Invisibility cloaks may be just around the corner

Mar 04, 2011 By Marlene Cimons
Elena Semouchkina tests a microwave dielectric cloak in an anechoic chamber--a cave-like compartment lined with charcoal-gray foam cones to abosrb sound. Credit: Elena Semouchkina, ECE Department, Michigan Tech University

In 1897, H.G. Wells created a fictional scientist who became invisible by changing his refractive index to that of air, so that his body could not absorb or reflect light. More recently, Harry Potter disappeared from sight after wrapping himself in a cloak spun from the pelts of magical herbivores.

Countless other fictional characters in books and films throughout history have discovered or devised ways to become invisible, a theme that long has been a staple of science fiction and a source of endless fascination for humans. Who among us has never imagined the possibilities? But, of course, it's not for real.

Or is it?

While no one yet has the power to put on a garment and disappear, Elena Semouchkina, an associate professor of electrical and computer engineering at Michigan Technological University, has found ways to use to capture rays of and route them around objects, rendering those objects invisible to the human eye. Her work is based on the transformation optics approaches, developed and applied to the solution of invisibility problems by British scientists John B. Pendry and Ulf Leonhardt in 2006.

"Imagine that you look at the object, which is placed in front of a ," she explains.

"The object would be invisible for your eye if the light rays are sent around the object to avoid scattering, and are accelerated along these curved paths to reach your eye undistinguishable from direct straight beams exiting the source, when the object is absent."

At its simplest, the beams of light flow around the object and then meet again on the other side so that someone looking directly at the object would not be able to see it--but only what's on the other side.

"You would see the light source directly through the object," said Semouchkina. "This effect could be achieved if we surround the object by a shell with a specific distribution of such material parameters as and permeability."

She and her collaborators at the Pennsylvania State University, where she is also an adjunct professor, designed a nonmetallic "invisibility cloak" that uses concentric arrays of identical glass resonators made of chalcogenide glass, a type of dielectric material--that is, one that does not conduct electricity.

In computer simulations, the cloak made objects hit by infrared waves--approximately one micron, or one-millionth of a meter long--disappear from view.

The potential practical applications of the work could be dramatic, for example, in the military, such as "making objects invisible to radar," she said, as well as in intelligence operations "to conceal people or objects."

Furthermore, "shielding objects from electromagnetic irradiation is also very important," she said, adding, "for sure, the gaming industry could use it in new types of toys."

Multi-resonator structures comprising Semouchkina's invisibility cloak belong to "metamaterials"--artificial materials with properties that do not exist in nature--since they can refract light by unusual ways. In particular, the "spokes" of tiny glass resonators accelerate light waves around the object making it invisible.

Until recently, there were no materials available with the relative permeability values between zero and one, which are necessary for the invisibility cloak to bend and accelerate light beams, she said. However, metamaterials, which were predicted more than 40 years ago by the Russian scientist Victor Veselago, and first implemented in 2000 by Pendry from Imperial College, London, in collaboration with David R. Smith from Duke University, now make it possible, she said.

Metamaterials use lattices of resonators, instead of atoms or molecules of natural materials, and provide for a broad range of relative permittivity and permeability including zero and negative values in the vicinity of the resonance frequency, she said. Metamaterials were listed as one of the top three physics discoveries of the decade by the American Physical Society.

"Metamaterials were initially made of metallic split ring resonators and wire arrays that limited both their isotropy (uniformity in all directions) and frequency range," Semouchkina said. "Depending on the size of split ring resonators, they could operate basically at microwaves and millimeter (mm) waves."

In 2004, her research group proposed replacing metal resonators with dielectric resonators. "Although it seemed strange to control magnetic properties of a metamateral by using dielectrics, we have shown that arrays of dielectric resonators can provide for negative refraction and other unique properties of metamaterials," she said. "Low loss dielectric resonators promise to extend applications of metamaterials to the optical range, and we have demonstrated this opportunity by designing an infrared cloak."

Semouchkina and colleagues recently reported on their research in the journal Applied Physics Letters, published by the American Institute of Physics. Her co-authors were Douglas Werner and Carlo Pantano of Penn State and George Semouchkin, who teaches at Michigan Tech and has an adjunct position with Penn State.

The National Science Foundation (NSF) is funding her research on dielectric metamaterials and the team's applications with a $318,520 award, but she plans to apply for an additional grant to conduct specific studies into invisibility cloak structures.

Semouchkina, who received her master's degree in electrical engineering and her doctorate in physics and mathematics from Tomsk State University in her native Russia, has lived in the United States for 13 years, and has been a U.S. citizen since 2005. She also earned her second doctorate in materials in 2001 from Penn State.

She and her team now are testing an all-dielectric rescaled to work at microwave frequencies, performing experiments in Michigan Tech's anechoic chamber, a cave-like compartment in an electrical energy resources center lab, lined with highly absorbent charcoal-gray foam cones.

There, "horn" antennas transmit and receive microwaves with wavelengths up to several centimeters, that is, more than 10,000 times longer than in the infrared range. They are cloaking metal cylinders two to three inches in diameter and three to four inches high with a shell comprised of mm-sized ceramic resonators, she said.

"We want to move experiments to higher frequencies and smaller wavelengths," she said, adding: "The most exciting applications will be at the frequencies of visible light."

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jjoensuu
1 / 5 (6) Mar 04, 2011
Unfortunately, looking at the behavior I see in the news, invisibility cloaks (just as teleportation) pose a problem vector: access to ladies locker rooms.

Call me dumb but some stuff would not surprise me.
baudrunner
1 / 5 (4) Mar 04, 2011
This will work in the environment where this research is taking place - a sound proof room with shock and vibration absorbing walls and floor. What is needed is some kind of regulatory feedback mechanism that eliminates the vibration and noise that exist in a normal environment. These impact significantly on the wave bending efficiency of the meta-material, prohibiting its use in the field. Nevertheless, this represents a new level in the science of meta-materials, and that makes this development very exciting.

Some day in the future, genetic scientists will study the feathers of birds, the hair of mammals, the scales of fish, the irridescence of butterfly wings etc. and intelligently design a true invisibility cloak that can be grown in the laboratory. Harry Potter's coat is not so far off.
sstritt
4.5 / 5 (17) Mar 04, 2011
Invisibility cloaks may be just around the corner

You won't see it coming
stealthc
1 / 5 (5) Mar 04, 2011
non-article, quartz can do it already.
TheGhostofOtto1923
2.5 / 5 (19) Mar 04, 2011
"We want to move experiments to higher frequencies and smaller wavelengths," she said, adding: "The most exciting applications will be at the frequencies of visible light."

-Yeah but the most useful might be in deflecting harmful radiation or even micrometeoroids around spacecraft, instead of trying to stop them with brute force. Could also work against battlefield lasers and particle beam weapons? Bullets maybe?? Shields up!
rgwalther
1 / 5 (1) Mar 04, 2011
I almost just saw one.
TheGhostofOtto1923
2.6 / 5 (17) Mar 04, 2011
As there may be those who balk at the suggestion of deflecting particles with these materials, I offer this:
"We show that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics. A microstructured, asymmetric post array forms the core hydrodynamic element and is used as a building block to construct microfluidic metamaterials and to demonstrate refractive, focusing, and dispersive pathways for flowing beads and cells."
jscroft
1 / 5 (4) Mar 04, 2011
Invisibility cloaks may be just around the corner.


Yes, but how would you know?
trekgeek1
1 / 5 (1) Mar 04, 2011
The best defense for a women's locker room would be a door. If a door opens without someone there, you've got a problem. Combine that with thermal cameras if you want.
Au-Pu
1 / 5 (4) Mar 04, 2011
The biggest concern, if and or when they get something working in the visible light spectrum, will be access to these materials by terrorists.
As far as the use of magnetic resonance for prevention of radar detection speak to the people at Skunk Works who built the Blackbird.
ottoisasciencegroupie
3.2 / 5 (9) Mar 04, 2011
@Otthole

It's always good for a chuckle when you try posting about something besides religion or politics, rare though that may be. Here you are again demonstrating your total ignorance of hard science:

Yeah but the most useful might be in deflecting...micrometeoroids around spacecraft

Fail.

As there may be those who balk at the suggestion of deflecting particles with these materials, I offer this:
""We show that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics."


There's no fluid in space, Stimpy. Since micrometeoroids aren't hydrodynamically coupled to a fluid, this method obviously won't work to deflect them.

Best if you just stick to the blustery rhetorical rubbish you love so much, you know, all the highly subjective grand-standing that has nothing to do with science.
TheGhostofOtto1923
2.6 / 5 (18) Mar 04, 2011
Best if you just stick to the blustery rhetorical rubbish you love so much, you know, all the highly subjective grand-standing that has nothing to do with science.
And you are obviously an otto groupie.

You have a stunted imagination. Fluid is matter no? Shake your head. Hear the sloshing sound? Feel the inertia?

How about this? Careful - there are some big words in it:
http
://arxiv.org/pdf/0801.2223

-And here are some adults discussing this very subject:
http
://www.talk-polywell.org/bb/viewtopic.php?t=1601&sid=47d0f4f89cf08739bc9709bf8456ff10

-I find these things on GOOGLE.

Otthole hehe what a kid
SincerelyTwo
1 / 5 (2) Mar 05, 2011
Actually, the invisibility cloak Harry Potter uses was The Cloak of Invisibility which came from Death himself as described by the following fictional fairy tale (which turns out to be based on a true story in that fictional universe):

http://harrypotte...Brothers

That invisibility cloak specifically will never lose its abilities. The cloak was passed down the family line until James Potter received it, who handed it to Dumbledore, who then passed it anonymously to Harry Potter.

Also, while they are a part of the fictional universe I don't recall any of the other type of invisibility cloaks ever being depicted in the books or the movies.
FrankHerbert
0.8 / 5 (51) Mar 05, 2011
I'd rather see religious discussions around here than harry potter treatises. uggggggggggggggggggggggggggggggggggggggggggg
kaasinees
2 / 5 (8) Mar 05, 2011
Also, while they are a part of the fictional universe I don't recall any of the other type of invisibility cloaks ever being depicted in the books or the movies.


Romulan space ships?
ottoisasciencegroupie
3.5 / 5 (8) Mar 05, 2011
@Otthole
You switched horses: first you claimed that hydrodynamic cloaking (http ://www.princeton.edu/~chouweb/publications/202%20Morton_Hydrodynamic%20Metamaterials_PNAS_2008.pdf) could protect a spacecraft from micrometeoroids, which is false...and a really dumb thing to say, frankly. And now you're citing an unrelated paper about quantum cloaking, which is irrelevant because the scale of the cloak is related to the Schrodinger wave function of the incident particle. So unless your cloak approaches Planck scale, you won't be shielding the Enterprise from any 1/2 gram micrometeroids this way, Sulu. And metamaterial cloaking is extremely wavelength-dependent, and therefore useless to shield even micron-scale regions from anything resembling the vast particle spectrum of the interstellar medium. By the way, that was mentioned at your discussion link, but science groupies do tend to miss little details like fundamental physical principles.
TheGhostofOtto1923
2.8 / 5 (16) Mar 05, 2011
spacecraft from micrometeoroids, which is false...and a really dumb thing to say, frankly.
First, consider the fact that your brain is damaged. Spend some time with that. Second, consider that I was offering different ways in which metamaterials can affect matter, which offers some hope that they may be used in the future to deflect interstellar particulates without slowing a spacecraft.

This was the point of that discussion on the polywell site yes no yes? Perhaps even to funnel them for use bussard-style without a large, messy magnetic field. Your objections sadly are based only on some of what we know about them at present, and do not consider what we might learn about them in the future. Look up the words myopic and intractable in GOOGLE.

Third, revisit the fact that your brain is debilitated and it is having a significant effect on how you perceive the actions of others. Then go and finish your homework. Dick.
ottoyanksinamirror
3.7 / 5 (9) Mar 05, 2011
@Ottiot

Lol, this is like watching a one-legged donkey struggling to escape from a pool of quicksand.

Your own citation refutes your hair-brained claim, but the math is too far over your head for you to grasp it...so you think you can bluff your way out of this. Funny.

Ecoute et repete: Metamaterial cloaks will *never* shield spacecraft from micrometeoroids because the shield has to be at the scale of the wavelength of the incident particle (which instantly rules out everything more massive than a proton), and because the principle of matter cloaking requires that the cloak be tuned to a single specific incident energy level. Thats why the authors of the paper you cited never even mention your dewy-eyed fantasy about using matter cloaks to shield a spacecraft from interstellar debris. And this is not myopia on my part; these are the intrinsic limitations to exploiting the wavefunction of any material object, which youd know if you could read the math in your own citation.
ottoyanksinamirror
3.5 / 5 (8) Mar 05, 2011
@Ottistic

Also, your dumb new proposal for using cloaking tech as a substitute for the magnetic scoop of a Bussard ramjet is simply absurd, because you've replaced a huge electromagnetic field with a metamaterial cloak the diameter of an Earth-sized planet or larger. Come to think of it, Zephir had a better grasp of scientific reasoning.

Btw, some guy speculating on a chat board about science that's clearly out of his depth, is not a substitute for supporting evidence, Ottiot. And Google is only as good as the operator. Here's a clue: if the only place your brilliant new physics idea is mentioned, is a single post by one guy at one tiny chat board (and that post got shot down by someone brighter), then you probably have no idea wtf you're talking about, slugger.

Face it dude: you have a weaker grasp on hard science than most Star Trek fans, and you'll never comprehend physics because you obviously can't understand the math that describes it.
TheGhostofOtto1923
2.9 / 5 (17) Mar 05, 2011
Hey I'm just throwing ideas out there which are bouncing off that thick carapace of yours. How big does a scoop need to be to gather sufficient interstellar ions at relativistic speeds? Would it work with stellar winds? Is your homework for French class? Who knows the answer to these things?

Hey how about this: we plasmatize micrometeoroids with the appropriate energy beams so they can be affected by plasmonic metamaterial constructs? How about that dick? Impacts with a sacrificial primary screen might be enough to dissociate particles and enable them to be deflected without expending energy. How about that dick?

Maybe this thing would allow you to overcome your intransigence with wavelength:
http
://en.wikipedia.org/wiki/Superlens
TheGhostofOtto1923
2.9 / 5 (17) Mar 05, 2011
the only place your brilliant new physics idea is mentioned, is a single post by one guy at one tiny chat board
Now trust me, I've seen it in another board as well. Here's a paper on matter wave and metamaterial interaction:
http://iopscience...1/215301

-How about that dick? Dick? Must be past his bedtime-
jmcanoy1860
1 / 5 (2) Mar 05, 2011
Invisibility cloaks may be just around the corner

You won't see it coming


ba dum bum
ottoyanksinamirror
3.3 / 5 (7) Mar 05, 2011
@Ottholio
I'm not here to help you. I only spoke up to point out that, for someone who incessantly bashes others over the head for being "unscientific," you, sir, are utterly inept at hard scientific analysis. The only reason you're not routinely humiliated here is that you usually confine your infantile and inflammatory posts to the highly subjective "soft sciences," such as sociopolitical topics, where there are frequently no real answers, only opinions.

However, other interested parties may find an intriguing if beleaguered solution to the key hurdles of interstellar spaceflight in the field of "metric engineering," which involves the manipulation of spacetime itself. The "Alcubierre drive," specifically, is a conceptually-hopeful if thorny idea that might, within a more advanced theoretical framework, someday overcome both the shielding and the velocity hurdles to manned interstellar spaceflight.

http
://www.nasa.gov/centers/glenn/technology/warp/ideachev_prt.htm
DevonMcSchnitzel
1 / 5 (2) Mar 06, 2011
"Until recently, there were no materials available with the relative permeability values between zero and one, which are necessary for the invisibility cloak to bend and accelerate light beams, she said."

Accelerate light beams? Am I missing something. Since when can the speed of light be accelerated?
bluehigh
1.8 / 5 (5) Mar 06, 2011
Its possible to bring light to a complete stop. So when you take off the brakes, light accelerates. As we all know (or should) light travels at different speeds depending on the medium it is travelling through. Light however does have a maximum speed - as far as we know.

A side question though might be - what is the rate of acceleration as light transits one medium to another?

otthole88
1.6 / 5 (7) Mar 06, 2011
you, sir, are utterly inept at hard scientific analysis.
As in totally and completely inept in absolutely every scientific topic known to humankind. Useless hyperbole. Sounds familiar.
The only reason you're not routinely humiliated here is that you usually confine your infantile and inflammatory posts to the highly subjective "soft sciences," such as sociopolitical topics, where there are frequently no real answers, only opinions.
yabbayabba. And of which, ottos opinions excel.
Alcubierre drive,
Where'd that come from? What's that have to do with metamaterials? You can't dance so you decide to sing a song for the audience? Dick?
shtoots
4.2 / 5 (5) Mar 06, 2011
Hey otto, couldnt help but notice how much of a dumbass you are. Keep it up.. lol.
TheGhostofOtto1923
2.3 / 5 (12) Mar 06, 2011
Hey otto, couldnt help but notice how much of a dumbass you are. Keep it up.. lol.
Hey thanks dick. How many nicks you got anyways?

On another unrelated note, I didnt know dick was actually an author:
http
://www.truth-out.org/how-rich-soaked-rest-us68155

-Although I can assume he would agree with the sentiment in this article.

Dick- you have still to address the possibility of converting interstellar micrometeoroids into ions which could be diverted by metamaterials. This would require far less energy than your planet-sized magnetic fields.
paulthebassguy
3 / 5 (4) Mar 06, 2011
Since light beams are essentially routed around the object, anyone who is in that object will not be able to see out correct?

Such a shame, I would have loved to use this to sneak into the ladies locker rooms.
ottoisasciencegroupie
3.4 / 5 (5) Mar 06, 2011
"Until recently, there were no materials available with the relative permeability values between zero and one, which are necessary for the invisibility cloak to bend and accelerate light beams, she said."

Accelerate light beams? Am I missing something. Since when can the speed of light be accelerated?

Remember your vector notation from high school physics: acceleration is any change in velocity, and velocity is a vector that possess both speed and direction components. Since these photons are following a curved trajectory through the lattice, they're accelerating by changing direction even if their instantaneous velocity within the material remains constant.
ThatCamel
5 / 5 (4) Mar 06, 2011
i liek this otto guy. he is funnai lol

But seriously, he's funny.
ottoisasciencegroupie
3.3 / 5 (7) Mar 06, 2011
you, sir, are utterly inept at hard scientific analysis.

As in totally and completely inept in absolutely every scientific topic known to humankind.

As I said, all the hard science anyway. I've had occasion to see just about every post you've ever made here, whilst down-voting them all repeatedly, lol, which ironically makes me the most qualified member on the subject of otto's crippled grasp of scientific reasoning. And I've concluded that you've probably always been a "science groupie," but this appears to be backed up only by some light pop science reading, such as Discover magazine articles and that ilk. The real reason you seem to post here appears to be this: Physorg is both active, and unmoderated, so here you can troll your shriveled little heart out until your cheeks turns blue. No, not the ones on your face.
ottoisasciencegroupie
3.3 / 5 (7) Mar 06, 2011
And of which, ottos opinions excel.

That's merely your opinion. In fact you seem to get down-voted more often when you're in "self-appointed and self-aggrandizing Physorg pundit" mode, than when you actually have a pertinent fact to share. Btw, everyone knows that people who refer to themselves in the third person are total failures at life. Fyi.
Alcubierre drive

Where'd that come from? What's that have to do with metamaterials? You can't dance so you decide to sing a song for the audience? Dick?

Metamaterials won't help you with interstellar travel; we've been over this twice already. Metric engineering is currently the most hopeful solution to the problems posed.
Hey otto, couldnt help but notice how much of a dumbass you are. Keep it up.. lol.

Hey thanks dick.

Not me, obviously. So yeah, score one for shtoots.

On another unrelated note, I didnt know dick was actually an author:

Also not me. Lol, you're awful at this.
ottoisasciencegroupie
3.3 / 5 (7) Mar 06, 2011
Dick- you have still to address the possibility of converting interstellar micrometeoroids into ions which could be diverted by metamaterials.

Whooosh! So all that stuff about energy levels and wavelengths just flew overhead like a Lockheed spy plane, huh? Look man, I've already pointed out that metamaterials won't work for diverting micrometeoroids, and the precise reasons why. The failing to comprehend is your problem. I can't make it any clearer until you have at least a passing familiarity with rudimentary quantum mechanics like the Schrödinger wave equation, or at least de Broglie wavelength and the wave-particle behavior of atomic nuclei.

This would require far less energy than your planet-sized magnetic fields.

Lol, you're getting everything all boogered up, dude. The huge electromagnetic field pertained to the Bussard ramjet, not the particle shielding question. Apples and oranges.

More studying and thinkingless pouting and pooping.
Eco_R1
1 / 5 (1) Mar 07, 2011
you would not be able to see anything from the inside out, due to non of the surrounding light entering through the cloak.
jscroft
1.8 / 5 (5) Mar 07, 2011
you would not be able to see anything from the inside out, due to non of the surrounding light entering through the cloak.


A couple of people have brought this up, and it's tactically interesting.

Say I HAD a cloaking device. If I have to interact with the outside world or move through it--and if not, why would I need a cloaking device?--I'll need to turn it off (and expose myself) every once in a while and sample my environment in order to avoid running into things. The duty cycle of this process will be determined by my tactical dynamics... the faster things are moving, the higher my required sampling frequency and hence my visibility.
jscroft
1.8 / 5 (5) Mar 07, 2011
Furthermore, if I'm going to the trouble of using a cloaking device, then my sensing techniques are likely to be passive, right? So any targeting fixes I acquire will have to be evolved over time via target motion analysis... and the quality of those fixes will tend to degrade as I reduce my sampling frequency.

The bottom line: even "perfect" cloaking is going to involve a real trade-off between stealth and sensor capability, which is more or less exactly the dynamic we face now, as anybody who has ever tracked a submarine will readily admit.
TheGhostofOtto1923
2.5 / 5 (11) Mar 07, 2011
@ottogroupietroll
As I said, all the hard science anyway.
And as I implied, since you are unaware of the full extent of ottos knowledge of hard science facuities, your assertions are imprecise and... sloppy.

So- now- work with me here dick. If we could convert interstellar matter to ions by either hitting it with energy beams and /or causing it to impact a suitable shield of some sort, could this be something that a metamaterial of THE FUTURE could divert?
The failing to comprehend is your problem. I can't make it any clearer until you have at least a passing familiarity with rudimentary quantum mechanics
-I mean your knowledge base is so fucking haughty that you should be able to conceptivate this for even me, nicht wahr- er- n'est pas?

Even if science can create your accupierre suction plunger configuration for practical use, there will still be the need for sublight travel at speeds at which miniscule impactoids might still be a problem. Any suggestions?
ottogroupietroll
2.1 / 5 (7) Mar 07, 2011
Hey dick
"Recent experiments even confirm the relations for molecules and even macromolecules, which are normally considered too large to undergo quantum mechanical effects. In 1999, a research team in Vienna demonstrated diffraction for molecules as large as fullerenes. The researchers calculated a De Broglie wavelength of the most probable C60 velocity as 2.5 pm." WIKIPEDIA

-So perhaps you science sheikhs might some day devise a metamaterial which can diffract larger items, suitably prepared.
Remember your vector notation from high school physics
Naw man I failed physics.
Btw, everyone knows that people who refer to themselves in the third person are total failures at life. Fyi.
Naw man everyone knows that anyone like dick the wondersockpuppet who makes up ananymous sockpuppet armies to one-rate people just because they tell dick to go stick himself, are total failures in life. Ottos just a nick dood.
ottogroupietroll
2.1 / 5 (7) Mar 07, 2011
The bottom line: even "perfect" cloaking is going to involve a real trade-off between stealth and sensor capability, which is more or less exactly the dynamic we face now, as anybody who has ever tracked a submarine will readily admit.
-Or the new JSF:

"In spite of being smaller than the F-22, the F-35 has a larger radar cross section. It is said to be roughly equal to a metal golf ball rather than the F-22's metal marble."

-Sensors could be shuttered mechanically or electronically, or selected areas in the metamaterial could allow partial transmission as in a beam splitter.
jscroft
1 / 5 (4) Mar 07, 2011
Sensors could be shuttered mechanically or electronically, or selected areas in the metamaterial could allow partial transmission as in a beam splitter.


Yah, that's kind of my point. If your stealth strategy is to route light around yourself, then partial transmission = partial stealth. If you're going to leave sensors outside the envelope, then you're exposing yourself to exactly that degree... like the radar cross-section and visible rooster-tail thrown up by a sub's periscope.

I'm not sure the JSF example is relevant, though. Stealth aircraft aren't stealthy because they are "transparent" to radar, but because they are either ENTIRELY opaque to it (i.e. they absorb it) or because they reflect it in every direction but the one that matters. Usually a combination of both.

Cloaking devices like the ones under discussion here are useful when the stealthed object is BETWEEN the sensor and the illumination source. In THAT geometry, the JSF would stick out like a sore thumb.
jscroft
2.5 / 5 (8) Mar 07, 2011
Incidentally, I've lost track... am I addressing Otto-The-Jackass-Troll or Otto-The-Other-Jackass-Who-Won't-Quit-Poking-Him-With-A-Stick? :)
TheGhostofOtto1923
2.5 / 5 (11) Mar 07, 2011
Incidentally, I've lost track... am I addressing Otto-The-Jackass-Troll or Otto-The-Other-Jackass-Who-Won't-Quit-Poking-Him-With-A-Stick? :)
Otto is otto who is either neither or both. Hard to know when stumbling into the middle of a firefight, who is the good mensch and who is the bad little troll.

Otto is good and innocent as the driven snow. Dick_wolf the sockpuppet is apparently in love with me. Wonder what his primary nick is? Ryan? Heel dick.

Re the topic, I keep thinking of course of the Predator creature and his imperfect cloak. He might stick out on radar, unless their technology included more conventional stealth.
ottoisasciencegroupie
1 / 5 (3) Mar 08, 2011
If we could convert interstellar matter to ions by either hitting it with energy beams and /or causing it to impact a suitable shield of some sort, could this be something that a metamaterial of THE FUTURE could divert?


No. Ionization is irrelevant, mass and incident velocity are the problems here: space debris covers an enormous range of masses and speeds, and a metamaterial matter cloak can only be tuned to a single frequency. If the frequency of the incident particle differs from this by even a few percentage points, the particle begins to interact with the metamaterial, immediately damaging it. Now when you consider that the range of particle masses in space spans the spectrum from free electrons to metallic rocks of significant sizes, and all of these are moving at different velocities, you (should) quickly realize that metamaterials will never be useful as micrometeoroid shielding. But metric engineering offers the hope of a nonmaterial shield, which is what's needed.
ottoisasciencegroupie
1 / 5 (3) Mar 08, 2011
Even if science can create your accupierre suction plunger configuration for practical use, there will still be the need for sublight travel at speeds at which miniscule impactoids might still be a problem. Any suggestions?


Yes, try some reading on a subject before posting your questions about it.

The Alcubierre drive works by compressing spacetime in front of a craft, and expanding it behind the craft, and in-between there's a region of flat spacetime within which the craft remains at rest. It's like moving on a conveyor belt: regardless of the rate of motion observed from an exterior point of reference, the interior "bubble" remains motionless wrt the craft. So the craft doesn't move "through" spacetime at all. It's like the difference between swimming through a lake, and riding a raft down a river. By riding on a magic carpet of spacetime, the velocity of the craft relative to the particles in space remains the same as an astronaut on a spacewalk around the Earth.
ottoisasciencegroupie
1 / 5 (3) Mar 08, 2011
To sum up, the Alcubierre concept at least in concept clears all three of the key hurdles to manned interstellar spaceflight:

1.) there is no need for reaction propellant

2.) a traveler can move faster than the speed of light, and with no relativistic time dilation consequences, and

3.) the spacecraft can travel unimpeded by the bath of incoming space debris that would otherwise impact a craft with energies comparable to detonating thermonuclear warheads.
TheGhostofOtto1923
2.7 / 5 (12) Mar 08, 2011
a metamaterial matter cloak can only be tuned to a single frequency.
At present. Layered solar cells are being devised to respond to different wavelengths of light.
spans the spectrum from free electrons to metallic rocks of significant sizes, and all of these are moving at different velocities, you (should) quickly realize that metamaterials will never be useful as micrometeoroid shielding.
Perhaps not by themselves but as part of a system with multiple elements working in concert, not unlike current stealth technologies. Tunable or 'smart matter' metamaterials are not out of the question.

The main problem at present with your warp drive is that nobody has any idea of how to do it without a stars worth of energy to play with.

'Never' is also useless hyperbole.
jscroft
2.3 / 5 (6) Mar 08, 2011
I keep thinking of course of the Predator creature and his imperfect cloak. He might stick out on radar, unless their technology included more conventional stealth.


So was I. With the obvious caveat that YES, I know it's just a movie, I've often wondered about the rationale behind (or in front of, in our case) the visual effect.

Generally my assumption has been that the effect makes sense, as no stealthing system thus far invented provides perfect coverage. But after this conversation, it's plain to me that imperfect stealth is a NECESSARY consequence of having to sense and interact with a complex environment. So maybe the "Predator effect" is an example of what this trade-off might look like when realized in hardware.

As a practical matter, faster or more complex relative motion will require a higher sensing frequency and thus more visibility. So expect man-scale invisibility cloaks to be of more use to snipers and recon forces than, say, mobile infantry.
jscroft
2.3 / 5 (6) Mar 08, 2011
It also makes sense that, if you're firing a non-autonomous weapon (like a rifle), the critical instants prior to firing are going to require nearly continuous sensing. So what we have is a sniper who fades into visibility as he takes aim, with maximum exposure at the moment he takes the shot, followed by a dim afterimage as he conducts his damage assessment and possibly prepares for another shot.

Spooky!
TheGhostofOtto1923
2.8 / 5 (9) Mar 08, 2011
Roddenberry already concepted it, the Romulans achilles heel:

http
://www.youtube.com/watch?v=gogyd66PFyE&feature=fvwrel

The military is already considering active camo which may produce a Predator effect:
http
://en.wikipedia.org/wiki/Active_camouflage
Pyle
1 / 5 (1) Mar 08, 2011
Let's set the record straight. Otto is only reliable for inflammatory rhetoric, not serious scientific ponderings. We, well I, love him for it. Anti-Otto (or whatever his preferred nick is) is only good for poking Otto. But again, this isn't bad. At least Otto seems to enjoy it.

Finally the Alcubierre effect is a mathematical game with GR that doesn't even play by the rules. So the "traveler" on your magic space-time carpet ride feels no effects of travel. What happens in the warped space around your bubble, at what energy cost? What proposed methods of warping space-time are there even? Oh yeah, none. At least the metamaterial shielding is 'impossible' for real physical reasons. Your Alcubierre drive is just fantasy. Keep poking though!
Pyle
5 / 5 (2) Mar 09, 2011
@jscroft: I admire your attempts to bring the conversation back from Otto bashing. Ultimately only the "periscope" need be uncloaked to survey the surroundings. A pinhole to view the world through could, conceivably, be the only part of your sniper visible immediately prior to the shot, assuming the technology is perfect.
jscroft
1 / 5 (4) Mar 09, 2011
@Pyle: Haha screw Otto. This is interesting!

Good point re. the "periscope," although that's going to have a different meaning in different contexts. A sniper's weapon IS the platform that collimates its pointy end--the projectile--with his sensor array. You're either going to have to "un-cloak" a significant chunk of his weapon, or else completely redesign the thing. That's going to be a challenge, because many of the design constraints on a sniper's weapon (like portability, ruggedness, etc.) have little to do with actually firing the thing from a concealed position.

Anyway, the point still stands: there HAS to be a trade-off between cloaking efficiency and navigation/targeting efficiency. Technology can drive the balance toward some ideal, but progress will NECESSARILY be asymptotic, a la Heisenberg.

It's the nature of the beast. At least, it's the nature of THIS beast.
Pyle
3.7 / 5 (3) Mar 09, 2011
@jscroft:
@Pyle: Haha screw Otto. This is interesting!
Actually I fall on "the otto's" side of many arguments. (I don't buy his 5,000 year conspiracy theory, but that aside.) This one doesn't qualify as an argument to me, he's was just shown up by the lurker.
Regarding the sensory array, why a significant chunk of the weapon? The projectile can leave the cloak no problem. You just need to know where to point the cloaked weapon and a pinhole is sufficient to gather the information, receive instructions, etc. The trade-off doesn't present itself until you have a cloaked target and you need a broader sensory receiving surface. For "everyday" applications there are soooooo many photons bouncing around that all you need is an itty bitty periscope.
jscroft
1.8 / 5 (5) Mar 09, 2011
Hmm, ever fired a rifle, Pyle?

The separation between the front & rear sights is what gives the marksman the angular precision necessary to put a dime-sized round into a head-sized target a mile away. The mechanical coupling between the sights and the barrel provide the collimation that ensures a match between sight picture and shot placement. The bottom line: unless sufficient light travels up the full length of the barrel, there won't be a shot.
jscroft
1.8 / 5 (5) Mar 09, 2011
I know that doesn't sound like much, and in fact modern snipers routinely fire from within an envelope of camouflaged netting that provides more or less the kind of concealment we're talking about... but then you'll find that more than a few ENEMY snipers wind up taking a round right through the right eye after it has passed up the length of their sniper scopes. I said a SIGNIFICANT chunk of the weapon, not a BIG one.

Could you decouple the sights from the barrel and achieve collimation in some other way? Sure... by completely redesigning the weapon. But that was my point.
Arf_Arf_Arf_Arf_Arf_Arf
2.1 / 5 (7) Mar 09, 2011
Actually I fall on "the otto's" side of many arguments. (I don't buy his 5,000 year conspiracy theory, but that aside.)
Please to look up the words myopic and intractable on GOOGLE. Danke.
SincerelyTwo
1 / 5 (3) Apr 02, 2011
Also, while they are a part of the fictional universe I don't recall any of the other type of invisibility cloaks ever being depicted in the books or the movies.


Romulan space ships?


I established the context in which I was speaking, the Harry Potter universe. I don't know who marked me as 1/5 but it better not have been for that reason. Anyone else here familiar with logic?

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