atomic_plane.JPGThe first line sure is juicy: "After more than six decades of research, the first atom-powered airplane is cleared for takeoff."And even if the substance doesn't quite back up the tantalizing intro in the current Popular Mechanics -- which it doesn't -- this is still an interesting concept.The attraction of a nuclear plane is that it doesn't run out of fuel. Convert a drone to atomic power, and it could stay aloft just about forever, the thinking goes.The nuclear drone wouldn't have a traditional fission reactor, running on uranium or plutonium. Instead, it would be powered by hafnium-178."In the late 1990s, researchers at the University of Texas in Dallas made a remarkable and unexpected discovery about [halfnium]," the magazine says. "When they bombarded the metal with 'soft' X-rays like those your dentist uses to examine your teeth, the metal released a burst of gamma rays 60 times more powerful than the X-rays."This reaction could be safer than conventional ones, the magazine argues."The gamma ray output drops precipitously the moment power to the X-ray machine is turned off... Since it produces only gamma radiation, less shielding is required. And should an accident occur, there is less of an environmental concern than with fission. Hafnium-178 has a half-life of only 31 years compared to thousands of years for other reactor fuels. In addition, unlike uranium or plutonium, hafnium-178 cannot support a chain reaction, which means it cannot be used to make rogue nuclear weapons."But, despite the potentially attractive features, an atomic drone is nowhere near takeoff."Project managers for Northrop Grumman and the U.S. Air Force Research Laboratory tell Popular Mechanics they have begun discussions that could lead to the conversion of a Global Hawk [drone] to a nuclear-powered aircraft They have not yet signed a contract to convert a Global Hawk to nuclear power, they are aware of discussions taking place within the Air Force." (emphasis mine)THERE'S MORE: Some scientists are pouring cold water all over the halfnium idea, reader MS points out. "May not make physical sense," was the opinion of 5 of 12 Pentagon researchers appointed to look into halfnium bombs.AND MORE: Defense Tech "deserves better than Popular Mechanics doing a fair imitation of the National Inquirer," says Los Alamos consultant and nuclear proliferation expert Russell Seitz.With so-called "isomers" like halfnium-178, he writes, "energy has both to be put in and gotten out. The mere fact that more and better physicists using fiercer x-ray sources and more sensitive gamma detectors can't get any signal out of the same isotopes -- even upon many experimental iterations and variations -- satisfies me that [this] is just another example of the economics of desire."AND MORE: The Defense Department was looking at atomic planes back in the 1940's, reader JM notes, with a project called "Nuclear Energy for the Propulsion of Aircraft," or NEPA. And for a year or so, the Pentagon considered irradiating human test subjects, to see how much nuclear exposure pilots could take. After Manhattan Project scientist Dr. Joseph Hamilton pointed out that such experiments would have "a little of the Buchenwald touch," the idea was finally, and thankfully, dropped.

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