Optical and acoustical measurement of ballistic noise signatures

Supersonic projectiles in air generate acoustical signatures that are fundamentally related to the projectile’s shape, size, and velocity. These characteristics influence various mechanisms involved in the generation, propagation, decay, and coalescence of acoustic waves. To understand the relationships between projectile shape, size, velocity, and the physical mechanisms involved, an experimental effort captured the acoustic field produced by a range of supersonic projectiles using both conventional pressure sensors and a schlieren imaging system. The results of this ongoing project will elucidate those fundamental mechanisms, enabling more sophisticated tools for detection, classification, localization, and tracking. This paper details the experimental setup, data collection, and preliminary analysis of a series of ballistic projectiles, both idealized and currently in use by the U.S. Military.

Spinal cord trauma by air gun projectiles in five cats

Spinal cord trauma induced by ballistic projectiles is considered uncommon in domestic animals, particularly in cats. Outdoor, and indoor-outdoor cats are at greater risk of receiving gunshot wounds. Despite their small size, moderate speed and poor aerodynamic design, projectiles from compressed air guns (pellet guns) can cause severe injury. Treatment and prognosis of animals presented with gun-related injuries can vary considerably, depending on the affected spinal segment location of the lesions, and extent of tissue damage. Due to the unusual occurrence, of this type of trauma in feline patients, the goal of this report is to describe the neurologic, radiographic, and surgical findings in five cats with spinal injury secondary to air gun projectiles.

Attitude Determination Algorithms through Accelerometers, GNSS Sensors, and Gravity Vector Estimator

Aircraft and spacecraft navigation precision is dependent on the measurement system for position and attitude determination. Rotation of an aircraft can be determined measuring two vectors in two different reference systems. Velocity vector can be determined in the inertial reference frame from a GNSS-based sensor and by integrating the acceleration measurements in the body reference frame. Estimating gravity vector in both reference frames, and combining with velocity vector, determines rotation of the body. A new approach for gravity vector estimations is presented and employed in an attitude determination algorithm. Nonlinear simulations demonstrate that using directly the positioning and velocity outputs of GNSS sensors and strap-down accelerometers, aircraft attitude determination is precise, especially in ballistic projectiles, to substitute precise attitude determination devices, usually expensive and forced to bear high solicitations as for instance G forces.