The WASP knife is certainly an interesting concept. It’s a knife that can instantly inject 800psi of CO2 into whatever it stabs once a release button is pressed.
According to the manufacturer, the knife was made for divers as a defense against large ocean predators. From their website:
As divers, we all know what the effects of compressed gas are underwater. Our training teaches us that our lungs would burst from over-inflation if we held our breath and rose to the surface. This principle is key to the effectiveness of the WASP Injection System.
This weapon injects a freezing cold ball of compressed gas, approximately the size of a basketball, at 800psi nearly instantly. The effects of this injection will drop many of the world’s largest land predators. The effects of the compressed gas not only cause over-inflation during ascent when used underwater, but also freezes all tissues and organs surrounding the point of injection on land or at sea.
When used underwater, the injected gas carries the predator to the surface BEFORE blood is released into the water. Thus giving the diver added protection by diverting other potential predators to the surface.
As you can see from the video at the top of this post, it makes quick work of a watermelon. The following video shows how the knife performs in ballistics gel.
As you can see, the function of the knife performs much better when it has a pocket of air to allow for expansion of the gas.