“Stealth ship vs stealth fighter” comparison is way too generalised. If you take Fridjof Nansen for example, the ship has no point defense, only 8 surface to air missiles and two fire control radars to guide them.
Theoratically, a pair of (non-stealthy) F-18Es, both carrying 4x harpoons and a jammer pod, can sink it without much difficulty, and live to tell about it.
This statement requires a bit of elaboration, at least to me. How can a part that is invisible from a certain angle affect the RCS value??
However general consensus is right, you cannot just assume how affects RCS by using eyeball. With appropirate continuity (which PAK-FA has by using very large composite panels) and correct RAM application (which PAK FA will certainly have in serial version) it may virtually be non-existant.
Did they?
Yes, like others said it was petr ufimtsev’s works that allowed the calculation of radar wave returns. Even LM admitted they used Petr Ufimtsev’s theories for designing Have blue, which lead to F-117. Unfortunately, skunk works didnt (or couldn’t) develop the knowledge further to calculate curved surfaces, and computer power were not sufficient to iterate by using flat surface formulae. Thats why F-117 had such a faceted shape, which possibly put a smile on Soviet physicists’ faces.:) With US understanding of the theory developed, no other LO design had such faceted face. (I think this single historic event alone shows why “if it doesnt look like X-XX it isn’t stealth” idea sounds more than idiotic.)
What low observable “things” did the Soviets design and manufacture?:confused:
Does Kh-101 missile count? Its a stealthy reshaped version of Kh-55.
Soviets never designed a military equipment solely on LO shaping, but there are clear traits that they benefited from it. Like others stated Tu-160 and upgraded Su-25 MiG-29 and Su-27s have RAM. On Kirov class cruisers, every wall on the superstructure is angled:
Intitute of Theroratical and Applied Electromagnetics has a self-built RCS prediction software and testing grounds. Here is an image from RCS testing ground, although may not be from Soviet times.
With its wings fully deployed and folding mechanism removed, IMHO, it would make an excellent Close air support aircraft. 4 non-afterburning engines would provide excellent thrust and survivability. By using a very thick airfoil on wings -which would be optimized for slower speeds- can provide excellent turn performance, payload and fuel capacity.
However if you are looking for a high supersonic interceptor, it wont work for many obvious reasons. IMHO, instead of drawing a design first, you should make your design goals, learn fundementals (not engineerings but reasons why some designs are well-recieved but others abandoned) and let the form follow it. Lets go to the boring part:
1- Shock geometry: If you want to draw something that goes fast, you should take a look at your shock angles first. Obviously this will be near useless on 3d analysis, but should give an idea about it. For example, your nose to wingtip angle is around ~32deg which will translate to around Mach 1,9. This will be your approximate top speed unless you have plenty of fuel to waste in order to go above it (which your design doesnt have). Also your wing leading edge shock cone translates to M1.15. Without using any mechanisms to move the shock away from the wings, it would also hinder supersonic acceleration. While talking about shockwaves, note that XB-70 has a very long fineness ratio that prevents folded verticals to be caught in the supersonic shock wave created by the aircraft’s nose.
2- Area ruling: For anything that moves fast enough to compress air in front of it, (general assumption in fluid dynamics is speeds above M0.85) area ruling becomes very important. Area ruling dictates shape of the aircraft is not important, as long as cross sectional areas of the design follow the lines of Sears haack body.
For example in F-5 below, note that body goes thinner as the wingspan reaches its max, in order to “balance” the extra cross sectional area added by wings. These area ruling is present on any transonic/supersonic aircraft since 1950s, but is better blended and less evident.
3- Engines: Number of engines must always follow your design needs. Do with the smallest # you can. For 99% of the time, one big engine with same thrust as two smaller engines will always provide better economy. Other than that, there is so much to say I think a numerical comparison should be more clearer:
4x F-404 in total will weigh 4,2 tons. Each engine will require its own individual inlet; If you want your plane to go M2.5+, you will have to go for a multi oblique shock inlet. You would love a 5 shock design but there is no point in putting an inlet that weighs more than these little engines behind them. Not to mention there will also be size constraints. Your plane will need four individual hydrolic systems to move these inlets, and individual sensors and ICS computers to control them. It will need extra structure to hold each engine and all the components i’ve mentioned. All this means weight; possibly measured in 3-4 ton range. When combined, those engines will have 195 kN dry 315 kN reheated (static) thrust, and have SFC of 82,6 kg/kN.h dry and 177,5 kg/kN.h reheated.
Imagine this; 1x NK-25s from Tu-22M will weigh 3,4 tons. It will require a single inlet, which can be better optimized for efficient supersonic operation (as there would be less weight and dimension constraints). It will be easily embedded into body, requiring a lot lighter structure and reduce the frontal area (and drag) by ~60%. As it will only need single hydrolic and ICS, overall system will possibly weight (a lot) less than 50% of the 4 engined design, while providing 137 kN dry 245,2 kN reheated (static) thrust, and have SFC of 73,6 kg/kN.h dry and 170 kg/kN.h reheated. Also, by removing 4x engine pods and switching to one engine embedded in a streamlined body will improve area ruling considerably. With 3-4 tons reduction in weight and drasdic improvements in shaping, this single engine layout would go faster even it has 23% less thrust than the 4 engined one, while providing better fuel economy both due to lower SFC and lower drag.
4- Going high supersonic always require large amounts of fuel. MiG-31, for example, carry 19,9+ tons of fuel. Density of fuel can be found easily by googling; make sure you have internal volume to pack some fuel, or -like others said- your plane wont make 200 miles.
About wing and tail design: You have to understand concepts of turning, stable/relaxed stable aircraft and how elevators work: Its always the lift created by wings itself that makes the turn. Before stalling, lift is directly proportional to the AOA. Elevators merely change the AOA of the airplane; lift vector pulls the aircraft to the center of the turn circle. For example an aircraft pulling 9Gs is creating 9 times lift force as its weight. Now stability: On a stable plane like F-15, lift vector is behind the center of gravity, so if unattended, extra weight at the front will decrease AOA, and by doing so decrease the lift vector, returning the aircraft to minimal AOA state (hence stable). On stable designs, elevators make a downward force to maintain the AOA state. On unstable designs like F-16, lift vector is in front of the CoG, and inertia of the plane continiously tries to increase AOA. If unattended, this will also increase lift, which futher increases AOA by a feedback loop, likely ends up in breaking the airframe (hence unstable). On these designs, elevators create a downward force to increase AOA to desired angle first, than try to stabilize the aircraft by creating upward force.(hence relaxed stable) This allows very quick AOA response, and elevators’ upward force contributes to lift, so aircraft makes a quicker and more energy efficient turn.
Now going back to your design. First, size and position of elevator depends on your design’s stability and angular inertia. Ideally, you will want a neutral stable aircraft with zero angular inertia and miniature elevators. But real life is different than ideal, so you have to estimate your aircraft’s physical charactheristics. If you have an inteceptor in mind, it shouldn’t need huge elevators. It shouldnt even have the ability to turn hard, otherwise you are wasting weight/space on useless areas that should better be spend on fuel capacity.
Most important of all, redirecting engine thrust is pretty useless for an high speed interceptor. With high speed air flowing above elevators, even slightest change of 3-4 degrees will create a very large force. In such that deflecting it to its max will be impossible because hydrolics wont be able to. If hydrolics could, such deflection would break elevator itself. If it doesnt break, such large AOA correction will destroy the airframe in an instant. Its THAT big of a force and will make engine thrust laughable.
I tried to make it simple best I can, hope it helps:D
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