4500 lb Rocket-Assisted 'Disney Bomb' For B-17 and B-29

[Zombificus 570]

The 'Disney Bomb', also known as the 'Disney Swish' and, officially, the '4500 lb Concrete Piercing Rocket Assisted Bomb', was a rocket-assisted bomb developed jointly by Britain and the US towards the end of the war in order to penetrate thick-roofed structures such as submarine pens and bunkers. Encased in a thickly-armoured casing, a 500 lb warhead was propelled towards the ground at up to 990 mph (Mach 1.29) by a rocket motor in its tail, the bomb's sheer speed allowing it to pierce at least 4.47m of concrete, with around 5 metres being the estimated maximum penetration. Due to unspecified 'technical issues', no British plane was capable of carrying the bomb (despite the Lancaster having a large enough bomb bay and good enough performance), so B-17s of the Eighth Air Force based in Britain were the only bombers to employ the Disney Bomb during WWII. After the war, continued testing was done with the new B-29 Superfortress, but postwar testing showed that the Disney (along with all of the other bombs tested in Project Ruby) was flawed, so the USAF moved onto new bomb projects and the B-29 never launched a Disney in anger. 

 

 

History:

 

The idea for the Disney Bomb, and the origin of its name, came from a 1943 propaganda film by Walt Disney, "Victory Through Air Power", which showed a similar, fictional weapon. A group of Royal Navy officers who saw this film, led by the bomb's inventor, Captain Edward Terrell, seized upon the idea as a potential way of dealing with German U-Boat Pens, which were extremely well fortified and couldn't be penetrated by anything besides the very largest British bombs, such as Tallboy and Grand Slam. Knowing that penetration increased with velocity (Grand Slam and Tallboy acquiring theirs by sheer weight), they saw the rocket propulsion as a way to enhance penetration without building such colossal bombs, and despite having no planes that could carry the weapon, the Navy proceeded with development of the bomb. Initially, it was hoped that the RAF's Bomber Command might be the delivery vector, but the Air Force never had much interest in the design and cited 'technical issues' which would prevent the weapon being launched from British planes. Given Bomber Command's disinterest, the fact that the Lancaster matches or exceeds the B-17 in most aspects that might have affected it carrying the Disney, and that we have no record of what the 'technical issues' actually were, this may have simply been an excuse on the RAF's part to avoid having to waste time on a design they didn't think was worth developing. 

 

The poster for Disney's "Victory Through Air Power", and the film's fictional rocket-bomb, penetrating a submarine pen.

 

Nevertheless, the Royal Navy persisted with the design, and with the US Eighth Air Force present in Britain, they had an alternative means of delivering the new bomb to its targets. Unlike Bomber Command, the USAAF were eager to employ the new weapon, and they soon began working with the Royal Navy to devise a way for them to be carried by their B-17 bomber force. Ultimately, as the Disney was too long to fit inside the B-17's bomb bay, external mountings on the wings already in use with the GB-1 glide bomb became the chosen carrying method, with two Disneys being carried -- one under each wing -- in much the same way as the GB-1 was. Testing commenced in early 1945, with testing first at Southampton to test accuracy and calibrate bomb sights, then at the recently captured Watten Bunker in France by two B-17s each deploying a pair of Disneys to satisfactory effect, prompting the weapon's acceptance for service. During the war, the Disney was dropped primarily by the 92nd Bombardment Group, with the 305th and 306th Bombardment Groups also using them in smaller numbers; the 94th Bombardment Group trained with them but didn't employ the weapon in combat before the war's end. 

 

IJmuiden's E-Boat pens, the first Disney Bomb target.

 

German E-Boats housed in Schnellbootbunker AY and BY (aka SBB1 and SBB2) in the Netherlands were becoming a serious threat to Allied shipping, and had been unsuccessfully attacked four times by the RAF since August of 1944, with a total 53 Tallboy bombs having been expended in the attempts. These bunkers, protected by 3.0m (SBB1) to 3.7m+1.2m (SBB2) of concrete, were chosen as the Disney Bomb's first target, with nine B-17s of the 92nd Bombardment Group sent out to the IJmuiden port in February 1945 to see if the new weapon would have more success against SBB2's thick construction than the Tallboys and conventional bombs employed in previous missions. Royal Navy intelligence learned soon after that the penetrations had been successful, but the mission had been a waste since the E-Boat pens had been empty at the time, so a second mission was quickly planned targeting the SBB1 bunker. This attack, again using nine B-17s, was carried out on the 14th of March, but whether it was successful is not noted in my sources.

 

A Disney Bomb being transported.

 

Following up an RAF raid against the Valentin Submarine Pens, which had weakened the structure with two Grand Slam earthquake bombs, 36 aircraft of the Eighth Air Force (12 of which were Disney Bomb veterans from the 92nd BG) attacked the pens three days later, on the 30th of March. Although more than 60 Disneys were dropped, they largely missed the main target, wreaking havoc on the surrounding facilities but leaving the Valentin pens themselves mostly unharmed, the one bomb to hit its target unable to do much damage by itself. The final Disney Bomb attack of the war came on the 4th of April, 1945, when 24 B-17s were sent to bomb fortified targets in Hamburg; owing to cloud cover, these Disneys were aimed by radar alone; as with the second IJmuiden raid, my sources don't mention the effects of this mission. As the war drew to a close, another mission planned for April was cancelled, leaving the number of Disneys dropped in the war at just 158.

 

Penetration of Disney Bombs during Project Ruby.

 

After the war, considerable testing was done on the weapon, particularly by the US, which was looking for the best elements of existing bomb designs for use in further developments. In June 1945, the Watten Bunker was once again a target of Eighth Air Force B-17s, acting on behalf of the RAF; it proved too small a target to be a good test target, and the French objected to further bombings in peacetime, so later tests moved onto a German bunker on Heligoland island and the Valentin Submarine Pens. These bombings, carried out in 1946 as part of the Anglo-American "Project Ruby" tests, showed that the Disney had impressive penetrative power (these tests are what confirmed its ability to pierce 4.47m of concrete and implied a 5.08m maximum depth) but also that its rocket motor was unreliable and inaccurate, and its warhead too small to guarantee destruction of a target without numerous penetrations, which its inaccuracy made relatively unlikely. None of the many bombs tested under Project Ruby were found fully satisfactory, so the Disney wasn't alone in being flawed, and the US decided that a rocket propulsion system would be considered for future weapons of equivalent role. B-29s, which had been one of the bomb's Project Ruby launch platforms, were considered for use with any Disney Bomb followup, but in the end it would be decades before the next rocket-assisted bomb in US inventory, leaving the few Disneys dropped as the B-29's only experience with this kind of weapon.

 

Specifications:

 

 

Length: 5.03m

Body Diameter: 380mm

Tail Diameter: 430mm

Mass: 4500lb (2000kg)

Warhead: 500lb (230kg) of Shellite

Fuse: Base Fuse 

Propellant: Cordite

Burn Time: 3 Seconds

Max Speed: 990 mph (1590 kph; Mach 1.29)

Launch Platforms: B-17E, B-17F, B-17G, B-29 (Testing Only)

 

Launching The 'Disney Bomb':

 

The Disney was suspended from its launch aircraft in two cradles on the underside of the wings, of the same design also used to launch the GB-1 glide bomb, with three arming wires linked to the bomb's warhead fuses, rocket ignition circuit and generator lock. To ensure that the bomb penetrated as far as it could before exploding, the fuses were installed in the base of the bomb rather than the nose. Because the rockets' ignition circuits needed to be triggered after the bomb's release from the plane, so as to give it time to swing nose-down towards the target, a generator was installed in the rear half of the bomb with a lock to prevent it turning while still attached to the plane. Six fins kept the bomb's descent stable until the rockets were ignited.

 

Left: A Disney Bomb being loaded. Right: A B-17G with Disney Bombs taxiing.

 

When the plane released the bomb, the three arming wires would be tugged, one triggering the bomb's fuses, one releasing the lock on the generator so that it could turn and produce power, and one triggering the ignition circuit linking the generator to the rockets. This last circuit would be either a timer circuit or a barometric (air-pressure-based) circuit, depending on the mission parameters. The bomb would be dropped from a predetermined height, most often 6100m, and after the timer or barometric circuit triggered the rocket motors (19 cordite-filled tubes, identical to those used in the RP-3 rocket) they would initiate a 3-second burn, accelerating the Disney to an impact velocity of 990 mph. A protective cover, fitted over the rockets at the rear of the bomb, would be jettisoned upon ignition, which typically occurred 30 seconds after launch from 6100m,.   

 

Its Place In War Thunder:

 

Currently, the Disney Bomb doesn't quite have the niche in War Thunder that it did in real life, but as suggestions for more complex bomb targets have been passed to development, I feel it's good to get options for bombs that would be useful new options when bomb targets do eventually get updated. While it has a relatively small warhead, owing to its deep-penetrating design, the bomb was capable of generating damage well in excess of a conventional bomb with the same warhead. In War Thunder as it currently is, the Disney Bomb should deal similar amounts of damage to bases as large conventional bombs in the 1000-2000lb range, if not more, to reflect that its design purpose was to pierce the outer parts of a structure and deliver its full payload to the unprotected interior, rather than inflict damage from outside via brute strength. Its blast radius, however, would be small, making it a poor choice against ground targets, especially since it was also typically launched at high altitude, and could be inaccurate if any of its 19 rockets were faulty.

 

Against ships, while potentially hard to aim, it should be more than capable of killing battleships and carriers with one central hit, again due to the fact that it penetrates before exploding. As (IIRC) Japanese AP bombs don't currently have a penetration mechanic, making them inferior to the standard bomb of their size, the Disney Bomb's functionality could also be applied to them for naval targets, giving them a reason to be in the game. In the future, if/when we get more complex bomb targets, the Disney Bomb would be a good way of giving American planes a bomb that can take out heavy targets without the potential Ground Forces balancing headache that could come with a Pe-8-equivalent huge conventional bomb. I'd also like to point out that while 6100m was the usual altitude for a Disney launch, there is no reason it couldn't be dropped lower than this. In real life, the drop height of the Disney had to be preset before they set out on their sortie, so if the implementation were to strive for realism, setting the drop height in the spawn screen would probably be required. A drop range of 1000m (i.e. 3-4km; 4-5km; 5-6km) seems reasonable, probably with a lower limit of ~3000m, since the bomb would be no better than a 500lb GP bomb (arguably worse) when dropped from below that altitude. This would introduce an element of planning ahead for the player, while also giving enough leeway that the weapon is practical and changes in plan can be made.

 

The reason 6100m was the chosen altitude was that above that height, increased drop altitude has negligible effects on the bomb's impact velocity, while below, the bombers would be more vulnerable to flak and their bombs less likely to penetrate as deeply. Logically, the Eighth Air Force chose to release their bombs as high as they could gain an advantage from, which coupled with the rocket boost is why it had such a high impact velocity despite being a relatively small bomb. Lower altitudes were possible, they'd just reduce the penetration -- and as a result damage dealt -- of the bomb; this could be implemented by reducing the damage done to targets up to a certain limit dependent on how high the bomber is. Against a naval target, for instance a carrier, one Disney might be sufficient to sink the target when dropped from 5000-6100m, whereas at a lower altitude like 3000m, two might be required to do the same level of damage. This provides bombers an additional incentive to climb with their bombs, and might make Disneys a valuable anti-Airfield weapon, since a B-17 dropping both of its Disneys from 6100m would be sure to deal a heavy blow to the enemy base. All that said, though there are certain niches the Disney Bomb could fill in the game as it is, this is a suggestion that looks forward to the kind of bomb targets we might have a few years from now and responds with a type of bomb that might become very useful in that event.

 

I hope you like this bizarre weapon, and I look forward to hearing from you in the comments! 

 

More Pictures:

 

Spoiler

 

A B-17G with Disney Bombs.

 

As above.

 

The same plane.

 

The same B-17 in flight.

 

As above.

 

A closeup of the same plane.

 

A Disney Bomb just after release over IJmuiden.

 

A technical drawing of the Disney Bomb.

 

Above: Officers pose with a Disney Bomb; Below: a Disney mounted on a B-17.

 

The poster for Disney's "Victory Through Air Power", which inspired the bomb.

 

A Disney Bomb being loaded onto a B-17.

 

A Disney Bomb underneath a B-17's wing.

 

A Disney-equipped B-17 in flight.

 

A bomb plot from Project Ruby.

 

A French technical drawing of the Disney Bomb.

 

 

 

Videos On The Bomb:

 

Spoiler

 

Walt Disney's "Victory Through Air Power", the inspiration for the bomb. The part with rocket bomb is around 57:15-58:00.

 

Period footage of B-17s being loaded with, carrying, and dropping the Disney Bomb.

 

A segment from the History Channel on the Disney Bomb.

 

 

Sources:

 

"Report of the Air Proving Ground Command, Eglin Field, Florida: Comparative Test of the Effectiveness of Large Bombs Against Reinforced Concrete Structures (Anglo-American Bomb Tests Project "Ruby")" (PDF version of the American report on the results of Project Ruby, available here)

"Weapons of the Eighth Air Force", by Frederick A. Johnsen (available online here)

"The Bomber Aircrew Experience: Dealing Out Punishment from the Air", by Philip Kaplan (available online here)

https://en.wikipedia.org/wiki/Disney_bomb

https://b17flyingfortress.de/en/details/bombentypen-bombenzielgeraet/ 

http://www.americanairmuseum.com/unit/169 (Page on the 94th Combat Bomb Wing, mentioning their part in the February 1945 Disney Bomb sortie)

http://www.sirbarneswallis.com/Bombs.htm (Disney Bomb mentioned only briefly)

https://en.wikipedia.org/wiki/Shellite_(explosive)

Edited November 1, 2019 by Zombificus
Edited poll to comply with the guidelines.

[SAUBER_KH7 3,294]

Open for Discussion.

 

I edited the poll to comply with the guidelines. All poll questions must include a "No" vote to remain fair and unbiased. This is due to the fact that the polling system requires members to vote for each question. Not just one or two.

 

Quote

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Quoted from:

 

Edited November 1, 2019 by SAUBER_KH7

[[email protected] 881]

all the those bombers should get it +1

[Jamaroo 231]

we do need more varied ordanance in the game. almost everything aside the FritzX and the 4000Lbs 'Cookie' is very bland and generic to each nation in terms of bombs, it would be nice to see a whole heap of aircraft get all sorts of wonderful weapons like this to add some spice to gameplay (like the Grand Slam and such)

 

+1 from me  

[Milocat 3,402]

This would be a fun weapon to see in the game, although I'm not sure how useful it would be.

[Solarmod 761]

I’d like to see more powered and guided bombs in game, maybe reworking the controls as well, I have difficulty using the Fritz-X and the AGMs. +1 from me!

[Deathbringer007 115]

I'll take it.

[Z3r0_ 3,770]

The main issue I see with this weapon (and other ground-penetrating bombs of this sort, i.e. the Grand Slam) is that there aren't any suitable targets for this thing in-game.  Bombing mechanics would need to be reworked and new targets conceived to give this any use over just picking the biggest bomb your plane can carry and using that instead (i.e. U-Boat pens on the Norway and Bolougne-Sur-Mer maps)

[Cpt_Bel_V 1,936]

Exactly why i said no,... 

 

This is because it will break(again) the bombing payload Meta. 

 

Yes something should be done for bombers, but adding bombs with no use or way to OP in certain case,... 

It's clearly not the way. 

 

I think it's better to upgrade the rewards to fly in formations(bombers themselves activity SL and RP) , and cover bomber (fighter with bombers bonuses in SL or RP for every thing your bombers are realizing assist for air kills, % for bombing), this will intimidate ennemy fighters to come unrivaled.

[Sarin 2,312]

With the addition of large ships, I believe this should be reconsidered. Disney Bomb's shorter time to impact would give US stand-off capabilities in naval battles similar to German Fritz X without having to implement, from the balance standpoint problematic, weapons like LBD Gargoyle, Hs 293 or even ASM-N-2 Bat.