> They found that a solid sphere, weighing 20kg [...] at about four times the speed of sound [...] 25 megajoules.<p>For comparison, the projectile from a US M829 tank round [0] involves a spike with a mass of 4.6kg traveling at an (initial) speed of mach 4.59, or around 5.70 megajoules. The propellant and all the other stuff which stays behind brings that up to 18.6kg.<p>I assume this cannonball's dramatically higher projectile-mass is needed in order to make up for <i>accuracy</i>, so that a glancing hit still rattles everything enough to make a difference.<p>[0] <a href="https://en.wikipedia.org/wiki/M829" rel="nofollow">https://en.wikipedia.org/wiki/M829</a>
It's like a modern cannonball. They say a 20kg "solid sphere" traveling at 4x the speed of sound could disable a tank by exerting forces on bolts that connect the pieces together, but otherwise leaving the tank with the <i>appearance</i> of being mostly unharmed.
Chinese researchers can claim this, but realistically, the US is one of the only countries that has repeatedly deployed its current tanks in a war context. If you don't have experience with tanks in a war, you'll very quickly learn what matters.