Supersonic AShM VS. Subsonic AShM

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.

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.

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.

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)

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.

most time you can lock a supersonic SSM once it's above horizon. but it's very hard to lock a stealthy subsonic SSM. you can't continuously track it coz its signatures are very weak and always hide in the background disturbed signals. you can catch its sinatures, but brokenly. those are not enough to support a lock process. so when the time you successfully lock a subsonic SSM and launch the interceptive SAM, the incoming SSM is almost only 20~ 30km away from you. the reactive time left to you is actually always short than some supersonic SSMs'.

conclusion is subsonic SSMs will be more deadly than supersonic SSMs untill above problems to be solved. and this is also the reason why american navy hasn't used any supersonic SSM in battle yet.

here's thai navy tests chinese c-801 and french mm-38. subsonic AShMs terminal trajectory could be as low as 3m.

I'd agree with most points here but not all. One can lower radar signature not depending on speed and almost not depending on size. Actually size too can be an advantage, if it gives you enough room to use radar absorbant materials of right thickness to help against radar wavelengths used for targeting on the ship you're attacking. IR signature would be a problem, true, though distance would be somewhat hard to judge from just that.

Size of sensors onboard also doesn't need to be small. Sure, it can be, but one has to set their priorites right. It could prove better to have a decent radar on than extra range from extra fuel.

Most of supersonics to date have actually been air launched. Almost exclusively russian designs. Though in some ways inferior, having a long reach missile was only chance russians would have to attack USN at open seas. And with 500 km ranges one simply could not use subsonics as target could get out of seeker's range in time needed for the missile to run its course. Hence high speeds.

Today's chinese missiles do seem to be subsonics (save for odd rumor here or there for terminal attack speed increase) while at the same time ranges keep drastically increasing. Probable reasoning for that is that main enemy would be taiwan, against who persistant airborne surveillance and tracking platforms could be employed, datalinking to missile while its on its way. Against an enemy like US, survival of such platforms (and precision of the missiles) would be in greater jeopardy. Alternative reasoning might be that radar seeker technology has gotten good enough so even from some 100 km or so missile can spot the ship and redirect itself to its new location. yj-62 seems large enough to house such radars.

Still, against enemy with mighty air cover, long range supersonics are way to go i believe. Appropriate sensors like ISAR must be equppied for better target discrimination at such long ranges (i'm basically talking radar horizon here, 400 km or so) and then you fire off a bunch and pray a few get through.

big toothbrush said:

here's thai navy tests chinese c-801 and french mm-38. subsonic AShMs terminal trajectory could be as low as 3m.

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Hi all,

I would like to know what happed to the Yinji-7 C-701 short range anti ship missile. Was it addopted in to PRC Navy?
Dont you think having a subsonic short range AShm would be useful in combating , small terrorist like sea units?

Thanks

Yaka

big toothbrush said:

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.

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Although the above statement is accurate, it is not an implication that the fuel efficiency of supersonic missiles is lesser than that of subsonic missiles.
It must be remembered that supersonic missiles such as the Brahmos and the Moskit have speeds upto Mach 2.8.

The air-breathing engines of these supersonic missiles ensure speeds of upto Mach 3, and thus coverage of large distances.

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.

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The above statement is accurate. Supersonic missiles perform manouevers such as the S-manouever, etc. in order to evade anti-ballistic missiles.

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.

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Although the length of the Brahmos is more than that of a subsonic cruise missile such as the Tomahawk, its diameter is only 60 cms as compared to the wingspan of 3 metres of subsonic cruise missiles (such as Tomahawk).
Thus, the RCS of subsonic cruise missiles may be more than that of supersonic missiles.

The reaction time of SAMs to engage incoming cruise missiles is constant.
Thus, subsonic cruise missiles offer more time for SAMs to react (since their speed is low), whereas the reaction time in the case of supersonic missiles is very less (since their speed is over thrice that of subsonic missiles).

Also, since supersonic missiles travel at upto Mach 6, tracking them and obtaining a lock-on to them is more tedious than subsonic missiles.

Hence, supersonic cruise missiles possess more protection features against SAMs, as compared to subsonic missiles.

3) supersonic SSMs can't fly as low as subsonic SSMs even in terminal phase.

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The above statement is inaccurate. The Brahmos missile is programmed to reduce its altitude to 5m to 15m above sea-level in the terminal phase, which is at 50 kms away from the target.

trajectory shiver would happen,

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The path of supersonic cruise missiles is fully sustained. Pin-point accuracy is achieved upon impact of the target.

plus the high speed, supersonic SSM is very easy to crush with water if it flys as low as a subsonic SSM.

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The Brahmos cruise missile can cruise at 5m above sea-level. The "water crush" as mentioned by you, does not occur.

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.

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The reduction in altitude of 5-15 m, by the Brahmos can be reached at 50 kms from the target. In the lo-lo cruise profile, the altitude is kept constant at 5m from launch to impact, although the range is restricted to 120kms only.

Even at lower altitudes, the speed of the Brahmos exceeds Mach 1 as compared to subsonic in the case for the Tomahawk.
Thus, the Brahmos shall offer lesser reaction time for SAMs as compared to subsonic cruise missiles.

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.

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The above statement is accurate. However, in flight-tests, the Brahmos has achieved pin-point accuracy upon impact of the designated targets.

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.

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The above statement is accurate.

conclusion is subsonic SSMs will be more deadly than supersonic SSMs untill above problems to be solved. and this is also the reason why american navy hasn't used any supersonic SSM in battle yet.

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In my view, supersonic cruise missiles are more "deadly" than subsonic cruise missiles.

The guidance mechanisms remaining the same, I would prefer a 500 km Brahmos missile to equip the Indian Navy as compared to a 500 km ranged Babur cruise.
The range of the Brahmos is restricted to 290kms because of the MTCR treaty only, to which Russia is a signatory.

The US has undertaken research on hypersonic cruise missiles. These shall have speeds of upto Mach 8 and shall be nearly invincible to almost any SAM system in service currently.

advantages for supersonic:
1. less reaction time for the defensive system
2. if travelling at the same altitude, it's probably harder to obtain a lock on a supersonic missile, since it is travelling so freaking fast.
3. and then, most likely harder to shoot down a faster moving target for the defensive system

disadvantage:
1. increased weight + higher flying altitude - in the case of moskit, it's just a mammoth AShM. Brahmos is smaller, but it travels in high altitude (14 km) for most of the flight. And even Brahmos is much heavier than the subsonic ones.
2. can be detected further out - due to the fact that they are travelling at higher altitude and has higher IR signature and probably has larger radar signature due to the larger size.
3. it has less time to acquire target, meaning it has less time to counter the ECM, the decoy missiles, basically less time to distinguish the real target from the duped ones.

disadvantage 2 is basically countered by advantage 1
disadvantage 3 is countered by advantage 2

so basically, against systems that has low range detection vs missiles at high altitude and the ability to shoot these missiles down at long distance (say SM-3 or SM-2), these missiles might not be as effective as a real low flying subsonic missile.

and against systems that have relatively low detection range vs missiles, the supersonic missile will have the advantage of giving the system less time to react.

so, I guess the best combination is something like Club missile which travels at low altitude and only goes supersonic in terminal phase.

I agree with most of the comparisons laid out between super-sonic and sub-sonic SSM's. Here's something other than the actual performance:

1. Supersonic SSM's are not cheap. Everything from research, testing, manufacturing, maintenance are all more expensive than subsonic SSM's. You can look at cost two ways: a) you can equip more subsonic missiles with the same $$. b) you can spend more $$ on the on-board electronics and launch hardware (radar and computer systems).

2. Supersonic SSM's are bulkier compared to subsonic SSM's, and they require a bigger launch platform. For example, I doubt that Bhramos can be launched easily from a 3500t FFG. On the other hand, C803 can be launched from a small and fast F22.

Finally, the above two points give subsonic SSM a strategic advantage: you can make them in mass numbers and can launch attacks with 100's of those at the same time.

The August Kanwa said that China has basically mastered the sub-sonic antiship missile and its already sitting at the world's cutting edge in this technology. Kanwa further surmises that China will modify its sub-sonic missiles to create a next generation of terminal supersonic antiship missiles.

Totoro said:

Though in some ways inferior, having a long reach missile was only chance russians would have to attack USN at open seas. And with 500 km ranges one simply could not use subsonics as target could get out of seeker's range in time needed for the missile to run its course. Hence high speeds.

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This is kind of a misconception of sorts. For example, the USN TASM had a nominal range of 470Km (250Nm). It travelled at around 520 knots, which is a little above 600 Mph. Since V=D/T you can easily see that the missile would travel it's entire range in about 25 minutes. A ship travelling at it's probable speed range of 10-12 knots would only have moved a total of 5-6 Nm (approx). Easily within range of TASM's seeker at point of enable. And as someone who actually worked onboard one of these types of ships, I'll tell you that no ship runs around the ocean at flank speed. Fuel considerations (range) (endurance) don't allow for it. But even then, at 30 knots, he moved 15 Nm. With a spread of less than 1 degree you can easily solve that problem.

Yes, TASM was actually a highly effective long range anti-ship missile. The USN was unhappy with it's performance, true, but not because of it's speed, range, or any other performance parameter. The USN just didn't like the performance of any long-range anti-ship missile in general, including Russia's supersonic models. I won't go into all the thinking behind it, but one of the main considerations is even when you detect something at 300 Km ranges and beyond, you still have to identify it, and track it, and target it. And you have to assess other things like other traffic in the area. You have to take into consideration of overall movement of the contact. And there are many more considerations. Just because your radar sees something at 300 Km, you still don't know whether it's a naval ship or not. Or whether it's friend or foe. etc. etc. etc. You don't just point a radar and shoot.

The USN only wanted TASM's in service to destroy surface ships in known bastioned/controlled areas. Today, there is no Navy that possesses the kind of strength to control vast sea areas like the Soviets once did for the USN to consider a threat. Only USN itself has that kind of power. And so, TASM is gone.

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You guys have some great thoughts in this thread. I would say a big advantage to supersonic over subsonic that has been missed is it's overall kinetic energy/killing power. It would obviously be much more damaging for a single 'Shipwreck' to hit a ships hull, than a single Harpoon, Exocet, C-802. But you guys pretty much summed up why I would prefer a sophisticated subsonic missile over a supersonic one any day.

And remember, it's not just the missile. You need the sensors and networks to be able to detect, track, ID, and gain a fire control solution. And you have to know how to use them, and how to maneuver to gain the positional advantages. ASuW is not so simplistic as point a radar and say Ah-hah! Then launch a missile. It just don't work that way.

I essentially agree with the pro-subsonic camp here, but I would like to say that each missle has their own use in real combat situations. Like TPHuang said, the Soviets developed the long ranged supersonic missle in order to put USN ships in range of their own ships and aircraft, something they could not have accomplished with subsonic missles due to the USN's sir superiority. Thus, a supersonic missle is something of a guerilla style equalizer in naval warfare. Much like a guerilla warrior trades overall hitting power in exchange for survivability and an assurance that they will indeed hit, a supersonic missle trades overall effectiveness for an assurance that an inferior navy can still provide a credible threat to an enemy that can engage it at arms length.