With the proliferation of missiles increasing worldwide, air defense is once again a hot topic. Most well-known air defense systems, such as the American Patriot and the Russian S-400, are long-range. The price of extensive coverage is that such systems are large and cumbersome, requiring launchers, command trucks, and bulky radars. As a result, they must be kept behind the front lines, far from potential ground threats. In a fast-paced offensive, these units can get left behind, as they simply maneuver too slowly.

Further, long-range air defense systems are not particularly effective against low-altitude airbreathing threats or short-range ballistic munitions (such as mortar rounds). For one, such targets often blend in with terrain clutter from far away. Also, since long-range air defense systems are not close to the action, their radar’s view of targets can be blocked by mountains, buildings, and other terrain features. Time-to-target is an issue as well — a Mach 4 missile such as the Patriot MSE will take over 20 seconds to reach a threat at the edge of its engagement range, which precludes the interception of many short-range munitions. Plus, using a $3.9 million Patriot missile against a drone or artillery round is not exactly economical.

To provide troops on the frontline with relatively cheap protection against low-flying threats and munitions, short-range air defense (SHORAD) is employed. SHORAD systems are light and portable, with guns and/or small missiles that cannot reach high-flying jets but are effective against low-altitude threats at short range. In this way, SHORAD systems and long-range systems compliment each other.

So that they can keep up with fast-moving tanks and armored vehicles, SHORAD systems are often wheeled or tracked and can be fired with minimal setup. Many are also armored to withstand the rigors of frontline combat. Many simple SHORAD systems are merely mounted applications of man-portable surface-to-air missiles (MANPADs). SHORAD systems are used on warships as the last line of defense, but this article will focus on land-based SHORAD.

For much of the Cold War, the Army had a wealth of SHORAD vehicles. Some were based on fast-firing rotary cannons; for example, the M163 Vulcan Air Defense System (VADS) featured a 20mm Vulcan gun. Others, such as the M6 Linebacker, used missiles (in this case the Stinger, which was designed as a MANPAD). As the Cold War ended and the US Army re-focused on counterterror, the need for such systems diminished and most were retired. The assumption was that American fighter aircraft, long-range missiles, and man-portable launchers would be enough to eliminate any threats. After all, the US Air Force had not faced a tough opponent since Vietnam, and many of its systems such as the F-15 were (and still are) undefeated in aerial combat.

However, this calculus has changed. During the late 1990s and early 2000s, when the bulk of SHORAD systems were retired or neglected, Russia was in a state of domestic crisis and its military was neglected. That is no longer the case; in fact, Russian air defense systems and fighter jets have improved remarkably over the years, to the extent that they pose a very real threat to American aircraft. Another development is the proliferation of small Unmanned Aerial Vehicles (UAVs), which have a small radar signature and fly very low. Small UAVs are also cheap, meaning they can be deployed in swarms, and using a million-dollar long-range missile on them would be impractical. While the Army already has a MANPAD, the Stinger, which performs short-range defense, this missile is small and its capabilities are limited. Thanks to such developments, SHORAD is once again in vogue. The Army’s ambitious goal calls for a SHORAD battery to embed with every Brigade Combat Team, ensuring that all major ground operations would have protection.

Currently, the Army’s SHORAD capability comes from two weapons: man-portable Stinger missiles and Stinger missiles mounted to HMMWVs (Humvees) as the AN-TWQ-1 Avenger. Because of the Stinger’s light weight and small size, its capabilities are limited, and the Humvee platform suffers from poor mobility and survivability. The Army is currently developing a new multi-mission launcher for use against drones and cruise missiles, but the launcher requires a large truck so it is not mobile enough to operate with the maneuver force.

To fill the SHORAD gap, the Army will eventually need a new system which can handle swarms of UAVs, eliminate high-performance aircraft, and keep up with other fighting vehicles. Boeing has proposed an upgrade to the Avenger system which would potentially fit the bill.

The new variant improves upon the original by integrating multiple missile types, instead of just the lackluster Stinger. A prototype featured AIM-9X Sidewinder and Hellfire Longbow missiles, but Javelin and Stinger missiles are also compatible. The integration of Hellfire and Javelin missiles indicates that the system is capable of engaging ground targets as well as aerial ones, creating a hybrid package. Atop the launcher is a small solid-state laser, which would be effective against small UAVs but not larger aircraft or armored targets, and in the center is a conventional 25mm autocannon.

The upgraded Avenger can be accepted by a number of platforms, including the Joint Light Tactical Vehicle (JLTV) and the Stryker armored fighting vehicle. It also has a static palletized variant. Perhaps the greatest appeal of this solution is that Boeing believes it could be fielded in less than a year.

Boeing’s proposal is not revolutionary. Rather, it uses proven missiles and guns in a novel configuration, with a small laser thrown in the mix. Some of the other SHORAD possibilities, however, push the boundaries of tech.

Until the 1950s, anti-aircraft artillery was the primary method of air defense. The dawn of the jet and missile age changed this, as targets became too fast to easily hit with gunfire. However, new innovations are turning the tables and signaling a possible return to gun-based air defense.

Driving this revolution is the development of hypervelocity projectiles (HVPs) — rounds which fly at many times the speed of a standard shell. HVPs were developed for use with railguns, which use a series of electromagnets to accelerate projectiles to Mach 7+. This reduces the time between firing and impact with the target, making HVP gunfire effective against jet and rocket-powered threats. Unlike a normal anti-aircraft shell, the HVP is guided by small fins, another feature crucial for hitting fast targets. Rather than using a bulky explosive warhead, HVPs destroy their targets by simply slamming into them at immense speed.

Railguns, while simple in theory, are difficult to perfect. Ironically, the railgun’s greatest asset is also its downfall: the HVP rounds travel through the barrel so quickly that they tend to erode and deform it. Also, generating enough power to fire the railgun is a challenge, especially on smaller platforms. Because of these issues, the railgun is still years away from fielding.

However, engineers realized during development that an HVP could also be fired from a conventional gun, albeit at a lower speed. This means that the Army’s M777 howitzer and M109 Paladin self-propelled gun could be converted to anti-aircraft weapons systems with relatively minor upgrades. Since the Army already has hundreds of these systems in service, this is undoubtedly an attractive proposition. Of course, the guns would need to be networked with some type of radar to obtain targeting information; small sets such as the AN/MPQ-64 Sentinel would be ideally suited. While not as mobile as other SHORAD solutions, an HVP-armed Paladin and a Sentinel could provide effective air defense for relatively cheap, as an HVP round costs around $50,000, while missiles such as the AIM-9X cost upwards of $400,000. Plus, a single Paladin can stow 37 complete rounds, while missile-based SHORAD systems usually carry less than 10 missiles. If the conventionally-fired HVP idea proves successful, a dedicated air defense gun with better mobility than the Paladin could be produced.

The holy grail of SHORAD is a mobile laser system, referred to as a directed-energy weapon in military circles. Small lasers like the one fitted to Boeing’s upgraded Avenger have been around for a while — the real challenge is creating a significantly more powerful laser which needs no help from guns or missiles to destroy its target. The benefits of such a weapon would be game-changing. Because energy weapons need no ammunition other than electricity, they can be fired repeatedly at a trivial cost. Plus, the energy discharged from such a weapon travels at the speed of light, so aiming is simple. However, significant challenges exist. For one, lasers require a relatively large amount of power in a very short period of time, while generators produce a relatively small amount of power over a long period of time. To bridge this gap, robust power storage banks are needed to build enough charge for firing. Creating a system which can store and discharge enough power to destroy targets reliably is extremely difficult. Further, the power of a directed energy weapon decays sharply over long distances, especially in foggy or hazy conditions.

Despite such obstacles, the US Army has made strides in laser-based air defense technology. Recently, the Army received a 60kW laser from Lockheed Martin, the most powerful truck-based military laser ever produced. It achieves this feat by combining a number of less-powerful fiber laser units into one coherent beam. A few years ago, the Army tested a 30kW laser, which was capable of burning holes in metal objects from several kilometers away. The 60kW laser, despite being twice as potent, is still much too weak for military usage beyond shooting down small UAVs and other soft targets. To reliably engage threats such as missiles, airplanes, and artillery shells, which have thick metal skins and move quickly, the power would need to be upped significantly — the Army’s goal is a 100kW laser. Another issue is that the HELMD demonstrator, which current experimental lasers use as a platform, is rather large and would not be capable of maneuvering with tanks and other combat vehicles. If the Army wants a laser capable of deploying on the frontline, it would need to miniaturize the components so the weapon could be mounted to a more nimble vehicle.

Since many of the breakthroughs associated with HVPs and directed energy weapons occur in clandestine military labs, public information is incomplete at best. As a result, nobody knows for sure how close directed energy weapons and HVPs are to fielding. Some would argue they may never see the light of day at all. However, the recent spate of successful tests and the need for a new short-range missile defense weapon certainly indicate that the military is willing to find solutions no matter the cost. Thus, the question of hypervelocity projectiles and lasers is less “if” and more “when.” Until then, conventional systems such as the Avenger will have to fill the gaps.