India has reportedly paused the acquisition of six additional Boeing P-8I maritime patrol aircraft due to rising costs driven by US tariffs, global inflation, and supply chain disruptions. This pause may also reflect a strategic response to changing US trade policies and tariff tensions.
If the US were to impose further trade restrictions or military sanctions, India’s Anti-Submarine Warfare (ASW) operations using the P-8I Poseidon could face serious challenges — especially since key components like sonobuoys are still imported from the United States. The question arises: Do we have a homegrown alternative if imports are cut off?
India has made progress. In a major step under the “Make in India” initiative, Bharat Dynamics Limited (BDL) partnered with US-based Ultra Maritime to co-produce sonobuoys for the Indian Navy. These will be manufactured under license at a new facility in Visakhapatnam, expected to be operational by 2027. This partnership ensures steady supply and partial indigenisation, but since the design belongs to Ultra Maritime, India could still be vulnerable if US sanctions take effect.
In 2025, a second landmark partnership between Adani Defence & Aerospace and Sparton (USA) made Adani the first Indian private-sector company to offer indigenised sonobuoy solutions. This collaboration combines Sparton’s advanced ASW technology with Adani’s large-scale manufacturing expertise. Yet, the fundamental question remains: When will India design and develop sonobuoys of its own?
Why Sonobuoys Matter
A sonobuoy is a floating electronic sensor dropped from an aircraft to detect and analyse underwater sounds — primarily to locate and track submarines. It consists of a radio-equipped surface float and a hydrophone that descends underwater to capture acoustic signals. These signals are transmitted wirelessly to ASW aircraft such as the P-8I, which analyse them to pinpoint submarine locations.
Both active and passive sonobuoys are used — the former emit sound pulses to detect echoes from submarines, while the latter listen silently for enemy movement. Together, they form the ears of an ASW aircraft.
Submarines, with their stealth and endurance, are among the most potent assets in modern warfare. They can gather intelligence, disrupt trade routes, and deliver nuclear strikes from undisclosed positions. Hence, long-range ASW aircraft like the P-8I Poseidon remain the most effective counter to this underwater threat.
Sonobuoys are not interchangeable between platforms — they are designed specifically for the ASW system that uses them, making indigenous development all the more critical.
How Sonobuoys Are Deployed
Airborne ASW aircraft like the P-8I deploy sonobuoys in carefully calculated patterns across large ocean areas, sometimes over 100 square kilometres, to encircle suspected submarine zones.
Passive sonobuoys simply listen to underwater sounds, while active ones emit sonar pulses and capture echoes. Both types relay data via radio signals to the aircraft overhead, where onboard computers process the acoustic patterns to estimate the submarine’s position, speed, and trajectory.
A sonobuoy is a floating electronic sensor dropped from an aircraft to detect and analyses underwater sounds — primarily to locate and track submarines. It consists of a radio-equipped surface float and a hydrophone that descends underwater to capture acoustic signals
Once deployed, sonobuoys float on the surface, transmitting signals while their underwater sensors descend to specific depths to gather sound data. This coordination allows the Navy to track enemy submarines in near real time.
Smart and Intelligent Sonobuoys
The next generation of sonobuoys will be autonomous and AI-enabled, capable of real-time detection, classification, and tracking of underwater threats.
Equipped with digital signal processors (DSPs), these smart buoys can filter noise, recognise echoes, and compress data before transmitting it. They can even switch between passive and active modes automatically when certain conditions are met.
By networking multiple buoys into a swarm, they can analyse data collectively, perform data fusion, and send a refined acoustic picture to the aircraft — all with minimal operator input. The result: faster detection, higher accuracy, and lower human workload in complex underwater environments.
Energy Efficiency and Power Algorithms
Smart sonobuoys must balance power consumption with operational endurance. New machine learning algorithms help optimise data transmission and sensor activity without sacrificing detection capability.
Techniques such as adaptive duty cycles, event-driven transmissions, and signal compression allow buoys to conserve battery life. Kalman filters further assist by predicting submarine motion, reducing the number of active sonar pings required and thus saving power.
Autonomous Drift and Positioning
Modern sonobuoys can use GPS-based navigation and drift management algorithms to maintain their position and adjust to ocean currents. By integrating predictive drift models and swarm coordination, they can reposition themselves autonomously for optimal coverage.
Future sonobuoys may even use micro-actuators or variable ballast systems to physically adjust position, improving tracking precision in dynamic maritime environments.
Filtering Underwater Noise
The ocean is full of sound — waves, marine life, and mechanical noise — making submarine detection difficult. Advanced sonobuoys now incorporate machine learning-based filters to separate useful signals from clutter.
They combine traditional static filters with adaptive spectral methods and deep learning networks such as Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs) to identify true submarine signatures in noisy conditions.
Swarm-Coordinated Sonobuoys
Swarm coordination represents the future of underwater surveillance. Instead of static deployment patterns, AI-enabled sonobuoys can communicate and adapt as a network, maximising coverage while minimizing the number of buoys needed.
These cooperative networks act like a self-optimizing underwater array, improving detection accuracy, range, and resilience — a leap forward from the traditional “drop-and-forget” model.
Battery and Power Innovations
Battery technology has advanced dramatically in recent years, driven by the electric vehicle revolution. Sonobuoys can now leverage lithium-thionyl chloride, lithium-seawater, solid-state lithium, silver-zinc, and hybrid battery systems combining batteries with super-capacitors.
These new designs increase energy density, extend operational life, and enhance safety — ensuring sonobuoys stay functional for longer missions.
Harnessing Renewable Ocean Energy
A promising idea for the future is to power sonobuoys using renewable ocean energy. Integrated micro-turbines, solar panels, fuel cells, or wave energy harvesters could provide sustainable, long-duration power for extended ASW operations.
It is time for the Indian Navy, DRDO, and domestic defence startups to revive and accelerate the air-launched sonobuoy program, ensuring that India’s underwater ‘ears’ are built at home, for the world.
Combined with low-power electronics and automated sleep modes, this approach could extend mission duration while reducing costs and logistics dependencies.
Recycled and Reusable Sonobuoys
Traditional sonobuoys are single-use devices, discarded after their batteries deplete. Recovering them is difficult and expensive, but research is underway to develop reusable and biodegradable models.
The goal is to reduce environmental impact, cut operational costs, and improve sustainability by using eco-friendly materials and modular recovery systems.
Modular Designs for Versatility
Modular sonobuoy designs allow for interchangeable components that can be customised for specific missions — from passive detection to multi-static networking.
This modularity ensures compatibility with multiple airborne platforms, simplifies maintenance and upgrades, and reduces overall costs. A single buoy equipped with both active and passive sensors represents the next logical step toward functional modularity and operational efficiency.
ASVs Supporting Deployed Sonobuoys
Autonomous Surface Vessels (ASVs) or Unmanned Surface Vehicles (USVs) are emerging as key partners for deployed sonobuoys. Their dual role includes sonobuoy management and data relay to aircraft or ships.
With extended energy endurance, USVs can maintain line-of-sight communication with distant sonobuoys, collect data, and transmit it to command centres, ensuring persistent underwater surveillance even when aircraft are not present.
The Way Ahead
In today’s unpredictable geopolitical climate, indigenous sonobuoy development is not just a technological goal — it’s a strategic necessity. India’s Ministry of Defence and the Indian Navy have already listed sonobuoys among 29 priority technologies for indigenisation.
It is time for the Indian Navy, DRDO, and domestic defence startups to revive and accelerate the air-launched sonobuoy program, ensuring that India’s underwater “ears” are built at home, for the world.
–The writer, an Aerospace Engineer, has served in the Indian Navy for 25 years. He is the founder and CEO of Defence Research and Studies [DRaS], a Fellow of the Institution of Engineers, and a Defence Research and Development Organisation – Technology Development Fund Expert. The views expressed are of the writer and do not necessarily reflect the views of Raksha Anirveda
