ahussains said:
at current state of the art subsonic SSM is indeed more efficient than supersonic one.
1) supersonic SSMs have to fly a high trajectory to maintain long distance trip, coz at low altitude air is much more dense than at high altitude. supersonic SSM will run out its fuel very soon when flying low trajectory due to resistance from air.
any high altitude object is easy target for SAM. the higher you are means you are above the horizon to farer enemy, enemy could detect you earlier, and have more reactive time.
while subsonic SSM could have a whole trip low-altitude flying. without support from airborne sensors, you can't detect it untill the missile got close to a distance that 30~50km far from you. this is the average horizon view range for shipborne radars.
I would tend to agree on this point. However, I'd like to point out that you are assuming that the launch platform fires the missile from it's maximum range. If the target does not have AEW support then, the launcher can get to just over the horizon and then launch his missiles. Since the missile has a shorter distance to fly it would be able to afford the additional fuel penalty. In such a situation, a supersonic AShM would have the advantage of reduced response time on the part of the target. If the target does have an AEW capability, then it does not matter whether the AShM is supersonic or not, it would be detected well before it pops over the horizon.
ahussains said:
2) supersonic SSMs have more obvious IR signature and bigger RCS than subsonic SSMs', which means the latter one would have less chance to be detected.
No doubt that supersonic SSMs would have a bigger IR signature. This is not much of a disadvantage. Very few ships have an IR early warning system installed (the Canadian and Dutch navies are among the first to do so). And if you're referring to IR-guided missiles like the RAM or the Sea Chaparral, you need to keep one thing in mind... unlike (most) radar-guided missiles which 'lead' the target (i.e. they aim for a point slightly ahead of the target, so that they intercept it), IR-guided missiles 'chase' the target. By this I mean that they aim for the hottest part of the target and try to overtake and hit it. This is quite practicable in the case of a (comparatively) slow moving aircraft or cruise missile. But the faster the target, the more difficult it is for the missile to intercept it. If you look at the kill envelope for any IR missile, you will see that it is most effective when fired from behind or to the sides of the target, and not from the front as in the case of a ship defending itself.
ahussains said:
3) supersonic SSMs can't fly as low as subsonic SSMs even in terminal phase. supersonic SSMs' high speed causes stochastic high pressure from air. trajectory shiver would happen, plus the high speed, supersonic SSM is very easy to crush with water if it flys as low as a subsonic SSM.
normally a supersonic SSM flys 30m high in terminal phase and only reduce to 5m in the last 1km of the trip. while a subsonic SSM flys 3~5m high in terminal phase. this also mean the latter one would have less chance to be detectd and shot down. this also mean the latter one would have less chance to be detectd and shot down.
I have not seen anything to substantiate this claim of a high-terminal altitude. Do you have any sources for this?
ahussains said:
4) supersonic SSM's seeker has to stand a more atrocious working environment than subsonic SSM's seeker does. thus even if their seekers have the same size apertures, the latter one's would have more chance to lock on target.(actually in most cases supersonic SSM's seeker has smaller aperture coz it has to save space to carry much more fuel)
Yes the aerodynamic forces on a supersonic missile are much greater than those on a missile flying slower. Radio waves are not affected by the physical environment, so given identical radars, speed will not make any difference to the performance of the radar. However, it is true that when a body flies extremely fast, the heated air (plasma actually) causes radio interference. Thankfully, hypersonic missiles are years away, so we'll cross that bridge when we come to it.
As for supersonics having a small radar 'aperture' (I'm assuming that you mean the size of the radar antenna), the diameter of the missile is determined by the missile's role and launch platform, not by it's speed. Just to give you some examples
Missile____________________Diameter
_________________________________
BrahMos___________________0.60 m
Tomahawk (TASM)__________0.52 m
Harpoon___________________0.34 m
C-802_____________________0.36 m
Moskit (SS-N-22)____________0.53 m
Exocet ____________________0.35 m
Penguin___________________ 0.28 m
Kh-35_____________________0.36 m
SS-N-25__________________ 0.42 m
SS-N-19__________________ 0.85 m
With the exception of the BrahMod, the SS-N-19 and the Moskit, all the missiles are subsonic.
ahussains said:
5) supersonic SSM's reflected radar waves have more obvious doppler frequency shift than subsonic's coz supersonic SSM has higher relative speed to enemy's radar. it means it's more easy to pick supersonic SSM's signals from background disturbed signals such as radar waves reflected by water.
You are correct on the point that ships (and aircraft) use the Doppler effect to filter out spurious signals like waves (and birds, and cars, speedboats etc). However, anything that moves faster than a preset limit (that limit is set depending on the local condition) is picked up as a possible target. To the radar, it makes no difference if the incoming contact is travelling at 850 km/h or 2000 km/h, both are potential threats and both would be displayed.
