Indian Missiles and Munitions Discussion - June'14

[Indranil]

Yagnashri, there is an "eighteen month" sword hanging. And it should. But 20 million ...

[ramana]

Indranil, 18 months is too short finding root cause in an aero development failure.

[SaiK]

Divide and conquer the problems .. once found, it should be fairly a game to get it cracking. Most of the time is lost in getting to the problem.
So, if we believe if it is only the wing, then 18 months to fix it should be enough with a bunch of "reactive minds" handling a crisis situation. No sleep for them I guess for a year or two.

[kurup]

This bunch of Agni missiles is getting way too complicated for a doltish mind like me. So I've been compiling some data and came across this presentation, has some diagrams, mathematical formulas and explanations which may prove useful : http://isssp.in/wp-content/uploads/2015 ... agappa.pdf

This is some of the data I've collected till now and reasonably sure that most of it is correct, more or less. There is a lot of conflicting information which makes this work quite time consuming. Wikipedia has numerous such errors and I have processed dozens if not hundreds of webpages to be reasonably sure. Apart from data related to "VEHICLE, OPERATIONAL, 1st Test, Last Test, Total tests, USER" if there is anything that needs to be added, kindly let me know.





Apogee Data
http://www.astronautix.com/i/india.html

https://books.google.co.in/books?id=Yt2 ... ni&f=false

According to DRDO , the payload of Agni 3 is only 1500kg .

[kurup]

Arun, Great finding Frontline interview. In hindsight Mr Chander gave a lot of info on what was the design philosophy.
Interstage with trusses were for upper stage exhaust gases at separation eject/vent easily. And lighting the forward stage just before separation gives positive way of stage separation as the exhaust pushes the departing stage. But this causes sever thermal and shock environment between the stages and aft equipment has to be rugged thermally and structurally.
So using retro rockets motors to pushway the departing stage is old school space vehicle technology but avoids the environment I was talking about. Good for less energetic motors.

One key word he used is motor pressure.
Energy of a rocket motor is proportional to burn area and pressure. From G.P. Sutton 'Fundamentals of Propulsion'

So Agni motors have been finally system designed and not put together as IGMP had to make do with in early phases with ASLV hand me downs and Prithvi jugaads.

So what is the weight of AIII and A V payloads?
I know it is 1.5 tonnes for A V.
What was it for AIII?

From DRDO NEWSLETTER March 2010 ,

[ramana]

Thanks. So AIII and AV have same 1.5 tonne payload. A I and A IV have 1 tonne.
What is the weight of aircraft delivered bomb?

[kurup]

Kurup, Can you check for NOTAM in April 2016 for K4?

On first week of march 2016 there were reports that India will test K4 on the next week .

http://asian-defence-news.blogspot.in/2 ... -week.html


Hemant Route reported that K4 was tested in a depressed trajectory on march 7 from a submerged pontoon .

http://www.newindianexpress.com/states/ ... 12114.html


Again it was reported that K4 was test fired from Arihant on march 31 .

http://thediplomat.com/2016/04/india-su ... c-missile/


The only NAVAREA I could get my hands on around that time period was for a 650+ km test ..... all credits to PARIKRAMA of IDF .

[Karan M]

excellent news RCI navigation was not at fault. which is good neqs for the plethora of other RCI programs.

[arun]

Then again on the Missile Complex Hyderabad vs ADE spat........................

“First rule in politics: never believe anything until it's officially denied.” – James Hacker (BBC TV Series “Yes, Prime Minister”)

[Karan M]

Use common sense. The same systems work for Agnis, Prithvis, Prahaars, SLBMs and wont work for a Nirbhay? Nirbhay was always around giving a novice team, experience. Creating a second missile capability at ADE vs Hyderabad. It will take time.

[darshhan]

Use common sense. The same systems work for Agnis, Prithvis, Prahaars, SLBMs and wont work for a Nirbhay? Nirbhay was always around giving a novice team, experience. Creating a second missile capability at ADE vs Hyderabad. It will take time.

Right on dot. Rci imarat has a well deserved very good reputation wrt delivery of effective missile systems. It would definitely rank in top 3 centres all over the globe, where research and development of missile systems is concerned.

[sudeepj]

First good the root cause is wing deployment mechanism.

I can easily see the recrimination. We didn't see the telemetry nor the video/animation driven by telemetry that caused the range safety to destruct the test vehicle. Early quick look would show the rolling vehicle which the mind would say is due to the control package. Its the video which would show the partial wing deployment which caused the roll. Anyway its good they isolated the root cause. Now they need to dig deeper as to why the bushing was allowed out of spec. and take systematic corrective action.

I agree the PDC are pulled right out of the air and some higher authority should have stepped in.
Also world over they are called ECD (Estimated Completion Date). Why come up with new acronym?
One thing I didn't like is the reporter calling up director Aero (D) who has a lot to do during this investigation and writing as if D Aero owes him an input!!!! Would suggest D Aero change his cell number.

For Nirbhay, the booster comes from ASL (Hyderabad); while the thrust vector control system and INS is from RCI (Hyderabad) and the launcher from R&D Engineers (Pune). The booster is designed by ASL (Hyderabad); the propellant comes from HEMRL (Pune) and the power plant is from a foreign source. The missile’s total system design and integration is done at ADE, Bengaluru.

Very good usage of resources and subject/domain knowledge expertise. The pyro bolts for separation are also from ARDE?

some one asked me why didnt the INS recover once the wing came back. Once frame of reference is lost its lost. So my analogy was the partial wing spun the missile and cause loss of frame of reference. Its like spinning a person in a dark room and telling him to head to the door without lights on.

There is no GPS to realign. And don't want it in a strategic weapon.

From an amateur understanding of INS, and the description, it appears that its likely not a full INS, but a system that is closely coupled to 'acceptable vehicle dynamics'. This makes sense as the missile is not supposed to do acrobatics but stay in a very tight aerodynamic profile. Lastly, the INS here likely failed in figuring out the 'attitude' of the vehicle, even if the location is known, its the 'pose' or the attitude of the vehicle which will determine the control inputs. The pose went haywire, the INS lost its frame of reference and control inputs could not be generated to realign the vehicle.

Finally, GPS should be used in missiles such as these. Even if GPS is denied over enemy airspace, in our own airspace, it should be available. Even if satellite are shot down, we can have 'pseudolites', ground based or aircraft based beacons using the GPS signal structure, using which location can be accurately computed by receivers. A weapons grade INS will anyday be thousands of times more costly than a GPS receiver.

[ramana]

I think those way points are to take out Nasr. A tactical missile to take out TNWS. Hence need robust non spoof able navigation. Maybe MINGS will get added if not already.
So full capability RLG and not a limited one.
Nirbhay is not post Cold War cruise missile. It has definitely purpose for India.

[JayS]

Hmm. Noob question. This INS going out of reference is interesting. Why couldn't the INS keep track of its motion whatever manoeuvres the missile might have went from..?? II don't think the missile would have gone through any violent manoeuvre as such. Why couldn't the INS keep track of attitude and position..?? It is suppose to do that exact thing. (Someone above gave analogy of Blinded man in dark room. If the man has accurate enough INS system built into him there is no reason why he should feel disoriented. He feels disoriented precisely because his natural INS has failed to keep track of his motion from the reference point when he started spinning). Is it by design?? If so why would they use such limited capability HW for a strategic weapon system..??

And why would the missile not has a GPS-INS integration to re-configure INS once its out of reference..?? Yes, GPS or such system may not be available all the time, but why not just have it as an option anyway. If signal is available use it, if not the missile was doomed to go down anyway. We now have multiple constellations available, including IRNSS, to augment and increase accuracy.

[sudeepj]

Hmm. Noob question. This INS going out of reference is interesting. Why couldn't the INS keep track of its motion whatever manoeuvres the missile might have went from..?? II don't think the missile would have gone through any violent manoeuvre as such. Why couldn't the INS keep track of attitude and position..?? It is suppose to do that exact thing. (Someone above gave analogy of Blinded man in dark room. If the man has accurate enough INS system built into him there is no reason why he should feel disoriented. He feels disoriented precisely because his natural INS has failed to keep track of his motion from the reference point when he started spinning). Is it by design?? If so why would they use such limited capability HW for a strategic weapon system..??

And why would the missile not has a GPS-INS integration to re-configure INS once its out of reference..?? Yes, GPS or such system may not be available all the time, but why not just have it as an option anyway. If signal is available use it, if not the missile was doomed to go down anyway. We now have multiple constellations available, including IRNSS, to augment and increase accuracy.

GPS is simply going to tell you the location, not the pose of the vehicle, as in is it upside down? is it banked at a 60 degree angle? Only the designers can answer all questions, but either the vehicle did not have a full INS with 360 degrees of freedom, or the software tracking the attitude did not know what to do with the vehicle in a bad state as indicated by the INS. Going by the description posted (INS lost its frame of reference), to me, it appears to be the former.

[JayS]

Hmm. Noob question. This INS going out of reference is interesting. Why couldn't the INS keep track of its motion whatever manoeuvres the missile might have went from..?? II don't think the missile would have gone through any violent manoeuvre as such. Why couldn't the INS keep track of attitude and position..?? It is suppose to do that exact thing. (Someone above gave analogy of Blinded man in dark room. If the man has accurate enough INS system built into him there is no reason why he should feel disoriented. He feels disoriented precisely because his natural INS has failed to keep track of his motion from the reference point when he started spinning). Is it by design?? If so why would they use such limited capability HW for a strategic weapon system..??

And why would the missile not has a GPS-INS integration to re-configure INS once its out of reference..?? Yes, GPS or such system may not be available all the time, but why not just have it as an option anyway. If signal is available use it, if not the missile was doomed to go down anyway. We now have multiple constellations available, including IRNSS, to augment and increase accuracy.

GPS is simply going to tell you the location, not the pose of the vehicle, as in is it upside down? is it banked at a 60 degree angle? Only the designers can answer all questions, but either the vehicle did not have a full INS with 360 degrees of freedom, or the software tracking the attitude did not know what to do with the vehicle in a bad state as indicated by the INS. Going by the description posted (INS lost its frame of reference), to me, it appears to be the former.

Yes. For attitude, its only INS that can play a part. I also think its perhaps HW deficiency. But then why would they have limited capability there..?? Is INS HW costly??

[Cybaru]

Nice read on missiles and INS http://techdigest.jhuapl.edu/td/td2804/bezick.pdf

[Cybaru]

Interesting they are not onboarding GPS or not using the signal at all assuming that GPS will be jammed by players.

[tsarkar]

Hmm. Noob question. This INS going out of reference is interesting. Why couldn't the INS keep track of its motion whatever manoeuvres the missile might have went from..?? II don't think the missile would have gone through any violent manoeuvre as such. Why couldn't the INS keep track of attitude and position..?? It is suppose to do that exact thing. (Someone above gave analogy of Blinded man in dark room. If the man has accurate enough INS system built into him there is no reason why he should feel disoriented. He feels disoriented precisely because his natural INS has failed to keep track of his motion from the reference point when he started spinning). Is it by design?? If so why would they use such limited capability HW for a strategic weapon system..??

And why would the missile not has a GPS-INS integration to re-configure INS once its out of reference..?? Yes, GPS or such system may not be available all the time, but why not just have it as an option anyway. If signal is available use it, if not the missile was doomed to go down anyway. We now have multiple constellations available, including IRNSS, to augment and increase accuracy.

Very General Answer - if the rate of disorientation data is more than the rate at which the guidance system can ingest and process that data, then failure will occur.

I've seen this in both military and civilian systems.

In the event of, say severe storm winds, buffeting the missile, the INS+GPS won't be able to keep the missile on course.

The best in class INS + GPS can correct drift - that is much less in magnitude than the disorientation caused by a failed control surface

Which is why met systems like DIGICORA are part of Pinaka or ground launched BrahMos regiments to ensure launch is within met parameters.

http://www.bemlindia.com/documents/Prod ... roject.pdf

Ships have met data from survey ships / satellites like INSAT/OCEANSAT etc.

A cruise missile like Tomahawk or Nirbhay or Babur is just powered glider optimised for endurance incapable of manoeuvres that a Harpoon or BrahMos can.

[JayS]

Very General Answer - if the rate of disorientation data is more than the rate at which the guidance system can ingest and process that data, then failure will occur.

What I am wondering is why is the INS not capable to handle this kind of situation for cruise missile. Is the INS HW cost too much (HW might exists with the capability but cost may be too much)?? Is it too difficult to write the SW algorithm (I am pretty sure its not this one). What exactly is stopping the designers to have the capability..??

[ramana]

Yes to both.

DRDO has given its answers after investigations that INS lost frame of reference when the partial wing deployment. As an academic exercise have Vivek bhai check if roll moment is induced with wings skewed at 60 degrees. One person said yes it will induce out of plane moments.

[Guddu]

Does India have its own GPS capability over China for missile guidance?...how difficult is it for China to take it out ?

[ramana]

Look at GPS satellite orbit. Look at signal strength. See how it's signal can be jammed. Then realize RLG pus MINGS is with multiple star sighting is best option.

[Indranil]

With guided rockets achieving such high levels of accuracy, it is time to develop long range rocket powered air to ground munitions. Something like IMI's MARS.

[Rishi Verma]

I don't buy the root cause as explained. Winglet didn't deploy so INS got disoriented is not sufficient. INS kicks in much later after stable flight using ground based reference signals (a CM is launched over friendly territory or friendly waters).

Sequence is 1) canister launch with a violent kick in the butt 2) leveling maneuvers 3) motors start 4) wings deployed 5) reference signal detect 6) INS reset, begins calculations 7) chase the first way point

(the INS has several classified inputs to allow resetting the error signal to zero, need not be GPS)

The RCA is not complete unless, what failed, and why it failed, and it leads what design improvements . Someone said "tolerances". Could be a spring mount, could be basic design fu*k up, It's hard to know because the missile was destroyed.

The simplistic RCA came out too fast to stop media or management backlash. I don't buy it, it's never that simple.

[shiv]

DRDO has given its answers after investigations that INS lost frame of reference when the partial wing deployment. As an academic exercise have Vivek bhai check if roll moment is induced with wings skewed at 60 degrees. One person said yes it will induce out of plane moments.

Not an expert but in highly swept wings there is a stream of air that moves along the leading edge which can be directed over the wing by means of a wing fence such as the one that can be seen on Su-7 wings. When wings are skewed with one angled forward and one backward - the one pointing forwards has air moving towards the fuselage and then going over the wing - producing more lift. In the case of the backward pointing wing the same leading edge stream of air moves outwards and simply bleeds off the trailing end - so this wing has less lift than the other. The vehicle will roll towards the side of the wing that is pointing backwards. Once it rolls it will also turn, lose altitude and stall.

[Indranil]

You are right Hakeem. Not only will there be differential lift, but differential drag as well. So there will be yaw moment as well. One you have these roll or yaw you will also have pitch moments.

Rishi sir, your 3 and 4 are definitely reversed on ALL modern surface launched cruise missiles. The booster covers the engine's exhaust and hence the engine cannot be started before the booster is separated. The deployment of the wing is a sub second affair and bringing the engine online is a matter of a few seconds. So even if the command to start the engine and deploy the wing is issued simultaneously, the latter is completed earlier. This allows the cigar shaped projectile to maintain altitude and attain much more stability as the engine powers up. I am also curious to know what the INS should reset against? It is an incredibly sensitive to deviation. So, I am curious to know what you are suggesting.

[Cybaru]

I would think INS needs to be ON from ground. Simplistically, its synced on ground, it shows delta as it moves forward which allows the calculations to target.

[shiv]

Maybe I am wrong - but an "inertial navigation system" (INS) is based on a gyro that acts like a 3 axis stabilized compass mounted on a platform by physically maintaining a mass oriented in one direction onlee while any movement of the mounting is detected as a change in direction. It does not need external inputs but multiple violent and sudden changes of direction could disorient a gyro.

But even with a shock resistant gyrocompass - if the machine itself can't fly and goes into a spin - the control inputs from the gyrocompass may be completely ineffective.

[tsarkar]

^^ INS are accelerometers and ring laser gyros/fibre optic gyros with GPS receivers to periodically calibrate.

Most mobile phones today have accelerometers and GPS receivers.

[ramana]

Kurup Thanks. So it's a cinch. K4 was tested at minimum range on or near 31 March 2016 from INS Arihant.

[ashishvikas]

RCA: Nirbhay wing deployment

https://giphy.com/gifs/26gs770V4KXk8Ys6Y

*Link updated.

[pralay]

@ashishvikas that link is not working without loggin in to dfi

[shiv]

RCA: Nirbhay wing deployment

http://defenceforumindia.com/forum/atta ... gif.13067/

Aaah - that man was not there to deploy the wing

[prasannasimha]

Inertial navigation is based on current location and adds on incrementally to the new position using a gyro to maintain true "North" and accelerometers to determine the deviation from the said "North" It is subject to errors like integration drift or rapid alteration in motion faster than acquisition/sampling time. If there was a massive roll it would be faster than acquisition time and so the control surfaces etc would not be able to work as it would not know its 3 D attitude and would be unable to compensate for the same. Remember the inertial navigation system is based on known position and the delta which is summated to it to calculate its new position. That is why they need a second method of correction like star sighting (not possible in cruise missiles generally) or terrain matching or GPS is added on to it as over time errors accumulate. It is generally never used in isolation

[prasannasimha]

^^ The order of accuracy and sampling rates for the missile INS and GPS are obviously much higher than what is provided by mobile phones. In fact if you notice Google initially did not provide positions within buildings on Google maps. They have now tried to provide that data by virtual INS combined with wifi signals , cell phone tower data etc etc to improve location within buildings. All of these things are ofshoots from military requirements but are downgraded for civilian use. We are not getting military grade GPS signals so we had to get RNSS and do not forget the famous "Blip" in the GPS of the first Nirbhay trial which probably made the developers a bit shy to use GPS updating etc

[Rishi Verma]

Rishi sir, This allows the cigar shaped projectile to maintain altitude and attain much more stability as the engine powers up. I am also curious to know what the INS should reset against? It is an incredibly sensitive to deviation. So, I am curious to know what you are suggesting.

No sir for me either. It's true that entire startup seq is less than a second - we have all seen the videos. What I said (not suggesting) is not the INS system but the error signal is reset to zero based on radio signals from ground after the violent ejection and after level flight is attained.
Error signal always accumulutes unless a reference (landmark-map matching, GPS, radio beacon etc) tell the vehicle exactly where and in which orientation it is (speed / direction of motion are computed on-board). In case of Nirbhay's radio signals are used initially but other tricks are employed as well during the course of the flight.

[chetak]

I would think INS needs to be ON from ground. Simplistically, its synced on ground, it shows delta as it moves forward which allows the calculations to target.

The INS needs to stabilize before launch either from manually entered coordinates or from a GPS signal before it wakes up "aware" of its initial position, time, altitude etc. Is it ring laser gyro based??

I doubt if the INS can stabilize whilst in motion because what would be it's initial reference?? Disclaimer: My knowledge may be scant on the latest technologies.

what other "classified" inputs can there be to the INS platform.?? target coordinates?? way points?? or some sort of scene matching, area correlation thingee??

The INS is a fairly straight forward technology, a well understood and a reasonably matured system.

[chetak]

Rishi sir, This allows the cigar shaped projectile to maintain altitude and attain much more stability as the engine powers up. I am also curious to know what the INS should reset against? It is an incredibly sensitive to deviation. So, I am curious to know what you are suggesting.

No sir for me either. It's true that entire startup seq is less than a second - we have all seen the videos. What I said (not suggesting) is not the INS system but the error signal is reset to zero based on radio signals from ground after the violent ejection and after level flight is attained.
Error signal always accumulutes unless a reference (landmark-map matching, GPS, radio beacon etc) tell the vehicle exactly where and in which orientation it is (speed / direction of motion are computed on-board). In case of Nirbhay's radio signals are used initially but other tricks are employed as well during the course of the flight.

If there is no "correction" inputs to the INS, as in the case of GPS signal loss or whatever other external radio/satellite inputs loss, the INS goes into a "dead reckoning" mode using time, vehicle speed, heading, altitude if coming from a RADALT or BARALT to compute its position. Errors of the INS (as also tolerances from the sensors) will tend to become cumulative and integrity of navigational data may be significantly compromised / deteriorate over the period of flight.

This INS however has to know it's initial position before launch.

[chetak]

Indranil, 18 months is too short finding root cause in an aero development failure.

ramanaji,

it may sometimes be "root causes" plural instead of singular.

the telemetry would have produced a lot of feedback for analysis. If everything has been destroyed, then only the telemetry data remains. lets hope that they have had clean inputs from the exact failure system/sensor or the root cause analysis may wind up with a complicated multiple cause possibility scenario.

If winglets hadn't deployed and the vehicle was thus not stabilized to requirements, the INS may require/have limitations of some sort of roll/pitch (rate??) tolerances which may have been exceeded causing it to give erroneous/no outputs to the flight control system.

If this was the case, then the design FMEA and also the potential failure modes and effects analysis may merit a re look.

The proof of the root cause pudding is as always, in the eating, which means that the "effectiveness" of a successful root cause fix HAS to be evaluated before the problem is considered solved. This may take time.

It would also be safe to assume that the INS platform and / or system would be duplicated (or more) and multiple systems would be polled to check that the validity of nav inputs from each system is within specified limits for use.