Mott Formula
Definition
An empirical relationship, derived from wartime UK research by N.F. Mott, predicting the statistical distribution of fragment masses from a metal casing cylindrical bomb; used forensically to characterise device casing geometry from recovered fragment size distributions.
- Originator
- N.F. Mott
- Origin
- Wartime UK research
- Predicts
- Statistical distribution of fragment masses
- Applies to
- Cylindrical metal-cased explosive devices
- Forensic use
- Characterising casing geometry from fragment sizes
Common questions
What forensic question does the Mott formula help answer at a blast scene?+
By fitting the recovered fragment mass distribution to the Mott distribution, an examiner can back-calculate parameters of the original casing, such as wall thickness and material, helping to characterise or identify the type of device used even when the casing itself is destroyed.
Why does casing material affect the fragment distribution?+
The Mott formula's statistical distribution depends on how a given casing material fractures under detonation stress, so brittle versus ductile casing materials produce different characteristic fragment size distributions, which is part of what the formula's parameters capture.
Is the Mott formula still used with modern computational modelling available?+
Yes, it remains a standard quick-reference statistical model in bomb scene reconstruction and munitions analysis, valued for giving an analytically tractable estimate without requiring full computational simulation of the detonation event.
Related terms
- Brisance
- The shattering power of a detonating explosive, distinct from heave (bulk displacement). Measured by the Trauzl lead block test. High-brisance explosives (RDX,...
- Chapman-Jouguet (CJ) Condition
- The steady-state condition in a detonating explosive at which the coupled shock and reaction zone travel at the same velocity (the detonation...
- Deflagration-to-Detonation Transition (DDT)
- The acceleration of a deflagrating burn front to supersonic detonation velocity, triggered by confinement. Relevant to understanding how improvised devices using low...
- DMDNB Taggant
- Dimethyldinitrobutane, a detection marker incorporated into plastic explosives (including Semtex) under the ICAO 1991 Convention on the Marking of Plastic Explosives; allows...
- Dynamic Pressure
- The pressure component due to mass flow of gas behind the shock front, proportional to gas velocity squared; the blast wind that...
- Friedlander Waveform
- The idealised time-pressure history at a point in air following a blast: instantaneous rise to peak overpressure at shock arrival, exponential decay...
- Hopkinson-Cranz Scaling
- The law relating peak overpressure and positive-phase duration to the ratio of range to cube-root-of-charge-mass (the scaled distance Z = R /...
- Mach Stem
- The reinforced shock front that forms near a reflective surface when the direct blast wave and its reflected wave merge, producing anomalously...
- Peak Static Overpressure (Ps)
- The maximum pressure increase above ambient at the shock front, the primary structural damage parameter, scaling with the inverse cube root of...