Can Stealth Technology Work With Light Waves?
Ptolomy
Brian Trosko <btr...@primenet.com> wrote:
>So, how would you do this with light waves? Pretty much anything you do
>along the same lines will still result in a target that's totally visible
>to a Mk. 1 Eyeball. Painting it black works just fine for night, which is
>why stealth aircraft *are* black. But during the day, it'll still stand
>out quite nicely. The other thing that stealth does, reflection, also
>wouldn't work to well. Cover your plane in mirrors? I'll still see it
>just fine.
>Sure, you could magically render it transparent or something, but that's
>not what stealth does. No, Stealth technology wouldn't work with visible
>light. I'll accept that something could, but it wouldn't be accurate to
>refer to this hypothetical something as 'Stealth'.
One might want to consult the history books for this one. It seems to
me that I remember reading years ago about a govn't project around
WWII or shortly thereafter called the Philadelphia Experiment? The
basic concept of the project was to use electromagnetic energy to
actually bend light around objects - buildings, ships, aircraft, etc.
This would render the subject effectively invisible to the eyes as
well as to any method of electromagnetic detection, i.e. radar. In
principle, this would be quite plausible. I believe this is where G.
Roddenberry came up with the idea for the cloaking devices for Star
Trek. As I recall various experiments were conducted; however, I
think we may all assume that none too successfully. If one could
perfect such a system, I would have to say that it would fit the
criteria for the description of being a genuine 'stealth' technology!
Regards, JCD.
P.S. Any further info on this subject would be concidered interesting
and post-worthy :)
Erik Max Francis
Ptolomy wrote:
> One might want to consult the history books for this one. It seems to
> me that I remember reading years ago about a govn't project around
> WWII or shortly thereafter called the Philadelphia Experiment?
The Philadelphia Experiment is (not even particularly good) science
fiction, folks.
--
Erik Max Francis, &tSftDotIotE / email: m...@alcyone.com
Alcyone Systems / web: http://www.alcyone.com/max/
San Jose, California, United States / icbm: 37 20 07 N 121 53 38 W
\
"E pur, / sic muove!"
/ Galileo Galilei
Paul J. Ready
Richard A. Schumacher <schu...@rsn.hp.com> wrote:
>>At any rate, that statement underestimates the AF, they would paint
>>a plane any color they thought would keep it from being shot down,
>>it's just that the primary stealth mission is flying at night. If
>>that changes, expect to see F-15/22 paint colors on the birds for day ops.
>Buckley reports that "Have Blue" F-117 prototypes were light
>blue and inconspicuous against daytime sky. Production aircraft
>are black. Apparently non-functional concerns (aesthetics?
>machismo? image?) do matter in today's Air Force.
I'm sorry, but I don't see your point here. Light blue to grey
does blend against the daytime sky, but black is the color to
avoid searchlights and fly low at night. Have Blue was a test
program, and any test program is going to start out with 100%
day flights, the -117 flew (almost?) exclusively at night during
desert storm, when blue would be less stealthy. In addition,
black has thermal properties that are supposed to be more stealthy in IR.
If the AF didn't like blue, they wouldn't paint their fighters blue.
Brian Trosko
Ptolomy <euc...@juno.com> wrote:
: One might want to consult the history books for this one. It seems to
: me that I remember reading years ago about a govn't project around
: WWII or shortly thereafter called the Philadelphia Experiment?
You'd probably want to consult the history books on that one, because it's
complete bunk. Fortunately, you did post on April 1st.
Allen Thomson
In article <Pine.A41.3.95.970401...@green.weeg.uiowa.edu> "P. Wezeman" <pwez...@blue.weeg.uiowa.edu> writes:
[much snippage]
> "Wings" showed some footage of an Avenger torpedo bomber with such
>lights along the front of the wing and inside the engine cowling. These
>were called Yehudi lights, named for the fictional little man who
>wasn't there.
To depart from the topic, thread and charter, can anyone explain in more
detail the Yehudi story/rhyme? I've heard it for decades, assumed from
the name that it's of Jewish folk origin, but have never heard the complete
explanation.
TIA
au...@imap2.asu.edu
Based on the title of the thread, I can't help but wonder if the
original poster might be wondering about the vulnerability of a "Stealth"
type aircraft to some type of terahertz system, or perhaps more
straightforwardly a LIDAR. "light" and "laser" often get mixed up in
general usage.
The primary answer: It doesn't really matter. LIDAR in most
applications is (and will increasingly be) used to detect not the
aircraft itself, but rather its environmental impact. No, not EPA
paperwork, but rather the air turbulence it creates and the pollution
(exhaust) it leaves behind. "Stealthy" or not, it is kind of hard to fly
without displacing air, and also rather hard to fly fast without using
combustion.
regards,
---------------------------------------------------------------------------
Steven j Forsberg at au...@imap2.asu.edu Wizard 87-01
Frank Crary
In article <3341DEFB...@alcyone.com>,
Erik Max Francis <m...@alcyone.com> wrote:
>> One might want to consult the history books for this one. It seems to
>> me that I remember reading years ago about a govn't project around
>> WWII or shortly thereafter called the Philadelphia Experiment?
>The Philadelphia Experiment is (not even particularly good) science
>fiction, folks.
Are you sure? I'd assumed that the Philadelphia Experiment was
some old, black project that a science fiction writer uses as a
name for a fictional program, just because it was a real program of
some sort and he liked the sound of the name.
> Erik Max Francis, &tSftDotIotE / email: m...@alcyone.com
> Alcyone Systems / web: http://www.alcyone.com/max/
>San Jose, California, United States / icbm: 37 20 07 N 121 53 38 W
> \
> "E pur, / sic muove!"
> / Galileo Galilei
Which is just a popular myth: Galileo would have been insane to say
anything of the sort, and there is no evidence that he actually
said the. (Although some of Galileo's actions during his inquisition
were fairly stupid, and might be considered insane, they weren't on
par with contradicting a confession he had just made. He was quite
familiar with the case of Bruno, and knew that stating his actual
opinions after promising the be a good boy was a excellent way to get
burned at the stake.)
Frank Crary
CU Boulder
Edward Wright
Here's an interesting item with implications for launch-vehicle design.
Boeing recently obtained a sample of a metal called gamma aluminum
titanimide, which the US government apparently spent hundreds of millions
of dollars trying to develop, unsuccessfully, as part of the NASP program.
According to Dana Andrews, you can now build a space-vehicle structure out
of this material and leave off the TPS. It is now being offered for sale
by a commercial mill in Austria.
--
The opinions expressed in this message are my own personal views
and do not reflect the official views of Microsoft Corporation.
Frank Johnson
Edward Wright wrote:
:
: Here's an interesting item with implications for launch-vehicle
design.
:
: Boeing recently obtained a sample of a metal called gamma aluminum
: titanimide, which the US government apparently spent hundreds of
millions
: of dollars trying to develop, unsuccessfully, as part of the NASP
program.
The problem with gamma-TiAl is that, like many intermetallics, it's
very brittle. In fact, if you were to drop a piece of of off a table it
would
shatter when it hit the floor.
: According to Dana Andrews, you can now build a space-vehicle structure
out
: of this material and leave off the TPS. It is now being offered for
sale
: by a commercial mill in Austria.
The X-30 was actually more seriously looking at alpha-TiAl that was
reinforced with SiC fibers. They (Rockwell, I think) managed to get a
reasonable fatigue
properties out of such a composite, but it failed thermal cycling to due
oxidation at the fiber/matrix interface. The program settled on using
conventional
Ti6Al4V-SiC composites and got around the lower melting point by
selective use
of a refractory TPS.
As an interesting side note the automotive industry was looking at
using
gamma-TiAl for piston heads in internal combustion engines. This got
people excited
because of a potential market for hundreds a thousands of lbs of
material. But I don't
think this ever got any farther than as a concept.
:
: --
: The opinions expressed in this message are my own personal views
: and do not reflect the official views of Microsoft Corporation.
Later,
-Frank
Allen Thomson
In article <5i4eeu$o...@news.microsoft.com> edwr...@microsoft.com (Edward Wright) writes:
>
>Here's an interesting item with implications for launch-vehicle design.
>
>Boeing recently obtained a sample of a metal called gamma aluminum
>titanimide, which the US government apparently spent hundreds of millions
>of dollars trying to develop, unsuccessfully, as part of the NASP program.
>of this material and leave off the TPS. It is now being offered for sale
>by a commercial mill in Austria.
Ah, AlTi resurfaces! While I have no clue as to the actual history
of work on this material or anything connected with it, I did hear
an urban legend/potential X-Files episode involving it. Here it is,
for whatever entertainment value it may have.
Two or three decades ago, an Eminent Metallurgist at, IIRC,
UPenn was contacted by Certain Government Officials, who gave him
samples of AlTi. As you can guess, these samples possessed material
properties far beyond anything then available. The UL is unspecific
as to whether the samples came from stolen Soviet technology, crashed
flying saucers, unrepeatable secret experiments, Faery rings, or
whatever.
The very slightly interesting part of this fable is that the
metallurgist was well known, at a specific Pennsylvania university,
and passed pieces of the samples to colleagues who analyzed them and
published the results in appropriate journals. This would appear
to be checkable (though not by me: I'm nothing like a metallurgist,
and am not sufficiently interested to figure out where to look and
what to look for).
Azeez Hayne
In article <33440037...@news.dial.pipex.com>, be...@dial.pipex.com wrote:
> Brian Trosko <btr...@primenet.com> wrote:
>
> >detect the F-117 until it's only 2 miles away, by which time it's already
> >opened the doors, dropped the bombs, and closed the doors again. By which
>
> I heard somewhere that one of the features of the F117 is it can open
> its doors, drop its load and close them again in a short space of
> time, to minimise its radar signature while they are open. Well I was
> just wondering why couldnt they just fit doors that open inwards?
> Shouldnt really affect the stealthyness and there wont be a big mass
> penalty?
>
> ---
> Robbie Longworth
> Preston UK
Ah...how would you avoid hitting the ordinance sitting in the bay? Unless
you wanted very tiny doors or a shitload of space between the doors and
the bombs...
Azeez
"Trix are for kids, Lucky Charms are for your MOM!"
-me
"The reason the movements of 60's and 70's seem so radical is that the 50's were so dead..."
-J
"What we obtain too cheap, we esteem too lightly...it would be strange indeed if so celestial an article as FREEDOM should not be highly rated."
Brian Trosko
Robbie Longworth <be...@dial.pipex.com> wrote:
: time, to minimise its radar signature while they are open. Well I was
: just wondering why couldnt they just fit doors that open inwards?
Either way, you're dealing with a *huge* increase in RCS, unless you want
to specially design both the interior of the bays and the bombs your
dropping. Doing to former adds expense and weight. Doing the latter
isn't really feasible.
: Shouldnt really affect the stealthyness and there wont be a big mass
: penalty?
If the doors open inward, you've got to make the bays bigger to accomodate
their movement, or carry less ordnance. Neither's a good thing, since the
-117 has a small enough bombload already. And, again, opening the doors
inward doesn't give you a smaller RCS than opening them outward.
Paul F. Dietz
On 5 Apr 1997 02:46:54 GMT, edwr...@microsoft.com (Edward Wright)
wrote:
>
>Here's an interesting item with implications for launch-vehicle design.
>
>Boeing recently obtained a sample of a metal called gamma aluminum
>titanimide, which the US government apparently spent hundreds of millions
>of dollars trying to develop, unsuccessfully, as part of the NASP program.
You are refering, I believe, to gamma titanium aluminide, an
intermetallic phase with the formula TiAl. I understand it has been
of interest for some time, but has had problem due to low ductility
(a problem with many intermetallic compounds). It is being actively
investigated for use in combustion turbines and valves in internal
combustion engines.
There are numerous references on the web to gamma TiAl. See, for
example:
http://ai-www.aist-nara.ac.jp/doc/people/eiiti-o/Pro/000038.html
http://hotrod.mt.ic.ac.uk/lchristo/creep.html
http://www.tms.org/Meetings/Annual-96/ThursAM1.html
http://www.tms.org/Meetings/Annual-96/ThursAM2.html
http://www.tms.org/pubs/Books/EachBook/304X.html
(+ many others)
Paul
Support Engineer
Dumb question, but would a metal glass of this alloy avoid the friability
and still have the heat resistance?
Support Engineer
Edward Wright <edwr...@microsoft.com> wrote in article
<5i4eeu$o...@news.microsoft.com>...
> of dollars trying to develop, unsuccessfully,
>It is now being offered for sale
> by a commercial mill in Austria.
Is there not a conflict between these two statements?
Jesse Nadel
Mark Eaton wrote:
>
> In article <33440037...@news.dial.pipex.com>, be...@dial.pipex.com wrote:
>
> > Brian Trosko <btr...@primenet.com> wrote:
> >
> > >detect the F-117 until it's only 2 miles away, by which time it's already
> > >opened the doors, dropped the bombs, and closed the doors again. By which
> >
> > I heard somewhere that one of the features of the F117 is it can open
> > its doors, drop its load and close them again in a short space of
> > just wondering why couldnt they just fit doors that open inwards?
> > penalty?
> >
>
> doors open inwards or outwards is irrelevant. The opening itself is what
> causes the problem. Something about sharp angles. The surface of the craft
> is designed so that wherever theres an edge, the two surfaces meet at
> shallow angles. The opening would violate this.
>
> But I'm just guessing based on popularizations of the subject.
>
> -Mark
>
> --->
> markeaton_@_mindspring_._com
Mark's right about the opening itself being a problem. In addition,
though, combat aircraft these days are so tightly packed that the bomb
bay is so small that there is no room internally for the door to open
without hitting the bomb. Externally opening doors are the only
feasible arrangement.
Jesse
Brian Trosko
Ralph Reinhold <Ralph.R...@hsv.boeing.com> wrote:
: The sky is black at high altitudes
At *very* high altitudes, like where the SR-71 can get up to when it tries
hard on a good day. Neither B-52s or F117s or B2s go anywhere near that
high.
:, this is why the bottom of B52s were
: black
I've never seen any B-52s with black bottoms.
: and it probably is why the F-117 and B-2 are black.
Are you trolling? Those planes are black so they're hard to see when they
fly at night, which is the only time they'll actually fly combat missions.
Spectre
Brian Trosko wrote:
David Palmer <dmpa...@clark.net.nospam> wrote:
: I have heard of stealth planes being successfully detected by
radar looking
: downwards, and seeing a hole in the scatter from the ground.
There's all sorts of radar that can detect stealth.
Everyone here seems to be laboring under some misapprehension that
stealth
is some magic turn-the-plane-invisible technology. It's not.
Stealth
just makes detection *harder*, not impossible. The idea is that if
your
SAM radar can detect, acquire, and track an F-15 at 80 miles, it
won't
detect the F-117 until it's only 2 miles away, by which time it's
already
opened the doors, dropped the bombs, and closed the doors again. By
which
time it doesn't matter if you can acquire or track the guy, since a
pair
of 2,000lb LGBs are already halfway to your emitter array.
Stealth defeats radar in two ways. For very short wavelengths,
Radar-Absorbing Material actually sucks up the radiation, converting
it to
heat. For longer stuff, the angled surfaces reflect *most* of the
radiation away from the receiving antenna. Note that 'most'; get
close
enough, the the other guy's *still* going to get enough of a return
off
of you. Maybe not enough to guide a missile with, but he's
definitely
going to know you're there. And if he emits with enough power, he
*will*
be able to track you.
But the reflection stuff only works if the wavelength of the
incoming
radiation is shorter (roughly) than the surface that's trying to
reflect
it. Long-wave radars can detect stealth aircraft relatively easily,
sometimes from quite long ranges. And no, this isn't a nail in the
Nighthawk's coffin, because long-wave radars have abysmal
resolution.
Yes, they'll let you know somebody's knocking, but you'll only know
where
he is to within a few dozen miles.
First, the radar has to detect the incoming aircraft. Stealth
knocks that
capability *way* back.
Second, the radar has to actually *track* the incoming aircraft. It
it
can't do that, then they can't launch radar-guided missiles at the
thing.
This is the kind of radar stealth was designed to defeat, so an
overhead
look-down radar certainly stands a better chance of detection or
tracking.
Third, once you launch the missile, either you or the missile has to
*maintain* the tracking, and stealth makes that much harder as well.
Stealth also mixes cooler air in with the exhaust, or otherwise
disperses
it to reduce (greatly) the IR signature. I'm not sure how it would
fare
against a modern, all-aspect IR missile, like a 9L, but it should
defeat
older-generation ones quite effectively.
So, how would you do this with light waves? Pretty much anything
you do
along the same lines will still result in a target that's totally
visible
to a Mk. 1 Eyeball. Painting it black works just fine for night,
which is
why stealth aircraft *are* black. But during the day, it'll still
stand
out quite nicely. The other thing that stealth does, reflection,
also
wouldn't work to well. Cover your plane in mirrors? I'll still see
it
just fine.
Sure, you could magically render it transparent or something, but
that's
not what stealth does. No, Stealth technology wouldn't work with
visible
light. I'll accept that something could, but it wouldn't be
accurate to
refer to this hypothetical something as 'Stealth'.
Check out the latest issue of Popular Science. They discuss the topic
of daytime stealth
Mikael Johannesen
>I heard somewhere that one of the features of the F117 is it can open
>its doors, drop its load and close them again in a short space of
>time, to minimise its radar signature while they are open. Well I was
>just wondering why couldnt they just fit doors that open inwards?
>Shouldnt really affect the stealthyness and there wont be a big mass
>penalty?
>
>---
>Robbie Longworth
>Preston UK
I don't think that it has the space to do that. The bombbay is loaded
with a rather big bomb.
David Burtner
In article <33440037...@news.dial.pipex.com>, be...@dial.pipex.com wrote:
|>
|> > Brian Trosko <btr...@primenet.com> wrote:
|> >
|> > >detect the F-117 until it's only 2 miles away, by which time it's already
|> > >opened the doors, dropped the bombs, and closed the doors again. By which
|> >
|> > I heard somewhere that one of the features of the F117 is it can open
|> > its doors, drop its load and close them again in a short space of
|> > time, to minimise its radar signature while they are open. Well I was
|> > just wondering why couldnt they just fit doors that open inwards?
|> > Shouldnt really affect the stealthyness and there wont be a big mass
|> > penalty?
The doors open outward for the same reason that closet doors open outward.
If the doors open inward, where do you put the bombs?
Patrik 'Ozzy' Olsson
-snip -
>I heard somewhere that one of the features of the F117 is it can open
>its doors, drop its load and close them again in a short space of
>time, to minimise its radar signature while they are open. Well I was
>just wondering why couldnt they just fit doors that open inwards?
>Shouldnt really affect the stealthyness and there wont be a big mass
>penalty?
-snip-
It would affect the "stealthyness", you are basically taking away
"lid" to a box full of edges and protrusions + the edges around the
bomb bay, all things that reflect radar all too well. You would also
have to have more complex bomb bay doors (which would take longer to
open) and most importantly, you will have a LOT of empty space that
you cannot use for anything due to the envelope of the the bomb bay
doors if they were to open inwards and not be allowed to come on the
outside of the plane at all.
In this case it is far better to have doors that open quick outward
and which allow a far better packaging of the planes interior!
You will ge a weight penalty also for having doors that open inward,
since you have to basically build a bigger plane due to the poor
packaging of the bombbay and the lids and opening mechanism would be
heavier as well than a smaller outwardly opening doors.
Best Regards
Patrik 'Ozzy' Olsson
Best Regards
Patrik 'Ozzy' Olsson
Jack Tabaska
Jesse Nadel <jesse...@lmtas.lmco.com> writes:
>Mark's right about the opening itself being a problem. In addition,
>though, combat aircraft these days are so tightly packed that the bomb
>bay is so small that there is no room internally for the door to open
>without hitting the bomb. Externally opening doors are the only
>feasible arrangement.
Just playing the devil's advocate here, but *conceivably* you could have
a sliding bomb bay door, like on the XB-70, or a rotating bomb bay, like
on the Canberra. However, you're still opening up a reflective hole in
the fuselage, so any gain in stealthiness would still probably not be worth
the increased cost/complexity/weight of the thing.
Jack Tabaska
jtab...@ural.colorado.edu
pat
In article <01bc442c$773764a0$1978...@mercury.inlink.com>, con...@inlink.com
says...
what a DoD lab was uable to do, a commercial facility was able to do
in commercial quantities. no conflict at all.
Funny, i worked on projects for the military that were failures while
within a few years, industry had produced far better products.
Charles Buckley
In article <E8C37...@news.boeing.com>,
Ralph Reinhold <Ralph.R...@hsv.boeing.com> wrote:
>Daniel Pawtowski wrote:
>>
>> In article <5hf3tm$f...@valencia.rsn.hp.com>,>> >will still obscure the background. (Rumor has it that the underside of
>> >the F-117A was to be painted light blue, to be less conspicuous against
>> >the background sky for ground observers, but the Air Force didn't like
>> >pastel colors.)
>>
>> I'd doubt that bit. I've certainly seen plenty of regular F-15's and
>> 16's painted pastel blue.
>>
>> Daniel Pawtowski
>> dpaw...@vt.edu
>The sky is black at high altitudes, this is why the bottom of B52s were
>black and it probably is why the F-117 and B-2 are black.
>Ralph
>
Nope. F-117 is intended, and has always been intended, to be a low level aircraft.
The prototypes for the vehicle were painted in a mottled blue coloring
and were considered very hard to see. The shift to black came later and,
so far, the rationale has not been sufficient to explain the changes. The
previous color scheme had tested out very well. Better, in fact, as they were
better equipped to work in the daytime.
(Actually, from the visual range, one of the most stealthy vehicles out there
is the Goodyear blimps. Without the lighting and painted signes, the thing is
very hard to see).
Jim Davidson
Support Engineer wrote:
>
> Dumb question, but would a metal glass of this alloy avoid the friability
> and still have the heat resistance?
Nice material, if you can get it.
Free Yourself,
Jim Davidson
Chairman & CEO
Interglobal Paratronics, Inc.
davi...@net1.net
http://www.ezez.com/ "The Center of the Web[tm]"
Ipse Libero
View our customer's web site at http://www.paradigm-motorsports.com/
View our customer's web site at http://www.ecologics.com/
View our favorite charity's web site at
http://www.houstonspacesociety.org/
"The Center of the Web" is a trademark of Interglobal Paratronics, Inc.
Edward Wright
>> of dollars trying to develop, unsuccessfully,
>
>>It is now being offered for sale
>> by a commercial mill in Austria.
>
>
>Is there not a conflict between these two statements?
Only if you believe the people who are saying only the government can fund
scientific research. (If the US government had developed it, they would
probably consider it a strategic material and not allow it out of the
country, let alone license the Austrians to produce it.)
Peter Mackay
In article <334ABF...@pacbell.net>,
rec.arts.sf.science,sci.space.science,rec.aviation.military wrote:
> Sure, you could magically render it transparent or something, but
> that's
> not what stealth does. No, Stealth technology wouldn't work with
> visible
> light. I'll accept that something could, but it wouldn't be
> accurate to
> refer to this hypothetical something as 'Stealth'.
Couldn't you make it out of transparent material with a matte finish? I
recall speculation on this during WW2, and a picture was published of a
very FW-190-ish looking fighter that had a pilot, an engine, a couple of
guns and a bunch of struts covered in transparent material.
~ m
u U Cheers!
\|
|> -Peter Mackay
/ \ pete...@netinfo.com.au
_\ /_
joseph james doyle
On 1 Apr 1997, James Summers wrote:
(summary of _Predator_-type invisibility suit deleted)
>
>This sounds good, except... What does "behind" mean? Remember, you're
>talking about a 3-dimensional object here. When you look straight at it, only
>the area in the "center" has the same "behind" as what you're looking at. If
>you look at a place half way between the center and the edge, it's "behind" is
>off to the side of the "behind" from your perspective, so you would see a very
>distinct distortion. In fact, if the the object were a sphere, you would see
>sky at the bottom and dirt at the top. Not very stealthy.
>
>Me thinks traditional camo works better than this.
>
You miss the point. There are sensors/emitters distributed evenly on
the the entire surface of the suit, and a computer to control each emitter.
If you were a cylinder (bear with me for the sake of simplicity/argument),
and wearing this suit, the computer would, for any given emitter, draw a
diameter to the opposite side, see what that corresponding detector was
seeing, then instruct the original emitter to emit a photon(s) of equivalent
wavelength. So, by doing that continuously around the entire circumference,
you get total camoflague.
Obviously, this is computationally expensive; I doubt it could be
done now, period. But, you can approximate the result with lower
"resolution", or just wait for computers to get three or four orders of
magnitude faster.
For a related topic, look up "phased array optics" in the context
of molecular nanotechnology. There should be some decent estimates of
the computing resources neccessary to pull the trick off.
Also, in the Anime movie _Ghost in the Shell_, there is a
similar concept, called "thermoptic camoflague". Except here, the "suit"
also cloaks your IR signature, which would cook you rather quickly.
-Joe Doyle
Mathematics and Computer Science
University of Illinois, Urbana-Champaign
"I'm sorry, did I break your concentration? Oh! You're finished! Well,
allow me to retort..."
-from _Pulp Fiction_
air...@csrlink.net
On 9 Apr 1997 20:42:21 GMT, jtab...@ural.colorado.edu (Jack Tabaska)
wrote:
You're right, a sliding door would be very quick and much more
convenient. But think about this, there is no way you can make the
plane 100% stealth unless you replace the weaponary configuration with
it's own flat-shaped weaponary bombs, and everything that's inside the
bay would be all flat.
nicholas louis rogal
Or if it was a 2 dimensional plane, then the whole thing would be flat.
John McLaughlin
> > > (Rumor has it that the underside of
> > >the F-117A was to be painted light blue, to be less conspicuous against
> > >the background sky for ground observers, but the Air Force didn't like
> > >pastel colors.)
Didn't the US army paint their desert tanks a light pastel pink
because it best camoflaged them in the desert? I really don't
think colour asthetics comes into matters of life and death.
-John McLaughlin
Peter Mackay
In article <335195af...@news.csrlink.net>,
air...@csrlink.net wrote:
> You're right, a sliding door would be very quick and much more
> convenient. But think about this, there is no way you can make the
> plane 100% stealth unless you replace the weaponary configuration with
> it's own flat-shaped weaponary bombs, and everything that's inside the
> bay would be all flat.
And when the bomb(s) leave the bay, you stuff up your stealth until you get
the doors closed again.
Let's face it, there's no easy way to drop bombs and keep your stealth.
Given that a very short time after you drop your bombs, there will be a
certain lack of surprise, what's the point?
The bomb bay will only be open for a short time. By the time anybody
notices, the weapons will be in flight, the doors will have closed again,
and the plane will have moved on.
Sure, you know something's there, but all you can do is alert the defences
for a better look after the weapons have impacted, and you're going to do
that anyway, right?
John F. Eldredge
John McLaughlin <John.Mc...@cbr.dit.csiro.au> wrote:
I work next to a railroad yard. During and shortly after Desert
Storm, I saw a lot of tanks and other military vehicles being
transported by train. All of them were painted in shades of yellow,
tan, and brown. I didn't see any pink vehicles.
--
John F. Eldredge -- eldr...@poboxes.com
PGP key available from http://www.netforward.com/poboxes/?eldredge/
--
"There must be, not a balance of power, but a community of power;
not organized rivalries, but an organized common peace." - Woodrow Wilson
B. Vermo
|Brian Trosko wrote:
|
| Everyone here seems to be laboring under some misapprehension that
| stealth
| is some magic turn-the-plane-invisible technology. It's not.
| Stealth
| just makes detection *harder*, not impossible.
Quite. Nor is the 'stealth' technology by any means new. I remember
a test from the seventies where a porsche was cowered with radar-
absorbing foam. It was not difficult to purchase the stuff, but it
was rather pricey since it was silver based and a low-volume product.
The front area of the 911 was small enough that contemporary police
radar would not get a good reading until it was quite close in the
first place. With the absorbing foam added, the radar did not get a
reading until you were near enough to recognize the operator.
I wonder how a large array of laser diodes would affect contemporary
laser speed measurement? The things must be built to a limited budget,
so they should not be all that difficult to fool?
Dan Ford
> > "E pur, / sic muove!"
> > / Galileo Galilei
>
> Which is just a popular myth: Galileo would have been insane to say
> anything of the sort, and there is no evidence that he actually
I saw his tomb the other week, in Santa Croce in Florence. Very
impressive. In fact, the most impressive there. Sally told me that the
Italians waited a hundred years before they let him into Santa Croce, just
in case it turned out that the Earth *didn't* move around the Sun. Where
do you suppose she picked up that bit of knowledge? I didn't notice
anything about sic muove, but of course I was admiring the telescope.
Enrico Fermi is in there too. His epitaph is taken from the Inferno, which
I thought was pretty funny, tho I don't think it was meant to be. As near
as I could reckon, it said: "But I measure myself against the width of the
open sea."
You have to hand it to those Italians. They build a damn fine tomb.
- Dan
David Brown
This brings me back to the Engineering joke:
If farmer Bob is travelling at the speed of light in his pickup track and
he truns on his headlights. Would they work?
Dave Brown
B. Vermo
In article <Pine.OSF.3.91a.97041...@christa.unh.edu>,
Dan Ford <d...@christa.unh.edu> wrote:
|
|> > "E pur, / sic muove!"
|> > / Galileo Galilei
|>
|> Which is just a popular myth: Galileo would have been insane to say
|> anything of the sort, and there is no evidence that he actually
|
|I saw his tomb the other week, in Santa Croce in Florence. Very
|impressive. In fact, the most impressive there. Sally told me that the
|Italians waited a hundred years before they let him into Santa Croce, just
|in case it turned out that the Earth *didn't* move around the Sun.
One thing: it should read "e pur, si muove".
Apparently, the quote is an invention from the second half of the 18th
century. But if you have not read Galileo's 'Dialogo', I can certainly
recommend it. You will find that very much 'common knowledge' about
the controversy was invented in the 'age of enlightenment'.
Galileo displays much deficient reasoning and mathematical errors by
modern standards, but many of his examples are quite interesting. And
his work was protected and encouraged by Maffeo Barberini (Pope Urban VIII).
The anti-Kopernican faction in the Church was not nearly as powerful
as later myth would have it. But Galileo made one fatal error. The
pope urged him to write the Dialogo in defence of the Kopernican
system, but to add a statement that "God in his endless power and
wisdom can give to the element of water its ocillatory movement
in many different ways, even such as are inscrutable to our intellect".
He received the imprimatur, and the book was printed in Firenze without
the Pope seeing the final script.
The work is formed as a discussion in the palace of Giovan Francesco
Sagredo with the wise Filippo Salviati and the rather less illustrious
Simplikio, who is used as the ignorant defender of old Aristotelian
thinking and who asks all the silly questions.
The grave error made by Galileo was that at the end he put the words of
the pope in the mouth of Simplikio. The wrath of Urban VIII was not
long delayed. Galileo's main supporter in the curia was sent away as
governor of Montalto and never allowed to return to Rome, and Galileo
was ordered to meet before the inquisitional court in Rome.
Dialogo was confiscated but not destroyed, and was not reprinted
until 1744.
Rene Schickbauer
> If farmer Bob is travelling at the speed of light in his pickup track and
> he truns on his headlights. Would they work?
Try it, if you can drive a pickup truck this fast!
Stuart Brierley
Rene Schickbauer wrote:
>
> > If farmer Bob is travelling at the speed of light in his pickup track and
>
> > he truns on his headlights. Would they work?
>
Well, assuming the lights haven't broken with stress of light speed, sure they would work.
Its just that you wouldn't see the beams in front of you, because you are travelling at light
speed.
Stu.
Loki
> > If farmer Bob is travelling at the speed of light in his pickup track and
>
> > he truns on his headlights. Would they work?
>
at the speed of light. Hence, the lights would work as the truck would
never quite reach a velocity of c.
---------------------------------------------
A.J. King
Director of Publicity, UKSEDS
(United Kingdom Students for the Exploration
and Development of Space)
E-mail: aj...@leicester.ac.uk
Web: http://www.gbnet.net/orgs/seds
---------------------------------------------
Michael Chen
Stuart Brierley wrote:
>
> Rene Schickbauer wrote:
> >
> > > If farmer Bob is travelling at the speed of light in his pickup track and
> >
> > > he truns on his headlights. Would they work?
> >
>
>
> Its just that you wouldn't see the beams in front of you, because you are travelling at light
> speed.
>
> Stu.
I had always thought that this was one of those anti-intuitive "frame of
reference" relativity things. If you were driving at the speed of light
and turned on your headlights, YOU (in the truck) would see the
light from the headlights fan out in front of you as normal, but someone
else, standing around watching you go by, would not see any light coming
from your headlights.
Mike
BlackBeard
In article <3360C3...@imagicgames.com>, Michael Chen
<mc...@imagicgames.com> wrote:
> > Stu.
>
> I had always thought that this was one of those anti-intuitive "frame of
> reference" relativity things. If you were driving at the speed of light
> and turned on your headlights, YOU (in the truck) would see the
> light from the headlights fan out in front of you as normal, but someone
> else, standing around watching you go by, would not see any light coming
> from your headlights.
>
Correct... The defining term is 'relativity'.
No wonder he called it that.... ;)
BlackBeard
-. .- -..- --.-
De Profundis
Submarines once, Submarines twice...
gram
Loki (aj...@le.ac.uk) wrote:
: > > If farmer Bob is travelling at the speed of light in his pickup track and
: > > he truns on his headlights. Would they work?
: > Try it, if you can drive a pickup truck this fast!
: You couldn't. Special relativity prohibits objects with mass travelling
: at the speed of light. Hence, the lights would work as the truck would
: never quite reach a velocity of c.
And that deer is going to barely have time to freeze in the glare.
_Serious_ radiator damage.
--
Ward Griffiths
"Men will never be free until the last king is strangled with the entrails
of the last priest." [Denis Diderot, "Dithyrambe sur la fete de rois"]
Erik Max Francis
Michael Chen wrote:
> I had always thought that this was one of those anti-intuitive "frame of
> reference" relativity things. If you were driving at the speed of light
> and turned on your headlights, YOU (in the truck) would see the
> light from the headlights fan out in front of you as normal, but someone
> else, standing around watching you go by, would not see any light coming
> from your headlights.
You've got the right idea. Replace "driving at the speed of light" with
"driving nearly at the speed of light" and you've got the right idea. The
trouble with the above statement is that no massive particle can travel at
c; it would take an infinite amount of kinetic energy to achieve that.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"The future / is right there."
/ Bill Moyers
Erik Max Francis
Stuart Brierley wrote:
> Well, assuming the lights haven't broken with stress of light speed,
> sure they would work.
>
> Its just that you wouldn't see the beams in front of you, because you
> are travelling at light
> speed.
No. No massive particle can travel at c.
You can travel as close as you like; (1 - epsilon) c is just fine.
However, in that case, even when travelling at just a snail's pace under
the speed of light, everything looks perfectly normal to you. Your
flashlight works normally, you detect photons moving at c, etc. That's
because in your own inertial frame, you're perfectly at rest. That's why
they call it relativity.
Ash Wyllie
>Loki (aj...@le.ac.uk) wrote:
>: > > If farmer Bob is travelling at the speed of light in his pickup track
>: > > and he truns on his headlights. Would they work?
>: > Try it, if you can drive a pickup truck this fast!
>: You couldn't. Special relativity prohibits objects with mass travelling
>: at the speed of light. Hence, the lights would work as the truck would
>: never quite reach a velocity of c.
>And that deer is going to barely have time to freeze in the glare.
>_Serious_ radiator damage.
>--
Naw, the deer wouuld be vaporized by blue shifted headlights.
-ash
Kusakabe Youichi
--
ヘ_ヘ ------------------------
ミ・・ ミ vo...@merope.opus.or.jp
( ° )～ 日下部陽一
----------------------------------
Loki <aj...@le.ac.uk> wrote in article
<Pine.SGI.3.91.970425113505.28702A-100000@hawk>...
> > > If farmer Bob is travelling at the speed of light in his pickup track
and
> >
> > > he truns on his headlights. Would they work?
> >
> > Try it, if you can drive a pickup truck this fast!
>
> You couldn't. Special relativity prohibits objects with mass travelling
> at the speed of light. Hence, the lights would work as the truck would
> never quite reach a velocity of c.
>
PBlase
>>>The doors open outward for the same reason that closet doors open
outward.
>If the doors open inward, where do you put the bombs?
>I was kind of thinking along the lines of doors that roll up the
inside of the fuselage.
Why bother, when you're dropping the bombs you're beyond the need for
stealth right then.
As to the original question as posed in the title, it's called painting
the craft black and operating at night (gee, just like the F-117 and B-2).
Stealth doesn't make a craft invisible, merely very difficult to see;
exactly like trying to see a black cat on a dark night.
bla...@freenet.edmonton.ab.ca
Ash Wyllie (as...@lr.net) wrote:
: >Loki (aj...@le.ac.uk) wrote:
: >: > > If farmer Bob is travelling at the speed of light in his pickup track
: >: > > and he truns on his headlights. Would they work?
: >: > Try it, if you can drive a pickup truck this fast!
: >: You couldn't. Special relativity prohibits objects with mass travelling
: >: at the speed of light. Hence, the lights would work as the truck would
: >: never quite reach a velocity of c.
: >And that deer is going to barely have time to freeze in the glare.
: >_Serious_ radiator damage.
: >--
: Naw, the deer wouuld be vaporized by blue shifted headlights.
And if not, there's always the sonic boom.
===================== ====================================
BLAINE GORDON MANYLUK email: bla...@freenet.edmonton.ab.ca
EDMONTON, AB
C Rasmussen
In article <5k1p1f$j1g$2...@news.sas.ab.ca>,
bla...@freenet.edmonton.ab.ca says...
>
>Ash Wyllie (as...@lr.net) wrote:
>
>: >Loki (aj...@le.ac.uk) wrote:
>: >: > > If farmer Bob is travelling at the speed of light in
his pickup track
>: >: > > and he truns on his headlights. Would they work?
>: >: > Try it, if you can drive a pickup truck this fast!
>: >: You couldn't. Special relativity prohibits objects with
mass travelling
>: >: at the speed of light. Hence, the lights would work as the
truck would
>: >: never quite reach a velocity of c.
>
>: >And that deer is going to barely have time to freeze in the
glare.
>: >_Serious_ radiator damage.
>: >--
>: Naw, the deer wouuld be vaporized by blue shifted headlights.
>
>And if not, there's always the sonic boom.
Sorry, no sonic boom at that speed, but the cherenkov
radiation would probably make sure that if the deer didn't get
hit, he wouldn't have to worry about making little deer.
Scott Brumage
In article <5k62pg$a...@eeyore.planet.eon.net>, chri...@planet.eon.net (C
Rasmussen) wrote:
Hmmm... While it would be imprudent to comment on the rather silly
scenarios discussed here, the original poster seemed to want to know "Can
Stealth Technology work with light waves?"
Yes.
We call it camouflage.
Some of the noteworthy examples I've read about include some of the
angular paint patterns applied to certain fighters that are intended to
confuse aspect angle or orientation (seem to remember some Canadian
F/A-18's that had false canopies painted on the undersurface of the
plane); similarly the false-wavecrest painted on the front of some naval
vessels that made it difficult to estimate speed (as viewed from a sub
periscope in WWII); use of external lights to match ambient luminosity;
and I suppose in the infrared spectrum the use of some kind of IR jammer
on certain helos (?). I've never read any description of how an infrared
jammer might work (not talking about flares here), or even if such a
device actually exists.
Is there such a thing as LIDAR, and if so, what are it's capabilities and
intended use? Are there any countermeasures, if this is some form of
active (not IR passive sensing) device? Are there paints or materials
that would diffuse, scatter, absorb, or refract LIDAR emmissions so as to
counter them and not compromise "normal" visibility?
Mark Andrew Spence
Scott Brumage wrote:
>
> Hmmm... While it would be imprudent to comment on the rather silly
> scenarios discussed here, the original poster seemed to want to know "Can
> Stealth Technology work with light waves?"
> Yes.
> We call it camouflage.
>
AFAIK, the answer is no.
Current stealth technology, e.g., F-117, works on the
angle-of-incidence-equals- angle-of-reflection rule. With radar, this is
not a a problem because the electro-magnetic radiation is emitted in one
direction only.
Solar radiation, i.e., light, is diffuse. Its intensity is equal in all
directions. No way to deflect all of it. Some of it is always going to
strike an object from such an angle that it will be reflected back
towards an observer, regardless of where he may be.
Perhaps that's why stealth planes like to operate at night.
M.S.
M.S.
Joe Vincent
C Rasmussen wrote:
>
> In article <brumage-3004...@algonquin.acns.fsu.edu>,
> bru...@acns.fsu.edu says...
>
> >Hmmm... While it would be imprudent to comment on the rather silly
> >scenarios discussed here, the original poster seemed to want to know "Can
> >Stealth Technology work with light waves?"
> >Yes.
> >We call it camouflage.
> >
SNIP
>
> Yes there are infa-red jammers mounted on helicopters,( perhaps on
> fixed wing aircraft as well, though I've never personally come across it )
> you can spot them as small faceted mirrored domes, usually mounted near
> the engine exhaust.
SNIP
> -- C. Rasmussen
I believe, if you can check it out, you will find that some versions of
the Suchoi Su-24 "Fencer" have just such equipment on their dorsal area.
--
Joe Vincent YGBSM!
jvin...@netten.net
My return address field is inaccurate to spoil spammers.
C Rasmussen
>Hmmm... While it would be imprudent to comment on the rather silly
>scenarios discussed here, the original poster seemed to want to know "Can
>Stealth Technology work with light waves?"
>Yes.
>We call it camouflage.
>
>Some of the noteworthy examples I've read about include some of the
>angular paint patterns applied to certain fighters that are intended to
>confuse aspect angle or orientation (seem to remember some Canadian
>F/A-18's that had false canopies painted on the undersurface of the
>plane); similarly the false-wavecrest painted on the front of some naval
>vessels that made it difficult to estimate speed (as viewed from a sub
>periscope in WWII); use of external lights to match ambient luminosity;
>and I suppose in the infrared spectrum the use of some kind of IR jammer
>on certain helos (?). I've never read any description of how an infrared
>jammer might work (not talking about flares here), or even if such a
>device actually exists.
>Is there such a thing as LIDAR, and if so, what are it's capabilities and
>intended use? Are there any countermeasures, if this is some form of
>active (not IR passive sensing) device? Are there paints or materials
>that would diffuse, scatter, absorb, or refract LIDAR emmissions so as to
>counter them and not compromise "normal" visibility?
Yes there are infa-red jammers mounted on helicopters,( perhaps on
fixed wing aircraft as well, though I've never personally come across it )
you can spot them as small faceted mirrored domes, usually mounted near
the engine exhaust. ( I can't remember the actuall designations off hand,
I'll have to hit the books and see if I can find it. ) They are called
'passive' IR jammers to differentiate them from flares.
How do they work? I don't know, but I would hazard a guess that
they either radiate at a IR frequency to interact with exhaust signature (
like red-green-blue lights look white ) to make them less visible to the
seeker head. Or the they create a bright IR signature, but do it
intermittently, flashing on and off, so that the missile keeps loosing
it's lock.
( Hey, if anyone DOES know, tell me :)
As for Lidar: it does exist, but I don't think operationally. It
uses a laser pulse to determine direction, range and (with doppler) speed.
If you have a powerful enough laser and the right equipment, you can also
get a spectral analysis of what the target's made of ( during beam weapon
research one of the ways to tell if the target was destroyed was to detect
the increased carbon from the vapourized pilot, cute. )
The problems with Lidar are short range ( varies depending on the
clarity of the atmosphere ) and mostly, the long scan time. It takes a LOT
longer for a pencil thin laser beam to pain the sky than a broad cone
shaped radio beam.
There are also experiments with electrochromatic panels on
aircraft to change their colour from white to dark blue-grey and back in
short time. This can either be used to "flicker" the aircraft, or to match
the colour of the background.
-- C. Rasmussen
Doug Lampert
In article <5kbe4g$h...@eeyore.planet.eon.net>,
>fixed wing aircraft as well, though I've never personally come across it )
>you can spot them as small faceted mirrored domes, usually mounted near
>the engine exhaust. ( I can't remember the actuall designations off hand,
>I'll have to hit the books and see if I can find it. ) They are called
>'passive' IR jammers to differentiate them from flares.
> How do they work? I don't know, but I would hazard a guess that
>they either radiate at a IR frequency to interact with exhaust signature (
>like red-green-blue lights look white ) to make them less visible to the
>seeker head. Or the they create a bright IR signature, but do it
>intermittently, flashing on and off, so that the missile keeps loosing
>it's lock.
> ( Hey, if anyone DOES know, tell me :)
Since I do not know, I am allowed to tell you. My guess would be that
the IR jammer radiates a large amount of short wave IR. Modern IR
detectors generally have two detection bands and compute a 'color
temperature' from the ratio of the intensities. Newer anti-aircraft
missiles are programmed to ignore targets with too high a color temperature
on the assumption that they are flares, and only go for targets cool
enough to be engine exhaust.
DougL
Jim Stevenson's reader
Erik Max Francis <m...@alcyone.com> writes:
>Stuart Brierley wrote:
>> Well, assuming the lights haven't broken with stress of light speed,
>> sure they would work.
>>
>> Its just that you wouldn't see the beams in front of you, because you
>> are travelling at light
>> speed.
>No. No massive particle can travel at c.
>You can travel as close as you like; (1 - epsilon) c is just fine.
>However, in that case, even when travelling at just a snail's pace under
>the speed of light, everything looks perfectly normal to you. Your
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ah not quite true if you are lokking out a 'window' of a ship
traveling near the speed of light. The stars around you will be blue
shifted in front of you and pushed into a increasingly smaller space.
Also at the aft end of this near ftl ship your event horizen will be,
ahh I think red shifted if memory serves me correctly ( reference: Carl
Sagan's PBS seris concerning Cosmos.
>flashlight works normally, you detect photons moving at c, etc. That's
>because in your own inertial frame, you're perfectly at rest. That's why
>they call it relativity.
A yea, but radition ( ie: visible light ) from outside sources (
ie the sun, stars, other constellations, etc will be red or blue shifted
depending if the sources are 'ahead' or 'behind' the approaching near
lightspeed object.
Joshua Turner
> Is there such a thing as LIDAR, and if so, what are it's capabilities and
> intended use? Are there any countermeasures, if this is some form of
> active (not IR passive sensing) device? Are there paints or materials
> that would diffuse, scatter, absorb, or refract LIDAR emmissions so as to
> counter them and not compromise "normal" visibility?
I don't know if the military is using it, but there certainly is such a
thing as LIDAR--police have been using it to track speeders. Advantages:
Supposedly greater accuracy, and it doesn't set off radar detectors.
Disadvantages? Because of the narrow beam (the thing that supposedly
gives it greater accuracy), it has to be manually aimed at a target. In
military terms, this last would be a killer.
As far as jamming LIDAR goes, it's apparently a piece of cake. Bright
lights and a lack of reflective surfaces have, in tests conducted by Car
and Driver, made cars invisible or nearly so to LIDAR devices. Same
thing would work in military applications, I suppose.
Brian Trosko
Joshua Turner <sh...@umich.edu> wrote:
: Supposedly greater accuracy, and it doesn't set off radar detectors.
: Disadvantages? Because of the narrow beam (the thing that supposedly
For the cops, that's an advantage; they know exactly what car they just
pegged, as opposed to waving the beam at a bunch of traffic and getting a
return off a random car.
: gives it greater accuracy), it has to be manually aimed at a
: target. In
: military terms, this last would be a killer.
What? Military applications use lasers all the time to hit specific
targets; LGBs, laser-guided missiles, and others all entail a laser beam
bipping a target and having a projectile guide in on the beam. And a
technology like LANTIRN entails, among other things, continuous
interrogation of the ground ahead of the aircraft with an infrared laser
beam.
: and Driver, made cars invisible or nearly so to LIDAR devices. Same
: thing would work in military applications, I suppose.
A bit different. A LIDAR gun needs a return off of a reflective surface.
A laser-guided bomb doesn't see the beam; it sees the breakup of the beam
where it hits a surface.
Joshua Turner
Brian Trosko wrote:
>
> Joshua Turner <sh...@umich.edu> wrote:
> : Supposedly greater accuracy, and it doesn't set off radar detectors.
> : Disadvantages? Because of the narrow beam (the thing that supposedly
>
> For the cops, that's an advantage; they know exactly what car they just
> pegged, as opposed to waving the beam at a bunch of traffic and getting a
> return off a random car.
Well, that's the "supposedly" part--recent indications (see Car and
Driver May 97 p. 127) are that it's harder to tell which car you're
hitting than is previously thought. The reason is that the beam is
invisible to the eye, so you might be getting returns off the car *next*
to the one you're trying to hit.
> : gives it greater accuracy), it has to be manually aimed at a
> : target. In
> : military terms, this last would be a killer.
>
> What? Military applications use lasers all the time to hit specific
> targets; LGBs, laser-guided missiles, and others all entail a laser beam
> bipping a target and having a projectile guide in on the beam. And a
> technology like LANTIRN entails, among other things, continuous
> interrogation of the ground ahead of the aircraft with an infrared laser
> beam.
Yes, absolutely, but the orignal poster wasn't asking about lasers in a
targeting capacity--he was asking if LIDAR was in use as an air-search
device. The narrow beam (as another poster has sinced mentioned) means
that it would take forever for you to sweep the sky--in search
applications (as opposed to precision targeting, where you already have
a general idea where the target is), a wider beam is better.
> : and Driver, made cars invisible or nearly so to LIDAR devices. Same
> : thing would work in military applications, I suppose.
>
> A bit different. A LIDAR gun needs a return off of a reflective surface.
> A laser-guided bomb doesn't see the beam; it sees the breakup of the beam
> where it hits a surface.
But even in this respect, wouldn't IR emitting surfaces be able to
"dazzle" the recpeptor? As I understand it, laser seeker heads use a
grid system to determine which way to move the guidance fins. The seeker
head moves the fins to try and keep the laser reflected from the target
in the center of the grid. If you filled the grid with light, the bomb
wouldn't know which way to go...
Anyway, it's important to keep in mind that LIDAR (detection and
ranging) has a very different purpose from targeting--and the orignal
question was about searching for targets.
Erik Max Francis
Jim Stevenson's reader wrote:
> >However, in that case, even when travelling at just a snail's pace under
> >the speed of light, everything looks perfectly normal to you. Your
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Ah not quite true if you are lokking out a 'window' of a ship
> traveling near the speed of light. The stars around you will be blue
> shifted in front of you and pushed into a increasingly smaller space.
> Also at the aft end of this near ftl ship your event horizen will be,
> ahh I think red shifted if memory serves me correctly ( reference: Carl
> Sagan's PBS seris concerning Cosmos.
Event horizon? No black holes here, sir.
Yes, you get aberration and redshifting, so everything in front of you is
compressed into a circle in front and blueshifted, and everything behind
you is similarly compressed and redshifted.
However, I was referring to local matters. Sure, things that are not
moving with you are going to look weird; I was specifically talking about
one's local environment. If lift a pen and drop it under thrust it's going
to look the same whether or not you're at rest, or travelling at Mach 2, or
travelling at 0.99 c. In a closed ship with no windows, you would have no
way of determining what your speed is. This is the essence of special
BlackBeard
>
> Anyway, it's important to keep in mind that LIDAR (detection and
> ranging) has a very different purpose from targeting--and the orignal
> question was about searching for targets.
The answer is yes. We have LIDAR systems for search and tracking, and we
have LIDAR systems for targeting. I've worked with programs for wire
avoidance and recently heard about a program for a hand-held imaging LIDAR
system. The technology is advancing rapidly.
Doug Lampert
>"dazzle" the recpeptor? As I understand it, laser seeker heads use a
>grid system to determine which way to move the guidance fins. The seeker
>head moves the fins to try and keep the laser reflected from the target
>in the center of the grid. If you filled the grid with light, the bomb
>wouldn't know which way to go...
But that only works if he is so close that your jammer fills the
sensors FOV (field of view) (i.e. way to close for comfort).
Possibly you could use a LASER to saturate the sensor to such
an extent that internal scattering and diffusion saturates every
pixal, but a deffence system that involves a target aiming a light
beam at the other sides sensor is probably a poor idea. He need
only design a slightly more robust system to take advantage of the
guidance help.
Better if you know his targeting criteria well enough to spoof them
to arange to have the target look like a decoy, while the decoy
looks like a target.
DougL
Jacob McGuire
Excerpts from netnews.sci.space.policy: 8-May-97 Re: Can Stealth
Technology .. by Doug Lam...@s10.math.ua
>sensors FOV (field of view) (i.e. way to close for comfort).
>
>Possibly you could use a LASER to saturate the sensor to such
>an extent that internal scattering and diffusion saturates every
>pixal, but a deffence system that involves a target aiming a light
>beam at the other sides sensor is probably a poor idea. He need
>only design a slightly more robust system to take advantage of the
>guidance help.
Well, I know that there was a program to defend transport-size
aircraft against IR missiles by mounting a number of suitably strong
lasers to cover all angles, which upon detecting a missile, would
saturate/fry the IR seekers. Something like this could damage/fry the
sensitive detector elements in an LGB.
And there was a program designed to destroy ground-based optics (like
binoculars/sights) that would use a low-power laser to scan the terrain
for reflective objects, then use a higher-powered pulsed laser to
shatter the optical elements so detected. Something like this could
also work against LGB's.
--
Don't hate yourself in the morning - sleep until noon.
Jake McGuire mcg...@andrew.cmu.edu
Johnny TwoBit
> > Is there such a thing as LIDAR, and if so, what are it's capabilities and
> > intended use? Are there any countermeasures, if this is some form of
> > active (not IR passive sensing) device? Are there paints or materials
> > that would diffuse, scatter, absorb, or refract LIDAR emmissions so as to
> > counter them and not compromise "normal" visibility?
>
>
> I don't know if the military is using it, but there certainly is such a
> thing as LIDAR--police have been using it to track speeders. Advantages:
> Supposedly greater accuracy, and it doesn't set off radar detectors.
> Disadvantages? Because of the narrow beam (the thing that supposedly
> gives it greater accuracy), it has to be manually aimed at a target. In
> military terms, this last would be a killer.
>
> As far as jamming LIDAR goes, it's apparently a piece of cake. Bright
> lights and a lack of reflective surfaces have, in tests conducted by Car
> and Driver, made cars invisible or nearly so to LIDAR devices. Same
> thing would work in military applications, I suppose.
You can also use reflectors like the ones used on float-poles to mark
the position of fishermens nets. They consists of three surfaces aligned
at right angles to each other forming eight 'corners' or grooves. The
radar or laser light (works for both) bounces on several of these sur-
faces before they return and gives the impression that the target is
several times larger than it is. If you put pads on such a devise to
make it rotate in the wind of a moving object, the reader will get
conflicting and insane readings, like 0-500-0 Mph in seconds on a car,
effectively making the readings useless.
Such devices are illegal to use on cars where I live :-)
-- Johnny
unknown
C Rasmussen (chri...@planet.eon.net) wrote:
: Yes there are infa-red jammers mounted on helicopters,( perhaps on
: you can spot them as small faceted mirrored domes, usually mounted near
: the engine exhaust. ( I can't remember the actuall designations off hand,
: I'll have to hit the books and see if I can find it. ) They are called
: 'passive' IR jammers to differentiate them from flares.
: How do they work? I don't know, but I would hazard a guess that
: they either radiate at a IR frequency to interact with exhaust signature (
: like red-green-blue lights look white ) to make them less visible to the
: seeker head. Or the they create a bright IR signature, but do it
: intermittently, flashing on and off, so that the missile keeps loosing
: it's lock.
: ( Hey, if anyone DOES know, tell me :)
May be talking out of my posterior here, but I always thought that IR
"jammers" were just heatsinks to soak up exhaust heat. I'm pretty sure that
such jammers can't be kept on indefinitely, which seems to support this -
the heatsink would need to turn off to cool down after a while.
cheers
Mike C
C Rasmussen
In article <5l9k53$hmn$1...@bs33n.staffs.ac.uk>,
cm5...@bs47c.staffs.ac.uk says...
>May be talking out of my posterior here, but I always thought
that IR
>"jammers" were just heatsinks to soak up exhaust heat. I'm
pretty sure that
>such jammers can't be kept on indefinitely, which seems to
support this -
>the heatsink would need to turn off to cool down after a while.
>
>cheers
>Mike C
>
--
There are exhaust dampers that diffuse the exhaust
stream, the most obvious are on the AH-64 Apache. But these
things are mounted on the _front_ of the aircraft in some cases.
(Look at a RN Lynx HAS Mk3 ) They don't have any connection to
the engines.
So far far I've heard guesses ( many good ) but nothing
for sure. The best one so far as that they emit in IR
frequencies to make the helicopter radiate the same as a decoy
flare.
############################################################
---- "Germans of future generations will honour Herr Hitler
as a genius, as a brave man, a matchless organizer and much
more." --- Mahatma Ghandi June 22, 1940
--- "Anybody can make mistakes." --- C. Rasmussen
------------------------------------------------------------
-- chri...@planet.eon.net ---- alone in the frigid north --
############################################################
Paul J. Adam
In article <5le2vs$d...@eeyore.planet.eon.net>, C Rasmussen
<chri...@planet.eon.net> writes
> There are exhaust dampers that diffuse the exhaust
>stream, the most obvious are on the AH-64 Apache. But these
>things are mounted on the _front_ of the aircraft in some cases.
>(Look at a RN Lynx HAS Mk3 ) They don't have any connection to
>the engines.
Those aren't IR suppressors, those are ESM antennae.
> So far far I've heard guesses ( many good ) but nothing
>for sure. The best one so far as that they emit in IR
>frequencies to make the helicopter radiate the same as a decoy
>flare.
No, that would _attract_ missiles, the idea of a flare being to produce
a more attractive target that isn't the helo.
The faceted IR jammers seen on many battlefield helos work by confusing
the hell out of mechanically-scanned IR seekers: the jammer radiates IR
pulses that interfere with the missile seeker's scan frequency.
--
There are four kinds of homicide: felonious, excusable, justifiable and
praiseworthy...
Paul J. Adam pa...@jrwlynch.demon.co.uk
C Rasmussen
In article <3BMk7sAw...@jrwlynch.demon.co.uk>,
pa...@jrwlynch.demon.co.uk says...
>
>In article <5le2vs$d...@eeyore.planet.eon.net>, C Rasmussen
><chri...@planet.eon.net> writes
>> There are exhaust dampers that diffuse the exhaust
>>stream, the most obvious are on the AH-64 Apache. But these
>>things are mounted on the _front_ of the aircraft in some cases.
>>(Look at a RN Lynx HAS Mk3 ) They don't have any connection to
>>the engines.
>
>Those aren't IR suppressors, those are ESM antennae.
>
International, pg 206 ) has two domed, faceted structures in front of the
aircraft above the pilot/copilot, and the caption reads,"...cabin-top IR
jammers..."
>> So far far I've heard guesses ( many good ) but nothing
>>for sure. The best one so far as that they emit in IR
>>frequencies to make the helicopter radiate the same as a decoy
>>flare.
>
>No, that would _attract_ missiles, the idea of a flare being to produce
>a more attractive target that isn't the helo.
>
It would IF there weren't 15 flares + helo, and IF the seeker head
hadn't been adjusted to try and differentiate between a flare and a
standard helicopter.
>The faceted IR jammers seen on many battlefield helos work by confusing
>the hell out of mechanically-scanned IR seekers: the jammer radiates IR
>pulses that interfere with the missile seeker's scan frequency.
>
>--
Yes, I have got an explanation,( after I made the above post )
indicating that it flashes in sinc with a mechanical scanning mask in the
seeker head ( much simplified here, the poster said it better and at length
) to disrupt the missile's tracking. Just living in a world of cheap,
customizable Charge Coupled Devices with electronic, scanning, I didn't
think that IR missiles were still so primitive. Learn something new every
day :-)
>There are four kinds of homicide: felonious, excusable, justifiable and
>praiseworthy...
>
>Paul J. Adam pa...@jrwlynch.demon.co.uk
>
--
29crosby
Paul J. Adam wrote:
>
> In article <5le2vs$d...@eeyore.planet.eon.net>, C Rasmussen
> <chri...@planet.eon.net> writes
> > There are exhaust dampers that diffuse the exhaust
> >stream, the most obvious are on the AH-64 Apache. But these
> >things are mounted on the _front_ of the aircraft in some cases.
> >(Look at a RN Lynx HAS Mk3 ) They don't have any connection to
> >the engines.
>
> Those aren't IR suppressors, those are ESM antennae.
>
> >for sure. The best one so far as that they emit in IR
> >frequencies to make the helicopter radiate the same as a decoy
> >flare.
>
> No, that would _attract_ missiles, the idea of a flare being to produce
> a more attractive target that isn't the helo.
>
> the hell out of mechanically-scanned IR seekers: the jammer radiates IR
> pulses that interfere with the missile seeker's scan frequency.
>
> --
> praiseworthy...
>
> Paul J. Adam pa...@jrwlynch.demon.co.uk
that cause the IR guided missile to 'think' there is a heat source
everywhere. I suppose this could cause a missile to explode depending on
the fusing, but the most likely result is it will get confused and not
know where to steer, thereby missing the target. I assume the labs are
working on IR scanning technology that won't be confused by these
systems. It seems to me, everytime somebody comes up with a really good
jammer, somebody else comes up with something that homes in on the
jammer.
Henry Spencer
In article <5lj4r7$o...@eeyore.planet.eon.net>,
C Rasmussen <chri...@planet.eon.net> wrote:
> ...living in a world of cheap,
>think that IR missiles were still so primitive. Learn something new every
>day :-)
It's a lot harder to build imaging chips in the thermal infrared than in
the visible and near-visible wavelengths. Experimental "staring array"
("staring" as opposed to "scanning") seekers are starting to appear, but I
don't think anybody's shipping operational IR missiles using them yet.
Even when that starts to happen, there will be plenty of IR missiles with
old-style seekers around for a long time to come; not only are there
rather a lot of them already on peoples' shelves, but they're easier and
cheaper to build.
(So how do you build countermeasures against staring-array seekers? Well,
there's got to be software behind it that turns the image into steering
commands, and you might be able to exploit limitations of the software.
Another possibility, which is being actively pursued already, is the
brute-force approach: using an IR laser to dazzle or even damage the
seeker head.)
--
Committees do harm merely by existing. | Henry Spencer
-- Freeman Dyson | he...@zoo.toronto.edu
John M. Cassidy
Check this months Popular Science. An article discusses this.
Apparently research done during WWII was abandoned because of radar and
has now been re-activated with the advent of "stealthy" aircraft, which
are limited to night-time ops.
The basic idea is to match the brightness of the aircraft with the
background by the use of powerful lights and light paintschemes.
Interesting.
--
Where other people have a nationality
The Irish and Jews have a phychosis.
Brendan Behan.
Robert Cook
John M. Cassidy wrote:
>
> Check this months Popular Science. An article discusses this.
> Apparently research done during WWII was abandoned because of radar and
> has now been re-activated with the advent of "stealthy" aircraft, which
> are limited to night-time ops.
"Stealthy" aircraft are not by definition limited to night-time
operations. Darkness is merely one form of stealth (visual)
that works for any aircraft.
- Robert Cook
PBlase
>>Apparently research done during WWII was abandoned because of radar and
has now been re-activated with the advent of "stealthy" aircraft, which
of the aircraft with the background by the use of powerful lights and
I was in the Air Force a while back, and while at Wright-Patterson AFB
talked to a guy that had played around with this for one of the labs at
W-P. They took an RPV, put "light bars" (strip lights) under the wings,
with a photocell on top of the plane and a circuit that adjusted the light
intensity to match that of the sky. He said that with the circuit turned
on, you couldn't see the thing overhead at 50 feet unless you know
_exactly_ where to look. The real problem was that they couldn't convince
the pilots that adding lights would help them stay hidden.
Note that this technique will not work with IR detection (warm aircraft
against cold sky), radar, or sound. For these you have to reduce emission
and reflection.