Here is something that my group has been asking me about. This is what I wrote up for them.

External Inertial Damping Field (a.k.a. the parking break)
SU cost: 1 SU per section of the ship.
Power: 1 power per round when active.
The External Inertial Damping Field is simply the parking break on a starship that is installed on many federation starships. This will keep the ship from drifting in space dock or while parked in the fleets navel yards and even when in the surplus depots around the galaxy. The parking break can be run off a simple auxiliary reactor.
The External Inertial Damping Field will prevent the ship from moving or even going to warp yet the simple drift of the thrusters firing seams to be compensated into the systems. The impulse engine is inhibited to triple the power to move the ship at any impulse speed.
If ships like the Galaxy-class and other, starships like having two sections a star drive and saucer section each would have an External Inertial Damping Field installed in both. For an example, if a Galaxy-class parked in the spacedock it would cost 2 power for the two sections of the starship. Where as a starships like the Defiant-class, a small single hull vessel with not separation system would cost only 1 power for the single section of the ship while parked.
This system only works when active in a gravitational field and has little effect in the space between the star systems. Instead of the External Inertial Damping Field an Inverse Warp Field would anchor the ship in deep space.
If another vessel is toeing the ship with an External Inertial Damping Field engaged the toe vessel requires twice the amount of power to pull in the impulse engines, structural integrity fields and tractor beams. A ship pulling the vessel with the External Inertial Damping Field activated will have a strain on its system in the engines, structural integrity field and tractor beam and checks will be necessary to see if there is damage to the ships systems. A difficulty test of 8 plus one per size of the vessel being toed for each round. If two or more ships are toeing the vessel with the External Inertial Damping Field active, the difficulty is cut in half per ship and if the ship is larger than the one being toed.

Failure of the tests for the impulse engines
1 – the impulse engines sustain half their SU’s in damage. (The impulse engine will shut down during the round the ship and the ship loses propulsion and speed.)
2 – the impulse engines cause 10 SU’s damage to the hull both interior and exterior
3 – damage to the EPS feed causing a plasma fire. (1% of the engineering staff are hurt and/or killed at the GM’s discretion fighting the fire or the initial explosion.) The impulse engine shuts down.
4 – the impulse engine over heats and shuts down with the safty systems over riding and there is no damage.
5 – the impulse engine tears loose of the hull and causing addition to the cost in SU’s for the engine and 5 SU’s of damage to the hull including both the hulls.
6 – impulse engine explodes causing times two the SU’s of the engine.

Structural Integrity Field failure
1 – 2 – SIF can not cover the strain and the sustains 10 SU’s damage to both the inner and outer hulls.
3 – 4 – the strain on the SIF cause either the Main or one of the backups to shut down after the strain. The SIF that shuts down and sustains half its SU’s in damage.
5 – 6 – The SIF burns up sustaining one third of the damage to the SU’s.

Tractor beam failure
1 – 2 – the Tractor beam burns up and cause 2 SU’s of damage to the tractor beam beyond the cost of the tractor beam.
3 – strain on the Tractor beam overloads the computer system and shuts the Tractor beam and requires a DC check of 10.
4 – 6 – the Tractor beam tears loose from the hull. Causing additional 5 SU’s of damage to the hull including the hull.