Tech.Info.4/Akash/Rajendra

[Peeyoosh]

Salman<P>Thanks as always.<P>Two quick comments.<P>Akash as a SAM vs. Akash interdicting SRBMs/IRBMs.<P>SAM role - Need to work on the smoky propellant of the SA-6 as a plume is far easier to spot and react to, rather than a SAM itself. the later the pilot spots it, the lesser the reaction time.<P>Integrating a wide aspect IR seeker into the guidance system is key - in case the guidance radar has to shut down due to HARM strike or if the target punches on afterburners and uses chaff to evade. <BR>Wonder how easy it would be to use inputs from two sources to guide the tracking logic, which input system would get precence under which set of condidtions? Desiging the operating logic is not going to be very easy.<P>In an anti missile role, I guess the radar systems are good enough and smoky propellant is fine, but is the Akash responsive enough to take on the role?<P>One last aside - how much of the radar cost is in the enrgy generator and transmitter and how much is in the signal receiver and processor. If the receiever/processor is the bulk of the cost then putting out decoys to confuse a HARM strike should be an option.<P>Peeyoosh

[Sukumar]

Good job Salman. Very informative post.<P>For quite some time, I had been thinking that the Akash is quite visually similar to the SA-6. Additionally, the common propulsion architecture had lead me to believe that DRDO based the Akash on the SA-6. Your posting confirms that.<P>I agree with Peeyosh. Apart from command guidance, Akash needs a semi active IR homing mode. This could also be used in the terminal guidance phase. The logic can be easily programmed with the following rules:<P>1. Command guidance supercedes IR info.<BR>2. If command guidance ceases, IR takes over.<P>This will preclude the IR sensors being misled by flares or the sun. However, it provides a backup if the Rajendra eats a HARM.<P>I know that phased arrays are harder to lock on to with a HARM compared to a regular radar. Anybody with more info on how frequency agile the Rajendra is both in the radar emitting mode as well as command guidance mode ?<P>To enhance the Rajendra's effective detecting range, all it means is that the radar has to put out more power. I wonder how that would be accomplished from within the confines of the BMP-2 launch vehicle. Perhaps a second "generator" vehicle would be hooked up to the BMP-2 carrier.

[Sukumar]

In a semi-active IR homing mode, the IR sensor is not on all the time. It is switched on selectively at a pre-determined phase - for example the terminal guidance phase or "end-game". <P>In most SAMs there are two sensors - active radar emitter/sensor and passive IR or passive radar sensor and passive IR or one of the two. <P>In the Akash's case it is purely command guidance, which means that the missile is a slave that is commanded by the Rajendra radar. Most phased-array radar/SAM systems work this way including the USN Aegis/Standard combination.

[Sukumar]

"So "semi-active" still means "passive" just std IR homing used in terminal phase? " <P>Yes. <P>What I am suggesting is command guidance + semi-active IR homing. I believe IR is always a passive sensor unlike radar which has an "active" emitter and a "passive" sensor. If a dual seeker is under development, that is great news.<P>I already addressed Peeyosh's question on logic in my first post above. Does anybody know the wattage put out by Rajendra ?<P>Also the Standard uses a Inertial/semi-active radar homing seeker. Here is some info on the Standard/Aegis combination:<P><B>General Characteristics, SM-1, SM-2 Extended Range </B><P>Primary Function: Surface to air missile<BR>Contractor: Hughes Missile Systems Company (formerly General Dynamics' Ponoma Division, sold to Hughes in<BR>1992) Ponoma Division; Raytheon Motorola; Morton-Thiokol; Atlantic Research and others<BR>Unit cost: $409,000<BR>Power plant: Two-stage, solid-fuel rocket; sustainer motor and booster motor<BR>Length: 26.2 feet (7.9 meters)<BR>Weight: 2,980 pounds (1341 kg)<BR>Diameter: 13.5 inches (34.3 cm)<BR>Wing Span: 5 feet 2 inches (1.6 meters)<BR>Range: 65-100 nautical miles (75-115 statute miles)<BR>Guidance system: Inertial/semi-active radar homing<BR>Warhead: Proximity fuse, high explosive<BR>Date Deployed: 1981<P><B>Aegis System</B><BR>Description: The Aegis system was designed as a total weapon system, from detection to kill. The heart of the system is an advanced, automatic detect and track, multi-function phased-array radar, the AN/SPY-1. This high powered (four megawatt) radar is able to perform search, track and missile guidance functions simultaneously with a track capacity of over 100 targets. The first Engineering Development Model (EDM-1) was installed in the test ship, USS Norton Sound (AVM 1) in 1973.<P>The computer-based command and decision element is the core of the Aegis combat system. This interface makes the Aegis combat system capable of simultaneous operation against a multi-mission threat: anti-air, anti-surface and anti-submarine warfare.<P>

[Peeyoosh]

Folks<P>This is rather good.<P>Vikrant<P>Thanks for the info - 25% of the system cost for a decoy is still high. I wonder if a hack could help lower it still. Is the signal generator's (the Klystron) signal signifaicantly degraded if it has to travel large distances via a Copper/Al sheathed cable? Could I hook up one Klysrtron to two or three antennae by say - 60/70 meters of cable and expect to simulate two or three radars? Would amps help? Sorry for the very funny questions but you seem pretty clued onto this.<P>Sukumar<P>Using a handover to IR in case of base radar guidance failure is kind of a naive logic? Don't you think that one could design a better logic that uses the IR signal to vet the radar input. <P>Add to that the fact that the IR sensor is an on-board sensor and hence ought to be quicker to guide the missile in its final manouvering. I also believe that IR systems are extremely sophisticated now and can vet flares, the sun etc.<P>On the Aegis - man that is a bit off for us for now <P>Just wondering!<P>Salman<P>Once upon a time not so long ago, I learnt that the reason for a smoky flame was incomplete combustion though that was for hydrocarbon based fuels - wonder if it stands true for metal fuels too? I wonder if using Mg rather than Al increases the flame temp. or the combustion effieciency?<P>Peeyoosh

[Sukumar]

Ah! Salman, now I see that the Akash uses a semi-active radar seeker with mid-course command guidance. That makes more sense. Now just to add the "passive" IR seeker also.<P>Peeyosh, IR sensing still has ways to go technology wise, though things have improved tremendously. Having both radar and IR sensors means you are probably twice as sure about what the target is doing. The problem happens when they provide totally different inputs i.e. one is getting decoyed.<P>I believe that radar signal processing is much more advanced than IR, which is why I proposed that the IR is superceded by the radar input. Semi-active radar means that the radar signal processor is on the missile. This concept of signal logic is quite complicated and the subject of much research. I am sure that established rules already exist that can be improved upon.<P>Does anybody know the power put out by Rajendra (Watts ??)

[Kuttan]

Very informative thread. Are you folks not worried that "Khan-baba" and his ilk may use these complicated mathematical expressions and figure out why the Ghauri keeps moving downwards rather than upwards when they light the top end?<P>For example, giving the value 3.14...<P>That could advance Pakistani research by a decade!<P>In Alabama, the State Legislature is debating correcting the value of pii to 3, as it was intended to be, before the communists confused everyone. <p>[This message has been edited by narayanan (edited 26-07-99).]

[vverma]

<a href="http://valhalla.angband.org/~gt8167c/my ... jpg">Akash being loaded on to a BMP-2 for testing</a>

[Sukumar]

damn ! my computer cant download the pic again from this angband.org site. Vverma, would it be possible to load the pix on a faster site ?<P>Try angelfire, yahoo, netscape or something ? Is it the same pic as on the BR missiles site ?<p>[This message has been edited by R Sukumar (edited 26-07-99).]

[vverma]

Sorry Sukumar. That angband.org is a UNIX box in my friend's dorm room. I think your ISP can't find the correct router. Anyway, here's a pic of the SA-6 loaded on its TEL with the Straight Flush engagement radar(??) in the background. <BR><a href="http://vverma.home.mindspring.com/SA-6.jpg">Click here.</a>

[vverma]

BTW, I posted the pics for both so people can compare. Salman seems to be mostly correct about the similarities bet'n the SA-6 and Akash.

[Peeyoosh]

Vikrant<P>You are right, dumb idea.<P>Peeyoosh

[Sukumar]

Jeez ! Verma, you were giving my ISP a merry chase around the web Thanks Rohit.<P>It is interesting that DRDO has not published too many pics of Akash, Trishul (anybody seen Trishul ?), Rajendra, Pinaka etc. When are they gonna learn some marketing

[vverma]

I think that's what DRDO is trying to do with drdo.org.

[Sukumar]

Salman, after quite some time I was perusing the BR pages on Akash. If what is said there is true, then the Akash has an active radar seeker which is used in the terminal phase, not semi-active as you have mentioned.<P>What this means is that the Akash carries an emitter which illuminates the target in the terminal phase. This would make it a very deadly weapon, because I am sure that the guidance logic would switch on the active seeker if the Rajendra eats a HARM.<P>The dual mode seeker adds passive IR homing. I really hope that the 60 KM version is soon out.

[Peeyoosh]

Could one build an emitter strong enough to paint the target from a reasonable distance (say 20-25 km.) and yet fit in the nose of a Akash?<P>any opinions Vikrant?

[Peeyoosh]

Salman<P>If used only for the terminal stage agree - then a 3-5 km range sounds fine to me. I was wondering more along lines of an intermediate range handover in case of a HARM attack.<P>By-the-way what is the advantage of using active terminal guidance?<P>Thx.<P>Peeyoosh

[Peeyoosh]

Salman<P>Ought to have made my query clear. What is the ebnefit of having "end game/terminal stage" active guidance with 5 km. range for SAMs.<P>If the intent is a handover in case of a HARM threat to SAM base - then I feel the active guidance would need a longer range - say close to around the range of a HARM missile!<P>Peeyoosh

[Sukumar]

Peeyosh, the objective is to provide mid course guidance and get the missile to the vicinity of the target in a standard mode of operation, not in case the guidance radar eats a HARM.<P>If some one was trying to help you find your way, they may walk with you to the street corner and then let you find the right house. <BR>Similarly, to avoid the need to put a powerful and big radar in the nose of the missile, the guidance radar takes it up to a certain point. This is true of most missiles including the mighty AIM-54C Phoenix carried by the F-14 Tomcat.<P>The missile then uses its radar to "lock on" to the target and terminate the end game. The wailing of the RWR is the last thing that the enemy pilot hears.