What V 2 has done is not quite like breaking the sound barrier...

That said, it had never been done before.
Scientists know constrictions accelerate fluids and fluid power is the cube of its speed.

Increasing fluid power should be easy...
at least in theory.
Since the 1800's many have tried and failed to significantly increase fluid speed and power.

From then to today no one produced the acceleration required... until V 2.

V 2 achieved twice the acceleration of any previous accelerator...

and eight times the power.
the basics
science