The U.S. military has long been worried about the growing overseas hybrid threat. Hybrid threats are those that combine elements of modern warfare such as precision-guided weapons, unmanned aerial systems, rockets and short-range ballistic missiles and digital communications systems with more traditional aspects of low-intensity operations and organization. Terrorist groups such as Hezbollah and Hamas have been among the most effective practitioners of the art of hybrid warfare. In 2006, Hezbollah not only conducted massed rocket and missile strikes on northern Israel, but employed a sophisticated network of ground defenses employing advanced anti-tank weapons hidden among the Shia villages of southern Lebanon to neutralize Israeli ground forces. An anti-ship cruise missile struck an Israeli gunboat. In 2014, Hamas initiated a seven-week conflict with Israel that included hundreds of rockets fired from built-up areas, sophisticated tunnels running under the border and anti-tank guided missiles. Both Hezbollah and Hamas now employ light unmanned aerial vehicles (UASs) for tactical reconnaissance. ISIS has shown remarkable skill integrating weapons systems such as artillery, mortars and armored fighting vehicles captured from Iraqi forces with a wide array of low-intensity weapons and techniques, most notably improvised explosive devices (IEDs).
The hybrid threat soon could be coming to the U.S. homeland. We have already seen individuals trained, and on occasion equipped, by Al Qaeda trying to take down airplanes or conduct mass casualty attacks in places like Times Square. ISIS has been recruiting so-called lone wolf terrorists apparently with the expectation that they would use a firearm in their attacks or, at worst, a vehicle-borne IED.
What if the next lone wolf has access to a small UAS or a gyrocopter? In January a small quad rotor crashed on the White House lawn and a gyrocopter landed on the lawn of the U.S. Capitol last April. Small quad-rotor UASs are readily available online. Larger UASs with payloads of at least several pounds are becoming commonplace in business such as film making and real estate. Soon even bigger UASs, with payloads of 100 pounds or more will be available for everything from crop dusting to package delivery.
Using command guidance with a small camera or GPS system on a UAS, or a pilot at the controls of the gyrocopter, the terrorists would have an aerial IED but one with the potential accuracy of a precision-guided weapon. A small UAS probably would not damage a building but could be used as an assassin’s weapon.
The Department of Homeland Security and U.S. Northern Command have devoted a lot of attention to the potential threat posed by light private planes and business jets packed with explosives and flown into a building. There are reports that the Secret Service has deployed man-portable anti-aircraft missiles to protect the White House.
Gyrocopters are considered by the FAA to be aircraft and must abide by all rules that apply to standard fixed and rotary wing platforms. This includes obeying the aircraft exclusion zone around Washington, DC. The FAA restricts the private operation of UASs by weight, altitude and line-of-sight command guidance. The agency is developing rules to govern the use of larger UASs. It is likely that within a few years there will be thousands of UASs of various sizes flying around the country.
Unlike aircraft that can be tracked by radar, most UASs and gyrocopters are so small and fly so low that they cannot be detected by conventional air surveillance systems. The Capitol Hill gyrocopter took off from Gettysburg, Pennsylvania and wasn’t detected until it was about to land. Even if it had been detected, what would the response have been? Low-flying, small UASs and gyrocopters can be engaged with small arms or even missiles, but only if the defenders have sufficient warning and an accurate track of the target.
Confronting hybrid adversaries flying UASs, Israel has developed means to detect and track this new threat. They have a family of small, even man-portable, sophisticated radars that can be easily deployed to cover critical fixed targets such as the White House or Capitol Hill, or variable venues such as sporting events, parades or political rallies. Some of these do detection and tracking while others are fire control radars to direct anti-UAS/gyrocopter weapons. Israel (and other countries, including the U.S.) also have developed mast/tower-mounted electro-optical systems that can be integrated with radar to provide accurate detection, tracking and fire control. Such systems could be deployed rapidly to protect critical sites in the U.S. homeland.
Once detected, there is still the challenge of how to defeat an aerial IED. Israel used a Patriot anti-aircraft missile to down a Hamas UAS. This seems excessive against a UAS or gyrocopter flying down the Mall towards the White House or Capitol Hill. The best solution appears to be either a directed energy weapon or a jamming device that would block the guidance system or shut down the air vehicle’s avionics.
In the aftermath of Oklahoma City and 9/11, the U.S. government took steps to secure critical infrastructure and commercial aircraft against attack. With two events just this year, it is time for those responsible for securing the U.S. homeland to get serious about the potential threat of aerial IEDs.
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