Stealth design issues:
This depends on tasking requirements, but if we assume that the aircraft is going to go in harms way and is designed to shoot and scoot priority targets as opposed to targets of opportunity, then we can consider the following:
Electronic emission issues:
Eliminate active radar and use Low Probability Intercept (LPI) in onboard signal and sensor use. YThis generally entails the use of spread-spectrum, burst-mode or highly modulated signals with a substantially reduced peak power level. Transmission times involve detection characteristics that resemble electronic background noise in transit to the target. Any radar system would employ reduced sidelobe emissions to reduce the chances of detection during active stages.
Thermal signature issues:
Elements such as the leading edges of the wings, which become heated by air friction in flight, can be internally cooled by pumping fuel or hydraulic fluid around and through them.
Engines intakes and exhausts to be mounted above the wings, out of "sight" of heat-seeking SAM's, MANPADS, etc.
Optical illusion:
Blend lights into the lower surfaces of the aircraft in an attempt to blend the visual silhouette into the sky background.
This has been done in the past through projects such as the Compass Ghost programme.
Counter shading
Overall aircraft colour:
Scattered light from dust and clouds reflects onto an aircraft's underside. Even black aircraft below 50,000 ft will be visible due to this phenomenon. Most aircraft for that reason are painted a low visibility grey to take advantage of low light levels. Black aircraft are useful at night (hence why their missions are usually nocturnal). Another example is the pink coloured landrovers used by the British SAS. Pink is the best colour for desert conditions and is harder to identify than the typical beige or cammo coloured vehicles.
Aerodynamic effects, contrail suppression:
Some aircraft have contrail detectors built in which monitor contrail side effects, these can be countered by chemicals injected into the exhaust plumes using chlorosulphonic acids, various alcohol mixtures, etc) for suppression
Radar cross section:
depends on three main factors:
- geometric cross section
- directivity
- reflectivity
all three need to be dealt with and are complicated within themselves
Absorbent structure and design:
eg, laminated rubber
GRP composite layer
honeycombing
lossy impregnation of foam
conformal shaping
plastic laminates
frequency-selective surfaces
reflector films
Combining these structures with thermal infrared and visual camouflage properties results in an increased low observability.
The airframe, shape of the plane has a considerable impact on the design, but the issue of noise and vibration also has to be attended to to end up with a complete solution
Stealth design has to be a complete solution, dealing with just the RCS will work against ground based sweepers, missile systems, and interceptor radars, but the RCS is frontal only.
That means that Stealth can be tracked by a sophisticated AWAC's (especially if it knows the relative flight corridor). Systems such as Australias JORN OTH radar system can spot stealth platforms.
I actually believe that stealth aircraft are at the other end of the life cycle now. The US was using stealth aircraft for approx 8 years before they were released into the public. That would indicate to me that although stealth is an obvious force multiplier in the majority of theatre, the US has come up with other solutions in its place.
One of the things that the US has done consistently well is to build leading edge aircraft, and be a generation ahead of the nearest competitor (eg A12, SR71, U2, TRS2, F117, B2 etc...)
If they have started to develop technologies elsewhere and not around a stealth focussed solution, then that would indicate to me that they already know how to counter stealth and are devloping new platforms.
Stealth in UCAVs/TUAVs in a network centric environment, stealthy ordinance, and C41 managed from space is going to render a lot of air forces uncompetitive.
I think stealth emphasised manned aircraft probably have another 10 years left.
Stealth on other platforms is just as complex and involves other issues to be considered at the design stage.
