[BwanaNdege]

Helium is not a propellant or an oxidizer.

Exactly! As I understad it, the helium pressure pushes the fuel & oxidizer from their tanks to the engines, eliminating the need for heavy, expensive and prone to mechanical failure turbo pumps.

Can anyone explain this convoluted paragraph?

"The report devoted a section to the composite overwrapped pressure vessels (COPVs) used to store helium in the second stage propellant tanks of the Falcon 9. The investigation into the September 2016 pad explosion that destroyed a Falcon 9 while being prepared for a static-fire test concluded that liquid oxygen in the tank got trapped between the COPV overwrap and liner and then ignited through friction or other mechanisms. "

Huh??

OK. this explains it. The COPV tank stores BOTH Helium and Oxygen.

[Vaquero]

The helium pressurization reminds me of how ICBMs are blown out of subs.

They have a small tank filled with water. They fire a small solid rocket motor thrust end into the water which flashes the water into steam. The steam pressurizes the tube blowing the icbm out with great force so it pops out of the sea. Then it’s own rocket engine ignites.