While the museum of the Royal Netherlands Navy in Den Helder (the Marinemuseum) lacks the space for a 4,300-ton guided missile frigate, a bridge module and a forward gun were saved from the scrapped Tromp-class frigates and now sit in the museum's outdoor memorial plaza. The two ships of the Tromp-class were arguably the most distinctive vessels in the Royal Netherlands Navy in the 20th century, with bridges topped by an enormous radar dome. This dome housed the cutting-edge, Dutch-developed three-dimensional (3D) radar that made the Tromp-class frigates powerful air defence and command and control ships.
The development of 3D radar was spurred by the rising threat of maritime attack by the Soviet Union in the 1960s. With the Soviets having assembled a large fleet of naval vessels and aircraft armed with anti-ship missiles, scenarios in which a Dutch naval ship would have to simultaneously track dozens of aircraft, ships, and incoming missiles became increasingly probable. At that time, however, existing radar systems could only track a few targets at a time and would soon become overwhelmed. Additionally, search radars only covered a two-dimensional slice of the spectrum, searching either in a horizontal or vertical plane. The Royal Netherlands Navy and the government's defence electronic development laboratory determined that a new radar system was required, combining long-distance detection with simultaneous height calculation and target direction. The new system would also need to track at least 100 targets in three dimensions (horizontal, vertical, distance) simultaneously.
In 1969, the Dutch company Hollandse Signaal Apparaten completed two Multi Target Tracking Radar (MTTR) prototypes. The revolving antenna system consisted of two search antennae and two target tracking antennae. The search antennae moved on a vertical plane, which combined with a revolving motion created a complete three-dimensional search pattern. The stabilised platform, housed within a large radar dome, turned at 20 revolutions a minute and had a range of 390 kilometres. It was able to track over 100 targets as small as a square metre. These prototype 3D radars were fitted to the guided missile frigates HNLMS Tromp and De Ruyter, which commissioned into the Royal Netherlands Navy in 1975 and 1976, respectively. At the time, these ships had the most powerful radar systems in existence. The 3D radars produced an enormous volume of data per second, which was processed by the Data Action Information System (DAISY). Information from DAISY was used by the ships' weapons systems, such as Harpoon missiles and the Goalkeeper close-in weapon system, to fire independently at targets. Other weapons on the ships, such as SeaSparrow missiles and the Bofors 120mm guns, used the WM 25 radar and information from DAISY to hit aircraft and anti-ship missiles at high altitude. The TARTAR fire control radar was used to guide medium-range Standard Missiles to their targets.
Equipped with their powerful 3D radar antennae, Tromp and De Ruyter generally sailed as the flagship of a squadron of naval vessels. In addition to providing data to the ships' own weapons systems, the 3D radar also provided real-time tactical information via radio (and later satellite) to all of the ships and aircraft of the squadron. HNLMS Tromp was decommissioned in November 1999 and HNLMS De Ruyter followed in October 2001. Recognising the technological importance of the 3D radar as a proud Dutch innovation, De Ruyter's bridge and radar dome were listed for preservation and removed before the ship was scrapped.
In 2009, the Friends of the Marinemuseum Foundation launched an initiative to transform De Ruyter's bridge and radar dome into an attraction for the general public. The result was an immersive experience that introduces visitors to the 3D radar and the guided missile frigate and her crew as a whole. Inside the radar dome, visitors experience a simulation of the wind force created by the radar as it spun at 20 revolutions per minute. On the bridge, visitors observe an immersive naval warfare scenario played on screens in place of the bridge windows.
Specifications: HNLMS De Ruyter (F806)
Displacement: 4,308 tons (full load)
Length: 133.2 metres (437 feet)
Beam: 14.8 metres (48 feet 7 inches)
Draught: 6.6 metres (21 feet 8 inches)
Propulsion: 1 x Rolls-Royce Olympus gas turbine and 1 x Rolls-Royce Tyne gas turbine generating 51,000 horsepower and powering twin propellers
Speed: 28 knots (52 km/h; 32 mph) maximum; 18 knots (33 km/h; 21 mph) cruising
Range: 5,000 nautical miles (9.300 kilometres) at 18 knots (33 km/h; 21 mph)
Armament: 1 x Standard surface-to-air missile launcher with 40 missiles; 1 x octuple SeaSparrow surface-to-air missile launcher with 16 missiles; 8 x Harpoon anti-ship missiles; 2 x twin Bofors 120mm (4.7-inch) guns; 3 x anti-submarine torpedo tubes; 1 x Goalkeeper close-in weapon system Aircraft: 1 x Westland Lynx helicopter (carried in a hangar)
Complement: 306 officers and ratings, not including additional staff when serving as squadron flagship
Photos taken 30 April 2026
 |
| The monument entitled 'Shadows of Light' stands in the Marinemuseum's memorial plaza alongside the bridge of HNLMS De Ruyter and a 120mm (4.7-inch) twin gun turret. Shadows of Light is dedicated to those Royal Netherlands Navy personnel killed in the line duty, with an annual commemorative service held on the last Thursday in May. The silhouettes in the sculpture represent the emptiness remaining after the death of a family member or colleague. The slightly curved wall represents the broken circle of life, with the depiction of a turbulent sea and a small boat carrying mourning relatives aboard representing the emotional turmoil after the loss of a loved one. The monument's wall resembles a gate with four pillar, an old symbol for the transition from life to death. The three silhouettes represent Heaven (the Holy Trinity) and the four pillars symbolise Earth, Life and Death, Heaven, and Earth. |
 |
| The Marinemuseum's memorial plaza includes lines of raised grey stone representing the outline of HNLMS De Ruyter's hull, creating a 'virtual deck' and providing a sense of the size of the Tromp-class guided missile frigates. The bridge section and deck gun are placed in the same locations relative to each other as they were aboard De Ruyter and sistership Tromp. |
 |
| The Bofors twin 120mm (4.7-inch) gun from HNLMS Tromp (1975-1999), sistership of HNLMS De Ruyter. |
 |
| Prior to being installed aboard Tromp, this 120mm (4.7-inch) gun had been fitted to the Holland-class destroyer HNLMS Gelderland (D811), in service between 1955 and 1973. |
 |
| Tromp's gun and De Ruyter's bridge sit in the memorial plaza, in front of the former dockyard's Ordnance Shop, now one of the buildings housing exhibits on the Royal Netherlands Navy. After their decommissioning, Tromp's gun and De Ruyter's bridge and radar dome were designated for preservation as industrial heritage artefacts. |
 |
| The bridge of the former HNLMS De Ruyter, one of two Tromp-class guided missile frigates of the Royal Netherlands Navy. De Ruyter was in service from 1976 to 2001 and alternated with sistership Tromp as the navy's flagship. Each of these frigates formed the core of a squadron, being principally tasked with air defence, anti-submarine warfare, and command responsibilities, while also undertaking humanitarian missions and showing the flag overseas. The Tromp-class vessels were distinctive due to their metres-high radar dome atop the bridge. The dome housed the revolutionary, Dutch-designed three-dimensional radar that could measure an object's direction, distance, and height at the same time. This enabled the crew in the command centre to respond to enemy movements within a fraction of a second. |
 |
| A ground floor lobby contains displays on HNLMS De Ruyter, including this large model. De Ruyter had a complement of 306, not including squadron staff. By comparison, her predecessor, the cruiser HNLMS De Ruyter (1953-1972), carried over three times as many crew and her successor, the air defence and command frigate HNLMS De Ruyter (2004-present), requires a crew of only around 200. Between 1976 and 2001, approximately 7,400 Royal Netherlands Navy sailors served on De Ruyter, representing a whole generation of navy personnel. By the time the ship moored in Den Helder for the final time, she had sailed around 620,000 nautical miles (1,148,240 kilometres), the equivalent to almost 30 times around the world. |
 |
| A shot of HNLMS De Ruyter cresting a wave, from a video playing in the lobby exhibit area. the Tromp-class guided missile frigates were equipped with medium- and short-range missile systems to perform their air defence role, while guided torpedoes and a Lynx helicopter were used for anti-submarine warfare. Enemy ships could be engaged with anti-ship missiles with a range of more than 100 kilometres. The two twin Bofors 120mm guns were for use against land, sea, and air targets. In the late 1980s, a Goalkeeper 30mm close-in weapon system was installed on the roof of De Ruyter's helicopter hanger to defend against incoming anti-ship missiles. |
 |
| A ladder leads up from the lobby to De Ruyter's bridge. |
 |
| De Ruyter's bridge. The windows have been replaced by display screens showing an animated simulation of operations at sea. The console in the foreground, here on the starboard side of the bridge, was the navigating officer's position. |
 |
| The bridge is functionally laid out, with the five central seats in front of the windows reserved for (from left to right) the squadron commander, the ship's captain, the helmsman, the officer of the watch, and the pilot or reserve officer of the watch. All of the bridge personnel have their equipment within easy reach. The captain has visibility of over the weapons and detection systems, as well as two telephones and the public address system. In a crisis, the captain would move to the ship's command centre below the bridge. |
 |
| The helmsman's position, with a small steering wheel to make rudder adjustments. The manoeuvring panel sits between the helmsman and the officer of the watch to enable the latter to take over if necessary. In most situations, the helmsman would serve as a lookout while De Ruyter sailed on automatic pilot. |
 |
| The port side of the bridge. The console in the foreground was the signalman's post and it was from here that he maintained radio contact with other ships. The navigation cabin (with the arched doors) is positioned at the centre-rear of the bridge. |
 |
| One of the two radar consoles inside the navigation cabin at the rear of the bridge. The navigation cabin was kept dimly lit to assist those monitoring the radar screens. |
 |
| The map table inside the navigation cabin, used for plotting the ship's course. |
 |
| The port aft section of the bridge, showing the signalman's position and the door leading onto the port bridge wing (not accessible to visitors). The tour route continues to the radar cabins aft of the bridge. |
 |
| After leaving the bridge, visitors proceed into the radar cabins controlling the ship's 3D radar antennae. |
 |
| Here in radar cabin 4, four radar engineers calibrated and maintained the 3D radar, located two storeys above in the radar dome. Radar calibration was done by hand, by operating dozens of buttons and switches in the system cabinets around this room. Each cabinet played a different role in processing the radar data.
|
 |
| Receivers located here converted the radar signals to make them visible on screens, while other systems enabled identified targets to be tracked automatically and calculated. |
 |
| Radar signals were sent from radar cabin 4 to the command centre, a few decks below, under the bridge. The crew in the command centre used the data to respond to enemy aircraft and other possible threats. |
 |
| In an emergency or during a nuclear, biological, chemical damage control exercise, the lighting in the radar cabins would be switched to red and the crew would don anti-flash gear, special heat-resistant clothing like that worn by the mannequins now on display. |
 |
| Climbing up one deck takes visitors to radar cabin 3, located directly under the 3D radar antenna. Displays in this compartment explain the science and history of radar. It was in the 19th century that German scientist Heinrich Rudolf Hertz discovered that radio waves bounce off metal objects. By the outbreak of the Second World War, researchers in various countries had developed applications to detect aircraft and ships. Dutch scientists had managed to send and receive radio signals using a single antenna and many of these scientists fled to Britain following the Nazi invasion of the Netherlands, where they worked with British colleagues to develop small radar arrays for use aboard ships. Since the war, radar technology has continued to evolve: while the first radar sets could detect another ship 10 kilometres away, today some systems can detect targets in space. The Netherlands has built a reputation in the field of radar technology, with the firm of Thales Hengelo (formerly Hollandse Signaal Apparaten) a world leader. Search radar covers a circular area around a ship and can detect targets up to hundreds of kilometres away, depending on the power of the radio wave and the height of the target. Once a target is selected by the search radar, the fire control radar focuses a large amount of energy on the target, with the reflected beams providing precise data on the distance, height, and speed of the target. Calculation systems can analyse this data in seconds, with the information being fed to guns and missile launchers to fire upon the target. Modern missiles carry a miniature radar system to permit them to locate and home in on their targets independently. |
 |
| Thick bundles of cabling running between the radar installation above and the equipment here in radar cabin 3 relayed the radar data. Radar cabin 3 also contained the transmitter that sent search instructions from the command centre to the radar array, as well as the antenna switchboard. A large cabinet in radar cabin 3 houses the Satcom system, a precursor of today's satellite telephones, which was used exclusively by the captain during emergencies or when radio communication was impossible. As radar transmissions can be detected and jammed or attacked, today radar is being superseded or supplemented by newer detection systems: passive infrared sensors that measure movement without transmitting a signal, and the use of data from third parties that allow a target to be attacked without needing to transmit signals from the attacking ship. |
 |
| The ladder leading up from radar cabin 3 to the radar dome immediately above. |
 |
| A dramatically-illuminated portion of the 3D radar antenna inside the dome atop the bridge. The radar's revolving antenna consists of a dish-shaped search antenna and two spiral antennae for tracking targets. The search antennae moves vertically, combining with the revolving movement of the whole to provide a three-dimensional search pattern. The stabilised platform spins at 20 revolutions per minute, creating a force 7 (50-61 km/h) wind inside the radar dome. The entire installation weighs 3,500 kilograms (7,716 pounds). The 3D radar had a range of 390 kilometres and was capable of simultaneously tracking over 100 targets as small as a square metre in diameter. This made the radar aboard the Tromp-class frigates the most powerful system of its day (1975-2000). Indeed, during naval exercises, some participants asked the Dutch ships to turn off their 3D radars since the opposition forces did not stand a chance otherwise. |
 |
| A final look at the bridge of the former HNLMS De Ruyter. The Tromp-class frigates were nicknamed 'Kojak' due to their distinctive radar domes, which were similar in appearance to the bald head of actor Telly Savalas, star of the 1970s American television detective series Kojak. |
