Cloaking devices
SCIENCE FICTION SOURCE:
Too many to list
IN SCIENCE FICTION, cloaking devices are very handy bits of kit that allow an enormous and heavily armed spacecraft – piloted by Klingons, for instance – to approach another craft in circumstances where hostile intent is not revealed until the last moment.
Such shields are thus the Trekky, techy equivalent of Harry Potter’s invisibility cloak, and while no one is suggesting that large-scale induced vanishing is an actual practical idea – at least yet – cloaking of another type was demonstrated in proof-of-concept earlier this year.
Not everything has to be about the visuals. Submarines, for instance, prowl about underwater looking for enemies using other senses – especially sound. It would be tactically advantageous, thus, if the searching sonar beamed out from a hostile craft could be prevented from revealing the presence of one’s own sub, making it, to all intents and purposes, invisible.
And that, in miniature, is what Amanda Hanford, an acoustical engineer from Pennsylvania State University, recently unveiled in the US city of Minneapolis, at a meeting of the Acoustical Society of America.
Hanford’s invention looked rather like a metre-high cheese grater. The device generates a complex array of acoustic phases which combine to effectively cancel out the giveaway reflections of probing sonar beams. To all intents and purposes, thus, the grater becomes invisible – or, at least, inaudible.
The machine uses “metamaterials”, which are complex structures composed of arrays of individual components significantly smaller than the wavelength of the sound waves they are intended to hide from.
At present, the prototype can squish only a narrow range of frequencies and is thus a long way from being able to hide a submarine in plain sight. Still, it’s a beginning. Even the Klingons had to start somewhere.