Anybody have any info the material used on the stealth aircraft to absorb
radar signals?

Standard stuff is a flexible plastic with powdered ferrite to match air, but
attenuate for no reflection, usually too heavy.
Stealth I think used a carbon material that matched air but had loss, also
in little hex patterns to keep the number of reflections high, more loss.
But they would not let us get that close to it 10 foot.
--Dwezil Smith

"Frank Alforo" wrote in message
...
Anybody have any info the material used on the stealth aircraft to absorb
radar signals?

Frank Alforo wrote:
Anybody have any info the material used on the stealth aircraft to absorb
radar signals?

I heard the first thing they ever tried was horsehair.
--
73, Cecil http://www.qsl.net/w5dxp



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"Frank Alforo" wrote in message
...
Anybody have any info the material used on the stealth aircraft to absorb
radar signals?



The 297 hits on Google for "radar absorbent material" was information
overload? The 3,730 hits for "RF anechoic material" frightened you? And the
70,100 hits for "stealth aircraft design" sent you scurrying here to see if
we had anything for you?

At least it's nice to see you doing your homework before Sunday night.

Ed
wb6wsn

"Ed Price" wrote in message
news:CAw9c.15750$Q45.10237@fed1read02...

"Frank Alforo" wrote in message
...
Anybody have any info the material used on the stealth aircraft to
absorb
radar signals?

The 297 hits on Google for "radar absorbent material" was information
overload? The 3,730 hits for "RF anechoic material" frightened you? And
the
70,100 hits for "stealth aircraft design" sent you scurrying here to see
if
we had anything for you?

At least it's nice to see you doing your homework before Sunday night.

Ed
wb6wsn

Tnx for the tip, Ed. Your point is well taken. But it seems to me that the
same can be said for the great majority of the posts seen here. Perhaps we
need a moderator to keep irksome and inane posts from cluttering up the
newsgroup and provoking the ire of the members who visit here.

Frank

"Frank Alforo" wrote in message
...

"Ed Price" wrote in message
news:CAw9c.15750$Q45.10237@fed1read02...

"Frank Alforo" wrote in message
...
Anybody have any info the material used on the stealth aircraft to
absorb
radar signals?

The 297 hits on Google for "radar absorbent material" was information
overload? The 3,730 hits for "RF anechoic material" frightened you? And
the
70,100 hits for "stealth aircraft design" sent you scurrying here to see
if
we had anything for you?

At least it's nice to see you doing your homework before Sunday night.

Ed
wb6wsn

Tnx for the tip, Ed. Your point is well taken. But it seems to me that the
same can be said for the great majority of the posts seen here. Perhaps we
need a moderator to keep irksome and inane posts from cluttering up the
newsgroup and provoking the ire of the members who visit here.

Frank


Naah, an official moderator isn't needed. Besides, he'd get burned out too
fast anyway.

BTW, absorbent material is NOT 377 ohms per square. The traditional
absorbent material is decidedly low-tech, consisting of open-cell urethane
foam with carbon particles dispersed along the cell walls. The grungy way to
make this is to cast a monster billet of foam, maybe 10' long by 4' by 4'.
The billet is then squashed flat in a press, and submerged in a solution of
carbon particles (lampblack; and seems I heard of that being made by
scraping the soot of a propane flame off of a copper block), water and
ethylene glycol (for wetting). The billet is allowed to expand, soaking up
the solution, and then drips dry. It's just like a huge kitchen sponge.
Particles of carbon are then left disperesed, almost painted, on the cell
walls. Then, after some more oven drying, they cut the billet, with a hot
wire, into those fancy pyramidal shapes. Then, some latex spray paint for
that high-tech blue or white look. And then they sell them to you for $175
per 24" square!

If you think of a plane wave propagating along, it has a 377 ohm wave
impedance over a unit area of wavefront. As the wave encounters the tips of
the pyramidal cones, a bit of the wave begins to encounter a slightly lower
impedance. As the wave propagates further, the impedance over the unit area
decreases. The wave begins to lose energy to ohmic heating of the lower and
lower impedance medium. Finally, at the base of the cones, the wave is
trying to propagate in a much lower than 377 ohm medium, and it's giving up
energy rapidly to warm the carbon particles. (With enough energy lost, it
might even melt the foam or ignite it.)

The tapered shape is used so as to present a gradual change in impedance.
The thing to avoid is any sudden change in impedance, which would result in
a reflection. There is much debate on optimizing the shape; right pyramids,
truncated pyramids, rotated sections of the pyramid, cones; some have
advantages in certain applications. The particles creating the loading can
be adjusted; sometimes ferrite particles are used with, or in place of, the
carbon.

(Before urethane foam was used, early researchers did use horse-hair. Maybe
one of them had some auto upholstery experience to draw on.)

All stealth is a combination of absorbing what you can, reflecting what you
can't (in more benign directions), trapping energy in labyrinths and
avoiding resonant structures (like exposed weapons or long panel seams,
etc). Another approach is to use multi-layer 'sandwiches" to create ohase
cancellation to a wave, but this is really difficult to optimize for more
than one frequency.

Ed
wb6wsn

The 297 hits on Google for "radar absorbent material" was information
overload? The 3,730 hits for "RF anechoic material" frightened you? And
the
70,100 hits for "stealth aircraft design" sent you scurrying here to see
if
we had anything for you?

At least it's nice to see you doing your homework before Sunday night.

Ed
wb6wsn


Wow. Good thing Frank is a seasoned ham; had he been a newbie you would
have just chased him from ham radio. Congratulations, Elmer!

Al W6LX

"Al Lorona" wrote in message
...

The 297 hits on Google for "radar absorbent material" was information
overload? The 3,730 hits for "RF anechoic material" frightened you? And
the
70,100 hits for "stealth aircraft design" sent you scurrying here to see
if
we had anything for you?

At least it's nice to see you doing your homework before Sunday night.

Ed
wb6wsn


Wow. Good thing Frank is a seasoned ham; had he been a newbie you would
have just chased him from ham radio. Congratulations, Elmer!

Al W6LX




Don't be an apologist for people who ask stupid or ill-phrased questions.
Don't pander to the lowest level. I provided a reply which I thought was
appropriate to the question. It was slightly sarcastic, though, by Usenet
standards, reasonably civilized. It provided three direct lines of search
for what was a very nebulous and obvious query. At no point did I attack the
poster, demean his mentality, question his civilization, or impugn the
length of his manhood.

Further, I hope your self-worth is well seasoned, or at least insulated, as
you don't seem to understand the difference between Usenet and Ham Radio.
Cranking off a dumb query on Usenet is equivalent to tuning up on a repeater
or net frequency. It's a bad use of electrons, and you can expect to be
chastised.

Perhaps I shouldn't be so harsh with you, as you can't seem to follow the
thread. If you were, you would have noticed that I provided considerable
background on RF absorbent material in a subsequent post.

Now, do YOU have anything informative to add to the subject, or are you just
trolling for sympathy? BTW, in addition to being in the dictionary,
"sympathy" yields about 3,700,000 hits on Google. Now there's a project for
your dotage.

Ed
wb6wsn

Ed wrote,

Don't be an apologist for people who ask stupid or ill-phrased questions.
Don't pander to the lowest level. I provided a reply which I thought was
appropriate to the question. It was slightly sarcastic, though, by Usenet
standards, reasonably civilized. It provided three direct lines of search
for what was a very nebulous and obvious query. At no point did I attack the
poster, demean his mentality, question his civilization, or impugn the
length of his manhood.

Further, I hope your self-worth is well seasoned, or at least insulated, as
you don't seem to understand the difference between Usenet and Ham Radio.
Cranking off a dumb query on Usenet is equivalent to tuning up on a repeater
or net frequency. It's a bad use of electrons, and you can expect to be
chastised.

Perhaps I shouldn't be so harsh with you, as you can't seem to follow the
thread. If you were, you would have noticed that I provided considerable
background on RF absorbent material in a subsequent post.

Now, do YOU have anything informative to add to the subject, or are you just
trolling for sympathy? BTW, in addition to being in the dictionary,
"sympathy" yields about 3,700,000 hits on Google. Now there's a project for
your dotage.

Ed
wb6wsn


Aha! Another pompous, sarcastic, smug, overbearing, insufferable post from
a
gentleman whose acumen is as nebulous as his reply is asinine. You should
get a job at a community college, Ed. College students are inured to your
particular brand of snide, demeaning discourse, since many teachers use
it as a technique for avoiding having to answer questions requiring knowledge
those teachers don't possess.
73,
Tom Donaly, KA6RUH

"Tdonaly" wrote in message
...
Ed wrote,

Don't be an apologist for people who ask stupid or ill-phrased questions.
Don't pander to the lowest level. I provided a reply which I thought was
appropriate to the question. It was slightly sarcastic, though, by Usenet
standards, reasonably civilized. It provided three direct lines of search
for what was a very nebulous and obvious query. At no point did I attack
the
poster, demean his mentality, question his civilization, or impugn the
length of his manhood.

Further, I hope your self-worth is well seasoned, or at least insulated,
as
you don't seem to understand the difference between Usenet and Ham Radio.
Cranking off a dumb query on Usenet is equivalent to tuning up on a
repeater
or net frequency. It's a bad use of electrons, and you can expect to be
chastised.

Perhaps I shouldn't be so harsh with you, as you can't seem to follow the
thread. If you were, you would have noticed that I provided considerable
background on RF absorbent material in a subsequent post.

Now, do YOU have anything informative to add to the subject, or are you
just
trolling for sympathy? BTW, in addition to being in the dictionary,
"sympathy" yields about 3,700,000 hits on Google. Now there's a project
for
your dotage.

Ed
wb6wsn


Aha! Another pompous, sarcastic, smug, overbearing, insufferable post
from
a
gentleman whose acumen is as nebulous as his reply is asinine. You should
get a job at a community college, Ed. College students are inured to your
particular brand of snide, demeaning discourse, since many teachers use
it as a technique for avoiding having to answer questions requiring
knowledge
those teachers don't possess.
73,
Tom Donaly, KA6RUH



Thomas obviously has problems with higher education, as his most potent
insult is to suggest that I teach at a community college. Oh, the horror!

Whatsa matter Tommy, did I hit a button on you? Some jackass community
college teacher give you a low grade, and it ruined your life? Nothing left
for you but trolling Usenet?

So here's my challenge to you, Tommy Twerp. Either add something useful
about RF absorbent materials, or go fellate an operating 5U4!

Ed
wb6wsn