From what I’ve seen about the missile fired, the range seems to be roughly 3 miles and a speed in the range of 800 mph. I don’t know if that’s maximum or average or what.
If my impression is in the ballpark, it pretty well eliminates the idea of a ground to air defense–the flight time would be well under a minute, perhaps under 20 seconds. Anti-missile defenses ideally meet the projectile, not try to chase it and chasing would likely be the case here. The defending missile would have to cover more distance than the terrorist one and less time. I just don’t think this line of reasoning makes ground defense plausible.
aahala, that is very true, I would never want to try to hit an enemy SA-7b with another missile, that would be futile. Best chances are to confuse it, or to get outside the engagement envelope.
So roughly how much would it cost to install an automatic IR flare ejector? And how dangerous are those flares if triggered accidentally, e.g. by a nearby aircraft?
These flares only burn for about 4-6 seconds, and are ejected outward and/or downward from the aircraft. With our required spacing between commercial aircraft, this is not an issue for any following aircraft. The cost is such that the military does not put them on all aircraft that may be in harm’s way, but I don’t know how much.
Damn. Double post. How’d the hamsters manage that?
Having argued against countermeasures for the aircraft, I thought I might make some constructive comments.
I think the easiest (cheapest and fastest to deploy) would be a type of permanent “flare” installation at the airport. I’m thinking of something like a carbon arc light or a gas flame under a grid. All you need is something that puts out an IR signature that is much easier to detect than the plane’s engines. You post these “flares” inside your perimeter fence around the runway. The ones closer to the runway on shorter posts, naturally, and the ones further away on higher posts. There are regulations for safety zones that define that type of thing (height and distance from runway centerline) and you just follow them for your post heights. The spacing depends on how far the fence is from the runway. The closer the fence is to the runway, the closer you have to space your decoy “flares” to make sure that the missile will see them as well as the aircraft. The exact spacing also depends to some extent on the field of view of the missile. If it can only see IR sources with in twenty degrees of its course, then you need decoys spaced closer than if the missile has a 180 degree field of view.
For choice, I would go with some kind of electric arc - you can power cycle them and save energy because you don’t have to run them 24/7. A gas (natural gas, butane, propane, etc.) flame heating a grid to incandescence would work, too. It would be more costly in up keep (fuel, grid burnout, etc.) than an electrical system.
Since the whole schebang stays on the ground, you don’t have quite the certification nightmare. It is relatively low tech, so you don’t have a lot of cost or time in the manufacturing. It can all be done with in the existing airport safety zone, so you don’t need extra security personnel. Most of the logistics chain is already in place - electricity from the power company or gas from the utilities, gas burners available everywhere and arc lights not much harder to buy or make, posts and tall support columns available commercially.
All simple, (relatively) cheap, and easy to do.
FOV is, generally speaking, less than 2 degrees for these types of missiles (1.9 deg for the SA-7b). It is not easy to get a lock. The source of IR needs to begin with the target (or darned close) to distract the seeker.
It seems that there is some ambivalence in the weapon used.
As my job involves testing televisions (and no–it’s not a dream job–try pressing a remote control a couple of thousand times a day. Automated testing is still a year away.), NBC reported that a SA-7 had been used for trying to whack the El Al jet, not the Stinger.
From what little I’ve read, the Stinger is the more deadly of the two. I believe one advantage lies in the fact that it uses two sensors: one IR, the other UV to help prevent it from being spoofed so easily. But that’s based on something I read over a year ago, so take a grain of NaCl with this info
I don’t think there’s any feasible defense against these shoulder fired missiles, once they are fired. There’s only a small window of vulnerability timewise for commerical airline takeoffs and the landing paths tend to be so long, low and slow, impact is likely to be just a few seconds. So in one case, the risk is relatively small and in the other, defensive measures not likely to be successful.
How many of these weapons do the terrirosts have? A handful or thousands? Nobody knows but if they had many and that was their intention, don’t you think there would be a firing once a week rather than a few times a year?
An even greater effort of the US and other countries should be to secure their stockpiles of these things and REDUCE them. I have no idea how many the US has, but say they have 2,000. The newer types appear to be pretty effective, say 30-70%. What possible situation would require the immediate capability of shoting down 600 low flying planes?
Securing and reducing the stockpiles does nothing about the missiles the terrorists now have, but it does draw a circle around it.
Only the newest mod of the Stinger (RPM) has that capability (IR/UV), as far as I know, and there are still somewhat older models out there that only use IR.
The SA-7b is basically the US Redeye missile, the precursor to the Stinger generation.
As far as the stockpile, there were no Stinger missiles fired in the Gulf War, but there were Stinger Teams all over the place, each team with a minimum of 6 missiles (Man Portable, not vehicle mounted). A Section (1991 USMC numbers here) has 5 Teams, a Platoon has 3 Sections, a Battery has 3 Platoons, and a Battalion has two Batterys. That is 540 missiles for the basic load for only one Battalion in the Marine Corps. Double that for the second Battalion. Then add a hell of a lot more for however many teams the Army may have. We easily surpass 2000 with only the BASIC LOAD. There are many more in the supply chain to re-arm those teams that fire. If all bad guys came to one spot, we would not need that many, but we need to protect a lot of people and a lot of area IN CASE they get attacked.
Why not use an infrared jamming system? While not 100% effective they decrease the acquisition range that a person can use to gain a lock. Given the already narrow window needed to acquire a target with a SA-7 or Stinger it could be useful. Besides, is there anyway for the shooter to determine if he has locked onto the plane or the IR jammer signal? Also, even if the actual plane does get locked onto is it still possible for the IR jammer to spoof the missile?
That would be our best defense to this threat, in my opinion. I do not know this NEMESIS System, but it appears from the photo to have a laser that could (from reading the cite) defeat the seeker head.
No. I am proposing to put them outside of the safety zones of the runways.
Its been over twelve years since I worked on this type of thing so the regulations may have changed and civilian regulations are probably different, too. But, as best as I can remember it goes like this:
No obstructions of any height within100 meters from the ends of the runway, after that obstructions rising at (forgotten how much) slope for each meter over the 100. No obstructions of any height to left or right of runway center line within 50 meters, after that obstructions allowed at (forgotten how much) slope for each meter over the 50.
I wasn’t aware that the field of view was so narrow. Given that, my suggestion falls flat on its face.:mad:
Let’s just launch a massive fireworks barrage from the ground behind the ass of each airplane as it takes off. At least it’d be cheap.
That Nemesis system looks very interesting. I wonder if they could work if placed on towers around airports or if one would have to have one on every plane.
Getting back to being serious …
I think it would be preferable to use ground based systems rather than airplane based ones. You’ve got less investment in hardware (per airport instead of per plane - huge difference.) You can also protect all airplanes instead if just the ones that the airlines have managed to retro-fit. You also don’t have the added complexity of getting FAA approval and certification - which military planes might not need but which you would sure as hell have to have for commercial stuff.
The FAA is another point, as well. You might manage to pass a law in the U.S. requiring that U.S. planes have IR jamming, but how will you get the governments (and industries and FAA equivalents) of other countries to go along?
Along with that is also the possibilty that the Nemesis system mentioned above is restricted hardware. I really don’t think you want every Tom, Dick, Harry, and Osama to be able to put his paws on one. If they are installed on the planes, you’ve got more of them to keep track of and more chances for one to get “lost” or for someone to fiddle with one and figure out how to get around it. If you use a ground based system, you can put them controlled access areas (guarded towers) or even have the National Guard or the Army be responsible for them.
While explaining the current topic to Mrs. Furd, I had a truly wonderful thought. Most modern commercial jet engines are high bypass models - meaning that for every cubic foor of air that goes through the combustion chamber a higher volume is pulled through the compressors and mixed with the exhaust. The main reason for doing this is that it makes them quieter (and probably more fuel efficient.) A nifty little side effect is that the exhaust tempertature is much lower. I couldn’t find any hard data on exhaust temperatures, but I did find some info on bypass ratios: F16/F15 747/767
If the exhaust temperature goes down linearly as the bypass ratio increases, and assuming that the two engines have the same combustion chamber temperature (although I expect the commercial engine actually burns cooler,) then the exhaust temperature of the engines on a 747 should be about 1/14th of that of the F-15. Maybe the assumptions are ungrounded and I’m overly optimistic, but it seems like the exhaust temperature should be way lots lower on the commercial planes than on the military planes.
What I’m trying to get at is that the missiles are designed to track military jets. Is there enough difference in exhaust temperatures between military and commercial engines that the IR sensors would have a hard time locking on?
I think (and hope) that it might make a difference, but it would be nice if someone could verify/disprove this.
Hmm. That was poorly phrased. What I was trying to say was that the difference between exhaust temperature and ambient temperature for the commercial engine should be about 1/14th of that of the military engine.
