Issue 50

A. Kakaliagos et alii, Frattura ed Integrità Strutturale, 50 (2019) 481-496; DOI: 10.3221/IGF-ESIS.50.40 485 1.5 m above ground in order to reflect historical reports (Table 4). It was reported that the Ottoman combat engineers had constructed a prepared position with a ditch protecting the gun crew having thus potentially placed the gun on an elevated ramp of soil and gravel (Phrantzes [6], Chalkokondyles [2]). According to Doukas [4], on January 1453, Orban executed full-scale fire testing of the Bombard at Sultan’s Palace in Adrianople with Sultan Mehmet present. Herein, a maximum range of 1 mile was reported which corresponds to 1,479 m, based on Agrippa’s Imperial Roman Mile. This result corresponds to the numerically evaluated gun range at 12 degrees cannon elevation (Table 4). Admittedly, with increasing gun elevation, corresponding range can be increased, however, at 12 degrees gun elevation the maximum effort for the construction of an elevated earth ramp is typically reached, requiring the construction of a 2 m high well compacted earth ramp with associated heavy fixed supports necessary to nail the gun in position and absorb bombard recoil. This reflects the maximum effort siege engineers could deliver. ௉ ൌ 0.393 ஺ ஺ ሺ ሻ ଶ ଶ (2) ஺ ሺ ሻ ൌ 0.7229 ହ െ 3.3061 ସ ൅ 4.9596 ଷ െ 2.6087 ଶ ൅ 0.558 ൅ 0.4485 (3) Cannon elevation Maximum ordinate Range Impact velocity on ground Arrival time on ground (deg) (m) (m) (m/sec) (sec) 5 18.41 744 180.43 3.794 8 43.18 1,096 166.65 5.876 10 65.04 1,306 159.28 7.227 Gun in firing position 12 90.79 1,498 153.12 8.550 Table 4 : Orban’s gun ballistics. Bombardment of Constantinople inner walls The bombardment of the Constantinople Theodosian Walls by the great cannon of Orban is hereby treated as a full-scale experiment and is numerically reproduced deploying Structural Mechanics. A ballistic scenario has been adopted in order to check Orban’s gun bombarding effect on Constantinople Inner Walls on April 24, 1453, as reported by Iskanter [5], who was an eyewitness of the historical events. This procedure was necessary in order to check and verify both muzzle velocity and the R factor, reflecting the pressure rise in the gunpowder chamber (Eq.(1)). Securing R, would lead subsequently to an assessment of the resulting stress situation in the gunpowder chamber. As reported in the Russian Chronicle of Nestor Iskanter, on April 24, 1453, Orban’s gun fired twice on the Inner Wall (Iskanter [5]). Following the first shot the Inner Wall started tilting, whereby, after the second shot a large portion of the wall collapsed. Herein, the cannonball opened a gap in the wall with the total height of the breach, measured from the ramparts, at 5 fathoms (9.15 m) approximately. Iskanter scenario was reconstructed analytically. For this purpose, the canon was placed at a distance of 500 m from the Inner Walls . The elite Condottieri force led by Giovanni Giustiniani Longo (Genova 1418-1453 Chios) was positioned facing Orban’s gun, at the Mesotechion Wall portion of the Theodosian Walls and at the Saint Romanos Gate. The selected gun position was outside the range of Giustiniani’s Genoese Crossbowmen, which was estimated at 400 yards from the Outer Wall ramparts (Fig.1). In general, Genoese Crossbowmen were considered as the most formidable elite unit of the Era, capable of firing up to 10-12 shots per minute with armor piercing darts, capable of penetrating all types of armor of the Late Medieval Period. Due to this fact, the decision to place the gun outside the range of this weapon but close enough to maintain line of sight to the Wall, was justified. According to historical records the Ottoman trenches were at very close distance from the Walls (Chalkokondyles [2]). The Ottoman bombard crew, although close to the Walls, could only see the upper section of the Inner Wall, as the line of sight to the lower portion of the Inner Wall was blocked by the Outer Wall Towers and the Paratechion ramparts. A target was selected which still could be spotted from the gun crew (Fig.1). Using the computer model presented previously, the gun “fired” with the muzzle velocity at 216 m/sec. Gun elevation was selected as input variable and several trial shots on the Wall were executed in order to identify the appropriate gun elevation adequate to hit the target. There was a very delicate balance in selecting the appropriate gun elevation. The cannonball was cruising at a very low altitude over the Outer Wall ramparts with high probability to hit the Outer Wall instead of the target or shoot over the Inner Wall ramparts.