Having seen the discussions here, I have concluded that this 'plasma stealth' pretty nonsense
I just really question those
canards on the J-20.
How are they going to keep the plane 'stealthy'?
Just to be clear to the readers...I have never said that canards will
DEFINITIVELY be a negative factor in RCS controls. But what I have repeatedly said was that canards make prediction and modeling of reflected and diffracted radar signals extremely difficult and that difficulty can raise the aircraft above an unacceptable threshold to qualify the aircraft as 'stealth'. This sentiment is common among radar specialists because we know that the greater the number of reflection and diffraction generators on a complex body, the greater the odds of radar detection. Flight control surfaces are radar reflection and diffraction generators but they are necessary for flight so we cannot eliminate them, we can only minimize the number of them and shape them as best we can. Same for engine exhaust. Weapons are also radar reflection and diffraction generators but we can enclose them, either by putting them inside the fuselage or 'pod' them like how the F-15 Silent Eagle does.
As far as this 'plasma stealth' goes...
What happens is people, on purpose of unwittingly, gave the impression that the aircraft is enveloped in a cloud of plasma like how the Space Shuttle is during atmospheric reentry. The problem of this vision is obvious: how to localize this plasma cloud. For the Space Shuttle, eventually the plasma cloud disappear. For this version of 'plasma stealth' we cannot afford that loss.
First set of keyword search: 'earth atmosphere layers plasma'
Ionosphere - Wikipedia, the free encyclopedia
This portion of the atmosphere is ionized and contains a plasma which is referred to as the ionosphere.
Second set of keyword search: 'radio atmosphere layers propagation'
Radio propagation - Wikipedia, the free encyclopedia
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere.
We know the behaviors of radio signals, which is the same thing as radar signals, upon layers of plasma. Sometimes the plasma field will absorb the signals. Sometimes the plasma field will reflect which is how radio communication over the horizon is possible via bouncing off the layers.
Most people have the misconception that metal reflects radar signals but as we have seen with radio propagation via atmospheric plasma layers, a plasma cloud can give the aircraft away as well if it is tuned to the incorrect frequency. The radar signals, instead of being absorbed by the plasma cloud, they are reflected as if they impacted a solid body. Add this to the problem of generating and sustaining a plasma cloud at several hundreds km/hr or even supersonic, we can see that the cloud version of 'plasma stealth' is quite fanciful.
Third set of keyword search: 'frequency selective surfaces' or FSS.
The formulation and distribution of the ferrite particles for military use are understandably secret, but the essence is still the same: that most of the radar signals are absorbed, bounced around the particles, and in the process are converted into heat. Only a very small percentage of the signals is reflected off the surface and that is unavoidable at this time. Much more complex FSS are Dallenbach and/or Salisbury layerings that are common in radome manufacturing but the ones for 'stealth' are also secret.
Fourth set of keyword search: 'plasma antenna'
Plasma antenna - Wikipedia, the free encyclopedia
In an ionized gas plasma antenna, a gas is ionized to create a plasma. Unlike gasses, plasmas have very high electrical conductivity so it is possible for radio frequency signals to travel through them so that they act as a driven element (such as a dipole antenna) to radiate radio waves, or to receive them. Alternatively the plasma can be used as a reflector or a lens to guide and focus radio waves from another source.
A plasma antenna is a solid construct that contains ionized gas and that exploits the behaviors of a plasma field to either transmit or receive radio signals.
Wireless at the speed of plasma - tech - 13 December 2010 - New Scientist
PSiAN consists of thousands of diodes on a silicon chip. When activated, each diode generates a cloud of electrons - the plasma - about 0.1 millimetres across. At a high enough electron density, each cloud reflects high-frequency radio waves like a mirror. By selectively activating diodes, the shape of the reflecting area can be changed to focus and steer a beam of radio waves. This "beam-forming" capability makes the antennas crucial to ultrafast wireless applications, because they can focus a stream of high-frequency radio waves that would quickly dissipate using normal antennas.
Fifth set of keyword search: 'plasma frequency selective surfaces'
Finally...The combination of the plasma antenna and frequency selective surfaces where instead of ferrite particles we substitute in tiny plasma generating diodes and we have a more realistic vision of 'plasma stealth' than that silly traveling cloud. I am not going to be unfair to the lay readers by posting bits from paywalled sources even though the search results will return mostly paywalled sources about plasma FSS. The point here is that these are credible third party technical sources where the contents are vetted before publication.
The problems for plasma FSS are enormous for military applications. They are no longer proofs-of-concepts because the concepts are proven in the laboratories in every major technically advanced enough countries. The problems are engineering because engineers are the ones who must create a working solution from competing materials and environments. Other problems are power generation and materials that are robust enough to withstand varying environmental stresses in aviation. If it was possible when the F-22 was developed, we would have it on the aircraft. However, that does not mean the US is ignorant of the idea and its problems. We may have something else better and am not going to get into that.
This leave the most practical application for 'plasma stealth' to be crucial placements of plasma antennas on the aircraft such as by the intakes or complex leading edges to absorb as much as possible the impinging radar signals on those areas. This idea has it own problems but it is more practical than the plasma cloud version.
The reason why people persists in believing the plasma cloud version of 'plasma stealth' is because it is 'sexier' than plain old ferrite based paint FSS on the F-117 and the F-22. Who wants to be like the Americans? So let us make a generational leap into science fiction and propagate the idea of the J-20 streaking across the sky enveloped in a plasma cloud that rendered the aircraft invisible to radars.
That's if you are a boy of course.
