TRM Magnus V

TRM Magnus V at sea during the 1948 Colonial Panic
Class overview
Name:	Magnus V
Builders:	Orten & Sogard Skipsbyggingsfirma
Operators:	Trinovantum
Preceded by:	Vegard III Class
Succeeded by:	Halvard I Class
In service:	1930-1962
Building:	0
Completed:	1
Cancelled:	1
Active:	0
Retired:	1
General characteristics
Type:	Battleship
Displacement:	49,600 tonnes
Length:	249.9 meters
Beam:	32.3 meters
Draught:	10.1 meters
Installed power:	20x three-drum boilers, 56,000 shp (42,000 kW)
Propulsion:	2 shaft; 2 sets of geared turbines
Speed:	23 knots
Range:	11,000 km at 12 knots
Complement:	1750
Armament:	3x triple 460 mm guns 8x twin 152 mm guns 6x single 120 mm anti-air guns 4x octuple 40 mm anti-air guns 2x 622 mm torpedo tubes
Armour:	460 mm

The TRM Magnus V Håkonsson was a large Trinovantan battleship built during the Third Ostlander-Trinovantan War and commissioned after its end. In order to comply with stringent size and displacement restrictions, the ship featured a unique armament scheme of two forward turrets and a single amidship turret. During construction, its design was modified to account for lessons learned from naval combat during the war, most notably the surprising effectiveness of anti-ship aircraft. It carried the largest and most powerful naval rifles of any Trinovantan warship ever constructed, and among the most powerful of any battleship ever constructed.

It first saw action during the 1948 Colonial Panic where it participated in sea control and shore bombardment against the rebelling factions. After the initiation of the Fourth Ostlander-Trinovantan War, it was recalled from its colonial flagship duties and rejoined the South Fleet. It primarily served as a heavy escort element for transport convoys and other ships of importance. Notably, the Magnus V engaged and sank the Ostlander battleship SKS Admiral von Alder during one such action.

Shortly after the conclusion of the Fourth Ostlander-Trinovantan War, the Trinovantan Navy began downsizing its fleet in an effort to cut expenses. As part of this effort, the Magnus V was put into the reserve fleet in 1958 and slated to be scrapped. As the second most modern class of battleship at the time, it was last on the list of large vessels to be scrapped. It was stricken from the register in 1962.

While it possessed unmatched firepower and protection for its time, the Magnus V’s design reflected the older and ultimately obsolete naval tactics of the Trinovantan Navy before the Third Ostlander-Trinovantan War. The ship’s lack of speed and operating range, while acceptable for short-range sea control sorties and battle-line engagements it was intended to participate in, rendered it ineffective in the high speed escort and raiding roles that came to dominate capital ship usage during the Fourth Ostlander-Trinovantan War.

Development

The Magnus V was intended to be a class of ship “second to none” to combat Ostlichtor’s super-dreadnoughts, including a new 40,000 tonne design with an armament equal to any in the Trinovantan fleet. Trinovantan capital ships had traditionally enjoyed an advantage in engagement range and firepower over their Ostlander counterparts. In order to preserve this advantage, a significant increase in firepower was considered to be crucial to any future ship design. To this end, the Magnus V was to be outfitted with new weapons far more powerful than the 380mm naval rifles favored by Trinovantum at the time.

However, concerns were given to the ever expanding size of the Trinovantan navy’s warships. The earlier Halvard IV class’s prodigious size had already proved to be highly limiting in terms of where the ships could base from, being too large for many military docks to effectively service, with several dock facilities needing to be expanded in order to be able to service these ships. This proved to be a sizable “hidden” cost to operating the Halvard IVs that the government did not want to repeat. As such, it was mandated that the ships of this new class were to be no larger than the Halvard IVs in dimension or displacement.

The requirement to mount heavier armament on a platform of limited size was what drove the novel armament arrangement of the Magnus V. Instead of the usual arrangement of turrets forward and aft of the ship’s superstructure and machine spaces, they were arranged with two turrets fore and a single turret amidship, with the engines and machine spaces in the aft sections. This concentration of the armament in a smaller section of the ship reduced the critical protected area of the ship, allowing for a very well armed and armored vessel to be constructed within the limiting size restrictions.

Development began in early 1918, with the first ship being laid down in 1921. However, the outbreak of the Third Ostlander-Trinovantan War later that year resulted in construction being paused. Eventually, the other planned ship of the class was canceled. The Magnus V was allowed to be finished to a modified standard with lessons learned from the Third Ostander-Trinovantan War. This resulted in a ship that possessed numerous novel design characteristics not present on preceding Trinovantan ship classes. Some of these design characteristics, most notably the all-or-nothing armor scheme, would be carried forward on the following Halvard I Class battleships.

Design

General Characteristics

The most immediately striking feature of the Magnus V is the placement of the main battery, with two triple turrets forward and one amidships. This concentrates the armament together in a relatively small space, compared to a conventional ship layout, reducing the required protected volume. While the overall hull size on the Magnus V was limited, it was by no means a small ship. At 249.9 meters in length and 32.3 meters in width, it was only marginally shorter than the Halvard IVs and slightly wider. The initial target displacement of the ship was intended to be 48,000 tonnes, but the final design reached a displacement of 49,600 tonnes. However, the margins for displacement were not as stringent as those for its physical dimensions, and this was considered to be within acceptable limits. Uniquely, the Magnus V featured a transom stern. This increased the high-speed hydrodynamic efficiency of the ship and would later feature on the Halvard I class of fast battleships. As time passed, this feature would become increasingly common on both Trinovantan and foreign-designed ships.

Though it possessed a relatively high length/beam ratio of 7.74 as well as a solid hull form for high speed cruising for a warship of its time and class, the Magnus V was not intended to be a fast ship. In this case, the designs given were intended to make it more stable and efficient during extended high-speed cruising as well as to reduce the needed power to reach its top speed of 23 knots. Higher speeds were seen as unnecessary, as the Magnus V was intended to act as part of extended battle lines as per the naval doctrine of the Trinovantan Navy before the Third Ostlander-Trinovantan War. In this role, having a significantly higher speed than the battleline would not only deprive the vessel of support, it would deprive the battle line itself of a powerful lynchpin to their formation. In this, the ship was generally well regarded as a stable gunnery platform. However, its seakeeping in adverse conditions was not as desirable, with a consistent complaint being how wet the forward deck was due to its lack of bow sheer.

In order to mitigate the effects of sailing in the colder northern sea, the vessel was equipped with steam heating systems in key interior and exterior areas as per most modern Trinovantan ships. Asbestos insulation was used extensively to mitigate temperature reduction and keep stations workable for the crew.

Armament

Testing rig for a 460mm Model 1922 naval rifle

The primary armament of the Magnus V was nine 460mm Model 1922 L/45 naval rifles, split between three triple turrets. At the time of construction, these were the most powerful naval rifles ever made and would remain the most powerful naval rifles ever equipped to a Trinovantan ship. They fired a 1506 kg capped armor-piercing shell with a 35.7 kg shellite bursting charge at a muzzle velocity of 762 m/s. During proof testing these shells penetrated a 500 mm thick armor plate at a simulated range of 20 km. This was the thickest plate available for testing and as such demonstrated an ability to defeat all known armor schemes at expected combat distances, including even that of the Magnus V itself. As such, plates of greater thickness were not constructed and it was declared that any current or speculated future ship within 20 km of the Magnus V would be in mortal danger of its main battery. A high-explosive shell was also provided for shore bombardment. This shell was heavier than the APC shell, weighing 1808 kg with a 198 kg Picric acid bursting charge. When at its maximum elevation of 40 degrees these rifles could strike a target up to 40 kilometers away with their armor piercing shells. Shells could be moved from the protected magazines up to the turret and loaded in between 55 to 70 seconds. The guns had to be set to 3 degrees elevation during this process. 85 shells were provided for each gun, resulting in a total of 765 shells.

One of the eight 152mm gun turrets

The Magnus V’s secondary armament was a more conventional battery of 152mm Model 1921 L/50 naval rifles, though these were placed in two sets of four twin turrets instead of the usual casemate or single open mounts common on preceding designs. This allowed each gun to cover a much larger area than previous mounting systems. This was of particular importance for the Magnus V due to the unique arrangement of its primary weapons. With two sets of turrets on either side of the forward tower and rearward machine spaces, almost every angle of approach can be covered by 4 turrets and thus 8 guns. Capable of being reloaded in approximately 12 seconds, these more rapidly firing guns were intended to augment the ship’s firepower against subcapital ships. The original specification for the 152mm Mk XXII gun mounts was for a maximum of 30 degrees, however this design was revised during the war in order to allow the secondary battery to target aircraft. As completed, these guns were capable of elevating from between -5 and 60 degrees. The increased elevation over previous mountings reflected the sudden realization of the threat that aircraft could pose to ships that came after the Third Ostlander-Trinovantan War. Though this would ultimately prove to be a forward-thinking idea, with many later Trinovantan ships carrying dual-purpose weapons, these turrets were not adequate for anti-aircraft work. The turrets were slow both to rotate and elevate, complicating the tracking of fast moving aircraft, and the gun's rate of fire was too low to sufficiently saturate aerial sectors.

The guns fired a 45 kg semi-armor piercing capped shell with a 1.7 kg bursting charge at a muzzle velocity of 898 m/s, for a maximum range of 23.5 km at 45 degrees elevation. This ammunition was capable of penetrating approximately 80 mm of belt armor at 10 km or 50 mm of deck armor at 20 km. A high explosive round was developed for the weapon, with the same 45 kg weight but a 3.6 kg bursting charge, for anti-aircraft use but was not carried beyond the ship’s initial service years. 100 rounds were carried per gun as standard for a total of 1600 rounds carried, the vast majority of these being SAPBC with a small number (generally around 80) of illumination and smoke shells carried for specific situations.

A 120mm Model 1925 AA gun being reloaded during the Magnus V's sea trials

The original anti-aircraft armament was to consist of six single quick-firing 120mm Model 1925 L/40 dual-purpose anti-aircraft guns. These guns had a rate of fire of between 8 and 12 rounds per minute with a power rammer to assist in reloading the guns when trained to high elevations. However, sustaining this rate of fire would turn out to be impractical, as the heavy weight of the fixed ammunition (34.5 kg) would quickly fatigue the loading teams. The 22.7 kg high capacity shells carried a 3.1 kg explosive payload which would inflict devastating damage to any aircraft hit by these weapons. These shells had a muzzle velocity of 750 m/s, and at 90 degrees elevation were capable of striking targets flying at over 9000 meters. Only 100 rounds were carried for each gun, for a total of 600 rounds. In the mid 1940s, these guns would receive new high-explosive proximity fuse ammunition, which carried a smaller explosive charge but helped to alleviate some of the weapon’s other faults in the anti-aircraft role.

An octuple mount for the 40mm Model 1928 anti-aircraft gun

While considered extensive for the time, experience from the Third Ostlander-Trinovantan War indicated that this anti-aircraft armament would not be sufficient. In particular, the advent and use of torpedo bombers whose low altitude attack approaches were vastly different from the expected air threat of high-altitude bombing that the original AA armament was intended to deal with. As such, during construction the anti-aircraft armament was augmented by four octuple 40mm Model 1928 L/39 anti-aircraft guns. These guns were essentially a revision of the 40mm Model 1915 L/39 anti-aircraft guns to make them suitable to be fitted to a high-density 8 gun mount. Despite being derived from an existing weapon, the development of this weapon and its accompanying mount was a problematic and protracted affair. The gun mechanisms were relatively complex and required skilled, careful maintenance as a result. Jams and stoppages were a recurring issue with these weapons during their service, though increased familiarity would help to reduce these issues over time. Each of these guns were capable of a rate of fire of 115 rounds per minute, for a combined rate of fire of 920 rounds per minute per mount. In the octuple mountings, each gun is fed from a 140 round ammunition canister that can be replenished by 14 round linked belts. These faster firing but short range guns would make approaching the Magnus V a much more dangerous than it would for any preceding Trinovanatan battleship. 11,900 rounds per station were carried, for 47,600 rounds in total.

Ahead of the forward ‘A’ turret were two broadside submerged 622 mm torpedo tubes, the largest torpedoes put on any Trinovantan ship. These 2585 kg oxygen-enriched air propelled torpedoes carried a 337 kg TNT explosive charge. This heavier explosive charge was intended to defeat the increasingly effective anti-torpedo protection being developed for modern capital ships. They could be launched with two different range and speed settings, 35 knots with a maximum range of 13.5 km or 30 knots with a maximum range of 18 km. At the low speed setting, the maximum range of the torpedoes is within what could be expected of a battle line engagement. As such, it was expected that these torpedoes would be used to disrupt enemy battle lines during these engagements. 16 of these torpedoes were carried.

Protection

The Magnus V was the first Trinovantan ship to adopt the all or nothing armor scheme. This decision was made in parts because weight efficiency was a major concern for the Magnus V due to the restrictions on its hull size and displacement but an additional concern arouse regarding plunging fire after naval battles that occurred during the 4th Peninsular War in which the extended engagement ranges of modern ships caused critical damage from long range shellfire striking underprotected deck armor to become much more common. This armor scheme sacrificed the protection of outboard areas of the ship to concentrate armor over critical zones like machine spaces and ammunition magazines. The 4th Peninsular War demonstrated that capital ships were generally able to survive even extensive damage to non-critical areas. Ammunition magazines, propulsion, command and control, and fire control were considered the most critical components worth protecting in descending order of importance. Damage to these systems would either pose a lethal risk to the ship, or degrade its capabilities such that lethal damage could more easily be dealt to the ship. As such, it was determined that the areas containing these systems should be protected at the expense of other areas of the ship. For simplicity and weight efficiency, it was ideal to concentrate all of these critical components into a single area which could then be given all affordable armor.

In a perfectly designed “all or nothing” style ship, all critical components would be located within a single heavily armored “citadel” located in the center of the ship. The remainder of the ship would have insignificant armoring, such that armor piercing shells would not be able fuse upon striking these noncritical sections. These noncritical sections would be separated from the citadel via thick protective bulkheads, which would be sealed during combat conditions. The armored citadel would have enough reserve buoyancy to keep the ship afloat even if every other section of the ship was flooded. This would ensure that any attack striking away from the citadel would be ineffective, regardless of the power of the attack, and that the critical areas necessary to the function of the ship would be armored to such an extent that they would be able to resist the attack of any equivalently sized opposing ship.

A cross section of a cemented steel plate, similar to what is used for the TRM Magnus V's belt armor

In practice, almost no ships followed the “all or nothing” concept perfectly and the Magnus V was no exception to this. However, even a partial usage of these concepts, alongside of the Magnus V’s unique armament arrangement, allowed for a level of hull protection that was unmatched by any ship preceding and even many that came after. Primary citadel protection was provided by a 380mm face-hardened cemented steel belt inclined at 25 degrees. Inclined belts were trialed on the Halvard IV class of fast battleships and theoretically gave their 305mm belts a similar line-of-sight thickness to the uninclined 330 mm belts that were standard for Trinovantan battleships. The Magnus V’s belt, being both thicker and having double the angle of inclination, would give it protection akin to that of a 420 mm belt against close range fire. At an engagement range of 10 km and an expected fall angle of 11 degrees, the effective thickness of the Magnus V’s belt would be approximately 470 mm. This represented an extraordinary increase in protection compared to the preceding battleship class. This belt covered a length from the 2.7 meters ahead of the forward turret’s barbette to approximately 8 meters behind the rear turret’s barbette. The belt thinned to 343 mm over the engine and boiler rooms after the rear turret. Behind that, it thickened again to 380 mm to cover the magazines of the rear 152mm secondary guns. This resulted in an overall protected length of 141.1 meters. This belt extended from the deck down to 1.4 meters beneath the waterline, providing comprehensive protection against shell fire.

The ship’s armored deck was a uniform 200 mm thick that ran the entire length of the armored citadel. This armored deck was double the thickness of what was present on previous Trinovantan battleships to account for the threat of long-range plunging fire which had become evident after the 4th Peninsular War. This exceptionally thick deck armor would also mitigate the danger of a plunging shell falling behind the inclined belt due to its outward angle, as it covered the entire hull from the edge of each belt. Rear of the citadel, the armored deck tapers down to 150 mm to protect the steering gear. Though developed with long-range shell fire in mind, the extreme thickness of this armored deck would provide comprehensive protection against both SAP and AP bombs that were used later in the Fourth Ostlander-Trinovantan War.

This armor scheme was intended to provide protection against the Magnus V’s 460 mm main guns at an expected combat range of 10-15 km. However, during testing the APC shells used by these guns proved to be more potent than initially estimated and were theoretically capable of penetrating the Magnus V’s belt armor at ranges of up to 20 km. However, the 200 mm armored deck was capable of resisting plunging fire from ranges that were beyond practical targeting ranges. It was determined that increasing the belt armor of the Magnus V to make it resistant to its own main battery would put it above the displacement limits outlined by the initial requirements, and that the current level of protection was enough to far outstrip any other gun in service. For instance, against the 380mm Model 1915 L/42 naval rifles used by preceding Trinovantan capital ships, the Magnus V had a theoretical zone of immunity ranging from approximately 5 km out to beyond their maximum range.

The armored citadel was separated from other sections of the ship by a 355 mm bulkhead. An additional 150 mm bulkhead is present to protect the steering gear. Torpedo protection is provided by internal torpedo bulges. This is of a largely conventional design, consisting of an air void and an inner buoyancy space, though enlarged to provide a greater degree of protection. One divergence was the use of a water-filled buoyancy space instead of steel crush-tubes as per previous torpedo protection systems used by Trinovantum. This provided similar protection to the older crush-tube design but with a reduced weight impact. A 50 mm torpedo bulkhead protects the inner hull spaces. Combined, the torpedo defenses have a width of 4.9 meters inboard. Overall, this system was capable of withstanding hits from 340 kg torpedo warheads.

Turret protection is provided by 460 mm of sloped non-cemented armor on the face of the turrets, considered sufficient against any current or theoretical naval gun of the time. This reduces down to 355 mm thickness on the sides of the turret, with the top of the turrets being 200 mm thick and thus providing comparable protection to the armored deck. The armored barbettes are 380 mm thick, protecting the turret mechanisms and ammunition hoists. The conning tower was given a similar 380 mm of protection, with communications systems connecting the conn to the bridge being run through a 200 mm armored tube. The connected fire control director was given an armored hood that ranged from 150-100 mm in thickness. The secondary gun turrets were giving minimal protection, with 75mm on the face and sides of the turret and 22mm on the roof.

Propulsion

Drive power for the Magnus V is provided by 20 high pressure three drum water-tube boilers which are divided between four boiler rooms. These boilers feed two geared steam turbines sets separated between two turbine rooms, with each set driving its own propeller shaft. The boiler rooms were placed aft of the turbines, in order to keep the funnel as far back along the ship as possible to improve the angles of fire of the rearmost turret. Even with this turbine-first machine space arrangement, the engines were still placed far further aft than they would be on a conventional layout which reduced the required length of the propeller shaft. The total output of this system was a modest 56,000 shaft horsepower, which would be able to propel the ship up to 23 knots.

Sensors and Systems

The primary armament of the Magnus V was controlled by one of two director towers, both located on the forward tower. The primary tower was placed on the bridge superstructure, just above and behind the “B” turret. The secondary director tower was located above the conning tower, underneath an armored hood. Both towers could control the full main battery of the Magnus V, as opposed to preceding designs where the secondary tower, if present at all, would only be able to direct the aft guns. Each main gun turret was equipped with a 12.5 meter coincidence rangefinder. Additionally, the Magnus V would be equipped with the Model 1 Fire Control Table, a simple analog fire control computer which assisted in gunnery calculations. More refined versions of this early system would be retrofitted onto older Trinovantan capital ships and would later feature on the Halvard I class of fast battleships.

Two director towers were provided for the secondary battery, one on each side of the bridge superstructure. The original anti-aircraft battery would be directed from a high-angle director on the ship’s mizzenmast. The octuple 40 mm gun mounts each featured their own director system which could be fed data from the anti-aircraft director’s height finder. A pair of 4.6 meter torpedo rangefinders is mounted on the aft superstructure near the funnel, to provide ranging data for the underwater torpedo tubes.

A refit in 1942 would see the addition of a gunnery radar to the ship’s fire control systems, along with an update to a newer fire control table to make use of the radar’s capabilities. This system operates in the UHF wavelength band, with an output of 25 kW, and is capable of acquiring targets at a range of up to 18.5 km. This system was generally well regarded, with it being considered particularly valuable for gunnery at night or in inclement weather. Facilitating this was the addition of an air/sea early warning radar and a surface search radar. The air-warning radar operates in the low VHF range and is capable of spotting potential targets at ranges of up to 175 km, though the low frequency at which this early warning radar operated at meant that the signal returns were often inaccurate to the point of being impossible to identify even the basic characteristics of what was being tracked, with a particular problem being ships or aircraft in close formation showing as a singular return. The surface search radar used by the Magnus V had a maximum acquisition range of 46 km against large ships. Due to operating in the S-band, the returns generated by this radar set were accurate enough for identification, tracking, and even gunnery plotting. However, the higher frequency band that allowed this also increased its power draw over that of the early warning radar, having a maximum draw of 100 kW compared to the warning radar's 70 kW.

Service History

The TRM Magnus V was laid down on March 18th, 1921 in Orten & Sogard’s Farsund Shipyard. Though initially planned to be laid down in 1922 with a projected commissioning date of 1926, the ships were ordered early and the construction timeline advanced by one year due to rising tensions with Ostlichtor. Despite this, the sudden outbreak of the 3rd Ostlander-Trinovantan War later that year upended this advanced timeframe. As the fleet shifted to wartime readiness during the early stages of the war, personnel and materials would be transferred away from the Magnus V’s construction and towards the servicing of existing warships. As fleet actions intensified during the war, construction of the Magnus V was paused altogether.

Commissioned on February 8th, 1930, became the flagship of the South Fleet. Uneventful career characterized by exercises and good will visits to allies and the colonies. Was present during the announcement ceremony of Temuair’s dominionship status in 1931. Major refit in 1942, addition of radar for both search and rangefinding, new fire control table, and VT fuses for AA battery. Flagship duties for the South Fleet were transferred to the Karsten Askelaad shortly after it was commissioned in late 1947.

1948 Colonial Panic Shore bombardment - “Earthshaker”

Fourth Ostlander-Trinovantum War. Miss initial stages due to Colonial Panic Escort duties Sinking of the SKS Admiral von Alder

Decommissioning after the 4th War.