It's true that COPVs are rather common in aerospace (being the lightest pressure tank technology available). > Or has SpaceX actually loaded fuel into its rock

It's true that COPVs are rather common in aerospace (being the lightest pressure tank technology available). > Or has SpaceX actually loaded fuel into its rockets over 700 times? This. SpaceX has done development test cycles, and for each launch performs stage acceptance tests at McGregor Texas and both "wet dress rehearsals" (now generally skipped) and static fires at their launch pads. All of these operations involve loading and unloading helium and LOX.