Principles of LPRL low-observable technology.
LPRL IR stealth coating technology alters the thermal emissivity of a host. Emissivity is defined as the ratio of radiant energy emitted by a body to the radiant energy emitted by a black body at the same temperature. Formally,
where e is the emissivity, and Wgray body (Wblack body) is the total radiant energy emitted by a gray body (black body) at a given temperature. Thus, an emissivity of unity corresponds to a perfect black body, while an emissivity of zero corresponds to a completely nonemissive material.
Combined Infrared and Radar Stealth
To this point, we have discussed IR stealth technology as separate from radar stealth technology. However, in the near future coatings will have to perform both functions simultaneously in order to counter the threat of dual mode missile guidance systems such as the MICA air-to-air missile that equips, among others, the Mirage 2000-5. In general, a unit’s coating will need to satisfy the requirements of the missions for which it was designed. For example, ground-support aircraft face very different threats than tanks or ships or aircraft designed with air superiority assumed, and the coatings of each will be different. Certain zones need only an IR stealth or RAM coating, while other zones require a combined IR/RAM stealth coating.
As discussed above in the brief review of stealth technologies, it is difficult to combine IR and radar stealth because current IR stealth materials are based on electrically conductive elements, which are highly reflective in the radar domain. Hence the dielectric nature of the LPRL IR stealth coatings proves advantageous for creating combined IR/RAM coatings because the active elements that provide IR stealth do not perturb the RAM characteristics. On the contrary, LPRL IR stealth coatings actually provide a modest amount of radar furtivity.
|Polarization||Incident Angle||Mean Attenuation Coefficient [dB] at given frequency|
|7.5 - 12.5 GHz||28.5 - 40.5 GHz||75 - 100 GHz|
The multilayer architecture consists of applying sequential layers of different coatings. In this approach, the outer layer typically provides
the IR stealth properties, without perturbing the RCS of the host. The inner layer is designed to reduce the RCS.
In the homogenous material the active dopants that provide IR or radar stealth are blended together in precise stoichiometric ratios that are varied depending on the application (aircraft, ship, tank, …) and/or mission. These coatings are typically much thicker than IR low observable coatings, since the wavelength in the GHz (radar) regime is longer than in the IR regime.
We note that although LPRL has developed RAM coatings, our core competency is IR stealth coatings, and tuning these coatings for RAM compatibility or to meet other mission-specific requirements. Therefore, our primary thrust in this field is to exploit our IR stealth technology in partnership with current manufacturers of RAM coatings to develop multifunction coatings.