Defense Technology International - May 2008 - (Page 45)

U.S. MARINE CORPS Double Duty The Defense Advanced Research Projects Agency (Darpa) is in the early stage of a research effort aimed at development of munition cases that provide structural integrity and explosive force. According to a solicitation posted in April, Darpa’s Reactive Material Structures program will focus on high-strength materials that withstand high stresses, presumably during transport, handling and deployment, yet “rapidly release energy upon demand”—i.e., when detonated. The materials or material systems proposed must have high density, large enthalpy (thermodynamic potential), reactive ingredients and “the mechanism(s) to convert consolidated structural material into large-surface-area powder, disperse and ignite the powder to produce a high-intensity blast.” Darpa’s work continues efforts by the Pentagon to improve the safety of ordnance without sacriﬁcing destructive power. The Pentagon announced in 1999 that it wanted an arsenal of insensitive munitions, yet only a few new weapons have qualiﬁed (DTI January/February 2007, p. 38). ■ 1 STOCKBYTE PHOTOS Keeping Secrets Separate research programs at the University of Calgary in Canada and the Tokyo Institute of Technology bode well for quantum cryptography, a means of coding information that will reportedly be impossible to crack. Teams at both schools recently stored a “squeezed vacuum” in a gas of rubidium atoms and retrieved it. A squeezed vacuum in quantum physics is the “noise” generated by light that actually increases in an electromagnetic ﬁeld when a light source is turned off, says Prof. Alexander Lvovsky at Calgary. The squeezed vacuums were stored for short peri- 2 ods—1 microsec. in Calgary, 3 microsec. in Tokyo. But the results prove it can be done. In the future, Lvovsky says, coded photons of light will be transmitted through optical ﬁbers and retrieved. The method will be secure because any effort to tap or otherwise measure the signals will destroy the data they carry. Unlike conventional optical communications, which use ampliﬁers to measure and reduce signal attenuation, quantum cryptography needs repeaters along a route to recapture and retransmit signals before they weaken. Lvovsky says quantum communication is at least 5-10 years from commercialization. ■ OVER THE EDGE Deep Black Scientists at Rensselaer Polytechnic Institute in Troy, N.Y., have developed a material that absorbs 99.955% of light, making it the blackest substance ever created. The team, led by Prof. Shawn-Yu Lin, used long, low-density, vertically aligned carbon nanotubes to achieve the extreme light absorption. The nanotubes have a low refractive index and random surfaces. Gaps and holes in the structure trap light, says Lin, giving the material, formulated as a thin coating, a refractive index (RI) of 0.045%. The previous benchmark for black was a nickel and phosphorus material with 0.17% RI. The U.S. National Institute of Standards and Technology has a black that reﬂects 1.4% of light. The RPI material has uses in military, scientiﬁc and commercial applications. Its light absorption would make soldiers and vehicles harder to see at night; the material could complement stealth technology; and coating satellites with it would improve the accuracy of many operations. The work was funded by the U.S. Energy Dept. and Focus Center New York for Interconnects. ■ AviationWeek.com/dti MAY 2008 DEFENSE TECHNOLOGY INTERNATIONAL 3 45 U.S. ARMY http://www.nxtbook.com/nxtbooks/aw/dti0107/index.php?startid=38 http://AviationWeek.com/dti

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Defense Technology International - May 2008 Contents Around the World Science Watch Tech Watch Learn and Live Think Again Vive la Difference En Route Out of the Box Package Deal On Watch Inside Job Programs Update The Net Back to the Future Busy Signal Mighty Mites Hull of an Idea Tough Enough Cutting Edge First Person In Review Insight

Defense Technology International - May 2008

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