From what I understand, increasing the power of large hydrogen bombs had long reached the point of diminishing returns. Basically, you were just blasting a larger hunk of atmosphere into space.
B-36 - Why a Pusher??
- Thread starter Piper106
- Start date
I think the goal was to come up with a weapon that with a properly placed air burst could ignite a huge area all at once, creating the mother of all firestorms, which would then move downwind, devastating and depopulating entire regions. Scorched earth without the effort of invading and occupying. Then along came the concept of nuclear winter and the folly of supermegatonnage began to sink in.
As a teenager, I read all kinds of articles about these ideas.
While Grau Geist had largely addressed this, the design of the B-36 wasn't to carry a huge nuclear warhead: It was to be able to fly from the Continental United States, bomb Germany, and return.
The requirements initially called for a range of 12000 miles while carrying 4000 lb. of bombs, at an altitude of 40000' at 275 mph true airspeed, a maximum speed of 450 mph, while carrying adequate defensive armament. Far as I know, these stipulations also called for the ability to carry heavier loads over shorter distances as well.
It wasn't long before the requirements called for a range reduction of 10000 miles while hauling 10000 lb. of bombs, with the same cruise and maximum speeds, and altitude requirements. I don't think there was any change in defensive armament requirements at the time. This might have been out of a desire to hit Japan from the United States, as well as heap more bombs on either.
Around 1944, there appeared to be a requirement for the aircraft to carry it's own escort fighter onboard, given that escort fighters were seen as virtually essential to daytime bombing (something that was generally the USAAF's preference), and the range of the B-35 or B-36 would make a traditional escort fighter all but impossible. The requirements initially called for either a plane that was partially submerged inside the plane, then one that was carried completely inside the bomb-bay (I don't know if there were proposals for piston or jet powered aircraft, but ultimately a jet-powered design would be built called the XF-85).
Somewhere between 1944 to 1945, there was a change in altitude requirements from 40000' to 50000' and a range increase from 10000 statute to 10000 nautical miles as well. I don't know if there were any changes to the defensive armament at the time, but I do remember seeing some proposals that included 37mm cannon in the turrets, though it'd later change to 20mm cannon.
Because the aircraft was large and required large components to be built to standard, and not everybody realized this: It resulted in lots of components being built below or outside the specified standard; because this required time to undo and rebuilt, as well as the fact that the economy quickly slowed from wartime to some semblance of peacetime: The aircraft wouldn't fly until August of 1946, around a year late; with the intended supercharger either cancelled, or not available in time: The aircraft was limited to around 10000'-15000' instead of the intended goal for a considerable period of time; while an appropriately suitable turbocharger was installed: The altitude ended up below the specified amount, as well as the top-speed (though the cruise speed might have been a little higher), though changes were made to trim off weight (some proposals might have involved the removal of at least some of the turrets), I'm not sure if the aircraft ever achieved the intended altitude over target, particularly when loaded, and it's range came up a bit below the 10000 nm figure.
Like most aircraft it had some basic problems that had to be overcome, such as the landing-gear design, which produced excessive footprint pressure, that meant only 3 airfields could operate the plane, but it was also the first USAF bomber that could be adapted to accommodate nuclear weapons with no major issue. That said, the four bomb-bays the aircraft had were eventually modified into two positively enormous weapons bays, and the normal maximum payload was 72000 pounds, with an overload capacity, often listed as 86000 lb, possibly as much as 87200 lb., while carrying 2 x Cloudmakers (they were basically earthquake bombs inspired by the Tallboy and Grandslam) which weighed around 43,600 pounds apiece. This also made it a natural fit for the first aerially deliverable hydrogen-bombs.
While I could be wrong about this, the first H-bombs actually carried liquid deuterium and tritium instead of the later lithium deuteride: This resulted in some degree of boil-off, and the need for dewar-flasks to replenish the stuff in flight. I think these were called "Emergency Capability" bombs (as in "It's an emergency -- we gotta bomb the Soviet Union into the stone-age!)
Though I don't know the dimensions of the B-52's bomb-bay, it didn't seem anywhere NEAR as large as the B-36. That said, it wouldn't be the first time I was wrong.
If I recall, it was either doubtful that the airplane would escape the blast at best, and most likely, they'd be hoist by their own petard: Interestingly, the high power of hydrogen-bombs lead to a proposal of a modified B-47 designed to fly as a drone. Ultimately, a less extreme solution revolved around a ribbon chute that would deploy in the fall, to extend the escape time.
It used a lead-tamper for the third stage. The yield likely would have been around 100 MT, and with modifications, they had anticipated up to 150 MT.
From what I recall, the reason had to do with the fact that the Tu-95 that carried it would probably get incinerated or vaporized by the bomb it dropped.
Interestingly there was a proposal to use the basic design of the weapon as an ICBM warhead: The UR-500 (later Proton Rocket) was to haul it to a city near us. Fortunately it was not used in that role, and instead proved a very effective means of launch stuff into space.
Was there any corruption with the B-35 prior to 1944? I remember most of the corruption that occurred was after 1946 or so.
special ed
1st Lieutenant
- 7,094
- May 13, 2018
The corruption occurred late 1940s as Symington appears to have invested in Convair. Since Bill Northrop resisted the merger, Northrop did not get aircraft contracts until the 1959 privately funded N-156 became the F-5A for Military Assistance to smaller countries. Eventually, it was seen that a trainer version would be beneficial hence the T-38.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Northrop's F-89 (N-24) was purchased by the Air Force in the late 40's.
ThomasP
Chief Master Sergeant
My understanding is that the 10,000 mile range with the 10,000 lb payload specification for the B-36 was the minimum needed to allow hitting any target of realistic potential (ie Europe, USSR, China, etc) from bases in the US and continue on to a safe recovery point on or over friendly/neutral territory. This would allow recovery in the UK or North Africa if the target was in Europe/western USSR - Saudi Arabia or Turkey if the target was in central USSR - Japan, Korea, Australia, if the target was in eastern USSR or China. For the most part, the longer range missions were planned to be one way. As far as I know the range requirement was found to be unrealistic (a max effective range of about 7,500 miles was achieved) and plans were to launch from closer to the target (the missile installations in the USSR) with recovery as before, or in many cases a true one-way mission.
special ed
1st Lieutenant
- 7,094
- May 13, 2018
GrauGeist is correct. Forgot all about them. I think those contracts were well under way and they were hoped to stop the Tu-4s should they come over the pole. I remember being told by a "B-89" driver that a tail chase of a Tu-4 was impossible and if he missed the intercept, he may as well go home and refuel.
Joe Broady
Airman 1st Class
- 121
- May 30, 2019
But B-36 engines were not buried in the wings, though the myth has been around for decades. "The big R-4360s were buried in the thickest part of the wing and drove the pusher propellers through long rearward extension shafts." (Herschel Smith, "Aircraft Piston Engines," 1981)
In reality, the B-36 had its Wasp Majors almost as close to the propellers as a conventional tractor installation. There was just a short extension case for a little more separation. (That from a manual for engine students at Sheppard AFB, which is on the web, I can't remember where.) This is clear if you look at any photo (sorry, haven't got a link at hand) of B-36 maintenance with nacelle access panels removed. The engines are just ahead of the props.
ThomasP
Chief Master Sergeant
swampyankee
Chief Master Sergeant
- 4,306
- Jun 25, 2013
Because, from all published data, its performance was much worse than the B-52.
From a frontal view, it is apparent that the engines make only a small contribution to the frontal area of the plane. They are not completely buried, but the B-36 comes closer to a buried engine installation than nearly all other contemporary multi-engine bombers. As always, there is a host of engineering trade-offs to consider.
wuzak
Captain
I believe the long range required was the fear that the UK would fall. If that were the case and the US was at war, then bombing missions would need to be flown from the Continental United States to bomb targets in Europe.
ThomasP
Chief Master Sergeant
Hey wuzak,
I may be wrong, but I thought the original range specification for the B-36 was 12,000 miles with X payload, and that it was decreased to 10,000 miles with 10,000 lb (ie a Mk III A-bomb) after(?) the war.
I may be wrong, but I thought the original range specification for the B-36 was 12,000 miles with X payload, and that it was decreased to 10,000 miles with 10,000 lb (ie a Mk III A-bomb) after(?) the war.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The B-36 was born during the Blitz, when the U.S. (and many others) feared Britain would not be able to hold out.
The original range minimum proposed was a combat radius shy of 5,800 miles, so the USAAF request in spring of '41 called for a max. range of 12,000 miles but after consideration of what was possible to build in a short amount of time, revised the max. range to 10,000 miles.
Even the B-19 (the result of a USAAC request for an extra long range bomber) which was nearing it's first flight, had a max. range of 5,700 miles with a bombload, roughly half of what was needed to reach Berlin and return home.
The original range minimum proposed was a combat radius shy of 5,800 miles, so the USAAF request in spring of '41 called for a max. range of 12,000 miles but after consideration of what was possible to build in a short amount of time, revised the max. range to 10,000 miles.
Even the B-19 (the result of a USAAC request for an extra long range bomber) which was nearing it's first flight, had a max. range of 5,700 miles with a bombload, roughly half of what was needed to reach Berlin and return home.
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That seems to fit with what I understand: The B-35 was initially favored by the bomber-generals, possibly because it was more aerodynamic, longer-ranged, was actually lighter, had better defensive armament coverage, and may have been able to fly faster, and higher.
It appears to have fallen out of favor around 1944, and while I don't know the reasons, if directional control and stability was realized to be a problem, it seems to explain matters pretty well. The B-36 was slated to fly at that point.
Whether there was any intent to fly the XB-35 as a proof of concept in 1944 anyway is unclear, but post-war, there did seem to be some interest, but it's around this time (far as I remember), that things went sideways: There were basically three problems that plagued the B-35 with two being technical, and one being corruption.
The technical issues comprised...
- Stability issues
- The aircraft seemed to have serious issues with directional stability, showing a profound tendency to fish-tail, and wallow all over the place: This would have affected bombing accuracy, something that was actually a problem on the B-24, though to a much lesser extent. It would also have resulted in a longer bomb run than say the B-29, and B-36.
- The aircraft appeared to be a bit twitchy on pitch: This seems to be a problem with flying wing-designs and some tailless aircraft (depending on the length of the mean aerodynamic chord), which might be related to the fact that, in order to have workable pitch control: You need to have sufficient spacing from the control surfaces to the bulk of the aircraft's mass, so the bulk of the mass ends up bunched in the middle (and given the choice between a little too much or a little too little controllability, most designers would opt for a little too much). I've been told this also affects dynamic stability as well, setting up oscillations (I'm not sure if the B-35 had issues with this on pitch). Interestingly, at high AoA, the pitch was fairly stable, possibly owing to the use of slots on the wings.
- Mission priority changes: In the post-war period, there was a change from delivery of bombs and incendiaries, to the delivery of nuclear bombs.
- As with the B-36, it was designed to carry 10,000 pounds of bombs a distance of 10,000 nautical miles normally, with the ability to carry larger loads over shorter distances, which it was completely capable of. It could also carry 51,000 pounds of bombs maximum, but the biggest bombs it was capable of carrying were 4000 pounds.
- The only 4000 pound bomb that I know of in the US inventory was the AN-M56 which was 117.25" in length, with a body diameter of 34.25" to 36", and a total diameter of 47.625".
- Early nuclear bombs were quite large owing to poor fission efficiency early on, which resulted in them being larger than many of the bombs used in WWII in one dimension or another (often diameter).
- Mk-1 (Little Boy): The weapon weighed between 8900-9700 pounds (depending on source) as released, and was 28" in diameter by 128" in length. While it was fairly slim by the standards of nuclear weapons: Only 5 were built, of which one was expended on August 6th of 1945.
- Mk-3 (Fat Man): The weapon weighed 10300 pounds and, while the same length, it was 60" in diameter, and 120 of them were built, making it a considerably more popular design that such a plane would be expected to carry.
- Mk-4: It was the first assembly-line nuclear weapon to be produced, 550 were built, and, while it was about the same size as the Mk-3, it was about 500-600 pounds heavier.
- The Mk-1 and Mk-3, if not all, required the bombardier to climb into the bomb-bay to assemble the weapon.
- As with the B-36, it was designed to carry 10,000 pounds of bombs a distance of 10,000 nautical miles normally, with the ability to carry larger loads over shorter distances, which it was completely capable of. It could also carry 51,000 pounds of bombs maximum, but the biggest bombs it was capable of carrying were 4000 pounds.
There was also a lot of disinformation spread that the aircraft should not even be spin-tested because it would be too dangerous to do so, but it was nonsense: Tests were performed to this effect. While I wouldn't be surprised if it was difficult to recover from a spin, at the same time, it was physically possible.
Wait, they wanted Northrop to merge with Convair? I thought they wanted a plant that was then currently used by Convair to manufacture the planes, which Northrop felt was unfair to his employees. If I recall, some of Northrop's underwriters also managed to ensure that he didn't get to make any decisions, or they had to pass through somebody else.
It's interesting to note that most of the problems with the aircraft were essentially fixable. Otis (yep, the old elevator designer) had developed an early stability augmentation device (which originated on elevators, which is why they slow down as they near the top rather than just go *BANG*) which corrected for the yawing issues. While I'm not sure if this was ever applied on the YB-35, it was on the YB-49.
The YB-49, as I understand it, had the 4 x R-4360's and the propellers that went with them removed, with 8 x J35's (supposedly they couldn't accommodate the J47's but I can't figure out why, unless it was weight related, as their dimensions were basically identical) placed in their spot, with fins grafted on where the propeller shafts were located to add stability back that was taken away. With roughly the same stability, the system was said to meet the specifications for bombing accuracy (admittedly, the description seemed to indicate it barely met the requirements).
Well, GrauGeist already pointed out that the F-89 ended up being developed for the USAF.
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special ed
1st Lieutenant
- 7,094
- May 13, 2018
See post #159 and look up the you tube interview.
Agreed. In addition to is lessor range the B-49 needed pitch and yaw dampers, they took a while to work and it couldn't carry certain nuclear bombs. No one is going to go back to the special physics guys and tell them to miniaturise their bomb some more because although the B-36, B47 and B52 could carry their bomb they're not a nifty as a flying wing.
The flying wing technology should have been perused more. The corruption allegations are likely true, they usually are but the aircraft couldn't do the job as well.
The B-49 needed flight control 'augmentation' something that I believe came to maturity with the SR-71/YB12A. Maybe some other aircraft.
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swampyankee
Chief Master Sergeant
- 4,306
- Jun 25, 2013
I was referring to the B-60, not the B-49. The B-49 did have handling problems which, pre-digital flight control, pre-smart bomb were intractable. It also, like most flying wings, had surprisingly large runway requirements.
davparlr
Senior Master Sergeant
The YB-49 was a YB-35 modified to install j35 engines so there were no YB-49s with R-4369 engines. The YB-47, basically a contemporary to the YB-49, also had J-35 engines and the B-47 later received the J-47, so, I think the J-47 was not ready for the YB-49 and I suspect there was no eagerness to upgrade the YB-49.
There is no doubt that the aircraft with the most potential for handling the future mission of enemy penetration was the B-49 due to its inherent stealthiness. The B-36 was obsolete when it became operational, only one year before the MiG-15 entered service and we know what it did to the B-29 force in Korea.
Performance comparisons using corrected NACA data (as stated in "Goodby Beautiful Wing" by Terrence O'Neill).
B-35 - B36
Empty wt. lbs 89,000 - 133,800
Wt. Cruise 135,000 - 212,000
Wt. Gross 180, 000* - 287,000 * weight reduced from max due to AF refusal to test landing gear
wt. max T/O 207,000 - 311,000
Miles-to-target 5,100 -3,600
Speed Combat (mph) 405 - 331
Design Ceiling ft. 49,000 - 40,000
Note: these B-35 numbers are using NACA corrections to previous flight test estimates using N9M reduced scale test aircraft. B-35 had the potential of performing the same mission as the B-36 at 60% of the weight.
Note also: That the B-49 radar cross section could have easily been improved significantly by moving the engine inlets to top of wing ala B-2. No need to make sophisticated ducts because there would be no airborn radar platforms above it probably well into the '50s, if not later. The B-49 could be practically invisible from the front to Russian radars.
