Of course it allows curves! It's just that they can't have curvature less than a great circle....~
Due to the way the military produces software specifications, it is very likely that the unbroken chain of subject-matter-experts from the days of ochre pictograms on cave walls to today have ensured that the software program functions exactly the same as drawing lines on charts by hand.
Since human navigators did not initially possess the capability to continuously recalculate courses, bearings, and headings, as would be required in a curved flight path, the ground-based and flight computers don't do it now. So planes still keep a fixed heading between a set of points, and any possible roundness is encoded into the turn data or a specialized, predefined pattern.
I was speaking of the angles in the shape of the planes design.
Have you ever seen a diffraction pattern caused by any discontinuities?
I have seen thousands of them ... the fourier transform of any discrete functions makes very nice detectable pattern that says : "NOT NATURAL". And that what radars are trained for spotting.
And the more symmetries the more the pattern reinforce itself saying: human made technology spotted. (Curie principle : symmetry in causes get propagated in the effects)
Have you seen a lot of natural object that are both discontinuous and symmetric and the size of a plane?
EDIT : I forgot to explain the relationship between convolution of signals and FT but I guess everyone is educated enough to know that convolution of signal is the base of radar detection and that Fourier transform are related to convolution.
Oh.... I thought you were talking about curves in the routes programmed into the flight computer!
AFAIK, stealth planes use all flat surfaces and no curves because a curved surface is more likely to reflect a signal from an active radar beam back in the direction of the detector instead of somewhere else.
If you shine a flashlight beam on a reflective sphere, you will always see a tiny spot of reflected light somewhere on the surface. If you shine a light beam on a perfectly flat surface, and it is not angled correctly, you will not see the reflection.
So stealth surfaces are designed to be as black (to radar frequencies) as possible, and as flat as possible. And if possible, you should make as many of your flat surfaces parallel to one another as you can manage, because each one sends a reflection of a radar beam to a new spot, and you don't want the spots to be widely dispersed.
In order to classify a radar reflection as natural or artificial, you have to detect it first.
Detection is always a business decision between true/false positive/negative, the costs of sensitivity that is non linear per stage (breakthrough are non predictable) and the costs of stealth.
And since science have improved at increasing detection by using distributed measures coupled with active correction the detection is getting easier and cheaper.
There is a pace at which technology are cheap and efficient. And money (especially when GPB is not growing) is really the nerve of war. Technologies should be used opportunistically according to their costs that can change faster than the design/delivery process.
The blindness on the cost efficiency and long term bets is taxing a lot the normal economy that in turns slow down and has difficulties feeding back military with useful cheap innovative realiable real innovations. We cannot predict the future. Especially when it comes to innovation.
And look: we rely on the best of our technology to build weapons, but these technologies don't seem to deliver.
Maybe the F35 story is an allegory of how our economies are in bad shape. And maybe the greatest military decision would be to diminish the defense/NASA budgets and fix the market and society.
PS I insist that these software problems are not unique to USA. Rafale, A400M, Typhoon, probably russian planes have been suffering "outstanding delays" & "budget slip" and software are often involved.
I do not think this is only a military problem. Something is rotten in the R&D department. Maybe the way we organize ourselves.
Remember with turbine powered bombers the flight takes 5 hours crossing the aerial zone of at least 5 NATO countries with modern aircraft and radars. And we know it was loaded with nuclear weapons, because of radioactivity.
In fact, maybe the paradigm of airplanes is outdated since USSR giving cheap missiles and crude radar to the viet kong have proven that in terms of costs planes can be shot down with a 1/100 ratio in terms of costs. Plus aerian superiority paradigm (a WWII idea) works against developed countries relying on a dense industrial country. But, it does not work against people relying on AK47 and propane bottles coupled with a simple radio system.
Money is the nerve of war.
Angles: Sorry I can't find the article explaining how the DOD imposed using a software for B2 (and not F35) that limited the possibility to make nice curbs.
However just look at the plane. And remember any physics lessons you have been taught : sharp angles make discontinuities. Discontinuities are easy to spot.
Stealth anyway is a scam.
B2 were spotted by US radars technologies bought by french since 1991 with networked radar (thomson). Validated during 1st iraki war while radar operator could put a name on the weired stuff they were seeing on screen they already saw flying over European space without authorization. (Spying allies is really not nice)
You can evade one radar by deflecting signal. But if in a network of radar the signal is reintercepted, then it is bad for the plane.
Also since 2000 it has been proven that the flight of a stealth plane above a normal "cellular phone grid" can be detected by the additional energy that it bounces back.
Still with networked radar, stealth planes can make "holes" of expected energy. (ionosphere does reflect a little part of energy, and stealth fighter makes "shadows/holes") it may require bigger wavelength though.
With IR detection, plane still leaves energy traces (like air friction).
Stealthiness only value is in plane vs plane fight to diminish the electronic signature, thus a frontal stealth is more than enough.
Stealth is a costly arm race. That is exactly what killed USSR that tried to fight USA IDS program (that was a scam).
Strategic thinking must address the costs problems.
Your BBC link says fighters were scrambled to approach the bomber that did not enter sovereign airspace. I'm not sure what your argument is.
I would say it's always been cheaper to shoot down an airplane than to build, use, and maintain it. That's nothing new.
I don't recall anyone ever claiming that stealth would make the planes undetectable, only harder to detect. You do realize that what we know as stealth technology today was developed 30 to 50 years ago? I would assume new technologies have been developed to defeat it. Even accidentally, such as your cell phone grid example; which did not exist when the stealth technology was developed. Doesn't mean it has always been a scam. Today's planes are "stealth-like" which means they have similar technologies but no one expects them to disappear into the night.
As for the cost, I agree. This trend of bigger, better, and more expensive is stupid.
And I cannot find the UK articles from 1 year ago saying the exact problem with typhoon and why UK wanted to replace them with F35. I remembered something about costs, availability attrition and budget. Like typhoon were to expensive and that 24/7 battle readiness was kind of a joke given the budget.
I was in the french navy for my conscription. The aeronaval would have preferred F16 over rafale ~2000 for exactly this:
1 rafale = 10 F16 (at the time) and OPEX of rafale >> F16.
And they could have had another diesel carrier thus france could have had a fully usable aeronaval task force for the same price.
Anyway: cellular grids where not that developed yet, but efficient distributed radar were. And every "refinment" is kind of another order of magnitude in the equation. Harder to measure, harder to counter, harder to build but it can be anticipated : every generations are almost an order of magnitude more expensive.
Can you see a pattern? Stealth like aircraft (Typhoon, Rafale, F35, F22) are hard to sell because they cost a lot due to complexity (in software notably). Thus government HAVE to subsidize them ...
Thus, people try to make them polyvalent BY DESIGN (waterfall model) and like any jack of all trades they tend to master none of them and inflates OPEX and KPEX with erosion of the benefits and a LONG development time that make them likely to be obsolete when delivered.
A lot can be said on the history of aircraft industry. I dare say we lost the art of being smart that requires some fast feedback loops (agile but correctly done) with minimal correct design (waterfall but correctly done) and cost efficiency.
That is the difference between the spitfire and the Me109.
Can a general purpose warbird be built during peace time?
I do not think so. They are like hammers built without knowing which nail will need to be hammered or may be screwed.
But simple cells (F4, mirage, F16) with awesome lines (ok, I am found of nice looking planes so it is not serious) that can sustain modifications (like the spitfire) have proven to be good planes ... on the long run when you have good workers, engineers, (tests) pilots, industrial able to make them evolve in a reasonable time and price constraint.
The quality of out warplanes reflect the actual problem with our civil economy : Quality and costs do not matter when industries relies on finance and not production for making benefits.
It does come off as a wasteful arms race but I think it's a bit much to call it totally useless due to theoretical weaknesses and occasional spotting. You clearly are more involved in this area so can probably answer, "Did they track the planes the whole mission or just get a glimpse of them on the way with long-range radar?" If the former, your claim is right and they're blown out of the sky by any non-3rd world country. If the latter, then they lack a full element of surprise but otherwise hit a local target with little opportunity to react.
Anti-stealth tech being sold by Russia, etc might change the situation with wide deployment if they're effective and quick response. Otherwise, it would seem stealth is still useful for hit and run attacks on key targets with less risk than easy to track and lock aircraft.
Are you suggesting that the UK totally ditched all of their current interceptors and have their pilots sitting around waiting for the F-35 to show up?
Are you saying the existing stealth planes are a money-making scam because we all know they built them wrong?
The software doesn't allow... "curves"? Why doesn't it allow curves?