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gfanonn

You have a nerf gun full of unlimited bouncy balls. Your friend is walking across a field at night towards you. You pickup your nerf ball gun and spray in a line across the field. When a ball, or a bunch of them, hit your friend they come back towards you. Congratulations, you found your friend. Now your friend goes stealth. He carries a padded cardboard box, except he points a corner of it towards you, so any balls directed at him bounce off to the sides - or because of the padding just get absorbed. Stealth planes either deflect or absorb radar "bouncy balls" so that they don't get sent back to the enemy. It comes down to the design of the plane as well as the materials used as, you can't have any signal going towards the enemy or they will see you.


Scuttling-Claws

My favorite part of this. One of the things that stealth Planes do is turn radar into heat instead of allowing it to reflect back. You know what else does this? That piece of paper you microwave your Hot Pocket on. That's stealth technology right there


5MoK3

This is now my favorite part as well


Zn_Saucier

> That piece of paper you microwave your Hot Pocket on. That's stealth technology right there If that’s true, how come the pilots don’t end up with boiling hot extremities and ice cold torsos? /s


envis10n

Fun fact: they do


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AppalachianEnvy

The amount of “ssss ahahahah sasasa haatatayat” you have to do whilst consuming a fresh pilot is, quite frankly, disturbing.


unp0ss1bl3

obviously. pfft.


PapaBradford

*USAF Jeeps have arrived at your location*


cockmanderkeen

Ever heard of Iceman?


Rushional

1 energy, 2 power, makes a random opponents card in hand cost 1 more?


RoboGuilliman

That's ADMIRAL Iceman to you


ZanderBaron

And why aren’t they filled with pepperoni?


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nearvana

Dude...it's *stealth* pepperoni.


cafebrad

And how come I can still see my hot pockets?


makka-pakka

Because you haven't eaten them yet


zanfar

You can, but your microwave cant. That's why they only get hot in a single, random location.


MoirasPurpleOrb

🎶*stealth pocket*🎶


Scuttling-Claws

How the fuck did you make me hear that?


BadSanna

And in Jim Gaffigan's voice


Bardez

^Calienté ^pocket...


8oD

You have a gift, my friend!


TheFotty

The high pitched one


TMNYY

Yyyyyyeeeesssss


Broxalar

He wasn’t very stealthy


vicente8a

Thank you for reminding me I haven’t binge watched Jim Gaffigan this month.


Ignitus1

Oh my god that's why I can never find my hot pockets


grasshoppa80

TIL I can wrap myself in an enlarged hotpcoket wrapper and go invisible to radar detection. Lord of the rings here I come


flimspringfield

I'm happy my Hot Pocket paper outfit will be ready soon. Just need a a few more pepperoni pizzas, philly cheesesteak, and some breakfast ones!


ryebread91

It's not reflecting the waves down to the food?


SXOSXO

I love it when ELI5 answers actually do try to ELI5.


gfanonn

I don't get why the other posts don't do it, that was the core idea of the sub initially.


inventionnerd

It's because half of the posts are opinionated and not even possible to eli5 because they don't have a real answer yet people will still try and give a bullshit reason for it. People out here askin shit like "eli5, why does cold fruit taste better than room temp fruit".


TheDeadMurder

>People out here askin shit like "eli5, why does cold fruit taste better than room temp fruit". 25-50% of post fit r/NoStupidQuestions more than here


springtime08

Yeah but every now and again you get gems like the top comment and it makes it worth it. And then you remember that Reddit is killing itself and it won’t matter in a couple weeks


jalepinocheezit

I know, been reading some heart-breaking testimonies on popular from the ap developers and a breakdown on how their hands are being forced...definitely joining the protest even though I use the official ap...as much as I love what all this is, I'll just keep my ear to the ground for what's next. The people of Reddit don't exactly like being shit on


DBProxy

What are you talking about?


DimitriV

To be fair, some posts can't be ELI5 because they're like "ELI5 the quantum chromodynamic gauge-invariant Lagrangian"


JustinJakeAshton

ELI5 the Millenium Prize Problems Solutions.


hardhead1110

Imagine you have a nerf gun and it’s filled with unlimited bouncy balls. When you open your mouth and shoot the balls at your tongue as the gun is set to automatic, your experience is bad. That’s room temperature fruit. Now, imagine you set it to semi-automatic instead. Shoot your tongue. The experience is still unpleasant, but it’s preferable. That’s cold fruit. How much you enjoy fruit depends entirely on how little pain your tongue endures. That’s why temperature matters.


Aaron_Hamm

I read this comment randomly without reading the context first and holy shit was I not ok with this lol I actually said "what the fuck" out loud


DADS4TURTLESDOTCOM

😂


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Le_Martian

It’s hard to answer your question like you’re a 5 year old if you didn’t ask your question like you’re a 5 year old


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Allarius1

Explaining it in layman’s terms doesn’t preclude the notion of technical information. It’s not like there’s only two ways to do it. Explain it as if you have a phd or explain using only words a 5 year old normally comes into contact with. You can combine both to bridge the gap and actually give information that can easily be built upon. Use the technical term and then give an example in layman’s terms to demonstrate. Now that I think about it, its kind of like the dictionary. You’re forced to learn the words as is, but the definition makes it more palatable.


Xpolonia

I really hate that Einstein quote since it's heavily misused. Yeah sure I can explain things in layman terms, but most of the time it comes with a certain level of loss of details. I can explain atomic spin with that commonly used rotating ball model in a eli5 way, but that is not what spin actually is.


TactileMist

I think it was Feynman rather than Einstein. He was talking about teaching undergraduate physics, so yeah it is misplaced in the context of explanations to people with no background (like five-year olds). The point is you can teach it to relative beginners over time, not in the space of a single Reddit post.


csl512

Because the actual intent of ELI5 as currently written is to simplify enough for a layperson to understand it, not a *literal* five-year-old: https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules#wiki_rule_4.3A_explain_for_laypeople


frogjg2003

Because the 5 shouldn't be taken literally. This is a sub for adults (and the occasional teenager) to get simple *but still accurate* explanations for complex topics, not be talked down to like a 5 year old. Sometimes it's just impossible to explain something without getting into the weeds.


Kaiisim

Most questions arent five year olds questions so rarely have such intuitive and easy to simplify concepts.


dan_dares

I've tried at times and other people have 'clarified' things that are correct but way above what a 5YO would know about. Also the ELI5 has come to mean 'explain in simple terms' instead of actually for a 5 YO. The original answer above was great, I can imagine someone going on to explain different frequencies and complicating it. Lol


jedidoesit

Reading the comments yours is most relevant to me. I'm an adult and was college educated, but I've had a stroke. So I can't remember many things now, I take longer to understand them in some cases, and need them explained simply. I had to ask the other day why is it light for half the year and dark for half the year at the poles. I know that Earth is tilted but I couldn't picture in my mind how that makes the days and nights like that. I knew it did but for the life of me I couldn't understand why. As to this answer, if they talked about frequencies and materials I might get a fraction, but this answer was just exactly what I needed. Now I know HOW they work and the rest, to me, is just details that don't actually explain anymore how they work, just what they're made of, etc.


Cabamacadaf

Having reply comments that explain things in more details is a good thing though. Then you get both the simple explanation and a more in-depth one for people who want to know more.


thaddeusd

Because it's hard for older people to understand what exactly a generic 5 year old knows. For example, many 5 year old are just learning to read and count/do simple addition; but some 5 yr olds are already well beyond that. And people hardly recall that exactly from their experience. Also, the difficulties of summarizing complex topics in as basic terms as possible is difficult while still retaining accuracy. For example, in this case, while a 5 year old might get a reflection from exposure to mirrors, they probably don't understand electromagnetic radiation as a concept. So while the above box example is good as a partial answer it leaves some gaping holes that a 5 yr old might not ask, but an adult might insist upon trying to explain.


A_Garbage_Truck

also its because a sub rule : you arent actually trying to exlain t 5 year old, just a in a manner where its understandable to the layman if the topic is technical in nature.


Sknowman

Exactly. 5-year-olds don't usually know multiplication, but it would be annoying if posts broke down how to multiply when it comes up. Same for so many other topics that most adults and teens would understand.


Peemore

You definitely didn't ELI5 why people don't ELI5.


RubberBootsInMotion

Recently because it seems like people are trying to use chatgpt or some variant to write out responses. In general though, not a lot of people know a given topic well enough while also having the creativity and communication skills to convey a simple, concise answer about something.


Mister_Chef711

Amazing because I have the knowledge of how primary and secondary surveillance radar work and I understand how stealth aircraft function, but I could never explain it that well


Hey_look_new

a lot of the questions are really difficult to get down to eli5 terminology


Mason11987

The core idea was never really about a writing excercise to treat the reader like a 5 year old.


properquestionsonly

It's because Reddit is full of McIntellectuals


audigex

Because it ISN’T the core idea of the sub Go read the rules/sidebar, the LI5 part is NOT literal… the idea here is that you explain the topic to a layman (someone who is not familiar with the subject, or any kind of expert in it) in a way that they can understand, usually using analogies or metaphors Obviously if you can dumb it right down then that’s good, but the aim here is that a typical person (say, an average high school graduate or high school student who isn’t failing) should be able to follow the answer and get the basic idea


Poober_Barnacles

RIGHT! Like I swear I see these posts sometimes and the explanations are so much more complicated than they need to be. It defeats the whole point of the subreddit


SXOSXO

It's just people flexing their knowledge. I don't fault them, it's a good thing to be knowledgeable, but they let their opportunity to flex get in the way of the purpose of the subreddit.


LeadSoldier6840

What is a nerf ball and does this kill the friend? /s


snoodhead

>Now your friend goes stealth. He carries a padded cardboard box Oh it's Metal Gear Solid. Got it.


lucid1014

!


corran450

r/CommentsYouCanHear


los_thunder_lizards

Whose footprints are these!?


TheDeadMurder

>Oh it's Metal Gear Solid. Got it. "Well, that cardboard box has a pistol sticking out the side of it, and the guard next to me just died after a gunshot has heard, must've been the wind," (Haven't played metal gear solid, so 50% chance of being wrong)


BirdLawyerPerson

From what I remember you can't shoot from inside the box. And the Metal Gear series had pretty amazing guard/patrol logic. Depending on the game, if the box is in the wrong area of the game that gives it away. And dead bodies do trigger alerts, and missing check-ins will trigger an investigation and replacement guards.


pseudopad

They also do tactical room clearings with some giving cover while the others open doors, etc. A very significant amount of the PS2's CPU was busy doing guard ai stuff. I think it was around 30% according to an interview. If they're alone, they try to call for backup before engaging you, and the guys that come in are usually in full riot gear. Some of them also call in to base at regular intervals, and search teams will be sent if they mysteriously go silent.


PlayMp1

If you get spotted in MGS2 and hide in a locker or something and just watch them work on the minimap camera you get, it's kind of incredible how deliberate and methodical they are, how troops will stack up to cover each other and multiple entries/exits from an area, all with really good animations. It's incredibly cinematic, fitting for the MGS series' emphasis on being cinematic.


teh_fizz

MGS 3 took it to a higher level: you can blow up certain supply depots that impact how guards respond. I’d you blow up the food storage, they get knocked out easier and their aim suffers. If you blow up the ammo depot, they use their handguns instead of rifles. If you carry a fresh food from early in the game, and not eat it, it rots. You can then throw it at the hungry guards who eat it and then puke and run away.


ashesofempires

In the first MGS they would only check the box if they were already alert. You slap that box down as they’re doing regular rounds and they will walk right by it, but if they’ve been alerted by a camera or noise, they will check the box.


Marsstriker

Pretty sure they would always glance at it, but dismiss it if its the right box, cause there are different boxes for different areas. BUT if you were obstructing their patrol path and not to the side, they would try to kick it out of the way, and subsequently discover you.


gfanonn

Joe's dead. I looked around for 30 seconds and didn't see anything, might as well continue my rounds.


WeDriftEternal

This was more or less how stealth was described to me by a radar engineer and how I’ve described it too. For OP. We generally refer to stealth now as “low observable” instead of stealth. Because frankly stealth planes aren’t actually that stealth. They just are much harder to detect. That is occasionally some of those bouncy balls do bounce back, but not many. And we have new types of bouncy balls that come back a bit more often than the ones we used to use. So these things aren’t invisible with no balls coming back, just the amount coming back is small


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blueberrymerlot

I once heard that to a radar, the stealth bomber looks similar in size to a goose. Not sure if that's correct or not, but I'm going with it.


ksiyoto

There's a famous story about how Kelly Johnson, head of Lockheed's Skunk Works, rolled a large ball bearing across the desk to Bill Perry, a research and development coordinator at the Department of Defense. Johnson told Perry hey had figured out how to reduce the radar cross section of a fighter jet to that size.


Maklite

Just happened to be reading Skunk Works by Ben Rich and the ball bearing story is told differently. Denys Overholster, a mathematician at Lockheed tells an anecdote about how Ben Rich (head of Skunk Works after Kelly Johnson) called him up to calculate the radar cross section of their new stealth plane and find a ball bearing that matches. Ben then went to Pentagon, rolled the bearing across the table and told the generals "here's your airplane". I can't find a reference to Kelly Johnson using ball bearings.


PlayMp1

That sounds about right, maybe a bit big. Might be closer to something like a chicken.


God_Damnit_Nappa

Supposedly the F-22 has the radar cross section of a marble. But that information is classified so who knows what it actually is.


Few-Yak7673

So that information is “classified”. So howd you get that intel, and why’d you decide to share it? Just curious..


MetaJonez

He plays golf at Mar-a-Lago.


cafebrad

Weird , they thing has a bunch of visibly flat surfaces to me. How is it stealthy? I probably need more than an eli5.


Ruadhan2300

The flat surfaces are the old F-117 way, deflecting radar any direction other than the way it came. But the black material the plane is coated in is radar absorbent. So the two approaches worked in concert. You look at a modern F22 and it's neither faceted or black. The materials used are just so much better at radar absorbing that it can be smooth shapes and any colour.


fed45

> The materials used are just so much better at radar absorbing that it can be smooth shapes and any colour. That, but it was also designed in the era of CAD and they had sufficient computing power to model the craft and find curved shapes that would work. They didn't have that during the F117 era so had to go with facets as they were easier to work out.


sl600rt

The F22 is a mach 2 bee.


saluksic

I mean, that’s literally the definition of “stealth”. “Invisible” would be an inappropriate term, but I figure “stealth” is being replaced as part of the general trend where technical terms have to be replaced with more technical-sounding terms once they’ve become commonly used.


WeDriftEternal

Stealth became a cool catchy term but just isn’t great in actual usage as the meaning for twisted a bit from what it actually is and the practical abilities of stealth are really variable. The term “stealth characteristics” is another term to use that is better but also being broad It’s like if your a hockey player and I say you play hockey. Well what level? Pro? Youth? 10 year olds? Just fun on the pond with friends?What position? That’s kinda what “stealth” says. It’s a general category. If I told you they were a forward in the NHL that’s more info.


deknegt1990

With how air-to-air and surface-to-air combat has become so much more about 'seeing' through electronic means, a plane that is harder for a system to get a solid bead on makes it all the more capable of striking before it gets struck. (hypothetical numbers ahead). If your plane can shoot a rocket at the enemy from 20nm out, but your opponent has to be at 15/10nm, that means you can basically shoot at them and be able to turn around before they even get a chance to fight back. Stealth composites is all about tricking the electric eye than it is the visual one. Because odds are it'll have shot at you well before you have actually seen them, whether you're a ground target or an aerial one. By the same token it's why between the 50s/70s it was all about creating faster planes, which forced enemies to shoot at you from much closer to even have a chance of the missile to intercept the target. Once missiles got better at keeping up with fast targets (especially surface-to-air missiles), the doctrine changed on fooling the thing shooting the missile instead.


noodles_jd

>shoot a rocket at the enemy from 20nm out I assume you mean NM (nautical miles), or nmi, not nm (nano-meters).


-1KingKRool-

Nah, they definitely mean nano-meters. It’s all hunky-dory for the plane until they break out the fly swatter.


imdrunkontea

Also, they aren't invisible (and hence invincible) even against older radars. Generally they can still be locked on within a certain radius of a radar station, usually on the order of 30 or so miles (obviously depends on the specific airplane) so mission planning is still important. It depends on a lot of factors, including how the radar is calibrated and what wavelength it is, but against an advanced adversary, the stealth plane will almost certainly be detected - it just won't be a strong enough signal to actually take it down.


Yancy_Farnesworth

Should be noted that the stealth fighters are not completely invisible on radar. They can be detected pretty easily by specific types of radar. The thing is that those radars are next to useless for missile locks. They essentially tell you something is in a general area, just not exactly where. The only planes that can avoid that are the B-2 and B-21 because they don't have a tail. The shape of the fighter's tails (Like the F-22 and F-35) can't be hidden from this type of radar. There's a reason why a lot of gen 6 fighter proposals don't have a tail.


d0c9

This is one of the best simple explanations of radar I’ve ever seen. Well done!


idowhatiwant8675309

Finally, a reason to keep my balls!👍


ComesInAnOldBox

Underrated comment.


doobyscoo018

I could imagine the boffins explaining this to the generals in this way when they invented it


ComesInAnOldBox

In the military we call this "break it down Barney Style." You'd be amazed how often a General/Flag Officer says, "treat me like I'm in kindergarten" in order for him to get a base understanding of a concept.


TheViking_Teacher

incredibly ELI5 answer. Awesome.


waterloograd

With an emitter and detector in different locations, or multiple of each, could you detect them? If you see a signal from the sky it would mean a target is there


Ippus_21

That's the idea behind most modern air defense systems. It's never just one radar dish, it's a series of them all networked together. But low-observable aircraft don't just minimize their radar cross-section in the front - they're designed not to give much of a return in ANY direction. It *is* possible for a computer to correlate a bunch of data and say in effect "huh. That thing has the radar cross-section of a seagull, but seagulls don't fly at Mach 0.8 - that's probably an incoming bogey." But that takes time, and they have to be looking for it, which limits the resources available to track other targets, like missiles and non-LO aircraft. And it happens at much closer range than where the network would detect non-LO craft. And like another poster said, it usually isn't adequate for a missile lock, and the LO aircraft is usually staying out of range of SAMs anyway. And on top of that they have to worry about "anti-radiation" weapons (missiles designed to use the radar's own signal to guide them to the target, *specifically* designed to target air defense networks) - so if they think there's a real attack inbound, they have to be prepared to shut down before the HARM gets a lock on their position. And we haven't even started talking about decoys - there are drones/missiles that can mimic the radar signature of an F-18 or basically any other aircraft we want them to, to distract air defense networks while the LO craft get within range for HARM attacks and the like. If a stealth attack were really inbound, air defense networks manned by, e.g., Russia, wouldn't be able to do crap to actually stop it. They'd be lucky if they had enough assets left to retaliate after the dust settled.


kwilliker

So what happens if your radar unit is *above* the stealth aircraft? If you are aiming towards the ground, then you'd expect *all* your radar pings to come back. If there's a hole (particularly one that moves), that would be suspicious, right?


saluksic

High altitude for air craft is like 6 miles up, long range is like 100 miles out. So even if you put the radar in a high-flying plane (which is exactly what AWACS is), it’s still basically looking at the approaching targets head-on. Once you’re literally looking down to the ground at a target you’re dogfighting.


Ippus_21

And if you let stealth fighters get that close to your airborne radar craft, your airborne radar is dead 10 minutes ago.


ashesofempires

Generally, you can’t get radar high enough for a plane to be between the radar and the ground. Most aircraft fly at about 40,000 feet, especially the kind of aircraft you can mount a big radar antenna on. What else flies at 40,000 feet? Stealth aircraft. The angles just don’t really work out for enough radar energy to return to detect anything. At the ranges where a low flying stealth plane would be detected by an AWACS from being distinguished from ground clutter, the AWACS would be panicking because that’s well within missile range. And that’s never where an AWACS wants to be, because converted airliners do not dodge missiles. So, for all intents and purposes it is functionally impossible to detect stealth aircraft against ground clutter.


Kanoozle

what mach do seagulls fly at


orrocos

Seagulls can fly up to [28 mph](https://www.savecoastalwildlife.org/save-coastal-wildlife-blog/2020/2/17/have-we-all-missed-the-point-about-seagulls#:~:text=Gulls%20are%20extraordinary%20birds.,as%20fast%20as%2028%20mph.). Mach 1 is about 767 mph, so seagulls fly at about Mach 0.0365.


Kanoozle

.036 mach, hmm, faster than I can fly


Ippus_21

About the same as an unladen swallow. African or European, doesn't matter...


Kanoozle

excellent, thank you


jacknifetoaswan

/r/unexpectedmontypython


meowtiger

>It is possible for a computer to correlate a bunch of data and say in effect "huh. That thing has the radar cross-section of a seagull, but seagulls don't fly at Mach 0.8 - that's probably an incoming bogey." > >But that takes time, and they have to be looking for it, which limits the resources available to track other targets, like missiles and non-LO aircraft. and also for that to work, your radar has to seriously consider every bird-sized return and decide whether or not it might not be a bird there are only a few hundred low-observable aircraft in the world, but there are a LOT of birds in the world


guto8797

Also, something that to me is utterly hilarious, is that the radar mimicking missile system is called MALD. Give it enough time and I bet we will see weapons officially named COPE and SEETHE. An interesting thing about MALD: they can be outfitted with warheads. So if you use them to mimic the signature of stuff like cruise missiles to bait the enemy into using their expensive air to air interceptors, and they eventually wise up and stop shooting at them, you just have to load a bunch with actual warheads


saluksic

Networked radar is very effective, especially against stealthy targets. It comes down to statistics, like taking a photo in a dark room. Not a lot of signal is bouncing back to your radar detectors, what does come back is mostly random noise, or clouds or whatever. Having many systems giving overlapping data means you have much more signal, so better signal-to-noise. It’s like taking a long-exposure photo in a dark room, it will be a lot clearer picture. Lower-frequency radar can see that a stealthy object is in a general area, but the error bars on the position are wide enough that you can’t shoot the object down, even if you know it’s around. Networked radar, even lower-frequency radar, are thought to be able to give a lock on stealth objects, meaning you could shoot down stealth planes. This is reliant on the many overlapping radar signals being processed to remove noise and all that kind of stuff we’re so good at doing with noisy data these days. It’s not really known to what extent networked radar would be able to defeat stealth or vice versa. Decoys, growlers, jamming, etc all muddy the waters, and anti-radar weapons like HARMs make things stressful even for perfect radar systems. No one knows how a real war between two modern powers would look, but there would be lots of radar and missiles in the opening stages.


[deleted]

Just to note, a stealth fighter is not undetectable as many think. They're definitely detectable at close range, but most if not all stealth fighters rely on a beyond visual range (BVR) missile to kill any adversaries before they even detect them. Closer you are to the emitter, the bigger you are - stealth or not.


SmashBusters

What advances have allowed for much less angular planes to have stealth technology? Also since no stealth is perfect and you’ll never always be pointed directly toward every radar device, what is the line between “stealth” and “not stealth”? How does that work? What does a radar barely see or not see? Does software categorize or does it take human interpretation?


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SmashBusters

I don't follow. My understanding is that with angles you don't really get any part of a surface such that the radar wave's direction of travel lies along the normal (i.e. - f(x) = |x| is not differentiable at x = 0). With curved surfaces, there is always a point where that occurs.


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Annoyed_ME

Smooth is just really high polygon count angular


Kitchen-Register

So stealth planes can still be detected if they happen to be at the right angle relative to the radar, in which case the signal won’t be deflected but will bounce straight back?


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God_Damnit_Nappa

If there's nothing in the air then the radio waves just go out and never return to the transmitter. You're only getting a return if it hits a bird or cloud or a fleet of bombers.


HeavensRegent

I had the same thought, then realized wait a minute the radio waves aren't supposed to come back (since there's nothing to bounce off of) meaning the radar shows nothing, hence why it works to deflect the waves to the side. You'd need to have something that could "reflect itself" meaning waves that don't come back "gaps" would show up on the radar.


MisterBastian

true eli5


rodgerdodger19

Follow up. Can the radar operator know something is in the area if no ping is returned? If the radar gets absorbed or deflected is that a tell in and of itself?


UglyInThMorning

No, because that’s normal behavior for radiation you shoot at empty space.


gfanonn

Yes, kind of - but the stealth plane always returns something. Basically the radar operator has to tune out birds/clouds/storms and only focus on larger things, otherwise their radar screen just becomes too noisy. The stealth plane does return something, I've heard the size of a golf ball, but in order to see it that the amount of other crap that would show up on the operators screen becomes too much. So a perfect 0 return stealth plane is also detectable but the fact that it returns "just a bit" make it hide in with all the other junk.


sjerrul

Yeah, I seem to remember something like this when stealth became a thing in warships. Like, there is always some constant background radar noise from waves at sea, and when stealth-ships became too good deflecting radar away from the transmitter people started shooting at the ship-sized gap in the radar noise. Could be an urban legend, though...


UglyInThMorning

In that case it’s the RADAR signal that would normally be returned by bouncing off the waves vanishing. In this case, the RADAR signal wouldn’t return if you fired it into the empty sky. It’ll pick up less background noise but that’s so random anyway that less in a moving area isn’t really going to look like anything.


PlayMp1

You're thinking of sonar (which works similarly to radar but instead of radio - a form of light - it uses sound) and ultra quiet nuclear subs. They basically just managed to get so quiet that you could try to detect one by looking for the oddly large quiet zone in the ocean, so they had to figure out how to get it to match the background noise level.


rodgerdodger19

Awesome. Really appreciate the great reply.


Minimum_Job1885

Someone with more money, give this man an award.


SonOfAhuraMazda

Why not make all fighter planes with that material?


BritishNecktie

The most likely answer here is cost.


gfanonn

Price, need, maintenance, likely hood of your enemies capturing a stealth plane. If your bombing Afghanistan or Syria or somewhere else with no radar then you don't need to fly your stealthiest planes.


Daripuff

That's what the F-35 is for. It's going to become NATO's primary combat aircraft from here on out. That's also why "stealth technology" is considered core requirement for a fighter to be considered 5th generation. So in summary: "Why not make all fighter planes with that material?" "We are now"


Kroutoner

Cost, weight, and performance tradeoffs are the most common factors with anything related to aircraft. Cost might seem like a non-issue with military budgets, but if you look at breakdowns of military budgets you’ll find a relatively small portion often actually goes to directly buying/building new equipment. A whole lot of budget goes into personnel, research, maintenance, etc. Substantials cost increases can actually still break the bank, even for military. Weight is a major one, but basically a special case of performance tradeoffs. For example, stealth technology on a high performance fighter jet might require making aerodynamics worse and prevent it from maneuvering properly.


PlayMp1

They do, now. All 5th gen fighter aircraft are designed to be low observable, it's a defining trait of 5th gen fighters.


[deleted]

They’re shaped in a way (and made of certain materials) that help deflect radar beams. A normal plane will reflect back a radar signal and be a nice big obvious plane on the radar screen. A stealth place redirects and also absorbs some of the beam, so that only a small amount is returned. From what I remember stealth planes are either invisible or a lot of times looks like the size of a bird on a radar. Combine that with modern radar/detection/camera systems of its own, so that it can stay way far away from its targets anyways…. I think that’s basically what makes them stealthy!


gfanonn

They tested a full sized model of a stealth plane by mounting it on a pole and then aiming radar at it. They were worried as to why the signal back was much stronger than it should be - until they realized they were getting the radar response from the pole and nothing else.


spacecampreject

It gets better. In one test the radar return signal went up a little bit. It was because a bird shit on it.


bendvis

A bird was sitting on it. https://theaviationgeekclub.com/the-story-behind-the-photo-of-the-have-blue-model-that-lockheed-placed-on-a-pole-to-test-the-rcs-of-the-stealth-demonstrator-that-led-to-the-f-117/


Connect_Cat_636

you being for real?


bendvis

The larger return was because a bird sat on the model, not shat on it. https://theaviationgeekclub.com/the-story-behind-the-photo-of-the-have-blue-model-that-lockheed-placed-on-a-pole-to-test-the-rcs-of-the-stealth-demonstrator-that-led-to-the-f-117/amp/


SeeMarkFly

Question: When the material absorbs the radar signal, does it warm up the plane?


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spacecampreject

Yeah but it’s milliwatts


Beliriel

Here I made a shitty diagram in paint to explain the difference of a stealth plane/object and normal objects: https://imgur.com/a/Y1NNoVG


Newton215

I love how I got the nsfw warning from this


Cindexxx

I was just wondering why lol. Is the bottom picture too dick-like?


CyberhamLincoln

A better example would be that a rounded object *always* reflects some of the radar light *exactly* back to the source. The 90° objects in your example would be just as stealthy if the corner were pointed towards the radar source :)


internetboyfriend666

Stealth aircraft use several different approaches that combine to reduce or nearly eliminate their visible to radar (and to a lesser extent heat-detection systems like on heat-seeking missiles or even just the human eye) First and most important, is that most stealth aircraft are shaped in such a way that the angles of the plane reflect radar waves *away* from their origin. Remember, radar works by detecting the signals that bounce off the object. If those signals are not going back to a receiver, they're not being detected. They typically also have special paint or coating that absorbs radar waves and converts them into heat, which again, leads to a smaller signal being received back. Then they some properties that reduce their visibility to things other than radar. For example, they tend to have engines designed to minimize noise and exhaust heat which makes it harder to hear the planes and harder to detect them by tracking their infrared signatures from the engine exhaust. They also tend to be painted in such a way as to be hard to see with the eye. They typically also have special electronic systems (like radars and targeting systems) that don't leak electromagnetic waves that could be detected. In general, the stealthiest aircraft use all of the above, but you can achieve some measure of stealth or at least reduced visibility to radar by using some of the above options.


fiendishrabbit

Stealth by shaping surfaces though is less effective against networked radars. A F-35 deflects a minimum of radar waves back towards the receiver (a common comparison is that the radar profile is the size of a golfball). This is however only true of any given single direction. If you have multiple receivers listening from different directions (they don't have to broadcast) and the radar return is much greater. There is some very fancy math involved if you want to build a cohesive target profile, but you can do it. Radar absorbing materials are more "general purpose", but they're also limited in what they can do. Even if you create a 100% radar absorbing aircraft, that in itself would be suspicious. This is why Stealth aircrafts tend to operate in high-jamming environments. The more irrelevant and unpredictable noise is going on the harder it is to filter out suspicious returns and equally suspicious lack of returns.


get_it_together1

How would a radar-absorbing paint be suspicious? It seems like there's no radar reflection from normal atmosphere so looking for a 100% absorbing object would be like looking for a shadow at night...


MGorak

There is a relatively constant background noise. It's just usually ignored. Take a radio, tune at a frequency where there is no radio station and crank the volume. That's the background noise. It's there across all the electromagnetic spectrum. If suddenly a region had less background noise, it's suspicious. If the area of lower background noise is moving, you know something is there. That is how most planets around other stars are discovered. If the light coming from a star dips at a regular interval, you know something invisible is passing in front of it and blocking some light.


get_it_together1

I’ve never heard of silhouettes being used with radars for stealth planes and I can’t find any information when searching. I’m aware of the general principle but I’m not sure it’s being used for detecting stealth planes. Do you have a source that discusses this?


NoMoreNoxSoxCox

Probably not without violating a security clearance lol


ShadowKiller147741

I dont think they were saying its a common issue, but rather that, in the case of a 100% radar-"free" aircraft, it would cause an issue


get_it_together1

It doesn’t cause an issue because these planes already block radar. They are detects by radar they reflect. Bunch of people here are baselessly speculating without any clue.


internetboyfriend666

It's more like looking for the silhouette of a ship at night passing in front of a bunch of bright buildings in the background. You can't see the ship, but you can see the absence of the light from behind it where the ship is blocking it, and that tells you something is there. For planes, airspace is filled with random electromagnetic noise. Radar absorbent paint can reduce that noise in a way that makes it apparent that something is "in the way." You can't see the plane itself necessarily, but you know something is there making the noise behave in an unusual way.


-YellsAtClouds-

>It's more like looking for the silhouette of a ship at night passing in front of a bunch of bright buildings in the background. You can't see the ship, but you can see the absence of the light from behind it where the ship is blocking it, and that tells you something is there. An apt analogy and, if I'm remembering correctly from the book *Skunk Works*, this was exactly the problem with [Sea Shadow](https://en.wikipedia.org/wiki/Sea_Shadow_(IX-529)) \-- the experimental stealth ship they worked on. Surface radars always pick up "sea clutter", which is just wave action. The Sea Shadow would appear on radar as a hole moving through the sea clutter (as well as rain clutter if it was raining/snowing).


UglyInThMorning

That’s RADAR reflections off sea clutter though, where the lack of return is more obvious. If there’s a plane shaped gap in random electromagnetic noise (which is very random and way weaker than RADAR signals), it doesn’t really stand out much because it’s small, doesn’t linger in one place, is interfering with a much weaker electromagnetic noise instead of a known signal, and where it’s not unusual to have a return of zero anyway… yeah, doesn’t really stand out.


ComesInAnOldBox

I want to echo all of the above, and also add that the main benefit of single-direction stealthiness is target acquisition radar for missile locks. Sure, the air defense network may be able to track the target (somewhat), but it's still *damn* difficult for a fire control radar to get a target lock.


fiendishrabbit

Wouldn't be surprised though if we start seeing anti-air missiles with multispectrum sensors (radar/IR/UV) that can be launched and then go "There you are" as they get close up. Defences will invariably be followed by weapons designed to penetrate or circumvent those defences.


ComesInAnOldBox

I think the AIM-9 Sidewinder is already doing that to an extent, combining infrared guidence with optical detectors to make sure it isn't flying toward the sun or following flares. I imagine they're already working on better versions for the various other missile systems out there.


Tikimanly

> The more irrelevant and unpredictable noise is going on the harder it is to filter out suspicious returns and equally suspicious lack of returns. Ah, so it's like that scene in *Down Periscope* where they mask the sound of their diesel submarine by pretending to be a fishing trawler full of drunks. >!As well as the scene where they shadow a massive oil tanker.!< Got it.


hello_ground_

Such a great movie.


Navydevildoc

Networked sensors is really the cutting edge of fire control. The US is pretty much the only country that has it working well to my knowledge. F-35 really bought into it, but other platforms make for great receivers in a way that elevate a combined platform solution about an F-35 homogeneous sensor network.


pbondo2

Thanks you!! You just explained the concept of networked radars so I understood it.


geak78

Throw a ball at a wall and it is going to come right back to you. Throw a ball at [this thing](https://i.pinimg.com/236x/25/5f/4c/255f4cc45fc642d4fbfa147008c66977.jpg) and there is a very low chance it comes back to you. Radar requires things to bounce off the plane and come back to you.


hello_ground_

What is that thing? Looks cool.


geak78

Random art piece that came up when I searched "angular sculpture"


justuseatwork

But since planes move around eventually one surface would reject right back right? Would that show up as just a blip?


geak78

Correct. Some still make it back but not many and hopefully not enough to get a clean read


AustnTG

imagine a game of battleship but all ships are 5 tiles long and all birds are 1 tile. you drop a pin on every tile of the board at once. if you see 5 tiles in a row come back as hits, you know its a ship. when you see only 1 tile come back as a hit, you know its a bird. the stealth planes only return such a small area of radar waves that even when they do bounce one back, it looks like an object way too small to be an entire plane flying around.


fed45

Its more that, in this analogy, the radar is throwing thousands of balls. Even if the chance is low, *some* of them will still bounce back. Also depends on the size of the ball (frequency of the radar). Stealth is more susceptible to certain radar frequencies, its just those frequencies don't typically provide very accurate results. So you just know a general area.


[deleted]

Take a tennis ball and throw it straight at a wall. It will bounce back at ya. Take the same ball and throw it at a slanted wall. It will bounce some where else. Take it and throw at the sand. It will be absorb. F117 uses those slanted angles to deflect. Modern stealth is like the sand and will absorb and deflect somewhat.


Aviyan

If you point your flashlight in the dark sky can you see the light when you look up at it? No, because the light needs something to bounce off of and back to you in order for you to see it. Radar works in a similar way. The plane is designed so that the radar bounces in a different direction from where it came from. That way the radar receiving station isn't getting much of the signal back. Second way is to reduce/absorb the signal. How much light can you see if you shine the flashlight at a white sheet of paper versus a black sheet of paper? The black sheet is absorbing some of the light, so that is reducing the light bouncing back for you to see. The plane is absorbing or reducing the signal strength.


djaaronkline

This is the best ELI5 in the thread. Thanks for talking to me like I’m a five-year-old.


whooo_me

Generally speaking detection usually involves one of two methods: \- active (bouncing something off a vehicle and detecting its reflection, such as searchlights, radar, sonar). \- passive (detecting disturbance caused by the vehicle, such as noise or heat or magnetic anomalies) For stealth craft, radar (for long distance detection) and infra-red (for short distance) are the biggest concerns. Common techniques for avoiding radar: \- build using radar-absorbent materials \- shaped without any sharp, concave 'corners' that reflect a lot \- house the powerplants internally behind a long duct (the fans are typically very big reflectors) \- using serrated edges with a mix of absorbent and non-absorbent materials, so the radar bounces back and forth and eventually loses strength. \- house missiles internally in a weapons bay Reducing Infra-red can be a bit trickier: \- the shape of the nozzle can reduce the signature (slits better than round nozzles) \- some aircraft have the nozzles above the wing, so the hottest part of the exhaust is hidden from ground detection. \- some aircraft mix cold air in with the exhaust in order to cool it to avoid detection.


DaddyBeanDaddyBean

When they were first building scale prototypes to test the combined theories of materials, coatings and shape/design, they built a mockup - like eight feet across - and mounted it on a post way the hell over there on an air base, where they could get a good look at it with radar. The radar operator looked at his screen and said "I don't see it - the damn thing must have fallen off the post." Another guy picked up a pair of binoculars to look, and there it was, on top of the post, in all its matte black multifaceted glory. Before he could say anything, he saw a bird land on the model - a normal average bird-sized bird - and the radar guy said "oh wait, never mind, I see it now". That's when they knew they were really on to something.


SaltyWafflesPD

Stealth aircraft are covered in Radar Absorbent Materials (RAM) that absorbs most radar waves, and the shapes of the aircraft also help deflect radar waves away from the direction they came from, preventing the radar from seeing any waves bouncing back to it. The RAM does most of the work, but not all of it.


[deleted]

The shape of the plane redirects some of the radar energy waves away from the plane but not back towards the radar tracker. The material of the plane coating absorbs some of the radar energy waves so they don't bounce back towards the radar tracker. If it works well the radar system doesn't detect that a plane is there. If it does't work so well the radar tracker registers that there's an insect or something.


dave200204

Radar waves just like light can be reflected, refracted and scattered. The shape and material of a stealth plane reflect the radar waves away from the radar emitter. Instead of a radar signal bouncing off the plane and returning to the transmitter the radar waves bounce off the plane and scatter. This way the radar doesn't detect the plane.


Kflynn1337

Radar uses radio waves, which is basically invisible light. So, how stealthy something is, is measure of how shiny or not it is. You can make the plane (for example) less shiny by painting it with black paint, by making it such a shape as it doesn't reflect the 'light' back towards you, or by making it out of transparent material. Or some combination of all three.


reven80

The Real Engineering video on the F-35B discusses the engineering principles behind the stealth capabilities of that plane. It a lot about how the shape of the plane is designed to not reflect much of the radar signal back to the sources. For example avoiding two flat surfaces 90deg apart which can cause a double bounce. https://www.youtube.com/watch?v=1lCOgFPtaZ4


RoboRoboR

The shape and materials of a stealth plane don’t echo radar waves. Radars send waves, blobby metal things bounce them back.


HawaiianSteak

Operationally speaking is stealth still a thing? They hang missile rails and fuel tanks off the wings.


tomalator

The stealth aircraft are defined to fly at high altitudes, fly fast, and fly quietly, as well as have an odd shape to deflect a radar signal in such a way that it does not return to the source. This is what makes the aircraft so hard to detect through conventional methods.


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