Low Observable Nozzles/Exhausts on Stealth Aircraft

[patriotpakistan]

Low Observable Nozzles/Exhausts on Stealth Aircraft

Low Observable Nozzles/Exhaust enables a stealth aircraft to reach all aspect stealth. They are used to suppress RCS and Infrared signatures considering that tailpipes are notorious for RCS and Infrared emissions. Since there is no dedicated thread to discuss that, I will attempt to compile known information to get started. Americans apply this technology to all their stealth aircraft yet I have noticed that the Chinese, Russian, Turkish.. etc have not applied it to their stealth fighters. Whats the reason for that? Any research in progress? What is the technology behind these nozzles/exhausts? Materials? Math? Effectiveness? Updates? Discuss and feel free to add more material and research.

F-117 Nighthawk (Not nozzles but the exhuast has stealth characteristics):

Patent images (from original patent file):

B-2 Spirit:

The exhaust on the B-2 Spirit is still heavily protected and close photography of it is still prohibited due to the extremely sensitive technology (reliable source). No up close photographs are available.

 

[patriotpakistan]

F-16 LOAN (Low Observable Assymetric Nozzle) Program:

[F16.net] During late-1996, A USAF F-16C and its F100-PW-200 engine were modified by a Lockheed Martin/Pratt & Whitney team. A LOAN (Low-Observable Asymmetric Nozzle) nozzle from the JSF (Joint Strike Fighter) Program Office was fitted on the engine for ground testing in a two-day rapid prototype operation. Developed under the Joint Strike Fighter 'BAA 94-2' program to evaluate advanced, affordable technologies applicable to the JSF, the LOAN provides a significant reduction in radar cross section and infrared signature emissions from the engine, as well as the potential for reduced maintenance costs.
During tests from idle to maximum afterburner, measurements were taken of infrared images, nozzle temperatures, and nacelle inlet pressures and airflow velocities. The nozzle also has been successfully tested on the Pratt & Whitney JTDE FX650 (Joint Technology Demonstrator Engine) for the JSF program.
With the LOAN, stealth is achieved through a combination of technologies. These include geometrical shaping, an advanced cooling system, and special coatings on internal and external structures. Due to the effectiveness of the advanced cooling system, the life of the nozzle divergent flaps will be more than doubled, resulting in significant maintenance cost savings.

LOAN is applicable to both retrofit and new production aircraft. Applications of the nozzle could involve the next-generation Joint Strike Fighter, as well as the world fleet of F-16 aircraft. According to Carl McMurry, program manager of Lockheed Martin's F-16 Ejector Nozzle Integration program, "The LOAN exhaust system incorporates technologies that will make JSF more survivable and affordable, but are available now and can significantly improve fielded weapon systems such as the F-16."
Ground testing at Lockheed Martin Tactical Aircraft Systems, of the Low Observable Axisymmetric Nozzle (LOAN) was completed in November 1996. The next step in the LOAN program is a flight demonstration, which is currently in the planning stages.

YF-23 Black Widow:

 

[patriotpakistan]

F-35 JSF:

Similar to the nozzle which was tested in the F-16 LOAN program.

 

[patriotpakistan]

F-22 Raptor (Probably the most effective nozzle out there):

 

[patriotpakistan]

Soviet reasearch into low observable nozzles:

Test nozzles look similar to the ones on the YF-23 by using a flat exhaust and using ceramics extensively to cool the exhaust gases. The test exhaust was mounted on an Su-27.

Not sure why this research has not translated to the PAK-FA program

Other research on low observable nozzles/exhaust:

Possible early chinese attempt.

J-20 Mighty Dragon's nozzles look like they may have small saw tooth edges.

Japanese ATD-X's 3D Thrust Vectoring Deflectors have rudimentry saw tooth edges

AGM-129 Stealth Cruise Missile

 

[C130]

the pak-fa,j-20,j-31, just don't look stealthy to me. if they can't get the engine nozzles right what else is lacking to make a stealth plane

 

[UKBengali]

the pak-fa,j-20,j-31, just don't look stealthy to me. if they can't get the engine nozzles right what else is lacking to make a stealth plane

J-20/J-31 dont use the final production indigenous engines.

We should wait to see what they look like before making judgement.

 

[Sasquatch]

Low Observable Nozzles/Exhausts on Stealth Aircraft

Low Observable Nozzles/Exhaust enables a stealth aircraft to reach all aspect stealth. They are used to suppress RCS and Infrared signatures considering that tailpipes are notorious for RCS and Infrared emissions. Since there is no dedicated thread to discuss that, I will attempt to compile known information to get started. Americans apply this technology to all their stealth aircraft yet I have noticed that the Chinese, Russian, Turkish.. etc have not applied it to their stealth fighters. Whats the reason for that? Any research in progress? What is the technology behind these nozzles/exhausts? Materials? Math? Effectiveness? Updates? Discuss and feel free to add more material and research.

F-117 Nighthawk (Not nozzles but the exhuast has stealth characteristics):

Patent images (from original patent file):

B-2 Spirit:

The exhaust on the B-2 Spirit is still heavily protected and close photography of it is still prohibited due to the extremely sensitive technology (reliable source). No up close photographs are available.

Final engines for the J-20 aren't ready. There's a rumor that the WS-15 could have the square like nozzles like F-119.

 

[patriotpakistan]

Looks like the first prototype for the F-60 (J-31) will indeed have LOAN type nozzles. The tail, wing and stabilizer edges also look to have been cut for planform alignment (Like the F-22).