So for head-on, the wingspan would be providing the figures? If I do this I get a RCS of 18.47 m^2 for a B-29 and 49.15 m^2 for the B-36. Those numbers seem a little small.
No, it is not that simple. You are calculating simple size and area, not RCS. While physical size plays a part in RCS, shape is just as important. Go back to the flat plate I mentioned before. Lets change the size to 1 meter by 1 meter, for a physical area of 1 m^2. But, the on-axis RCS at X band is about 41.4 dBsm, or about 13963 m^2.
Physical size comes into play as a larger component when you get very low in frequency, as that size may determine what is the minimum frequency that has a reasonable chance of detecting the target. And even then, it ain't that simple. There are literal books written on what we are stating in single sentences and paragraphs here.
The best we can hope for here, without re-writing said books, is the general information involved. And generalities are almost always wrong at some level, the more technical the subject the more likely generalizations are to be wrong.
I'm guessing all the military aircraft indicated are in X-band since the military would be the most likely to track such an aircraft.
Not at all. In fact I would bet that most of the military aircraft in such charts are not actually measured values, but guesstimates. Remember that most of these charts are not from military sources. The newer the aircraft, the more likely that is to be. I would bet a pretty fair quantity that no unclassified actual measurements, nothing that would show up on a forum like this, of modern examples of the F-22, F-35, B-2, B-1, etc, aircraft exist. In the public domain at best someone has modeled them, and made some assumptions of the coatings used.
And X band is not all military aircraft have to worry about. It is true that many, maybe even most, threat radars (radars that can track and shoot deadly things at you) are in X band, but far from all threats are there. Also, the radars that hand off the target to the threat radar, things like acquisition, search, EW, radars, they might not be X band (many are) but you still want to hide from them also. So you need to know how easily you can be seen in every threat band, not just one of them.
Except with stealth it seems
Higher frequencies = larger RCS unless you are actively trying to change that equation, such as with stealth. Reduced RCS is not magic, and it is not a cloaking device. It only reduces the range at which you can be detected. For military applications, if you can't see me until after I have killed you, then I might as well be invisible.
Remember what I said above, "while physical size plays a part in RCS, shape is just as important". One thing not discussed so far is coatings.
To reduce RCS you can shape the object so reflected energy goes anyplace but back towards the radar. This will reduce the monostatic RCS (but leave you vulnerable to bistatic technologies). You can also coat it with materials that are not reflective in the frequency range (wavelengths) of interest. This will also reduce the RCS in both monostatic and bistatic applications.
Take the example of a flashlight in a flat black painted room. You shine the light around and the reflections, back to the person holding the flashlight, are weak, not a lot of light comes back to the source from the flat black painted walls.
Now put a mirror in the room pointed at a 45 degree angle to the the light source. The light will reflect off the mirror, but not back towards the source, and much of it will get lost in the black painted room. Still a weak reflection, from the aspect of the person holding the light. This is a monostatic scenario. But, if someone happens to be where the light is redirected to by the mirror, the light will be bright. This is bistatic.
Now point the mirror towards the light source. The same surface, but now reflecting all the light back to the source. Bright reflection.
Now paint the mirror flat black, what happens?
The angle mirror is shape, the flat black paint on the mirror is coating. In a very rough way.
Understood. Weren't X-band radars already being used in WWII?
X band radars existed by the end of WW II, yes. However, they were still a minority. Most radars in use during WW II were S band and lower.
So a sphere with a diameter of 12" would have an optical region of 18", and that would correspond to 535.4 MHz?
If you abide by the 1.6 lambda definition, yes. For the purposes of calculating the RCS as a calibration target it is not useful as some variability will be there until you get up into the 10 wavelength area.
So running rabbits would mean the return would rapidly zip all over the place in range?
Yes, running rabbits are moving (in range) false targets / interference. Two radars tuned to about the same frequency and not synchronized (in pulse timing) would produce such false targets. If the false targets or interference are in sync, not running, then it is easier for the operator to differentiate fakes from real. Two radars that are synchronized (in pulse timing) would produce such fixed false targets.
What does ITU, IEEE and ESM (I know what NATO means) mean?
ITU = International Telecommunications Union
IEEE = Institute of Electrical and Electronic Engineers
ESM = Electronic Support Measures
T!