Incomparable indigenous RLGs — French no match; see!!

Going to France for ring laser gyros as navaid for the Brahmos cruise missile is a ridiculous thing the Indian govt has done. Whether the Minister of State for Defence Rao Inderjit Singh even understood what he was actually asking for when he requested the French defence minister Jean-Yves Le Drian for technology assistance with the ring laser gyro as guidance system on the Brahmos is doubtful. He would have merely learnt by rote from a note given him by the Ministry of Defence (MOD) before regurgitating it to the Frenchman.

Minister Inderjit was in Paris for the Air Show where the Pakistan Air Force flew its JF-17, the 4- gen aircraft and managed to snag several customers — at a time when the Indian govt is sitting on the sidelines confused and baffled about the best way to proceed on the 4.5 generation Tejas LCA which only needs a determined govt push to get it into IAF squadrons and for it to draw interest from a whole host of states that would be keen to buy it. Incidentally, the states that have shown definite interest in the Sino-Pak JF-17 include Nigeria and Sri Lanka.

Is this junior minister or, for that matter, the Union minister for defence Manohar Parrikar aware that (1) the Agni-prgramme head GV Sekaran-produced ring laser gyro (RLG) the technology base for the country’s Mangalayan Mars probe? If this RLG can get the Indian space vehicle on a “slingshot”course to the distant red planet on the first try, you think it will face problems getting the Brahmos dead on a terrestrial target? (2) the Indian-made RLG outfits both the Agni ballistic missiles and the Shourya and the K-15 boost-glide missiles. (3) the RLGs on ballistic missiles, as experts will tell you, have to have very high axial accelerations capability. On the other hand, cruise missiles (CMs)/boost glide vehicles (BGVs) require a very high lateral accelerations capability in order to pull-off maneuvers by the vehicle. More specifically, for violent maneuvers, the RLG needs to have a very high tolerance which translates into low % error as a function of G’s pulled. Further, in CM’s and BGV’s, the RLG is usually the primary navigation unit, especially in an intense ECM environment such as GPS jamming, spoofing, etc. Equipped thus on the Shaurya and K-15 (both BGV’s), the RLG works just fine. BGV’s are what scares everybody. This is because they are virtually impossible to intercept by any ABM system.

The stories rife in certain GOI/MOD circles that the Indian RLGs have greater axial tolerance but lack sufficient lateral tolerance are, therefore, so much motivated poppycock!

There is visual record of the RLG helping Brahmos prosecute the impossibly difficult S maneuver and punch a hole through a small triangular metal plate on a wall (and the wall itself). The exercise was to simulate an attack on a hypothetical chemical weapons plant on enemy territory. This does not seem like a RLG with an inferior lateral performance. And this video was circa: 2010. The Indian RLGs have been improved since then and ECM jamming might very well have be factored into them. The guys at the Sekaran outfit are damned good. See the video clip and judge for yourself Mr Parrikar and other doubting Thomases! Watch it at


The French item, say, Sagem RLG in contention looks like this:

It is unlikely the Indian RLG performance can be bettered in any flight envelope and is definitely miles better than the French item. In the event, going to France for this technology when a far better and proven technology is available at home seems like suppression of an already developed indigenous capability and wasting national wealth.
P.S.: The person who designed the algorithm for the “Kalman filters” to help the BGVs pull very violent maneuvers and to detect incorrect sensor inputs is a desi who once worked in an Indian R&D dept, was hounded out of it, and is now sought by and works on contract basis with top scientific R&D orgs in Asia and elsewhere. So much for the Indian govt nursing Indian talent for national good!

About Bharat Karnad

Senior Fellow in National Security Studies at the Centre for Policy Research, New Delhi, he was Member of the (1st) National Security Advisory Board and the Nuclear Doctrine-drafting Group, and author, among other books of, 'Nuclear Weapons and Indian Security: The Realist Foundations of Strategy', 'India's Nuclear Policy' and most recently, 'Why India is Not a Great Power (Yet)'. Educated at the University of California (undergrad and grad), he was Visiting Scholar at Princeton University, University of Pennsylvania, the Shanghai Institutes of International Studies, and Henry L. Stimson Center, Washington, DC.
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4 Responses to Incomparable indigenous RLGs — French no match; see!!

  1. archit says:

    wrong science: kalman filters not for manoevring. Incorrect analysis. RLG understanding incorrect

  2. According to experts, ‘Kalman filters’, besides being used for tracking, can also be used when the trajectory of the target can be inferred and assumptions cycled back into the loop.

  3. archit says:

    Kalman Filters: Its ONLY as good as the sensor/s input. see the maths, Which are different/ multiple in each phase of flight. Terminal accuracy is a function of lots more issues, which are not relevant here.

    basic RLG
    Do you suppose it wont work in one axis and will in the other? wrong

    Also, no great shakes making a RLG today. All IN/GPS are specialised modules made by specialists. As you have often argued on this blog and various commenters have observed economies of scale may prevent meaningful indian private investment.
    DRDO may well have asked for french technology for all you know.

  4. ~!@#$%^&*()_+ says:

    I had posted a reply to PMO based on your post above. But the crux is that any such grapevine campaign as is suggested by your claim “stories rife in certain GOI/MOD circles that the Indian RLGs have greater axial tolerance but lack sufficient lateral tolerance” is obviously a motivated campaign.

    All algorithms are by their very nature only as good as the sensor input. It is in the sensors that we lag. Any lag in the algorithms is only coincidental and not the crux of the problem. Indian researchers have time and again with multiple projects shown their skills and newer developments should not be found wanting because of an inability to understand basics. Sensor hardware on the other hand take longer and real money to develop. Resources that have perennially been denied invariably under influence of people who have neither designed nor often even fought wars with the equipment they had.

    Anyhow what I have been told and subsequently verified from papers available online, is that the Kalman Filters work best for linear systems – early Prithvis and Agnis – go up come down no difficult maneuvers. The algorithm, I was told simply estimates the current position by integrating the new measurement with the old position estimate. While the old position estimate already is carrying some factor of the old measurement and old estimate.

    Extended Kalman for non-linear systems like complex BGVs and longer ranged Akash fired from static Transporter-Erector-Launchers. But the real difficulty will be with highly complex problems like placing radars on ships, making cruise missiles that have multiple waypoint maneuvers with capacity to be launched from ships and aircrafts. Yet these too have been done by Indian researchers or are being convincingly pursued.

    Unscented Kalman filter based algorithms are meant for highly non-linear systems where even the initial system state and vector may be difficult to pin down. Or for cases where the costs are a limitations and people do not want to get into developing separate navigation models to control the large differences in the estimated vs actual initial states of their Extended Kalman Filters. Like Astra being launched from a highly maneuvering aircrafts that essentially put the whole system into a reset position with every roll/climb/yaw of the aircraft and where the aircraft fires their missiles merely in the general direction even without a true lock on or even in the reverse direction without any lock on. Even systems like the Dhanush and K-15, would face this problem of a difficult to pin down initial states though to a much smaller degree with the speculated non-linear Boost-Glide phase. Probably Dhanush was the start of our missile algorithm development of the more difficult kind. Thus these systems may not be there in as many numbers of may be there only on Brahmos with significant limitations but this is still no reason to simply import just for the heck of it.

    So essentially whispers that Indian sensors “lack sufficient lateral tolerance” is a lot of bull because most cases Indian researchers have not yet been tasked &/or funded for taking up these things.

    Remember Control Laws for LCA Tejas are all Indian and the Sonars are all Indian. Indian Navy infact maintains utmost secrecy for their algorithms pertaining to Sonars. They own the goddamn algorithm. ‘Own’ not ‘Import’-That is the crucial difference. Something amiss to these whisperers. – should help. And mind you NAL is not a secretive defence research organization.

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