cloaking devices??

Scott:
>A few days back, Steve and Hans mentioned the idea of using the
>Active EMS or EMS Jammers as a cloaking device.  Well, sorry to get
>back to it so late, but I just thought you might wanna know that this
>is (of course) impossible.

Hmmm... then why is GM talking about using it on cars in 1994?


>The hope would be that you could emmit an electro magnetic wave
>pattern identical to the ships normal pattern but out of phase with
>it in such a manner as to create a destructive interferance pattern.
>Well, that is I'm afraid, just not possible.

I also seem to recall seeing a news article on test operations in use
today.  It didn't work real well with anything but low frequency
stuff, but it did work.


>There is an analogous short story by Arthur C. Clarke called
>"Silence, Please."  Which appears in "Tales From the White Hart"
>(Excellent stuff).  The idea there is not EM radiation, but sound
>waves.  (Much easier to deal with.) So, let's look at the problems
with that.

Yes, I've read it.  Written in the late 40s-early 50s, right?  Before
computers?


>In order to create such an interferance pattern, one would have to
>know, the exact position of the listener (to within a wavelength of
>the sound in question) as well as how they were moving to take
>doppler shift into account.  Now you might be able to do that for ONE
>observer, but if the observer moved, even slightly, the effect would
>be lost.

No.  If it out of phase here, it will still be so there, assuming that
the signal is an exact copy of the incoming.  And if you match the
wavelength incident where you are, the doppler shift will shift it
right along with the original signal you are trying to mask.


>I believe in some airliner designs they were talking about using
>speakers in the cabin to make zones of destuctive interferance around
>passengers heads to drown out the sound of the aircrafts engines
>(Unducted fans.)  The system was going to block out just the sound of
>the engines.  However the silence zones were only localized to the
>region of the passengers head.  There were speakers placed in the
>chairs headrest.  But it was not possible to get the entire fusilage
>of the plane to be such a zone.

I hadn't heard of that one.  Sounds like a start in the right
direction, and I don't believe that 3000 years additional research
won't be able to come up with a better result.


>Now, to attempt this with light, you might be able to fool one
>observer, BUT you would have to know their EXACT position.  To within
>a wavelength of light, ie down to nanometer acurracy.  You would have
>to know their EXACT speed relative to you to account for doppler
>shift.  Now, with the ranges of space combat being what they are,
>there is NO way you could know this.  And if you did, you might as
>well fire your weapons, cause your sensor accuracy would have to be
>enough to count every cell in the pilot's body.

Nonsense.  Are you suggesting that I have to know your exact position
for you to SEE me?  If you can see me, then I can flash a light in
your eyes.  And if the light were just so, then you wouldn't see me
any more.  If you assume (and you have so far) that the sensor arrays
are all over the hull, then you could get a pretty good copy by
generating a counter-signal at each point on the array to match
incident EM at that point.  It won't be perfect, by any means (unless
technology improves in 3500 years - a long shot, some people think),
but it will be better than letting them see you without even trying to
hide.


>Furthermore, even if you did manage to fool their passive EMS like
>this, you would still run afoul of their densiometers and neutrino
>sensors.  And there is no way to spoof a neutrino sensor.  If you
>built a decoy drone to spoof it you would have to install a similar
>size power plant in order to get it to fool anyone.  (Several million
credits for a decoy drone?)  Nope.

I never said we could spoof their densitometers and neutrino sensors.
But Rob Dean pointed out recently (from TD #3?) that the operational
parameters for a densitometer were envisioned such that detection
range would be less than 5000Km.  And you can monkey with neutrino
sensors by EMMasking your ship, but not your drone, or by using a
reaction that produces more neutrinos in the drone...


>Yes, we have no cloaking devices.
>We have no cloaking devices today.  :-)

But will we in 3500+ years?  THAT is the question!

And I never suggested a cloaking device.  Hans inferred that.  I was
suggesting something to make you ship HARDER to detect, not
impossible.

Later...

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I have learned to use the word "impossible" with the greatest caution.
                                    --W. von Braun