Thread: F-22, stuff you should know

Originally Posted by Garry

...Is RSC different from different perspectives..... like front... rear.... sides... top... botom.... other various angles? What is a radar cross section figure means? Something average of that?

Yes, it varies as a function of the incident angle, frequency, and many other factors. RCS values for any given AC are usually show on a polar plot with a set spacing, like 5 or 10 degrees. So you will have a value for a frontal aspect, a side aspect, rear, etc. They will all be different. The same applies for off-plane angles. It's only recently that we have had the computing power to do a decent job of calculating the RCS from any given angle.

RCS is an area, usually expressed in m^2 or dBsm. By definition, RCS is the measure of reflected energy back to the emitter.

The simplified formula is:
RCS=geometric cross section x reflectivity x directivity.

Originally Posted by highsea

Yes, it varies as a function of the incident angle, frequency, and many other factors. RCS values for any given AC are usually show on a polar plot with a set spacing, like 5 or 10 degrees. So you will have a value for a frontal aspect, a side aspect, rear, etc. They will all be different. The same applies for off-plane angles. It's only recently that we have had the computing power to do a decent job of calculating the RCS from any given angle.

RCS is an area, usually expressed in m^2 or dBsm. By definition, RCS is the measure of reflected energy back to the emitter.

The simplified formula is:
RCS=geometric cross section x reflectivity x directivity.

Thank you highsea!

I have one more (final) question - how about energy (frequency+amplitude)? Isn't RSC different depeding on emitted wave? If yes then is there some commonly accepted value of emited energy to make RCS values comparable?

Originally Posted by Captain Drunk

While plasma streams would increase stealthiness since they absorb radio waves rather than deflect and disperse them. Hence Plasma Stealth is a safer bet.

I just can not understand how this ionized air cloud is going to follow an aircraft which is flying at pretty good speed? I think that it is possible to cover a fixed object or even slower moving..... like tank.... or etc. But how it will be done with aircraft?

I heard one vesion - rough surfaces invoke plazma (ionized air) at high speed.... but it is hard to assume.... if you increase your traction so much then you will spend so much more energy on slower speed!!!

Last. One pilot told me that ionized clouds are seen on radars... as they radiate energy themselves.... is this a problem?

So I don't understand how it will work!

ps. So I think it may be applied to tanks/fixed object.... but it will blind the tank/fixed object while this CLOAKING is used.

Originally Posted by Garry

Thank you highsea!

I have one more (final) question - how about energy (frequency+amplitude)? Isn't RSC different depeding on emitted wave? If yes then is there some commonly accepted value of emited energy to make RCS values comparable?

RCS is the eqivalent number. You measure it and compare to another object, for example if some object reflect back the same amount as 5 squre meters steel plate (in frontal projection) - you put RCS = 5 m^2

p.s. Deafcon, If you turn the same plate so only it's side will face the radar - it will reflect very different amount of energy. Different RCS. Where did you get the idea of a constant value into your litte head?

Originally Posted by Garry

I just can not understand how this ionized air cloud is going to follow an aircraft which is flying at pretty good speed? I think that it is possible to cover a fixed object or even slower moving..... like tank.... or etc. But how it will be done with aircraft?

I heard one vesion - rough surfaces invoke plazma (ionized air) at high speed.... but it is hard to assume.... if you increase your traction so much then you will spend so much more energy on slower speed!!!

Have you seen the lightning? Is it slow?

Last. One pilot told me that ionized clouds are seen on radars... as they radiate energy themselves.... is this a problem?

So I don't understand how it will work!

ps. So I think it may be applied to tanks/fixed object.... but it will blind the tank/fixed object while this CLOAKING is used.

Simply speaking. The thing in stealth is to fiind a matherial (and/or geometry) which wave resistance is matching the environment. So in radio-wave front there is no (or as less as possible) refractions.
So to the wave - stealth object would look as a as transparrent obstacle of infinite depth. Have you seen for example a clean cube of ice in water?

The same thing with plasma. Theoretically you can match the plasma frequency so it's active impedance will match the wave impendace of the air.
And you don't NEED a high power to absorb the wave, since amount of energy that reached the aircraft is already very little.