FIELD OF THE INVENTION

[1] The present invention specifically pertains to training hand-grenades. More generally, the invention relates to blast simulation as applied thereto.

BACKGROUND OF THE INVENTION

[2] Dummy hand-grenades for training, simulation and practicing (herein after “dummies”) were used and reinvented since the first world war, and maybe well before. As such, GB 123028 discloses a totally passive dummy hand-grenade for practice in throwing, merely bearing the shape and size of a real grenade. At WWII, dummies comprising a replaceable cartridge containing a small amount of explosive charge were introduced, see GB551999 as an example, configured to simulate grenade explosions by a relatively weak sound of blasting. A few decades later, as disclosed in EP2329215, a dummy with laser diodes was used for simulating an explosion’s flash. Much similarly, GB 893080 discloses a dummy comprising a clay body having an axial bore lined by a sleeve in which a cork wad underlies an explosive charge above which is a delay fuse provided with a match head and surrounded by a sleeve ending in a paper collar covering the charge. Colouring matter was incorporated in the clay and marked the explosion’s area. Twenty years ago, as depicted in US20020182976, speaker and light emitters, electrically connected to a microchip and operable in steps of producing a random sequence of light flashes were presented. These random flashes were replaced by an electronic control mechanism enabling an array of light-emitting diodes in a selected time sequence, see e.g. US8113689. US20100072895 also discloses a security device with a control chip connected to speaker(s) and light source(s). A step forwards has been taken in US20180080748A1 (US application No. 15/272,046) which discloses a dummy that allows users to simulate the countdown time for the detonation of a standard grenade, flashbang grenade, and impact grenade, without using explosive charges, fire, or pressurized material. The dummy utilizes both visual (LEDs, max. 6600 Lumens) and auditory feedback (siren, 2.25kHz 105dB at 12V) in a safe and re-usable manner. A simulated detonation is selected by using a switch. Its configuration panel includes a mode selection button to select an operational mode and/or detonation delay time for the grenade simulation apparatus. Upon selection of a loss prevention feature, continuous auditory and/or visual feedback is provided periodically, e.g., every 5 minutes, until switch is turned off. Such a feature may allow the grenade simulation apparatus to be more easily found following a training exercise.

[3] Blast is an anomalous term, but is most frequently used to describe very large amplitude and/or long duration pressure waves accompanying the discharge of weapons, e.g. hand grenades. Taken together, sound, noise, and blast all refer to airborne acoustical phenomena whose energy may be described both in terms of their physical characteristics (amplitude, frequency content, and / or duration) and their effects on man's physiology and behavior. There are applicable a few definitions peculiar to impulse blast, i.e., peak pressure is the highest pressure achieved, expressed in dB etc.; Rise Time is the time taken for the single pressure fluctuation that forms the initial or principal positive peak to increase from ambient pressure to the peak pressure level; Pressure wave duration (A-Duration) is the time required for the pressure to rise to its initial or principal positive peak and return momentarily to ambient pressure; Pressure envelope duration (B -Duration) is the total time that the envelope of pressure fluctuations (positive and negative) is within 20 dB of the peak pressure level. Included in this time would be the duration of that part of any reflection pattern that is within 20 dB of the peak pressure level.

[4] Sound waves can be described by many characteristics: wavelength, amplitude, time-period, frequency, velocity or speed, mouthpiece parameters, bell parameters, conic vs cylindrical shaped air column and pathway thereof, materials (e.g., plastic vs metal strings), air-humidity, room parameters (e.g., room size and dimensions, open space(s) and windows size and shape, walls coatings) and so on and so forth; hence every musical instrument sounds differently (Fig. 1). The subjective impression of frequency, in the same sense that loudness is the subjective sense of the intensity or amplitude of a sound. As such, pitch is a psychoacoustic variable, and the degree of sensitivity shown to it varies widely with people. The pitch of a tone or note allows it to be placed in a musical scale; thus, notes of a scale are often called pitches, and given names (A, B, do, re, mi, etc.). The distance between two pitches is called an interval. However, equal frequency intervals do not always give the same sense of pitch distance, depending on the range in which the interval is situated. For instance, a fifth in a high frequency range may seem to be a smaller pitch distance than a third in a lower range; the MEL scale is an attempt to measure this variation. Blasts are also defined in psychological terms. The measures of loudness are the phon and the sone. The sone is a perception of sound pressure and is obtained by a conversion of eight octave bands into sones from an appropriate table. The phon is a unit of loudness for pure tones. Human sensitivity to sound is variable across different frequencies; therefore, although two different tones may have identical sound intensity, they may be psycho-acoustically perceived as differing in loudness. The phon is merely a transformation of the sone into a logarithmic scale. Sounds that are perceived as equally loud to the human ear will have the same sone or phon value. The mel is used here as a subjective measure of the pitch differences in frequency between sounds.

[5] There is still a need for a dummy for simulating different types of explosions, in various locations.

SUMMARY OF THE INVENTION

[6] To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a training hand-grenade (100) comprising a housing (101) optionally interconnected with a safety lever for activating the grenade (102); within the housing accommodated at least one blast simulator selected from a group consisting of a speaker (120) for generating an acoustical blast imitation (10), one or more light emitters (130), a smoke generator (131) and any combination thereof; wherein a processor (150), intercommoned with a power supply (140), and the blast simulator, configured to operate the blast simulator in one of two or more preset modes of operation, each of the modes of operation is characterizing a predefined combination (fingerprint) of blast acoustic parameters, and optionally also light and smoke effects.

[7] It is another object of the invention to disclose a training grenade as defined above, wherein the blast acoustic parameters selected from amplitude, frequency, content, duration, peak pressure, rise time, pitch, sone, phon, mel values and explosion profile.

[8] It is another object of the invention to disclose a training grenade as in any of the above, wherein light effect is selected from a group consisting of light radiant flux (F) and radiation intensity (/) of burning fireball.

[9] It is another object of the invention to disclose a training grenade as in any of the above, wherein the safety lever is either (i) permanently affixed to the housing of the grenade or (ii) detachable or releasably attached from the same.

[10] It is another object of the invention to disclose a training grenade as in any of the above, wherein the fixture of the safety lever is blast proof. [11] It is another object of the invention to disclose a training grenade as in any of the above, wherein speaker is configured to detach from the housing of the grenade after the blast.

[12] It is another object of the invention to disclose a training grenade as in any of the above, wherein at least one portion of the cross-section of the housing in its rear portion, namely from the speaker outside of the grenade, is either conical or cylindrical.

[13] It is another object of the invention to disclose a training grenade as in any of the above, wherein the power supply is selected from a group consisting of rechargeable batteries and disposable batteries.

[14] It is another object of the invention to disclose a training grenade as in any of the above, wherein the CPU is configured to provide an explosion profile (fingerprint) simulating hand grenades, the hand grenade is selected from the group consisting of fragmentation grenade, smoke grenade, illuminating grenade, high explosive grenade, anti-tank grenade, sting grenade and stun grenade.

[15] It is another object of the invention to disclose a training grenade as in any of the above, wherein the explosion profile corresponds to a single, double or multiple-ignition grenade.

[16] It is another object of the invention to disclose a training grenade as in any of the above, wherein its further comprising a CPU (150) interconnected with a database comprising two or more different combinations (fingerprints) of blast acoustic parameters, and optionally also light and smoke effects; and a selector interconnected with the CPU; wherein the CPU interconnected with signaling modules controlling the speaker generated acoustic phenomena and the light and/or smoke generated emission; and wherein the selector configured to set the blast parameters prior to use.

[17] It is another object of the invention to disclose a training grenade as in any of the above, wherein at least one of the signaling module is provided with a real-time feedback system (200) for obtaining location and blast data, collecting posteriori data, processing the data and resetting the signaling module according to the processed data.

[18] It is another object of the invention to disclose a training grenade as in any of the above, wherein the feedback system comprises a sensor (170) interconnected to CPU (150), a receiving module for receiving input from the sensor, a data analysis module for analyzing the input, and a detonation module for adjusting blast parameters based on real-time feedback (204). [19] It is another object of the invention to disclose a training grenade as in any of the above, wherein the feedback system is intercommunicateable with one member of a group consisting of GPS; cellular tracking modules; Bluetooth tracking system; RFID-containing tracking system; real-time locating systems (RTLS); satellite tracking system; including Active radio frequency identification (Active RFID), Active radio frequency identification - infrared hybrid (Active RFID-IR), Infrared (IR), Optical locating, Low-frequency signpost identification, Semi-active radio frequency identification (semi-active RFID), Passive RFID RTLS locating via Steerable Phased, Array Antennae, Radio beacon, Ultrasound Identification (US-ID), Ultrasonic ranging (US-RTLS), Ultra- wideband (UWB), Wide-over-narrow band, Wireless Local Area Network (WLAN, Wi-Fi), Bluetooth, Clustering in noisy ambience, Bivalent systems; simultaneous localization and mapping systems and any combination thereof.

[20] It is another object of the invention to disclose a training grenade as in any of the above, wherein the acoustical phenomena are selected from the group consisting of: amplitude, frequency content, duration, peak pressure, rise time, pitch, sone value and explosion profile.

[21] It is another object of the invention to disclose a training grenade as in any of the above, wherein the grenade comprises at least one first communication module, and is in communication, by means of the module, with at least one second external communication module located in one or more remote locations; the external modules is in communication with one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof.

[22] It is another object of the invention to disclose a training grenade as in any of the above, wherein the grenade is free of one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof.

[23] It is another object of the invention to disclose a training grenade as in any of the above, wherein the grenade, when operated under defined terms, do not activate one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof

[24] It is another object of the invention to disclose a training system for the grenade as defined in any of the above, wherein the system comprising one or more the training grenades operateable within at least one first location; at least one external communication module located in one or more second remote locations. [25] v at least one of the grenades located within at least one first location intercommunicates with the at least one external communication module located in one or more second remote locations and with one or more operators located within at least one third remote location.

[26] It is another object of the invention to disclose a training system for the grenade as defined in any of the above, wherein the grenade is located within at least one location; the grenade further comprises a wireless communicator intercommunicates with one or more operators located within another location.

[27] It is another object of the invention to disclose a training system for the grenade as defined in any of the above, wherein at least one of the operators is configured with communication means to operate at least one of the grenades.

[28] It is another object of the invention to disclose a training system for the grenade as defined in any of the above, wherein the operator is configured with communication means to operate at least one of the grenades.

[29] It is another object of the invention to disclose a method for training a user with hand-grenade (100), comprising step of providing a training grenade (dummy); throwing the dummy, thereby activating a sensor (201) located in connection with the housing of the dummy; at time the dummy is static, transmitting input data obtained by the sensor to a receiving module (202); analyzing and processing the data in a CPU (203) located with the housing; defining the environment surround the dummy; and setting blast parameters (204); and simulating blast of the dummy characterized by environment-related blast parameters (205).

[30] It is another object of the invention to disclose a method for training a user with hand-grenade comprising: providing a training grenade (dummy); proving a CPU (203) within the dummy and intercommuting CPU with a database comprising two or more different combinations (fingerprints) of blast acoustic parameters, and optionally also light and smoke effects; by means of a selector, defining grenade type; throwing the dummy, thereby activating a sensor (201) located in connection with the housing of the dummy; at time the dummy is static, transmitting input data obtained by the sensor to a receiving module (202); analyzing and processing the data by the CPU; defining the environment surround the dummy in function of the blast fingerprints parameters (204); and then simulating blast of the dummy characterized by environment-related blast parameters (205) so that a specific fingerprint of blast acoustic parameters, and optionally also light and smoke effects is provided. [31] It is another object of the invention to disclose a method for training a user with hand-grenade comprising providing a training grenade (dummy); proving a CPU (203) within the dummy and intercommuting the CPU with a database comprising two or more different combinations (fingerprints) of blast acoustic parameters, and optionally also light and smoke effects; providing a wireless communicator within the dummy; by means of a selector, defining grenade type; throwing the dummy, thereby activating a sensor (201) located in connection with the housing of the dummy; at time the dummy is static, transmitting input data obtained by the sensor; analyzing and processing the data by the CPU; defining the environment surround the dummy in function of the blast fingerprints parameters (204); and then signaling the parameters to an external receiving module located at a remote location, by means of the external receiving module, simulating blast of the dummy characterized by environment- related blast parameters (205) so that a specific fingerprint of blast acoustic parameters, and optionally also light and smoke effects is provided.

[32] It is another object of the invention to disclose a method for producing a training hand-grenade (100). The method comprising steps of providing a housing (101), optionally interconnecting the same with a safety lever for activating the grenade (102); within the housing accommodating at least one blast simulator selected from a group consisting of a speaker (120) for generating an acoustical blast imitation (10), one or more light emitters (130), a smoke generator (131) and any combination thereof; wherein the method further comprising steps of a intercommunicating processor (150) with a power supply (140) and with the blast simulator, configuring the same to operate the blast simulator in one of two or more preset modes of operation; and characterizing each of the modes of operation by a predefined combination (fingerprint) of blast acoustic parameters, and optionally also light and smoke effects.

[33] It is another object of the invention to disclose a method for producing a training hand-grenade (100). The method comprising steps of interconnecting a CPU (150) with a database comprising two or more different combinations (fingerprints) of blast acoustic parameters, and optionally also with light and smoke effects; interconnecting a selector with the CPU; interconnecting the CPU with signaling modules controlling the speaker generated acoustic phenomena and the light and/or smoke generated emission; and configuring the selector to set the blast parameters prior

[34] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, parameters are one or more members of a group consisting of initiation time (time of operating the dummy), small indoor environment (from about lm ³ to about 9),

? medium size indoor environment (from about 9m ³ to about 24m ³ ), large size indoor environment (from about 24m ³ to about 100m ³ ), outdoors urban environment being adjacent (distance of about 0.5m to about 6m) to at least one solid wall, open outdoors environment, environment with glass/metal-like solid vertical structures, environment with wall-like solid vertical structures, environment with plants/bushes-like semi-rigid vertical structurers, day time, night time, strong wind (more than 2 m/s) or weak/no-wind (less than 2 m/s)

[35] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the blast acoustic parameters selected from amplitude, frequency, content, duration, peak pressure, rise time, pitch, sone, phon, mel values and explosion profile.

[36] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, light effect is selected from a group consisting of light radiant flux (F) and radiation intensity (I) of burning fireball.

[37] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, safety lever is either (i) permanently affixed to the housing of the grenade or (ii) detachable or releasably attached from the same.

[38] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the fixture of the safety lever is blast proof.

[39] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the speaker is configured to detach from the housing of the grenade after the blast.

[40] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, at least one portion of the cross-section of the housing in its rear portion, namely from the speaker outside of the grenade, is either conical or cylindrical.

[41] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the power supply is selected from a group consisting of rechargeable batteries and disposable batteries.

[42] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the CPU is configured to provide an explosion profile (fingerprint) simulating hand grenades, the hand grenade is selected from the group consisting of fragmentation grenade, smoke grenade, illuminating grenade, high explosive grenade, anti tank grenade, sting grenade and stun grenade. [43] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the explosion profile corresponds to a single, double or multiple ignition grenade.

[44] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, CPU (150) is interconnected with a database comprising two or more different combinations (fingerprints) of blast acoustic parameters, and optionally also light and smoke effects; and a selector interconnected with the CPU; wherein the CPU interconnected with signaling modules controlling the speaker generated acoustic phenomena and the light and/or smoke generated emission; and wherein the selector configured to set the blast parameters prior to use.

[45] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, at least one of the signaling module is provided with a real-time feedback system (200) for obtaining location and blast data, collecting posteriori data, processing the data and resetting the signaling module according to the processed data.

[46] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the feedback system comprises a sensor (170) interconnected to CPU (150), a receiving module for receiving input from the sensor, a data analysis module for analyzing the input, and a detonation module for adjusting blast parameters based on real-time feedback (204).

[47] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the feedback system is intercommunicateable with one member of a group consisting of GPS; cellular tracking modules; Bluetooth tracking system; RFID- containing tracking system; real-time locating systems (RTLS); satellite tracking system; including Active radio frequency identification (Active RFID), Active radio frequency identification - infrared hybrid (Active RFID-IR), Infrared (IR), Optical locating, Low- frequency signpost identification, Semi-active radio frequency identification (semi-active RFID), Passive RFID RTLS locating via Steerable Phased, Array Antennae, Radio beacon, Ultrasound Identification (US-ID), Ultrasonic ranging (US-RTLS), Ultra-wideband (UWB), Wide-over-narrow band, Wireless Local Area Network (WLAN, Wi-Fi), Bluetooth, Clustering in noisy ambience, Bivalent systems; simultaneous localization and mapping systems and any combination thereof. [48] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the acoustical phenomena are selected from the group consisting of: amplitude, frequency content, duration, peak pressure, rise time, pitch, sone value and explosion profile.

[49] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the grenade comprises at least one first communication module, and is in communication, by means of the module, with at least one second external communication module located in one or more remote locations; the external modules is in communication with one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof.

[50] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, grenade is free of one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof.

[51] It is another object of the invention to disclose a method for producing a training hand-grenade (100). In this method, the grenade, when operated under defined terms, do not activate one or more of the following: a light emitter, a smoke generator, a speaker and any combination thereof.

BRIEF DESCRIPTION OF THE FIGURES

[52] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[53] Fig. 1 schematically illustrates E5 played on the violin; played on the clarinet; F2 played on the bassoon; Bb 3 played on the trumpet, adapted from Figs. 3.5-3.11 in Lapp, David R. The physics of music and musical instruments. Wright Center for Innovative Science Education, Tufts University, 2003;

[54] Fig. 2 schematically illustrates a few profiles of grenade explosions and blasts thereof; namely grenade explosion sound effects as recorded by the inventors, (1) as disclosed in a first currently available web site https://www.rendefhub.com/ardera/gfenade-explosion-soand-eff ect (2) and as disclosed in a second currently available web site https://www.pond5.com/soi.md- effects/l/grenade.html#2 both sites are incorporated herein as a reference;

[55] Fig. 3 shows a schematic illustration of a hand grenade; [56] Fig. 4 is a block diagram, showing the functional elements of the blast simulator of the dummy of the current invention; and

[57] Fig. 5 is a flow chart, illustrating the steps of a method for blast simulation based on preset parameters and real-time feedback.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[58] In the following description of the embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration the specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized because structural changes may be made without departing from the scope of the present invention.

[59] The term “blast” generally refers to the increased pressure and flow resulting from the deposition of a large amount of energy in a small and very localized volume. In this invention, blast refers to a predefined sound (and other energy discharging profile, such as radiation, light, vibration, explosion, detonation, discharge).

[60] The terms “hand grenade” and “grenade” interchangeably refer to any type of available small explosive, chemical, or gas bomb that is used at short range. The terms are applicable to any grenade, single, double or multiple ignitions; such as fragmentation (defensive) grenades, illuminating grenades, chemical (e.g., smoke and riot control-) grenades, incendiary, high explosive (offensive) and anti-tank grenades and nonlethal grenades, such as Stun (flashbang) and sting grenades. Each type of grenade is characterized by an individual blast explosion profile. Fig. 2 illustrates different profiles sampled at 44.1KHz

[61] The term “dummy” refers hereinafter to a non-lethal hand-grenade configured as a toy or for training, simulation and practicing. In a non-limiting manner,

[62] The term “feedback loop system” herein in the present invention refers to a system for obtaining data from sensors on the grenade after throwing, processing of the data, followed by setting blast parameters by controller, based on the data.

[63] The term “sone value” refers hereinafter to how loud the blast is perceived by a person hearing the blast. The sone is defined by both the frequency of the sound, and its intensity (on the decibel scale). [64] The term “about” refers hereinafter to a value being lower than or greater than 20% of the defined value.

[65] Jackson et al. have stated that explosion sound is due to the disturbed of surrounding gas molecules which produces a sound effect when explodes, it will be bound to promote the process when a burst of energy is released, and produces sound. Pyrotechnic sound effects are mainly due to the explosion and intermittent combustion. Velocity of pyrotechnic detonation is faster, explosion sound is more violent and explosive sound has its inherent tone, but according to different types of pyrotechnic, some voices are "sharp" and some are "rounded." Sound effect of flash blast bomb refers to a large number of gaseous product and heat constraints by the housing when releasing generated by explosion, and occurs the rapid expansion to cause the gas molecules disturbances which produces sound effects. Sound effects of flash bomb blast is related to combustion rate of charge, the charge mass and strength of the housing, See Jackson Jr, B., et al. Substitution of Aluminum for Magnesium as a Fuel in Flares. No. PA-TR-4704. PICATINNY ARSENAL DOVER NJ 1975 incorporated herein as a reference.

[66] The term “acoustic parameters” and “acoustic phenome” thereof interchangeably refer hereinafter in a non-limiting manner to parameters selected from pr (i.e., Peak rarefactional pressure); pc (i.e., Peak compressional pressure); pr.3 (i.e., Derated peak rarefactional pressure); pc.3 (i.e., Derated peak compressional pressure); Isppa (i.e., Spatial-peak pulse- average intensity); Isppa.3 (i.e., Derated spatial-peak pulse-average intensity); MI (i.e., Mechanical index); AWF (i.e., acoustic working frequency); Depth (i.e., Distance to start of pulse); PD (i.e., Pulse duration); PII (i.e., Pulse-intensity integral); PII.3 (i.e., Derated pulse- intensity integral); anther acoustic parameters can be derived from the above, including but not restricted to the following: IOB, namely Output Beam intensity (i.e., Power divided by beam width measured from planar or orthogonal cross scan); Focal volume (i.e., Combination of beam widths from transverse and axial scans); ISPTA, namely Spatial-peak temporal- average intensity (i.e., For a single -element transducer, PII divided by pulse repetition interval); ERA namely effective radiating area (i.e., The area close to the transducer through which most of the acoustic power passes); BNR namely beam non-uniformity ratio (i.e., The ratio of the spatial-peak temporal- average intensity to the spatial-average intensity, averaged over the effective radiating area); amplitude, frequency, content, duration, peak pressure, rise time, pitch, sone, phon, mel values and explosion profile etc.

[67] Reference is now made to Figs 3-4 of the present invention, providing a schematic representation of a dummy training hand-grenade (100). The dummy comprises a housing (101), a safety lever (102), and a blast generator (110). The housing of the dummy shown in figure 3 (101), is cylindrical. In other embodiments, the cross-section of the dummy may be conical. As mentioned hereinabove, the shape of the air column and pathway affect the sound emitted during the simulated blast. The safety lever (102) is shown in a closed and open position. In some embodiments of the current invention, the safety lever (102) is detached from the dummy during the simulated blast. In other embodiments, the safety lever is configured to remain attached to the dummy during the simulated blast.

[68] A block diagram showing the functional components of the blast generator (110) is shown in Fig 4. The blast generator (110) comprises a controller unit (150), a speaker (120), a light generator (130), and a power supply (140). The CPU comprises signaling modules, for controlling the sound and light parameters.

[69] In some embodiments of the current invention, the blast parameters are preset during manufacture. These blast parameters include intensity, frequency, duration, peak pressure, rise time, pitch, sone value and explosion profile for determining the type of simulated grenade.

[70] The power supply (140) of the blast generator may consist of a disposable battery, or a rechargeable battery.

[71] In other embodiments of the current invention, the blast parameters are set prior to use. The blast parameters are set by a selector (160) interconnected to the CPU, as shown in Figure 4. Setting blast parameters prior to use, enables additional factors affecting the blast to be taken into consideration, such as open/closed space, room size, window size and shape.

[72] In other embodiments of the present invention a feedback loop system is provided enabling the user to adjust the blast parameters of the dummy grenade according to the type of grenade to be simulated, for example fragmentation grenades or stun grenades, detonating in proximity of open/closed space, room-size, window shape and size, wall type, open field, selected sone value.

[73] Modules of the feedback loop system include at least one sensor, a module for receiving sensor input, a data processing module for analyzing input, and a detonation module for adjusting blast parameters according to processed input data.

[74] In other embodiments of the current invention, some of the blast parameters are preset, and other blast parameters are determined based on real-time feedback. Input for the feedback system is obtained from at least one sensor (170) on the dummy, interconnected to the CPU, shown in Figure 4. A flow chart illustrating the method implementing the real-time feedback system is shown in Figure 5. The feedback method (200) comprises throwing the dummy (201), activating the sensor. Sensors can be proximity sensors, position sensors, motion sensors, gyroscope sensors, humidity sensors, temperature sensors and image sensors. Data from the aforementioned sensors are then transmitted to the CPU (202). The input from the sensor is subsequently processed by the CPU in step (203), and blast parameters determined from sensor input are set in step (204). This is followed by a blast simulation step (205), based on preset blast parameters, and blast parameters determined from sensor input.

LIGHT

[75] Radiation mathematical model of pyrotechnic flash are available in the literature, see e.g., Jiao Qing Jie, Ma Wei, Xu You Wen “Study on pyrotechnics light radiation experiment” Beijing Institute of Technology, 2000, 20 (1): 129-132; and Ma, Yongzhong, Zhiwei Ma, and Guangtao Zhu. "Research on Charge Formula Design and Effect of Flash Blast Bomb." 2016 International Conference on Education , Management and Computer Science. Atlantis Press, 2016, both are incorporated herein as reference!. In the following equations, the degree of convergence of the condensed phase particles in a band (l1~l2). F(X-T) is formula of blackbody radiation function. A is the surface area of the fireball, e Dl is average emission rate of a condensed phase particles in the wavelength range. Fireball radiation comes mainly from surface radiation of condensed phase particles, so radiant flux of light burning fireball (F) is as follows:

[77] The radiation intensity (I) of the fireball is as follows

SMOKE

[79] Yngve et al. have underlined that an explosion causes a variety of visual effects in addition to the light refraction by the blast wave. An initial chemical or nuclear reaction often causes a blinding flash of light. Dust clouds are created as the blast wave races across the ground, and massive objects are moved, deformed, or fractured. Hot gases and smoke form a rising fireball that can trigger further combustion or other explosions and scorch surrounding objects, see Yngve, Gary D., James F. O'Brien, and Jessica K. Hodgins. "Animating explosions." Proceedings of the 27th annual conference on Computer graphics and interactive techniques ACM Press/Addison-Wesley Publishing Co., 2000, incorporated herein as a reference.

[80] Upon a blast, a mixture of air and gaseous combustion products is filling the environment. Momentum conservation is enforced by the Euler equations (Navier-Stokes with zero viscosity):

[81] u ^' = -(u · V)u - Vp/p + f/p Eq. 3

[82] where u is the fluid velocity, p density, p pressure, f any external forces acting on the fluid, and an overdot denotes differentiation with respect to time. The same grid that holds the fluid’s velocity also holds the fluid’s temperature. The temperature evolves according to:

[84] where T denotes the fluid temperature, T _a ambient temperature, T _max the maximum temperature in the environment, and H heat energy transferred into the fluid, and cooling constant c _r ; see Bryan E. Feldman, James F. O'Brien, and Okan Arikan. "Animating Suspended Particle Explosions". In Proceedings of ACM SIGGRAPH 2003, 708-715, August 2003 incorporated herein as a reference.

EXAMPLE I

[85] Reference is now made to Fig. 6, schematically illustrates a building 601 near which a dummy according to one embodiment of the invention was thrown (initiated) at position 602. Prior exploding, the dummy locates it position, here, outside and adjacent building 601. As it is an external explosion, it will be directed to mimic a certain explosion fingerprint, optionally combining sound acoustics with light and/or with smoke. In case the dummy comprises a selector, which defines the type of the grenade, e.g., fragmentation grenade, smoke grenade, illuminating grenade, high explosive grenade, anti-tank grenade, sting grenade or stun grenade, and the explosion phenomena will be mimicking an outside explosion of this certain type of grenade, here e.g., a regular-type of fragmentation army grenade (603a); a high explosive fragmentation army grenade (603b); a SWOT-type double ignition grenade (603c), or a small smoke grenade (603d).

EXAMPLE II [86] Reference is still made to Fig. 6, presenting the same dummy grenade (604), operated now within building 601. As the acoustics changes from an open urban field to an indoor urban field, the acoustics dramatically changes and the explosion of aforesaid regular-type fragmentation army grenade (603a) is changes now to fingerprint (605).

EXAMPLE III

[87] Reference is still made to Fig. 6, presenting an urban zone 606 having multiple high close neighboring buildings, some of which are covered with glass windows and/or glass walls. In this seen, the explosion of aforesaid regular-type fragmentation army grenade (603a) now has a new fingerprint which is characterized by a series of two or more dominate echoes, see 608 and 609.

EXAMPLE IV

[88] Reference is still made to Fig. 6, presenting a building 601 near which a dummy 610 was thrown. In this embodiment of the invention, dummy 610 either (i) comprises a speaker or (ii) otherwise does not include a speaker. When operated, the grenade locates it position (here, open urban field) and wirelessly signals a remote speaker 611 specifications such as location, type and time so that the speaker emits of blast acoustic parameters 612. A combination is provided in another embodiment of the invention where some of the explosion parameters are provided by dummy (610) and so by the remoted speakers (611), light or smoke generators.

EXAMPLE V

[89] Reference is still made to Fig. 6, presenting an open field. Here the explosion provided by the dummy mimicking same regular-type of fragmentation army grenade (603a) is quite different, see 614.

[90] While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. It will further be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims which follow.