depending on the source.

But even 45 * $814 thousand = $36.63 million.
1.8% of the $2 billion given for the Manhattan Project.

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Silverplate was alotted 53 million by the Manhattan commission. This amount has been used in later years to inflate the B-29's overall cost.

29 Silverplate B-29s were assigned to the 509th CG and on station, 15 were used operationally with the remaining being active reserve.

GrauGeist said:

Silverplate was alotted 53 million by the Manhattan commission. This amount has been used in later years to inflate the B-29's overall cost.

29 Silverplate B-29s were assigned to the 509th CG and on station, 15 were used operationally with the remaining being active reserve.

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The -29 was enormously expensive as a delivery system for both standard and nuclear bombs. Considering the context of the time and the ability of our nation to cover the cost, not to to mention the follow-on effects on airplane design and construction, it seems to me to be a fair investment. Forcing Boeing to leap ahead with this made sure, I think, that the B-47 and B-52 rolled out as they did.

Thumpalumpacus said:

That's okay. The B-29 in whole demolished much more urban area than simply the two A-bombs and delivered an airplane that could drop the bomb from the Marianas. Well worth the three billion dollars.

I look at this sort of thing as a weapons-system thing. A 1300mph fighter is not very useful without guided missiles, a giant gun is not very useful without a tank or GMC to tote it around usefully on a field of combat. American subs were damned near useless until the MK14 debacle got sorted out. M-26 Pershings were slow to get to Europe in part because they took up a lot of space on cargo ships and LSTs. Systems.

B-29+Manhattan project was terribly expensive, but we had the money and it worked -- as a system. In that light, I don't mind putting MP and B-29 into the same expense pile. You needed one to feature the other.

One thing the Western Allies did very well (after a bit of sorting) is to develop systems to deliver firepower at the necessary point. Compare that to the chaos of Axis systems, in production, logistics, weapons, and delivery.

Click to expand...

It was first considered to used Lancaster bombers that had proven their capacity to carry huge bombs with the Tallboy, but the Silverplate B-29s were selected for national prestige reasons.

To use business terms, ROA=Return on Assets, the B-29 was the go bomber for years. Including the Korean affair and development into the B-50. The ROA continued as 29 use in a mother plane role in tests of missiles and X planes. Finally as targets, a life sort of like the B-52 of today. The KB-29K and P used jet engines to increase speed to refuel TAC fighters. Consider the ROA in the KC-97 tankers and the 377 airliners. ROA continues with the Guppies and Super Guppies. We got our moneys worth, and so did the USSR.

Frog said:

It was first considered to used Lancaster bombers that had proven their capacity to carry huge bombs with the Tallboy, but the Silverplate B-29s were selected for national prestige reasons.

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The Lancaster was only briefly considered.

Yes, there was the fact that high command wanted an American bomber, but the B-29's performance also made it a prime candidate as it flew faster, further and higher - this last feature is important, as the first bomb was released over Hiroshima at 31,000 feet and the second bomb was released over Nagasaki at 29,000 feet, both of which being well above the Lanc's service ceiling.

The possibility of a Lancaster as an Atom Bomb delivery platform was discussed in great detail here:
The Lancaster as a potential nuclear bomber in 1945

Frog said:

It was first considered to used Lancaster bombers that had proven their capacity to carry huge bombs with the Tallboy, but the Silverplate B-29s were selected for national prestige reasons.

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"First"? "Considered"? I think both those are questionable statements. From what I understand, the Lanc was suggested by a Brit scientist, but was not "considered", which suggests debate and discussion before rejection.

There's an entire thread on the topic bouncing around here somewhere.

Thumpalumpacus said:

"First"? "Considered"? I think both those are questionable statements. From what I understand, the Lanc was suggested by a Brit scientist, but was not "considered", which suggests debate and discussion before rejection.

There's an entire thread on the topic bouncing around here somewhere.

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According to the Manhattan Project site, the Ordnance Division of group E-7 (Delivery Group), under Ramsey at first concluded that only the Lancaster and then troublesome B-29 (1943) were able to deliver a 10 tons bomb. The Lanc was quickly dropped because of a too narrow bomb bay and the opposition of Arnold.

Trying to steer the thread back to an RAF bomber:

If Avro starts with the Manchester and instead of just adding 12' (90' -> 102') for Lancaster, adds 38' for the high altitude bomber along with Lancaster VI extended outer wings, the resulting bomber has more/less the wingspan required (146' wingspan). The additional 26' allowing 2 additional engines with Ø 13' propellers.
Given the increased span outer, Avro needs to extend the fuselage <engines further out + high altitude requirements> (Lancaster VI/Lincoln I was 9' extension i.e. 50% of span increase), so 19' extension. 70' -> 89'
This gets an airframe more/less capable. Not as efficient as a clean sheet, but available sooner?

RR can then be given the requirement for the engines - we don't care how: 6 -Merlins with 2 stage/3 speeds or 4 - Griffons/ 4- Vultures with 2 stage/2 speeds (And you can start with less, e.g. Tallboy vs Grand Slam and/or 25k' versus 30'k using 2 stage/2 speed Merlins).

A lot of the other issues are chicken or egg and/or wanting all weather bombing (Wallis was thinking only 25% of days would allow attacks)
Can e.g. Mossie's adequately guide to/mark the target so the main bomber force doesn't need as sophisticated tools?

The Short Stirling was ahead of Avro in terms of development.

Had Short not been restricted in wing width and several other issues, than the Stirling may have been a much better performer and available to perform missions that the Lancaster later performed.

Frog said:

According to the Manhattan Project site, the Ordnance Division of group E-7 (Delivery Group), under Ramsey at first concluded that only the Lancaster and then troublesome B-29 (1943) were able to deliver a 10 tons bomb. The Lanc was quickly dropped because of a too narrow bomb bay and the opposition of Arnold.

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I'm unable to find that, can you link?