What happens when a projectile launched at almost 14,500 km/h hits a body of water? To find out, American scientists will film the precise moment of the impact with a special camera.
With the war in Ukraine, we regularly hear about Russian hypersonic missiles. These technologically advanced weaponry would be unstoppable and destructive. What characterizes a hypersonic missile is its speed going beyond Mach 5 and its ability to remain maneuverable at this speed in order to avoid being intercepted. A missile such as the Kh-47M2 Kinzhal, which Russia would have used during a strike in Ukraine, can thus evolve at Mach 9.
If the Americans are behind in the development of such weapons, their projects around hypersonic vehicles are multiple and scientists are carrying out numerous experiments related to this field. This is particularly the case for the laboratories of the Case Western Reserve University in the United States which receive funding from the US Navy and the US Air Force.
Rather than designing such an armament, they seek to capture in image the precise moment of the impact of a projectile moving at nearly 14,500 km/h on a wall of water, that is to say at a hypersonic speed. Scientists expect to see the formation of ice, vapor bubbles and their bursting, or sonoluminescence. They even believe that this last luminous phenomenon could be a possibly exploitable source of energy.
The US Special Operations Command is testing special munitions that can be fired both underwater and in the air. © Ussocom
A camera that takes 200 million images per second
As early as the 1940s, the U.S. military conducted high-velocity projectile impact studies in water to assess the effects of the shock wave on ship hulls. While the speed was far from hypersonic, based on this data, in the 1950s scientists had made extrapolations and estimated that an impact could lead to the formation of ice. An ice called “exotic” because it would not have the usual characteristics of crystalline ice with its hexagonal symmetry.
The researchers of the Case Western Reserve University therefore wish to verify this postulate and their other suppositions by carrying out the impact with the mass of water at this hypersonic speed of 14,484 km/h. You should know that the supersonic speed in water is already 5,630 km/h, while that of the sound barrier in air is around 1,200 km/h.
To carry out their experiment, the researchers will use a gas gun with a 12.2 meter long barrel to propel an 18 mm projectile into a 2.4 m deep reservoir of water. As for propelling rockets, the projectile will be equipped with two charge stages in order to achieve this high velocity. To capture the precise moment of impact, the team will use a very high-speed camera capable of taking 200 million frames per second. For comparison, a human eye can capture 30 frames per second and a capable smartphone can capture up to 300.
Apart from the study of the phenomena induced by the impact, for the military, these results should make it possible to evaluate the potential damage on ships located near strong underwater explosions, or to optimize the flight of hypersonic vehicles or missiles through rain or fog.
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