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Subject: IR Missile Range
displacedjim    1/3/2005 2:30:44 PM
Giving a single "maximum range" value for an IR missile is even less meaningful than it is for a radar guided missile. Two parameters must be considered to find the maximum effective range of the missile assuming the target is within the missile seeker's field-of-view, and the lesser of the two is what determines the maximum effective range: missile kinematic range and seeker lock-on range. If you picture a God's-eye view looking straight down at the target, typical IR seeker performance would place a heart-shaped zone around the target where the seeker can lock-on to the target when the seeker is within that zone and has the target in its field-of-view. Lock-on range from the frontal aspect might be only a few miles, while from dead astern might be 20 miles. This can vary significantly with altitude and weather conditions affecting visibility in the seeker detection spectrum. Note that with older seekers this is relatively independent of target speed, but very dependent on target throttle setting (particularly afterburner). Furthermore, a sudden maneuver could change the target aspect such that what was previously tail-on and within seeker range is now abeam or even head-on and outside of seeker range. Of course, recent seeker advances have greatly improved seeker performance, particularly against the target's forward hemisphere aspect. On the same God's-eye view, missile kinematic range would place an eliptical zone around the target extending primarily ahead of the target where the missile has the kinetic energy to physically arrive at the target when launched toward the target from within this zone. Kinematic range from dead ahead might be 20 miles while from the stern aspect might be only a few miles. This can vary significantly with altitude and weather conditions affecting atmospheric density and hence drag on the missile. Note that this is very dependent on target speed and somewhat dependent on launch aircraft speed. Initial launch aircraft aspect to the target could impose some penalty if it requires significant initial missile course-correction. Furthermore, a sudden maneuver could change the target aspect such that what was previously head-on and within kinematic range is now abeam or even tail-on and subsequently outside of kinematic range. Therefore the maximum effective range of an IR missile is the intersection, or overlap, of these two zones. It tends to look something like a tomato. For AIM-9M/AA-11 class weapons, it ranges roughly from several miles head-on to quite a few miles from the target's 10- and 2-o'clock aspect, and back around to several miles from dead astern. In no case is it more than 10 miles. Barring some significantly improved seeker lock-on ranges, the only way at this time an IR missile could have a maximum effective range much greater than that would require some means of being able to launch the weapon without an initial lock-on to the target and then acquire a LOAL (Lock-On After Launch) once it comes within seeker lock-on range. At that point the missile maximum effective range would be dominated or completely determined by the kinematic range zone. Displacedjim
 
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HJ    RE:IR Missile Range   1/16/2005 1:53:14 AM
I prefer to call the indented portion of an IR missile envelope (or WEZ/LAR) the clevage effect due to IR seeker decreased range due to fuselage masking in the head-on situation. I think you have underestimated your ranges though when Focal Plane Arrays (FPA) are considered. They are really sensitive (brings forth issue of processing all they see though) and do better than you give them credit. But, why state all this in the first place; what are you trying to discuss or is there a question in here somewhere?
 
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displacedjim    RE:IR Missile Range   1/16/2005 10:37:06 PM
I was trying to point out that using maximum kinetic range as a maximum range for an IR missile is misleading, and that typically the effective maximum range will be half the kinetic maximum, or even less--depending on the other factors I mentioned using AIM-9M/AA-11 class weapons as an example. Displacedjim
 
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HJ    RE:IR Missile Range   1/16/2005 11:36:45 PM
Rog. Except the max range in a shooter centered envelope with zero aspect (180 if you are USAF trained) wouldn't be half, only a percentage less and only in the that aspect. Turn the target 10-20 degrees thus exposing the engine plume and the clevage disappears.
 
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displacedjim    RE:IR Missile Range   1/17/2005 1:34:48 AM
Clarification: I meant "...typically the effective maximum range to target at the time of launch will be half the head-on kinetic maximum, or even less..." My post was triggered by an HTMW item that cited the following "maximum ranges": "The Archer has a range of 20-40 kilometers, depending on the version,..." "The Archer clearly had eclipsed the AIM-9L/M Sidewinder, which had a range of 16 kilometers..." "The Python 4, an Israeli IR-homing missile, which also had a helmet-mounted sight, also was outperforming the Sidewinder (15-kilometer range, nearly as much as the Sidewinder..." Displacedjim
 
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HJ    RE:IR Missile Range   1/17/2005 1:56:36 PM
I don't think you can make that kind of generalization about seeker vs kinematic ranges (also have to define altitudes, launch speeds and signature of target as well as aspect). Mid and long wave IR FPAs can really see a long way in most cases. Depends on the type rocket motor as to whether it is a factor of 2. In case of AIM-9X, it is not. In case of other SRMs, LOAL was integrated to allow launch at max effective kinematic range to compensate in much the same that AMRAAM or MICA launches in RF realm without a "lock" and then uses a terminal seeker to pick up the target when targets is estimated to be in seeker range. Simplistic analogy but covers basics.
 
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displacedjim    RE:IR Missile Range   1/20/2005 6:19:23 PM
"I don't think you can make that kind of generalization about seeker vs kinematic ranges (also have to define altitudes, launch speeds and signature of target as well as aspect). Mid and long wave IR FPAs can really see a long way in most cases. Depends on the type rocket motor as to whether it is a factor of 2. In case of AIM-9X, it is not. In case of other SRMs, LOAL was integrated to allow launch at max effective kinematic range to compensate in much the same that AMRAAM or MICA launches in RF realm without a "lock" and then uses a terminal seeker to pick up the target when targets is estimated to be in seeker range. Simplistic analogy but covers basics" -- HJ ---- Thanks, but I clearly was not including AIM-9X or other next-generation IR missiles. As I've said a couple times now, I was addressing an item that called out the Archer, AIM-9M, and Python 4 specifically, and I mentioned the AIM-9M and Archer specifically. Furthermore my rough wag rule of thumb clearly was just that and not meant to be some dogmatic decree--although I am correct in the context of my posts. My initial post did account for the effects of the variables like altitude, target aspect, etc. I also mentioned the effect of LOAL. Thanks for mentioning them again, though, in the context of the latest generation of missiles just now coming into service. They indeed--just as I said they would in the last paragraph of my initial post--go a long way toward increasing the effective range toward the kinematic maximum in all regimes. Displacedjim
 
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HJ    RE:IR Missile Range   4/10/2005 3:40:44 AM
Sorry about tardy reply, Guess I missed your reply somehow. I'm still a little dubious that your original statement can be laid out that simplistically. A couple things keep nagging at me. One sore spot is lumping AIM-9M with R-73/AA-11 and Python 4. AIM-9M can't compete with either in range or off boresight capability (seeker limits, track rate and kinematics). But I think you were trying to highlight the "tomato" effect as you call it so generation of missiles doesn't apply as the tomato shape (I prefer clevage) applies to all generations that have forward quarter capability, BUT I would happier IF you had set the most important conidtion and that is the target must be at zero aspect relative (180 if you use USAF terminology) to seeker, This is called a target centric envelope and it does look like a tomato! But if you start to increase aspect, the engine engine is unmasked and yyou no longer are looking at a tomato. I buy your argument then. Cheers, HJ
 
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displacedjim    RE:IR Missile Range   4/10/2005 10:27:21 PM
I'm not sure what I'm missing. Please spell it out slowly so it gets through all my armchair padding and to my brain. Here's what I said regarding the seeker's view: "If you picture a God's-eye view looking straight down at the target, typical IR seeker performance would place a heart-shaped zone around the target where the seeker can lock-on to the target when the seeker is within that zone and has the target in its field-of-view. Lock-on range from the frontal aspect might be only a few miles, while from dead astern might be 20 miles. This can vary significantly with altitude and weather conditions affecting visibility in the seeker detection spectrum. Note that with older seekers this is relatively independent of target speed, but very dependent on target throttle setting (particularly afterburner). Furthermore, a sudden maneuver could change the target aspect such that what was previously tail-on and within seeker range is now abeam or even head-on and outside of seeker range. Of course, recent seeker advances have greatly improved seeker performance, particularly against the target's forward hemisphere aspect." Your most recent reply included this comment: "BUT I would happier IF you had set the most important conidtion and that is the target must be at zero aspect relative (180 if you use USAF terminology) to seeker, This is called a target centric envelope and it does look like a tomato! But if you start to increase aspect, the engine engine is unmasked and yyou no longer are looking at a tomato." ---- I'm not seeing what it is you think I'm wrong or unclear about. I said that regarding the seeker's view of the target, when the target is facing the seeker it might be only a few miles, but that as the seeker is looking more and more at the side and then the tail of the target, then the detection range increases until by the time the seekers view of the target is up his tail it may be more like 20 miles. Overall, this aspect angle of the target causes a heart-shaped zone around the target, within which the missile seeker can lock onto it. Therefore, what may be only 3 miles at 0 degrees (nose-on) may become 5 miles at 20 degrees off his nose, and 6 miles at 40 degrees off his nose, and 7 miles at 60 degrees off his nose, and 9 miles at 90 degrees (beam), and 12 miles at 135 degrees off his nose, and 20 miles looking straight up his tailpipe, i.e., heart-shaped. Then when you also consider the eliptical shape of the kinematic engagement envelope from the target's point-of-view, and overlap the two as only the shortest of the two is what counts, you end up with a tomato around the target, within which if you are flying toward him you can lock-on AND hit the target. Of course, that's assuming he continues straight and level; obviously counter-measures can still reduce the effective range even further. Displacedjim
 
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HJ    RE:IR Missile Range   4/10/2005 10:41:23 PM
Aspect is what I'm refering to. The "tomato" effect is only present with aspect coming down the "snot locker" say with reciprocal heading. If you are heading at the target and it has aspect the tomato effect dissapates with increasing aspect (not with to be confused angle off nose). In fact, kinematic envelope lessens as aspect increases. Not trying to belabor the point, just make sure the caveat is in place. Missile envelopes (or LAR/WEZ) are almost like CAT scans of the brain. You highlighted an important phenomena that is sometimes overlooked and is one reason LOAL is attractive.
 
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displacedjim    RE:IR Missile Range   4/10/2005 11:21:20 PM
Thank you. Now I think I see what you're pointing me to. The converse of what I was talking about is what you're reminding me of. I did allude to some of that as well in my original post when I said "Initial launch aircraft aspect to the target could impose some penalty if it requires significant initial missile course-correction" while discussing the kinematic range envelope. By that I was trying to refer to angle off the shooter's nose to the target. But you're right in that overall I was basically assuming the shooter being nose-on to the target. Not having gone to Fighter Weapons School or flying it for a living, I just have some basic figures to go by from the AFTTP3-1 (I'm not sure what the Navy calls whatever is their equivalent, but to USAF pilots it's their Bible regarding the threat, tactics, etc.) and I wasn't trying to talk too deeply on a subject I'm certainly no expert on--just hopefully correct some misinformed attitudes about the "maximum" range of heaters. Thanks for helping. Displacedjim
 
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