## 1 Introduction
Each type has its advantages and disadvantages: the directed water devices project the water at higher speeds, but the affected surface is smaller, and the EOD technician must be more precise in the placement of the device and even know the internal disposition of the IED components. On the other hand, with omnidirectional devices, the technician does not have to be concerned about the device orientation; they are cheap, simple designs and can even be made by the EOD teams themselves with mineral water bottles or similar (these are known as Mineral Water  
Figure 1: Basic elements of an IED. Bottles (MWBs)) [9]. There are some patented models on the market [7; 9] that are offered to police forces and armies around the world. Even so, it is common for specialists to use handcrafted devices made by themselves. The system is simple: the device contains water or another fluid and an explosive charge that projects this liquid onto the IED. However, the apparent simplicity of the device is contrasted by the complexity of the explosive wave phenomenon, being necessary a study that provides more information in order to optimize variables such as the mass of explosive to be used for a particular amount of fluid, the effective distance between the device and the IED, the type of fluid, as well as other variables that influence the speed of the fluid and, therefore, its disruptive power. However, there is a dramatic lack of studies published in the open literature on the design and analysis of the factors that intervene in the operation of water projection counter-IED devices. The few studies available are limited to directional water-jet propulsion devices. [PERSON] et al. [10] address the study of water-jet propulsion due to high explosive detonation. They evaluate the velocity of water when experimentally measured, as compared to the prediction given by the Gurney equation. However, as the authors rightly state, the \"Gurney equation can provide fair results regarding initial velocity of metallic fragments for explosively driven metal casings\" [10], but gives wrong predictions for the projected water front. [PERSON] [11] addresses the simulation of the internal ballistics of a two-chambered recoilless projected water disruptor. [PERSON] et al. [12] use a single base propellant, also with a directional disruptor, for an experimental study oriented towards qualification tests (impact, sealing, vibration, shock, etc.). On cylindrical devices, [PERSON] [8] patented a fluid-filled bottle or plastic container that contains an adjustable sheet explosive, to direct the fluid projectile towards the IED. However, to the best of the authors' knowledge, no research work can be found in the literature on the design, optimization, or study of the parameters of an omnidirectional counter-IED device. Consequently, the present study aims to provide new research experimental data, useful to researchers who study the optimization of omnidirectional counter-IED devices, designers, or even the EOD units of police and military forces, constructing their own devices in the most efficient way. To do so, the impact of the problem variables on the device effectiveness (which can be assimilated with the speed of the projected liquid) is analyzed, as well as the interaction between significant factors, through the Design of Experiments (DoE) and statistical analysis. This paper begins by describing the mathematical background of the used methodology and, later on, the factors selected for the tests are justified (Section 2). After this, the tests carried out are detailed and the results obtained are discussed (Section 3). Finally, the conclusions of this work are presented (Section 4).