gadeshi
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Combat Aircraft technology and Evolution
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bhramos
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These are not combat aircraft, Please go through the first page of this thread ..
gadeshi
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NPO Saturn has mastered aero engine parts from Cobalt alloys using additive tech (3D-printing):
https://sdelanounas.ru/blogs/92926/
https://sdelanounas.ru/blogs/92926/
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Track-before-detect
OK. What the F?
My understanding: It looks to me like they are using background signals and variations in clutter-return to identify a shifting target. But does this not make the system especially vulnerable to spoof, ECM and mimics? Its like a double-edged sword. The more you try to use this technique, the harder it becomes to discern anything useful. If your enemy is prepared for this stuff, its likely going to screw you up more than when you dont use this tech. But I could be wrong about how this works.
What exactly is this tech and what are the bottlenecks in its implementation?
OK. What the F?
Would appreciate if someone could explain this tech and if its viable yet. Also, to me it seems that it will appear in ground-based radars before it appears in Fighters.
My understanding: It looks to me like they are using background signals and variations in clutter-return to identify a shifting target. But does this not make the system especially vulnerable to spoof, ECM and mimics? Its like a double-edged sword. The more you try to use this technique, the harder it becomes to discern anything useful. If your enemy is prepared for this stuff, its likely going to screw you up more than when you dont use this tech. But I could be wrong about how this works.
What exactly is this tech and what are the bottlenecks in its implementation?
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Wait does this thing actually has a chance of working.
And this is the 6th gen Iranian super fighter of the hell.....
Bahamut
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What I understand is that since the angle at which we look at the target changes so there will be a change in RCS and with that change we can track the target
@StealthFlanker Can you explain the concept
Thanks in advance
StealthFlanker
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When a radar scan a volume of space, it receives not only the reflection from targets but also reflection from natural objects such as birds, insects, ground, background radiation..etc. To ease the computational process and avoid cluttered or whiten the whole screen, most radars apply a threshold known as the clutter rejection threshold( normally a signal to noise threshold ), if the signal received is weaker than this threshold the radar will not be bothered to measure any characteristics of this signal. The lower your threshold is, the more likely you detect target with lower radar cross section, but at the same time you will also have to process alot more information.
You can imagine the radar see the reflection from a volume of space like the photo below, every spike represents a reflection but the radar will only measure the Doppler shift, bearing, and delay of that very tall spike and only that spike will be declared to the operator. In other words, a radar with rejection threshold set to reject birds will not be able to detect a target with a bird like reflection regardless of how high or how fast that target flies.
Track before detect is a technique where the radar processor doesn't apply any threshold and instead will measure the Doppler shift, bearing and delay of every single reflection and recorded it.Overtime, it can pick out which one is the real target. Because the radar does not represent all these reflections that it track and detects to the operator (otherwise he will be overwhelmed with a screen full of random dot), in a sense the radar track the target without the operator "detecting the target", that where the name come from. Because Track before detect doesn't have a threshold, it can detect targets with much lower signal to noise ratio condition.
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scatterStorm
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If what you are telling is true, than this would definitely would need a good power to gain ratio, but could also be aerial version as well, considering how radar tech is been improving these days.
gadeshi
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Yes, but you forgot pulse summarising and detect probability that also can be lowered by the proper signal processing and real time computations.When a radar scan a volume of space, it receives not only the reflection from targets but also reflection from natural objects such as birds, insects, ground, background radiation..etc. To ease the computational process and avoid cluttered or whiten the whole screen, most radars apply a threshold known as the clutter rejection threshold( normally a signal to noise threshold ), if the signal received is weaker than this threshold the radar will not be bothered to measure any characteristics of this signal. The lower your threshold is, the more likely you detect target with lower radar cross section, but at the same time you will also have to process alot more information.
You can imagine the radar see the reflection from a volume of space like the photo below, every spike represents a reflection but the radar will only measure the Doppler shift, bearing, and delay of that very tall spike and only that spike will be declared to the operator. In other words, a radar with rejection threshold set to reject birds will not be able to detect a target with a bird like reflection regardless of how high or how fast that target flies.
Track before detect is a technique where the radar processor doesn't apply any threshold and instead will measure the Doppler shift, bearing and delay of every single reflection and recorded it.Overtime, it can pick out which one is the real target. Because the radar does not represent all these reflections that it track and detects to the operator (otherwise he will be overwhelmed with a screen full of random dot), in a sense the radar track the target without the operator "detecting the target", that where the name come from. Because Track before detect doesn't have a threshold, it can detect targets with much lower signal to noise ratio condition.
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StealthFlanker
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Don't you mean pulse compression?
I didn't say track before detect is the only way to improve detection probability, i only explain what it is
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A Closer Look at Stealth, Part 5: Nozzles and Exhausts
F-117 Nighthawk
The F-117A Nighthawk was the first U.S. aircraft to use low-observability as its primary means of survivability. The rear of the aircraft sloped from an apex above the cockpit into a broad, flat feature dubbed the “platypus.” The engine exhaust flattened to thin slots 4-6-in. deep and 5-ft. wide, divided horizontally into about a dozen channels. The lower fuselage terminated in a lip extending 8 in. past the exhaust at a slightly upward angle. This was covered in “heat-reflecting” tiles that were cooled by bypass air from the engines. The platypus shielded the hot metal parts while the flattened plume reduced IR intensity from the side and accelerated mixing with ambient air. The extended lip masked the exhaust slot and first 8 in. of plume from below, while the low-emissivity tiles limited IR absorption and emission.
B-2
Buried deep within its flying-wing airframe, the B-2’s engines are prevented from heating the outer surface. The exhaust is cooled by bypass air, including from secondary air intakes, and flattened prior to exiting over the “aft deck”—trenches built of titanium and covered in low-emissivity ceramic tiles. Likely containing magnetic radar-absorbent material (RAM), these extend several feet behind the nozzles, blocking the plume’s core from below and the side. Large chevrons at the end of the engine fairings and aft deck also introduce shed vortices to accelerate mixing with ambient air.
F-22 Raptor
Pratt & Whitney incorporated a number of IR signature-suppression techniques into the F119 engines that power Lockheed Martin’s F-22 Raptor. Aft of the low-pressure turbine are thick, curved vanes that, when looking up the tailpipe, block any direct view of the hot, rotating turbine components. Fuel injectors are integrated into these vanes, replacing the conventional afterburner spray bars and flame holders. The vanes mask the turbine and contain minute holes that introduce cooler air. The exhaust then passes through the F119’s “non-axisymmetric,” or 2D, thrust-vectoring nozzles, which have upper and lower surfaces ending in wedges with blended central edges. These nozzles further mask the engine hot parts while flattening the exhaust plume and generating vortices. Minute holes are evident on their inner surfaces, likely providing bypass air for enhanced cooling.
F135 Engine
In designing the nozzle of the F135 engine that powers the F-35 Joint Strike Fighter, Pratt & Whitney aimed to rival the low signature of the nozzles on its previous F119, while beating it on maintenance costs. The F135 nozzle comprises two overlapping sets of 15 flaps, offset so outer flaps are centered on the gaps between the inner flaps. The inner flaps are thin, have metallic exteriors and straight sides and terminate in inverted “V”s. The sides create rectangular gaps between them with the nozzle fully diverged. The outer flaps, which Pratt calls “tail feathers,” are thicker and covered in tiles with blended facets. They terminate in chevrons that overlap the ends of the inner flaps to create a sawtooth edge. Toward the fuselage, the tiles end in four chevrons and are covered by additional tiles (not attached to the engines in this photo) that terminate fore and aft in chevrons and interlock with adjacent tiles in sawtooth-fashion.
The F135 nozzle likely suppresses IR signature using multiple methods. The trailing-edge chevrons create shed vortices, shortening the plume, while their steeper axial angle likely directs cooler ambient air into the exhaust flowpath. The inner surfaces of both sets of flaps are white and covered in minute holes similar to those on the F119, which might supply cooling air. The space between the tail feathers and the trailing chevrons may also contain ejectors to provide even more cooling air. The tiles and inner flap surfaces are likely composed of low-emissivity, RAM composites.
http://aviationweek.com/defense/clo...les-and-exhausts#slide-0-field_images-1655211
F-117 Nighthawk
The F-117A Nighthawk was the first U.S. aircraft to use low-observability as its primary means of survivability. The rear of the aircraft sloped from an apex above the cockpit into a broad, flat feature dubbed the “platypus.” The engine exhaust flattened to thin slots 4-6-in. deep and 5-ft. wide, divided horizontally into about a dozen channels. The lower fuselage terminated in a lip extending 8 in. past the exhaust at a slightly upward angle. This was covered in “heat-reflecting” tiles that were cooled by bypass air from the engines. The platypus shielded the hot metal parts while the flattened plume reduced IR intensity from the side and accelerated mixing with ambient air. The extended lip masked the exhaust slot and first 8 in. of plume from below, while the low-emissivity tiles limited IR absorption and emission.
B-2
Buried deep within its flying-wing airframe, the B-2’s engines are prevented from heating the outer surface. The exhaust is cooled by bypass air, including from secondary air intakes, and flattened prior to exiting over the “aft deck”—trenches built of titanium and covered in low-emissivity ceramic tiles. Likely containing magnetic radar-absorbent material (RAM), these extend several feet behind the nozzles, blocking the plume’s core from below and the side. Large chevrons at the end of the engine fairings and aft deck also introduce shed vortices to accelerate mixing with ambient air.
F-22 Raptor
Pratt & Whitney incorporated a number of IR signature-suppression techniques into the F119 engines that power Lockheed Martin’s F-22 Raptor. Aft of the low-pressure turbine are thick, curved vanes that, when looking up the tailpipe, block any direct view of the hot, rotating turbine components. Fuel injectors are integrated into these vanes, replacing the conventional afterburner spray bars and flame holders. The vanes mask the turbine and contain minute holes that introduce cooler air. The exhaust then passes through the F119’s “non-axisymmetric,” or 2D, thrust-vectoring nozzles, which have upper and lower surfaces ending in wedges with blended central edges. These nozzles further mask the engine hot parts while flattening the exhaust plume and generating vortices. Minute holes are evident on their inner surfaces, likely providing bypass air for enhanced cooling.
F135 Engine
In designing the nozzle of the F135 engine that powers the F-35 Joint Strike Fighter, Pratt & Whitney aimed to rival the low signature of the nozzles on its previous F119, while beating it on maintenance costs. The F135 nozzle comprises two overlapping sets of 15 flaps, offset so outer flaps are centered on the gaps between the inner flaps. The inner flaps are thin, have metallic exteriors and straight sides and terminate in inverted “V”s. The sides create rectangular gaps between them with the nozzle fully diverged. The outer flaps, which Pratt calls “tail feathers,” are thicker and covered in tiles with blended facets. They terminate in chevrons that overlap the ends of the inner flaps to create a sawtooth edge. Toward the fuselage, the tiles end in four chevrons and are covered by additional tiles (not attached to the engines in this photo) that terminate fore and aft in chevrons and interlock with adjacent tiles in sawtooth-fashion.
The F135 nozzle likely suppresses IR signature using multiple methods. The trailing-edge chevrons create shed vortices, shortening the plume, while their steeper axial angle likely directs cooler ambient air into the exhaust flowpath. The inner surfaces of both sets of flaps are white and covered in minute holes similar to those on the F119, which might supply cooling air. The space between the tail feathers and the trailing chevrons may also contain ejectors to provide even more cooling air. The tiles and inner flap surfaces are likely composed of low-emissivity, RAM composites.
http://aviationweek.com/defense/clo...les-and-exhausts#slide-0-field_images-1655211
gadeshi
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@StealthFlanker, maybe pulse compression, but it will be closer to pulse saturation in Russian.
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Absolutely NOT .
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Where did you get that info? From the troll factory lecturers?
One of the major design purpose for F-22's flat nozzles is to flatten the exhaust air so that it will be spread out more after leaving the nozzles. A more spread out exhaust cools faster than the more concentrated exhaust of round nozzles. The differences in exhaust heat between F-22's flat nozzles and conventional rounded noozles may not be very substantial on short range but it substantially helps mask the IR signature of F-22 over longer ranges.
Another major design purpose for the wedge shape of F-22's nozzle is to minimize its radar signature.
Bahamut
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https://aviation.stackexchange.com/questions/21081/advantages-of-square-over-circular-engine-nozzle
For decreasing IR signature the length of the nozzles have to be longer to allow the cool air to mix. For F 22A it is mainly for rcs.
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Read the Aviationweek magazine article I posted above. That paddle flat nozzles of F-22 is also for IR signature reduction.
Bahamut
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Read carefully , they only thing which indicate the flat design does is mask internal hot engine part which only will be visible if you are behind the aircraft
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It's you who did not read the article well.
"xxx These nozzles further mask the engine hot parts while flattening the exhaust plume and generating vortices. xxx"
A flat exhaust plume spreads the exhaust heat in the atmosphere in a much wider space thus dissipating the heat resulting in cooler exhaust plume than in jets with concentrated (rounded) exhaust plumes.
But as I mentioned earlier, this IR signature reduction scheme makes significant difference on long ranges. On short ranges, it does not make much difference.
Interestingly, from F117, to B-2, to F-22 the exhaust plumes are flattened by flat exhaust nozzles or exits. The F-35 break the mold. This is one reason why observers conclude that at least on the aft section the F-35 is not as stealthy as F-22. But most conclude this is done to reduce cost since the conventional rounded nozzle in F-35 is much cheaper to construct than the more complicated exhausts of previous stealth planes.
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