By: Hotshot
- 29th August 2014 at 07:37Permalink- Edited 1st January 1970 at 01:00
The F-22 is expected to attack with SDBs in high supercruise for the first strikes. I agree that the ability to maneuver is still important. But if the maneuvrability is still quite good, the less time the F-35s spend in enemy airspace the better. Flying at Mach 1.2 instead of Mach 0.9 would reduce the time in enemy airspace by 1/3.
A big concern for intial strikes is enemy fighters. Once the enemy air force has been destroyed, flying in high subsonic wouldn't be that bad, if the F-35s have a good SA and most VHF radars have been destroyed they can just avoid the SAM threats. They would also have more fuel, so more time to find targets.
By: Mercurius
- 29th August 2014 at 10:17Permalink- Edited 1st January 1970 at 01:00
However interview recently with gen Mike Hostage show that
"Both F-22s and F-35s will be spotted at range by low frequency radar."
It shows no such thing. The article based on the Hostage interview that I have seen says that "critics" make this claim. It does not attribute this opinion to Hostage.
By: mig-31bm
- 29th August 2014 at 17:34Permalink- Edited 1st January 1970 at 01:00
It shows no such thing. The article based on the Hostage interview that I have seen says that "critics" make this claim. It does not attribute this opinion to Hostage.
probably, but isn't this part kind of obvious •? , I mean it alway well known that stealth not working at VHF frequency
By: xena
- 29th August 2014 at 19:22Permalink- Edited 1st January 1970 at 01:00
it true that high speed is lot more useful for stealth aircraft than a non stealth one
but it may take alot of time to turn , depend on speed ( if iam not wrong at mach 2 fighter like F-14 and Mig-31 have turn radius about 40-60 km and remember they are optimum to operate at high speed , they can turn better at mach 2 than most fighter ) , not to mention , it really hard to avoid pop up threat when you flying fast
No. High speed is not useful for stealth aircraft. Speed means warm-up of the surfaces and that means stealth is useless because the aircraft can be spotted by IIR-sensors. The hotter the surfaces (the higher the speed) the longer the range it can be spotted by IIR-sensors.
A stealth fighter is stealth when it doses not emit any radiation. No radar, no ECM, no heat radiation, no communication...
By: Mercurius
- 29th August 2014 at 21:04Permalink- Edited 1st January 1970 at 01:00
probably, but isn't this part kind of obvious •? , I mean it alway well known that stealth not working at VHF frequency
There is no 'probably' - To the best of my knowledge, Hostage made no such statement. In the article I read, it is the journalist who is making the statement, not Hostage.
"Widely believed" might be more accurate than "well known" in terms of the usefulness of stealth at VHF frequencies. The degree to which the effectiveness of low-observable technology is reduced at VHF frequencies has been the subject of much speculation, but no-one recognised as an authority on low-observable technology has made any definitive statement on the subject.
By: FBW
- 30th August 2014 at 07:45Permalink- Edited 1st January 1970 at 01:00
No. High speed is not useful for stealth aircraft. Speed means warm-up of the surfaces and that means stealth is useless because the aircraft can be spotted by IIR-sensors. The hotter the surfaces (the higher the speed) the longer the range it can be spotted by IIR-sensors.
A stealth fighter is stealth when it doses not emit any radiation. No radar, no ECM, no heat radiation, no communication...
In the first generation of "stealth" that may have been true. Newer fighters designed for LO use the fuel as a heat dump, comms/datalinks that are directed (MADL) etc., LPI radar that jumps frequencies, and passive detection that was not possible with the first generation of Low Observable fighters. In theory, engineers have tried to solve the problems that you have stated, to what degree they have been successful is a matter of conjecture and not likely to be open source information.
By: Hotshot
- 30th August 2014 at 08:15Permalink- Edited 1st January 1970 at 01:00
And the F-35 is not a blackbird either...
Also, the F-35s would anyways probably try to enter enemy airspace at full or almost full mil trust at mach 0.9+. And whether the F-35 is at full mil thrust at mach 0.95 or at mach 1.2 makes no difference in thrust output, so no difference in IR signature due to the engine.
A supercruising F-35 at mach 1.2 may have a somewhat higher IR signature, but detection range for a IR source is proportional to the square root of the distance. So if a supercruising F-35 at mach 1.2 has say 20-25% more IR signature, it will be detected 10-12% further, which doesn't make much difference.
As for going through the transonic regime, using the full afterburner for about 1 minute from mach 0.8 to mach 1.2 may not be the only possibility. Instead, the plane can accelerate to mach 0.95 at full mil thrust, climb 10000 feet, and accelerate during the dive. F-16s are said to be able to reach mach 1.1 when diving. The F-35 may have to use its afterburner at 50% for like 30 seconds during the dive to get to mach 1.2, but not much more.
By: xena
- 30th August 2014 at 17:40Permalink- Edited 1st January 1970 at 01:00
In the first generation of "stealth" that may have been true. Newer fighters designed for LO use the fuel as a heat dump, comms/datalinks that are directed (MADL) etc., LPI radar that jumps frequencies, and passive detection that was not possible with the first generation of Low Observable fighters. In theory, engineers have tried to solve the problems that you have stated, to what degree they have been successful is a matter of conjecture and not likely to be open source information.
You can not fool physics. Higher speed means friction and friction means heat. Heat must be discharged somewhere. If you keep the heat inside the whole aircraft will radiate heat or it will overheat with all it's high tech inside. This is insane for modern aircrafts. This means you have to get rid of the heat and this can be gathered by IR-sensors. Nothing radiating is invisible. Even LPI radar you can spot with modern latest technology and sensitive broad band ESM gear. If your opponent knows you are there, but he doesn't know where, he can take adequate measures to spot you. For example switch on bistatic/multistatic radars, long wavelength radars and EO sensors. IMHO even today a real stealth aircraft is an absolute silence aircraft with no radiations and no heat footprint.
By: FBW
- 30th August 2014 at 18:45Permalink- Edited 1st January 1970 at 01:00
You can not fool physics. Higher speed means friction and friction means heat. Heat must be discharged somewhere. If you keep the heat inside the whole aircraft will radiate heat or it will overheat with all it's high tech inside. This is insane for modern aircrafts. This means you have to get rid of the heat and this can be gathered by IR-sensors. Nothing radiating is invisible. Even LPI radar you can spot with modern latest technology and sensitive broad band ESM gear. If your opponent knows you are there, but he doesn't know where, he can take adequate measures to spot you. For example switch on bistatic/multistatic radars, long wavelength radars and EO sensors. IMHO even today a real stealth aircraft is an absolute silence aircraft with no radiations and no heat footprint.
By: obligatory
- 30th August 2014 at 18:53Permalink- Edited 1st January 1970 at 01:00
using fuel as a heat sink may cause the unwanted effect of transforming part of the fuel into dead weight
that can not be used for propulsion,
like mig-21 was stuck with part for balance purpose
-less time airborne, -less usable fuel fraction
By: Tu22m
- 30th August 2014 at 21:24Permalink- Edited 1st January 1970 at 01:00
using fuel as a heat sink may cause the unwanted effect of transforming part of the fuel into dead weight
that can not be used for propulsion,
like mig-21 was stuck with part for balance purpose
-less time airborne, -less usable fuel fraction
Using fuel to dump heat is pretty old stuff. It is described pretty well here:
By: mig-31bm
- 31st August 2014 at 07:49Permalink- Edited 1st January 1970 at 01:00
No. High speed is not useful for stealth aircraft. Speed means warm-up of the surfaces and that means stealth is useless because the aircraft can be spotted by IIR-sensors. The hotter the surfaces (the higher the speed) the longer the range it can be spotted by IIR-sensors.
A stealth fighter is stealth when it doses not emit any radiation. No radar, no ECM, no heat radiation, no communication...
that is wrong
for stealth fighter now , they still have radar but LPI radar , they obviously have heat radiation because they moving through the air
and spotted by IIR sensor doesnt mean much if you cant target it ( limit by the LRF range about 40-60 km ) so fast speed could be useful for stealth fighter if they was trying to run away
By: mig-31bm
- 31st August 2014 at 07:51Permalink- Edited 1st January 1970 at 01:00
There is no 'probably' - To the best of my knowledge, Hostage made no such statement. In the article I read, it is the journalist who is making the statement, not Hostage.
"Widely believed" might be more accurate than "well known" in terms of the usefulness of stealth at VHF frequencies. The degree to which the effectiveness of low-observable technology is reduced at VHF frequencies has been the subject of much speculation, but no-one recognised as an authority on low-observable technology has made any definitive statement on the subject.
how about F-117 cased , and the resonant effect at VHF frequency , isnt that the reason why all military force design modern low frequency radar to detect stealth fighter
By: mig-31bm
- 31st August 2014 at 07:55Permalink- Edited 1st January 1970 at 01:00
You can not fool physics. Higher speed means friction and friction means heat. Heat must be discharged somewhere. If you keep the heat inside the whole aircraft will radiate heat or it will overheat with all it's high tech inside. This is insane for modern aircrafts. This means you have to get rid of the heat and this can be gathered by IR-sensors. Nothing radiating is invisible. Even LPI radar you can spot with modern latest technology and sensitive broad band ESM gear. If your opponent knows you are there, but he doesn't know where, he can take adequate measures to spot you. For example switch on bistatic/multistatic radars, long wavelength radars and EO sensors. IMHO even today a real stealth aircraft is an absolute silence aircraft with no radiations and no heat footprint.
AESA radar cannot be detected by ESM not only because it is low power beam but also because it transmit in unpredictable pattern thus ESM system cant recognize it from background noise
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By: obligatory
- 31st August 2014 at 09:34Permalink- Edited 1st January 1970 at 01:00
AESA radar cannot be detected by ESM not only because it is low power beam but also because it transmit in unpredictable pattern thus ESM system cant recognize it from background noise
wow, thats like double guarantee that AESA cant get detected isnt it ?
By: Mercurius
- 31st August 2014 at 12:04Permalink- Edited 1st January 1970 at 01:00
how about F-117 cased , and the resonant effect at VHF frequency , isnt that the reason why all military force design modern low frequency radar to detect stealth fighter
There is indeed likely to be a resonant effect and VHF frequencies, but it would be naive to assume that this has been ignored by engineers involved in designing low-observable aircraft and missiles.
There is, to the best of my knowledge, nothing in the public domain on low-observable techniques for use against VHF radar. However, at a recent defence exhibition, I saw a document (not in the public domain) that indicates that such techniques exist and have been fielded.
While some Russian companies do cite a range capability against the F-117 for some of their recent VHF radars, the fact that the US do not make their low-observable aircraft available to these companies for the purpose of radar tracking trials, we must assume that these claimed performance figures are little more than theoretical estimates based on Russian estimates of the F-117's radar cross section.
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By: lukos
- 31st August 2014 at 13:05Permalink- Edited 1st January 1970 at 01:00
It's not so much the resonant effect, it's just that the RAM doesn't work terribly well in the low band below 3GHz.
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By: lukos
- 31st August 2014 at 13:10Permalink- Edited 1st January 1970 at 01:00
wow, thats like double guarantee that AESA cant get detected isnt it ?
It can be detected but it's more difficult, and very difficult to use more complicated precision detection on it, like interferometry, and I don't see any way of effectively jamming it without either telepathy or espionage to steal the frequency swapping algorithm.
By: mig-31bm
- 31st August 2014 at 17:10Permalink- Edited 1st January 1970 at 01:00
There is indeed likely to be a resonant effect and VHF frequencies, but it would be naive to assume that this has been ignored by engineers involved in designing low-observable aircraft and missiles.
There is, to the best of my knowledge, nothing in the public domain on low-observable techniques for use against VHF radar. However, at a recent defence exhibition, I saw a document (not in the public domain) that indicates that such techniques exist and have been fielded.
While some Russian companies do cite a range capability against the F-117 for some of their recent VHF radars, the fact that the US do not make their low-observable aircraft available to these companies for the purpose of radar tracking trials, we must assume that these claimed performance figures are little more than theoretical estimates based on Russian estimates of the F-117's radar cross section.
one technique that I have heard of is to increase the size of the object ( but that only work for big aircraft)
I don't know what kind of tech you reffer about but it kind of unlikely that f-22 and f-35 have such technology in them even if they exist because these 2 aircraft was designed a long time ago
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By: Hotshot - 29th August 2014 at 07:37 Permalink - Edited 1st January 1970 at 01:00
The F-22 is expected to attack with SDBs in high supercruise for the first strikes. I agree that the ability to maneuver is still important. But if the maneuvrability is still quite good, the less time the F-35s spend in enemy airspace the better. Flying at Mach 1.2 instead of Mach 0.9 would reduce the time in enemy airspace by 1/3.
A big concern for intial strikes is enemy fighters. Once the enemy air force has been destroyed, flying in high subsonic wouldn't be that bad, if the F-35s have a good SA and most VHF radars have been destroyed they can just avoid the SAM threats. They would also have more fuel, so more time to find targets.
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By: Mercurius - 29th August 2014 at 10:17 Permalink - Edited 1st January 1970 at 01:00
It shows no such thing. The article based on the Hostage interview that I have seen says that "critics" make this claim. It does not attribute this opinion to Hostage.
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By: mig-31bm - 29th August 2014 at 17:34 Permalink - Edited 1st January 1970 at 01:00
probably, but isn't this part kind of obvious •? , I mean it alway well known that stealth not working at VHF frequency
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By: xena - 29th August 2014 at 19:22 Permalink - Edited 1st January 1970 at 01:00
No. High speed is not useful for stealth aircraft. Speed means warm-up of the surfaces and that means stealth is useless because the aircraft can be spotted by IIR-sensors. The hotter the surfaces (the higher the speed) the longer the range it can be spotted by IIR-sensors.
A stealth fighter is stealth when it doses not emit any radiation. No radar, no ECM, no heat radiation, no communication...
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By: Mercurius - 29th August 2014 at 21:04 Permalink - Edited 1st January 1970 at 01:00
There is no 'probably' - To the best of my knowledge, Hostage made no such statement. In the article I read, it is the journalist who is making the statement, not Hostage.
"Widely believed" might be more accurate than "well known" in terms of the usefulness of stealth at VHF frequencies. The degree to which the effectiveness of low-observable technology is reduced at VHF frequencies has been the subject of much speculation, but no-one recognised as an authority on low-observable technology has made any definitive statement on the subject.
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By: FBW - 30th August 2014 at 07:45 Permalink - Edited 1st January 1970 at 01:00
In the first generation of "stealth" that may have been true. Newer fighters designed for LO use the fuel as a heat dump, comms/datalinks that are directed (MADL) etc., LPI radar that jumps frequencies, and passive detection that was not possible with the first generation of Low Observable fighters. In theory, engineers have tried to solve the problems that you have stated, to what degree they have been successful is a matter of conjecture and not likely to be open source information.
Posts: 1,123
By: Hotshot - 30th August 2014 at 08:15 Permalink - Edited 1st January 1970 at 01:00
And the F-35 is not a blackbird either...
Also, the F-35s would anyways probably try to enter enemy airspace at full or almost full mil trust at mach 0.9+. And whether the F-35 is at full mil thrust at mach 0.95 or at mach 1.2 makes no difference in thrust output, so no difference in IR signature due to the engine.
A supercruising F-35 at mach 1.2 may have a somewhat higher IR signature, but detection range for a IR source is proportional to the square root of the distance. So if a supercruising F-35 at mach 1.2 has say 20-25% more IR signature, it will be detected 10-12% further, which doesn't make much difference.
As for going through the transonic regime, using the full afterburner for about 1 minute from mach 0.8 to mach 1.2 may not be the only possibility. Instead, the plane can accelerate to mach 0.95 at full mil thrust, climb 10000 feet, and accelerate during the dive. F-16s are said to be able to reach mach 1.1 when diving. The F-35 may have to use its afterburner at 50% for like 30 seconds during the dive to get to mach 1.2, but not much more.
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By: xena - 30th August 2014 at 17:40 Permalink - Edited 1st January 1970 at 01:00
You can not fool physics. Higher speed means friction and friction means heat. Heat must be discharged somewhere. If you keep the heat inside the whole aircraft will radiate heat or it will overheat with all it's high tech inside. This is insane for modern aircrafts. This means you have to get rid of the heat and this can be gathered by IR-sensors. Nothing radiating is invisible. Even LPI radar you can spot with modern latest technology and sensitive broad band ESM gear. If your opponent knows you are there, but he doesn't know where, he can take adequate measures to spot you. For example switch on bistatic/multistatic radars, long wavelength radars and EO sensors. IMHO even today a real stealth aircraft is an absolute silence aircraft with no radiations and no heat footprint.
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By: FBW - 30th August 2014 at 18:45 Permalink - Edited 1st January 1970 at 01:00
Which is why the F-22,35 use fuel as a heat sink then burning it. I would say that engineers are well aware of the thermal issues and are already looking at improvements in thermal management. http://aviationweek.com/awin/afrl-s-invent-program-tackles-aircraft-system-efficiency
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By: obligatory - 30th August 2014 at 18:53 Permalink - Edited 1st January 1970 at 01:00
using fuel as a heat sink may cause the unwanted effect of transforming part of the fuel into dead weight
that can not be used for propulsion,
like mig-21 was stuck with part for balance purpose
-less time airborne, -less usable fuel fraction
Posts: 1,149
By: Tu22m - 30th August 2014 at 21:24 Permalink - Edited 1st January 1970 at 01:00
Using fuel to dump heat is pretty old stuff. It is described pretty well here:
http://books.google.se/books?id=ZTTlAwAAQBAJ&lpg=SA2-PA77&ots=_csIZVpjyY&dq=using%20fuel%20as%20cooling%20radar&hl=sv&pg=SA2-PA77#v=onepage&q&f=false
Oh, did I just prove another of the "only in F35™"-features as being decades old and not unique at all? ;)
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By: mig-31bm - 31st August 2014 at 07:49 Permalink - Edited 1st January 1970 at 01:00
that is wrong
for stealth fighter now , they still have radar but LPI radar , they obviously have heat radiation because they moving through the air
and spotted by IIR sensor doesnt mean much if you cant target it ( limit by the LRF range about 40-60 km ) so fast speed could be useful for stealth fighter if they was trying to run away
Posts: 2,014
By: mig-31bm - 31st August 2014 at 07:51 Permalink - Edited 1st January 1970 at 01:00
how about F-117 cased , and the resonant effect at VHF frequency , isnt that the reason why all military force design modern low frequency radar to detect stealth fighter
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By: mig-31bm - 31st August 2014 at 07:55 Permalink - Edited 1st January 1970 at 01:00
actually they have managed to make a tank invisible in infrared
http://www.huffingtonpost.co.uk/2014/03/31/pl-01-stealth-tank_n_5061795.html
AESA radar cannot be detected by ESM not only because it is low power beam but also because it transmit in unpredictable pattern thus ESM system cant recognize it from background noise
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By: obligatory - 31st August 2014 at 09:34 Permalink - Edited 1st January 1970 at 01:00
wow, thats like double guarantee that AESA cant get detected isnt it ?
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By: Mercurius - 31st August 2014 at 12:04 Permalink - Edited 1st January 1970 at 01:00
There is indeed likely to be a resonant effect and VHF frequencies, but it would be naive to assume that this has been ignored by engineers involved in designing low-observable aircraft and missiles.
There is, to the best of my knowledge, nothing in the public domain on low-observable techniques for use against VHF radar. However, at a recent defence exhibition, I saw a document (not in the public domain) that indicates that such techniques exist and have been fielded.
While some Russian companies do cite a range capability against the F-117 for some of their recent VHF radars, the fact that the US do not make their low-observable aircraft available to these companies for the purpose of radar tracking trials, we must assume that these claimed performance figures are little more than theoretical estimates based on Russian estimates of the F-117's radar cross section.
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By: lukos - 31st August 2014 at 13:05 Permalink - Edited 1st January 1970 at 01:00
It's not so much the resonant effect, it's just that the RAM doesn't work terribly well in the low band below 3GHz.
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By: lukos - 31st August 2014 at 13:10 Permalink - Edited 1st January 1970 at 01:00
It can be detected but it's more difficult, and very difficult to use more complicated precision detection on it, like interferometry, and I don't see any way of effectively jamming it without either telepathy or espionage to steal the frequency swapping algorithm.
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By: mig-31bm - 31st August 2014 at 17:03 Permalink - Edited 1st January 1970 at 01:00
in theory you could if you know the partten but I think that would be like guessing WPA2 WiFi password
Posts: 2,014
By: mig-31bm - 31st August 2014 at 17:10 Permalink - Edited 1st January 1970 at 01:00
one technique that I have heard of is to increase the size of the object ( but that only work for big aircraft)
I don't know what kind of tech you reffer about but it kind of unlikely that f-22 and f-35 have such technology in them even if they exist because these 2 aircraft was designed a long time ago