FGM-148 Javelin

The FGM-148 Javelin is an American-made man-portable anti-tank guided missile fielded to replace the Dragon antitank missile.

Overview
Javelin is a fire-and-forget missile with lock-on before launch and automatic self-guidance. The system takes a top-attack flight profile against armored vehicles (attacking the top armor which is generally thinner) but can also take a direct-attack mode for use against buildings or fortifications. This missile also has the ability to engage helicopters in the direct attack mode. The missile reaches a peak altitude of 150m in top attack mode and 50m in direct fire mode. The missile is equipped with an imaging infrared seeker. The tandem warhead is fitted with two shaped charges: a precursor warhead to detonate any explosive reactive armor and a primary warhead to penetrate base armor. The Javelin was used in the 2003 Invasion of Iraq, with devastating effects on the Iraqi version of T-72s and Type 69 tanks.

The missile is ejected from the launcher so that it reaches a safe distance from the operator before the main rocket motors ignite; a "soft launch arrangement". This makes it harder to identify the launcher and allows it to be fired from within buildings; however, back-blast from the launch tube still poses a hazard to nearby personnel. Thanks to this "fire and forget" system, the firing team may move on as soon as the missile has been launched.

The missile system is carried most often by a two man team consisting of a gunner and an ammo bearer, although it can be fired with just one person if necessary. While the gunner aims and fires the missile, the ammo bearer scans for prospective targets and watches for threats such as enemy vehicles and troops.

Development
In 1983, the United States Army introduced its AAWS-M (Advanced Anti-Tank Weapon System - Medium) requirement, and in 1985, the AAWS-M was approved for development. In August 1986, the Proof-of-Principle phase of the development began, with three competitors designing prototypes such as the SC440-AT . In late 1988, the POP phase ended, and in June 1989, the full-scale development contract was awarded to a joint venture of Texas Instruments and Martin Marietta (now Raytheon and Lockheed-Martin). The AAWS-M received the designation of FGM-148.

In April 1991, the first test-flight of the Javelin succeeded, and in March 1993, the first test-firing from the launcher succeeded. In 1994, low levels of production were authorized, and in 1996 the first Javelins were deployed with US Army units.
Test & Evaluation

Development Test and Evaluation (DT&E) is conducted to demonstrate that the engineering design and development process is complete. It is used to reduce risk, validate and qualify the design, and ensure that the product is ready for government acceptance. The DT&E results are evaluated to ensure that design risks have been minimized and the system will meet specifications. The results are also used to estimate the system’s military utility when it is introduced into service. DT&E serves a critical purpose in reducing the risks of development by testing selected high-risk components or subsystems. DT&E is the government developing agency tool used to confirm that the system performs as technically specified and that the system is ready for field testing.

DT&E is an iterative process of designing, building, testing, identifying deficiencies, fixing, retesting, and repeating. It is performed in the factory, laboratory, and on the proving ground by the contractors and the government. Contractor and government testing is combined into one integrated test program and conducted to determine if the performance requirements have been met and to provide data to the decision authority.

In 1996 the General Accounting Office (GAO) published a report questioning the adequacy of Javelin testing. The report, called “Army Acquisition – Javelin Is Not Ready for Multiyear Procurement”, opposed entering into full-rate production in 1997 and expressed the need for further operational testing due to the many redesigns undergone.

Previously in 1995 the Secretary of Defense, William Perry, had set forth five new operational test initiatives. These included: 1) getting operational testers involved early in development; 2) use of modeling and simulation; 3) integrating development and operational testing; 4) combining testing and training; and 5) applying concepts to demos and acquisitions.

The late-phase development of the Javelin retroactively benefited from the then new operational test initiatives set forth by the Secretary of Defense, as well as further test conducted as a consequence of the Army’s response to the GAO report. Before the Milestone III decision and before fielding to 3rd Battalion 75th Ranger Regiment at Fort Benning (also Army Rangers, Special Forces, airborne, air assault, and light infantry), the Javelin was subjected to limited parts of the five operational test and evaluation initiatives, as well as a portability operational test program (an additional test phase of the so-called Product Verification Test) which included live firings with the full-rate configuration weapon.

Per initiatives and as a DT&E function, the Institute for Defense Analyses (IDA) and the Defense Department’s Director of Operational Test and Evaluation (DOT&E) became involved in three development test activities, including: 1) reviewing initial operational test and evaluation plans; 2) monitoring initial operational test and evaluation; and 3) structuring follow-on test and evaluation activities. The results of these efforts detected problems (training included) and corrected significant problems which led to modified test plans, savings in test costs, and GAO satisfaction.

Qualification testing
The Javelin Environmental Test System (JETS) is a mobile test set for Javelin All-Up-Round (AUR) and the Command Launch Unit (CLU). It can be configured to functionally test the AUR or the CLU individually or both units in a mated tactical mode. This mobile unit may be repositioned at the various environmental testing facilities. The mobile system is used for all phases of Javelin qualification testing. There is also a non-mobile JETS used for stand-alone CLU testing. This system is equipped with an environmental chamber and is primarily used for Product Verification Testing (PRVT). Capabilities include: Javelin CLU testing; Javelin AUR testing; Javelin Mated Mode testing; Javelin testing in various environmental conditions; and CLU PRVT.

The All-up-Round Test Sets includes: Extreme temperature testing; Missile tracker testing (Track rate error, Tracking sensitivity); Seeker/focal plane array testing (Cool-down time, Dead/defective pixels, Seeker identification); Pneumatic leakage; Continuity measurements; Ready time; and Guidance sections (Guidance commands, Fin movement).

Components
Missile
Warhead
The Javelin missile’s tandem warhead is a high-explosive antitank round. This round utilizes an explosive shaped charge to create a jet of superplasticity deformed metal formed from trumpet-shaped metallic liners. The result is a high velocity jet that can penetrate armor.
The Javelin counters the advent of explosive reactive armor (ERA). ERA panels lay over a vehicle’s main armor and explode when impacted by a warhead. This explosion does not harm the vehicle’s main armor, but causes steel panels to fly into the path of the antitank round’s jet, so that the jet expends its most potent energy cutting through the panels, rather than through the main armor. The Javelin uses two shaped-charge warheads in tandem. The precursor charge sets off the ERA and clears it from the path of the main charge, which then penetrates the target’s primary armor.

A two-layered molybdenum liner is used for the precursor and a copper liner for the main charge.

To protect the main charge from the explosive blast, shock, and debris caused by the impact of the missile's nose and the detonation of the precursor charge, a blast shield is used between the main and precursor charge. This was the first composite material blast shield and the first that had a hole through the middle to provide a jet that is less spread out.

A newer main charge liner produces a higher velocity jet. This change makes the warhead more effective as a penetrator and smaller, with more room for propellant to increase the missile's range.

Electronic arming and fusing, called Electronic Safe Arming and Fire (ESAF), is used. The ESAF system enables the firing and arming process to proceed, while imposing a series of safety checks on the missile. ESAF cues the launch motor after the trigger is pulled. When the missile reaches a key acceleration point (indicating that it has cleared the launch tube), the ESAF initiates a second arming signal to fire the flight motor. After another check on missile conditions (target lock check), ESAF initiates final arming to enable the warheads for detonation upon target impact. When the missile strikes the target, ESAF enables the tandem warhead function (provide appropriate time between the detonation of the precursor charge and the detonation of the main charge).

Propulsion
The system uses a soft launch to eject the missile from the launch tube. A launch motor fires within the launch tube but stops burning before the missile clears the tube so that the gunner is not burned by hot gases. The soft launch permits low recoil for shoulder launch. When the missile has cleared the launch tube and has traveled a safe distance, the main rocket motor ignites and the wings and fins flip out (as shown in the top-right picture) as the missile is propelled at the target at subsonic speeds.

The missile has an integrated launch and flight rocket motor which keeps weight low. The launch motor initiator ignites the launch motor igniter, which then ignites the launch motor propellant grain. Gases vent through the launch motor nozzle. After a delay, a signal is sent to the flight motor initiator which ignites the flight motor igniter to ignite the flight motor propellant. When enough gas pressure builds up in the flight motor chamber a burst disk (that separates the launch motor and the flight motor) ruptures. The flight motor gases flow down the launch motor chamber and out the launch motor nozzle.

For gunner safety, a pressure release system is used to ensure that a malfunctioning launch motor does not cause an explosion. The launch motor has shear pins that fracture in the event of launch motor overpressure and allow the motor to be pushed out the back of the launch tube.
An annular igniter is used for the launch motor. A circular ring design was key to integrating the launch motor and the flight motor. The launch motor igniter had to be placed in the nozzle so it could not be blown out the nozzle since debris would be a hazard to the gunner. The annular igniter allows exhaust gases to be vented.

The rupture or burst disc that separates the launch motor and the flight motor has a higher tolerance for pressure on the launch motor side and lower tolerance on the flight motor side. This allows the disc to protect the flight motor from the ignition of the launch motor and when sufficient pressure develops still let the flight motor rupture the disc and send flight motor gases past it and down through the launch motor chamber.

The launch motor propellant is the same as that used in other missiles. The flight motor propellant is derived from the propellant used in the tube launched.

Seeker
As a fire-and-forget missile, after launch the missile has to be able to track and destroy its target without the gunner. This is done by coupling an onboard imaging IR system (different from CLU imaging system) with an onboard tracking system.

The gunner uses the CLU’s IR system to find and identify the target then switches to the missile’s independent IR system to set a track box around the target and establish a lock. The gunner places brackets around the image for locking.

The seeker stays focused on the target’s image continuing to recognize as the target moves or the missile’s flight path alters or as attack angles change. The seeker has three main components: 1) focal plane array (FPA); 2) cooling and calibration; and 3) stabilization.

1) Focal plane array (FPA) - The seeker assembly is encased in a dome which is transparent to the FPA long-wave infrared radiation. The IR radiation passes through the dome and then through lenses that focus the energy. The IR energy is reflected by mirrors on to the FPA. The seeker is a two-dimensional staring FPA of 64x64 MerCad (HgCdTe) detector elements The FPA processes the signals from the detectors and relays a signal to the missile’s tracker.

The staring array is a photo-capacitive device where the incident photons stimulate electrons and are stored in the detector as an accumulated charge. The electrons are discharged, pixel by pixel, as currents to a readout integrated circuits attached at the rear of the detector. A better photovoltaic mechanism in which a voltage signal is developed directly from the impact of the photons and charge storage is done in the readout rather than in the detector material.

2) Cooling/Calibration - The FPA must be cooled and calibrated. The CLU’s IR detectors are cooled using a Dewar flask and a closed-cycle Stirling engine. But in the missile there is not sufficient. So prior to launch, a cooler mounted on the outside of the launch tube activates the electrical systems in the missile and supplies cold gas from a Joule-Thompson expander to the missile detector assembly while the missile is still in the launch tube. When the missile is fired this external connection is broken and coolant gas is supplied internally by an onboard argon gas bottle. The gas is held in a small bottle at high pressure enough coolant for the duration of the flight approximately 19 seconds.

The seeker is calibrated using a chopper wheel. This device is a fan having 6 blades: 5 black blades with very low IR emissivity and one semi-reflective blade. These blades spin in front of the seeker optics in a synchronized fashion such that the FPA is continually provided with points of reference in addition to viewing the scene. These reference points allow the FPA to reduce noise introduced by response variations in the detector elements.

3) Stabilization - The platform on which the seeker is mounted must be stabilized with respect to the motion of the missile body and the seeker must be moved to stay aligned with the target. The stabilization system must cope with rapid acceleration, up/down and lateral movements. This is done by a gimbal system, accelerometers, spinning mass gyros (or MEMS), and motors to drive changes in position of the platform. The system is basically an autopilot. Information from the gyros is fed to the guidance electronics which drive a torque motor attached to the seeker platform to keep the seeker aligned with the target. The wires that connect the seeker with the rest of the missile have no friction to keep the seeker platform balanced.

Tracker
The tracker is key to guidance/control for an eventual hit. The signals from each of the 4,096 detector elements in the seeker are passed to the FPA readout integrated circuits which reads then creates a video frame that is sent to the tracker system for processing. By comparing the individual frames the tracker determines the need to correct so as to keep the missile on target. The tracker must be able to determine which portion of the image represents the target. The target is initially defined by the gunner who places a configurable frame around it. The tracker then uses algorithms to compare that region of the frame based on image, geometric, and movement data to the new image frames being sent from the seeker, similar to pattern recognition algorithms. At the end of each frame the reference is updated. The tracker is able to keep track of the target even though the seeker’s point of view can change radically in the course of flight.

To guide the missile the tracker locates the target in the current frame and compares this position with the aim point. If this position is off center the tracker computes a correction and passes it to the guidance system which makes the appropriate adjustments to the four moveable tail fins, as well as six fixed wings at mid-body. This is an autopilot. To guide the missile the system has sensors that check that the fins are positioned as requested. If not, the deviation is sent back to the controller for further adjustment. This is a closed-loop controller.

There are three stages in the flight managed by the tracker: 1) an initial phase just after launch; 2) a mid-flight phase that lasts for most of the flight; and 3) a terminal phase in which the tracker selects the sweet spot for the point of impact. With guidance algorithms, the autopilot uses data from the seeker and tracker to determine when to transition the missile from one phase of flight to another. Depending on whether the missile is in top attack or direct attack mode, the profile of the flight can change significantly. The top attack mode requires the missile to climb sharply after launch and cruise at high altitude then dive on the top of the target (curveball). In direct attack mode (fastball), the missile cruises at a lower altitude directly at target. The exact flight path which takes into account the range to the target is calculated by the guidance unit.

Launch Tube Assembly
Both men carry a disposable tube called the Launch Tube Assembly which houses the missile and protects the missile from harsh environments. The tube also has built in electronics and a locking hinge system that makes attachment and detachment of the missile to and from the Command Launch Unit a very quick and simple process.

Command Launch Unit
The gunner carries a reusable Command Launch Unit (in addition to the Launch Tube Assembly) more commonly referred to as a CLU (pronounced "clue"). The CLU is the targeting component of the two part system. The CLU has three views which are used to find, target, and fire the missile. The CLU may also be used separately from the missile as a portable thermal sight. Infantry are no longer required to stay in constant contact with armored personal carriers and tanks with thermal sights. This makes the troops more flexible and able to perceive threats they would not otherwise be able to detect. In 2006 a contract was awarded to Toyon Research Corporation to begin development of an upgrade to the CLU enabling the transmission of target image and GPS location data to other units.

Advantages and disadvantages

Advantages
The portable system is easy to separate into main components and easy to set up when needed. Compared to more cumbersome anti-tank weapon systems, the difference is noticeable. For example, a TOW requires a heavy tripod stand, a bulky protective case for the thermal sight, a larger, longer launch tube, and requires much more time to assemble and prepare. The Javelin (although very heavy) is lighter than other missiles and their necessary parts.
Although the CLU's thermal imaging may hinder aiming, its thermal targeting allows the Javelin to be a fire-and-forget system. This gives the firer an opportunity to be out of sight and possibly moving to a new angle to fire from, or out of the area by the time the enemy realizes they are under attack. This is much safer than using a wire-guided system because the firer must stay at the same location the missile was fired from and guide the missile into the target.
Another advantage is the Javelin's power at impact. The missile has a tandem shaped charge in its warhead that is made to penetrate reactive armor. The Javelin was created with the intent to be able to penetrate any tank armor and was tested on the M1 Abrams Tank. With the top attack mode it has an even greater ability to destroy the tank because it can attack where most tanks are the weakest.

The soft launch capability of the Javelin allows it to have only a minimal backblast area. This enables the Javelin to be fired from inside a wide variety of structures. This gives the Javelin advantages in urban fighting over the widely used AT4, which has a very large backblast area, although this is lessened in the AT4 CS. A large backblast area would seriously injure personnel if fired from inside a small structure.

The missile also has a greater range than the system it replaces, the M47 Dragon

Disadvantages
The main drawback of the system is its 49.5 lb (22.5 kg) total weight. This does not account for the additional batteries (BA5590 lithium battery) which weigh around 2.25 lb (1.02 kg) each. Each battery is estimated to last 4 hours by the Javelin's manufacturer. A normal load for batteries (not counting the "just in case" extras that most teams carry) is 5–10. This number may be more or less depending on the length of mission. The system is designed to be portable by infantry on foot and weighs more than the original specified weight the army called for.
Another drawback of the system is the reliance on a thermal view to acquire targets. The thermal views are not able to operate until the refrigeration component has cooled the system. The manufacturer estimates 30 seconds until this is complete, but depending on the ambient temperature, this process may take much longer. The thermal view is occasionally hindered by a naturally occurring phenomena where the temperature of the earth heats or cools rapidly, and may interfere with the recognition and lock-on of the intended target.