This is a discussion on Stealth Ship's secret: Plastic within the Space & Defense Technology forum, part of the Global Defense & Military category; Air Forces have been getting better and better at making their planes practically invisible to radar. Now, Navies may be ...
Air Forces have been getting better and better at making their planes practically invisible to radar. Now, Navies may be starting to catch up, according to Military.com.
The site highlights "three new high-profile designs: the Visby corvette, designed by the Swedish shipbuilders Kockums, the British Type 45 Destroyer, designed by BAE Systems, and the U.S. Navy's DD(X) destroyer, under construction by Northrop Grumman."
The ships each have their own ways of escaping detection. The Visby's: plastic.
It is the largest vessel ever constructed of carbon fiber -- a super-hard, lightweight plastic that is also used in the making of race car chassis and racing yacht hulls. Specifically, the boat's surface is composed of two layers of carbon fiber filled with a Polyvinyl Chloride (PVC)-like foam, or what Kockums calls sandwich-construction carbon fiber reinforced plastic (CFRP). This composite material has been proven to reduce a ship's "signature," so that not only is it more difficult to pick up on radar, but also less vulnerable to mines and other types of electronic detection, such as infrared. Since the material is not made of steel, it also escapes detection by magnetic waves. And since the Visby, at 600 tons, is about half as light as a conventional corvette, it has quicker escape abilities. That's not even mentioning the lower maintenance costs for a ship composed of plastics as opposed to one built from steel, and the lower fuel consumption costs.
The site highlights "three new high-profile designs: the Visby corvette, designed by the Swedish shipbuilders Kockums, the British Type 45 Destroyer, designed by BAE Systems, and the U.S. Navy's DD(X) destroyer, under construction by Northrop Grumman."
Its questionable to add the DDX project to that list since absolutely nothing is known about these ships. Even naval-technology does only give information about the cancelled DD-21 project. I am not aware of even some kind of sketch of these ships.
The LCS-concept however certainly belongs to these stealth ships in actual development, esp. the General Dynamics-Design.
Other good examples are the french Lafayette-Class Frigates and the norwegian Skjold-class FAC.
In terms of underwater developments the german 212A-type SSK with its silent fuel cell-based AIP would be another example.
Plastic, composite are not radio reflective nor radar absorbent. They just let the RF go through---and the RF will bounce against the internal structures.
Which makes the radar signature even worst than using deliberately radar reflective surfaces that turn the reflections away from the emitting source.
Radar absorbency must use magnetic material, since magnetism turns EMF into electricity, or use a system of passive radar cancellation by phase offset of the radar echoes, e.g. Salisbury screen, Jaumann method. The latter is where carbon fiber is used, but not because it absorbs EMF, but it partially lets EMF through, partially reflects some EMF back.
And the point is? Patrol boats are not meant to fight against other navies but are mainly for stopping criminal activity and life saving missions.
It largely depends on the design. In the case of the Danish Flyvefisken-class multi/modular-roled patrol boat, most of the configurations were in some form of combatant. The vessels could be equipped with a rapid fire 76mm cannon, Harpoon AShM, Sea Sparrow SAMs, mine rails, etc. Also MCM vessels are frequently constructed with some form of FRP or GRP hull, this is done to both reduce the magnetic signature as well as allowing for the hull to be constructed as a single piece. Doing so avoids seams and joints which could potentially split or crack open if the hull is hit by the shockwave from an underwater explosion.
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Plastic, composite are not radio reflective nor radar absorbent. They just let the RF go through---and the RF will bounce against the internal structures.
Which makes the radar signature even worst than using deliberately radar reflective surfaces that turn the reflections away from the emitting source.
Radar absorbency must use magnetic material, since magnetism turns EMF into electricity, or use a system of passive radar cancellation by phase offset of the radar echoes, e.g. Salisbury screen, Jaumann method. The latter is where carbon fiber is used, but not because it absorbs EMF, but it partially lets EMF through, partially reflects some EMF back.
Oki-doki. But what if one using radar absorbent material in the interior. Around "machine room"(?) and /or other spaces?
There are different kinds of RAM and among those used in buildings to create for example, radar proof rooms, are foam based. The most common is ferric based, fancy word for compound that appears to be impregnated with magnetized iron fillings. Radar is a form of electromagnetism, you need a magnetic material to convert them into electricity. Physics tells you that energy cannot be created nor destroyed so what seems to be "absorbing" is actually converting radar energy into another form. Anyway, yes, underneath the surface composite material, you have to apply radar absorbency either using the system above, or by trapping the radar echoes so they don't escape. Sort of like two mirrors facing each other.
I look at the Visby and the primary RCS reduction factor does not appear to be the composite used, but by the fact that its design makes heavy use of planform alignment. This is a design strategy where you reduce diffusion of radar reflections from as many directions to as few as possible. That's like putting all the radar reflections into one direction which has to be pointed away from the emitting source. The threat radar receiver has to be lucky to be on that direction out of all the possible angles.
