sampson@attctc.Dallas.TX.US (Steve Sampson) (01/14/90)
From: sampson@attctc.Dallas.TX.US (Steve Sampson) > From: denbeste@spdcc.com (Steven Den Beste) > From an operational point of view, a jet's IFF-receiver is precisely > such a transponder. Whenever it receives a challenge, it answers. Only a proper challenge. Improper challenges either beep or light a lamp based on a switch position. The missle will have to ensure it gets a reply from the target before launch. It must decode replies from other targets in the area and distinguish the real one. > SAM can figure out how to send a challenge, it can then home in on the > jet's answer. It doesn't know what the answer means, and it doesn't > care. At the lowest level, it is just a radio beacon towards which > the missile can aim. > The jet will, of course, also challenge the missile The transponder does not interrogate. It merely replies. Modern fighters do have interrogaters on-board. They are useful for sorting out the bad guys, but are of no use in avoiding terminal high-Mach Air-to-Air, or Surface-to-Air missles. Any SAM or AAM in the air is to be avoided, as they usually don't care what they hit. I can't see designing and flying with/deploying a missle that will only track IFF beacon replies. The ECCM is too easy (eg, shut IFF off). > Anything which prevents the jet from answering also risks having the > jet fail to answer a missile which IS friendly. It's my understanding most nations employ two types of missles: radar guided and heat guided. I've never heard of a good-guy abort algorithm. You shoot, missle tracks, aircraft dies, you see friendly pilot eject, oops... > Just how do you make sure that all the friendly time-of-day clocks > are synchronized within a fraction of a second? I don't see how this > could be done in practice. You would have to have everyone Sync to the same master clock. This can be done on request by ground and airborne units Syncing to an orbiting C3 platform (which gets his from Region HQ). Each unit has a rubidium clock (sp?) that maintains accurate time for many hours after Sync. Option 1 will work. > So my point is this: As long as one of our jets has IFF onboard and > operating, there should be a relatively unsubtle way that a SAM can home in > on that IFF system so as to destroy said jet. The jet's IFF will correctly > identify the SAM as a foe, but this is irrelevant. (Except that it means the > pilot can try somehow to evade the thing.) Let's say you got a contract to develop such a missle (jets don't interrogate missles, they're so high speed the reply comes back after impact) and the pilot has not "strangled" his IFF. The missle tracking algorithm waits for an IFF interrogation. It then engages and is released. This unit then continuously interrogates and tracks any replying target. Probably wouldn't need a very high rate of interrogation. Sounds like it may work. Further research shows you need a SIF rejection algorithm, some sort of amplitude tracker, and then proximity fuse. You wouldn't want it to start tracking another target. One problem is a pilot would get very suspicious when his IFF all of a sudden had a high interrogation rate followed by visual contact with an inbound AAM or SAM. Normally the IFF is not used much, so any use of that feature will raise suspicion. If the pilot gets back to a debrief the tactics would change very quickly, so you need 100% kill rate. I'd say it all sounds pretty neat for a one time good deal, but wouldn't be as effective as less technical means. Plus - there's no guarantee that the missle will go after the highest priority threat. It may lock on to some empty C-130 just as well as a fully loaded B-1 bearing down on its target. Conversation in the arming pit: Mig Armer: "What will it be sir?" Mig Pilot: "ah, let's see, how about 4 heats and 4 radar, load the guns" Mig Armer: "Hey! I got a good deal on IFF trackers, they're really Neat-O" Mig Pilot: "rubbish"