Knife with Sapphire Blade! (no metal)

jill jackson said:
I've flown many times since 9/11 and they only XRAYED my carry on and made me walk through a metal detector. I could have had any sort of non metal weapon taped to my body and they would have never known it. :eek:
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i think that will change in the near future.
 
M Wadel said:
i guess these machines can see through anything, since they are more advanced than regular x-ray-machines. i wouldnt worry about ceramic knives when i fly, i would worry alot more about stolen missiles, bombs and such, however not even that is likely to happen imo. a ceramic knife would probably snap very quick if you stabbed someone, so its onetime weapon, useless imo. no need to worry there.
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It would never dull when cutting throats, even if it was not so strong as metal. :eek:
 
anybody seen the movie "total recall" with the Arnold the govenator, in that movie they have one of those machines.. thats how they look :)
 
So this knife being sapphire is probably pretty expensive and rare.

Does that make it a "Terrorist/Gent jet knife" ?
 
killerskill said:
Listen to that cry baby wussy sheeple who wrote that article. Those people make me sick:barf: ''Oh no, the ''terrorists'' are gonna get us all with saphire knives"":jerkit:
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I am pretty sure that the author was being sarcastic in his little article. He was pointing out the futility of what the airlines are trying to do to stop "terrorists".
 
BTW, I don't think X-rays will be able to detect a sapphire blade. Sapphire is transparent precisely because it transmits electromagnetic waves without reflecting or absorbing them.
 
IMO obsidian would make a sharper non-metal blade. I've seen arrowheads made from it and they are very sharp.
 
A bad choice. Even if single crystal and absent any significant inhomogeneities, sapphire is rather heavy and quite brittle. True, the edge would be extremely sharp -- briefly. (And it's tough to grow large pieces of single crystal sapphire -- whether you use heat-exchanger methods or EDFG, Edge-Defined Film-Fed Growth.)

Good as a scalpel, perhaps, but that is it. One good blow perpendicular to the axis and you'd have a great deal of very sharp sapphire shards.

Now -- as an optical material, quite useful! And with interesting non-linear optical and EM properties.

BTW, I did a great deal of work with artificial sapphire in the early 90s.
 
Artfully Martial said:
It doesn't matter how deadly a weapon is on an airplane. It just has to scare people, since apparently in virtually all instances in 9/11, no one resisted...a guy with a box cutter wouldn't stand a chance against the huge numbers on a commercial jet, and people probably wouldn't even get killed resisting (a real possibility, of course, but a box cutter just can't penetrate that far"

That is not true. Read about what happened on Flight 93, that's the one that flew into the ground after the passengers ran at the terrorists and fought with them. The intended target was the Capitol building.

Early in the hijacking the terrorists killed two men by slitting their throats with a box cutter.

I urge anyone who has forgotten the Flight 93 story to read this...

http://www.post-gazette.com/headlines/20011028flt93mainstoryp7.asp

Steve
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I specifically said most. People are arguing technicalities. My point is that the weapons terrorists used were never designed to kill in the first place, merely to intimidate. Now, if they had a realllllly deadly weapon that for some reason didn't look at all like a weapon, it would have been ineffective from the get go. The purpose is almost entirely psychological.

In regards to the x-ray visibility of the knife, I'm betting you could see it pretty well. As a general rule, the denser the stuff, the more x-ray visible. If something is small but weighs 20 lbs, you'll almost definitely see it...there are some other physics concepts going into x-ray visibility too, but this is the most obvious one. High Z numbers of the atoms involved (which is closely related to the first part) is also really obvious on x-rays.

Some folks have referred to its ability to be seen through a deterrent for x-rays. But x-ray machines don't work like your eyes. They're effectively shining a big x-ray flashlight through one side and your eye is on the other side..like putting a flashlight up to the back of your hand and seeing the bones through the palm like I did as a kid. You see where x-rays don't go through, or got through less often.
 
The plain and simple fact everyone from this post to the authorities are ignoring is that a plane could never be taken at knife point again. The terrorsists operated on the correct assumption that the hostages felt they were bieng taken into a hostage negotiation situation. Had they known that they would be used as a airborn missle they would have happily sacraficed another passanger or two to overtake there opponents. As it was they had just watched someone die bloodily and didnt want to risk there own or other passengers lives. While of course this is speculation, ask yourself one question. Knowing what you know now, would you let your family be taken hostage on a plane by a guy with a straight razor? Or would you glady risk life and limb to stop the situation and save not only those on the plane but thousands of inncoents ina building somewhere? 9/11 was a new tactic that took people by suprise. I personaly think it would be fine to return to allowing passengers to cary small posket knives again, although I know this will not happen. I think explosives and guns are the only real threat in air travel at this point.
 
OldPhysics,

The crystal on my watch face is sapphire, and has sustained some reasonably sharp impacts.

Is it that the impacts on a knife edge are so much greater per unit volume(?)/surface area(?) or that I just haven't whacked it hard enough yet to discover sapphire's brittleness?
 
The Swiss watch-makers have been well aware of sapphire's limitations for a very long time. It is nonethless a nice compromise -- transparent, today relatively cheap to produce, and extremely tough (though brittle).

The watch crystals are pretty thick and are carefully shaped to be self-supporting. Most 'whacks' will be resisted successfully -- you won't even see a tiny fracture (usually begins as a small star shape) -- especially if a blunt object is responsible for the whack. Now, the same force used in a smaller area can reach sapphire's breaking point and produce a fracture, thus ruining the watch face.

More importantly to the watch-makers, little bits of grit are generally not 'hard' enough to scratch the surface of the sapphire. Pulling the smooth sapphire crystal (carefully worked to remove any imperfections) across even sharp metal surfaces generally will not result in a scratch. Like all non-ductile materials, sapphire is strongest when it presents either a perfect bulk material or a smooth surface with no imperfections (no place to start a propagating crack!).

I would not put the face of a punch, for example, on a sapphire watch crystal...and strike it with even a small hammer!

You are correct when you suppose that a thin, sharp knife edge made of sapphire is thus extremely vulnerable. Any impact is delivered automatically against a very small area, rapidly leading to chips and fractures and thence to total failure.
 
DocNightfall said:
But if I put myself in a terrorist's shoes, I would think it'd make a really nice airplane knife. Who cares if it isn't that tough? It's sharp, and that's all I'll need it to be. Box cutters (which are similarly sharp and not so durable) were used to hijack the planes used in the 9/11 attacks, so airport officials are now more careful watching out for box-cutter-like devices on X-ray scans of hand-carry luggage.
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Pardon my bumping this, but what public evidence is there that box cutters were used?

I have seen none; on the contrary I recall seeing at least one article pointing out the lack of evidence.
 
It is not out of the question guy's. Boker makes ceramic blades. Even though
I am not a big fan of them. Because if you happen to drop the blade, it will
shatter and also the price is steep on them.
 
DocNightfall said:
The best way to prevent that scenario from happening to you, is of course to bring your own sapphire-bladed pointy. If enough passengers have them, those terrorists don't stand a chance!
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You are reminding me of a comedian years ago (before 9-11) who said she always brings a bomb with her on the plane. Because after all, what are the chances of their being TWO bombs on the plane?
 
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