DARPA is unique among government agencies in not only being allowed, but encouraged, to pursue concepts and technologies that may not come into regular use for decades – if then. Those have included the Internet, aircraft stealth, unmanned air and ground vehicles, robots, directed energy, artificial intelligence, virtual reality, precision guidance, hypersonic flight, bionic prosthetics, controlling mechanical devices by thought, and flying cars.
During his time with DARPA, Smith led a research team investigating, among other things, invisibility. He has continued that work at Duke, with research into the electromagnetic properties of artificially structured materials – metamaterials – and the theoretical potential to design a material that would render objects invisible.
He also sees some “glimmer of reality” in the cloaking technology used by Star Trek’s Romulans to make their starships not only undetectable by sensors, but also invisible to the naked eye. However, while theoretically possible, based on the bending of light near massive gravitational sources, such as black holes, creating a portable device carried aboard a ship and being able to turn it on and off, in his words, leaves it “firmly the domain of science fiction.”
Perhaps surprisingly, Smith sees far greater potential for real-world invisibility in a science – rather than magic – based version of Harry Potter’s invisibility cloak. By using the right materials, he wrote, it might be possible to bend light around the cloak – which would create a sphere surrounding the object to be concealed – without requiring a black hole’s gravity well.
“The capabilities and limitations of cloaking will continue to be sorted out in the coming months and years, but there are some issues that are clear from the outset,” Smith wrote. “The cloak is a complicated structure. Not just complicated, but one that requires materials that are not known to exist. This appears to be one difficulty we can surmount by the use of artificial micro- and nano-structures that can substitute for the lack of conventional materials having the right properties. And while the cloaking structures are complex as materials go, they are nevertheless easily fabricated using available technologies.
Overall, then, the future of camouflage for land forces – indeed, all military and paramilitary units – appears on the edge of the first significant change since Ice Age hunters covered themselves with mud and leaves, first to trick game animals, later other humans during combat.
“One last point to consider is that the entire design paradigm that leads to the cloak – starting by transforming space and then determining the equivalent electromagnetic material – represents a new approach to optics,” Smith concluded. “Just five years ago, this idea of transformed optics might have been abandoned because the resulting material requirements would have been considered impractical.
“With the advent of metamaterials, that conclusion has now changed and we can envision entirely new classes of optical devices, invisibility cloaks being just one example. So, while we have been inspired by the invisibility of fictional worlds, perhaps the discoveries that might follow from transformation optics will in turn have an impact in fictional worlds – as well as in the actual world.”
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