A functional cloak of invisibility ? what?

[John]

No: HPFGUIDX 192373

Hi everyone.

As Clarkes Third Law states....

"Any sufficiently advanced technology is indistinguishable from magic."

This statement is also probably reversible, but I have yet to witness any indisputably genuine advanced magic and so cannot be sure this is the case. :o)

Yes, technology can undoubtedly produce many ideas and technologies that can operate to provide 'effective' if not 'actual' invisibility.

Starting with the earliest, but often most effective method there is, of course, simple physical camouflage. If anyone doubts the effectiveness of such 'crude' methods I dare them to walk around in a wood with a well camouflaged and well positioned and highly trained sniper trying to get a shot at them. What kind of flowers due you want for your funeral? :o

Another variation on simple methods is of course to utilise the concealing power of darkness.

Going up the scale to far more sophisticated methods one must look to technologies that can either make a man or machine 'radar invisible' and the now familiar 'stealth' technologies can do exactly that. They work by eliminating or at least drastically reducing the level of energy from radar systems that get reflected back to the detector/receivers of tracking systems. The plane's special shapes and also special radar energy absorbing coatings can make a modern stealth plane or ship appear far smaller or more distant than they actually are and make locking weapons onto them as targets very hard. But even these sophisticated stealth technologies are not true invisibility, and certainly cannot fool one of the most simple but also very sensitive detection systems, the Mk.1 eyeball! That is why stealth plane attacks are almost always carried out under the cover of darkness.

Ok, now we start to look to current research, (stealth is not cutting edge but is in fact an 80's technology that was kept top secret for a long time).

So we can, to some extent hide a plane or ship from radar to gain a tactical advantage, but visual detection in daylight is always a strong possibility. What can we do to circumvent that hazard and what can we do also to hide the heat emissions of living bodies or engines?

The idea of hiding things from visual detection is in part tacking a step back to the idea of camouflage, and in the past was done simply with paint effects, such as painting the bottom of a high flying aircraft to match the blue of the sky as seen from the ground. If this is done accurately to all intents and purposes such an aircraft can become 'invisible', but getting the colour match just right is impossible to maintain, as the colour of the sky is always changing.

However modern 'smart' materials that have chameleon type properties are being developed (some from the study of octopi and squid, who also have amazing camouflage abilities). Combined with cameras detecting their surroundings soon a plane, ship or tank etc will be able to constantly change it's colour to match it's background. For a stationary or very slow moving vehicle this idea (at least when viewed from a frontal position) can be very effective, however in the case of faster moving vehicles, like jets there is almost bound to be a slight lag in the system which might betray a plane's presence.

As to the 'heat signature' of a person or vehicle, some systems exist already to reduce visibility. In the case of a person a simple insulated suit and helmet can, for a very short time, prevent their body heat being detected. However, given that the heat of their body is trapped inside such a suit with nowhere to go it rapidly builds up and becomes unbearable, or indeed lethal if allowed to go on too long. 

Some more sophisticated ideas have been tried, variations on the 'insulation' idea. One such idea which can work for longer periods with the user remaining more comfortable is based on the underwear of a spacesuit, as worn by the astronauts on the moon. Some of the designs for such suits had an active liquid cooled garment worn next to the skin, which carried away the build up of heat. However the heat must eventually go somewhere and it is transferred to a backpack or 'suitcase' type unit which uses heat exchangers to keep the liquid body coolant at the right temperature. However this cooling unit itself gets hot in the process and would become highly detectable, so  in a 'stealth suit' liquid gas refrigerants are employed to try and balance out this heat and prevent the emission of this energy for as long as possible.

Using such a garment and cooling system a person could easily defeat the most commonly used of burglar alarm detectors, a passive infrared detector. These devices normally work by picking up an intruder's body heat moving in it's 'field of view'. Thus a criminal or assassin could carry out their work in a premises without fear of detection, at least for as long as their coolant pack holds out.

Vehicles too can have analogous 'heat camouflage' units fitted and indeed the military of many countries are working on such technologies right now, the best of which can make a large military vehicle like a tank 'invisible' in the heat spectrum, at least as long as it remains stationary.

So then, we have the ability at least partially to hide from visual, radar and heat detection, part way then to true invisibility, but there's still a long way to go. At least two other detection systems need to be thwarted.

In the case of a human body, we breathe and sweat in order to live and the chemicals emmitted by these 'life processes' can be detected and tracked, special absorbant filter materials and face masks might well help against such detectors however.

One final telltale signature remains however, that being sound. Betrayal by sound can either come from from passive tracking (at it's most simple just listening or using very sensitive machines for more accurate and analytical tracking like submarines do) or by active 'sound radar' similar to that a bat or dolphin use to track their prey. This later is hard to beat as any movement betrays one's presence, causing 'doppler shifts' in the sounds that reflect back to the sound sensor, although by clever surface design of materials, using absorbant materials the reflected sound can be much reduced. In the case of passive trackers just muffling noise sources will work, to a greater or lesser extent, depending on how much noise you want to hide. For instance a human creeping about on crepe soles tippy toe is not a very noisy event. But running a tank or jet engine very much is.

Combining all the suggested technologies and ideas above into one might provide a high degree of indetectability, but still we are not talking full, infallible and genuine invisibility. So what of the future?

Well the boffins reckon it may one day be possible to 'bend' light around a person or object and thus render it invisible in the true sense. This is already possible using tiny samples of special materials in tightly controlled laboratory conditions, but it ain't gonna happen anyday soon in the 'real world' on a large scale. It fact it never may come true, as just because you have a chunk of material with the right properties to be made invisible it doesn't necessarily mean that material has the right mechanical property to make part of a plane, a ship or even a human garment.

So meanwhile I guess we all better hope (as The Weird Sister's lyric says), that 'Magic Works' 'cos us muggles have a long way to go before we can duplicate Harry's cloak. ;o)
Many Blessings All.
John, (Oriondruid).