Equivalence principle of space ?doesnt really apply only when a moving object has reached steady State?

Answer 1

The equivalence says that an object being accelerated is equivalent to an object in a gravitational field. If it's accelerating, it's not at some steady state.

http://en.wikipedia.org/wiki/Equivalence_principle

Answer 2

The equivalence principle isn;t really about space. Its about gravity. It states that a uniform gravitational field is indistinguishable from an accelerating reference frame. It does not matter if objects are accelerating within the frame, and a momentary comoving frame can be applied to get a local reference frame for objects.