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BT Bombentorpedo for Ar 234 C-3 and Me 163B

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Piotrek1:
Hello everyone,
I thought it would be good to have this type of weaponry for such aircraft as Me-262, Ar 234 C-3, Me 163B or Fw-190F-8 (or F-9), I hope that maybe one day in the future the data from this request will be useful for someone .
underneath is a collection of various data found on the web:

BT 700 Bomb-Torpedo- Data*

Dimensions
Length 3.50 m 11 ft 5 in
Diameter 42.6 cm 16 in
Tailfin span 1.10 m 3 ft 7 in

Weights
Weight, without rocket unit 780 kg 1,720 lb
Explosive weight 330 kg 728 lb

*Of interest is that an unpowered version of the BT 700 developed for use against naval vessels and merchant ships and released from the Fw 190, was intended not to achieve a direct hit but to first travel some 60-80m (200-260ft) underwater before impact. The triple tail fins stabilize the missile during descent and were designed to separate upon striking the water. Two types of fuses were fitted, one of which was activated during the missile’s underwater path and the other in the event of an unintentional direct impact above the water line. The BT 700 C2 had an overall length of 3.3358 m (11 ft), maximum body diameter 45.6 cm (18 in) and weight 700 kg (1,543 lb), of which 375 kg (827 lb) was the high-explosive filling.

BT 1000 bomb-Torpedo -Data

Dimensions
Length 4.24 m 13 ft 11 in
Diameter 48 cm 19 in
Tailfin span 1.30 m 4 ft 3 in

Weights
Weight, without rocket unit 1,180 kg 2,601 lb
Explosive weight 710 kg 1,565 lb

http://michaelhiske.de/Wehrmacht/Luft/Luft/LDV_4200/SERIE_S/Blatt_03.HTM    (de)
http://ww2data.blogspot.com/2019/05/german-explosive-ordnance-concrete.html

German BT (Torpedo/Bomb)
BT Bombentorpedo:
Designed to replace the conventional torpedoes, the BT Bombentorpedo-series bombs could be launched from a Schnellbomber flying at high speed in dive of 20 degrees from height of 200m, against ships located 2,800 m away.

Developed, built and tested had been:
BT 200 / BT 400 / BT 700a / BT 700 b / BT 1000 / BT 1400 / BT 1850

It is reported that some BT 400 and BT 1400 had been in service. Beginning 1945 the developement had been stopped.
 
It is reported that FW-190F-8/R-16 equiped with BT-700 flew night attacks ageinst British ships from Stavanger airfield/Norway.However this claim can not be substantiated.

Early 1943 the departement "Technische Luftrüstung" led by Dr. Benecke proposed a new type Torpedo and developed and tested it at the Researchinstitute "Graf Zeppelin. The so called "BombenTorpedo" is unpowered Torpedo which was dropped in a low angle. This new developed Torpedo could be build in shortest time, much cheaper and resource saving. No expensive PowerUnit was needed.

--- Quote ---Except for some plans, neither Pi-Mz nor Unterwasserzuender were used in BTs. The Pi-MZ was actually found inappropriate for the BT and could not be used at all, while the Uw.Z. was not even tested. Operational BT models used standard delayed action electrical bomb fuze, mounted on a fuselage side. Generally not hydrostatic, but time, distance and proximity fuzes were considered usable.
There's no physical possibility for a BT dropped from 200 m in a 20 degrees dive to cover 2800 m, especially that the underwater trajectory was only 50-100 m long - a BT dropped this way at 600 km/h would enter the water after after some 450 m of flight. BTs were to be dropped from a climb, not dive.
Only bigger BTs (1000+) were made from welded steel plates, smaller had cast warheads.
The BT 1000 RS did not actually reach 960 km/h, this value refers to max. velocity at which usual BT could be dropped.
I don't know if BT 1850s were used against Remagen bridge, but smaller BTs were to be used (and probably were indeed) by III./KG 200 against sea targets in northern Europe.
--- End quote ---

--- Quote ---BT (Bomben Torpedo)

General: The aircraft torpedo is an expensive, complicated weapon.  The proportion of explosive weigh is low.  Mass production is lengthy and expensive.  In addition, present day performance of torpedo engines limit the speed and range of the projectile.  Both of these items are essentials for accuracy and safety from anti-aircraft fire.

A relatively simple weapon would result were the torpedo engine and the control gear omitted.  If this simplified weapon were launched so that the greater portion of the distance to the target was covered through the air, as with an ordinary bomb, the initial speed of the launch would be retained over nearly all the range.  The projectile would enter the water just short of the target and carry on in the direction of its flight in air by reason of its momentum in the same was as does a torpedo.  To prevent it from going too deep before detonation, a relatively flat angle of entry into the water is necessary.

Such a weapon was developed in Germany during the closing months of the war, and it was called the Bomben Torpedo.  It combines the characteristics of the bomb to travel a long distance in a short time interval with the characteristics of a torpedo in that underwater travel eliminates range errors.

Details:
The BT was developed in four sizes: 200kg, 400kg, 700kg, and the 1400kg.  They all incorporated the same general shape and construction, and were entirely of steel.  They were constructed in three pieces; the warhead (two sections) and the tail section.  The forward section of the warhead was in the shape of a truncated cone, and the after section of the warhead was cylindrical.  The transverse fuze pocket was located in the cylindrical section just aft the point where the two sections were welded together.  The suspension lug T-type, was secured to the warhead just forward of this weld at the center of gravity.

Tail Section: The tail section was also in the shape of a truncated cone.  There were three very large fins placed 120 degree apart at the after end of the section.  This type of tail provided excellent stability for the bomb while it was in the air.  The tail section was secured to the after section of the warhead in such a manner that when the missile struck the water, it was jettisoned.

Early in the experiments, a BT 1000 was worked on and this missile had a rocket motor inside the tail section.  This idea was soon dropped as it proved impractical for the missile.


Underwater Behavior: The bomb must in no event ricochet off the water, not even in flat angles of entry, but must continue without deviation of its path of entry.

It is known that with ogival noses, as seen in the illustration of the BT 1400, a bomb will ricochet off the water when it strikes at a flat angle.  By using a flat nose, as seen in the illustration of the BT 700, or better yet by using a spoiler plate, this ricochet at flat angles is definitely avoided.  The front surface of the spoiler plate is made in the form of a section of a sphere of radius, equivalent to the distance between the surface of the spoiler plate and the bomb's center of gravity.  As the flow of force is practically perpendicular to the upper surface of the body when it is awash, the resulting flow of force must go through the center of gravity and thus it causes no turning moment.

A spoiler plate with the same diameter as the bomb, however, has a high water drag.  The ideal situation is to have the size of the plate less than the greatest caliber of the bomb body and so shaped that only the spoiler plate and no other part strikes the surface of the water at flat angles of entry.

Source: German Explosive Ordnance Vol. 1: Bombs, Rockets, Grenades, Mines, Fuzes & Igniters
--- End quote ---

Aircrafts:

Me-262 Schnellbomber,Ar 234 C-3, Me 163B with 2 Torpedo Bomb's type BT1000, Bf-110 (for test only?)

Ar 234 B-2 was also considered in the summer of 1944 for carrying two BT 400 under the nacelles (plus Magirusbombe gun pod under the fuselage).

The Fw 190 F-8/U2 torpedo bomber was fitted with an ETC 503 bomb rack under each wing and a centerline mounted ETC 504. The U2 was also equipped with the TSA 2 A weapons sighting system that improved the U2's ability to attack seaborne targets with a 1,543 lb (700 kg) BT 700.

The Fw 190 F-8/U3 heavy torpedo bomber was outfitted with an ETC 502, which allowed it to carry one BT-1400 heavy torpedo (3,086 lb/1400 kg). Owing to the size of the torpedo, the U3's tail gear needed to be lengthened. The U3 also was fitted with the 2,000 PS BMW 801S engine, and the broader-chord vertical tail from the Ta 152

Fw 190F-8/U2 - torpedo plane with two underwing ETC 503 racks or under-fuselage mounted ETC 504 (previously ETC 501) bomb rack. The plane was equipped with a special sight system, TSA 2A (Tiefsturzangle 2A) for precise aerial torpedo BT (Bombentorpedo) aiming. Using this torpedo it was possible to attack targets from a higher altitude and from a higher angle than in the case of an ordinary aerial torpedo LT (Lufttorpedo). It was planned to use two BT 400 or one BT 700 torpedo. Other armament was reduced to two fuselage mounted MG 131 machine guns. A small number of these planes were in service with 11./KG200.

Fw 190 F-8/U2 (renamed into Fw-190 F-8/R15 in the end of 1944) had to carry two BT 400 under the wings. A handful of these aircraft was actiually delivered to III./KG 200 till April 1945.

Fw 190F-8/U3 - torpedo plane adapted for transportation of the heavy BT 1400 torpedo on an under-fuselage mounted ETC 502 pylon designed specially for this in TWP Gotenhafen-Hexengrund (see the section "Operational use"). His plane had a lengthened tail wheel strut to eliminate the possibility of striking the ground with the torpedo. The plane was equipped with the TSA 2 sight system coupled with a FuG 101 radio altimeter. This version was powered by the more powerful 2000 hp (1470 kW) BMW 801 TS engine. The Ta 152 tail was also mounted.



Me 163B with BT 700 Bomb-Torpedo
Only recently accessible files of the AVA Göttingen contained photographs and a number of file notations that described measurements of special urgency made on the Me 163B model equipped with two underwing BT 1000 Bombentorpedos (bomb-torpedoes). From the documents of the Messerschmitt Project Office in Oberammergau and the AVA of 18th February 1944, it is evident that at the wish of Prof Willi Messerschmitt, wing-tunnel measurements of the Me 163B with underwing loads were to be urgently conducted, as the rocket-propelled aircraft was scheduled to be used at an early date against ship targets. The documents were annotated as being of the highest urgency. From various AVA reports, it is evident that Dipl-Ing Hubert of Messerschmitt Project Office was placed in charge of this work. In a communication from the Junkers Flugzeugwerke dated 22nd september 1944 to the AVA, it is mentioned that measurements made in the Junkers win-tunnel would be accepted, where information from the Junkerswerke concerned measurements made on a Messerschmitt fighter with suspended underwing loads. These measurements were conducted by Junkers on an Me 163B with two BT 700s - smaller than the BT 1000, and which enabled the Me 163B to take off on its normal wheeled dolly. As far as is know, take-off trials were made at Junkers in December 1944 with BT mockups, but no documentation on their progress is to hand. Since a great deal has already been published concerning the Me 163B, other than its use as an operational fighter described above, mention will only be made here of the BT 700 and the BT 1000.

There BT-designated air-launched missiles (where the figures following denotes the weight) used against ground and seaborne targets were developed by the former Forschungsanstalt (Research Institute) Graf Zeppeling or FGZ in Stuttgart-Ruit.
The BT missiles were manufactured partly at the Tripel Werke factories in Mohnsheim/Elsass. Their high explosive contents were furnished by the Luft-Munitionsanstalt (Air Ammunition Institute) in Boodstedt, the propulsion unit consisting of a powerful Rheinmetall-Borsig solid-propellant rocket motor. Release of the BT missile was to take place by the so-called ‘schleuderwurf’ (catapult-release) method with the aid of a Reflexvisier (reflex bombsight) or Revi specially developed for it. Depending on the attack altitude, the release distance was up to 3,000m (9,840ft).

--- Quote ---in 1992 they Discover in Aerodynamische Versuch Anstalt (AVA) at Göttingen several Files notes.
of Windchannel Model of a Me 163B with 2 Torpedo Bomb's type BT1000.

one note was of a conference between engineer Hubert (from Messerschmitt) and professor Betz from AVA
"its necessary to check the Stability Me 163B with BT1000 in a Windchannel Test"
"the soon use of Plane against Shiptarget deepens of that Test Result"
"The Model is Ready middle of February for Test of 2 Day duration.
"A longer Test has to be interrupt, because of not urgent." signature mister Hildenbrand.
the note is date 9 February 1944.
more Files notes and Photos show this Test was made

A letter from 22. September 1944 from Junkers "Flugzeugwerke und Motorenwerke" to AVA
say they receive the test result from February

the BT1000 Bomb Torpedo's
1000 kg Bomb rocket for land and sea Target
from Research's institute Graf Zeppelin in Stuttgart-Ruit

the Pilot or Bomber used a special developed "Reflexvisier" from Drop height depend the BT1000 fly 3000 Meter far
the BT1000 was Propelled by Solid rocket build by company "Rheinmetall"

Source: Flug Revue April 1992 page 49
Source: Picture Stüdienbüro für Luftfahrt, Feiler
--- End quote ---
http://www.secretprojects.co.uk/forum/index.php/topic,2409.msg21374.html#msg21374

Best regards,
Piotrek

Dreamk:
Well I m made the meshes for these torpedoes when i created the Air-launched Torpedo pack (and if I remember well the meshes are in fact part of the upload, but without the java) but did not finalize them as the basis for writing the java was lacking and contradictory.

The BT torpedoes are a problem as the only fact agreed about them is their shape and dimensions (some mock-up test samples have survived in museum in Poland) but nobody really agrees about how they were intended to work at the end of the development curve: the original idea of a rocket bomb torpedo was soon dropped as quite unfit to the intended aim (in fact the bomb would explode when  touching water instead of going on under water till the target) then the development went towards a regular torpedo but dropped at high speed and high altitude, then towards a skip-bomb. What the US succeeded to do with the 3.5" and 5" rockets, initially designed as an anti submarine weapon, striking water at distance from a submarine and continuing its trajectory underwater towards the objective was possible due to the small size and the shape of the projectile head. The size of the BT torpedo was in one of the sources of its failure. The flat nose of the BT torpedo was a logical contradiction - a flat nose is aimed at preventing ricochet for depth bombs, causing such a drag that such a bomb can only sink, not change direction towards a precise azimuth and go on running towards a target  - for a torpedo such a nose is a cause of failure. The gliding torpedoes, propelled or not, were a more logical approach.

If

Piotrek1:
Hello Dreamk, Thank you for your comprehensive explanation 8). Is there any technical solution to this problem that would allow us to use this weapon in our game?
Best regards,
Piotrek

singüe:
With the short range of the komet it seems a silly atempt to waste resources and time. Im I wrong?

Piotrek1:
Hello singüe, maybe you are right, unfortunately I am not a competent person to comment on this topic :-[, I would like to ask the experts to speak...I'm sure we have a few 8).
Best regards,
Piotrek

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