Stealth Technologies

[ysi_maniac]

Let's see Super Hornet: are square inlets intended to reduce RCS or to improve eficiency?

If I plan to make a F-15XX that is said that would have some stealth characteristics, which part of the airframe deserve more attention? which mods are best worth?:

Romboid inlets
recontoured nose
no frame canopy
internal weapons
exhaust nozzles

I would like some discussion in the mods that reduce RCS the most. I mean in this public modeler's level. I not need specific data that could damage any national security

Thanks

[Supertom]

Hey Carlos,

All of the above  

But seriously, one way to do it would be to resurface certain areas of the aircraft that might be at a perpendicular angle to the ground.  In the case of the F-15, the air intakes would be rhomboid.  The tailplanes will need to be canted inward or outward.  The canopy will be reprofiled so from the front, it has more of a triangular profile than a round profile.  The idea is that you don't want radar waves bouncing back at you, but rather away from the source.

Don't forget that you could also replace a large number of the aircraft's skin with radar-absorbent materials (RAM), so you won't get a fully stealthy aircraft, but at the very least a significantly reduced RCS.

I read somewhere that exhaust nozzles are the hardest thing to "stealthify" because the carbon deposits from exhaust are natural radar reflectors.  

Evan might have some better ideas (or even correct my factoids)

[ysi_maniac]

Thanks Tom.

Waiting for more contributions  

[Hobbes]

Not having inside information, I'll go ahead and speculate anyway.
You want to prevent radar beams from returning the way they came. Circular/oval contours are bad, because they always present one point where radar is reflected to its origin. That explains the shape of the nose and intakes on the F-22.
The canopy is a relatively large source of returns, so do a new one. Doing a frameless one may help, but it also needs a coating (gold, green, whatever).
Internal weapons are nice, but with careful design (see e.g. Storm Shadow) may not be necessary. Doing internal weapons on the F-15 would complicate things to the point where you've got an all-new airframe.
The exhausts aren't critical for radar stealth. You're mostly concerned with the frontal aspect: by the time the enemy radar's looking at your back, something will have gone 'boom' and your presence is no longer a secret anyway.  

[jcf]

Something to remember about the internal weapons carriage, its really designed for the opening or 'surprise' stages of a conflict. Once the balloon goes up sneaky isn't quite as important. The JSF for example is designed to carry loads of external ordnance.
'Stealthy' containers for SDBs or in armament bays on redesigned conformal fuel tanks would both be possibilities. Evidently they was some thought given to adding weapons capability to the original F-15 FAST packs, it was mentioned relatively recently over on the Secret Projects board.

Cheers, Jon

[ysi_maniac]

You guys know a lot more than me    

[Jeffry Fontaine]

Mating a one piece canopy from an F-16 to your F-15 might be one of the quickest modifications to create your stealth F-15.  Hacking up the intakes to create a different shape cross section will definitely be a challenge.  Aside from using several kilograms of body putty and sheet plastic to rebuild your Eagle to what was suggested, you might be better off with taking the minimalist approach and go with the things that are easy to change such as the canopy.  

Good luck!  

[gooberliberation]

'Stealthy' containers for SDBs or in armament bays on redesigned conformal fuel tanks would both be possibilities. Evidently they was some thought given to adding weapons capability to the original F-15 FAST packs, it was mentioned relatively recently over on the Secret Projects board.

Cheers, Jon

Perhaps start with the normal CFTs, and cut internal bays into them and putty the rest so theyd be stealth-ey looking. I can't see any way to make a ventral weapons bay, but you would have the added advantage of being able to face an opening bay away from someone's radar. Mabye the most economical way to get an F-15XX would be to kitbash a Strike Eagle with a YF/F-22. For sure the cockpit would have to be replaced and new flight surfaces and intakes would be preferred.

[B777LR]

Some time ago, when israel was thinking of adding conformal tanks to the F-15s, somneone proposed rewinging them with F-22 wings

[GTX]

Another option is to use stealthy external weapons pods as was proposed with the FB-22:



Kind of like a modern revisit of the Vickers Wellesley:



Regards,

Greg

[HOG]

Excuse please
What is RCS and why?

Gary  

[GTX]

RCS = Radar Cross Section.  Essentially it is the key measure used to determine an object's ability to be 'seen' by a radar.  See here for a more detailed explanation.

Regards,

Greg

[ysi_maniac]

More info
http://www.whatifmodelers.com/forum//index...c=11348&hl=wing

[Shasper]

Carlos, you could always use a semi-conformal weapons mounting arrangement like the pallet that MDD proposed for the F-4s, or some sort of mounting arrangement like on the F-16XL to cut down on RCS without having to resort to using a internal weapons carriage system.


Just a thought mate

Shas B)

[elmayerle]

But seriously, one way to do it would be to resurface certain areas of the aircraft that might be at a perpendicular angle to the ground.  In the case of the F-15, the air intakes would be rhomboid.  The tailplanes will need to be canted inward or outward.  The canopy will be reprofiled so from the front, it has more of a triangular profile than a round profile.  The idea is that you don't want radar waves bouncing back at you, but rather away from the source.

Don't forget that you could also replace a large number of the aircraft's skin with radar-absorbent materials (RAM), so you won't get a fully stealthy aircraft, but at the very least a significantly reduced RCS.

I read somewhere that exhaust nozzles are the hardest thing to "stealthify" because the carbon deposits from exhaust are natural radar reflectors.  

Evan might have some better ideas (or even correct my factoids)

Supertom covers a lot of areas that are valid.

Further, yes, I do have a few ideas.  The pics I've seen of the most advanced F-15 derivatives have a wing that looks like a blend of the F-15 and YF/F-22 wing, particularly with regard to frontal angles.  The rhomboid inlets are definitely more LO than the 2-D ones on the present F-15, though you'll likely need some material changes on the inlet ducts (adding RAM, preferably, for durability, as part of composite inlet ducts); the F-35 style inlets are lower yet, but would be much more difficult to retrofit to the F-15.  The exhaust nozzles are as difficult as one might think, there are materials and finishes, such as used on the LOAN testbed as well as certain nozzle detail changes (again, see the LOAN testbed, as well as the JSF/F-35 nozzles) that can reduce RCS.  Overall, you want to eliminate, as much as possible, external intakes and/or vents that increase RCS.

As for weapons carriage, internal carriage is feasible for new designs for those phases of a conflict where LO is at a premium; beyond that, external carriage allows more and the F-35 has three hardpoints under each wing (outboard-most on each side being for an AAM, only).  Careful attention to pylon design and stores integration can still help reduce the RCS of a fully armed-up aircraft (I've seen drawings of stores pylons studied for the B-2).

HTH,
Evan