The more gravity the slower time is, relative to a distant observer moving faster than us.
The greater the speed the slower time goes etc.

As we watch a body at high speed away from our gravity well...
it seems only obvious to me that we would see it seemingly moving faster over "time" compared to our faster time down here since we are movin slow and on top of a large gravitational mass. It would also stand to reason that the acceleration would be a constant but very small unless speeds very near the speed of ight were achieved.

What have I missed? Why do assume an unknown force is causing our robotic spacecraft to accelerate ever so slightly?