Weapons of Ukrainian Victory: Review of the Patriot air defense system

The United States is currently finalizing plans to send the first battery of the Patriot air defense system to Ukraine. Let’s take a closer look at this missile system.

The transfer of this system is both a confirmation of the unwavering US commitment to supporting Ukraine and a significant improvement in the capabilities and potential of the Ukrainian air defense system. At the same time, this step raises several questions, such as the need for intensive training of the Ukrainian military in the use of these systems, the prospects for long-term sustainment of the unit, and the short- and long-term implications for US air defense. In addition, the transfer of one battery of the Patriot air defense missile system will not radically change the situation, as its use is limited by the area it can cover and the high cost of interceptors. But it is a good signal for Ukraine, for its air defense, and a further impetus for cooperation with other Western partners.

The Patriot system is part of a $1.8 billion aid package to Ukraine that was announced during Ukrainian President Volodymyr Zelenskyy’s recent visit to Washington, D.C., to meet with President Biden and other officials.

Readers of a certain age may remember first hearing about Patriot missiles during the 1991 Gulf War, when the missile system effectively shot down Iraqi Scud missiles in defense of Israel.

The Patriot is one of the most sought-after air defense systems on the American arms market, and is currently in service with Saudi Arabia, the Emirates, and NATO allies in Europe. Israel still uses it. Now we can add Ukraine to this list.

So, first things first.

TABLE OF CONTENTS

1. What is interesting about the Patriot air defense missile system

2. The purpose of the Patriot air defense missile system

3. Stages of Patriot air defense system development

4. What is included in the Patriot missile system

5. Details on the operation of the Patriot

5.1. MIM-104A anti-aircraft guided missiles

5.2. Controlling the launch of the MIM-104A missile

5.3. Fire control station AN/MSQ-104

5.4. Multifunctional radar AN/MPQ-53

5.5. M901 launcher

6. Technical characteristics of the Patriot missile system

7. The cost of Patriot

What is interesting about the Patriot air defense missile system

The Patriot is a long-range mobile air and missile defense system capable of shooting down targets at any altitude, in any weather conditions, and designed to combat tactical ballistic missiles, cruise missiles, and aircraft. Mounted on trucks, each system is capable of holding four interceptor missiles that can be moved at will. The system is manufactured by Raytheon in Massachusetts and Lockheed Martin Missiles and Fire Control in Florida.

First deployed in the 1980s, Patriot has become the workhorse of the US Army’s air and missile defense, a key element of its power and a major symbol of US commitment to allies and partners. Unlike a single missile system, the Patriot includes a family of elements, control units, radars, a family of interceptors, and other support equipment. The Patriot is in service with the United States and allied countries, including Germany, Greece, Israel, Japan, Kuwait, the Netherlands, Saudi Arabia, South Korea, Poland, Sweden, Qatar, the United Arab Emirates, Romania, Spain, and Taiwan. Ukraine will soon join them.

The word Patriot is an abbreviation for Phased Array Tracking Radar for Intercept on Target. This name was given to the missile system in 1976, but it was previously known as SAM-D. This program dates back to the 1960s and was intended to replace or supplement the HAWK and Nike-Hercules air defense systems.

The US Armed Forces have used Patriot batteries in numerous conflicts over the past 30 years.

The purpose of the Patriot air defense missile system

The Patriot air defense missile system is used to cover large administrative and industrial centers, naval and air bases from all existing air attack assets in the face of powerful enemy electronic countermeasures. The complex is capable of simultaneously detecting and identifying more than 100 air targets, continuously tracking eight selected targets, preparing basic data for firing, launching and guiding up to three missiles at each target.

An anti-aircraft battery includes 4-8 launchers with four missiles each. The battery is the minimum tactical fire unit that can independently perform a combat mission. The battery is most often used as part of a division.

The Patriot missile system has high combat capabilities. The effectiveness of the system is achieved due to its construction on the basis of advanced circuitry solutions, the use of modern materials and advanced technologies in the systems and components of the missile system.

The main technical solutions that characterize SAM systems include:

A multifunctional radar with a phased array and an electron beam scanning system.
The combined guidance scheme (radio-command guidance in the middle section of the trajectory and “guidance through the missile” in the final section) allows to significantly reduce the size of the homing head and the cost of onboard equipment of a high-precision guided missile. All this is achieved by transferring the functions of the on-board computer to the ground equipment of the system and reducing the required target acquisition range.
Large range and high speed of missiles.

Stages of Patriot air defense system development

The development of the system began in 1963 to replace the previous generation of air defense systems. The first flight test of the missile took place in February 1970, and on January 11, 1974, the missile first performed guidance maneuvers based on commands received from ground-based radar.

Since 1983, these air defense systems have been in service with the U.S. Army and have been supplied to America’s NATO allies, as well as Israel, Saudi Arabia, and Japan. Patriot became widely known during the Gulf War. And not even because it proved to be a reliable air defense system. According to the manufacturer, sales after that war amounted to about $3 billion.

During the Gulf War, the Patriot air defense system was used to combat Iraqi Scud tactical missiles. Warnings about the missile launch and its flight path came from a reconnaissance satellite. This data had to be received at least 90 seconds before the warhead appeared on the radar screen. As a rule, the interception was carried out at altitudes of 5-10 km at a distance of 7-15 km from the battery position. Sometimes the warhead was not destroyed completely, but only changed its flight path. Also, the target could be hit by fragments of the destroyed warhead due to the proximity of the interception point. In real combat conditions, the effectiveness of the systems was almost the same as during the range tests: the probability of hitting the target ranged from 0.6 (according to the Pentagon) to 0.8-0.95.

The purpose of the Patriot modernization was to adapt the air defense system to protect small areas from ballistic missile attacks. The task of this version of the air defense battery was not only to ensure that a tactical ballistic missile was deflected from its target, but also to destroy it. For this purpose, the software was modified, which also made it possible to combine the work of three Hawk and Patriot SAMs under the control of a single fire control center. During the modernization, the warhead of the missile was improved and a new fuze was installed, increasing the weight of the missiles. These changes did not affect the effectiveness of the missile when firing at aerodynamic targets and subsequently became standard for all modernized missiles.

A variant of the PAC-2 was tested at the White Sands test site in November 1987, with a modified Patriot missile hitting another Patriot missile that simulated a Soviet SS-23 ballistic missile.

As part of the second stage of modernization of the RAS-2 in the early 1990s, the GEM (Guidance Enhanced Missile) program developed a missile with an improved guidance system that included an advanced radio detonator. This improved the Patriot’s ballistic missile interception capabilities.

At the same time, the new QRP (Quick Response Program) program provided for the modification of the AN/MPQ-53 radar software to improve its capabilities in intercepting ballistic missiles. According to Reitheon specialists, this allowed to increase the Patriot battery’s defense zone against such missiles by 4 times compared to the RAC-1 version.

Raytheon has proposed another modernization of the Patriot system, creating a new version of the missile, designated as RAS-2 Hit-to-Kill. The proposal for this upgrade was made in order to give the first versions of the system in service a direct hit capability similar to the RAS-3 missile, as well as to increase their strike capability.

The modernization included replacing the passive COS of the existing PAF-2 missiles with an active Ku-band one, replacing the high-explosive warhead and introducing a special propulsion system, as well as upgrading the missile’s software. The new components provide the missile with the ability to maneuver from targeting to collision with the target, as well as to destroy attacking ballistic and cruise missiles, aircraft and UAVs. The choice of RAS-2 for these purposes is due to its greater range and altitude compared to RAS-3.

Together with the RAF-3, the Hit-to-Kill missile can ensure the operation of Patriot systems until 2028. The US Army’s SLEP program will include the modernization of the RAF-2 and PAC-2GEM missile variants to the PAC-2GEM+ configuration. This option will include a high-explosive warhead, an advanced in-flight reprogrammable radio fuze, and a surface acoustic generator to increase the effectiveness of countering cruise missiles.

The PAC-3 is another modernization of the Patriot, which has improved ballistic missile defense capabilities. Almost all aspects of the system have been updated. The new MIM-104F missile was introduced. It is much smaller than the old Patriot missiles. Four missiles are transported in one container. Thus, one launcher has 16 missiles instead of 4. The missile has a range of about 40 km and a flight altitude of 20 km. The radar has received an increased detection and tracking range.

What is included in the Patriot missile system

The Patriot missile system includes:

multifunctional radar station with a phased array antenna AN/MPQ-53
fire control station AN/MSQ-104
M901 launchers
anti-aircraft guided missiles MIM104
AN/MSQ-26 power supplies
means of communication, technological equipment
means of radio engineering and engineering camouflage.

Details on the operation of the Patriot

MIM-104A anti-aircraft guided missiles

The MIM-104A missile used in the Patriot is a single-stage guided missile with a conventional aerodynamic design. The missile consists of the following compartments (from the nose to the tail): fairing, homing head, warhead, engine, control system (control unit, 4 transverse stabilizers and 4 rudders with hydraulic drives).

The airfoil protects the homing head from high aerodynamic loads and heat fluxes at hypersonic flow rates. The fairing itself is made of a ceramic alloy by special casting. Its nose part is covered with cobalt alloy. The fairing body thickness is over 120 mm.

Under the airfoil is a flat radar antenna of the homing head (305 mm in diameter), mounted in a gimbal on an inertial platform. Behind it is the MDAGS guidance system, which consists of two units – the TSG end section guidance unit and the modular mid section guidance unit (MMP).

The MMP guidance unit is located in the warhead compartment and contains navigation devices and an on-board computer. The warhead compartment also contains an inertial sensor, auxiliary electronic equipment, including a signal converter, a detonator trigger mechanism, and a high-explosive fragmentation munition with a fuse and antennas. The missile is powered by a Thiocol TX-486 solid-fuel single-mode engine. Two cables run along the outside of the engine, which transmit signals from the guidance system to the control system located in the tail of the missile. The average thrust of the engine is 11,000 kgf, the operating time is 11.5 seconds. The engine housing is part of the rocket body, but has additional thermal protection. The engine contains a charge of conventional solid fuel fixed to the walls. The fuel is ignited by a pyrotechnic system located in the front of the engine casing. Four hydraulically driven steering wheels are located around the engine nozzle. This section contains the battery, oil tank, compressed air cylinder, electric pump and high-pressure unit. The rocket has no wings; the aerodynamic lift is generated directly by the fuselage.

During maneuvering, the overload can be more than 25 units. The missile systems are monitored using built-in instruments. A malfunction message is automatically transmitted to the fire control system computers.

The Patriot missiles are delivered in their original packaging, in rectangular containers. The guided missiles are placed in the containers on two railroad tracks. The containers themselves are made of aluminum sheets mounted in a welded frame. The front of the container is covered with a fiberglass-reinforced rubber cover that is punctured by the missile during launch, and the back with a hard fiberglass cover that is completely removed by the gases escaping during the salvo.

Controlling the launch of the MIM-104A missile

The flight is controlled by a combined guidance system. At the initial stage of the flight, software control is implemented, at the middle stage – radio command control, and at the final stage – using the TVM (Track-via-missile) method, which combines command guidance with semi-active guidance. The use of this guidance method made it possible to significantly reduce the system’s sensitivity to various electronic countermeasures, and also made it possible to organize the missile’s flight along the optimal trajectory and hit targets with high efficiency.

The essence of the TVM method is as follows. In the process of guiding the missile to the target, the AN/MPQ-53 radar simultaneously tracks the target and the MIM-104A guided missile. The radar signals reflected from the target are received by the MDAGS antenna and the angular coordinates of the target line of sight determined by it are transmitted via a high-frequency channel to a special radar antenna and sent to the onboard computer of the fire control center. The computer also receives signals received by the radar directly from the target, which are compared with the signals coming from the guided missile.

Based on the analysis and comparison of these signals, guidance commands are generated for the missile and transmitted to it by the radar’s main beam. After conversion on board the guided missile, these commands are transmitted to the control actuator as well as to the MDAGS antenna actuators to ensure continuous tracking of the target.

Fire control station AN/MSQ-104

The fire control center – the Patriot command post – is located in a special container mounted on the chassis of the M814 vehicle. Inside, communication equipment and a workstation for one operator are located along one wall, and a computer, data terminal, workstation for the second operator and auxiliary equipment are located along the other.

The combat crew of the command post consists of two operators. Each operator’s workstation has an air situation indicator with a diameter of 53 cm, an indicator control device, a set of key switches for inputting and outputting the necessary fire control information during combat operations, and a unit for monitoring the functioning of the system’s equipment.

The left indicator of the workstation displays the general situation in the detection, control and firing zones of the guided missile battery, and the right indicator shows information on the control of all elements of the missile system battery and the current air situation. The use of special service equipment allows for diagnostic monitoring of individual devices and the guided missile as a whole, even during combat.

Multifunctional radar AN/MPQ-53

The AN/MPQ-53 multifunctional radar is mounted on a 15-ton biaxial fifth-wheel semitrailer and is transported by an M818 wheeled tractor. The operation of the radar is largely automated – its maintenance is carried out from the control center of the combat crew, consisting of two operators. The station provides almost simultaneous detection, recognition, tracking of 90 to 125 air objects and flight control of all MIM-104A guided missiles aimed at targets in a given sector. The integrated AN/TPX-46(V)7 queryer is used to identify targets.

The maximum target detection range is 35-50 km (at a target flight height of 50-100 m) and up to 170 km (at a flight height of 1000-10000 m). It all depends on the angle of the radar antenna and the target azimuth. This is achieved by using a phased array antenna and a high-speed computer that controls the station’s operating modes at all stages.

The control system allows the Patriot battery to be used in conjunction with the E-3 Sentry long-range detection and control aircraft. In this case, the Patriot is in radar silence until the last moment, receiving targeting information from the airborne AWACS system of the aircraft.

The antenna system is folded up on the roof of the cab when in the field position. The radar sector is selected by turning the cab in the desired direction. In a fixed cockpit position, the radar is capable of searching and detecting targets in the 90° azimuth sector, and tracking and guiding missiles in the 110° sector.

A characteristic feature of the radar is the conversion of signals into digital form, which made it possible to use a computer to control the station’s operating modes. Electronic scanning of the antenna array radiation pattern is achieved by changing the phases of high-frequency radiated signals using phase shifters.

The radar transmitter generates and amplifies high-frequency oscillations that differ depending on the station’s operating mode in terms of modulation, pulse duration and repetition rate, power, and operating frequency. The power of the generated signals is tens of kilowatts, and in a pulse lasting several tens of milliseconds, it can exceed hundreds of kilowatts. To increase the resolution of the radar, the signal receiving and processing device implements the method of pulse compression in dispersive delay lines. The transmitter operating modes are changed by a computer in millionths of a second.

The radar uses the principle of compaction in sensing, receiving and processing signals in time. The entire area to be surveyed is divided into 32 separate sections, each of which is scanned one by one with a laser beam, with the station’s operating cycle time in each section being 100 µs, and the radar’s operating mode can be changed from cycle to cycle.

Target search in a given sector takes the most time, and tracking targets and guided missiles takes less time. The duration of the full cycle of searching and tracking targets, as well as guiding missiles to them, is only 3.2 seconds. The radar also has a mode of operation in which the air situation is not monitored in the entire zone consisting of 32 areas, but only in those areas where air targets are most likely to appear.

M901 launcher

The M901 launcher is designed to launch, transport and temporarily store missiles. It is mounted on an M860 two-axle semitrailer and transported by a wheeled tractor. The launcher includes a lifting boom, mechanisms for lifting missiles and guiding them in azimuth, a power supply, a drive for installing a radio mast, which serves to receive commands and transmit data to the fire control station, an electronic unit and communication equipment.

As soon as the launch command is received, the necessary data is entered into the missile’s storage device. When the “start” button is pressed on the operator’s console, power is supplied to the control system equipment, after which the ground computer of the fire control station automatically turns on the missile control system, performs the necessary calculations and prepares the flight algorithm.

The reaction time of the Patriot air defense battery is minimized primarily by pre-turning the control panel arrow in the direction of the intended attack, as well as by minimizing the time lost when the missile enters the flight path. Each accelerator installed on the ground is assigned a specific sector of space, and these sectors overlap many times. This allows the Patriot battery to fire in a circular pattern, unlike air defense systems that use vertical-launched missiles.

It should be noted that the development of the MIM-104 guided missile considered a vertical launch option. However, this option was abandoned because at that time such equipment was not used on American missiles of this size.

Technical characteristics of the Patriot missile system

Maximum range of target interception: 80 km (in the 90° sector)
Minimum target interception range: 3 km
Maximum target interception height: 24 km
Minimum target interception height: 0.06 km
Number of simultaneously fired targets: 8 (in the 90° sector)
Probability of target hit: 0.8 (in combat conditions 0.4-0.6)
Missile weight: 912 kg
Weight of the rocket with the container: 1696 kg
Diameter: 0,41 м
Length: 5.31 m
Speed: 3-5 Mach
Maximum transverse loads: 30g
Control: by means of cross-shaped stabilizing tail planes
Span of stabilizers: 0,87 м
Engine: RDTT TX-486 from Thiocol
Specific engine thrust: 13 kN-s/kg
Engine start-up time: 12 с
Guidance system: in the middle section – radio command, in the end section – radar TVM
Warhead: high-explosive fragmentation warhead
Warhead warhead: conventional explosive
Fuze: XM818, non-contact
Container dimensions: 0,99×1,09×6,10 м
Weight of the warhead: 70 kg (RAS-1), 90 kg (RAS-2)
Deployment time: 30 minutes.

The cost of Patriot

Over the years, the Patriot system and missiles have been constantly modified. The current interceptor missile for the Patriot system costs about $4 million, and the launchers cost about $10 million each.

At this price point, it is unprofitable to use Patriot to shoot down the much smaller and much cheaper drones that Russia uses in Ukraine.

For example, Ukraine faces a variety of attacks from Russia, and the Patriot may be good against some and not very useful against others. The Patriot battery has a long range, but can only cover a limited area. For example, Patriot systems can effectively defend a military base or critical infrastructure facility, but cannot fully protect a large city like Kyiv. They could only provide coverage for a part of the city.

However, the Patriot’s ability to counter ballistic missiles and aircraft could protect Kyiv in the event of a potential Russian attack with tactical nuclear weapons.

But beyond the capabilities of the Patriot, its deployment sends an unequivocal signal of the US government’s continued support for the Ukrainian people’s fight against the Russian invasion. And sometimes it is even more important.

Now, in the face of fierce fighting with the occupiers, every high-precision projectile, every combat vehicle, every air defense system is extremely necessary for us, so I would like to sincerely thank our Western friends and partners for their help and support. The invaders will not escape from retribution. Glory to Ukraine! Death to the enemies! Glory to the Armed Forces of Ukraine!

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