Myth: 1 G barrel rolls are impossible.

Robert M. Gary writes:

You are assuming that the center of the roll makes a straight line,
that is not the case.

I'm making no such assumption.

The reality is that there will always be an acceleration of 1 G imposed on the
aircraft, in the direction of the ground. There is nothing that you can do in
an aircraft that will eliminate this acceleration, and there is nothing you
can do in an aircraft that changes its height above the ground or its path
over the ground that will not introduce additional acceleration. This is all
basic physics.