drobbo

Gravity gradient stabilization is also known as tidal locking, which is what keeps the same face of our moon facing Earth, so its effects are actually very noticeable under the right circumstances. As for what real craft do, this technique has been used on multiple spacecraft in the real world and was first successfully demonstrated in 1967. It is being considered as a stabilization method for the proposed CubeSats. Also, moment of inertia is dependent on the amount and distribution of the mass, not necessarily the shape of the spacecraft. As it is dependent on gravity, the closer the craft is to the centre of gravity, the more torque that can be generated by this technique. However, as the planets in KSP attempt to mimic the gravity of real-world planets (Kerbin=Earth, etc), their gravitational fields are unrealistically massive for their size, which allows for much lower orbits and much greater available torquing power. This is all assuming you wanted it to be used completely realistically, which not all the physics in KSP mimic. I agree that being able to tell the SAS system how you want it to orientate is a better alternative, but the dev team has listed exactly this idea in the What Not to Suggest sticky, so I thought I'd propose a different idea.

Say that you have a station or satellite in orbit around a body (eg. planet) and you want the orientation of the station/satellite to remain the same with respect to the body, not the absolute frame of reference. For example, if a space telescope was added to the game, under the current behaviour of the SAS systems, you must choose between either a fixed orientation (SAS on) or free-moving orientation that is near impossible to match to the rotational velocity of the craft. The fixed orientation would not work for a telescope that is supposed to point in a certain direction, such as directly outward from the body it is orbiting, as at the opposite side of the orbit it will be facing directly towards the body. With SAS disabled, it is near impossible to have the rotation of the craft align with the rotational speed and direction with respect to the body it is orbiting. Another way of examining this problem is with a manned (Kerbaled?) space station with a central column and radial crew modules. If you want the central column to always remain vertically aligned, the station must rotate with respect to the body it is orbiting. This form of attitude control is commonly achieved in the real world with gravity gradient stabilization. This technique can be greatly simplified into the following: a spacecraft in orbit around a body (mass of body must be significantly larger than craft) will attempt to align the axis of minimum moment of inertia vertically. Using the space station example above, if its minimum moment of inertia is aligned through the central column and the force of stabilization great enough, the station would be rotated with respect to the body as it orbited the body so that it was always pointing away from the body's surface. I can imagine that this would be particularly annoying if all craft in orbit about a body were affected by this in-game, but would be particularly useful for space stations, comms satellites, solar panels and the like. Therefore, adding some part that could be attached to a spacecraft so that this effect could be used would enhance the orientation capabilities of spacecraft in orbit, as well as creating a more engaging gaming experience.