B-29 Grand Slam Bomb WWII Secret Project Story

the intent of this video is to review the characteristics of the World War II blockbusting tall boy and Grand Slam bombs we will also clear up the controversy regarding the bomb speed at Target impact and plan B-29 usage over Japan the British specifically developed large blockbusting bombs to destroy German hardened targets not readily susceptible to Conventional bombing these included Bridges U-Boat pens V2 rocket sites and battleships these bombs would burrow into the ground prior to detonation the bombs explosion would cause a mini earthquake the earthquake Shockwave would reduce the structural Integrity of the target these bombs were often referred to as earthquake bombs this image from a Declassified September 1945 U.S Navy bomb disposal document titled bomb and fuses pyrotechnics illustrates a size comparison between the Grand Slam tall boy and a human all of the images in this video are Declassified a cross-section of the bomb is shown in this image the bomb's explosive fill occupies this volume the bomb's tail Helix stabilizing fins will induce a spinning force on the bomb tall boy's spin rate is 300 RPMs whereas Grand Slam spin rate is 60 RPMs the tall boy and Grand Slam bombs are shown in this picture in reference to other British bombs geometry and characteristics of the tall boy bomb are in this image the 12 000 pound class tall boy bomb is designated T10 by the US Army it is 21 feet in length and has a body diameter of three feet two inches the bomb steel casing wall thickness is 1.2 inches the explosive fill is either torpex or Tritonal depending on the country of manufacture the explosive fill of the US version of the tall boy equated to 5 100 pounds of Tritonal as shown in this page from a September 1945 National Defense research committee document titled weapons data fire impact explosion the British filled their tall boys and Grand Slams with torpex as discussed in the remark section both Tritonal and torpex have greater relative power as compared to TNT as shown on this table from a September 1945 Office of the chief of ordinance document titled terminal ballistics data volume 3. torpax has a 22.5 percent higher air burst Peak pressure than TNT while Tritonal has a 12.5 percent higher airburst Peak pressure than TNT the U.S mounted bombs are suspended by two straps this image shows a Lancaster suspension buckles dangling after a grand slam release this image shows a Grand Slam in the Bombay of a B-29 the bomb fills both bombays and the bomber's radar was relocated from between the bombays to between the nose gear wheel well and the forward Bombay exterior view of the b-29s Grand Slam bomb captive slings this close-up image shows the linked chain suspension slings and the weapons Bay bomb stabilizing brackets the b-29's Bombay doors were trim contoured to accept the Grand Slam bomb extending into the Airstream like shown in this image and can be seen more clearly in this image with the Palm Bay doors open the bomb will be deployed from modified very heavy bombers it is a deep penetration bomb but not considered armor or concrete piercing its destructive power comes from its Earth shock waves the tall boy is similar to the Grand Slam just different in size deep penetration usage of the bombs is also discussed on this page from a 1946 Naval Ordnance systems command document titled British explosive Ordnance the bomb is not designed for armor or concrete piercing but rather its destructive power comes from the heavy Earth shock waves the bombs are carried by specially designed Lancaster bombers there were 854 tall boys dropped in World War II this chart describes the characteristics of the larger Grand Slam bomb all the parameters that apply to the tallboy bomb also apply to the Grand Slam bomb except the weights and geometries are upsized and the spin rate is lower at 60 RPMs the 22 000 pound bomb is U.S army designated as a t-14 it is 25 feet 5 inches in length and 3 feet 10 inches in diameter the Grand Slam steel casing gauge is thicker than the tall boys at 1.75 inches and it contains 9440 pounds of Tritonal there were 41 Grand Slams dropped in World War II so how effective were tall boys and Grand Slams operationally this chart describes the World War II combat effectiveness of various bombs against concrete structures from a June 1945 Army Air Force evaluation board document titled the relative effectiveness of various bombs and fuses operational data indicates that semi-armor piercing bombs of one thousand pound weight class or less have been ineffective against reinforced concrete structures at thicknesses of 5 feet or greater the only bomb found to be effective against U-Boat pens is a 12 000 pound tall boys a u-bolt pens roof consists of thick reinforced concrete as shown in this image this image and this image an example of a tall boy attack is described the breast U-Boat pens was attacked by RAF lancasters with tallboy loadouts a total of 26 tall boys were dropped nine of the tall boys hit the roof of the U-Boat pens no difference in bomb Effectiveness was found for fused at Nation train time delay of one half to 11 seconds the roof varied in thickness between 11 and 18 feet roof holes were observed in three of the nine hits four of the nine hits produce large craters and interior scabbing two tall boys landed on the edge of the pens and caused no damage scabbing damage is described on this page from the reference shown earlier scabbing damage occurs when the bomb shock wave is reflected off of the concrete slabs back face a Shockwave will eject concrete on the far side of the bomb's impact side an interior scabbing crater will form a hole in the thick concrete slab is formed when the impact crater and the scabbing crater merge this image shows the interior damage from the breast tallboy raid this image shows the exterior damage from one of the tall boy bombs the report goes on to state that general purpose bombs are not effective against German U-Boat pens other than forming small craters in the roof only tall boy class bombs and larger should be adopted on concrete structures like u-bo pans the recommended bomb sizes in few settings for the destruction of various concrete fortifications is shown on this page so what is the speed of a tall boy and Grand Slam bomb at impact there's some internet debate regarding this issue specifically do they attain supersonic speeds and if so under what conditions a sonic speed is attained when an object travels at the speed of sound an object traveling at a Sonic Speed equates to a velocity of Mach 1. the speed of sound at sea level equates to 1116.4 feet per second as defined in this United Technologies aeronautical handbook 1116 feet per second equates to 761 miles per hour or 1225 kilometers per hour an object is traveling at supersonic speed if its velocity exceeds a sonic speed or is faster than Mach 1. this chart outlines the strike speed and strike angle of the tall boy bomb the chart's footnotes are on this page strike speed error will not exceed 15 percent and impact angle four percent the x-axis is a bombs release altitude from 0 to 32 000 feet the left y-axis is the aircraft's true ground speed at Bomb release from 0 to 500 miles per hour the solid family of Curves in the chart body is the strike speed of the bomb from 300 to 1 350 feet per second the dash family of Curves in the chart body is a strike angle or obliquity angle from 5 to 50 degrees a zero strike angle would indicate the bomb is perpendicular at Target contact the bomber command Museum indicates that tall boys were released at an aircraft speed of 200 miles per hour as shown in the snippet from their website page for example the speed of a tall boy Target contact can be extracted from the chart by assuming a Lancaster bomber released a tall boy at a ground speed of 200 miles per hour at an altitude of 15 000 feet the interception of these parameters is at this point on the chart interpolating between the 1000 foot per second and 1100 foot per second curves yields a tall boy ground contact speed of 1010 foot per second at a strike angle of 16 degrees the bomb will contact the ground at an angle of 16 degrees from the normal Direction at a speed of Mach 0.90 similar strike speed and impact angle plots are shown for both the Grand Slam and a typical 500 pound general purpose bomb for reference most of the bombs dropped by the U.S 8th Army Air Force over german-occupied Europe for general purpose demolition bombs a cross-section of the 500 pound an- m64 is shown on this image for reference its steel casing is only .30 inches thick the strike speed for the tall boy Grand Slam and the 500 pound general purpose bomb as a function of altitude was re-plotted for ease of discussion the strike speed was converted from foot per second to Mach number the release speed is defined at 200 miles per hour the x-axis is the release altitude and feed the y-axis is the bomb strike speed in Mach number the family of Curves represent the tall boy or grand slam and the an-m64 500 pound general purpose bomb the tall boy and Grand Slam impact speeds are virtually identical for a 200 mile per hour release speed so they are represented by a single line the strike velocity at the speed of sound or Mach 1 is represented by this horizontal dotted line if the tall boy or grand slam bomb is released at an altitude of 18 900 feet or less the bomb strike speed will be less than Mach 1 or within the subsonic range if a tall boy or grand slam bomb is released at an altitude greater than 18 900 feet the bomb strike speed will be greater than Mach 1 or supersonic the an-m64 bomb never attained Sonic Speed it always contacts a Target at a subsonic speed the angle at strike impact is important to make sure the bomb does not Ricochet off the target this is extremely important when attacking concrete targets like U-Boat pins this chart outlines a Ricochet and penetration limits for various bomb types striking various mediums the x-axis is the bomb's impact velocity in feet per second the y-axis is a bomb's angle of impact from 0 to 90 degrees a 90 degree impact would be perpendicular to the Target as shaded in this view the thick bands in the body of the chart are for water soil and concrete the charts annotations and notes are shown here no Ricochet occurs if the bomb strike angle is above the band The top part of the band is represented by bombs with sharp noses long slender bodies or low densities this criteria more or less applies to the tall boy and Grand Slams no Ricochet is expected if the combination of strike speed and angle is above this band for a tall boy dropped at 18 900 feet in altitude the speed on impact equates to Mach 1 or 1116 feet per second the angle of obliquity is 15 degrees we will need to plot these parameters on the Ricochet curve the point resides within the no Ricochet Zone given this data the bomb will penetrate the target it would seem to make sense the Germans would want to construct concrete sloping ropes on their U-Boat pants to take advantage of the bomb's Ricochet effect so did B-29 bombers deploy either the tall boy or Grand Slam in World War II 21st bomber command studied the feasibility of tallboy and Grand Slam operational usage against Japan as discussed on this May 5th 1945 headquarters of the 20th Air Force Weekly Newsletter three officers were sent to Europe to study British experiences it was recommended that the bombs be available for usage as soon as possible a limited number of b-29s would be adopted to carry the bombs against Japan targets would be identified initial test results were discussed in this follow-up June 5th Weekly Newsletter a B-29 can deploy a single tall boy no unusual flight issues not suitable for formation flying with mixed Loadout b-29s bombing accuracy is considered exceptionally good combat radii is reduced from 1500 miles to 1 350 miles this is due to aerodynamic drag from the Bombay door Gap after Bomb release bomber command was expecting the delivery of 100 grand slams and 500 tall boys from the British no later than September 1st 1945 as discussed on this June 23 1945 Weekly Newsletter the 15 tall boys in Grand Slam ready b-29s were also expected on September 1st 1945. the Bombay doors need modifications to meet water ditching goals the war ended before either tall boys or grand slams could be deployed over Japan you if you've enjoyed this video please consider commenting liking and or subscribing to the Channel World War II us bombers

Channel: WWII US Bombers

Views: 35,810

Keywords:

Id: OK3TEh_C95g

Length: 14min 4sec (844 seconds)

Published: Tue Jul 11 2023