For the big-rip scenario to be expected, wouldn't the expansion of space have to have an accelerating rate even between two points of the same distance such as 70k/sec/mega parsec/year (or any other time frame, maybe 13.7 billion years)?

With the observed expansion rate of 70k/sec/mega parsec, the space between two objects, ie. the Sun and Earth is expanding, but due to gravity they are moving towards each other at a faster rate than that expansion, so the system's over size then only remains constant because the lateral inertia has us in orbit. I imagine that if the Earth left a trail on medium of space as it orbited the Sun, we'd see a spiral moving outward from the system as space expanded.

If space wasn't expanding, I bet the Earth would need to be moving a wee bit faster laterally to maintain this size of an orbit. That math is beyond this mere kindergarten teacher in Thailand, I'm afraid.

I don't see gravity as affecting the expansion of space at all, only the curvature of the space, hence the motion of objects through the medium of space and their gravitational interaction with each other. The expansion of space should therefore not transmit any inertia to the objects that are seemingly accelerating apart from each other within the medium, which is why objects can be moving faster than the speed of light relative to one another, but not in relation to the medium of space.

Which type of rate has been observed? I've only heard the current rate of 70k/sec/MP on astronomycast. Is that rate expected to be increasing ie.. perhaps 70k/sec/MP/13.7 billion years? If so, hello, big-rip! I imagine it shouldn't be too long till our observations can rule one out if they haven't already.

edit: previously had expansion rates at 20k per... must have misheard the podcast, or just getting old. thanks speedfreek for the correction