By David Hambling January 12, 2010
Photo: Defense Threat Reduction Agency
Iran’s nuclear facilities may be deeply-buried in a “maze of tunnels” — making them hard to find and even harder to destroy. But the Pentagon is working on some new technological tricks for exactly this kind of mission.
Iran’s president, Mahmoud Ahmadinejad, apparently takes a personal and close interest in tunnels — he’s a founder member of the Iranian Tunneling Association. Many of those facilities were built as underground shelters in the aftermath of the 1987 “War of the Cities,” when Iraq and Iran exchanged bombardments of Scud missiles.
There are hundreds of miles of such tunnels, created by giant boring machines. The underground locations provide defense and concealment — there is no telling what is a nuclear facility and what is an empty storage space. And, even if the entrance is visible, the extent and layout are unknown, making targeting difficult. Even if the site is attacked, the thickness of mountain rock makes them invulnerable to ordinary bombing.
That’s why the U.S. Air Force is rushing the Massive Ordnance Penetrator (pictured) into production. The MOP can punch through 60 feet of concrete, but this is the very bluntest of instruments for the job. There is more subtle technology to seek out and destroy such facilities.
Pentagon mad science division Darpa has an array of research projects devoted to Underground Facility Detection & Characterization. According to the program’s website, the agency’s Strategic Technologies Office is:
investing in sensor technologies that find, characterize and identify facility function, pace of activity, and activities in conjunction with their pre- and post-attack status. STO is also investigating non-nuclear earth-penetrating systems for the defeat of hard and deeply buried targets.
Seeing through solid rock might sound like a tall order, but Darpa thrives on challenge. One project is called Airborne Tomography using Active Electromagnetics, which builds on technology originally developed by the geophysical exploration industry. The ground is illuminated with electromagnetic energy — typically extremely low frequency — and the distortions on the return show the presence of underground facilities and tunnels. Some years ago, military-backed scientists at Alaska’s High Frequency Active Auroral Research Program (HAARP) were able to map out tunnels at depths of a hundred feet or greater. Papadopoulos, for example, says he wants to do another round of subterranean surveillance experiments. “Personally, I believe it can reach 1,000 kilometers. It [currently] can’t reach Iran, if that’s your question,” one of those researchers, Dennis Papadopoulos told Danger Room. “But if I put HAARP on a ship, or on an oil platform, who knows?”
Gravity Anomaly for Tunnel Exposure is even more sophisticated, using nothing more than variations in the local gravitational field caused by underground spaces. Extremely sensitive gravity gradiometers measure the difference in pull to map out underground voids. Darpa has already reached the stage of integrating the gravity gradiometer and signal processing payloads and mounting them in an unmanned aircraft, and have been “verifying performance in relevant geologic environments.”
Darpa is not neglecting the traditional methods of surveying underground structures, and there is a parallel Seismic and Acoustic Vibration Imaging effort. This might use untended ground sensors dropped from aircraft, or it might be something more advanced — Darpa’s website describes a mobile system using “an integrated, laser vibrometry system to detect seismic wave anomalies.” This might be another airborne sensor, though it might still need to drop something to produce shockwaves to create the seismic and acoustic vibration to be detected.
Darpa clearly believe that it is possible to locate and “characterize” underground facilities — this can mean everything from looking at what sort of vehicles come and go, to monitoring communications traffic or atmospheric sampling for traces of tell-tale nuclear material. It is hardly a surprise that Iran has complained of U.S. drone intrusions in recent years. Some observers suspect that the Air Force’s newest stealth spy drone in Afghanistan, the RQ-170 “Beast of Kandahar” may be sneaking over the border.
If detected, can such targets be attacked? The MOP may be capable of smashing through a lot of rock, but there are smarter approaches. The U.S. Air Force has developed skip-bombing techniques with bunker busters so that they arrive horizontally and can be aimed precisely at entrance doors. They may not destroy the entire facility, but if all the entrances are wrecked, then nothing can go in or out.
Thermobaric bombs like the BLU-118 “cave buster” have been specifically designed for attacking tunnel systems; the shockwave will travel far underground, going around corners and bends that would degrade normal blast waves. One test showed that it could kill human targets even when the blast had traveled through 1,100 feet of tunnels.
There are also more exotic options, like the Rocket Balls (or more correctly, “kinetic fireball incendiaries”) developed for the Defense Threat Reduction Agency. A warhead would release a large number of these rubberized balls of rocket fuel; once ignited they bounce around at high speed, spreading out by going through doorways and other openings and raising the surrounding temperature to over a thousand degrees within seconds.
Attacking the Iranian nuclear program would be a massive undertaking, though but not necessarily impossible. However, it would certainly appear that the United States is the only nation with the capability to carry out such an attack. As far as we know, Israel lacks both the sensor technology and the munitions for the job.