Saturation Diving & Air Diving: The Cutting-edge Tech Behind INS Nistar

Amid rising maritime challenges in the Indian Ocean, the Indian Navy has launched a game-changer: INS Nistar. Commissioned on July 18, 2025, this advanced, indigenous diving support vessel embodies India's push for self-reliant defence. Its cutting-edge diving systems tackle bold missions-from submarine rescues to deep-sea salvage-relying on sophisticated saturation and air diving techniques that let crews operate safely in extreme conditions.

Understanding Saturation Diving

Saturation diving is designed for extended operations at depths often beyond 50 meters and up to 300 meters. It relies on saturating a diver's tissues with inert gases, allowing them to reach equilibrium with the surrounding pressure. Once saturated, additional time at depth doesn't increase decompression, allowing work for days or weeks with only one decompression at the end.

Divers live in pressurised chambers or habitats, breathing gas mixtures like heliox to prevent nitrogen narcosis and oxygen toxicity. Transfer to the worksite occurs via a closed diving bell that maintains pressure. This setup reduces health risks from repeated decompressions, such as 'the bends.' On INS Nistar, saturation diving uses advanced compression chambers and self-propelled hyperbaric lifeboats for operations up to 300 meters.

This technology transforms deep-water tasks. By reducing decompression cycles it improves efficiency and safety, making it essential for sustained underwater missions.

The Basics of Air Diving

Air diving, or surface-supplied diving, suits are suitable for shallower depths up to 50 meters. Divers use compressed air via an umbilical, which also provides power and communication. Dives are short, usually under an hour, with mandatory decompression stops.

Air diving requires a return to surface pressure after each session, limiting it to tasks that allow for quick ascents. Nitrogen narcosis is a risk at deeper depths. Its simplicity makes it ideal for routine work at moderate depths. INS Nistar supports air dives to 75 meters using side diving stages, complementing its capabilities.

Key Differences and Their Significance

The differences between saturation and air diving lie in their depth, duration, and physiological demands. Saturation diving excels in deep, extended missions by enabling weeks-long underwater stays without repeated decompression. In contrast, air diving is suited for shallower, shorter tasks, as divers must return to the surface after each session.

These differences provide operational flexibility. Saturation diving reduces risks in high-stakes situations, cutting decompression time and improving safety. Air diving offers cost-effective solutions for less demanding tasks. Together, they form a versatile naval toolkit for diverse underwater challenges.

Use Cases Aboard INS Nistar

INS Nistar, 118 meters long and over 10,000 tons, is a hub for these technologies, boosting the Navy's underwater capacity. In submarine rescues, saturation diving plays a crucial role. The vessel serves as the "mother ship" for deep submergence rescue vehicles, enabling divers to assist submarines at depths of up to 300 meters. It also utilises remotely operated vehicles for monitoring and salvage operations down to 1,000 meters, ensuring precise interventions in emergency situations.

Air diving excels in shallow salvage or maintenance, such as hull inspections or deploying equipment. For evacuation or rescue, air diving allows for quick assessments; saturation diving supports prolonged, deep recoveries. These capabilities, developed with over 80% domestic content and 120 MSMEs, highlight India's engineering excellence.

These methods go beyond tactics; they show strategic readiness. By mastering them, the Navy becomes a preferred regional rescue partner and fosters international cooperation. INS Nistar's technology ensures swift, effective responses to safeguard lives and assets.

INS Nistar showcases the Navy's forward-thinking approach, integrating advanced diving technology for modern warfare and humanitarian aid. As the first such vessel from Hindustan Shipyard Limited, it enhances capability and advances self-reliance under the Aatmanirbhar Bharat initiative. In the depths, saturation and air diving provide safety and efficiency, reinforcing the Navy's protective role.

(Aritra Banerjee is a Defence & Security columnist)