Browsing by Author "Salt, John D."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Chip away everything that doesn't look like an elephant(The Operational Research Society, 2025-04-02) Salt, John D.This paper addresses the question of how conceptual models are created in a simulation modelling activity. Assuming an entity-based approach to simulation, some techniques for discovering good entity classes are considered, including personation. Also considered are the notations by which a conceptual model can be represented, and the modes of thought required for good conceptual modelling. Specifically excluded from consideration is the idea of applying a cut-and-dried method. The shortcomings of computers for conceptual modelling are remarked upon.Item Open Access A hundred years of tiny mortars(2022-07-07) Salt, John D.In 1915, Wilfred (later Sir Wilfred) Stokes serendipitously invented a trench mortar which set the pattern for medium and heavy mortars to this day. Stokes-Brandt mortars are smooth-bored, muzzle-loading, drop-fired weapons, with a system of variable charges (increments), and using the ground to absorb recoil. This presentation covers a rather different class of weapon which arose during the 1920s. These are trigger-fired, 37 to 52mm in calibre, with no charge system, described variously as light mortars, grenade dischargers, or misleadingly as “knee mortars”. A variety of design approaches is described, and evaluated in terms of throw-weight and range. The most efficient and successful designs seem to be the simplest. These tiny mortars were popular before World War 2, especially with Imperial Japan, but by the end of the war most major combatants had lost their enthusiasm for such weapons. Great Britain, unusually, retained a weapon in this class until quite recently. The current state of the art is represented by French and Chinese designs of captive-piston spigot mortar, which have enviable stealth characteristics. The author believes that it is still useful for an infantry platoon to have a light mortar capable of throwing a one-kilogram bomb to half a kilometre.Item Open Access Small arms, small data : small arms shooting accuracy and the small data problem(ISMOR, 2016-07-26) Salt, John D.This paper explores how small-arms aiming errors appear to vary with range. In particular it investigates the question of whether a “proximity effect” exists, reducing accuracy at close range. Data on small-arms hitting rates is sparse. The paper analyses nineteen sources of data, giving 83 data points; combat data is augmented with data from police shootings, range trials, OR models and qualification scores. The paper explains the assumptions made in order to compensate for gaps in the data, such as target size. Data points are reduced to a common basis of angular error, which would produce the observed hitting rate if shooting at a visible static rectangular target at the stated known range. This subsumes all errors normally included in ballistic error budgets, plus the uncertainty of target location if firing at targets not clearly visible. The data available indicates that the accuracy of small-arms fire decreases with proximity to the target, so that the hitting rate does not increase as much as would otherwise be expected at closer ranges. The effect seems to apply across different types of data source, weapon, and fire, up to about 100 metres. The paper discusses possible explanations for the effect: prevalence of close terrain in the combat sample, restricted visibility, targets reducing their exposure time close to the enemy, uncertainty as to true target position, psychological stress due to enemy proximity, and a transition to pointed rather than aimed shooting. Each may be a contributory factor, but it is tentatively concluded that a hastier shooting style arising from psychological stress provides most of the explanation. Finally the paper suggests some directions for future work, the most important of which is clearly to add to the data available on this subject.Item Open Access Thoughts on modelling supression (Presentation)(2017-07-18) Salt, John D.