Stealth and Tejas

[sancho]

The best DRDO can do is to reduce its RCS by making use of radar absorbent structures (RAS)

That's already included today, since a low RCS was a development and design aim from the start, however, as soon as you add external loads, the RCS will go up, so that is the main area to where you can reduce the RCS. That's the reason why the difference between the normal F18SH and the Silent Hornet is, replacing external fuel tanks with CFTs and external weapons with carrying them (except of the IR missiles) in the weapon pod.

 

[S-DUCT]

That's already included today, since a low RCS was a development and design aim from the start, however, as soon as you add external loads, the RCS will go up, so that is the main area to where you can reduce the RCS. That's the reason why the difference between the normal F18SH and the Silent Hornet is, replacing external fuel tanks with CFTs and external weapons with carrying them (except of the IR missiles) in the weapon pod.

Tejas still utilises older generations of RAM.
For the crucial frequency specific 8-12 GHz (X-band) range,it gives an whooping 19.2dB absorption, the 3mm layer is essentially 3 x 1mm (or 2x 1.5mm) layers. As per breakdown in the table above, would give -6.4dB per 1 mm. So 2 layers of 3mm (i.e.6 layers equating to 6mm) will yield an absorption coefficient of around -35dB (6mm x -6.4dB).It's an amazing result!.

RAM being developed for PAK-FA gives absorption coefficient of 30db for 6mm(2*3mm) thickness.

You can still apply latest generation of RAM on LCA to reduce RCS further.

 

[sancho]

You can still apply latest generation of RAM on LCA to reduce RCS further.

As said, it hardly makes a difference as long as you carry external loads.

 

[S-DUCT]

As said, it hardly makes a difference as long as you carry external loads.

Okay.I wanted to point out that along with CFT and External weapons bay,we can still apply Newer RAMs to bring down RCS.

 

[BlueDot_in_Space]

Okay.I wanted to point out that along with CFT and External weapons bay,we can still apply Newer RAMs to bring down RCS.

another major improvement would be to get rid of the vertical tail and use thrust vectoring. This will save weight and further reduce RCS.

 

[S-DUCT]

another major improvement would be to get rid of the vertical tail and use thrust vectoring. This will save weight and further reduce RCS.

IMO,it will become too complicated,NASA cancelled X-44 manta program a decade ago.

 

[Hobo1]

Tejas should be able to postion itself as Gnat which severely thrashed PAF in 71 war.

 

[sancho]

Okay.I wanted to point out that along with CFT and External weapons bay,we can still apply Newer RAMs to bring down RCS.

Which it probably never get. If CFTs would be possible and required, they wouldn't go to lenghten the airframe and integrate new fuel tanks now. Weapon pods with a useful capacity might only be possible for the wings, since the centerline station of the Tejas is size limited.

 

[rashtriya.rifles]

Why are people even thinking that we can apply RAM coatings just like that ? Every Kg extra matters. Especially when the engine has less acceleration already !

 

[S-DUCT]

Why are people even thinking that we can apply RAM coatings just like that ? Every Kg extra matters. Especially when the engine has less acceleration already !

If we replace GE-414 with single AMCA 75KN/110KN engine ,then the weight issue will be resolved.
@anymember:What's the avg. density of RAM.

 

[VanDiZ]

I know that LCA was not designed with stealth in mind... but like every modern aircraft it was in the plan (design) to paint the LCA with RAM... so no weight problem...

LCA is small in size so less RCS then bigger non-stealth aircrafts.

As it is well known that CFC act as a radar EMW absorber, the heavy use of CFC in its airframe causes the farther reduction of the RCS.

So, the end result is, we cannot say that LCA is a by-design stealth aircraft but it will be wrong to say that it do not have any stealthiness.

Its not that difficult to understand... right ???

 

[Sergi]

If we replace GE-414 with single AMCA 75KN/110KN engine ,then the weight issue will be resolved.
@anymember:What's the avg. density of RAM.

What is that ??? Can you throw some light on that ???

 

[Kloitra]

If we replace GE-414 with single AMCA 75KN/110KN engine ,then the weight issue will be resolved.
@anymember:What's the avg. density of RAM.

Different materials, different densities. Pure ferrites, about 5 gm/cm^3. For neoprene based ferrites, I would guess about 3 gm/cm^3. But there are many more factors involved, like the thickness, etc to calculate the weight of RAM. Not sure if they use ferrites anymore.

Patent US3754255 - WIDE BAND FLEXIBLE WAVE ABSORBER - Google Patents

This is an age old paper. Try searching for better ones.

 

[S-DUCT]

Different materials, different densities. Pure ferrites, about 5 gm/cm^3. For neoprene based ferrites, I would guess about 3 gm/cm^3. But there are many more factors involved, like the thickness, etc to calculate the weight of RAM. Not sure if they use ferrites anymore.

Patent US3754255 - WIDE BAND FLEXIBLE WAVE ABSORBER - Google Patents

This is an age old paper. Try searching for better ones.

Generally maximum of 2 or 3 layers totaling 6-13mm of thickness can be applied without getting significant diminishing returns.
Patent US20090126783 - Use of vertical aligned carbon nanotube as a super dark absorber for pv, tpv ... - Google Patents
Though different CNT RAM will have different density,but for sake of calculation i'll assume its density as give by the above patent as .015g/cm^3 and total thickness of 6mm(two layers of 3mm).
In any case i think it will not exceed 50kg(3.5kg for area of 38.4m^2 wing area.)
@Sergi:

Check the below link.
http://drdo.gov.in/drdo/drdojsp/downloadtndr.jsp?tenderName=4083&McrId=GTRE*Gas%20Turbine%20Research%20Establishment&p=advdesidoc.pdf"]http://drdo.gov.in/drdo/drdojsp/downloadtndr.jsp?tenderName=4083&McrId=GTRE*Gas%20Turbine%20Research%20Establishment&p=advdesidoc.pdf[/URL]

 

[Kloitra]

Generally maximum of 2 or 3 layers totaling 6-13mm of thickness can be applied without getting significant diminishing returns.
Patent US20090126783 - Use of vertical aligned carbon nanotube as a super dark absorber for pv, tpv ... - Google Patents
Though different CNT RAM will have different density,but for sake of calculation i'll assume its density as give by the above patent as .015g/cm^3 and total thickness of 6mm(two layers of 3mm).
In any case i think it will not exceed 50kg(3.5kg for area of 38.4m^2 wing area.)

We would get AMCA before we get industrial production of 'vertical aligned CNT' enough to paint entire aircraft.
https://sites.google.com/site/cntcomposites/cost-and-production