ARTICLE IN PRESS HOSTED BY Available online at www.sciencedirect.com ScienceDirect Defence Technology ■■ (2015) ■■–■■ www.elsevier.com/locate/dt 1bs_bs_query Q2 The ballistic performance of the bombard Mons Meg 2bs_bs_query Q1 3bs_bs_query Ian LEWTAS, Rachael MCALISTER *, Adam WALLIS, Clive WOODLEY, Ian CULLIS 4bs_bs_query QinetiQ, Fort Halstead, Sevenoaks, Kent T N14 7BP, UK 5bs_bs_query Received 28 September 2015; revised 30 November 2015; accepted 1 December 2015 6bs_bs_query Available online 7bs_bs_query 8bs_bs_query Abstract 9bs_bs_query The bombard Mons Meg, located in Edinburgh Castle, with a diameter of 19 inches (48 cm), was one of the largest calibre cannons ever built. 10bs_bs_query Constructed in 1449 and presented to King James II of Scotland in 1454, Mons Meg was used in both military and ceremonial roles in Scotland 11 bs_bs_query until its barrel burst in 1680. This paper examines the history, internal, external and terminal ballistics of the cannon and its shot. The likely muzzle 12bs_bs_query velocity was estimated by varying the propellant type and the cannon profile was investigated to identify weak spots in the design that may have 13bs_bs_query led to its failure. Using the muzzle velocity calculated from the internal ballistics, simulations were performed with granite and sandstone shot for 14bs_bs_query varying launch angle and ground temperature. The likely trajectory and range of the cannonballs are described. The internal and external ballistics 15bs_bs_query informed the initial conditions of the terminal ballistic impact scenarios. The performance of the cannonball against both period and modern 16bs_bs_query targets, in the form of a pseudo-castle wall and a monolithic concrete target, respectively, were simulated and are presented and discussed. 17bs_bs_query © 2015 Production and hosting by Elsevier B.V. on behalf of China Ordnance Society. 18bs_bs_query Keywords: Analytical; Hydrocode; Muzzle velocity; Cannon barrel design; Trajectory; Castle brick target 19bs_bs_query 20bs_bs_query 1. Introduction that the first cannonball fired at the keep passed straight through 46bs_bs_query the wall and severed the hand of Margaret Douglas as she was 47bs_bs_query 21bs_bs_query As one of the larger and well documented surviving medi- drinking inside. 48bs_bs_query 22bs_bs_query eval cannons, Mons Meg stands in pride of place at Edinburgh Once retired from active military service she found a new 49bs_bs_query 23bs_bs_query Castle and in its history (Fig. 1). Constructed around 1449 in role as a display piece at Edinburgh Castle. However, on 30 50bs_bs_query 24bs_bs_query Mons, part of what is now modern day Belgium, at the request October 1680, to celebrate the visit of James Duke of York and 51bs_bs_query 25bs_bs_query of Duke Philip the Good of Burgundy [2], the bombard was Albany to Edinburgh, the barrel burst, effectively ending her 52bs_bs_query 26bs_bs_query intended as a wedding present to King James II of Scotland, operational life. 53bs_bs_query 27bs_bs_query who, in 1457 married Duke Philips’ great niece, Mary of This paper investigates and discusses the internal, external 54bs_bs_query 28bs_bs_query Gueldres. and terminal ballistics of the cannon. The internal ballistics 55bs_bs_query 29bs_bs_query Customs records date Mons Meg’s first arrival on Scottish 30bs_bs_query shores around 1457 [3], seemingly first taking place in battle at 31bs_bs_query the siege of Roxburgh Castle in 1460, although this is not yet 32bs_bs_query backed up in any way other than stories from the time [3]. The 33bs_bs_query earliest written record of her active role in service is during the 34bs_bs_query 10 day bombardment of Norham Castle in 1513 [3] during 35bs_bs_query which she is reported to have destroyed both the castle’s inner bs_bs_query 36 and outer wall. Her last use as a defensive weapon was during 56bs_bs_query 37bs_bs_query the Lang Siege 1571–73, after which she was only used for 38bs_bs_query ceremonial duties. 39bs_bs_query One of the most famous stories about the bombard was the 40bs_bs_query two month siege of Threave Castle by James II. The story goes 41bs_bs_query 42bs_bs_query 43bs_bs_query Peer review under responsibility of China Ordnance Society. + 44bs_bs_query * Corresponding author. Tel.: 44 1959514029. Fig. 1. Mons Meg at Edinburgh Castle. Licensed under creative commons 57bs_bs_query 45bs_bs_query E-mail address: [email protected] (R. McAlister). attribution-share alike 2.0 generic license [1]. 58bs_bs_query http://dx.doi.org/10.1016/j.dt.2015.12.001 2214-9147/© 2015 Production and hosting by Elsevier B.V. on behalf of China Ordnance Society. Please cite this article in press as: Ian Lewtas, Rachael McAlister, Adam Wallis, Clive Woodley, Ian Cullis, The ballistic performance of the bombard Mons Meg, Defence Technology (2015), doi: 10.1016/j.dt.2015.12.001 ARTICLE IN PRESS 2 I. Lewtas et al./Defence Technology ■■ (2015) ■■–■■ Table 1 bs_bs_query 59bs_bs_query calculates the likely muzzle velocity of the cannon and 100 Pressured produced by period black powder compositions [7]. 101bs_bs_query 60bs_bs_query analyses the possible reasons for the barrel bursting. The exter- Period Composition name Range of Average muzzle 102bs_bs_query 61bs_bs_query nal ballistics uses the results from the internal ballistics to −1 pressure/ velocity/(m·s ) 103bs_bs_query 62bs_bs_query analyse and predict the cannonball trajectory and likely final MPa 104bs_bs_query 63bs_bs_query velocity and impact angles. This is used to investigate its ter- 14th century John Arderne Feuerwerkbuch 44–51 328.6 105bs_bs_query 64bs_bs_query minal performance against modern targets and period, castle- 16th century Whitehorne 22–25 231.1 106bs_bs_query 65bs_bs_query type targets. 16th century Bruxelles 66–76 385.4 107bs_bs_query 66bs_bs_query 17th century British government Formula 92–105 425.3 108bs_bs_query 67bs_bs_query 2. The cannon 109bs_bs_query 68bs_bs_query Mons Meg is constructed of wrought iron, sometimes called 3. Internal ballistics 110 bs_bs_query 69bs_bs_query charcoal iron, a highly variable iron, both in chemical compo- 70bs_bs_query sition and slag content. However it is a very ductile metal and 3.1. Muzzle velocity 111 bs_bs_query 71bs_bs_query the levels of slag have made the iron extremely resistant to To calculate the muzzle velocity of Mons Meg, the analytical 112 bs_bs_query 72bs_bs_query corrosion [4]. It measures over 4 m in length, with a bore of code Proteus was used. Proteus is a 1 dimensional, lumped 113 bs_bs_query 73bs_bs_query 50 cm and weighing over 6000 kg [5], easily making it one of parameter code used to solve for combustion of gases and 114 bs_bs_query 74bs_bs_query the largest (by calibre) stone firing cannons in history. internal pressures; it is similar to IBHVG2 [8], and internal 115 bs_bs_query 75bs_bs_query It is divided into 2 distinct parts, the powder chamber, and studies have shown the predictions of both codes to be 116 bs_bs_query 76bs_bs_query the barrel. The powder chamber measures 1.16 m in length, and comparable. 117 bs_bs_query 77bs_bs_query varies from 0.59 to 0.53 m in diameter (Fig. 2). It is likely that There were three likely black powder compositions in use 118 bs_bs_query 78bs_bs_query the powder chamber is constructed from one billet of iron during Mons Meg’s operation lifetime and one from when the 119 bs_bs_query 79bs_bs_query which has been hammer-beaten on a mandrel to achieve the barrel burst, each with a different range of pressure produced. 120bs_bs_query 80bs_bs_query correct inner dimensions. The barrel measures 2.88 m in length Proteus matched these shot pressures to calculate the muzzle 121bs_bs_query 81bs_bs_query externally, and varies from 0.63–0.75 m in diameter. It is con- velocities. The results shown in Table 1 average the propellant 122bs_bs_query 82bs_bs_query structed from 25 staves running the length of the barrel which mass and pressure range, whilst assuming a 160 kg granite 123bs_bs_query 83bs_bs_query are covered and held in place by 33 hoops. These would have cannon ball, to produce a single muzzle velocity for each 124bs_bs_query 84bs_bs_query been heated in a furnace and placed over the staves, as these composition. 125bs_bs_query 85bs_bs_query cooled they would tighten to hold the barrel together and fasten As there is no definite source for which type of powder was 126bs_bs_query 86bs_bs_query the staves to the powder chamber. used in Mons Meg, an average of the 14th and 16th century 127bs_bs_query 87bs_bs_query Mons Meg fired cannonballs roughly 490 mm in diameter. powders (its operational timespan) was used as the expected 128bs_bs_query 88bs_bs_query During Mons Meg’s operation lifetime in the 15th and 16th muzzle velocity of the cannon, 315.0 m/s. This value was taken 129bs_bs_query 89bs_bs_query centuries, iron shot was not available and the cannonballs were forward to be used in the external ballistics section. 130bs_bs_query 90bs_bs_query made from local stone. There are records [7] which indicate The above value of 315.0 m/s was reached after several 131bs_bs_query 91bs_bs_query both sandstone and granite shot was used to give mass ranges refinements to the model. An initial value of 319.1 m/s was 132bs_bs_query 92bs_bs_query of 130–140 kg and 160–170 kg for the different stone, previously calculated and used in both the external and terminal 133bs_bs_query 93bs_bs_query respectively. ballistics work as the research was running in close to parallel 134bs_bs_query 94bs_bs_query Black powder was used as the propellant charge for