Currently I am having a discussion with a certain person about the horizon search capability of APAR (the one on the Sachsen class) against sea skimmers. Could other people confirm the following physical principles?
1. Horizon for 5m target illuminated by a radar at 20m elevation is 27km. Calculated form here – http://www.qsl.net/w4sat/horizon.htm
2. There is no way to detect under the horizon air targets in the X band. I know about radars using tropospheric effects to get an over the horizon reading for surface ships like this one – http://www.selex-si.com/EN/Common/files/SelexSI/brochure_datasheet/2008/Data_Sheet/RAN30X.pdf however that mode is completely useless against sea skimmers.
3. The APAR brochure gives the range at 75km against “low flying targets” but I suppose they have specified it against something flying at 100-200m, not against a skimming missile? http://www.thalesgroup.com/Countries/Netherlands/Documents/Datasheet_APAR/?LangType=2057
Are my assumptions correct?
By: Vetinari - 29th April 2012 at 18:23
So basically something in the class of 737AEW will have difficulties getting data on targets of the Harpoon/Kh-35 class and will detect them at about let’s say 100km?
Also, if the data is so unreliable, I presume that it is useless for guiding ship-based IR homing missiles over the horizon against the sea skimmers (relying purely on the data from the 737, I’m not sure if the airplane could even communicate with the missiles directly)?
By: obligatory - 29th April 2012 at 14:57
AEW is not overly effective in detecting skimmers, and it depend greatly on weather condition, Pk is probably a bit less on an average.
By: Vetinari - 29th April 2012 at 11:40
Anyone? At least any examples for over the horizon guidance of SM-2 Block IIIB will be greatly appreciated.
By: Vetinari - 28th April 2012 at 00:06
Thanks a lot for the help, as I understand my assumptions have been correct.
All in all, currently I am involved in the design of a board based (internet board) game that involves a modern asymmetrical conflict involving an amphibious landing against certain opposition (the landing side is based on a perceived Turkish Navy fleet in 2024). Because of that the escorts of the landing crafts have to intercept an expected salvo of subsonic sea-skimmers (between 32-128), I am having a heated discussion with my friends about certain parameters and a few new questions appeared:
1. Assumed launch interval between ESSM/SM-2/RAM missiles is taken as 1-2s
2. Another assumption is that 737AEW cannot possibly provide direct mid course guidance for SM-2 Block IIIB for over the horizon engagements (as that block has a thermal imaging seeker) or sufficiently accurate data to the ship command system in order to attempt such engagements (given that a sea skimmer has its small engine underneath the airframe the thermal signature should be low and the accuracy of directing the missiles to use their seeker should be insufficient). I do know that such attempts have been made with a Hawkeye and SM-3 with AMRAAM seeker, but that is not the case for the SM-2/737AEW combo. Am I correct? At least my assumption is that the 737AEW is mostly useful in directing battles between aircraft.
3. From the above thoughts the only useful info that an AEW could give to the ships will be of the vector of attack and rough arrival time. Also, I have my doubts that 737AEW could see small targets at sea level from its maximum range.
4. I am modelling the TF-2000 frigates on the Sachsen Class, however I think it is a bit of an overkill as the Germans appear as something utterly capable AND expensive. What should be the ammount of targets engaged by a frigate based SPY-1 coming from one direction? I know that it depends on AN/SPG-62 mounted, but given that two are provided for illumination, they should manage attacking 8 targets simultaneously?
5. From all of the above – any engagement against sea-skimmers (modelled on Kh-35) should start at about 20km, give or take a few kilometres depending on waves, weather, and luck. At that point on till the missiles hit, the flotilla attempts to shoot at least two SM-2/ESSM for each incoming missile. Any self-defense like Phalanx or RAM is used only if the missile is coming directly against the ship with the CIWS itself. Are these assumptions correct?
6. From point 5 – the close in “dead” zone of SM-2 is important and it is about 7-8km in my assumption, I hope that is correct? For the dead zone of ESSM I assume something like 2km.
7. For older ships of the formation like any Perry class frigates – won’t the number of air targets in the air (over 300 if things happen simulatenously) saturate the onboard radar, forcing it to ignore some tracks? (modelled as reduced efficiency and kill probablility)
8. Against skimmers I use probability to kill of 0.7 for SM-2 and 0.8 for ESSM, that should be reasonable?
By: radar - 27th April 2012 at 23:28
the brochure says:
I/J (X) band active phased array for low elevation detection out to 75 km
which does not mean that apar is able to detect a sea skimming target at 75 km. low elevation is not the same than low altitude.
the reason that x-band is preferable for low elevation horizon search is that the first lobe is very close to the surface compared to lower frequencies.
By: Jonesy - 27th April 2012 at 18:29
1. Give or take 1000m yes. That is the point where the inbound crosses the horizon detection and track forming would be some seconds later.
2. I/J band does direct line of sight only. E/F bands can curve over the horizon in a limited fashion but do not have the resolution for the kind of endgame illumination APAR can provide.
3. Definition of low altitude being all important!
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April 26, 2012 at 10:44 pm