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Newly-tested drone could trace nuclear weapon origins

Sandia's Harvester

If a nuclear weapon were unexpectedly detonated anywhere on the planet, unmanned drones could be used to sniff out the tell-tale radioactive particles in the atmosphere determine who the weapon belonged to.

Sandia National Laboratories said it has developed and successfully tested airborne pods that can be mounted on unmanned aerial vehicles and sent up to rapidly collect airborne radioactive samples in the wake of such an explosion.

A UAV, said a Jan. 9 statement from Sandia, is relatively inexpensive and could fly right down the throat of telltale radiation over a broad range of altitudes without exposing a human crew to hazards.

Sandia said its airborne particulate collection system, which is calls “Harvester,” had recently demonstrated those kinds of capabilities in a test over Grand Forks Air Force Base in Grand Forks, ND, in late September. The Harvester system, said the agency, “tasted” the atmosphere with two particulate sampling pods. A third pod would provide directional guidance for a real event by following the trail of gamma radiation.

The three pods, with additional hardware, software and ground-control equipment, are expected take their place on aircraft in the Air Force’s investigatory arsenal in the next few years, said Sandia.

No radioactive isotopes were used in the Grand Forks test, explained the laboratory. The pods, it said, were able to collect and identify naturally occurring radioisotopes of lead and bismuth produced from the radioactive decay of atmospheric radon. Additionally, radioactive beryllium-7 produced from cosmic ray-induced break-up of naturally occurring carbon-14, also showed up on the filters, providing a uniform measure for debris distribution.

The test over North Dakota was a formal Department of Defense (DoD) Joint Capability Technology Demonstration (JCTD) that coupled the Harvester modular pods to the long wings of a Department of Homeland Security Customs and Border Protection-provided MQ-9 Reaper UAV  -- the  more powerful cousin of the Predator.

The Harvester’s Directional Gamma Radiation Sensor (DGRS), said Sandia, helps guide the aircraft toward the radioactive plume using four large sodium iodide radiation detectors and a complex processing algorithm. The Harvester equipment operator tells the pilot, who is located far away in a UAV ground control station, to fly toward the plume’s “hot spot.”

Air passes through the samplers, each about the size of a small snowmobile, as the Reaper cruises at 200 mph, according to Sandia. This rams particles into filter paper like light hitting a photographic plate, causing the particles to stick to the filter fibers, it said. A separate radiation sensor analyzes the filter in real time to estimate the type and quantity of radioactive particles collected, with more extensive examination of the filters occurs after the aircraft has landed.

Because gas analysis can complement particle analysis, Sandia said it is developing a third type of pod called the Whole Air Sampling Pod (WASP) to demonstrate the feasibility of collecting multiple, large-volume air samples that can be analyzed for radioactive gases. Radioxenons, radioisotopes of the noble gas xenon, if detected, can provide a tell-tale indication of a nuclear detonation, it said.

According to Sandia, Harvester was developed with support from the Albuquerque office of National Technical Systems, an international engineering firm. The early research and development phase was funded by the National Nuclear Security Administration’s Office of Nonproliferation Research and Development. The later development and qualification phase was funded by the Defense Threat Reduction Agency and the Office of the Secretary of Defense’s Acquisition, Technology and Logistics Rapid Fielding Office as part of the JCTD.