The Lancaster as a potential nuclear bomber in 1945

[buffnut453]

Not to put too fine a point on it but what was Chadwick going to say? No, our bomber can't handle it? Of course he's going to say yes. His comment doesn't really mean anything in the scheme of the discussion other than an interesting aside.

Sorry but I strongly disagree with that statement. Chadwick wasn't a sales guy, nor was he a former project manager with a business degree but no technical chops. He was an engineer...and a bloody good one.

One thing I've learned in my dealings with engineers is that they seldom say they can do something if they haven't worked out the practicality to some level of detail. Bear in mind Chadwick had already integrated a number of unplanned-for bomb loads onto the Lancaster, including Upkeep, Tallboy and Grand Slam.

For my money, if Chadwick said it could be done, then you could take that to the bank.

Now, was the Lancaster a better option than the B-29? Of course not. The latter was a generation ahead in technology.

Could the Lancaster have carried out the nuclear mission? That rather depends on the extent of changes made to the airframe. The mods for the 3 British weapons mentioned involved considerable airframe changes but all were implemented relatively quickly and successfully.

We will never know what changes would have to be made to the Lancaster airframe but many of the key elements were there (eg saddle tanks for extra range). The key challenge would be bringing together all those elements while attaining a suitable altitude to drop the weapons, and achieving sufficient getaway speed to protect the crew. Those may be intractable problems but desperation is the mother of invention. If the B-29 had flopped, I have no doubt that the Lancaster's problems would have been resolved sufficiently to carry out a nuclear mission. Maybe not the exact profile that was actually flown by Tibbets and Co., but a workable profile was probably achievable.

 

[RCAFson]

Here's a top (plan) view of a Lancaster bomb-bay with an 8000lb HC bomb. This bomb is slightly longer than a Fat Man (which has a max width just less than the B-B), but has a similar CG. I've drawn in 2 aux fuel tanks, fore and aft of the bomb. These two tanks would have a total capacity of 900-1200IG:

for reference here's a look at other Lancaster bomb loads:

Bomb Loads

Note how the CG of the Tall Boy and Grand Slam prevent the use of aux tanks aft of the bomb, but on the Catechism Tirpitz raid a 400IG Wellington aux tank was fitted forward of the TallBoy.

 

[nuuumannn]

While I agree that people not actually involved in the project wouldn't be given specific details, the idea that "a foreign national" wouldn't be allowed access to the programme is absolutely not correct. The British were heavily involved in the Manhattan Project, indeed Roosevelt was suggesting the US actively engage with Britain on nuclear weapons as early as October 1941...and a whole bunch of the "British" participants had very non-British names. I know it's Wikipedia but take a look at British contribution to the Manhattan Project - Wikipedia for more details.

Yes, as I have pointed out, there were even New Zealanders involved, but the point was that Chadwick WAS NOT involved, therefore he would not be privvy to secret information. Ramsey would have supplied him what he could, not necessarily specifics, so Chadwick would have to make an educated guess based on what he knew. The presumption that he received specific details such as engineering drawings, dimensions and such like is hearsay and can only be proven if we know for certain exactly what he received. It is highly unlikely he would have been aware of the code names Thin Man and Fat Man as in 1943 these were used within the Manhattan Project alone.

For my money, if Chadwick said it could be done, then you could take that to the bank.

Again, see above. Unless we know exactly what Ramsey sent him, what these details were, then any stipulation that it could definitely carry a Fat Man is merely speculation until proven otherwise, NOT guaranteed fact. And, as I have pointed out repeatedly before, the drag aspect to carrying such a bomb would be enormous and it would be barely flyable, with the engines working hard to overcome the extra drag - see the definition of drag coefficient, which would eat away at its fuel quantities. It's just not a practicable proposition. Just a heads up, I studied aerodynamics when doing my engineering training, so I do know a little about this sort of thing, but it doesn't take a qualified engineer to see that carrying such a bulbous load underneath it would severely impact its performance.

The Grand Slam carrying B.I Specials were dogs to fly and even in the Lancaster I and III's handling notes, at MTOW the aircraft can only be flown straight and level until its weight is below 63,000lbs. Oil temps in the climb were at their highest levels before the engines overheated and the climb had to be skillfully managed, the engines themselves reached extreme temperatures and handling was severely degraded. Not the best condition to be in on a long haul bombing operation of such importance.

 

[buffnut453]

Yes, as I have pointed out, there were even New Zealanders involved, but the point was that Chadwick WAS NOT involved, therefore he would not be privvy to secret information. Ramsey would have supplied him what he could, not necessarily specifics, so Chadwick would have to make an educated guess based on what he knew. The presumption that he received specific details such as engineering drawings, dimensions and such like is hearsay and can only be proven if we know for certain exactly what he received. It is highly unlikely he would have been aware of the code names Thin Man and Fat Man as in 1943 these were used within the Manhattan Project alone.

Again, see above. Unless we know exactly what Ramsey sent him, what these details were, then any stipulation that it could definitely carry a Fat Man is merely speculation until proven otherwise, NOT guaranteed fact. And, as I have pointed out repeatedly before, the drag aspect to carrying such a bomb would be enormous and it would be barely flyable, with the engines working hard to overcome the extra drag - see the definition of drag coefficient, which would eat away at its fuel quantities. It's just not a practicable proposition. Just a heads up, I studied aerodynamics when doing my engineering training, so I do know a little about this sort of thing, but it doesn't take a qualified engineer to see that carrying such a bulbous load underneath it would severely impact its performance.

Again, if Chadwick said the Lancaster could carry the weapons, then it's a reasonable assumption that he had access to sufficient information to enable him to say definitively that it was feasible. That's not "speculation" but confirmation from the Lancaster's designer. As an engineer, I find it extremely unlikely that Chadwick would say the Lancaster could do something if he lacked critical information upon which to base such an assertion.

As to the drag question, again it rather depends on the changes made to the Lancaster to perform the mission. The Lancaster's overall drag could be considerably reduced by removing the H2S blister and mid-upper turret, and replacing the front turret and perhaps the bomb aimer window with a more streamlined design. Such changes would introduce some trade space from a performance perspective.

Again, I'm not saying the Lancaster would be a good option as a nuclear bomber, and certainly not as good as the B-29. As Joe has pointed out, we're dealing in "couldda/wouldda/shouldda" hypotheticals but I have a hard time believing Chadwick would say the Lanc could do something without having done the calculations first to ensure his claims were correct. If you can point to any other instance where Chadwick performed in such a cavalier attitude, I'd be happy to be educated.

 

[Conslaw]

I was thinking about Sweeney's mission and led me to wonder.

Suppose Bockscar was one of these unicorn Lancasters - would it have been able to follow the exact timeline of eventsbas the actual B-29 or would it have been lost in action?

I've seen a great deal of effort to try and "fit" a Pumpkin Bomb into it's bomb bay, so let's assume the fuselage was widened enough to safely accommodate it's dimensions.
Would it have had enough fuel to not only made the trip from Tinian to the rendezvous point, then on to the primary and secondary target then on to Iwo Jima (Okinawa only in an emergency)? For the record, the Silverplate B-29s had a capacity of 7,250 gallons of fuel.

And what about both the imposed drag penalty of the bulging fuselage as well as additional fuel burn for extended (unscheduled) loiter time?

Nearly an hour was spent trying to find a bombing solution for Kokura before moving on to Nagasaki. Additionally, and extra 15 minutes was spend at Yakushima.

Add to that, the extra fuel consumed during the mission with the altitude change due to bad weather.

And finally, because if the faulty fuel transfer pump, Bockscar could not use 640 gallons if fuel, but instead, had to carry that weight home.

So taking all of these actual events into consideration, could a modified Lancaster have made the exact same journey under the exact same conditions?

Sweeney ended up diverting to Okinawa due to lack of fuel. This doesn't negate the main point though.

 

[GrauGeist]

Sweeney ended up diverting to Okinawa due to lack of fuel. This doesn't negate the main point though.

Right - due to alternate cruise altitude, exceeding planned loiter time at rendezvous point, nearly an hour spent at Kokura and the diversion to Nagasaki and a faulty fuel transfer pump, meant that there was literally not enough fuel remaing to taxi to the ramp at Yontan field.

Someone else brought up the point of unfavorable wind conditions earlier and this may have been the case for the inbound leg. The rendezvous was changed from Iwo Jima to Yakushima and the cruise altitude was raised to 17,000 feet due to "poor weather". As it happens, the poor weather was actually a monsoon - which explains why Kokura, Nagasaki and everything else was obscured by clouds.

Something else that might be interesting to note, is that three hours into the mission, Fat Man armed itself. Ashworth and an assistant actually worked on the bomb and resolved the issue (two switches had been reversed) - a point that is often overlooked in this thread: the bomb (Little Boy and Fat Man) needed to be accessed by the Weaponeer.

 

[RCAFson]

Right - due to alternate cruise altitude, exceeding planned loiter time at rendezvous point, nearly an hour spent at Kokura and the diversion to Nagasaki and a faulty fuel transfer pump, meant that there was literally not enough fuel remaing to taxi to the ramp at Yontan field.

Someone else brought up the point of unfavorable wind conditions earlier and this may have been the case for the inbound leg. The rendezvous was changed from Iwo Jima to Yakushima and the cruise altitude was raised to 17,000 feet due to "poor weather". As it happens, the poor weather was actually a monsoon - which explains why Kokura, Nagasaki and everything else was obscured by clouds.

Something else that might be interesting to note, is that three hours into the mission, Fat Man armed itself. Ashworth and an assistant actually worked on the bomb and resolved the issue (two switches had been reversed) - a point that is often overlooked in this thread: the bomb (Little Boy and Fat Man) needed to be accessed by the Weaponeer.

Sweeney was quite prepared to ditch the aircraft, in order to accomplish the mission; that's the real point here. Groves thought arming the bombs in-flight was unsound and would have overruled it if he had been informed:

Groves, Now it can be told:

"Parsons had decided with Farrell's approval to complete the final
assembly of the bomb after takeoff. His purpose was to minimize the
hazards of a crash on Tinian. I had previously said that I was op-
posed to this as unwise, because it was unnecessary and because it
would be very difficult to do it in cramped conditions in the plane.
I was not informed of the plan until it was too late to interfere... (p.317)

I was not possible to "safe" the Fat Man by leaving the assembly (p.343-4)
incomplete prior to take-off, as had been done in the case of the
Little Boy. There was considerable discussion among the technical
staff about what would happen if the plane crashed, and possibly
caught fire, while it was taking off. They realized that there would be a
serious chance that a wide area of Tinian would be contaminated if
the plutonium were scattered by a minor explosion; some thought that
there was even a risk of a high-order nuclear explosion which could
do heavy damage throughout the island's installations. Of course, we
had gone into all this at length during our preliminary planning, and
on the basis of my own opinion, as well as that of Oppenheimer and
my other senior advisers, that the risk was negligible I had decided that
the risk would be taken.

As happens so often, however, there was constant interference
by various people in matters that lay outside their spheres of re-
sponsibility. Throughout the life of the project, vital decisions were
reached only after the most careful consideration and discussion with
the men I thought were able to offer the soundest advice. Generally,
for this operation, they were Oppenheimer, von Neumann, Penney,
Parsons and Ramsey. I had also gone over the problems at con-
siderable length with the various groups of senior men at Los Alamos,
and had discussed them thoroughly with Conant and Tolman and
with Purnell and Farrell and to a lesser degree with Bush. Yet in
spite of this, some of the people on Tinian again raised the question
of safety at take-off at the last moment. Their fears reached a senior
air officer, who asked for a written statement to the effect that it would
be entirely safe for the plane to take off with a fully armed bomb.
Parsons and Ramsey signed such a statement promptly though with
some trepidation, possibly with the thought that if they were proven
wrong they would not be there to answer. Ramsey then advised Op-
penheimer at once of the various design changes that must be made
to ensure that future bombs would in fact be surely safe."

We have to consider, as Groves did, that arming the bombs in-flight, increased the probability of mission failure.

 

[RCAFson]

The presumption that he received specific details such as engineering drawings, dimensions and such like is hearsay and can only be proven if we know for certain exactly what he received. It is highly unlikely he would have been aware of the code names Thin Man and Fat Man as in 1943 these were used within the Manhattan Project alone.



Again, see above. Unless we know exactly what Ramsey sent him, what these details were, then any stipulation that it could definitely carry a Fat Man is merely speculation until proven otherwise, .

You won't give up on trying to smear Ramsey and Chadwick's competence:

What you are proving is that no amount of evidence will ever be sufficient for you:

Ramsey was assigned to head the Delivery Group of the Ordnance Division and later
served as deputy to Pasion." His immediate tasks were to design the bomb casings that
would carry the gun-assembly bomb and implosion bomb. By the end of 1943 it had
already been established that the gun-type bomb-Thin Man-would weigh on the order
of five tons. Ramsey assumed that the implosion bomb would weigh approximately the
same. Given their size and weight, there were only two possible choices for an aircraft to
deliver the weapons, the British Lancaster or the American B-29, which had begun
production in September.

Ramsey favored the Lancaster and traveled to Canada in early October 1943 to meet Roy
Chadwick, the plane's chief designer, Chadwick was in Canada to observe the initial
Lancasters coming off the production line at the Victory Aircraft Works, Milton Airdrome,
in Toronto. Ramsey showed Chadwick preliminary sketches of the large-thin-shaped and
stubby shaped-bombs and later wrote with more details.(12) Chadwick assured Ramsey that
the Lencaster could accommodate them.

When Ramsey returned, he wrote to Parsons suggesting that the Lancaster be seriously
considered and planned a memo to General Groves recommending that a modified
Lancaster be used.(13)The bomb bay was thirty-three feet long and sixty-one inches wide.
The depth was only thirty-eight inches, but this could be modified. The Lancaster's ceiling
was 27,000 feet, its speed 285 miles per hour, and takeoff required only 3,750 feet of runway
-a critical matter wherever it would be based.
(12). Norman F, Ramsey Jr. to Roy Chadwick, October 23, 1943, Folder Dr. Norman Ramsey, Box 6,
Tolman Files, RG 227/81, NARA.
(13). Memo, N. F, Ramsey to Capt. W. . Parsons, October 14, 1943, Lancaster Aircraft, Folder Dr Norman Ramsey... NARA
" (Norris, pages 316-317 Racing for the Bomb)

Again, the actual FAT MAN width was 60.25in or less.

 

[ThomasP]

If the Lancaster could have achieved the range requirements, we can assume that a 'guppy' bulge modification would have to be done. If a 'guppy' bulge is assumed, then access to the nose of the 'Fat Man' could be easily achieved. The area in the oval below is the part of the 'Fat Man' that had to be accessed in flight. I do not think arming of the bomb in flight would be a problem - unless there is something else involved on that I am not aware of?

 

[Simon Thomas]

The Grand Slam carrying B.I Specials were dogs to fly and even in the Lancaster I and III's handling notes, at MTOW the aircraft can only be flown straight and level until its weight is below 63,000lbs. Oil temps in the climb were at their highest levels before the engines overheated and the climb had to be skillfully managed, the engines themselves reached extreme temperatures and handling was severely degraded. Not the best condition to be in on a long haul bombing operation of such importance.

That sounds like SOP for normal B-29's. The FI engine in the Silverplate was better, but still needed the crew on their A game.
Fifi takes careful operation, and that is with a light load and a modified version of the 3350.

 

[nuuumannn]

As to the drag question, again it rather depends on the changes made to the Lancaster to perform the mission. The Lancaster's overall drag could be considerably reduced by removing the H2S blister and mid-upper turret, and replacing the front turret and perhaps the bomb aimer window with a more streamlined design. Such changes would introduce some trade space from a performance perspective.

Putting it (very) simply, drag is about the shape of the object, its physical size and frontal area and how it moves through the air. Other complexities include the viscosity of the air, the speed of the object etc. With an increase in speed comes an increase in drag, which correspondingly reduces acceleration and increases workload to maintain specific values. Basically, the faster you go, the greater the amount of resistant force on the aircraft and therefore the greater the amount of work required to maintain those values. Acceleration decreases and the engines have to work harder, which means a higher fuel consumption as the aircraft accelerates on take off and into establishing the climb. With aircraft that are heavily laden, around 20 percent of their total fuel load is used just to get off the runway (a value roughly calculated in a class exercise using a 747, its total fuel load and its MTOW versus its speeds and acceleration). By even fitting a streamlined bulge to the underside covering the Fat Man would be like increasing the frontal area of the Lancaster by nearly twice its value since the bomb is almost the same diameter as the aircraft.

Oh and Mark, as an engineer as you've pointed out, since you don't know the exact content of what Ramsey revealed to Chadwick, it's best not to presume until you do.

you won't give up on trying to smear Ramsey and Chadwick's competence:

Nothing of the sort, so watch it.

So your argument, which comprises an utter lack of understanding of the basics of aviation, fabrications and sheer fantasy are not an insult to their efforts? Lancaster VIs with miracle engines that never fail??? Silverplate Lincolns??? The ability to carry Fat Man with no impact on the aircraft's performance at all??? Fantasy fuel loads???

Gawd...

 

[RCAFson]

(1)With aircraft that are heavily laden, around 20 percent of their total fuel load is used just to get off the runway (a value roughly calculated in a class exercise using a 747, its total fuel load and its MTOW versus its speeds and acceleration).


(2) Nothing of the sort, so watch it.

(3) So your argument, which comprises an utter lack of understanding of the basics of aviation, fabrications and sheer fantasy are not an insult to their efforts? Lancaster VIs with miracle engines that never fail??? Silverplate Lincolns??? The ability to carry Fat Man with no impact on the aircraft's performance at all??? Fantasy fuel loads???

(1) Twenty percent?

Fuel consumption for TO = fuel burned for warm-up and taxi and then fuel burned at full throttle during the acceleration to TO speed, and given that the runways are less than 10K ft long, this cannot exceed ~1min. Maybe you meant two percent?

(2) Sure sounds like it.

(3) I'd refer readers to (1), above. We know the AMPG of Lancasters with Grandslam being carried externally, and amazingly, it's little different than a Lancaster with all internal bomb loads with a top turret and radome...

Grandslam = 2350rpm, 4.5lb boost. 212TAS = .99

Internal = 2350rpm 4.6lb boost, 214TAS = 1.01

 

[nuuumannn]

1) Twenty percent?

(2) Sure sounds like it.

1) Yup, 20 percent. You really don't know about this stuff, do you...

2) Nope, again, you are seeing something and misinterpreting it.

 

[FLYBOYJ]

Fuel consumption for TO = fuel burned for warm-up and taxi and then fuel burned at full throttle during the acceleration to TO speed, and given that the runways are less than 10K ft long, this cannot exceed ~1min.

If a careful start up, taxi, run-up and extra checklist followed because of the payload and mission, I'd say more like 10 to 20 minutes. Even in the tropics, I don't see the engine oil warming up to TO temps in less than 5 minutes. Shoot, when I fly my 172 it could take 5 minutes just to get to the run-up area and that's when I'm the only one on the field!

 

[RCAFson]

1) Yup, 20 percent. You really don't know about this stuff, do you...

2) Nope, again, you are seeing something and misinterpreting it.

1) Rather than admit to a rather obvious mistake, you double down on it...

2) Ditto.

 

[swampyankee]

I think some of the people criticizing the Lancaster for its range are missing (or bypassing) a fairly important point: when many of these discussions were underway, the Normandy landings had not yet occurred and it was uncertain whether WWII in Europe would last longer than WWII in the Pacific. The original target for the atomic bomb was Germany, not Japan, and that eliminates some of the issues with the Lancaster's range. Clearly, it doesn't address any of its shortcomings with regards to vulnerability, since the Lancaster was both slower and lower flying than the B-29.

 

[nuuumannn]

When doing ground runs in our turboprops, after start we have to allow the oil temp to warm up into the green before we take the props out of feather, and when the pilots are flying, that's before even contemplating putting the condition levers into Max and pulling the power levers out of flight idle and taking the park brake off. The time that takes depends on a lot of things, how warm the engines were before we began running them, OAT, and if we've done a comp wash, the engine is full of water, so...

But that's very different to fuel consumption on take off at MTOW, and you add all that extra drag of a big bomb underneath and your plane becomes a barn door that gets bigger in size as you accelerate into the climb.

 

[nuuumannn]

The original target for the atomic bomb was Germany, not Japan, and that eliminates some of the issues with the Lancaster's range.

Well, that makes some sense, but the hypothetical is that the Lancaster could do the trip to Japan. Of course it could if Berlin was the target and they were flying from England...

 

[nuuumannn]

1) Rather than admit to a rather obvious mistake, you double down on it..

Says the internet warrior to the aircraft engineer who works on aircraft every night and has years of experience doing so...

 

[DerAdlerIstGelandet]

1 minute to start engines, warm up engines, run through pre-takeoff checks, taxi to the active, and take off?

I've never done that in 20 years of flying and crewing.

Not even an aircraft on standby that has been run up, been through all the checks and shut down waiting for a mission.