During the recent Nuclear Security Summit in Washington DC, British Prime Minister David Cameron made the ominous assessment that the Islamic State in Iraq and Syria (ISIS) is seeking to use drones to detonate “dirty” bombs over Western cities. While Cameron and other world leaders are right to be concerned about the prospect of more ISIS attacks on metropolitan targets, this particular scenario said much more about the evolving threat of the drone as an effective terrorist weapon than that of a dirty bomb or radiological dispersion device.
A dirty bomb explosion would not be exponentially more catastrophic than a conventional one. As with any bomb, people within the immediate vicinity of the explosion would likely be killed or wounded by the force of the explosion. Those within a slightly greater radius would absorb high doses of radiation that could increase the risk of dying from radiation poisoning – perhaps greater than 50 percent – if left untreated. While it’s possible a dirty bomb could be designed to disperse radioactive material over several blocks, depending on the force of the explosion, the effects of that dispersion must be kept in perspective.
Dr. Richard A. Muller explained in Physics for Future Presidents: The Science Behind the Headlines that exposure to radiation is itself not fatal. What matters is the amount of radiation to which a person is exposed, and for how long. The dispersal of radioactive material over a larger area causes it to lose some potency. Individuals farther away from the blast epicenter – even if they don’t evacuate immediately – will be exposed to a radiation level significantly below what is needed tocause radiation poisoning. Humans already live with a 20 percent chance of dying from cancer brought on by causes found in nature, so consistent exposure to low levels of radiation creates only a marginal increase on top of that.
“The biggest danger from a radiological weapon is the misplaced panic and overreaction that it would cause,” Muller wrote. “A dirty bomb is not really a weapon of mass destruction, but it is potentially a weapon of mass disruption.”
The real issue in Cameron’s scenario is not the dirty bomb itself so much as the drone carrying it.
Today’s civilian drone – whether purchased as a single platform or assembled from disparate component parts – offers significant tactical advantages to terrorists. Strap a conventional explosive to a drone, and you have a remote control precision-guided bomb that can be flown into or onto a target of choice. The drone offers the advantage of evasion, as the operator does not have to plant the bomb at the target before detonation or get close to the target as would a suicide bomber, making identification and interdiction more difficult for law enforcement.