Sian Dereta-class Border Fleet Gun Destroyer

Pioneer-class Super Dimensional Fortress 4

ROBOTECH Technical Files

by Pieter Thomassen

edited by Tim Wing


  • Sian Dereta reference file
  • Sian Dereta gallery
  • Zentraedi Space Weapons gallery

Designation: Sian Dereta-class Border Fleet Gun Destroyer

Name and disposition:

  • Approximately 80,000 Sian Dereta Gun Destroyers were commissioned in the Tirolian Border Fleets and the Tirolian Special Forces.
  • These ships were built at various locations throughout the Robotech Mercantile Empire, including the Orbital Shipyards over Fantoma and the Maldara lunar yards in the Vallivarre system, and entered service from 1680 through 1899.

Ship’s complement:

  • Ships’ crew (4135 Tirolians, 65 Zentraedi),
  • Air Group (100 Tirolians, 160 Zentraedi),
  • Troops (450 Tirolians, 700 Zentraedi),
  • Life support limits are for a full combat complement and about 100 Zentraedi supernumaries (450,000 Tirolian sized men total).


  • Length: 1403 meters (main hull), 1721 meters (overall).
  • Height: 330 meters (main hull), 461 meters (overall).
  • Width: 324 meters (main hull), 518 meters (overall).
  • Mass: 22,300,000 metric tons, operational (typical).
  • Fuel Mass: 2,050,000 metric tons, maximum (typical).

Propulsion systems:

  • Main power system: Zorrelev-1005-Trafla protoculture-fueled Reflex furnace cluster. The powerplant of a Sian Dereta class vessel can nominally deliver up to 48.1 Petawatts of power, and can operate for seventy-five minutes at maximum power before overheat initiates autoshutdown.
  • Maneuvering Thrusters (12): fusion-plasma reaction thruster clusters with steerable nozzles. Located on the port and starboard top, sides and bottom halfway forward and aft.
  • Reaction-mass Thrusters (4): Varrelev SD65 fusion- reaction thrusters with protoculture energizer mounted in the upper and lower corner of the aft port and starboard halves of the ship.
  • Secondary Reaction Thrusters (15): Varrelev SD65 fusion-plasma reaction thrusters with protoculture energizer mounted in the upper and lower corner of the aft port and starboard halves of the ship.
  • Anti-gravity System (1): 30 Rastraz anti-gravity pods.
  • Space Fold (1): Nolfantom-proldarlev 835 spacefold. This system generates a hull-conformal fold.
  • Planetary Capabilities: The Sian Dereta-class has atmospheric capabilities through its reaction thrusters and anti-gravity system. The hull has sufficient structural strength for the ship to make a cold landing on it. Note that the ground underneath should be as firm as possible. The ship will float in an ocean, and this is the preferred landing method unless a land location has been extensively prepared.

Pioneer-class Super Dimensional Fortress 10Endurance and mobility limits:

The dry stores endurance was limited to about 3 years with a full crew complement, assuming no mining and subsequent replenishment, which the ships were capable of doing. The extensive recycling installations ensured that only incidental biomass losses needed to be replenished. Water stores were recycled almost completely. The hydroponics installations on board provided the crew with a steady supply of fresh foods.

The mecha consumables supplies (mainly missiles) were very extensive, and could sustain continuous combat operations for over thirty days due to the lack of missile launchers in the Tirolian mecha.

The ship-launched missile magazines sufficed for three large battles or five or more skirmishes.

The Reflex furnace could function for about 35 years at normal usage levels before before an energizer rebuild was necessary.

At full power, the main propulsion systems can nominally produce up to 611.9 Giganewtons of thrust at a minimal reaction mass efficiency profile, or as little as 14.6 Giganewtons of thrust at a maximum efficiency setting. At lower power levels, these thrusts are commensurately smaller.

At full power, the Sian Dereta can nominally achieve a maximum delta-v of 169 kps at the cruising acceleration of 0.1 gees, a maximum delta-v of 33.8 kps at the battle acceleration of 1.0 gees, and a delta-v of at most 9.5 kps at the flank acceleration of 2.5 gees. At lower power levels, these ranges are commensurately smaller.

The fold systems were not navigationally guaranteed for any single jump beyond 10 kiloparsecs. If longer voyages were required, the ship had to conduct multiple fold jumps.

The maximum sustained atmospheric speed is limited to Mach 3. A higher speed could be attained while accelerating to orbit, or in emergencies, but this stressed the engines to above their sustainable heat tolerances. The maximum hover time on the anti-gravity systems was limited only by the protoculture supplies and maintenance requirements.

Weapon systems:

  • Makral Ever 198 Reflex cannon (2): These weapons form the forward part of the ship. The two forward booms move apart slightly, then open up, and a particle beam generation then takes place between the two halves of one or both cannons. These weapons have an effective range of 300,000 km, and the effects against planets are equal to the heat and blast effects of the detonation of a fusion weapon of 48 megatons, if fired at full power. However, while there are two cannons, the powerplant can only recharge the cannons at a rate of three shots per minute in total. Though both cannons can be charged simultaneously given a large enough charge period (approximately 40 seconds), sustained fire in combat is effectively done with one cannon only. If utilized against starships, the largest vessels can be destroyed by the leakage of the beam. A direct hit will vaporize the target vessel. The weapon can also be set to a wider dispersal. While not nearly as effective as a tight beam against warships, it is capable of clearing a wide area of fighters and other mecha.
  • Makral Deim 653 particle cannon (8): As the Reflex cannons cannot be fired fast enough to be effective against multiple heavy opponents, the main anti-ship weapons are 8 heavy particle cannon. They are mounted behind movable panels in the hull of the ship. Two cannons are mounted in the tips of the upper cannon booms, two are mounted in the dorsal cannon booms, and four are mounted in blisters on top of and directly underneath the main engines. The particle beam has an effective range of 300,000 km and a full power discharge of 1.9 terajoules, equivalent to 380 tons of TNT. Although the cannon could be fired at lower power settings (and commensurate increases in the rate of fire) the highest power setting was typical in combat. The rate of fire at this setting was approximately six salvos per minute.
  • Makral Mossil 918 combination cannon (48): For centuries this combined particle beam and laser weapon has been the standard medium cannon armament on Zentraedi vessels. The laser was originally provided for pulse firings in an atmosphere, to ‘drill’ a vacuum channel through air through which the particle beam could then travel without significant loss of impact energy to atmospheric scattering. However, the laser was upgraded to be as potent as the particle beam, so that the actual discharge medium could be chosen as the optimum for the local target and environment conditions. Because of the slow recharge time of the larger weapons, this cannon turret is the most often utilized weapon system on board Zentraedi vessels. For ground support, it is the only effective weapon as the other systems are to heavy to be used around own troops. As most Zentraedi beam weapon systems, the cannon has an effective range of 300,000 km. Each full-intensity shot has a yield of 1000 MJ, and the cannons can cycle through their firing sequence once every three seconds. The exact location of these weapons varied by building yard, but the most common scheme mounted en of these weapons on or near the tips of each cannon boom, with the other 28 weapons spread over the other surfaces of the hull.
  • Deuawhaug Rasar 89 (16): A Reloadable Silo Launch System (RSLS), or as it is better known, a torpedo tube, capable of firing large anti-ship and ground bombardment torpedos. The tubes can reload in five to ten seconds, and have a 40 round magazine close-by. These launchers are mounted horizontally in the cannon booms. The missiles used are the SSA-1 Sniper (Lojredbeth Deuawhaug) and the SSA-2 Scrapper (Letkes Deuawhaug) missiles. The former is a nuclear missile with a 326 kT reaction warhead, the latter is a conventional tipped missile with a warhead of 2.3 metric tons. Both missiles are optimized for anti-ship strikes in deep space, but can be used in orbital bombardment modes or in an atmosphere.
  • Touwhaug Rasar 481 (48): A missile launcher mounted in a pop-up turret, firing anti-mecha/missile missiles, though the projectiles can guide on point-blank enemy ships. When the missiles are released they are already on their intercept vectors, or very close to them. Each turret has a reload time of 6 seconds and a magazine with a 100 round capacity. They are mounted for spherical coverage. The missile system used is the SAA-1 Granite (Gliquoun Touwhaug), a weapon with a conventional blast fragmentation warhead of 278 kg and an atmospheric range of 112 km at a speed of Mach 7.5.

Air group and mecha complement (typical for Border Fleet, 1995):

Tirolian forces:

  • 300 Bioroids,
  • 15 Assault Corvettes,

Zentraedi forces:

  • 200 Nousjadeul-Ger power armors,
  • 200 Regult battlepods,
  • 150 Gnerl fighter pods,
  • 100 Queadluun-Rau power armors,
  • 45 Glaug battlepods,
  • 4 Zentraedi shuttlecraft,
  • 12 asteroid mining craft.


  • The Sian Dereta class carries mining and manufacturing equipment for its own use; series production other than minor runs of replacement mecha is not possible.
  • The sensor outfit is excellent, and includes highly sensitive EM sensors and rudimentary foldspace scanners.

Pioneer-class Super Dimensional Fortress 15Design notes:

The Sian Dereta class was designed specifically for the demands of the Border Fleets. As such, the design differed considerably form the Zentraedi refits that had, to that time, made up the bulk of the Border Fleet strength.

A primary difference with ships such as the Queadol-Magdomilla was, for instance, the provision for a mostly Tirolian crew, with the Zentraedi giving troop and heavy labor duties labor only. Of course, due to their bulk, the Tirolian living spaces were still considerably smaller than those for the Zentraedi. This had still considerable effects on the design. Furthermore, the whole emphasis of the vessels was shifted from general duty police and space control to anti-ship and planetary bombardment taskings, in addition to greatly improved sensor performance. Moreover, great attention was given to prolonged deployments without, or with only minimal, support from faraway home bases.

As with all Zentraedi Reflex cannon ships, the front section of the Sian Dereta composed the main armament. The class was unique in carrying a double Reflex cannon, rather than a single. This was not done to improve firepower, as the powerplant could not recharge the two cannons simultaneously, but because these ships were to operate farther away from support forces and structures. The second cannon then was carried to reduce wear and tear and for redundancy. However, the advantages of this ‘spare cannon’ proved to be so small in relation to material effort of building and operating the weapon that in the successor class, the Sian Macross, the double cannon was deleted and a single cannon carried once again. The lower levels of the cannon booms carried the Zentraedi mecha hangars and some personnel quarters, with launch bays opening on the open bay in the middle of the booms.

The center section of the ship was the main structural member. The dorsal carried the Tirolian command citadel, a cilindrical structure lying on the hull, tipped aft by one of the secondary engines. The upper levels of the main section proper were dedicated to the Tirolian crew quarters and supprt systems, followed by two large and deep decks for part of the Zentraedi complement. On these levels was also the fold system hold. The lower levels were hangar decks for the smaller ships, almost exclusively Tirolian Assault Corvettes, though some Zentraedi shuttles and drone mining craft were also carried. The hangar decks were served by a large closeable ventral hatch in the center of the main section.

Pioneer-class Super Dimensional Fortress 3Flanking the main section were the two engine sections, which continued with the engines proper aft of the main section. The forward parts of the engine sections housed in their upper levels the various large installations such as the fabrication equipment and fuel purifiers. The center levels housed the Reflex furnaces and heavy engineering equipment, while the forward lower levels housed the Tirolian troops (with launch chutes for the Bioroid mecha). Aft of these primary engineering spaces were the reaction engines proper. Spreadout thoughout the ship were the reaction mass tanks for the ship and attached craft and mecha.

The Sian Dereta’s engine sections were typical of older Border Fleet designs, and were flanked by outrider bodies with the more sensitive sensor equipment. Apart from isolating these sensors from the ship proper, these sections also covered the main engineering spaces from flank attacks. The sensors mounted were rudimentary fold sensors and very sensitive EM sensor arrays. These were supported by additional sensor booms at the tip of the cannon booms.

The Sian Dereta carried a heavy armament. Apart from the double Reflex cannons already mentioned, the ships mounted eight heavy particle cannons, more than the larger Queadol Magdomilla assault cruiser. These cannons were located in the tip of the cannon booms (2), in elevating mounts on top of the cannon booms (2), and in blisters above and below the main reaction engines (4). This meant that usually five or six heavy cannons could be brought to bear on an enemy ship, given the customary Tirolian tactic of pointing the ship at the enemy to deny him a large target area. Consequently, the ventral engine cannons were relatively useless, and in the succesor design, the Sian Macross, these cannons were moved to the upper forward deck (Terran derivatives of the Sian Macross such as the Valiant class have this reversed, as those ships serve as the main capital ships and not as a design for use with numerical and technological superiority). The medium and missile defense batteries were as heavy as those on Zentraedi ships half again the Sian Dereta’s size. All this weaponry had its price, of course. The torpedo armament was minimal, certainly compared to what Zentraedi ships carried, but the heavy cannon armament compensated for this. The troop capability was reduced even more, but this too was acceptable as the Border Fleet was not intended to assault or police planets.


Pioneer-class Super Dimensional Fortress 30In 1653, the Robotech Mercantile Empire had expanded to such a size that supply lines to the outlying territories, thinly populated with troops but always under a greater threat than the inner regions, had become cumbersome to maintain. In addition, although the communication equipment allowed real-time contact with Tirol, the Zentraedi and Triumviroid headquarters there lacked in ‘on site’ awareness. What was needed was a flexible, semi-autonomous combat force capable of dealing with threats on the Empire’s rim on its own or, at least, of sending a warning and holding the line until reinforcements arrived.

Built to fulfill this need were Border Fleets. Unlike the regular Tirolian and Zentraedi fleets, these fleets were made up of mixed Tirolian/Zentraedi crews, operating custom-designed ships with a large amount of autonomy. The Triumviroids commanded the ships and Task Forces, clone forces provided a fast reaction force and Zentraedi troops provided the heavy troop component. Because these forces had to operate in distant areas without the certainty of fast reinforcements the troops were equipped with a qualitatively superior weapons mix compared to the core imperial forces. For instance, the Zentraedi Borderers, as they were often called, were equipped with 7 times the normal allotment of Glaug pods, and were also among the first units to receive Quaedluun-Rau power suits.

This qualitative edge also extended to the Border Fleet ship designs. The Border Fleet’s largest ship was designed as the Sian Dereta class battleship, but after the designers recognised that its mission profile and outfit were different from all ship classes that had gone before the designation was changed to the new ‘Gun Destroyer’ category, incidentally effectively deleting the battleship designation. As the first class to be so named, the Sian Dereta set the standard for these ships, a standard which these days becomes more and more the standard for all capital ships. This includes Reflex cannons as the main weapons, supported by an anti-ship cannon armament heavier than a Queadol Magdomilla assault cruiser. The medium cannon and missile batteries were as strong as the Thuverl Salan’s, a ship almost half again as long as the Sian Dereta.

The first Border Fleet ships were converted Zentraedi vessels, and the first Sian Dereta prototype entered service around 1680. The Sian Dereta served with the Border Fleet as the local flagship, usually leading a task force of Seron Thoun battlecruisers and a number of Tou Redir scout vessels (and later, Tou Salaam class Exploration cruisers), all accompanied by one or two Quiltra Queleual vessels in the supply configuration. These task forces each patrolled their area of the Empire’s border sectors, scouting for threats and generally giving acte the presence for the Tirolian Empire. With an average of one Sian Dereta and five Seron Thoun ships in each task force, the battlegroups were highly potent, numbering an average of seven Reflex cannons between them. In addition to the larger than usual amount of anti-ship weapons this gave the task forces the firepower equivalent of several Zentraedi battlegroups of equal size. However, while the troops stationed on the ships were fast and hard-hitting, they were not as numerous as those on regular Zentraedi ships, and thus the Border Fleets were limited frontier patrol duties and fast strike missions only. Conquest and large scale policing were not part of the Border Fleet tasks and were relegated to the main Zentraedi forces. This ship and troop make up of the Border Fleets, combined with the close Tirolian supervision through the Triumviroid commanders, made such a task force ideal for special forces duties, and the Tirolian fleet command appropriated several Sian Dereta and Seron Thoun groups after construction and employed them as such, though never in numbers exceeding 97 such task forces.

The Sian Dereta continued in series production for near two centuries, with an estimated 80,000 vessels of the class built. In the final years of the 19th century, the Border Fleets were at strength, and attrition could be met for the foreseeable future by ships then under refit and repair, and by replacing losses with Seron Thoun craft on a temporary basis. Due to the independent nature of the Sian Dereta, it was not until about a century later that the class was becoming a thinly spread design whose replacement parts were no longer in production and whose stocks were dwindling. Rather than rebuilding the production lines, a new and updated design, the Sian Macross, was prepared and construction begun on prototypes, with the goal of replacing the Sian Dereta on a one-to-one basis over the next five to seven decades. However, protoculture depletion and the disaster regarding Zor made this plan impossible. The Sian Deretas, like all Tirolian ships, gradually lost power in the first two decades of the 21th century, and were destroyed outright or stranded in place at their farflung postings.

Pioneer-class Super Dimensional Fortress 50As an historical note it should be mentioned that the United Earth Expeditionary Force used the outer hull of one such ship, captured (as a total loss) in 2015, as the outer hull of the SDF-3 UES Pioneer, which was built to the exterior dimensions of the Sian Dereta class. The Pioneer thus almost perfectly mimicked a Sian Dereta, as part of a ploy to close with Tirol before being fired upon. As another point of interest it must be stated that the Border Fleet designs lend themselves admirably to adaptation as capital ships for Terra and her allies. This was due to the heavy armament on a relatively small hull, coupled with the large troop capability created by replacing full size Zentraedi with micronian sized troops.



Robotech (R) is the property of Harmony Gold. This document is in no way intended to infringe upon their rights.

Original artwork by: Tatsunoko Production Co., Ltd.

Acknowledgement is extended to Peter Walker, Pieter Thomassen and Robert Morgenstern of the unofficial Robotech Reference Guide. Peter Walker, Pieter Thomassen and Robert Morgenstern are given credit for all quotes and paraphrasing of the unofficial Robotech Reference Guide that has been utilized in this publication. 

Images from – Robotech II: The RPG, Robotech Expeditionary Force Field Guide (March 1989)

Content by Pieter Thomassen, edited by Tim Wing

Copyright © 1999 Robert Morgenstern, Pieter Thomassen, Peter Walker; 2016 Tim Wing