Czech Passive Radar Detecting B-2 at 150 miles (2015) | Hacker News Reader

Czech Passive Radar Detecting B-2 at 150 miles (2015)

defence-blog.com

118 pointsenigmabridge120 comments

Hmm, not your typical RADAR. This is basically using the RF emissions of the plane, and their detection at multiple RF detection stations with synchronized clocks, to determine the difference in arrival time. The radio emissions all travel at the same speed through the air, the difference in arrival time can be used with some simple trig to figure out where the RF emitter is. There are a number of Time Difference of Arrival or TDOA systems out there. It is why I expect aircraft stop using their radios when they are about to engage their targets.

That said, they are "easy" to jam in the sense that when you have two radio signals on the same frequency, they will interfere with direction finding. And there is a lot of noise in the RF spectrum out there, especially during thunderstorms.

>multiple RF detection stations with synchronized clocks, to determine the difference in arrival time. The radio emissions all travel at the same speed through the air, the difference in arrival time can be used with some simple trig to figure out where the RF emitter is.

That's a fancy way to say 'triangulation'.

I believe it's technically trilateration, not triangulation.

Contemporary passive radar arrays are phase sensitive so it ain't that simple either.

It would be triangulation if the system was measuring the arrival angles of the incoming signals. If the system relying solely on arrival time differences, it's likely doing something based on trilateration.

Here's an interesting variation that uses RTL-SDR's: https://dopplerfish.com/passive-radar/

Cool we can build our own radar!

More to the point, detecting a stealth aircraft is very different from shooting at a stealth aircraft.

This radar would likely not have the location accuracy of where exactly the B-2 was to accurately engage it with a missile. Your accuracy would be limited by the rate of RF pings the B-2 is putting off, and then the margin-of-error of these RF waves and receiver.

This is one difference between the B-2 and stealth fighters like the F-22 & F-35: The latter are not necessarily designed to be invisible, only impossible to reliably hit. Their shapes and radar-absorbent paint deflect, diffuse, or absorb the high-frequency bands used in the terminal guidance of missiles. So they are hard to target. But they can be picked up at range by long-distance, long-wavelength VHF and UHF radars. These frequencies, used in early-warning radars, have too low-optical resolution* however to be any good at aiming guns or missiles. The B-2's "flying wing" shape is able to not-interfere with these wavelengths though, and hence hides from them. In that sense, this is somewhat interesting, if neutered for the reasons you mention.

*You can only localize the detection to a few sq hundred meters, even kms.

And also, searching the top speed of a B-2 at 628mph, if detected at 150 miles out only gives them 14 minutes. Which is both a lot, or a little. Depending on how prepared for action someone is.

Or a lot less than that, if the B-2 isn't using gravity munitions.

Well since there are so few B2 and they are essentially irreplaceable, I imagine standard wartime doctrine for the adversary would be to ignore target protection as a concern and go straight for the plane even at the risk of losing several of yours by flying over territory you don't control.

In reality, what would make a difference is coordinating communications and decision making.

If you can localize down to the range of a km? Can't you just shoot down optically? A giant dark plane blotting out the stars...

Yup, it seems to me that the optimal missile would use mid-course guidance before doing IR / visual light homing in the terminal phase.

All the stealth craft also included some IR avoidance as a matter of course, IR seeking missiles existed at the time these were designed. It's unclear if a more modern missile would still be sensitive enough to lock on and avoid chasing flares.

The techniques they used to decrease the IR visibility are pretty neat. The engine nozzles are over the wings and there are a lot of airflow tricks used to cool it down faster so from below there might not be enough plume to track from a surface launched missile coming, from below at least.

https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit#In...

Conventional IR countermeasures (spatial, spectral etc.) really are becoming a thing of the past.

When you’re talking about terminal IR guidance on any modern missile, generally the IRCCM will be so good that the probability of defeat with a flare cocktail is below an acceptable risk threshold. DIRCM is the current answer to this problem and—to tie this in with the parent comment—renders terminal IR guidance much less effective than MMW or other RF guidance.

https://en.m.wikipedia.org/wiki/Directional_Infrared_Counter...

Flares don't do much against anything besides mid and short wave infrared.

It's impossible to hide from long wave IR sensors, which detect the heat signature of the plane itself, and not its exhaust.

Recently in DC they detected a plane that did not respond to warnings. The optical system then also detected the plane and panic ensued. Problem was the radar system was showing a phantom and the optical system saw a nearby plane and thought it was confirming the phantom.

Tldr; it's complicated

https://www.thedrive.com/the-war-zone/31222/mysterious-airsp...

As we saw with both Iran and Russian AA teams shooting down passenger jets...

Don’t forget USA navy vessels shooting down passenger plane.

Hopefully the US has learned something in the past 32 years since that incident. It seems that even our allegedly sophisticated adversaries haven’t in the present time.

At least the Russian team was merely operating a Buk in a clandestine op in the middle of a field in Ukraine (and the US ship was technically in Iranian territorial waters in 1988 during an actual war), I’m curious what Iran’s excuse was shooting it down in their own property?... maybe we’ll learn more about it eventually. Bellingcat was able to provide the actual team member names and wiretaps of the Russian soldiers.

An airplane at altitude doesn't blot out stars. Optical sensors are nearly useless, especially against a black aircraft at night.

Not to sound skeptical, but I've seen some stuff Ratheon was putting out at least 10-15 years ago and I think it had some pretty impressive optical sensors. Are we including the various infrared frequencies?

Optical and infrared sensors have improved a lot and can be a useful supplement but due to limited field of view and interference from weather you generally can't count on them for primary search. Unless the target is really time sensitive, B-2 mission planners try to fly at night in bad weather when those sensors are seriously degraded.

I doubt it. If people are able to photograph dark birds at night, I see no reason why a missile with much bigger optics and more efficient (wider band and monochrome) sensors wouldn't be able to find a plane.

They're also not quiet.

there have been developments using the sound for terminal guidance to augment that.

I'm sure any modern IR missile can shoot down any current stealth plane if it knows the location to within a few kms.

There are FLIR images of thr F22, nothing extraordinary about it in the IR spectrum.

A lot of Russian planes have Electro Optical systems for targeting. Usually they are IR based locking onto hot engines and such like a typical Fox 2 (Heat seeking missile) Range of IR tracking is pretty small for head on planes and more importantly your missile needs to know where to look in the first place to acquire the target. Also stealth aircraft have reduced heat signatures making it harder to pick them out against the background. Also you have problems with determining contrast against the background due to diffraction.

Essentially the passive array in this article is in the class of "Early Warning Radar" which is used to alert Combat Air Patrol aircraft and SAM sites where to start looking for the contact.

If you wanted to use this with a networked radar guided missile you would have problems with terminal guidance. If the missile could acquire the target as it came into radar range for the radar cross section of a stealth aircraft, there is very little chance it would have the energy to track the target. It would essentially need to make a right turn midair to track on the target. All the while the missile's radar will be making the plane's RWR light up like a Christmas tree.

> they are "easy" to jam in the sense that when you have two radio signals on the same frequency, they will interfere with direction finding

Nope, it's a more sophisticated algorithm they're using. Our company held all the patents for locating GSM cell phones calling 911 using UTDOA. The U is uplink, meaning the network of receivers listens when the phone talks. The patents entail each receiver taking a sample of the signal they heard in that time slot on that frequency. They upload the sample to a processor which tries to correlate all the samples with some DSP math, sliding them around in time to see if they match. If they do correlate, the offsets of each one is your delay for doing trilateration.

So if you have multiple talkers at the same time, they can probably be subtracted out by the correlation step.

ECM can be directional (phased array antenna). If an aircraft knew the approximate location of the receiving antennas it could theoretically jam them seperately.

> That said, they are "easy" to jam in the sense that when you have two radio signals on the same frequency,

Not at all. Check out the VLBI technique from radio astronomy, it's not hard to tell that there are two discrete signals.

But that's not really the point: you can see stealth aircraft already with lower frequency radars, just not well enough to shoot them down. It's hard to imagine this passive technique being good enough to shoot them down, either.

https://en.wikipedia.org/wiki/Stealth_technology#Low-frequen...

the low frequency radar thing relates to the active radar in the missile warhead. Not accurate enough for hit to kill missiles, but plenty for modern shaped charge warheads that only need to get within 250 meters or so of the target for a kill, and completely irrelevant for warheads supplemented with optical targeting that only need to be within 5 miles clear line of sight to confirm a lock.

Passive radar uses background RF, usually TV transmitters. Which is why they are the first to go everytime America decides to punish a nation for trying to use something other than the dollar to trade oil or decides to crack down on opium smuggling.

Not really enough though, which is how they lost all the F117s over Serbia in the 90s. One of which I have a framed picture of on the wall along side an original "sorry we didnt know it was invisible" flyer.

Tech has come a long way since then.

> Not really enough though, which is how they lost all the F117s over Serbia in the 90s. One of which I have a framed picture of on the wall along side an original "sorry we didnt know it was invisible" flyer. <

Only a single F117 was shot down over Serbia.

https://en.wikipedia.org/wiki/Lockheed_F-117_Nighthawk#Comba...

Perhaps choose a better source than wikipedia, like people who were there.

https://images.app.goo.gl/vUd8z2gkWEtKWKcJ8

even your source says they hit 2. They claim they downed 3. Americans denied they lost any for decades.

A propaganda poster knowingly conflating the words stealth and invisible, a distinction its intended audience wouldn't be able to make, to mock the enemy? I think I'll stick with the Wikipedia source.

And even that says: Some American sources state that a second F-117A was damaged during the same campaign, allegedly on 30 April 1999;[61] the aircraft returned to base, but it supposedly never flew again.[62][63]

Point is with AA missile is that getting them "on target" is almost as effective as a hit. target has to deploy its counter measures and return home, else next time they are destroyed.

I was addressing the dubious choice of sources delivered with arrogance and condescension. Couldn't care less about how many airplanes did Serbia take down.

so you otherwise accept the Serbians/passive radar got the entire F117 fleet mothballed?

I was addressing the dubious choice of sources delivered with arrogance and condescension. Couldn't care less about how many airplanes did Serbia take down.

Hit 2. Only 1 crashed. You wrote "lost". A plane that flies back to base isn't "lost."

Also, the US didn't deny that they lost any for decades. I remember the news footage (in the US) of the night it was shot down.

You have a peculiar axe to grind here. Are you trying to sell radar systems or something?

> ... their detection at multiple RF detection stations with synchronized clocks, to determine the difference in arrival time.

I believe this is generally called multilateration (MLAT):

* https://en.wikipedia.org/wiki/Multilateration

* https://www.skybrary.aero/index.php/Multilateration

* https://www.sciencedirect.com/topics/engineering/multilatera...

* https://www.navcanada.ca/EN/products-and-services/Pages/on-b...

The B2 is relatively ancient as far as stealth tech goes.

Also, most stealth aircraft are detectable on radar. The question is how big or small is the radar cross section. That’s not something this blog post digs into. Meaning, most of the time a B2 looks like a goose or a small animal.

Correction on my part: The B-2 and F-35 have radar cross sections roughly the size of a marble.

A goose flying at 600mph?

It could happen:

https://en.wikipedia.org/wiki/Chicken_gun

In that vein: cold-war era chicken-heated nuclear bomb (for area denial) https://en.wikipedia.org/wiki/Blue_Peacock#Chicken_power

Oh dear.... Never heard of this but I'm glad the cold war is over.

"Alright chaps, let's bury some 10 kiloton nuclear mines in Germany in case the Russians come.", From wikipedia: "deny occupation of the area to an enemy for an appreciable time due to contamination"

"It was judged that the risks posed by the nuclear fallout and the political aspects of preparing for destruction and contamination of allied territory were too high to justify. "

Ummmmmm yeah WOULD YOU THINK???

"One particularly remarkable proposal suggested that live chickens be included in the mechanism. The chickens would be sealed inside the casing, with a supply of food and water; they would remain alive for a week or so. Their body heat would, it seems, have been sufficient to keep the mine's components at a working temperature."

Ok...... Now I'm really wondering if the Soviets were the crazy ones.

I present you https://foreignpolicy.com/2014/01/30/the-littlest-boy/ which also was to be deployed into prepared shafts to make some area impassable. The keyword here would be "Wallmeister" for the people tasked with that mission.

Entertaining. Excerpt:

> Cold War strategy was filled with oxymorons like "limited nuclear war," but the backpack nuke was perhaps the most darkly comic manifestation of an age struggling to deal with the all-too-real prospect of Armageddon. The SADM was a case of life imitating satire. After all, much like Slim Pickens1 in the iconic finale of Dr. Strangelove, American soldiers would strap on atomic bombs and jump out of airplanes as part of the opening act of World War III.

> From the Army's perspective, the problem was that bombers and missiles were managed by the Air Force and the Navy, leaving the ground force out of arguably the most significant development in the history of war, even as its soldiers would be chiefly responsible for stopping a Soviet invasion of Western Europe. Fortunately for the Army, many U.S. strategists still saw nukes simply as bigger conventional bombs, and America's post-Hiroshima mastery of the cutting-edge science of atomic destruction had filled weapons designers more with a sense of the possible than the prudent. The result was a series of odd creations that made their way into the Army's arsenal, from atomic artillery to nuclear-tipped air-defense missiles.

It's a matter of signal to noise. There's a lot of clutter out there, and most radars have some level of filtering. Most stealth is detectable, but lost in the noise.

It is a game of cat and mouse.

Yes, B2 is relatively ancient, but so is the Tamara passive radar (it was capable to detect B2 and F-117, in the 80'ies). Just like there is a newer stealth tech for planes, there is never stealth detection tech in radars.

Israel stopped intruding into Syrian airspace with the F-35 after the deployment of the S-300 air defense system, which suggests that the most modern aircraft are stacked against even last-gen air defense.

Prior to that they had no issue going deep into the country and taking out Pantsir S1 and other Soviet-era systems

Geese don't go supersonic.

Neither does the B2...

Source on the RCS of the F-35?

Well, in some frequency ranges, using a conventional radar, yes.

And for some applications, that is important.

But even state of the art modern stealth planes are way less stealth than some people expect.

https://en.wikipedia.org/wiki/Passive_radar

In a passive radar system, there is no dedicated transmitter. Instead, the receiver uses third-party transmitters in the environment, and measures the time difference of arrival between the signal arriving directly from the transmitter and the signal arriving via reflection from the object.

Passive radar systems have been developed that exploit the following sources of illumination:

  Analog television signals
  FM radio signals 
  Cellular phone base stations
  Digital audio broadcasting 
  Digital video broadcasting
  Terrestrial High-definition television transmitters in North America
  GPS satellites (GPS reflectometry).

You can build your own with rtl dongles and lots of patience - https://www.rtl-sdr.com/building-a-passive-radar-system-with...

A lot of countries posses radar that can detect stealth aircraft in a certain area, but cannot be used to create a fire solution or even narrowing it down to an area more than a couple square miles.

I believe as a design tradeoff, these planes are much more "invisible" (lower radar cross section) at tracking and targeting radar wavelengths, which must use much smaller frequencies.

They do claim it works on all stealth planes including the F-35, but the B-2 is now 30 years old and was designed in the mid 1980s. Detecting it from 150 miles is impressive, but when they're equipped with 250 mile standoff air-to-surface missiles, ultimately not very useful. I'd be curious how much better the stealth is in the world of supercomputers and CFD for modern planes as well.

Well it's passive radar. So you don't have to outperform the stand-off range of the target, since you are invisible to the plane too.

Is there any risk of demodulator IF or other leakage from these receivers?

Given that it’s entirely reasonable to build a 3 GHz baseband receiver these days, you don’t need IF. The whole thing can probably be made to radiate almost indistinguishably from a cell phone or computer.

A cell phone moving at that kind of speed will stand out.

Would a passive radar usually be moving?

> ...but the B-2 is now 30 years old and was designed in the mid 1980s.

Given that the B-52 is 65 years old, built with 1955's technology, I would expect something more sophisticated to have a longer shelf life than 30 years.

The B-52 is only useful after the enemy's air defense systems have been completely suppressed. It's mostly just a truck.

The B-52 can also carry long range stand off weapons.

That's not how it works. There are loads of planes much younger and more sophisticated than the B-52 which are no longer in service. To name just a few high profile examples: the SR-71, F-117, and Space Shuttle.

Not much. The F-117 is stealth mostly due to shape. The B2 stealth is mostly due to materials and construction techniques. You can run optimization routines to reduce scattering, but it’s not going to be huge improvements

This is a good book that discusses several techniques:

https://www.amazon.com/Radar-Man-Personal-History-Stealth/dp...

B-2 is old but the stealth shaping is still much better than F-35 and there is much more internal structure inside the wings that absorb radar energy. The RAM paints used in B-2 are probably up to date with current technology as well.

B-2 is also inherently more stealthy to to Rayleigh scattering than F-35 is due to the size.

Stealth is not magic. Shaping is 90% of the stealth, rest is the materials and details.

Vera-type radars may be be able to detect stealth aircraft with low angular resolution but they can't be used for targeting.

There is no evidence in the article to assert a B-2 was actually detected at 150 miles outside of unverified claims.

I think the current anti stealth capabilities are not clear, countries that use anti stealth radar are not talking about the capabilities, e.g. what does "The superior stealth target tracking capabilities ensure optimal performance in demanding littoral environments." mean

https://www.thalesgroup.com/en/netherlands/news/new-fire-con...

or "Within this enormous range it detects a wide spectrum of targets: air breathing targets, stealth targets and ballistic missiles."

https://www.thalesgroup.com/de/smart-l-multi-mission-radar-0

or "It is also claimed to be highly capable of detecting stealth targets"

https://en.wikipedia.org/wiki/S1850M

> "performance in demanding littoral environments"

This is a defence contractor 1337 sp33k for "Works well in the South China sea"

Many people fail to understand that there's a huge difference between detecting the presence of an aircraft and actually targeting it. Anti-aircraft weapons must be precisely targeted to have any chance of hitting. So a passive radar can be useful in limited circumstances for cueing other sensors but it can't accomplish much by itself.

Could the adversary still just send cannon equipped fighters to the general that would locate the stealth bomber visually and shoot it to pieces ?

Sure, could be rather hard to do in the night but once a stealth bomber is sighted visually, it is toast - B2 simply has no self defence weapons available at all.

A stealth fighter could be better off if it can defend itself while still avoiding others getting a weapon lock, effectively forcing them to use visually sighted cannon while it can use sensor guided gun and missiles normally.

The B2 especially is huge (there's one on display in Dayton) and likely slow. If it's been localized to within a few km or so, it's probably a sitting duck to any reasonably modern air force.

There is no way a B2 will be deployed without at least a couple fighters escorting it.

If it has fighters escorting it then it is not invisible.... whole point of B2s is to be invisible to long range radars (due to plane geometry). F22 and F35 don’t have this capability.

That's the type of tactic that mostly only works in movies. In the real world interception is very, very hard just due to geometry. Fighters have limited fuel supplies and don't move much faster than bombers. Any no country can afford to keep a lot of them in the air or even on alert status at any given time. So the circumstances have to line up pretty well to get an interceptor in the right place at the right time.

And even then, aircraft like the B-2 are difficult targets to actually hit. At high altitudes they are fairly maneuverable due to low wing loading.

Well, existing stealth bombers (basically B2 at this point) are sub sonic while many fighters are super sonic.

As for range - that's a good point, if your low fregvency or passive radar gives you a big bounding box, your fighters could run out of fuel before they find the stealth bomber. Or it might drop/launch its payload before you catch it.

Supersonic dash capability can help in some limited circumstances but it doesn't fundamentally change anything. Fuel consumption at those speeds is extremely high.

Stealth bombers aren't going to dodge missiles. They need to reach their target before they are noticed at all. Otherwise the enemy will mount a response and intercept the bomber.

That is not realistic. In most circumstances the enemy won't have any defensive assets in the right place at the right time in order to generate an intercept.

It's sort of like if you're deer hunting and spot one through binoculars a mile from you moving away. You're going to have to get really lucky to take that deer.

You're a member of the Deer Defense Corps, though, and this time you're much better armed than the hunter. You've also had twenty years of training for your mission. It's just that the hunter is really hard to see. You don't have to care about a hunter running away from you, that's not your job.

Given that there are very few B2s, they're only going to be sent against the most valuable and well protected targets. Those are the most likely to have very alert defensive assets in exactly the right place to go after the B2s.

> Jamming hard and almost impossible to be destroyed by the anti-radiation missiles kill radar. Positioning and stick to the target in the air, on land and sea surface perfectly, providing enough parameters in real time.

This post is really quite garbage.

That reads like a badly-translated press release. I don’t buy it.

What would air defence against a swarm of a few 1000 UAV look like? Because China...

Drones represent a huge range of different things. Assuming you mean something that’s a replacement for military aircraft.

In order to have a useful X,000miles range and useful payload you need to build fairly large drones which means a large target. If their cheap that directly translates into low speeds making them a very easy target for anti air guns, or low cost anti aircraft missiles.

If you want a large fast drone, that’s getting expensive. To the point where having or not having a pilot makes minimal cost differences.

Note, this assumes it’s part of a modern war with extreme radio jamming etc.

Why would you not deploy smaller drones via another platform?

Small cheap disposable drones are a game changer. Drop them on a military base and have them seek and distort any human shaped targets, any sources of RF radiation, anything that looks like a vehicle or plane...

> Drop them on a military base

If you can get close enough to drop a bunch of slow drones, you can get close enough to just drop a bomb on the whole thing instead. Much more bang for your buck.

Let's also not forget that small drones might become 'banned' much like chemical weapons did, if they ever became viable.

Small drones will never be banned by international treaty. There is zero chance of that.

Why?

Lasers were banned. Where does your certainty come from?

Lasers were not banned and are more heavily used now than ever before. Only blinding lasers were banned by treaty, and even with those China is semi-openly defying the ban.

“Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.“

https://news.ycombinator.com/newsguidelines.html

It’s clear what they where referring to, as the argument was a type of drone being banned not all drones. Saying they “banned lasers” is correct even if they only banned a subset of lasers.

I am genuinely curious if you have a deeper argument. As small anti personnel drones seem suspiciously close to cluster munitions, but might be acceptable.

It was not even remotely clear what they were referring to. There are many different types of lasers.

Considering that the US, Russia, India, and China haven't even signed the Convention on Cluster Munitions there's clearly no political appetite for such bans among countries with large militaries. And such a ban would be unenforceable anyway because small drones are dual use technologies which don't require specialized manufacturing.

I'd argue we've had those for a while, just by different names: cruise missiles, anti-radiation missiles, smart glide bombs, etc. The SDB II has a 60 nm range with active terminal homing, including targeting anything that looks like a moving vehicle. Though I wouldn't consider the SDB particularly cheap, at around 200K each. I would certainly agree the these sorts of precision guided weapons are a game changer, though. I don't believe there's been a conflict yet where both sides have these weapons. Such a conflict would get very very bloody.

A pilot severely limits the kinds of maneuver the craft can perform, where the craft can be deployed from, etc.

F-15s have pulled well over 10g without killing the pilot, however it damaged the airframe beyond repair. An aircraft that could routinely pull high-G manoeuvres would have to be reinforced to the detriment of its weight (and thus its size/range/load capacity) and cost.

The expected direction of drones is as loyal wingmen (i.e., to carry sensors, weapons and/or fuel) and to be low-cost (i.e., disposable). If your drone costs more than an F-35 you'll want to get it home again, whether there's a human inside or not.

Reference?

http://google.com/

A swarm of a 100 more expensive anti-UAV UAVs.

You'd need a breakthrough in battery (or other form of energy) technology - eg. high range + cheap as hell ...I don't think/hope China will be a world leader on this anytime soon :)

Ofc you can low-tech your way into it by just delivering drones in shipping containers and hiding them close to potential targets... Also, cheap ass drones + bio-warfare would make a killer combo, if you knew you won't get nuked if you implement it...

UAVs don’t have to be battery-powered; don’t mistake them for quadcopters.

What's the mission and purpose of the B-2 these days? It's a penetrating strategic bomber. The justification for it was that it could strike mobile Soviet ICBM launchers. It was never going to be any good for that. What's it for now? Has it ever been used against a sophisticated enemy (i.e. not people who are literally living in caves)?

It's combat debut was during the Kosovo War, which was clearly _not_ people who are literally living in caves, during which the F-117 suffered its only combat loss, shot down by anti-aircraft missiles, successfully tracked by the radar.

OK, but what's it good for today? Kosovo was 20 years ago. If the B-2's role is to fly conventional missions, the MQ-9 can be armed with the same weapons that the B-2 carries.

Getting inside an integrated air defense network to take out strategic targets. It's got what is believed to be a better stealth profile than the f-22 or f-35, while having payload comparable to a b-52. The MQ-9 wouldn't be able to get anywhere close to an air defense network.

OK I'm convinced. What's the 52 for, then?

Large scale strikes also, but after air defenses have been taken down, or suppressed by SEAD escorts. Keep in mind we only have 21 B-2s and they are very expensive to maintain, so it makes sense to use the B-52 whenever possible.

There is also a matter of accuracy. I believe stealth planes are often “detectable” at longer frequencies, which however do not give precise enough information to fire a missile at them. So you’ll know they are coming but can’t shoot them down. I would imagine radio signal triangulation falls into a similar category.

You don't necessarily need the aircraft to emit any signals, you may be able to detect changes in the background RF emissions reflected or distorted by the aircraft. It would have to be enormously CPU expensive but if you can correlate changes in tens or hundreds of frequencies, I can imagine it could be done.

2016: https://www.cnbc.com/2016/09/21/the-end-of-stealth-new-chine...

150 miles is not that much

2015

Who wrote that article? It reads like Chinese that was put through a bad version of google translate.

I mean really who uses 'cum' in an official article (even though it's not in an NSFW context and technically used correctly). It's a word that has fallen into disuse because its 'other' use has taken over its association entirely :) You won't find this in a serious publication.

And this "Distance reconnaissance: 400 km with 20 m wrong; Number of goals can stick to 200 targets simultaneously."

Whatever it is, this ain't English.

cum qa become remains in common use today.

> I mean really who uses 'cum' in an official article (even though it's not in an NSFW context and technically used correctly).

English speakers.

> You won't find this in a serious publication.

Won't I? Then let's search for such usage:

- Seems serious: https://www.nytimes.com/roomfordebate/2015/09/02/whats-the-g...

- Seems philosophical: https://opinionator.blogs.nytimes.com/2015/02/02/how-to-be-a...

- Seems like all publicity is good publicity: https://www.theguardian.com/cities/2018/mar/26/braunau-spotl...

- Seems expensive: https://www.wsj.com/articles/the-force-is-strong-inside-this...

- Seems fashionable: https://www.washingtonpost.com/lifestyle/2020/03/01/paris-fa...

- Seems Swiss: http://www.bbc.com/travel/story/20170717-the-country-that-ca...

- Seems like a headline: https://www.bbc.com/news/world-africa-24960219

It kinda seems blogspammy, true, but 'cum' is common, right? The most typical use in US official stuff is announcing the history of someone and they say "magna cum laude".

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