Cold flow testing of laboratory-scale hybrid rocket engine test apparatus.

A cold-flow experimental investigation is performed on the Ryerson University lab-scale hybrid rocket engine test apparatus, in order to gain a further understanding of transient phenomena affecting the engine’s hot test firing results to date. The hot test firing data was characterized primarily by noticeable thrust oscillation magnitudes at low frequency being measured by the test stand’s thrust-measuring load cell, relative to somewhat lower magnitude low-frequency pressure oscillations being measured by a head-end pressure transducer. The present investigation allows for the evaluation of the fluid-structure interaction behaviour of the rocket engine’s combustion chamber and upstream oxidizer feed-line/injection apparatus (along with the surrounding test stand structure). Pressurized air at a moderate temperature acts as the working fluid (rather than hot gas arising from combustion), passing through the internal flow system, and exiting at the engine’s exhaust nozzle. Cold flow tests are conducted at three different flow-regulating orifice-plate conditions upstream of the head-end injector: 1) unchoked, 2) marginally choked and, 3) choked, in order to potentially observe any trends in that regard, as tied to feed-system stability/instability. The cold flow test results, from the experimental time-dependent measurement of pressure, thrust and axial acceleration, in turn undergo FFT analyses to help identify any frequency-dependent trends in regard to transient behaviour. Hammer tests are conducted to further establish the relevant lower frequency natural modes of structural vibration of the test apparatus with the engine in position The potential applicability of Karabeyoglu’s well-known thermal lag-combustion-gasdynamic predictive model (for estimating a characteristic frequency), which captures to some degree the intrinsic low frequency combustion-based instability behaviour of hybrid rocket engines, is considered for the present test engine setup. There are some promising comparisons in terms of relevant frequencies of mechanisms in the 20 Hz range, mechanisms that might be coupling to produce a noticeably augmented oscillation condition (as was observed in the hot firing thrust measurements).

Cold flow testing of laboratory-scale hybrid rocket engine test apparatus.

A cold-flow experimental investigation is performed on the Ryerson University lab-scale hybrid rocket engine test apparatus, in order to gain a further understanding of transient phenomena affecting the engine’s hot test firing results to date. The hot test firing data was characterized primarily by noticeable thrust oscillation magnitudes at low frequency being measured by the test stand’s thrust-measuring load cell, relative to somewhat lower magnitude low-frequency pressure oscillations being measured by a head-end pressure transducer. The present investigation allows for the evaluation of the fluid-structure interaction behaviour of the rocket engine’s combustion chamber and upstream oxidizer feed-line/injection apparatus (along with the surrounding test stand structure). Pressurized air at a moderate temperature acts as the working fluid (rather than hot gas arising from combustion), passing through the internal flow system, and exiting at the engine’s exhaust nozzle. Cold flow tests are conducted at three different flow-regulating orifice-plate conditions upstream of the head-end injector: 1) unchoked, 2) marginally choked and, 3) choked, in order to potentially observe any trends in that regard, as tied to feed-system stability/instability. The cold flow test results, from the experimental time-dependent measurement of pressure, thrust and axial acceleration, in turn undergo FFT analyses to help identify any frequency-dependent trends in regard to transient behaviour. Hammer tests are conducted to further establish the relevant lower frequency natural modes of structural vibration of the test apparatus with the engine in position The potential applicability of Karabeyoglu’s well-known thermal lag-combustion-gasdynamic predictive model (for estimating a characteristic frequency), which captures to some degree the intrinsic low frequency combustion-based instability behaviour of hybrid rocket engines, is considered for the present test engine setup. There are some promising comparisons in terms of relevant frequencies of mechanisms in the 20 Hz range, mechanisms that might be coupling to produce a noticeably augmented oscillation condition (as was observed in the hot firing thrust measurements).

Celebratory firing leads to serious injuries – a case report

Firearms are extensively used in shooting incidents, functions or for recreational purposes around the world. However, illegal modifications to a firearm can pose a major challenge to the forensic community, as their examination and subsequent individualisation are not always easy when compared to standard firearms due to the non-availability of standard comparison material and the damage caused to the firearm during test firing. We present a case report of unusual firing by an improvised firearm adapted to produce a loud noise during a marriage party. This led to high pressure inside the barrel, damaging the extractor assembly of the rifle and caused serious injuries to bystanders. An expert must be aware of all usual and unusual results of firings. In this case, an unusual method of firing two bullets shows the generation of high pressure inside the barrel causing the barrel and extractor assembly to break and act as secondary projectile. These cases need thorough investigation and careful observation to achieve positive outcomes.

Penentu Jarak Tembak Berdasarkan Kerusakan Proyektil Timah Tanpa Jacket untuk Senjata Api Genggam Jenis Revolver S&W Kaliber .38 Spesial pada Target Tulang

This study aims to predict the shooting range based on damage the type of lead a projectile without jacket caliber.38 special fired from handguns kinds brand Revolver S & W caliber .38 specials. Based on the phenomenon of criminal cases of abuse handguns types Revolver and the fact that real data it was found that 8% of the amount of lead projectiles without jacket as forensic evidence, the condition has broken the deformed moderate to severe. The study was conducted at the Police Forensic Laboratory experimental method test-fired in the shooting box at short throw distance range of 0.5 to 6 meters , where the bone is positioned at the target position changes location every 0.5 meters, so the total number of shots is 12 times shot on 12 position target location, and finally obtained 12 variations of deformation projectile shot results. Stages test firing conducted through three stages as follows: 1). Phase sample preparation equipment and materials firearms, bullets and target bone. 2). Phase shooting target accurately. 3). Stages of deformation measurements and weighing projectile, arranged in the form of table data. Material samples of bullet used was the type of lead bullets without jacket caliber .38 special with technical specifications diameter of projectile 9.09 mm (real 9.05 mm), length of projectile 17.90 mm (real 18.61 mm), projectile material lead antimony, projectile weight of 10.25 grams, muzzle velocity (initial) 265 m / sec, rounded nose shape, coefficient of form C = 2, the ballistic coefficient i = 0,9 effective range or the distance accurately of 25 meters. Material samples of bone were used as target is 1694 SR veal ribs with bone hardness values (87 ± 1.5) shore, is used for the calibration test firing, a human skull age adults (≥ 35 years) with a value of hardness (78 ± 6 ) shore, is used as the target subjects of research, human ribs (costal C-3 / C-6) adult (≥ 35 years) with a value of hardness (69 ± 19.5) shore, is used as the target subjects of research. Keywords : deformation; projectiles; bones