The ATV Unbound Part III: The SL-Missile Question

Part III of The ATV Unbound – compiled excerpts on the ATV by a group of retired Naval officers:

Lest someone think that we already have the Agni and the Prithvi and could we not simply deploy one of the versions of the Agni or the Prithvi on a nuclear sub, it should be clearly understood that a missile launched underwater from a submarine is a far more complex thing than a missile of similar range and payload fired from land or air. A SLBM (submarine launched ballistic missile) is qualitatively different from a land-based ICBM.

Firstly, no version of the Agni qualifies as a true ICBM. Secondly, there are important design differences in a land-based ICBM and a SLBM. All long range rockets are what is known as multi-stage rockets. In a land-based rocket, when you stack the stages upon each other, the rocket becomes long. But height is not a problem on land. This becomes a very serious problem in a submarine.

A major part of the research in making a SLBM revolves around developing design and technologies that would result in a short stubby missile which would be able to deliver the warheads of nearly the same gross weight to roughly the same range. The LGM-30 Minuteman III ICBM of the USA, a three-stage rocket, is nearly 60 feet tall but only 65 inches thick. It has a range of over 6000 miles. On their biggest nuclear sub, the Ohio class SSBN also the Americans have been able to deploy their Trident-II D-5 SLBM which had to be limited to only 44 feet height. And yet it is 74 inch wide. The Trident is still nearly 58.5 tons in weight whereas the Minutemen is only 32.1 tons. Yet the Trident has a range of only 4600 miles. This shows how difficult it is to design a short ICBM for a submarine even for those nations which have vast experience in this field.

There is one more problem for a SLBM. Inside a submarine you cannot fire its rocket engine. This means that it has to be cold launched, that is, expelled by the pressure of expanding cold gas in the launch tube. The technology of cold launch in itself is quite complicated. Then the SLBM has to traverse a depth of water before it can break free and fly in the air. While it is moving through the water, it is subjected to a great many disturbances as against a land-fired ICBM which flies into the air on its set trajectory from the word go. This makes the guidance system of the SLBM far more complicated and has to be much more sophisticated.

It should be clear that making a SLBM is far more difficult than making a regular land-fired ICBM. The same argument applies to any missile that is fired from the submarine. Even if you are firing a small missile of say 300 miles range from a SSN, the missile has to be technologically more sophisticated than a corresponding land-fired missile. For example, the guidance system of the missile has to be better.

Thus one should not think that if we have a missile of 300 miles range, it automatically enables us to have a submarine launched missile of the same range. They are different ball games altogether. In fact, making submarine launch capable missiles is proving to be as difficult as making the submarine itself.

A nuke sub is a dud if you cannot fire a respectable missile from it. Making a proper ICBM fired from the sub is beyond our immediate and mid-term capability. We do not have even a land-based ICBM in the mid-term. This means that a submarine launched ICBM is ruled out. Could they be thinking in terms of an IRBM? Will that be feasible? Let us examine that.

The INS Chakra, a Charlie II class sub, was a cruise missile firing submarine. It has been argued that since our basic design data came from the INS Chakra, perhaps we would not be able to deviate materially from that.

The Sagarika has been identified as either a submarine launched cruise or ballistic missile with a range of 300 km. The project began in 1994. It was slated to be completed by 2005. It has been reportedly test-fired once this year.

According to the Asian Defense Journal (5/95, p. 20-27): “India is testing scale models of a submarine-launched ballistic missile (SLBM) Sagarika in wind tunnels at the Aeronautical Defense Establishment (ADE), a part of DRDO. The project initiated some three years ago (1992), is aimed at building a SLBM which will be carried on an indigenous nuclear submarine. The missile, which in some respects will be similar to Prithvi, will be able to hit targets as far away as 300 km.” The same journal reported that if it were to be a cruise missile then it would be designed to carry a warhead of 450 kg.

Among the major problems associated with such a system are the effects of water in the nozzle on motor ignition. (AIAA Missile Sciences Conference, 1990, A.K. Whitney, CFD Analysis of Reentrant Water Jets and AIAA Missiles Sciences Conference, 1993, C.Y. Tsai, Motor Ignition with Water in the Nozzle). In fact, this effect had caused the failure of two out of three flights of the US Trident II missile.

Lest someone think that we have been proudly displaying our Agni and Prithvi missile in our Republic day parades, it must be clarified that the Indian missiles like Prithvi and Agni have yet to make their mark as accurate missiles. They have propulsion systems alright, they can cover the distance alright but hitting the target is once again a different ball game altogether. The Prithvi is reported to have a relatively high circular error probable (CEP) — 300 meters at 150 km range and 500 meters at 250 km range, (0.2 percent of the range). Efforts to reduce it to an acceptable level have not been successful, which is why the Army has set up Project Bheeshma to sort out the problems. There is an additional problem. The Prithvi’s liquid fuel poses liabilities as a delivery system. The liquid propellant mixture is highly volatile and corrosive and must be loaded just prior to launch. This is not a missile which you can keep ready to fire any moment. And filling the propellant is a specialized operation requiring specially trained personnel. There is no indication as yet as to how are they going to solve these problems for the submarine launched version.

Accuracy problems have plagued the Agni also, official claims notwithstanding. In any case, Agni cannot even be considered for the submarine. Initially the CEP was said to be about 100 meters. The CEP of 100 meters meant that the missile would only strike within 100 meters of its target 50% of the time. The DRDO’s Chief Controller of R&D (Missile Division), A.S. Pillai, stated after the Agni-II test, “We have improved accuracy by a factor of at least three. It is a far more lethal missile now.” A Japanese newspaper report stated that Agni-II achieved a Circular Error Probability of 40 meters. All international experts, however, agree that more future tests would be required to substantiate the computer simulations that India used to produce this figure.

Prithvi was made to dabble with a radio-correction guidance system also. Whether such technology can be transferred over to the SLBM project remains to be seen. Many analysts maintain that if all these attempts fail, the nuke sub could end up using nothing but the Yakhont anti-ship cruise missile designed by NPO Mashinostroyeniya. In the absence of a reliable missile, it appears that even if the submarine becomes seaworthy, it would be like going to battle on a horse without a sword or lance in hand!

The program of building the submarine launched missile called Sagarika started in 1992 and was originally reported to involve adapting a ramjet engine to the missile to reduce the need for heavy oxidizers. But according to other sources and official papers published between 25-31 July 94, the Sagarika is fashioned after the Prithvi.

Interestingly, the New York Times reported in April 1998 that Russia was helping India build a nuclear-capable sea-launched missile called the Sagarika. Both India and Russia denied cooperating on the project, but India reportedly confirmed in 1999 that its Aeronautical Development Establishment (ADE) was developing a 300-kilometer range cruise missile. According to the Times, Russia acknowledged to American officials in 1995 that Russian scientists were providing India with technological support, but insisted that their assistance was limited and involved only the technology needed to launch an underwater missile. However, an American official told the Times that Russia was providing “significant engineering services” as well as the parts and equipment necessary to build and launch the missile.

Now there is little doubt that the Sagarika missile is being developed by India’s Aeronautical Development Establishment (ADE) in Bangalore with Russian assistance. In fact the project itself was initially believed to have been headed by a Russian scientist. Officially of course, the Russians are still vague about it. On record, senior NPOM official — Russia’s state-supported cruise missile and space technology design bureau — said that although Russian scientist had provided critical hardware for the guidance system, they had no connection with developing the Sagarika as a nuclear deterrent.

No one knows for sure whether it is going to be a cruise missile or a ballistic missile. Some observers have concluded that it will be made in two versions, both as a cruise missile and as a ballistic missile with a range of about 300 km.

As a cruise missile it has to be like a Tomahawk cruise missile or a little smaller version of that without our having ever demonstrated the capability of coming anywhere near the technology.
The first flight trial of the cruise missile version is claimed to take place sometime during this year. The engine is likely to be a turbojet with a solid fuel booster. The missile will be vertically launched. Now there are serious doubts about whether we would be able to build a turbo jet or turbo fan engine small enough for the missile and yet giving sufficient thrust. Our efforts on the Kaveri engine for the LCA have singularly failed so far and we are not known to have developed any other engine. Once again, as is the case with the reactor, it is not just a matter of scaling down.

Problems will also have to be overcome in respect of the so-called switchover mechanism, which enables a missile to settle into a cruise phase after takeoff with a solid-fuel booster. Help was sought from Israel as well as some European/Russian missile firms in 2001. The help was also intended to increase the range of the missile from the pathetic 300 km to a respectable 1000-2500 km so that the deterrence has some credibility.

The guidance system of the missile was supposed to be upgraded with the help of Russian scientists from the NPOM. But it is not known whether even with Russian help we have reached anywhere near incorporating the terrain-contour-matching (TERCOM) and digital scene-matching area-correlation (DSMAC) missile-guidance systems. Most probably not. In any case there have been no test flights. It may be recalled that the Americans love to show the video films of their cruise missiles hitting targets with pin-point accuracy.

One more thing may be kept in mind. We all know how jittery the Americans are about such missiles being developed in the rest of the world. The U.S. Air Force National Air Intelligence Center’s 1999 report on missile proliferation does not list India among the countries able to build cruise missiles by 2009. Will Sagarika be able to do what it is expected to do?

The developmental cruise missile would carry conventional warheads. Eventual long-range versions would have to be nuclear-capable. Otherwise we would simply be wasting our time, money and effort. The point to be noted is that there could be nothing more foolish than firing a conventional warhead on a land-based target from a submarine. If you have invested so much in a nuclear submarine, its worth will not be realized unless you have the capability of firing a nuclear warhead.

Coming to a nuclear warhead, the most vital point is its weight. Miniaturizing a nuclear warhead is enormously more difficult than just exploding a nuclear device. We have not yet produced any evidence of having become capable of making nuclear devices so small that they could be limited to the small payload of the Sagarika, i.e. about 450 kg. The missile launchers being built at Hazira, called Project 78, by L&t. Many believe the Sagarika is most likely a clone of the Prithvi series missiles. Prithvi-I and II are land-based and III, sea launched.

Sagarika would require some modification even in the sea launched version of Prithvi because launching from under water is materially different from launching from the surface of water. The problem is that even in the ballistic missile version, you do not have a nuclear warhead that is small and light enough to as its payload. The first underwater flight test was supposed to take place in September 2001. As was to be expected, nothing happened. Thus the ballistic missile version also is not very promising as an effective weapon system.

The Dhanush and the Sagarika programs remains obscure. Given the evident similarities in their overall characteristics, Dhanush may simply be the new name for the original Sagarika system. However, since the Dhanush is reported by some sources to have a 350 km range, compared to the 250-300 km range of the Sagarika, the change in designation might reflect a design change.

Dhanush is supposed to be a naval version of the Prithvi. The 8.5 meter long Dhanush, was tested on 11 April 2000 from the INS Subhadra anchored 20 kilometers offshore in the Bay of Bengal close to the Orissa coast. The test was reportedly described as only a “partial success” by V. K. Aatre, scientific advisor to the Ministry of Defence. Officials at the DRDO declined to provide specific details about the test, but naval sources reportedly said the missile crashed into the sea approximately 25-30 kilometers from the launch vessel. The missile flew for only four seconds and broke into two pieces, barely managing to clear the ship. It was promptly called a tech demonstrator.

The Indian Navy is apparently seeking another variant of the Dhanush surface-to-surface ballistic missile that is capable of striking land targets within a range of 500 km. The longer-range missile will have propulsion fuel similar to its short-range version.

There’s a shortpoint: If we don’t have at least a nuclear-tipped IRBM platform by the time the ATV hits water, there’s going to be no real point.

(Next, Who Does What, and What the Hull!)