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Post by oldpop2000 on Oct 29, 2013 11:40:03 GMT -6
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Post by steel selachian on Nov 12, 2013 20:37:41 GMT -6
I'm not sure if the B-2 "isn't as stealthy;" it's more that it's a second-gen design that is a real PIB to maintain - to the point where you need to have climate-controlled hangars; you can't just operate the things out of any airbase in the world or leave it parked on the flight line. I wonder if Northrup Grummann has considered simply revamping the basic B-2 design for this competition with technology such as new RAM coatings, engines, and sensors. The idea is supposed to be to churn these things out at about $500 mil a pop. Well, back in mid-1990s dollars $550 mil was about the flyaway cost of a proposed second-run B-2A. That doesn't leave a lot of room for devising new bells and whistles.
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Post by oldpop2000 on Nov 12, 2013 20:51:09 GMT -6
I'm not sure if the B-2 "isn't as stealthy;" it's more that it's a second-gen design that is a real PIB to maintain - to the point where you need to have climate-controlled hangars; you can't just operate the things out of any airbase in the world or leave it parked on the flight line. I wonder if Northrup Grummann has considered simply revamping the basic B-2 design for this competition with technology such as new RAM coatings, engines, and sensors. The idea is supposed to be to churn these things out at about $500 mil a pop. Well, back in mid-1990s dollars $550 mil was about the flyaway cost of a proposed second-run B-2A. That doesn't leave a lot of room for devising new bells and whistles. I believe that the USAF simply wants to be able to retire the B-1Bs and B-52s as soon as possible. I also believe that they maybe considering optional manning, meaning that this plane maybe a general purpose, overgrown stealth UCAV. I don't see the B-2 design being used at all. I can make a bird cheaper if I can remove the crew, believe me. I can remove the redundancy in many systems, I can improve G limits because I don't have to consider human frailties and I don't need cockpits and the attendant equipment necessary to make pilots safe. If I can make the bird modular and simply replace the front nose with a nose that contains the cockpit then I can still save bucks. Everything is classified so all articles are speculation.
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Post by steel selachian on Nov 26, 2013 18:05:30 GMT -6
Figured we could throw this into the mix: www.aviationweek.com/Article.aspx?id=/article-xml/AW_11_25_2013_p22-638264.xmlPersonally, I don't buy it. If you can nail an ICBM warhead or one of the supersonic Russian ASMs with a SAM, you can sure as hell nail a Mach 3-4 aircraft flying at high altitude. All you need to do is pick it up at enough of a distance - not very hard - and put something in front of it; physics will take care of the rest.
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Post by oldpop2000 on Nov 26, 2013 19:16:32 GMT -6
Figured we could throw this into the mix: www.aviationweek.com/Article.aspx?id=/article-xml/AW_11_25_2013_p22-638264.xmlPersonally, I don't buy it. If you can nail an ICBM warhead or one of the supersonic Russian ASMs with a SAM, you can sure as hell nail a Mach 3-4 aircraft flying at high altitude. All you need to do is pick it up at enough of a distance - not very hard - and put something in front of it; physics will take care of the rest. I can't disagree with their logic because I've watched and tracked SR-71s with a height finder and we only got three to five paints on the target before it was gone. We knew where he had taken off from, his course and where he was headed and yet, we could only get a few good paints at the top of the scope before he had disappeared. And he hadn't achieved full speed yet, since he had just taken off from over the mountain at Beale AFB. No one, that I remember from those days ever got close to shooting down an SR-71 due to its stealth but more importantly its speed. Everything depends on how fast and accurate your search and tracking radars are but more importantly your computers. You will need to launch ASAP to prevent a tail chase as explained in the article. To boost a heavy missile in a near vertical climb to intercept altitude requires at least two stages and good prediction as to where your target will be when the missile arrives. ICBM's are not that hard to detect or track as they follow a reverse parabolic trajectory and it is mathematical and predictable. Once you get one or two good fixes on it, you can easily predict where it will be at any one moment in time.
Believe me, it can be done. The Mach 6 bomber following a human designated and guided path is far more difficult to predict and that means it is much harder to kill. Speed has always been life in the world of aircraft, take my word for that.
I wish I could tell you more details, but alas I am bound by the papers I signed many years ago. I hope you understand, they aren't kidding. It works.
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Post by steel selachian on Dec 1, 2013 21:10:13 GMT -6
As I recall, the SR-71 wasn't particularly stealthy; while it did have some RCS-reduction features it still had an RCS of about 10 square meters from head-on. More importantly, the exhaust plume left a big fat radar signature when the plane was going full tilt.
I'll grant that radar detection and interception are subjects you know a lot about; I just question the wisdom of placing all your chips on the bet that speed alone will save you. I assume that the SR-71 mostly went up against the SA-2 and SA-5 systems during its overflights; it may have encountered the early marks of the SA-10 late in its career. There have been a lot of advances in radar, missiles, and computers over the past thirty years, and speeds of Mach 4 or above may not give the aircraft as much of an edge.
On a more logistical note, the SR-71 had to overcome a load of technical hurdles that we'd have a hard time doing better with now, such as airframe expansion. It's one thing to zip over a target and take pictures; it's another when you have to bomb it. Will the aircraft have to slow down to open the weapons bay and release ordnance? What will its combat radius be, and how dependent is it on tanker support? Will it need to use a separate stock of jet fuel, like the SR-71's JP-7? Will it have any capability to loiter in a combat area? What kind of operational loss rate should we expect? Remember that out of 32 SR-71s, 12 were written off in accidents.
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Post by steel selachian on Dec 1, 2013 21:20:18 GMT -6
Bah, double post error.
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Post by oldpop2000 on Dec 2, 2013 8:34:42 GMT -6
As I recall, the SR-71 wasn't particularly stealthy; while it did have some RCS-reduction features it still had an RCS of about 10 square meters from head-on. More importantly, the exhaust plume left a big fat radar signature when the plane was going full tilt. I'll grant that radar detection and interception are subjects you know a lot about; I just question the wisdom of placing all your chips on the bet that speed alone will save you. I assume that the SR-71 mostly went up against the SA-2 and SA-5 systems during its overflights; it may have encountered the early marks of the SA-10 late in its career. There have been a lot of advances in radar, missiles, and computers over the past thirty years, and speeds of Mach 4 or above may not give the aircraft as much of an edge. On a more logistical note, the SR-71 had to overcome a load of technical hurdles that we'd have a hard time doing better with now, such as airframe expansion. It's one thing to zip over a target and take pictures; it's another when you have to bomb it. Will the aircraft have to slow down to open the weapons bay and release ordnance? What will its combat radius be, and how dependent is it on tanker support? Will it need to use a separate stock of jet fuel, like the SR-71's JP-7? Will it have any capability to loiter in a combat area? What kind of operational loss rate should we expect? Remember that out of 32 SR-71s, 12 were written off in accidents. The SR-71 did have some technical problems that had to be overcome. It was originally conceived as a high speed, high altitude strategic reconnaissance aircraft, and no thought of dropping bombs ever entered anyone's mind. It did have rudimentary stealthy features like the radar absorbing material coating, laminate plastic leading edge and trailing edge, fuselage lip, engine cones, etc. Even the method of embedding the engines in the wings was an early attempt to reduce the IR signature. The reduced RCS, its altitude and high speed were its protection for the time period. And I stress the time period. You really can't drop bombs from 125,000 feet and traveling at Mach 3+. Not unless you intend to launch the out the tail backwards like the Vigilante.
What stealth, and there is more to stealth than radar avoidance, does is reduce the detection range of radars. Example; take a compass and draw circles overlapping on a plain piece of paper. This is how a radar net is configured. Now, take the compass and draw those same circles but reduce the diameter by 1/3. Now there are gaps, and stealth aircraft fly through those gaps. The faster you can ingress through the gaps to the target and egress, the safer you are going to be. This is how speed is going to help you be more stealthy, it will get you through the gaps faster. We will have to see where this project goes.
www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/6581/The-SR-71s-Replacement-The-SR-72.aspx gizmodo.com/5511236/the-thrill-of-flying-the-sr+71-blackbird
www.blackbirds.net/sr71/fallblackbird.html
www.dept.aoe.vt.edu/~mason/Mason_f/ConfigAeroStealth.pdf
All in all, you can't outrun the speed of light, but what you can do, is move so fast that the opponents integrated air defense system cannot react to your movements. Keep in mind, that IADs are human functions, and move at our speed. Remember the U-2? I saw it take off on a mission from Laughlin AFB many years ago. The loss of that bird was directly due to its lack of speed and altitude. This is why the CIA and USAF got together and developed the SR-71. Stealth reduces reaction times of IADs, that's how speed is stealthy.
EDIT: Just for you to examine - My radar sets
www.radomes.org/museum/equip/radarequip.php?link=fps-26.html
radomes.org/museum/equip/fps-6.html
www.radomes.org/museum/equip/fps-24.html
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Post by oldpop2000 on Dec 4, 2013 9:16:14 GMT -6
Just a note about the SR-71 RCS. Using various official engineering sources, the RCS of the SR-71 was the size of a piper cub. It was lower than the B-1 bomber built about twenty years later. It was a stealthy bird.
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Post by williammiller on Dec 4, 2013 13:30:02 GMT -6
IIRC a caesium-based compound was also dumped into the exhaust of the SR-71 to reduce the radar signature of the planes exhaust plume as the plume was a significant contributor to the SR-71 RCS.
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Post by oldpop2000 on Dec 4, 2013 13:49:53 GMT -6
IIRC a caesium-based compound was also dumped into the exhaust of the SR-71 to reduce the radar signature of the planes exhaust plume as the plume was a significant contributor to the SR-71 RCS. The fuel was JP-7 and one additive was a cesium compound with the official name of A-50 which reduced heat signature.
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Post by sirchaos on Dec 6, 2013 11:42:15 GMT -6
Speaking of plumes and their radar (not to mention infrared and visual) signature... how about building a plane that uses its engines only before and after the hairy part of the mission, and *glides* through enemy radar coverage? That´ll take care of the exhaust plume, and if it isn´t detected, a recon plane at least would not necessarily need to maneuver.
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Post by oldpop2000 on Dec 6, 2013 12:58:47 GMT -6
Speaking of plumes and their radar (not to mention infrared and visual) signature... how about building a plane that uses its engines only before and after the hairy part of the mission, and *glides* through enemy radar coverage? That´ll take care of the exhaust plume, and if it isn´t detected, a recon plane at least would not necessarily need to maneuver. Hi Christian: That is how the U-2 spy plane operates, it accelerates on take-off, climbs to its cruising altitude and then the engine is shut down and now it glides on its high aspect wings. Each wing tip has a device named a pogo which falls off on take-off. When she lands and taxi's, two truck, one on each side have to pull along side, and attach the pogos, then it can slow down. The problem is that with the high aspect wing, you cannot exceed certain speeds, designated as " not to exceed velocity". She was not stealthy, due to the mirror like qualities of wings. One of sources of reflection is specular reflection and that is the primary source that designers have to overcome. The leading and trailing edges cause a source titled diffraction. On some aircraft, like those with long wings, it is a major source of RCS. The nose cone is another diffractive source. Engine inlets and cockpits also. The U-2s stall speed was 10 knots less than the cruising speed, which makes for fun flying. One big advantage of the U-2 over the SR-71 is loiter time. The U-2 can stay over the target area for hours, the SR-71 can't. I suspect that UCAV's and drones have taken over much of this work.
So, enter the SR-71. It was stealthy, extremely fast with good flight characteristics and high altitude. Yes, I have seen both take off, one at Laughlin AFB and one at Fallon NAS.
Now, to the general question that you had. In military aviation, speed is life. Speed reduces the opponents reaction time and gives the attacker a chance to ingress to the target, acquire, lock-on and launch his attack. Speed also allows the attacker an egress time. All integrated air defense systems are human controlled. They acquire a target, identify the target, track the target then a human makes the decision how to attack the target: will it be missiles, manned aircraft or anti-aircraft weaponry. In the arena of strategic reconnaissance, speed and altitude are critical to the completion of these missions. Manned strategic reconnaissance gives the user flexibility in surveying areas of the opponent that a satellite doesn't have. If a hot spot in the world occurs, but no reconnaissance is available through satellites, then the manned or unmanned strategic reconnaissance package is the best game in town. Many times its used because of its ability to be specific in its aiming point for its sensors.
As to the concept of "gliding", gliding doesn't work unless you have a high aspect( long wing with short span) just like a glider. However, that type of wing cannot be used in above Mach 1 flight conditions. In fact, it isn't used much beyond 300 knots. Swept wings are the only wing design that can carry an aircraft through the sound barrier or near it safely. That type of wing doesn't glide well, in fact, it has the glide angle of brick, as we used to say. Nice thought but it has been tried.
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Post by steel selachian on Dec 6, 2013 18:01:34 GMT -6
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Post by oldpop2000 on Dec 6, 2013 20:06:18 GMT -6
The comment "sailplane-like" means an efficient wing and a light structure. This is why laminar flow is so important. A laminar flow wing is thinner, the leading edge is more pointed and its upper and lower surfaces are nearly symmetrical. Based on my investigations over the years, the thickest part of the wing occurs at 50% chord, not 25% as in conventional designs. This means that the flow of air, which generates the lift is maintain over more of the wing and drag is reduced. All this says is that a laminar flow wing is more efficient and uses less forward energy to generate lift. The chord is a line from the leading edge through the wing to the trailing edge. This distance is the mean chord. The first aircraft to have a laminar flow wing was the P-51 Mustang. The surface has to be absolutely flush, no wing panels out of joint, no Zsus fasteners sticking up, nothing. Most modern aircraft that use this kind of wing, have very exacting wing tolerances. The B-24 wing was laminar, but no one knew it, it was just a very efficient wing in the tunnels.
So, the comment means essentially a very efficient wing and a light air vehicle: I.E. like a sailplane. So, no it isn't going to glide like a sailplane.
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