High Altitude Heavy Bomber for RAF

[EwenS]

.....A commencement date for Tiger Force wasn't until early 1946,

The Tiger Force "Special Missions Wing" consisting of the Tallboy equipped 9 & 617 squadrons were expected to be established on Okinawa in time to participate in Operation Olympic scheduled for 1 Nov 1945. The first of two convoys carrying Airfield Construction Service units and their equipment left Britain in mid-July 1945 to travel to Okinawa via the Panama Canal and Pearl Harbor. The first contingent on SS Empress of Australia had reached Eniwetok by mid-Aug where they were held temporarily due to the war ending. They were then diverted to Hong Kong via the BPF base at Manus. Arriving HK in early Sept, they helped re-establish services for the civilian population in the colony.

 

[GrauGeist]

So circling back to the question of an early high altitude bomber:

What could.have been done to get the Stirling to meet that profile?

I know I've asked before, but it was missed in the conversation.

The 100 foot wingspan is one issue that could have been addressed.

What else could have been done to improve it's performance?

 

[don4331]

So circling back to the question of an early high altitude bomber:

What could.have been done to get the Stirling to meet that profile?

I know I've asked before, but it was missed in the conversation.

The 100 foot wingspan is one issue that could have been addressed.

What else could have been done to improve it's performance?

I looked at this last night after your question:

Going from Wiki as I don't have anything better, it says the Stirling has the Sunderland's wing reduced/thickened to the 100' requirement... Checking Aeroweanie 's site, he has both using a modified Gottingen 436 airfoil...which is an 11% airfoil which doesn't impress me as a thick airfoil. (OK, max ordinance for top and bottom curves don't line up, but the max values for each still only add up to a 11.5 airfoil...) Can Short double the thickness and still call it a Gottengen 436 airfoil??

The Stirling is also heavy in comparison to the Lancaster - 49,600lbs empty compared to 36,900lbs. Even the Lincoln at 44,200lbs is lighter - which will affect load carrying, speed and ceiling.

The biggest drawback I see is the Hercules XI is a single stage single speed engine. The Bristol engines must have contributed heavily to the Stirling's low ceiling (16,500') compared to the Lancaster's (21,400'). The Hercules XVI with 2 speed drive probably would have went a long way to address this. But it's still way behind the Lancaster VI with 2 stage 2 speed Merlins (28,500' ceiling)<or 30,500' depending on source> Can Bristol cobble together a 2nd stage and air to air intercoolers to get the required altitude in "reasonable" timeframe? Can the Hercules be adequately cooled at the required altitude??

If you're sticking with 4 engines, the alternative is 4 - RR Griffons to get 2 stage 2 or 3 speeds. (I'm not considering the Centaurus or Sabre as they doesn't really have a high altitude versions either).

Without GE licensing (selling) its turbine technology to UK, turbocharging is a long steep hill to climb...​

 

[wuzak]

The Stirling has a larger wing area than the Lancaster, with roughly the same wing span.

Gottingen 436 airfoil looks to me to be an earlier style aerofoil than the Lancaster's NACA 23018 at root and 23012 at tip.

Maybe a bit draggier.

The fuselage is longer and deeper - a product of a troop carrying requirement?

So I don't think the Stirling is as aeroydynamic as the Lancaster.

Rolls-Royce had experimented with a turbo Condor in the 1920s, so it was not unknown to them.

Power Jets was designing and building their first gas turbines, and Metropolitan Vickers the F.1 then F.2 gas turbine engines.

Both these used axial type turbines, similar to what GE was doing.

And, arguably, British compressor technology, or at least Rolls-Royce's, was in advance of GE's.

If some sort of turbo was required, I'm sure it could be developed and tested before production versions of the high altitude/heavy bomber were ready.

(The Rolls-Royce Crecy used a scaled down Derwent turbine for turbo-compounding - such a turbine could have been the basis for a turbocharger.)

 

[wuzak]

Would an all-metal design be preferred to Wallis's geodetic design for the Victory bomber?

Vickers were producing the Wellington using the geodetic design, and would produce a few Windsors using the same technology, they were also able to build the Type 432 high altitude fighter using stressed skin metal construction.

For reference, Windsor design started in 1941, first flight 1943. Type 432 started in 1939, first flight 1942.

An all new design starting in 1940 may have been available in late 1944?

 

[EwenS]

The fuselage is longer and deeper - a product of a troop carrying requirement?

There was also a troop carrying requirement in Spec P.13/36 that led to the Manchester and the Halifax. IIRC it was 1940 before it was finally dropped from the requirements.

 

[Alan Stevens]

The Thin Man bomb—an early gun-type nuclear weapon design—ran into a fatal flaw: plutonium-240.

Here's the breakdown:
Design concept: Thin Man was a long, rifle-like bomb intended to fire one subcritical mass of plutonium into another to achieve a nuclear explosion. It relied on plutonium-239 as the fissile material.

The problem: Reactor-bred plutonium inevitably contains plutonium-240, an isotope with a high rate of spontaneous fission. That means it emits neutrons randomly and frequently.

Why that matters: In a gun-type bomb, the two plutonium masses take milliseconds to come together. But with too much plutonium-240, there's a high risk that a stray neutron could trigger a premature chain reaction—a "fizzle"—before full assembly. That would result in a dud or a vastly reduced yield.

Outcome: By mid-1944, Los Alamos scientists realized the gun-type design was unworkable with plutonium. They scrapped Thin Man and shifted focus to the implosion-type design, which became the Fat Man bomb dropped on Nagasaki.

So in short, Thin Man was doomed by the very nature of reactor-produced plutonium.

 

[Alan Stevens]

The B-29 is still the benchmark. The aircraft has to be pressurised if you want the altitude performance, and then there is the range and payload, which should be able to match the B-29 on the atom bomb missions. It is a big ask, but realistically, there's no choice, otherwise the RAF acquires Washingtons, which defeats the purpose of a new big bomber. Let's face it, you are not really going to want to achieve the altitude performance without a pressurised airframe, so that means the Lancaster airframe is out.

The aircraft in the on-deck circle for the B-29 was the B-32.

The Consolidated B-32 Dominator was developed as a backup to the B-29 Superfortress in case Boeing's ambitious design ran into insurmountable problems.

The B-32 shared many features with the B-29, including the same powerful Wright R-3350 engines and a pressurized cabin in its early design. But it suffered from development delays, mechanical issues, and design compromises—like abandoning pressurization and remote-controlled turrets due to persistent problems.

By the time the B-32 was combat-ready in mid-1945, the B-29 was already flying missions over Japan. Only 118 B-32s were built, and they saw limited action in the Pacific, including a few bombing runs and even the last air combat of World War II.

So yes, the B-32 was in the on-deck circle—but the B-29 hit the home run.

the B-32 would have been a super-heavy replacement for the B-24 and the B-17 if the war lasted into 1946

 

[Shortround6]

Going back to the original post and premise

To carry the bomb, Wallis has proposed the 6 engine "Victory" bomber.

in 1940 the proposed bombers were a lacking in engine development which lead to the 6 engine solution with had problems of it's own.
The B-29 worked (barely) because the turbos allowed a sea level 2200hp to make 2200hp at over 25,000 or more importantly to make 2000hp at over 25,000ft at max continuous.
Granted they sucked fuel at a horrendous rate but trying to get non turbo engines to give similar power was not going to work (unknown in 1940/41).
A B-29 at a take-off weight of 120,000lbs could burn 1000 US gallons of fuel just getting to 30,000ft and needed just under 240 miles to do it using max continuous power all the way.
They may not have done that very often, more likely to climb in stages to cool off the engines.
The late/post war 3 speed Griffon offered 2000-2420hp at low altitude but it was down to about 1400hp at 25,000ft for max continuous.
Needing 6 or more 2000lb + engines (and radiators and other accessories) to match the power if the Wright engine installations (with all of their accessories, like twin turbos and intercoolers) started running the weights up quick.

Using manned defensive guns didn't work well with pressurization. Getting remote control/sighting guns made sealing the crew compartment a lot easier but required more complicated gun mounts. A limited travel tail mount might work.

A large, heavy, high speed bomb is going to be less effected by winds on the way down but dropping from higher altitudes has problems of it's own, like vision.
There is often quite a difference even with rifles between theoretical accuracy and practical accuracy at longer ranges.
Granted part of the idea of an earthquake bomb is that you only have to get it into a area of 4-6 city blocks
But in 1941-42 for the British you do need to find the right city.

 

[GrauGeist]

I looked at this last night after your question:

Going from Wiki as I don't have anything better, it says the Stirling has the Sunderland's wing reduced/thickened to the 100' requirement... Checking Aeroweanie 's site, he has both using a modified Gottingen 436 airfoil...which is an 11% airfoil which doesn't impress me as a thick airfoil. (OK, max ordinance for top and bottom curves don't line up, but the max values for each still only add up to a 11.5 airfoil...) Can Short double the thickness and still call it a Gottengen 436 airfoil??

The Stirling is also heavy in comparison to the Lancaster - 49,600lbs empty compared to 36,900lbs. Even the Lincoln at 44,200lbs is lighter - which will affect load carrying, speed and ceiling.

The biggest drawback I see is the Hercules XI is a single stage single speed engine. The Bristol engines must have contributed heavily to the Stirling's low ceiling (16,500') compared to the Lancaster's (21,400'). The Hercules XVI with 2 speed drive probably would have went a long way to address this. But it's still way behind the Lancaster VI with 2 stage 2 speed Merlins (28,500' ceiling)<or 30,500' depending on source> Can Bristol cobble together a 2nd stage and air to air intercoolers to get the required altitude in "reasonable" timeframe? Can the Hercules be adequately cooled at the required altitude??

If you're sticking with 4 engines, the alternative is 4 - RR Griffons to get 2 stage 2 or 3 speeds. (I'm not considering the Centaurus or Sabre as they doesn't really have a high altitude versions either).

Without GE licensing (selling) its turbine technology to UK, turbocharging is a long steep hill to climb...​

The Short. Brothers were hunting in the right direction, though.

The Sunderland's wing was 112 feet, but their S.32 project was intended to have a wingspan of 117 feet (with a wing area of 2,020 sq.ft.).

It seems to me, that the Stirling's greatest weakness, were it's engines.

The aircraft in the on-deck circle for the B-29 was the B-32.

There was also the XB-39.

 

[Alan Stevens]

There was also the XB-39.

XB-39 was an upgraded B-29

 

[GrauGeist]

XB-39 was an upgraded B-29

The XB-39 was a backup plan for the B-29 in the event that the R-3350 engine issues were not resolved.

The XB-39 was literally a re-engined B-29, having Allison V-3420 engines installed in place of the Duplex Cyclones.

It's performance was impressive, too.

 

[wuzak]

The XB-39 was a backup plan for the B-29 in the event that the R-3350 engine issues were not resolved.

The XB-39 was literally a re-engined B-29, having Allison V-3420 engines installed in place of the Duplex Cyclones.

It's performance was impressive, too.

Faster, but shorter ranged.

 

[Shortround6]

If you put in more powerful engines but don't increase the fuel load you get shorter range.

A lot of these bombers had operational ceilings thousands of feet lower than their 'service ceiling'. A lot depended on weight and some times the "book' weight was way under what they actually operated at. Some B-29s were taking off 13-15,000lbs heavier (overload) than gross weight. They were not burning off all the extra fuel just taking off and getting to cruise altitude.
Same goes for the British 4 engine bombes just not quite as extreme.

Another factor is when did they discover they needed a pressurized crew compartment at around 30,000ft? They developed the pressure cabin in the Wellingtons with a goal of 40,000ft.
The B-17 was supposed to operate above 30,000ft but................they couldn't. The Plane would, with some difficulties, but the crews could not. Oxygen masks and heated suits worked for a few hours, not 5-8 hours at the high 20s and low 30s. They needed pressure cabins, just not quite as much as flying at 40,000ft but you have to know that at the design stage or early development stage, and you have to be OK with dropping the big bomb at a lower altitude and having a lower impact speed (less penetration) or.................you need the heavier pressure cabin and the fancier engine installations to not just reach 40,000ft but actually operate at 40,000ft.

 

[Alan Stevens]

Another factor is when did they discover they needed a pressurized crew compartment at around 30,000ft? They developed the pressure cabin in the Wellingtons with a goal of 40,000ft.
The B-17 was supposed to operate above 30,000ft but................they couldn't. The Plane would, with some difficulties, but the crews could not. Oxygen masks and heated suits worked for a few hours, not 5-8 hours at the high 20s and low 30s. They needed pressure cabins, just not quite as much as flying at 40,000ft but you have to know that at the design stage or early development stage, and you have to be OK with dropping the big bomb at a lower altitude and having a lower impact speed (less penetration) or.................you need the heavier pressure cabin and the fancier engine installations to not just reach 40,000ft but actually operate at 40,000ft.

To do it right -- need all crew spaces pressurized, not just the flight crew space. On the B-29 that included the mid section and the tail section.

That's one of the features that made the B-29 Superfortress so advanced for its time. Unlike earlier bombers, the B-29 had three pressurized compartments: the forward crew cabin, the mid-section (connected by a 35-foot pressurized crawl tunnel over the bomb bays), and the tail gunner's compartment.

This setup allowed the entire crew—not just the pilots—to operate in a pressurized environment at high altitudes, which was crucial for long-range missions over the Pacific. The tail gunner's station was especially unique: it was pressurized but isolated, meaning the gunner couldn't leave it during flight unless the aircraft was depressurized. It was a bold leap in bomber design—and a logistical challenge.

It relied on bleed air from the turbo-superchargers on the inboard engines (#2 and #3) to supply pressurized air to the crew compartments.
Here's how it worked : The turbo-superchargers compressed ambient air to boost engine performance at high altitudes. A portion of that compressed, filtered air was tapped off and routed into the aircraft's pressurized sections. This air was cooled and regulated before entering the forward, mid, and tail compartments to maintain a livable pressure and temperature.

Using engine exhaust itself would've introduced toxic gases and heat—so instead, the system cleverly used the clean, compressed intake air from the turbochargers. It was one of the first operational systems of its kind and a major leap in bomber crew survivability.

 

[yulzari]

One Lancaster high altitude proposal, equally applicable to the other heavies, was to mount a fifth engine in the fuselage to drive a supercharger whose high pressure air would be piped to the wing mounted engines. Of course this is extra fuel and mass but maintains low level power at height.

 

[SaparotRob]

Wouldn't that cut into a bunch o' bomb bay?

 

[Alan Stevens]

One Lancaster high altitude proposal, equally applicable to the other heavies, was to mount a fifth engine in the fuselage to drive a supercharger whose high pressure air would be piped to the wing mounted engines. Of course this is extra fuel and mass but maintains low level power at height.

The added weight of a non-propulsive engine, plus the necessary ducting, intercoolers, and fuel load, would have eaten into payload, range, and overall efficiency. And all that complexity meant more maintenance headaches and more things to go wrong at 40,000 feet. In many ways, it was an elegant solution to a tough problem—but also one that created new trade-offs.

 

[yulzari]

The added weight of a non-propulsive engine, plus the necessary ducting, intercoolers, and fuel load, would have eaten into payload, range, and overall efficiency. And all that complexity meant more maintenance headaches and more things to go wrong at 40,000 feet. In many ways, it was an elegant solution to a tough problem—but also one that created new trade-offs.

Quite so but it was something that could be incorporated into existing production. Obviously not seamlessly but still within a timescale far faster than a new design. How well the crew would cope with flying at an even higher altitude is another matter. The high altitude Wellington had a pressurised capsule for the crew.

Mapperley History

 

[Alan Stevens]

Quite so but it was something that could be incorporated into existing production. Obviously not seamlessly but still within a timescale far faster than a new design. How well the crew would cope with flying at an even higher altitude is another matter. The high altitude Wellington had a pressurised capsule for the crew.

Mapperley History

Seems very over complicated to me. The Merlin was one of the most advanced engines of the war. Just equip the propulsion plants with turbochargers like was done in the R-3350 and there will be enough airflow into all crew compartments.

I don't see the need for 40,000 foot altitude design.

The B-29 Superfortress was designed for high-altitude strategic bombing and had a service ceiling of about 31,850 feet.