Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!ted From: ted@cs.utexas.edu (Ted Woodward) Newsgroups: comp.sys.mac.games Subject: Re: Sinking Carriers in Harpoon Message-ID: <321@victoria.cs.utexas.edu> Date: 6 May 91 17:35:15 GMT References: Organization: U Texas Dept of Computer Sciences, Austin TX Lines: 54 In article sr26+@andrew.cmu.edu (Stephen Alexander Racunas) writes: >The problem with Phoenix missiles is not the altitude change causing the >missile to lose lock. The Phoenix is a "look down shoot down" missile that can >handle targets changing altitude and targets lost in ground clutter. The >problem is when the plane drops to VLOW altitude, it goes below the radar >horizon of the missile... i.e. there is WATER on the direct line path from the >missile to the target and the missile CANNOT SEE THE PLANE to shoot it down. I think you mean to say that the phoenix uses active radar homing; it doesn't need to be guided by a plane while in flight. There are three problems with your analysis: 1) AIM-54C's (the digital phoenix used in Harpoon) use inertial guidance (basically, 'go here') with mid course correction (the target moved; go here instead) with terminal active radar homing (OK, you are close enough, turn on the radar on go in). By the time the phoenix is close enough to use it's radar homing, it won't worry about LOS to the target. So even if the target initially dives below the radar horizon, you can still send the missile after it. 2) It doesn't matter when the target dives to very low; even if it is 1 nm away the phoenix will still miss. 3) If you are at high and have a standard 2er shot at you (range 75 nm), it will hit you if you stay at very low. Now, it too has inertial guidance and mid course correction, but if you are farther than 26nm from the launching platform (large ship to very low target radar horizon), it can't hit you. But it does. My conclusion is that harpoon does not check to see if you are below the radar horizon at the time of impact; instead it only checks at the time of launching. You may see the same thing with SA-N-6s launched by Russian cruisers, but it's different. Those missiles use Track Via Missile guidance, which means that each missile must be guided separately, as opposed to standard missiles only needing to be guided while terminal. Also, Soviet naval helicopters (Ka-25B's, I think) have equipment built in to relay the TVM signal. So if he has choppers up, he can guide missiles against very low targets out to their max range. Oh, the Leahy class cruisers do not conform to what I just said in the game. They are equipped with SM2ER, so should be able to have any number in the air at once, subject to launching restrictions. But they only seem to want 4 missiles in the air at once; in fact, the only ships I have seen with more missiles in the air than directors are Aegis ships, even though all SM2 armed ships keep missiles inertial except during the terminal phase, an, while SM1s are semi active radar homing throughout their entire flight, you can still point the director at one member of a group, shoot at it, shoot another missile later slaved to the same director, and switch targets after the 1st missile destroys the 1st target. -- Ted Woodward (ted@cs.utexas.edu) "Mad scientists HATE shopping for shoes!" -- Peaches