Every starpilot knows that if you fly through a planet’s gravity field whilst in hyperspace, your ship will immediately be pulled out back into realspace. The Empire used this fact to create the Immobilizer 418, more commonly known as the Interdictor Cruiser.
From a distance, the six hundred metre Interdictor looks like a small Star Destroyer, but on closer inspection, it is something else entirely. The Cruisers are notable for the four great globes located on its hull; two on top, and two on the underside. These house the Cruiser’s four gravity well projectors, which are used to prevent ships from entering hyperspace, or to pull them out into realspace. The projectors are powered by an artificial gravity-well generator.
Imperial fleets normally have one or two Interdictor Cruisers, which are usually stationed on the perimeter of the battlefield to stop the enemy escaping. There are also twenty quad laser cannons if the Interdictor needs to fend off capital ships. Once on the perimeter, Interdictor captains had a good view of the battlefield, and could position their gravity wells with great precision. They had, otherwise the enemy could escape while the gravity wells are recharged and repositioned.
This brings up the Interdictor’s greatest disadvantage. If the wells are wrongly placed, they need at least a minute to recharge. In this time, a quick-thinking pilot could easily engage his/her hyperdrive and jump out of the area. But the hull of the Interdictor has been favoured by Imperial bureaucrats, who like it because of its resemblance to the Star Destroyer. The hull is also good because it can be modified for special missions with the addition of a variety of weapons.
Thrawn say the usefulness of the Interdictors during his campaign. Actually, one of them managed to pull Luke’s X-Wing out of hyperspace, and Thrawn’s personal flagship, the Chimaera, almost captured him. But the young Jedi used a pair of proton torpedoes to take out the Chimaera’s tractor beam projector, and he jumped out of the system.