Today's battlefields call for smart munitions guidance and fuzing technology that aims to reduce collateral damage and increase effectiveness.
On today's battlefield, where targets can be hidden among civilians and precious infrastructure, guiding munitions to their target has become more important than ever. When a gun emplacement is located mere feet from a school, or a bunker is located next to a hospital, the ability to fire a weapon that will hit a target exactly is of the utmost importance. Gone are the times when battles were fought in the open and unguided weapons could be launched without fear of hitting noncombatants.
Smart munitions are guided using different systems and are fuzed in many ways based on what mission they will be serving. Whether a weapon is seeking a target that was painted by a laser to detonate at the point of impact, or being lead to a GPS coordinate to explode at a specific height above the ground, smart munitions are used in countless missions and in a variety of ways.
Smart munitions are some of the most powerful tools available on the battlefield today, especially since traditional munitions have fallen out of use. "Smart munitions is a very active field," says Roy Rumbaugh, program manager for the Advanced Precision Kill Weapon System (APKWS) at BAE Systems in Nashua, N.H. "The reason is that non-precise weapons are really for area suppression, for wars of the past. In today's theaters of engagement, collateral damage is an extremely important topic and taking out only your target is more and more important each day. Having precision allows you to use very small munitions and place them very accurately. A larger munition causes a lot of collateral damage. Precision weapons are the future, because non-precise weapons have a diminished role in today's warfare."
Not only do smart munitions reduce collateral damage and destroy the target, but they also increase the actual effectiveness of the weapon. "Operators placing a legacy warhead directly on target for the first time, with precision guidance, have been favorably surprised about how effective a small warhead can be," Rumbaugh says. "If you're not guiding precisely, you're not really being effective."
When the full power of a weapon comes to a target, the force is increased by huge amounts, which makes effective some payloads that once were considered too small. This results not only in cost saving, but also in saving soldiers and vehicles from carrying large and heavy loads into combat.
One of the simplest methods of guidance involves lasers, in which designators illuminate the target. Smart munitions detect the laser beam and ride it right into the target.
Infrared guided munitions, also known as heat-seeking weapons, use a sensor that detects the infrared radiation to guide itself to a target. Any object that gives off heat registers to an infrared sensor, making it a prime candidate for use in air-to-air missions or when targeting any other major source of heat. Infrared guidance systems are commonly used with optical systems or helmet-mounted sights, to aim the seeker at the target.
Radar-guided systems can feature either an on-board radar to detect and guide the weapon to the target, or a radar in a different location that designates a target and communicates via radio with the weapon to guide it to its target. Similar to infrared systems, radar requires an operator to identify a target and launch the weapon before it is uncaged and allowed to seek the target on its own.
Television-guided systems use a camera mounted on the weapon to guide it to the correct target. The weapon is operated by personnel who select the target on a display to guide it, either manually adjusting if the target moves or allowing a contrast-based system to adjust the weapon's aim automatically.
GPS guided systems function by having the weapon communication through radio with a GPS satellite for information rather than using on-board sensors to detect the target. The weapon is then guided using the most efficient path determined by its on-board processing and inertial guidance system.
|The Advanced Precision Kill Weapon System is a laser-guided munition that is compatible with existing Hydra 70 unguided rocket launchers and components. It converts the Hydra 70 unguided rocket into a precision-guided munition through the addition of a mid-body guidance unit developed by BAE Systems.|
Different systems for different missions
With so many different ways to guide a weapon to its target, the choice of one system over another has many considerations. Each method of guidance has its own advantages and drawbacks, with different systems functioning better in certain environments and situations. "It's about mission effectiveness," says BAE's Rumbaugh. "The guidance system has to serve whatever mission it is trying to do."
Of course, mission effectiveness isn't the only issue system designers worry about. An ideal guidance system is small, lightweight, and inexpensive. "The more sophisticated the seekers and modes, the higher the cost and the bigger the physical footprint," Rumbaugh says. "High-precision at low cost is the holy grail."
The method that is most commonly used is laser guidance, as it involves no communication system in the weapon, allowing for high accuracy at a low cost and physical footprint. "Laser guidance is suitable for missions where you have the opportunity to designate the target with the laser," says Rumbaugh. "It's a low-cost way to get very high precision."
Lasers are popular for guidance because their use is relatively simple. "Lasers allow you to be extremely simple, as long as you can point that laser on the target and the weapon can see it, you can do a guidance solution," Rumbaugh explains. "The complexity and cost goes down dramatically when lasers are used." Due to their simplicity and very high accuracy, lasers are used in most situations where they are a viable form of guidance, such as against immobile or slow-moving targets. Current laser guided munitions can have accuracy levels as high as a 100 percent hit rate within two meters of a target.
While laser guidance is an ideal solution when it is viable, lasers require the ability to hold a laser on the target for a long period of time, making it unusable in situations where dust, clouds, or movement make it impossible to keep the laser on-target. "Laser and infrared aren't as good in obscured environments where a radar or GPS seeker might be used," Rumbaugh says. "The environment dictates your choice of weapon."
Similar to how an infrared seeker is not viable against targets that don't give off much heat; each seeker has a different environment for which it is well suited.
Smart munitions can feature several methods of guidance, and can utilize the information given in several ways. "If you have multiple seekers, you can either use them in combination, gathering information from multiple different sources, or you can go through hand-offs from acquisition to terminal phases," says BAE's Rumbaugh. A weapon could initially be guided to a target using GPS to penetrate cloud cover, and then switch to image-based guidance as it comes into range of a target for greater accuracy. Using several systems allows operators to combine the strengths of each system while mitigating weaknesses.
|A Joint Direct Attack Munition (JDAM) is dropped in combat. JDAM turns 'dumb' munitions into precision-guided weapons.|
Guidance technology evolution
As with other technologies, the steady improvement of processors and other hardware has enabled guidance technology to become much more effective, but the main improvement is elsewhere. "Probably the biggest leaps in technology are in the sensors themselves," says BAE's Rumbaugh. "Technology has moved very rapidly toward lower-cost, higher-performance, and lower-size devices. All the sensing technologies, including inertial sensors, have dramatically improved over time."
With sensors becoming more accurate, the guidance systems themselves are acting on better data, enabling these weapons to be placed on-target with greater frequency and effectiveness. While the software to guide a missile or mortar has been around for dozens of years, accurate guidance requires accurate data.
One new advancement in sensors that has great promise for guided munitions are Shortwave Infrared imaging sensors, which can be placed on missiles for the terminal phase of their flight to detect the laser being used to mark the target.
"It's all about discrimination and positive ID of targets, especially in an urban theater of operations," says David Dawes, manager of business development for U.S. Department of Defense (DOD) applications at UTC Aerospace Systems in Princeton, N.J. "Having seekers that can discriminate and track targets with better precision is the direction we're going-and imaging sensors are the key enablers for that effort," Dawes says. "And the key enablers for those sensors mean being able to see targets in all kinds of environments and weather conditions, with all the contextual clues you really need for good identification rather than just detection."
|Joint Direct Attack Munitions (JDAM) are created by adding sensors and a guidance system to a 'dumb' munition.|
Trends in smart munitions
Smart munitions have been steadily trending toward smaller weapons. "It enables you to carry a lot more of them on a platform," explains BAE's Rumbaugh. "This enables immediate engagement of fleeting targets. In modern warfare, where you have multiple targets, you don't have time to go back to base and get a new load. A higher quantity of smaller munitions can be carried on each sortie which is more effective against targets that are not persistent."
Targets in today's warfare are not consistent, and carrying enough ammunition to eliminate all of them is important when confronted with guerilla tactics. Smaller munitions allow vehicles to stay on target rather than having to return to base while enemy combatants return to hiding.
With an increased focus on cost reduction, modern militaries have been turning more toward making legacy weapons more effective. "In today's funding environment starting a brand new weapon from scratch is a pretty onerous task; it requires a lot of money and time. Modifying an existing system is much cheaper than building a new one. The demand to add precision guidance to non-precise weapons is quite high. We're seeing a lot of retrofit interest for cost reasons."
Many programs have come into being with the intent of upgrading unguided munitions into guided munitions, such as the Joint Direct Attack Munition program. Upgrading an unguided weapon into a guided one involves attaching a sensor kit and an actual guidance kit, generally a tail kit with fins that steer the weapon as it travels through the air, to the weapon itself.
|An engineer at BAE Systems works on the Advanced Precision Kill Weapon System (APKWS). APKWS is a laser-guided munition that has been fielded in Afghanistan.|
Fuzing on smart munitions
Guiding a weapon to a target is important, but making sure the weapon detonates at the precise time to cause maximum damage is equally important. Simply hitting a tank with a missile is not enough; the missile needs to destroy it or render the tank inoperable. Proper fuzing is what ensures weapons will do the maximum amount of damage to targets while reducing collateral damage.
"Some of the different fuze types are fuze on contact, time delay, height of burst, and proximity," says BAE's Rumbaugh. "Different fuzes are for different missions. Point of contact fuzing is for if you want the munition to go off as soon as it strikes something, such as when you want low penetration into an object, a vehicle, boat, or gun emplacement. For hardened targets, such as lightly armored bunkers or vehicles, you want a time-delay fuze for maximum effect. If you're working in open fields against personnel, a height of burst fuze senses when you're a certain height above the ground and goes off or releases smaller munitions."
Each fuze type serves a unique purpose, and all smart munitions carry a fuze that tells the weapon when to detonate its explosive charge.
|A soldier 'paints' a target using a laser designator to guide the weapon. Laser-guided munitions are popular among armed forces due to their low cost and high accuracy.|
With smart weapon guidance having attained such high accuracy, there has been increased interest in fuzing and how to improve the effect of weapons once they have reached their target. "There have been a lot of discussions looking at other types of warheads and fuzes," says BAE's Rumbaugh, "we have a great delivery vehicle now, so the question is what do we put on the end of it to perform specific missions."
One of the capabilities that has been seen as very desirable is the ability to modify how a fuze behaves, allowing you to essentially change the type fuze of a weapon based on its mission. "If you have the ability to modify the kind of fusing you have on a mission, then you have more than a one-trick pony, which is where I see the interest going. A common delivery system and a variable munition on the front end opens up all kinds of possibilities to modify and change things in the field and have a low inventory."
Being able to switch a single mortar round from a height of burst fuze for use against personnel to a time-delay fuze for use against convoys and armored vehicles would reduce the load soldiers need to carry and save costs by requiring fewer mortar rounds to be manufactured as one round covers several missions.
The future of smart munitions
Smart munitions are in for advancement due to necessity, and the improvements to guidance systems, fuzing, and even energetic materials have been coming in at a rapid pace. Demand for precision munitions is high and will likely remain so for a long time.
"The rules of engagement are pushing our direction for precision, as is the broader use of precision. We want to reduce collateral damage; we need precision for force protection of both friendlies and non-combatants; we're looking at scalable lethality, from non-lethal to lethal responses," says Bill Smith, director for fuze and precision technologies at the U.S. Army's Munitions Engineering and Technology Center in Picatinny Arsenal, New Jersey. "All of that will push our targeting needs and the state-of-the-art in target locating devices; it also means smaller munitions and smaller precision components."