The early history of the Derf Class is an amazing story of near abandonment. The Derf was designed as a destroyer leader (Daring class), but improvements in small ship sensor technology during the Four Years War rendered this type of ship obsolete. It was then re-roled as an exploration cruiser (Derf class), but the decision to produce further ships of the Constitution and Anton classes meant that it could not fulfill that role either. Finally the USS Derf was borrowed for a demonstration of the buoy tender concept. This demonstration was so successful that serial production of the Derf was ordered immediately and eventually totaled 600 vessels over a period of 35 years. Few vessels in Starfleet history have achieved either that level or longevity of production and it is certain that had the class been adopted in either of the other two intended roles it would not have gotten anywhere near either figure.

The Derf class tender has been operational in Starfleet for more than 25 years. When it entered service in July of 2256 (1/9807), the Derf class marked a new concept in navigational beacon repair. Before its introduction, marker buoys and navigational beacons had to be retrieved and returned to a repair facility to be serviced. Derf class tenders eliminated this need because they carried repair facilities on board.

When a Derf arrives at a malfunctioning beacon’s location, a shuttle uses a tractor beam on the beacon and tows it into the lower hull, which is the tender’s main repair facility. The beacon is then placed on an assembly line and repaired robotically. When the work is finished, the shuttle tows the beacon back into the spacelanes, and the Derf moves on.

Although the Derf is not designed as a fighting vessel, it is capable of aggressive defense. Most repair missions take place along the borders between the major powers, where the chances of encountering enemy ships is very high. Because of this high risk, the Derf is armed with medium-range phasers.

This protection does not prevent them from falling prey to enemy ships. In February 2263 (2/0702), the USS Acropolis responded to signals from a malfunctioning marker buoy. As its shuttle neared the beacon, a Klingon warship appeared and opened fire before defensive action could be taken. The volley crippled the Acropolis’ engines, and the tender was boarded and towed into Klingon territory.

Intelligence later discovered that the beacon had been planted by Klingon operatives to entrap the repair tender. It is theorized that the Klingons gained technical information concerning robotics and repair techniques that they lacked, but it is not known just what gain this action brought them in the overall situation. Some analysts believe that study of the robotic repair systems will make it possible for Klingons to alter the functioning of navigation beacons robotically, creating potential havoc in border spacelanes. However, a crash program of buoy upgrading and fitting of encryption systems, which occupied the entire fleet of Derf’s and many other ships, prevented this from happening.

The design of the Derf evolved over a number of Marks. The Mk II would have offered improved impulse and warp drives compared to the Mk I, but a further improved Mk III was designed while the early Mk IIs were being tested. All Mk IIs were updated to Mk III specifications to keep the number of variations within the fleet as low as possible.

In 2285 (2/22), a number of Derfs were taken in hand for conversion to a new Mk V standard. The increase in tensions on the Klingon frontier meant that Derfs now required an armed escort in order to operate safely. The Mk V refit introduced improved shields and enhanced weapons in order to allow the ship to operate without escort in most situations. Not all ships have been refitted to this standard, but all new production was to this standard until production ceased. The Derf class was built at Merak by Chandley Works, Ltd. Buoy maintenance is now carried out by civilian ships in most areas of the Federation, but Starfleet maintains a fleet of Derfs in both active service and reserve to maintain those in more dangerous areas.

The Derf class is now a surprisingly sought after posting amongst many young officers. The reasons for this are varied. All active ships are assigned to border areas, so there is a chance to see the “enemy” in the flesh, it (in Mk V form) is a tough ship to best in combat, and perhaps most importantly it is one of the few classes still in service from the “classic” era of starship technology.

Of the 691 Derfs built, 8 Mk Is, 351 Mk IIIs, 61 Mk IVs and 72 Mk Vs remain in active service, and 38 Mk Is and 25 Mk IIIs are in reserve fleets. Two Mk Is, 2 Mk IIIs and 2 Mk IVs are used by Starfleet Training Command; 12 Mk Is, 8 Mk IIIs and 2 Mk IVs have been destroyed; 1 Mk III has been captured by the Klingons; 1 Mk I, 3 Mk IIIs and 1 Mk V are listed as missing; 4 Mk Is, 4 Mk IIIs, 3 Mk IVs and 2 Mk Vs have been scrapped; and 2 Mk Is and 1 Mk III have been sold to the private sector.