Radar Absorbent Material

Are they still using tiles of Radar Absorbent Material on the F-117? They were attached to its skin with adhesive and the gaps filled with special paint, but I read somewhere that the newer low-observable planes just use the paint -maybe �coating� is a better term- which can be "touched up" to preserve their low radar cross section if it gets chipped or otherwise damaged.

In one interesting online article I found it says that maintenance crews at Holloman Air Force Base do use strips of RAM to cover up the landing gear and conduct a radar evaluation of the individual planes to see what needs to be fixed. This creates a scenario where each aircraft has unique stealth characteristics. Seems not all black jets are created equal. Or maybe they were, but some have led rougher lives than others.

What exactly is �Radar Absorbent Material� anyway?

The information I find online seems to be pretty outdated. That�s pretty amazing considering that TV images and still photographs of the wreckage of a Nighthawk (F-117A #82-0806 downed near Belgrade, Yugoslavia in 1999) being picked over by civilians made it into the mainstream press. Plus, it has been in the operational inventory for at least 15 years. The most I can find is that the structural RAM is an �advanced composite� which does say much. Not being a materials scientist by any stretch, the only guess I could make is carbon fiber/epoxy blended with some sort of ferrite to make it bounce radar signals around inside the structure, a concept that dates back to the �Iron Ball� coating on the SR-71.

Heaven and the USAF only know what advances have been made in exotic RAM technology since the days of` �Iron Ball� paint (C-144). The F/A-22 is said to have these once supremely expensive materials on the most reflective surfaces, such as the leading edges of the wings, the bulk (by weight) of the airframe being titanium and aluminum. Since they are going to be produced in respectable numbers, along with the stealthy F-35 Joint Strike Fighter and RH-66 Comanche helicopter, the cost may have come down, too.

Maybe one day I will be able to afford enough to have the front of my car painted with RAM.

1.www.af.mil...
2.www.boeing.com...

I believe that there was a lengthy debate about this here on ATS before. One of the suggestions is that these aircraft may have an outer skin that also has electrostatic charge applied to it. A special paint may help with conductivity. This electrostatic charge may produce a slight anti-grav effect and reduce radar effects (though I am not clear on how this happens).

Yes, I caught the threads on plasma stealth, electromagnetic field manipulation, and other "Gee whiz" speculations. I was musing about the established nuts-and-bolts technologies -paints, coatings, alloys, composites, etc.- used to create aircraft with low radar cross-sections.

I have no doubt that the higher tech options are at least being developed; I just doubt that we will be reading much about them if after nearly 20 years of building stealth planes there is so little actually published about the basic techniques.

You can actually buy radar-absorbing car bras...though I'm not sure how well they work... Could help avoid that speeding ticket, hehe...

Originally posted by Spectre
In one interesting online article I found it says that maintenance crews at Holloman Air Force Base do use strips of RAM to cover up the landing gear and conduct a radar evaluation of the individual planes to see what needs to be fixed. This creates a scenario where each aircraft has unique stealth characteristics. Seems not all black jets are created equal. Or maybe they were, but some have led rougher lives than others.

I was stationed at Holloman AFB from late August 01 until mid September 02. In the frist part of my tour there I worked right on the flightline every morning doing checks on AAS, check my webpage to find out what that is. I got to watch, and saluate alot of pilots of the 117 as they rocketed down the runway, standing less than 200ft from the runway center line. Never got close enough to wear I can touch them.

I will say this however, with the conditions they fly under at HAFB, do a google search on it to see the area, and you can wonder why they are so worried about the radar signature. It is very possible for each aircraft to have a slightly different amout of radar absorbing capabilites do to all the sand that does fly up from White Sands.

As far as using RAM around landing gear and bomb hatches, I wouldnt expect the AF to have it any other way. If it wasnt coated and designed in the same way the rest of the plane, once the get ready to drop a bomb, opps I am visible on radar. Hence they use the RAM and modify the doors to have the same type of radar deflection patern the aircraft does.

How RAM really works? You will have to find a engineer who works with the # to be exact.

RAM used to be about material and construction, but new stealth technology does not rely on either.

the Paint has an absorbation method that "soaked" up high energy microwave pulses and then re-emitted the left over energy at a different wave length

the RAM material is a composite construction that had a surface layer with micro diamond shape patterns on it that defracts the radar signal in a multitude of directions thus scattering the signal return to the sending source as unrecognizable

and the new RAM / Stealth technology uses complex curves and an active "discharge" filter that modifies the incoming wave length and almost cancels out the energy by discharging it into the atmosphere around the craft creating an ionic effect. Like discharging the built up static when walking across carpet.

This effect makes the sending signal apear to go past the stealth object. As only a small channel is discharged ionically.

To my knowledge, RAM was first used in WWII by the Germans on their periscopes to escape the attentions of radar-equipped antisubmarine aircraft. The SR-71 used paint with iron balls in suspension to dissapate radr, plus that distinctive radar-reflecting chine all the way around the aircraft and its inwardly canted tailfins. (They initially made flying the plane feel very strange - left bank produced right yaw!) This was great and all, but they couldn't hide the damn exhaust plumes from radar!

Originally posted by Spectre
Are they still using tiles of Radar Absorbent Material on the F-117? They were attached to its skin with adhesive and the gaps filled with special paint, but I read somewhere that the newer low-observable planes just use the paint -maybe �coating� is a better term- which can be "touched up" to preserve their low radar cross section if it gets chipped or otherwise damaged.

In one interesting online article I found it says that maintenance crews at Holloman Air Force Base do use strips of RAM to cover up the landing gear and conduct a radar evaluation of the individual planes to see what needs to be fixed. This creates a scenario where each aircraft has unique stealth characteristics. Seems not all black jets are created equal. Or maybe they were, but some have led rougher lives than others.

What exactly is �Radar Absorbent Material� anyway?

The information I find online seems to be pretty outdated. That�s pretty amazing considering that TV images and still photographs of the wreckage of a Nighthawk (F-117A #82-0806 downed near Belgrade, Yugoslavia in 1999) being picked over by civilians made it into the mainstream press. Plus, it has been in the operational inventory for at least 15 years. The most I can find is that the structural RAM is an �advanced composite� which does say much. Not being a materials scientist by any stretch, the only guess I could make is carbon fiber/epoxy blended with some sort of ferrite to make it bounce radar signals around inside the structure, a concept that dates back to the �Iron Ball� coating on the SR-71.

Heaven and the USAF only know what advances have been made in exotic RAM technology since the days of` �Iron Ball� paint (C-144). The F/A-22 is said to have these once supremely expensive materials on the most reflective surfaces, such as the leading edges of the wings, the bulk (by weight) of the airframe being titanium and aluminum. Since they are going to be produced in respectable numbers, along with the stealthy F-35 Joint Strike Fighter and RH-66 Comanche helicopter, the cost may have come down, too.

Maybe one day I will be able to afford enough to have the front of my car painted with RAM.

1.www.af.mil...
2.www.boeing.com...

Well first of all there are many types of Radar Absorbing Materials out there. They vary from big flexable sheets that are like a thick foil textured materal that is non-metallic to a special paint coating.
Basiclly what RAM is comes down to this:
Ram is composed mainly of nonmetallic material imbedded with with magnetic praticals that convert radar energy into heat and then transfer the heat to the aircraft (or vehical) to avoid creating a detectable heat signature.

Tim
ATS Director of Counter-Ignorance

The design of RAM, and in particular, specular RAM is a design of single or
multilayer lossy dielectrics with specified scattering properties. While the loss
mechanisms through which RAM operates are on the atomic and crystal lattice levels
(microscopic), it is best to understand how it operates by taking a classical transmission
line approach for calculating the reflection and transmission properties of RAM.
For those with an electrical engineering background, RAM is simply the design
of a lossy distributed network which matches the impedance of free space to that
of a conducting body to be shielded.
Selecting the components of RAM is based on the fact that some things absorb
energy from electromagnetic fields that pass thru them. These things have indices
of refraction which are complex numbers. It is the imaginary component which
accounts for the loss and is analogous to the way a resistor converts electrical
current to heat.
Radar absorbers are loosely classified as "resonant" or "broadband". Thus "resonant"
RAM is effective only for a discreet frequency or a set of discreet frequencies. Broadband
RAM is effective over an entire band of frequencies. Anechoic chambers are not a good
example of flight RAM as this is the geometric transition approach to RAM where
volume is not a constraint.
It is difficult to achieve the bandwidths desired of microwave radar absorbers
(typically 2-18GHz) using a single-layer absorber so much of the work in this area
is in designing multiple layers based upon bandwidth specifications. If you want
to get familiar with the background necessary to work in this area, you can start
by studying Salisbury Screens and Dallenbach Layers. The bandwidth of a Salisbury screen
can be improved by adding additional resistive sheets and spacers to form a Jaumann absorber.
By varying the resistivity of the sheets, you enter the realm of graded dielectric absorbers.
Usually, commercial graded dielectric absorbers are constructed of discreet layers with
unique properties for each layer. If you wanted to play with some of this stuff,
you might see if AN-74 is still available from Emerson and Cuming. It is a 3 cm thick
three layered foam absorber that specs 20 db RCSR down to 3.5 GHz. To try this on
your car, you would smoothly cover your HEADLIGHTS, which are the singularly
brightest front aspect radar speculars on your vehicle. This would almost cut a typical
police radar detection range in half. (Front aspect only) But do not blame this post if you get fined.

1. Most states have fines for interfering with police radar, and the Judge will
not engage in the math arguments of passive versus active interferance.

2. This RAM treatment has NO EFFECT on IR Beam Speed Detectors.

3. Covering your headlights at night would be to advertise your ignorance, and other fines
would apply as well.


This is just touching on the subject, which with diligent research, can be found
in university libraries. A full coverage of RAM types would not be possible
in an unclassified format. So I will stop short of Magnetic RAM, circuit analog
absorbtion, and selective surface element geometries.

REF ::

1. W.W. Salisbury, "Absorbent Body for Electromagnetic Waves"

2. T.M. Connolly and E.J. Luoma, "Microwave Absorbers"

3. "Eccosorb H, Hair Type, Broadband Microwave Absorber", Technical Bulliten 8-21,
Emerson and Cuming, Jan 1973


/\/ight\/\/ing

Excellent information, NW. thanks--
I am not a student, so I have to rely on a friend who works at our local university library for material that I can't pick up at the public library or bookstore. I have asked if they have any of the publications you mentioned. That should make for some good 'light reading." Hopefully I can get my brain around some of it. This started off as a casual interest but the more I read, the more I want to learn. If I get the urge to go back to school, though, I blame ATS!

Don't worry. If I get busted whipping around with blacked out headlights, I'll leave you out of it. The sheriff's department is using laser these days, anyway.

"Don't worry. If I get busted whipping around with blacked out headlights, I'll leave you out of it." == Spectre

He...He... busted a gut over that one, thanks.
Have to be careful with things like that, there are some
on ATS that just may try such things.

/\/ight\/\/ing

Great, just great... I'm trying to bone up on RAM but now I can't get out of my head this image of me driving my mini-van --totally blacked out, using nightvision-- through a speed trap on the interstate at 100mph (I wish!) without setting off the radar. That would shake up local law enforcment enough to spill their coffee. Didn't that happen in a "Cannonball Run" movie or something?

Speaking of the more practical application of stealth, car magazines these days seem full of ads and articles about the ongoing battle of speed detection devices vs. detection and jamming devices. My favorite item is the "Spectre Radar Detector Detector (RDD)" for obvious reasons. There are a plethora of active anti-LASER/anti-RADAR methods and since most of the stuff is advertising I just don't know who to believe. Independant testing indicates that the police detectors are ahead of the active jammers. The LASER jamming sounds, in principle, like the infrared supression systems used on aircraft to foil heat-seeking missiles. RADAR jamming sounds like the ECMs I have heard about since Viet Nam. All this talk of "countermeasures" sounds like warfare to me.

At least it is accessible information and makes for a good distraction while waiting in a doctor's office.

with its midlife upgrade teh ram on the f-117 will be scraped off and replaced with a sprayed on type. From what i hear ram turns radar waves into either heat or magnetic energy. The Eurofighter, rafale, and grippen all claim to be stealthy, but they carry their stores on the outside so are they?

1. W.W. Salisbury, "Absorbent Body for Electromagnetic Waves"

2. T.M. Connolly and E.J. Luoma, "Microwave Absorbers"

nightwing, are these two books or technical articles? My library resources came up blank on them.

Spectre, the number two reference is available online ::

patft.uspto.gov.../netahtml/srchnum.htm&r=1&f=G&l=50&s1=4038660.WKU.&OS=PN/4038660&RS=PN/ 4038660


I forgot the classic nature of number one, it dates back to 1943. Might not be easy to find, even though its a classic. I will look for another place you can find it.

/\/ight\/\/ing

well that's y they never let u get too close to real planes with that paint. if u were a spy, the ingredients for this paint would be the biggest thing u could find