AFP has an interesting, unsigned piece on an emerging terrorist threat: radio-controlled aircraft and small unmanned aerial vehicles (UAVs). They are readily available, relatively easy to build and operate, and extremely difficult to detect. In the hands of a terrorist organization, these "flying robots" could be used to deliver a small explosive device--or a chemical or biological payload--against "soft" targets.
As the article notes, some terrorists are already exploring this technology. Hizballah has obtained a small fleet of UAVs from Iran, and flew one over norther Israel on 11 April 2005. A videotape of the flight reportedly aired on a Hizballah TV station in Lebanon, and Israeli defense sources have reportedly confirmed a second flight as well. In both cases, the Israeli Air Force (IAF) was unaware of the intrusion until the UAV was well inside Israel's airspace, and had been sighted by ground observers. These flight(s) represented a major psychological and propaganda for Hizballah, which (until now) had no effective means of challenging the IAF's control of the Israeli skies.
With their small size (a wing span of five meters or less), use of lightweight materials, slow operating speeds and the ability to operate at low altitude, these remotely-piloted aircraft are almost impossible to detect on radar. Most of these devices have a radar cross-section that is miniscule; additionally, the "velocity gate" feature of most surveillance and target-tracking radars automatically eliminate targets operating at slow speeds, so a terrorist UAV, hang-glider or hobby aircraft would never appear on the screen--even if the radar managed to detect it.
These potential threats cover the spectrum from over-sized, radio-controlled model planes and helicopters, to hang-gliders and ultra-lights and small UAVs. Radio-controlled aircraft are inexpensive, and can be obtained on-line, or from a local hobby shop. Hang-gliders and ultra-lights are also readily available, mostly in kit forms that can be quickly assembled. UAVs are more expensive, but still within reach for a terrorist organization. And with scores of UAV manufacturers around the world (and no proliferation controls), terrorists are limited only by their financial resources and technical accumen. But even those restrictions can be easily overcome, as evidenced by Iran's transfer of UAVs to Hizballah, and the widespread use of GPS technology. GPS allows a terrorist ultralight, hang glider or UAV to navigate precisely, and reach pre-determine targets--without the use of complex data link signals that could be potentially jammed.
These types of aircraft have two limitations: a small payload, and in most cases, a relatively short range. However, these deficiencies are less important in a chemical or biological attack, where a small amount of agent, delivered to the right target by by remoted controlled ultralight or UAV, could have devastating results. The same holds true for a small, air-delivered explosive warhead, employed against such targets as oil refineries, POL storage, or power plants.
At least one expert claims that little attention has been paid to this threat. That's not entirely true. I know at least one Air Force organization that recently completed a major assessment of this threat, and the information has been presented to several high-level audiences. As for mitigation efforts, that's another story. In deployment situations, our military forces have the resources to deal with terrorist ultra-lights and UAVs (shoulder-fired SAMs, attack aircraft, helicopters), but linking them together in a viable defensive scheme remains problematic. In a homeland defense scenario, the problems are more acute, and deserve serious consideration. The potential threat from this type of technology will only grow in the years to come.
A slightly scary footnote: the article references a New Zealand engineer, Bruce Simpson, who has demonstrated how terrorists could build a crude--but effective--cruise missile for under $5,000, using off-the-shelf technology. Simpson's website recounts those efforts--and pressure from the U.S. and New Zealand governments to shut down the project.