After that, I think we hit a technological wall, you can almost see the asymptote after the mid 70's. Though I think Space X is poised to knock some things over again if they succeed in their "cheap but reliable" approach, which basically amounts to attacking the problem as if it were a commercial airline engine as opposed to a rocket engine, and subjecting it to those standards of rigor. But that's a different kind of progress.
More on topic, this article completely fails to support it's hyperbolic "costs thousands of lives" subtitle.
