What is the purpose of the piezoelectric crystal in the RPG-7 HEAT round?

The piezoelectric crystal in the RPG-7 HEAT round is specifically designed to arm the warhead upon firing. This crystal activates the detonator when subjected to the pressure generated during the launch, ensuring that the warhead is safe until it is fired. This safety mechanism is crucial as it prevents unintended detonation if the round is dropped or mishandled prior to being launched. The reliable arming of the warhead ensures that it functions as intended once it reaches its target, allowing for effective engagement of armored vehicles and fortifications.

The other options do not accurately describe the purpose of the piezoelectric crystal. For instance, while enhancing penetration capability and increasing explosive power are important attributes of the RPG-7 HEAT round, they are achieved through the design and composition of the warhead itself, rather than by the piezoelectric crystal. Stabilizing flight is also a key component of missile design, but that function is typically achieved through fins or stabilizers, not through the piezoelectric mechanism.