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Dynamics of impacts
Published in Ömer Aydan, Rock Dynamics, 2017
Kenkmann et al. (2011) conducted laboratory experiments with dry and wet sandstone blocks impacted by centimeter-sized steel spheres. They utilized a powerful two-stage light gas gun to achieve impact velocities of up the 5.4 km/s. They concluded that cratering efficiency, ejection velocities, and spall volume are enhanced if the pore space of the sandstone is filled with water. In addition, the crater morphologies differed substantially in both experiments and the vaporization of water upon pressure release significantly contributed to the impact process. Strength and elastic modulus of sandstone used in experiments were 62.4 ± 2.8 MPa and 14.8 ± 1.4 GPa for the dry, and 47.0 ± 3.7 MPa and 12.1 ± 1.0 GPa for a water-saturated sandstone measured perpendicular to the bedding planes.
Ammunition Design Practice
Published in Donald E. Carlucci, Sidney S. Jacobson, Ballistics, 2018
Donald E. Carlucci, Sidney S. Jacobson
Two other concepts of gun propulsion should be mentioned. These are the use of electromagnetically generated force to propel a projectile down a gun and the idea of using a low-molecular weight gas to propel the projectile—the light gas gun. At the time of this writing, neither concept has shown the ability to progress beyond the laboratory stage to a fieldable weapon, although light gas guns are in common use in laboratories to reach velocities with small projectiles approaching meteorite entry speeds.
Comparison of an Electrothermal Plasma Source to a Light Gas Gun for Launching Large Cryogenic Pellets for Tokamak Disruption Mitigation
Published in Fusion Science and Technology, 2018
T. E. Gebhart, S. K. Combs, L. R. Baylor
The pellets launched with the light gas gun are a 50-50 mixture of deuterium and neon formed by combining approximately 600 Torr·l of each gas in a vessel separate from the volume that contains the barrel’s freezing zone. Once the gas is mixed, a gate valve is opened allowing the gas to flow to the freezing zone. The size of the pellet can be calculated using the amount of material frozen into the pellet. A known volume with a known pressure drop allows for an accurate mass of frozen material to be calculated. The diameter of the freezing zone remains constant, so a length can easily be inferred. This combination of gas (600 Torr·l of both neon and deuterium) resulted in pellets with a length-over-diameter ratio of 1.37 and an approximate mass of 0.77 g. The pellets launched with the electrothermal source have a density of 1.2 g/cm3 and a mass of 1.18 g; thus, the mass of the mixed gas pellets is 35% less than the Lexan pellets launched with the electrothermal source. The mass of the pellet has a significant influence on the resulting speed of the pellet; as the pellet mass increases, the resulting speed decreases. The pellet speed is limited by the sound speed of the propellant gas, as shown by gas gun theory.17 Multiple shots were conducted with the light gas gun for two different propellant gases: helium and hydrogen.