Four other SSKs will follow in the wake of Khanderi, at intervals of nine months. However, none of them will be equipped with air-independent propulsion (AIP) systems of either indigenous or imported origin. This despite the DRDO’s Ambarnath-based Naval Materials Research Laboratory (NMRL), along with the Kochi-based Naval Physical and Oceanographic Laboratory (NPOL) initiating R & D on an AIP module way back in 2002. It may be recalled that the Govt of India’s Cabinet Committee on National Security has approved the procurement of six CM-2000 Scorpene SSKs in September 2005 at a total cost of Rs 18,798 crore (US$4.2 billion) and the contract was signed in October that year. The project cost was subsequently revised to Rs 23,562 crore in February 2010, along with a revision in delivery schedules. In 2010, it was envisaged that an indigenously-developed AIP module would be fitted on to the latter three of the six CM-2000s. However, a series of delayed decision-making processes thereafter caused all six CM-2000s to be bereft of the AIP modules.
While the DRDO was insisting that it will be able to deliver on-time a proven AIP solution as demanded by the Indian Navy, the MoD was unsuccessful in drafting a long-term industrial roadmap for new-generation SSK procurements by using the CM-2000 procurement effort as the foundation. By 2012 itself, when it was crystal-clear that the NMRL-developed AIP module was nowhere in sight for the latter three CM-2000s, the MoD should have approved the procurement of an additional three CM-2000s with the proviso that they be equipped with the NMRL-developed AIP module—especially when DCNS at that time was more than willing to invest US$100 million in the R & D programme in partnership with both the NMRL and Mazagon Dock Shipbuilders Ltd (MDL). Had such an option been approved, then even the first six CM-2000s could have been be retrofitted with such AIP modules during their subsequent mid-life refits.
Without snorting, a diesel-electric SSK can only expect to stay continuously submerged for a maximum of about 100 hours if cruising continuously at 4 Knots. The SSK must snorkel on a regular basis to preserve the charge in its main battery. The ratio of time spent snorkelling to not snorkelling is referred to as the INDISCRETION RATIO and will normally be kept as low as possible. Indiscretion ratios vary from 30% during transits to 5% for a SSK in an operational area. By and large, snorkelling is the Achilles Heel of the SSK, exposing it to counter-detection. Firstly, snorkelling requires a periscope/optronics mast, an ESM mast and a snorkel induction mast to be raised, all of which expose the SSK to enemy visual sensors and radar. It is possible for an enemy to detect masts and their plumes and wakes visually, particularly during the day. Visual counter-detection opportunities increase with the number of masts exposed, the speed of the SSK and the calmness of the sea. Designers try to minimise mast visual profiles by minimising mast sizes, using camouflage to blend masts into the background environment and streamlining masts to reduce plumes and wakes. Operators try to minimise plumes and wakes by minimising snorkelling speeds; a simple rule-of-thumb being Knots = sea state + one. Radar counter-detection is also a function of the number of masts exposed and the speed of the SSK, although good radar performance is not limited to daylight. Techniques used to minimise visual counter-detection generally work equally well in also minimising radar counter-detection. Additionally, radar absorbent material and shape optimisation are used. ESM masts and systems are employed to determine the presence of dangerous radar signals and masts are lowered when rackets approach dangerous levels. “Gulping” can be used to reduce visual/radar counter-detection opportunities, particularly in scenarios where there is a heavy airborne ASW presence, but a pressing need to snorkel. “Gulping” involves raising the snorkelling mast just above the surface of the water. Wave action results in the mast washing over from time to time—which causes discomfort to the crew as vacuums are pulled inside the SSK and then released on an alternating basis. Despite all the methods employed by submariners to minimise counter-detection while snorkelling, modern optronic systems and periscope detection radars, particularly airborne, still present challenges to submariners. Another significant snorkelling counter-detection source stems from running diesels and associated equipment noises. Snorkelling can increase a SSK’s acoustics radiate noise source-level between 20 and 30 decibels. Assuming propagation losses of six decibels per doubling of range, and all other things being equal, the acoustic counter-detection ranges of a snorkelling SSK can increase eight- to 16- fold! Of course, SSK Commanding Officers will take advantage of any increases in ambient noise such as that caused by evening or fish choruses and heavy rain. They will also top up the battery packs with short snorkellings whenever tactically possible. Nonetheless, snorkelling presents significant challenges to SSK commanders. AIP-equipped SSKs don’t have the same Achilles Heel as diesel-electric SSKs. Whilst conventional AIP systems don’t assist SSKs in transits or in high-speed runs, they do allow them to operate at low-speed for up to three weeks (or 504 hours) without the need to snorkel.
For most land-based applications, a fuel cell uses oxygen from the air as the oxidant since this saves the weight and volume of having to carry an oxygen source. However, for SSK applications, oxygen must be carried. A disadvantage of a fuel cell-based AIP system that uses a reformate gas as opposed to pure hydrogen is that the reforming system will have a higher oxygen demand. This is because, in addition to operating the fuel cell, oxygen is also required to reform the liquid fuel into hydrogen, either for partial oxidation reforming or to burn a small proportion of the fuel or off-gas to provide the heat for steam reformation. This extra oxygen requirement must be factored into any calculations. A further complication of reforming systems is that carbon dioxide is also produced as a byproduct of the reaction and this needs to be stored or disposed of safely and discretely. Carbon dioxide has a high solubility in water and, if necessary, can be discharged without producing bubbles by pre-dissolving the gas. Liquid fuels, such as methanol and diesel, have the advantages that they are readily available, may be stored in tanks and have a high-energy density. Often, these advantages outweigh the complications introduced by a reformer. Carbon monoxide is a potential byproduct of the reformation process. This is a reversible poison for the platinum catalyst used in PEM fuel cells (of the type developed by Siemens of Germany) and therefore purification of the gas is required before it is fed to the fuel cell.
The DRDO’s Ambarnath-based Naval Materials Research Laboratory (NMRL), along with the Kochi-based Naval Physical and Oceanographic Laboratory (NPOL), have since 2002 been trying to develop an on-shore AIP system that will enable an SSK to stay submerged continuously for about 25 days. The methanol-based steam reforming system suitable for a SSK needs comprises a storage vessel for methanol, a storage vessel for oxygen, a steam reformer assembly, a gas purification stage, and a carbon dioxide handling system. Methanol is a liquid at room temperature and can be stored in tanks. The methanol will be consumed as it is used by the NMRL-developed Borohydride Hydrolysis/Phosphoric Acid-based fuel cell, and a hard conformal tank requires compensation to accommodate the changing volume to prevent it from collapsing. Direct water contact with methanol is unacceptable because the two are miscible. External storage of methanol in soft conformal bags is now being tried out. The bags are fabricated from methanol-resistant material and, during operation, the seawater naturally displaces the consumed methanol without coming into contact with it. Methanol is a toxic, flammable liquid that burns without a flame, but is easily contained and therefore, if the system is correctly designed, it should not pose a safety hazard. There is also considerable interest in methanol reformer systems for use in automobiles and buses. Alcohols and hydrocarbons can, in theory, act as fuel for a fuel cell and be directly oxidised like hydrogen. One of the commonest fuels of this type is methanol, which is used in the Direct Methanol Fuel Cell (DMFC) of the type now being developed by Germany’s HDW.
However, no significant R & D breakthroughs have been achieved by the NMRL nor are they expected to be achieved in the latter half of the decade. To date, only 30% of the required test-points have been obtained, despite the shore-based AIP module being in operation as a technology demonstrator since 2011. Apart from the NMRL and NPOL, other DRDO laboratories and industrial entities that are involved with this R & D venture are Larsen & Toubro, THERMAX, IOCL, TEXOL, Indian Institute of Petroleum, AKSA, CEEFES, C-DAC, DIGITRONICS, NSTL, RCI, ROLTA and MDL.
The Messy Project 75I
As of now, there is no clarity within either the MoD or Naval HQ on what Project 75I is all about and how it ought to proceed. For instance, while Naval HQ on one hand is insisting that the six SSKs of imported design under this project must be equipped with indigenous AIP modules and the SSK hulls must be built with indigenously produced DMR-292A steel (all six CM-2000 Scorpenes are built with HLES-80 high-yield stress-specific steel supplied by ArcelorMittal, which will allow the SSKs to reach diving depths of up to 300 metres/1,150 feet and achieve an average of 240 days at sea per year per submarine), it is now also clamouring for financial sanction for procuring six indigenously designed and built nuclear attack submarines (SSN).
Now, if an all-new imported SSK design is to be chosen for Project 75I, it would mean that hull-design selection cannot take place unless and until the indigenous AIP module emerges as a proven solution. Add to that the time taken for such an AIP module to be integrated with the selected hull-design after a lengthy process of sea-trials (which can last for up to four years for the lead boat). Consequently, if one is to believe the NMRL’s assurances of a full proven AIP module being available by 2020, then the RfP for procuring the six AIP-equipped SSKs will not be released until 2018 at best, and the first AIP-equipped SSK will not enter service before 2026 at best. What further complicates matters is that the NMRL-developed AIP module presently has structural dimensions and electro-mechanical interfaces tailor-made for seamless integration with the CM-2000 Scorpene’s hull.
Both common-sense and logic therefore demand that the scope of Project 75I be limited to the immediate procurement of only three additional CM-2000 Scorpene SSKs all equipped with the indigenous AIP modules.