Actually, you need mass to get inertia and gravity and furthermore you get inertia and gravity whenever you have mass. ;¬)
I'm going to post in good faith what I hope will be a post that clears up a few ideas about this topic and amounts to something of a "primer" on mass and the 'laws of motion'.
Any 'physical object' that you can interact with has mass, this mass is directly related to how many atoms make up the object, what the 'atomic weight' (bad historical choice of terms, there, by the way) of each atom is and how widely separated the atoms are (this last is density / volume).
All objects (masses) attract each other in the same way that most people are familiar with magnets doing, however, gravity is a very weak force compared to magnetism and the two nuclear forces (which hold atoms together, by the way). This means that only very large masses have easily human-observable gravitational fields - e.g. the glasses on my table are technically attracting each other but that attraction is easily overcome by friction from the polished ceramic (low friction!) surface of my table (and totally overwhelmed by the attraction of the Earth or even the table itself).
All objects also resist changes to their velocity (i.e. they resist acceleration), this is known as 'inertia' but it's not really a separate force or effect, per se, simply part of the nature of mass.
Unless acted on by a force, an object will continue its existing vector (i.e. speed and direction) and the force required to apply a specific acceleration to a given object is directly proportion to the mass of that object, also with a given acceleration and a given force you have an implied mass. => F = m.a
A couple of confusions result from 'layman' usage of these terms, as follows:
"Gravity" is commonly understood as "being pulled down to the floor" and "weight" is used as a synonym of mass (in reality, weight is a force resulting from the acceleration of an object in a gravitational field, towards the centre of that field).
When people talk about "artificial gravity" they tend to mean "some way of making the floor feel like the floor" and this is easily achieved by ensuring a force towards the 'floor' (e.g. rotating a structure and having the 'floor' near the outer part of the structure and set perpendicular to the force).
When people think 'zero-g' they often assume this means 'little or no mass' on a subconscious and intutive level, leading people to mishandle massive moving objects, potentially.
So-called "inertial damping" is actually "acceleration protection" - you need to protect passengers from sudden changes in acceleration that result from manoeuvring or impacts. It's called "inertial damping" because if you were to somehow stop mass from resisting such changes then you could, perhaps, get very small, even functionally zero, forces applied to those masses as a result of the undesired accelerations. The very same theoretical ability would also allow you to, perhaps, create 'artifical gravity' without applying a force (such as by accelerating the object the passengers are in).
In other words: "inertial damping", "gravitics","artificial gravity (in most cases)" and "anti-grav" are all the same basic idea.
