F-22 hundred of times more stealthy than Su-57?

[Token]

In trying to follow this conversation, when I see the term "dB" I'm thinking, as a musician, that radar -- and detection -- work on a logarithmic scale as well?

They don't work on a log scale, but we often express and measure things related to them on a log scale.

For things like radar we don't have to use the dB scale, it is just convenient because of the large numbers and ratios involved.

For example, a radar might have a peak power of say 100,000 Watts. It might have an antenna gain factor (how much the antenna amplifies the signal) of 1258. It might have a feedline (feedline, be it waveguide or something else, takes the energy from the transmitter to the antenna) loss ratio of 2.2 (you put power in one end of the feedline and less power comes out the other end of it).

These are the total numbers I need to determine the radars Effective Radiated Power (ERP). ERP is one of the important factors in determining radar performance. To use these numbers to determine the ERP the process is the transmitter power divided by the feedline loss ratio, and multiplied by the antenna gain. Peak transmitter power divided by the feedline loss would be 100,000/2.2=45454.5 Watts at the antenna. Multiply that by the antenna gain, 45454.5x1258=57,181,761 Watts ERP.

But, doing it in dB it all becomes addition and subtraction, and working with much smaller numbers. The transmitter peak power (100,000 Watts) is +80 dBm, the feedline loss (the ratio of 2.2) is -3.4 dB, and the antenna gain (gain factor of 1258) is 31 dB (could be either dBi or dBd, not important for this discussion). I just take those numbers and add them up, 80+(-3.4)+31=107.6 dBm ERP. ERP is typically expressed in either dBm (dB based on 1 milliWatt) or dBW (dB based on 1 Watt). I have determined the ERP in dBm, to convert to dBW simply subtract 30, making the ERP 77.6 dBW.

Note that I did not carry any of the numbers in dB out past the tenths digit, and this has caused some rounding errors. I easily could have carried them out, for greater accuracy, but typically working to a tenth of a dB results in errors that are insignificant for normal operations. Such accuracy may be important for lab work, but typically not in the field. In this case the rounding errors have caused the 57,181,761 Watt ERP to become (converting 107.6 dBm back to Watts) 57,543,994 Watts, an error of under 0.1%. As I said, I could have maintained accuracy by not rounding.

But why all this converting back and forth, doing math, just to have easier math? Because we typically don't do that, instead we measure many things directly in dB to begin with, there is typically very little conversion to do.

Antenna gain is most often expressed in dB (either dBi or dBd), so the data on the antenna would say 31 dB of gain, not a gain factor of 1258.

Loss ratios can be, and normally are, directly measured in dB. It would be uncommon to call the feedline loss ratio 2.2, but would be very common to say the feedline has 3.4 dB of loss.

And power meters for radar and similar applications can be set to read out the power in dB, typically either dBm or dBW.

Everything (at least every numeric value or ratio) can be expressed in dB. $1 can become 0 dB$, so 1.3 trillion dollars would be 121.14 dB$, half of 1.3 trillion dollars would be 3 dB lower, or 118.14 dB$.

The one way space loss (how much the signal is reduced as it travels through space) of a 10 GHz radar tracking a target 50 km away is 1 / 438500000000000 what it was when it left the antenna. Or, using the ERP in our example at the top of my post, 57181761 Watts/ 438500000000000 space loss. This means the signal level at the target is .0000001304 Watts, or 0.0001304 milliWatts.

But that space loss, like any other number or ratio, can be expressed in dB also, and we end up with -146.42 dB (in fact, formulas can calculate it directly in dB, no need to calculate it and then convert). By doing it in dB, we start with the 107.6 dBm ERP above, subtract the space loss of 146.42, and end up with -38.82 dBm at the target. If you wanted to you could convert the -38.82 dBm to milliWatts (and find it is 0.000131 mW), but why do that when the rest of what you want to do is probably still in dB? For example, the receiver MDS, the smallest possible signal the radar can detect, will most often be expressed in dBm.

T!

 

[Thumpalumpacus]

They don't work on a log scale, but we often express and measure things related to them on a log scale.

For things like radar we don't have to use the dB scale, it is just convenient because of the large numbers and ratios involved.

For example, a radar might have a peak power of say 100,000 Watts. It might have an antenna gain factor (how much the antenna amplifies the signal) of 1258. It might have a feedline (feedline, be it waveguide or something else, takes the energy from the transmitter to the antenna) loss ratio of 2.2 (you put power in one end of the feedline and less power comes out the other end of it).

These are the total numbers I need to determine the radars Effective Radiated Power (ERP). ERP is one of the important factors in determining radar performance. To use these numbers to determine the ERP the process is the transmitter power divided by the feedline loss ratio, and multiplied by the antenna gain. Peak transmitter power divided by the feedline loss would be 100,000/2.2=45454.5 Watts at the antenna. Multiply that by the antenna gain, 45454.5x1258=57,181,761 Watts ERP.

But, doing it in dB it all becomes addition and subtraction, and working with much smaller numbers. The transmitter peak power (100,000 Watts) is +80 dBm, the feedline loss (the ratio of 2.2) is -3.4 dB, and the antenna gain (gain factor of 1258) is 31 dB (could be either dBi or dBd, not important for this discussion). I just take those numbers and add them up, 80+(-3.4)+31=107.6 dBm ERP. ERP is typically expressed in either dBm (dB based on 1 milliWatt) or dBW (dB based on 1 Watt). I have determined the ERP in dBm, to convert to dBW simply subtract 30, making the ERP 77.6 dBW.

Note that I did not carry any of the numbers in dB out past the tenths digit, and this has caused some rounding errors. I easily could have carried them out, for greater accuracy, but typically working to a tenth of a dB results in errors that are insignificant for normal operations. Such accuracy may be important for lab work, but typically not in the field. In this case the rounding errors have caused the 57,181,761 Watt ERP to become (converting 107.6 dBm back to Watts) 57,543,994 Watts, an error of under 0.1%. As I said, I could have maintained accuracy by not rounding.

But why all this converting back and forth, doing math, just to have easier math? Because we typically don't do that, instead we measure many things directly in dB to begin with, there is typically very little conversion to do.

Antenna gain is most often expressed in dB (either dBi or dBd), so the data on the antenna would say 31 dB of gain, not a gain factor of 1258.

Loss ratios can be, and normally are, directly measured in dB. It would be uncommon to call the feedline loss ratio 2.2, but would be very common to say the feedline has 3.4 dB of loss.

And power meters for radar and similar applications can be set to read out the power in dB, typically either dBm or dBW.

Everything (at least every numeric value or ratio) can be expressed in dB. $1 can become 0 dB$, so 1.3 trillion dollars would be 121.14 dB$, half of 1.3 trillion dollars would be 3 dB lower, or 118.14 dB$.

The one way space loss (how much the signal is reduced as it travels through space) of a 10 GHz radar tracking a target 50 km away is 1 / 438500000000000 what it was when it left the antenna. Or, using the ERP in our example at the top of my post, 57181761 Watts/ 438500000000000 space loss. This means the signal level at the target is .0000001304 Watts, or 0.0001304 milliWatts.

But that space loss, like any other number or ratio, can be expressed in dB also, and we end up with -146.42 dB (in fact, formulas can calculate it directly in dB, no need to calculate it and then convert). By doing it in dB, we start with the 107.6 dBm ERP above, subtract the space loss of 146.42, and end up with -38.82 dBm at the target. If you wanted to you could convert the -38.82 dBm to milliWatts (and find it is 0.000131 mW), but why do that when the rest of what you want to do is probably still in dB? For example, the receiver MDS, the smallest possible signal the radar can detect, will most often be expressed in dBm.

T!

Now that's a lot of arithmetickin' for a guy like me who struggled through college trig, but I think I'm following. To wit, a log is a specific ratio (right?), based on essentially compressing by a given log base as defined for the purpose of the equation being solved?

At any rate, I do understand it better now especially as I understand my guitar amp's wattage being converted into audio dBs. At least I think I do!

They do, yes.

Of course, without a receiver/amplifier, the frequencies cannot be heard by the human ear, but they follow the same logic. Like that hum you get in your electric guitar is 60Hz, just out of human hearing range, but with an amp, becomes audible (I think around the B scale?).

Oh, 60-cycle hum is very audible, especially on my home recordings before I learned how to use an EQ, lol.

The human hearing range is roughly 20Hz to 20kHz, most radar freqs operate in the high gigahertz range (like up to 36gHz).

But all can be justified with decibel logorithyms.

Understood, and thanks to you three who answered.

I am far from a math whiz, but hopefully this helps a little...

Indeed it does. I just didn't want to assume the term "dB" worked the same with electronics as it does with audible sound.

 

[ODonovan]

I don't know where you "read" this, but the F-35 and F-15EX are STRIKE aircraft - in layman's terms, they are bombers. The F-22 is a dedicated air-to-air fighter. The F-35 (and I'm talking F-35A) is basically a flying supercomputer that can fulfill several functions to include battlefield integration and AEW roles. The F-15EX carries "the bombs" but also has an outstanding air-to-air capability.

I've read it in several reports. Here's one from Lockheed-Martin.

F-35 and Aegis Combat System Successfully Demonstrate Integration Potential in First Live Missile Test

Two pre-eminent weapon systems, the F-35 Lightning II and Aegis Weapon System, worked together for the first time during a live fire exercise. The joint Lockheed Martin, (NYSE: LMT) U.S. Navy and...

news.lockheedmartin.com

That's expanded upon in this article.

How the F-35 proved it can take enemy airspace without firing a shot

An F-35B carrie…

www.wearethemighty.com

And here's an article about the "AMBER" system on the F-15EX. It can carry up to 22 air to air missiles.

The King of America F-15EX is Back - Modern, Big, Ugly and More Formidable - Military-wiki

The US Air Force estimates the F-15EX has 70% of the same parts as the F-15C and F-15E that they replace. The F-15EX is said to be easier to fabricate.

military-wiki.com

There have been a number of others, but that covers the basics.


-Irish

 

[FLYBOYJ]

I've read it in several reports. Here's one from Lockheed-Martin.

F-35 and Aegis Combat System Successfully Demonstrate Integration Potential in First Live Missile Test

Two pre-eminent weapon systems, the F-35 Lightning II and Aegis Weapon System, worked together for the first time during a live fire exercise. The joint Lockheed Martin, (NYSE: LMT) U.S. Navy and...

news.lockheedmartin.com

That's expanded upon in this article.

How the F-35 proved it can take enemy airspace without firing a shot

An F-35B carrie…

www.wearethemighty.com

And here's an article about the "AMBER" system on the F-15EX. It can carry up to 22 air to air missiles.

The King of America F-15EX is Back - Modern, Big, Ugly and More Formidable - Military-wiki

The US Air Force estimates the F-15EX has 70% of the same parts as the F-15C and F-15E that they replace. The F-15EX is said to be easier to fabricate.

military-wiki.com

There have been a number of others, but that covers the basics.


-Irish

"So now with this development, an F-35 can pass targeting data to the world's most advanced missile defense system, an Aegis site, that would fire its own missile, likely a SM-6, to take out threats in the air, on land, or at sea."

That's called "battlefield integration." The aircraft will still carry bombs and participate in strike roles.

No where does it mention anything about bomb carrying F-22s (if that's what you meant).

The AMBER rack is a feature that the F-15EX "can" carry if deployed to do so. It's primary mission is to drop bombs but it is a multirole aircraft

 

[ODonovan]

"So now with this development, an F-35 can pass targeting data to the world's most advanced missile defense system, an Aegis site, that would fire its own missile, likely a SM-6, to take out threats in the air, on land, or at sea."

That's called "battlefield integration." The aircraft will still carry bombs and participate in strike roles.

No where does it mention anything about bomb carrying F-22s.

The AMBER rack is a feature that the F-15EX "can" carry if deployed to do so. It's primary mission is to drop bombs but it is a multirole aircraft

I'm sure the F-35 WILL carry bombs and run strike missions, AFTER air superiority is gained. Doing so while enemy fighters are still in the mix puts them unnecessarily at risk. The situation I'm referring to happens in the very earliest part of the conflict. And, I never said ANYTHING about "bomb-carrying F-22s." The F-22s would be establishing air superiority and would vector toward the enemy aircraft, in many cases ones designated by the F-35s. The enemy aircraft would likely not even know the F-22s were there until it was too late. In most cases, missiles either from F-22s or long range "missile boats" would be able to knock out most enemy "stealth" fighters before they had the chance to respond.

Oh, and don't think "can" about the F-15EX and the AMBER system. That was a major selling point for the aircraft.


-Irish

 

[FLYBOYJ]

I'm sure the F-35 WILL carry bombs and run strike missions, AFTER air superiority is gained. Doing so while enemy fighters are still in the mix puts them unnecessarily at risk. The situation I'm referring to happens in the very earliest part of the conflict.

OK, agree - it will carry weapons internally during the initial

And, I never said ANYTHING about "bomb-carrying F-22s."

My misunderstanding

The F-22s would be establishing air superiority and would vector toward the enemy aircraft, in many cases ones designated by the F-35s. The enemy aircraft would likely not even know the F-22s were there until it was too late. In most cases, missiles either from F-22s or long range "missile boats" would be able to knock out most enemy "stealth" fighters before they had the chance to respond.

Agree

Oh, and don't think "can" about the F-15EX and the AMBER system. That was a major selling point for the aircraft.


-Irish

It was but that Amber rack can also deploy air to ground weapons from what I understand

 

[ODonovan]

It was but that Amber rack can also deploy air to ground weapons.

And that makes me so very happy. With the EXs ability to carry almost 30,000 lbs. of ordnance, there will be sh*t blowing up everywhere! Hey, what can I say? I like big booms and I can not lie.


-Irish

 

[buffnut453]

I'm sure the F-35 WILL carry bombs and run strike missions, AFTER air superiority is gained. Doing so while enemy fighters are still in the mix puts them unnecessarily at risk. The situation I'm referring to happens in the very earliest part of the conflict.

Not sure I entirely agree. Air superiority is about more than just tackling enemy fighters. A key element involves neutralizing adversary ground-based air defences and for that you need bombs delivered by a stealthy platform.

There's absolutely no point focusing on an adversary's fighter force if you can't operate 4th gen combat aircraft and non-combat types because of the SAM threat.

 

[Token]

Not sure I entirely agree. Air superiority is about more than just tackling enemy fighters. A key element involves neutralizing adversary ground-based air defences and for that you need bombs delivered by a stealthy platform.

There's absolutely no point focusing on an adversary's fighter force if you can't operate 4th gen combat aircraft and non-combat types because of the SAM threat.

No doubt about it, the F-35 will be a major, maybe the major, SEAD / DEAD platform.

But I think maybe you and others are mixing thought processes. Air superiority itself vs an air superiority fighter. I have no argument about what you said, indeed I agree with it, but a fighter designed specifically for air superiority, like the F-22, might have a very limited ability for other tasking, like ground strike. Sure, it has the SDB, but really, what else would it do in a ground strike role? No modern or smart fight is a single platform doing it all. Among the other forces used, a few F-22's to scrape dedicated air defense aircraft off of them and something like the F-35 using only internals on day one of the fight to kill things on the ground, that is going to be a tough team to beat.

T!

 

[buffnut453]

No doubt about it, the F-35 will be a major, maybe the major, SEAD / DEAD platform.

But I think maybe you and others are mixing thought processes. Air superiority itself vs an air superiority fighter. I have no argument about what you said, indeed I agree with it, but a fighter designed specifically for air superiority, like the F-22, might have a very limited ability for other tasking, like ground strike. Sure, it has the SBD, but really, what else would it do in a ground strike role? No modern or smart fight is a single platform doing it all. Among the other forces used, a few F-22's to scrape dedicated air defense aircraft off of them and something like the F-35 using only internals on day one of the fight to kill things on the ground, that is going to be a tough team to beat.

T!

No disagreement. I'm not saying the F-22 isn't important...it's absolutely critical. I simply objected to the characterization of air superiority as solely an air-to-air fight. For example, we could shoot down every Russian fighter that opposes us and yet not achieve air superiority because S-300, S-400 and (presumably, soon) S-500 SAM systems would significantly hinder our freedom of manoeuvre and ability to achieve operational objectives.

 

[Token]

Why this is important is what I addressed. The target that is 20 dBsm larger will always be able to be detected by radar at a longer maximum range under the same conditions, with the same probability of detection, simply by virtue of its larger RCS.

Using the radar range equation you can calculate the maximum distance a given radar (if you know all of its parameters) can possibly track a given size target. Part of the radar range equation does consider a probability of detection, generally a number of 80% or greater is used. Typically this range performance is quoted as the range to track a 0 dBsm (1.0 sq meter) target, but you can also calculate it for any other size, such as -10 dBsm or -30 dBsm.

Use a known radar example, say the FAA ASR-11 primary track radar. This radar has a specification of being able to track a 0 dBsm target, a 1 square meter RCS target, at 55 nm, or 102 km (Table 3.4-1, page 16, here http://www.tc.faa.gov/its/worldpac/techrpt/cttn9727.pdf ). At 102 km, or less, this radar has a greater than 80% probability of tracking a target with an RCS of 0 dBsm. It does not have the same probability of detection for a -10 dBsm target until the target gets within 32 km, and it will not have that same probability of detection with a -30 dBsm target until the target is within 3.2 km.

Using the real world, known, ASR-11 radar, and assuming the RCS numbers quoted in the Ausie Air Power paper are correct, we can calculate that the ASR-11 radar would not detect (with the standard 80% PD) the inbound (front aspect) Su-57 until the aircraft was inside 32 km, and it would not detect the inbound (front aspect) F-22 until the aircraft was inside 3.2 km.

Other radars will have similar tracking range disparities between the two aircraft. The exact tracking ranges will be different, but the ratio of detection ranges will remain similarly skewed. If the numbers presented in either article are correct, the Su-57 can be seen by radar 10 times as far away as the F-22 can, and I have given a real world radar example using those numbers.

OK, let this be a lesson, never do math in your head in public. If you are going to say something in numbers actually calculate the numbers, or don't be surprised if you mess it up.

The general statement I was making remains the same, the smaller RCS target will always be tracked at shorter maximum ranges, all other things being equal. But the specific numbers I used are incorrect. It appears that at the beginning of this thread I flipped a bit in my head (maybe used the approximate ratios for -40 dBsm instead of -20 dBsm reduction?), got that number stuck in there, and never cross checked after that.

Reading through this thread I see that I repeatedly said something along the lines of "a 20 dB reduction in RCS yields a detection range of 1/10 the original RCS detection range". This is an incorrect statement from the get-go. A 20 dBsm reduction would reduce the detection range by about 70%, not 90%. I even said "using the radar range equation you can calculate", and then I did not actually use that equation to calculate anything but instead I rounded things and guesstimated based on my original error. My bad.

The example I used was the ASR-11. It has a stated performance parameter of being able to detect and track a 0 dBsm target at 55 nm, or 102 km. And then I said that means it can track a -10 dBsm target at 32 km and a -30 dBsm target at 3.2 km. Those values I stated are wrong, even as rounded estimates. A more correct rounded estimate would be a -10 dBsm target at about 56 km, a -20 dBsm target at about 31 km, a -30 dBsm target at about 17 km, and a -40 dBsm target would be about 9 km.

Sorry about that, hope this clears up any bad take aways. But my basic point still stands, there is a significant detection range delta between the two aircraft.

T!

 

[DerAdlerIstGelandet]

Not going to start a new thread, but I love this picture. Taken at the Kaneohe Airshow in Hawaii last weekend.

A beautiful aircraft in an amazing photo op. Damn I love this plane.

More from the same airshow.

 

[WARSPITER]

I'm not a great jet "looks" fan as most seem to have a sameness about them but not that one. The first pic is a snorter.

Also, the SU-57 is going to be extremely hard to bring down as it is extremely hard to find, owing to the fact that there
are very few of them in the air. Ten, twelve, or even twenty per year isn't really enough at all when the rest of the system
isn't exactly (from what I've seen) up to scratch.

 

[DerAdlerIstGelandet]

The looks are actually secondary for me.

 

[WARSPITER]

The looks are actually secondary for me.

True. That is the best thing about the pic when you know it works even better than it looks.

 

[Macandy]

I'm not a great jet "looks" fan as most seem to have a sameness about them but not that one. The first pic is a snorter.

Also, the SU-57 is going to be extremely hard to bring down as it is extremely hard to find, owing to the fact that there
are very few of them in the air. Ten, twelve, or even twenty per year isn't really enough at all when the rest of the system
isn't exactly (from what I've seen) up to scratch.

It's 12 years since its first flight… they've built 16, 10 test articles, and 6 notionally'delivery' airframes, and crashed 2.

Its a total bust of a programme they simply can't deliver.
At best, its a slightly lower RCS SU-27 - and considering the SU-27's absolutely huge RCS, that's not a hard ask.

 

[Admiral Beez]

Isn't the Su-57 at the level of the Armata MBT, essentially wunderwaffe that never get past the first trial batches? Is there a naval equivalent? I suppose the Lider class or Arcturus class?

 

[Thumpalumpacus]

I bet few will get built while Russia is spending its brains out in Ukraine.

 

[GrauGeist]

The Moskva class was supposed to be a carrier group killer.

We've all seen just how fearsome and invincible it turned out to be...

 

[Admiral Beez]

I bet few will get built while Russia is spending its brains out in Ukraine.

I'm somehow thinking the best Sukhoi's are made in China. How does the Shenyang J-16 compare with the Sukhoi Su-35?