The Thunder class was designed originally to act as garrison vessels on starbases. When the Savant project began, however, room for such a ship was provided in the designs so that a dedicated combat vessel would be able to escort the massive carrier when reienforcements would be unavailable. To that end, a special launch-bay has been built into the Savant class where a single Thunder can be fit in.

The Thunder has no shuttle craft, but is able to land on and take off from planets and other large objects. With a weapons load-out identical to the defiant, though considerably smaller, there is almost no room for personal comfort. Only half the bunks needed for each person are available, forcing a hot-bunking technique into use. The small galley only has a pair of synthisizers capably of producing simple dishes that meet the body's requirements. No sick bay is present, though crew quarters can be converted into small versions if needed.

Though the Thunder class's primary duty is to escort its mother ship, they are also used for extended away missions when it would be unwise to take a Savant class in. With that in mind, all Thunders being sent out of the galaxy are equipped with a cloaking device purchased from the Klingon Empire. Also, enough room for a squad of marines is provided, but no other form of security is present.

The Thunder class assigned to the USS Serenity is a fairly new model, the USS Hammer. Traditionally, either Captain Floten or Commander Calps would command this vessel, however, any member of the senior staff is authorized to take the ship out. Normally, junior officers crew the ship, along with experienced NCOs.