"Paint-On" Antenna for Airships/Blimps

Just found this article about an antenna which can literally be painted onto the surface of an airship or blimp.

Here is an image of the SA-60 airship which the researchers used.

The article also points out that the company which carried out the research, RTI International, has links with NASA. Also the two other companies which teamed up with RTI on this research, Applied EM and Unitech, are carrying out similar research under the Air Force Small Business Innovative Research Program.

Could this technology be used on a military airship or stealth blimp? Could the RCS of a stealth blimp (a hot topic in black project circles at the moment) be reduced by using a paint on antenna or would the sheer size of such a blimp make it irrelevant?

Yes, it's not that unusual, The Volvo V70 has it's readio antenna "painted" in the left back window.

Isnt that just a piece of metal embedded in the glass? I think its something totally different to whats being talked about in the above article.

Well it's kinda orange. I have to ask my dad.

The innovation here is to get the conductivity up in order to reduce dissipation losses, and not develop a lot of microcracks when flexed. Then you have to do it over a wide range of frequencies. And not degrade in weather and sunlight, or ozone if it's lofted high enough. That's tougher than it sounds. You can do a paint-on for a rigid surface that's good for either high or low freqs fairly easily, especially if it's not exposed to weather. It gets a lot harder if you want to have a generic solution for a flexible surface that's got to last for more than a few days.

You probably DON'T want a surface that's a good antenna on your airframe if you want the RCS down. Just the opposite, if you could make it a total dielectric (more points if you give it the same dielectric constant as air) then it would be undetectable. Well, by conventional radar anyway. Unfortunately, that precludes doing anything useful with it, since people, electronics, cameras and so on tend to have metals or be conductive.

i thought the whole point of a stealth surface was to be dieletric? so as to absorb incoming radiation from the radar, spread it about and then send it on its way in another direction? (Possibly im wrong on that !)

A painted on antenna would be a great way to keep it all smoothed and flushed with the skin of an aircraft / blimp, thus keeping the reflectivity down to a bare minimum.

The stealth blimp wouldn't be like todays blimps would it though? I guess they would at least try to smooth it out and make it more streamlined / stealthy. Any how, thats just my two pennies worth - I would love to see a big airship in the skys though - what a way to travel!

Heres a great link that makes the argument for stealth blimps more solid and believable.

www.space.com...

[edit on 17/7/06 by GSA]

Hm. There's several facets (pun intended) to reducing observability.

Also I used the term 'dielectric' sloppily. What I meant by "total dielectric" but didn't say clearly was that if it had the same characteristics of air (no dissipation, no conductivity, relative permeability near 1), then you wouldn't get any return from the object's surface. Sort of like putting diamonds in a glass of distilled water to hide them. But it would be impractical, because anything useful inside it would reflect the radar instead.

Any surface/volume that doesn't have the same permittivity and permeability characteristics as the medium it's embedded in causes a discontinuity that can be detected, although it's easier to detect some types of discontinuity than others. That's why plywood aircraft have much less return.

In general, a good conductor presents a BIG discontinuity. You want an antenna to be really conductive, like a piece of metal. If you don't, then you'll lose power in dissipation losses that just heat up the antenna, but don't do anything to radiate a signal.

Unfortunately, that same characteristic of conductivity that makes metal a great antenna also makes it a great reflector for a radar target.

Think about radar targets...they're aluminized for a reason.

One characteristic of traditional RAM is that it is dissipative, and converts some percentage of the incoming radar signal to heat in the material instead of returning it. This can also make it a good reflector of what's left, but with RAM you do other stuff with the coating as well. One thing is that you can make a Salisbury screen, where you have a 377 Ohm/square conductive surface 1/4 wavelength over a reflective surface. This causes an intentional mismatch that bounces the reflection back and forth between the metal skin and the 377 Ohm/square dissipator. But that's only good for one frequency.

There's another trick called graded dielectric RAM that's less frequency dependent. You can also use lossy ferrite inclusions to turn the H-field component energy into heat instead of working on the E field components like graded dielectric does. (The F117 supposedly uses carbonyl ferrite dust to do this)

You can also shape the surface so that the returns are (theoretically) eliminated by directing the reflections away from the sender (sort of an anti-corner-cube) using Ufimtsev faceting. There are solutions to the edgewave equations that use concave and convex surfaces now, and thus you don't have to have that F117 look quite so much anymore, although the computational power required to solve it is massive.

There are better ways to do it these days, though.

None of them involve painting a highly conductive material on. Remember, a conductor, which that antenna paint is, is NOT a dielectric. Dielectrics are not conductors in the DC sense. You can google and find a term "dielectric conductivity" but this is the conductivity of displacement current, not conduction current.


[edit on 17-7-2006 by Tom Bedlam]

Oh I agree with you, I just was saying that having a paint on ariel was a great way to keep it flush with the skin as not to present a reflective surface from most angles.

On the top of a blimp would be a good idea if it was a high altitude craft , then it could just bounce around signals to satellites or other blimps ect.

How ever, i completely agree that a skin made totaly of this paint on ariel would be a nightmare!!!

I don't know about the Volvo, but there has been conductive paints out for a long time, that would be useful for purposes described in the first post.

I don't have any links to provide, sorry for that. But anyone who has been into electronics can tell you, it's out there. In electronics, it was useful for making patches to damaged circuit boards. But I'm sure the stuff that they used was probably a bit more conductive, and more durable (to withstand the elements).

It's been a long time, but I did remember that much about it.

Hope this little tidbit helps.

[edit on 7/17/2006 by Mechanic 32]

GFAD,
I don't want to change directions in this thread, but have you seen the work boeing did of putting the ariels and antenna into the flaps of the aircrafts wings? Its another idea to make the antenna more conformal dfor stealth applications - As you see its not directed towards blimps per se, but interesting none the less.

Oh and i have an article about passive radar systems being developed by china, and the only way to defeat such a network? you got it, slow moving stealthy blimps....

Passive radar? You mean a bistatic radar?

No I think its a totaly passive radar defense system.

hell, Ill just paste the whole thing here for you to read becauise typings a pain.



The People’s Republic of China will soon field a new, passive anti-aircraft
early-warning system, dubbed the PCL (Passive Coherent Location) system, which will
be capable of detecting stealth aircraft . The system tracks civilian radio- and
TV-broadcast signals, detecting aircraft by analyzing the slight distrubance in the
commercial wavelengths caused by their flight. US military and industry experts
reportedly held a secret meeting in December 1999 to discuss the potential
implications of the PRC fielding such a system.
In 1998 Lockheed Martin Mission Systems had already developed and tested a similar
system, dubbed Silent Sentry. The system had been under development for the almost
15 years, the concept might be viewed as a 'passive radar', because it uses the
reflections of the commercial FM or television broadcast signals(operating between
50 and 800 MHz) which are present in great profusion in most of the world's densely
populated areas. The Silent Sentry uses high-dynamic-range digital receivers,
phased-array antennas, powerful commercial processors from Silicon Graphics (SGI)
and software tools, the system is first initialized by cataloging the broadcast
transmitters in the region, their location and signal characteristics. The Silent
Sentry measures the Doppler shift of the reflected energy from the target, so one
way to defeat it would be to 'stand still' (stealth blimp?). The current detection
range for a 10m2 target is 180 km - soon to be extended to 220 km. Additional
growth plans include the facility for direct target-elevation measurement; the
ability to classify targets,and be able to track over 200 targets,differentiating
among those as little as 15 m apart.
Of course being passive such a system would be imprevious to conventional SEAD
tactics, and the tracked target wouldn't be aware it is tracked. (One wonders if it
was just because of the 'Propaganda problem' that TV /civilian radio broadcasting
and relay antennas where attacked in Yougoslavia, when the Chinese seemed to be so
involved, could they have been testing their PCL?)
The Silent Sentry is offered in either fixed-site or rapid-deployment
non-militarized versions. In the mobile configuration, three illuminators are
employed, providing 2-D real-time tracking, and 3-D visualization during subsequent
analysis.On option is a cooperative illuminator whose signals look like those of a
standard FM transmitter in order to improve accuracy or provide redundancy. The
system is also relatively cheap at $3 to $5 million per system.

Sorry about the size link because i had to type it all! very interesting point that it can be defeated by slow moving blimps...better make them visual and acoustical stealth too for that matter!

It's sort of similar to a multistatic setup.

We proposed a 'picket fence' something similar to this once. A chirped transmitter pointing up in a cone and triangles of receivers around it to track the Doppler.

There are easier ways to spot a low-observable. Well, more straightforward. The PCL is not something you can put in a fighter.

Ah. What to say. This won't detect something you want to hide badly enough, blimp or no.

thanks for that one. So if its not so good does it mean there wasting their time building it? or is it mainly for non stealthy craft ie f-18 / 16's ect ect? and the raptor and f-117 can still be assured of an easier time over head?

It's good against type I Ufimtsev stealth with ferrite or graded dielectric RAM, which covers most new adopters of low observable technology.

The latest low-observable tech is two major generations past that, going for 3. Radar has improved too. AESA can "burn through" type I at a reasonable engagement range, and there is a totally new fighter radar technology that can just frickin' detect anything, but it's not out in production fighters.

The article says that Lockmar's design start was 15 years ago, but in 1989 or thereabouts the situation changed. Probably what happened was that ol' compartmentalization - the right hand of Lockmar wasn't apprised of what the left hand of Boeing had invented. Heh.

[edit on 17-7-2006 by Tom Bedlam]

Wow guys thanks for all the info, I think Ive got my head round most of it now! Some of it being a little more advanced than what I know.

Tom Bedlam, am I right in simplifying what youre saying into "This wouldnt make a good surface for a stealth aircraft as a good aerial is very conductive and a very conductive surface reflects radar really well"? If thats true then I guess this tech isnt particularly useful for front line miliatry airships but could definately be useful for say a high altitude airship for relaying communications or battlefield observation which doesnt require stealth.

I understand your description of "passive" radar, do you think you could expand on your statement Tom that you can still hide aircraft from it? From what you say it seems that Lockheed Martin did some work in this field and then dumped the idea but the chinese have developed an operational model. What that means is that the USAF already has methods of hiding from it.

Right. Very conductive curved blimp surface = massive radar return



Sure, or even better as a civilian "floating satellite" city relay. There's a constant low-level bid process I see going on relating to these. A blimp sort of aerostat that is used to relay broadband/phone etc through a city. WiFi gone mad.



Lockmar is still apparently working on it (didn't know that). The Russians fielded something similar what, 3 years back? It also looks for random radio returns bouncing from the planes, as well as low-level radio noise emissions from the avionics.

You can do something similar with cell phone towers. We pitched maybe a dozen ways to spot type I stealth as part of an exercise once. You can, for instance, seed updrafts with conductive polymer strands ala 'chemtrails' and try to stick one or more to the craft. Or look for a reduction in background radio noise...the planes have the same problem with that as some of our subs, if you're quieter than the background, you have this "hole in the water" you can also detect. That was an idea we knew was impractical (someone else thought of it too). But there are a couple of more effective ways, like using a diffuse illuminator and using passive receivers in a grid. Type I just doesn't reflect a return to the sender. Like this Chinese system, you can pick up returns off-axis, and if you're chirping the transmit signal, you can correlate phase/frequency between receiving stations and determine a position.

There's also bistatic and multistatic rigs. It's like a big metal detector, sort of, you broadcast a static RF field, and when the plane flies between it and the receiver you get a return as the plane scatters some of the signal. Everyone knows that works, but it didn't used to be that you could get any real info from it, until someone figured out how to use SAR processors (it's sort of an inside out SAR) to image the plane, then a little more math and they had location and bearing info out of it. So you can't say bistatics are ignorable anymore, but I don't think anyone knows how to do the math trick but maybe Sandia, Northrop and Lockheed.

But to answer your question, yes.



[edit on 18-7-2006 by Tom Bedlam]