Impactless, in-tube sabot separation technique useful for modest-sized supersonic ballistic ranges

Abstract

A simple and high performance sabot separation technique which is useful even in about 10-m-long supersonic ballistic ranges has been developed. The normal in-flight sabot separation distance is vastly reduced by adding an addition tube with no diaphragm that may cause damage to the projectile. The launch tube of the ballistic range is subdivided to the acceleration, ventilation, and sabot separation sections. In the ventilation section, both the precursor shock wave driven by the sabot when coasting through the acceleration section and the driver gas is vented out to the dump chamber. In the sabot separation section, only the sabot experiences a great dragging pressure imbalance whereas the drag to the projectile is kept negligible. Initially, the whole system except for the driver gas chamber is connected without any diaphragm; the range operation is not accompanied by any high-speed impact among the sabot, diaphragm, and other related solid parts. The experimental environment can be kept clean. The influence of the muzzle blast is eliminated within a reasonably short distance from the muzzle because it delays owing to the ventilation section. Calibration experiments and the demonstration of flow visualization and boom measurement of supersonic flight were conducted using a 25 mm bore, Mach-2 ballistic range.

Staged Aft Body for Alleviation of Tail Boom

“…In the sabot separation section (length of 1.4 m), the sabot is separated from the model because of the imbalanced pressure between the front and back of the sabot. The pressure increases on the front side of the sabot because of an advancing sabot-driven shock wave, whereas the pressure decreases on the rear side because of the ventilation [20]. At the muzzle, the sabot collides against a metal plate and is then trapped.…”

Low-Boom Performance Demonstration of a Long, Staged Aftbody

“…This experimental setup employed a unique sabot separation scheme, [6][7][8] which enabled the setup to launch a model with a length-to-diameter ratio of higher than 20. The in-tube catapult launch scheme 8) was combined with mechanical sabot separation; in this scheme, the sabot impinges against a sabot stopper plate.…”

Validation of measurement accuracy for near-field pressure around supersonic projectiles in a ballistic range

“…Near-field pressure measurement experiments in a ballistic range were initially conducted by NASA in the 1960s [17]. Since then, the experiments have been performed by many researchers in universities and at NASA [16,[18][19][20]. A ballistic range at the Institute of Fluid Science, Tohoku University was constructed in 2002.…”

“…In ballistic range experiments, the near-field pressure is generally measured by a flash-mounted pressure transducer in a plate [16,18,19]. In this case, shock waves generated from a free-flight projectile are reflected and diffracted at the plate, and these reflected/diffracted shock waves interfere with the measured pressure waveforms.…”