DRDO AIP Plug: Late, But a Leap for Project-76 Indigenous Submarine Design

AIP Energy Module & Submarine Plug Diagram by Gemini

DRDO is reportedly poised to deliver its indigenously developed Air Independent Propulsion (AIP) plug in time for integration with INS Khanderi during its scheduled refit in 2026–27.

INS Khanderi is the second Kalvari-class (Project-75, Scorpene) submarine inducted into the Indian Navy (IN). It was commissioned on September 28, 2019.

The Indian Navy inducted six Kalvari-class Scorpene submarines under Project-75 between 2017 and 2024. Originally, it was planned to integrate DRDO-developed AIP plugs—designed to facilitate extended submerged endurance—into all Kalvari-class boats. However, the DRDO plug was not ready in time for installation on the first boat, INS Kalvari.

AIP Development Landmarks and Timeline

In June 2023, DRDO signed a contract with L&T to provide two AIP system modules for Kalvari-class submarines.

Under the contract, the Naval Materials Research Laboratory (NMRL), a DRDO laboratory, transferred AIP technology to L&T. The AIP modules are manufactured, integrated, and undergo factory acceptance trials at L&T’s AM Naik Heavy Engineering Complex in Surat.

The AIP modules, also called Energy Modules (EMs), are integrated into the AIP plug, which is then retrofitted into the submarine during refit. The refit will also include equipping the boat to launch DRDO-developed heavyweight torpedoes.

In December 2025, DRDO was expected to deliver the EM for integration with the plug that will be inserted into INS Khanderi during its refit.

“The system has undergone extensive shore-based trials and has met the required benchmarks. Integration work on the second submarine is expected to be completed before December 2026,” Times Now reported, quoting sources.

The submarine will need to undergo extensive trials following installation of the AIP plug, since the dimensions and buoyancy characteristics of the boat will change.

Sea trials are reportedly expected to commence between July and August 2027, with the full refit process expected to conclude by early 2028, the sources added.

Characteristics of the DRDO-Developed AIP

The DRDO-developed AIP uses phosphoric acid fuel cell (PAFC) technology.

A fuel cell converts chemical energy from a fuel into electricity through a chemical reaction between positively charged hydrogen ions and oxygen (or another oxidizing agent).

1. Several fuel cell types exist, including:
2. Alkaline Fuel Cell (AFC)
3. Proton Exchange Membrane Fuel Cell (PEMFC)
4. Direct Methanol Fuel Cell (DMFC)
5. Molten Carbonate Fuel Cell (MCFC)
6. Phosphoric Acid Fuel Cell (PAFC)
7. Solid Oxide Fuel Cell (SOFC)

A PAFC uses phosphoric acid (H₃PO₄) as the electrolyte. Hydrogen gas (H₂) is used as the fuel at the anode, while oxygen (O₂) from air is supplied at the cathode.

PAFC fuel cells offer several advantages over other fuel cell types. They provide greater fuel flexibility and are more tolerant of fuel impurities. They can operate using reformed hydrocarbon fuels such as methanol or even biogas.

PAFC operating temperatures (150–200°C) are relatively high. As a result, they generate steam as a byproduct in addition to electrical power for propulsion. The steam can be utilized for other onboard heating requirements, raising overall operating efficiency to as high as 70%.

INS Khanderi

DRDO AIP Critical for Project-76 Submarines

Successful integration of the DRDO AIP plug will not only augment the capabilities of Project-75 submarines but will also facilitate finalization of the design of Project-76 submarines.

Under Project-76, India has embarked on an ambitious design, development, and manufacturing program to deliver 12 next-generation diesel-electric attack submarines (SSKs) to the Indian Navy.

Project-76 is envisaged as the logical successor to the foreign-designed Project-75 (French Scorpène) and the upcoming Project-75I (Most likely German Type-214) programs.

Project-76 was initiated in late 2023 when the Indian Navy’s Warship Design Bureau (WDB) received formal authorization to begin the preliminary design phase.

In early 2024, the MoD allocated initial funding for the indigenous development of two pivotal enabling technologies for modern submarines: AIP systems and advanced lithium-ion batteries. As noted earlier, AIP offers increased submerged endurance, while lithium-ion batteries provide higher discharge rates and faster charging compared with traditional lead-acid batteries.

Project-76 aims for an unprecedented 90–95% indigenous content, including the Combat Management System (CMS), sonar suites, and periscopes.

Development Timeline

L&T is confirmed to be part of the design process along with the Navy’s Directorate of Naval Design (Submarine Design Group) (DND-SDG).

L&T’s credentials in submarine construction are impressive and extend beyond the development of the AIP plug for Project-75 submarines. The company previously carried out detailed engineering and hull construction for the Arihant-class SSBNs. It also designed and developed the SOV-400 Midget Submarine, a 400-tonne special operations vessel for commandos.

Additionally, L&T designed and built the Submarine Escape Training Tower (SETT) facility in Visakhapatnam, which is used to train naval crews in emergency escape procedures.

P-76 Progress

In September 2025, a senior L&T official reportedly stated that the design phase of the submarine could be completed by 2026–27.

As of March 2026, the project has moved into the detailed design phase. The Indian Navy is currently finalizing the Staff Requirements to ensure the P-76 can act as a bridge between conventional SSKs and nuclear-powered attack submarines (SSNs) being built under Project-77.

Initially, six submarines are proposed to be built. The first submarine could be delivered in six to seven years, with all six delivered within ten years.

As mentioned earlier, follow-on orders are likely to meet the Indian Navy’s expanding requirements.

P-76 Specifications

The P-76 submarine is envisioned as a 3,000-tonne class vessel, roughly 50% larger than the current Kalvari class.

It will feature a fully indigenous AIP system and incorporate advanced lithium-ion batteries, both designed and developed by DRDO in collaboration with L&T.

The submarine will be armed with indigenously developed torpedoes as well as torpedo-tube-launched anti-ship and land-attack cruise missiles.

 Copyright © Vijainder K Thakur. First published on Thumkar.

IAF Signals Hypersonic Ambitions With IISc-Led Propulsion Challenge

A Gemini rendition of the launch of a S-200 with a DMRJ powered curise missile

The Indian Air Force on January 29, 2026 signed a Memorandum of Agreement (MoA)  with the Foundation for Science Innovation and Development (FSID), IISc Bengaluru to indigenously develop an advanced high-speed air-breathing propulsion system.

Announcing the MoA, the IAF's official X handle stated that the MoA "underscores IAF’s commitment towards Atmanirbharta by development of high-speed flight systems with dual-use capabilities."

Copies of documents and diagrams posted on social media and associated with the MoA indicate that the proposed “advanced high-speed air-breathing propulsion system” is a dual-mode ramjet/scramjet engine (DMRJ), intended for use in propelling missiles or combat aircraft.

DRDO has already developed ramjet and scramjet engines for missiles. The former operate efficiently at high supersonic speeds and the latter operate efficiently through hypersonic speeds. 

DMRJ Engines Explained

In a ramjet engine the air entering the engine is slowed to subsonic speed and consequently compressed before combustion. In a scramjet engine, the air is similarly slowed down and compressed but remains supersonic throughout the combustor. 

Ramjet engines operate efficiently roughly from Mach 3 to Mach 6. Scramjet engines are needed for speeds beyond Mach 6–7

DMRJ, which combines ramjet and scramjet propulsion, can operate efficiently across a very wide supersonic to hypersonic speed envelope by switching how combustion occurs inside the engine.

DMRJ Development Status

The DMRJ concept has been tested but never operationalised.

Russia reportedly tested a hydrogen-fueled dual-mode scramjet  developed by the Central Institute of Aviation Motors (CIAM) in the 1990s under (Kholod Project). 

It modified a 5V28 missile from the S-200 long-range air defence system, replacing the warhead and guidance system with a DMRJ and its liquid hydrogen fuel tank.

To test a DMRJ, it first has to be accelerated to high supersonic speeds that can facilitate ramjet light-up. The S-200 is a heavy missile with a launch weight exceeding 7,000 kg and substantial payload capacity. The S-200’s solid boosters and liquid-fueled sustainer were well suited to accelerating the payload to hypersonic velocities. This modified S-200 served as a cost-effective, readily available booster, leveraging existing infrastructure.

Boosted to high speeds by the missile’s liquid rocket motor, the DMRJ successfully transitioned from ramjet propulsion to scramjet propulsion, achieving speeds over Mach 6.4, with scramjet mode sustained for 77 seconds across seven flight tests (1991–1998).

Russia used the data gathered from these tests to develop the 3M22 Zircon, which can achieve speeds near Mach 8. However, the Zircon uses a scramjet engine not a DMRJ. It is boosted to hypersonic speed directly by its solid-propellant rocket booster. 

Similarly, DRDO’s Hypersonic Technology Demonstrator Vehicle (HSTDV) and its follow-up system under development, the Extended Trajectory–Long Distance Hypersonic Cruise Missile (ET-LDHCM), both use scramjet propulsion, not DMRJ.

DMRJ Limitation

A notable limitation of a DMRJ is its inability to operate from zero airspeed. It needs to be accelerated to a high airspeed that can generate air compression due to airflow path constriction. To overcome this limitation, a dual-mode ramjet (DMRJ) can be paired with a rocket booster when used in a hypersonic cruise missile. 

For use in a combat aircraft, the DMRJ is paired with a turbine engine in what is called a Turbine-Based Combined Cycle (TBCC) architecture.

In a TBCC-powered combat aircraft, at speeds below ~Mach 2.5 to 5, a turbofan or turbojet provides thrust. The turbine is then shut down and bypassed, and the DMRJ takes over propulsion.

Combining a turbine with a DMRJ allows a combat aircraft to take off conventionally using a turbine engine and then accelerate all the way to hypersonic speeds.

Using TBCC propulsion, a combat aircraft can take off and loiter at subsonic cruise. When desired, it can accelerate to supersonic speeds using its turbine engine and then switch to DMRJ propulsion for sustained hypersonic cruise. Such a flight profile is impossible with a pure DMRJ + rocket booster combination.

TBCC Challenges

Ramjets, scramjets, and DMRJs are conceptually and mechanically relatively simple to build, as they involve no moving parts. However, the materials and techniques required to sustain supersonic and hypersonic combustion do pose significant challenges.

While a DMRJ can be combined with a turbine engine in a TBCC configuration, the engineering challenges are extremely complex, and the concept remains experimental.

The air flowing into a turbine engine has to be subsonic and at relatively low temperatures, whereas the airflow in a DMRJ has to be supersonic and at very high temperatures.

As such, the two engines share the inlet and nozzle, but not the combustor.

Smoothly switching from turbine to ramjet and then to scramjet operation is a particularly major challenge. Any pressure mismatch can cause the engine to fail to start or experience flameout.

Conclusion

As already noted, the engineering challenges of building a reliable ramjet that can transition to scramjet mode within the form factor of a compact missile fare immense.

While standalone scramjet and ramjet missiles exist or are being developed, true DMRJ designs remain in research and flight test demonstration programs rather than fielded systems

As already noted, there are no operational missiles powered by DMRJ propulsion, let alone the even more complex TBCC architecture.

Viewed in this light, the IAF’s MoA with IISc is clearly aimed at funding long-term research. This investment is unlikely to yield operational benefits for the IAF for at least a decade.

IISc has actively participated in the HSTDV programme, which successfully met its stated objectives. It therefore possesses the experience and technical depth required to undertake the development of DMRJ propulsion, and eventually progress to TBCC systems.

Supporting long-term technology development is, without doubt, a sound approach for the IAF.

However, there also appears to be a subtle but important message in the IAF’s tie-up with IISc:

While the IAF is willing to invest in future technologies, its immediate operational requirements cannot wait. These must be met through fast-paced procurement, preferably from domestic OEMs, but where necessary through foreign partnerships that guarantee continuity of support and supply.

Copyright © Vijainder K Thakur. First published on Thumkar.

Is DRDO Overprojecting Project Kusha to Undercut Local S-400 Manufacturing?

Conceptual view of a deployed Kusha system

The Indian mainstream media, ever inclined to hype and sensationalise defence-related news, is at it again. This time, the focus is on Project Kusha.

Media professionals, lacking deep enough insight into weapon systems, are hyping DRDO claims about the capabilities of Project Kusha and its projected development timelines, instead of critically questioning the claims.

Let us first understand what Project Kusha is and then see for ourselves whether DRDO claims are realistic.

Project Kusha: Conceptual Overview

Based on statements by DRDO officials, Project Kusha is an Integrated Air Defence System (IADS) that is conceptually similar to the Russian S-300, S-350, S-400 and S-500 systems.

An IADS provides layered (short, medium- and long-range) defence against a wide spectrum of aerial threats, ranging from medium-sized drones and helicopters to cruise missiles, fighters, aerial force multipliers such as tankers, AWACS and ISR platforms, as well as short- and medium-range ballistic missiles.

Russia is the only country in the world that has so far developed full-spectrum IADS. The Indian Air Force (IAF) is in the process of procuring the S-400 system from Russia. The three systems already acquired proved very effective during Operation Sindoor. The S-400’s track record during the ongoing war in Ukraine has also been impressive.

Understandably, the Indian defence media was elated when DRDO announced in 2025 that it would be developing an IADS. The media went overboard, projecting Kusha not just as an S-400 analogue but as an S-500 analogue. The former claim was a stretch; the latter, a joke. 

A major difference between the S-400 and the S-500 is that the latter is capable of engaging hypersonic aerial threats. India will first need to operationally deploy a hypersonic manoeuvring missile before it can develop an interceptor for such a missile. At this point in time, we are well short of that capability.

Emboldened by the puerility of media questioning, DRDO officials have put forward extraordinarily ambitious timelines for Project Kusha—timelines that bear little resemblance to past performance.

Kusha capabilities

As noted earlier, Kusha is an integrated air defence system, broadly comparable to the S-400, and is designed to employ a layered mix of short-, medium- and long-range interceptor missiles.

The single-stage short-range Kusha interceptor, designated Mk-1 and having a range of approximately 50–60 km, forms the core of all three missile variants.

The medium-range (Kusha Mk-2) and long-range (Kusha Mk-3) variants build upon this core interceptor by adding a booster stage, making them two-stage interceptors. The two variants differ primarily in the diameter of the booster stage.

Development Progress

At this point in time, the Kusha IADS exists only as a concept, and the Kusha Mk-1 most likely as a designed and wind-tunnel-tested model.

According to an HT report, the first development trials of Kusha Mk-1 are expected to take place in September this year. DRDO expects the Kusha Mk-1 to be inducted as a standalone short-range missile system by 2028.

Development trials of both Kusha Mk-2 and Kusha Mk-3 are projected to start in 2027.

In other words, the three missiles will be developed on parallel tracks after the Mk-1 interceptor has demonstrated the efficacy of its design.

Based on the HT report, DRDO appears to be projecting that by 2030, Kusha will be ready as an IADS with three different interceptor missiles covering ranges from 50 to 400 km.

This projection is certainly not backed by DRDO’s past record in operationalising indigenously developed air defence missile systems, nor does it have a global precedent. The claim is so divergent from reality that it can only be explained as an attempt to scuttle the local manufacture of S-400 system components.

DRDO has done well with recent missile projects such as Akash Prime and Akash NG, but nowhere near well enough to enable it to develop the Kusha system within five years. 

Akash Prime

Akash Prime is an incremental upgrade of the Akash missile in which an active seeker replaces the passive seeker of the Akash. Other improvements include a mobile launcher and more reliable performance under low temperature environments at higher altitudes. The missile reportedly has a longer engagement range of 40-km

The maiden test of the Akash Prime missile was done on September 27, 2021. During the test the missile successfully intercepted and destroyed an unmanned aerial target. Five years since its maiden test,  the missile has yet to be operationally inducted.

Akash NG

Akash NG was first mooted in 2010. The DRDO had then projected a development time of just 18 months. Notably, the claim notwithstanding, the DRDO was yet to develop a RF seeker for any missile at that point of time. 

The project was sanctioned in September 2016 after DRDO acquired RF seeker technology with help from Russia. 

The missile was first tested on January 25, 2021, using an electronic target to validate its ability to engage a hard manoeuvring target.

The missile was tested for the second time on July 21, 2021, once again without its active seeker, against an electronic target. Subsequent phased testing progressively demonstrated all design capabilities of the missile.

Following flight testing on December 24, 2024 DRDO announced that the missile system had “successfully intercepted aerial targets at different ranges and altitudes, including near-boundary low-altitude and long-range, high-altitude scenarios.”

The test marked the successful completion of User Evaluation Trials of the missile, meeting all PSQR requirements. However, till today, the missile is yet to be inducted into operational service. 

In an earlier blog post, I had praised DRDO's development of a new clean sheet, dual pulse motor missile with an active seeker and a very capable radar in just around 10 years. 

Conclusion

The IAF needs a proven IADS now, not in the future. This was shockingly evident during Operation Sindoor. One only needs to close one’s eyes and relive the operation hour by hour, day by day, to realise how badly we could have been mauled had the IAF not operationally deployed its S-400 regiments.

DRDO’s projections that it will be able to develop three different variants of Kusha interceptor missiles within the next four to five years are overly optimistic at best.

Possibly, this is a disingenuous attempt to prevent the IAF from taking up local manufacture of the S-400 system.

From DRDO’s point of view, local manufacture of the S-400 or S-500 system would dramatically reduce the market size for its Kusha system, as and when it is fully developed.

However, DRDO needs to tread with caution. In the past, capability overprojections have resulted in a precipitous drop in IAF squadron strength. As a result of this decline, the IAF is now more heavily reliant on air defence than it has ever been in the past.

While there can be no doubt that the IAF should look at domestic options despite limited capability shortfalls, there can also be no doubt that such compromises should not enfeeble the IAF to an extent where it loses its deterrent capability. DRDO must keep the national interest in mind to the same extent that it expects the IAF to do so.

Overstating its capabilities and projecting unrealistic timelines to secure the only market segment it is capable of competing in is not the right approach.

Copyright © Vijainder K Thakur. First published on Thumkar.

LR-AShM: India’s Hypersonic Answer to Carrier Strike Groups

Photo credit: AIR

The DRDO is set to display its most lethal non-strategic missile to date—an aircraft-carrier killer—during this year’s Republic Day parade. The Long Range Anti-Shipping Missile (LR-AShM) is a hypersonic missile being developed to arm Indian Navy (IN) coastal batteries. It is designed to ensure that no carrier group—US or Chinese—can approach within 1,500 km of the Indian coastline in an attempt to exert military pressure on the nation. Currently, IN coastal batteries are armed with BrahMos missiles.

According to the MoD press release, the missile follows a quasi-ballistic trajectory. It achieves hypersonic speeds starting at Mach 10, maintaining an average speed of around Mach 5.0 through a “multiple-skip” manoeuvre.

A quasi-ballistic trajectory differs from a ballistic trajectory. In the latter, the missile follows a largely predictable flight path. In contrast, a quasi-ballistic trajectory is inherently unpredictable. Equally important, such a trajectory allows the missile to fly at relatively low altitudes, evading detection by ground- or ship-based radars during much of its flight. The missile’s extreme speed and manoeuvrability further complicate interception.

The LR-AShM has been indigenously developed by laboratories of the Dr APJ Abdul Kalam Missile Complex, Hyderabad, along with several other DRDO laboratories and industry partners.

Terminal Guidance

An anti-shipping missile carrying a conventional warhead requires extremely precise terminal guidance, given that an aircraft carrier is a fast-moving and manoeuvring target.

Typically, a long-range missile intended to strike a moving target employs a dual-mode seeker combining Active Radar Homing (ARH) and Imaging Infrared (IIR) guidance. ARH enables target acquisition and tracking in all weather and lighting conditions, while IIR facilitates target discrimination in clear weather, allowing the missile to distinguish the carrier from other warships in the strike group.

Without specifying the nature of the terminal guidance, the MoD press release states:

“Indigenously developed sensors are provided for engaging moving targets in the terminal phase.”

DRDO developed and refined its ARH capability through the BrahMos programme, particularly the land-attack variant. Similarly, it honed its IIR homing capability while developing advanced variants of its Anti-Tank Guided Missiles (ATGMs).

Maiden Test

The Defence Research and Development Organisation (DRDO) conducted a successful flight trial of India’s first long-range hypersonic missile from Dr APJ Abdul Kalam Island, off the coast of Odisha, on November 16, 2024.

At the time of its maiden test, the MoD release referred to the LR-AShM simply as the Long Range Hypersonic Missile (LR-HM).

Missile Launch Video Analysis

DRDO released a video of the maiden test. The following observations are based on that footage.

As the missile emerged from its container following a cold launch, it appeared to employ its attitude-control thrusters twice before first-stage solid-rocket-motor ignition.

The missile transitioned from a vertical to a horizontal trajectory in roughly six seconds, beginning about eight seconds after liftoff. This early transition suggests the missile is designed to fly within the atmosphere for the entire duration of its flight.

The missile’s physical configuration indicates a two-stage solid-propellant design.

The first stage functions as a booster. The second stage is the hypersonic sustainer, featuring cruciform, short-span, long-chord aerodynamic surfaces along the mid-body and four short triangular fins at the aft section. The mid-body surfaces likely provide manoeuvrability and flight control, while the aft fins contribute to stability.

According to the MoD press release, the missile

“features a two-stage solid propulsion system. The first stage separates after burnout, while the second stage boosts the vehicle to hypersonic speeds before transitioning into an unpowered glide to the target.”

At hypersonic velocities, the cruciform configuration can reduce drag compared to planar wing designs.

Future Development

As stated in the MoD press release, the missile will initially be deployed with coastal batteries. A logical progression would be upgrades enabling deployment aboard IN warships and, eventually, submarines. Such deployment would push adversary carrier groups well beyond 1,500 km from India’s coastline.

The demonstrated cold-launch capability from a container strongly suggests eventual deployment on ships and potentially on future submarines.

YJ-20

China fields several ballistic missiles with hypersonic warheads capable of anti-shipping strikes, including the DF-21D (1,500 km, Mach 10), DF-26 (4,000 km, Mach 10+), DF-17 (1,800–2,500 km, Mach 5–10), and DF-27 (5,000–8,000 km, Mach 5+).

Because ballistic missiles follow relatively predictable trajectories, they can be intercepted by ship-borne air-defence systems within a carrier group.

More recently, China has fielded hypersonic quasi-ballistic anti-ship missiles, notably the YJ-20 and YJ-21, capable of launch from air, surface, and undersea platforms.

Chinese state media released footage showing a YJ-20 launch from the PLAN Type 055 destroyer Wuxi on December 28, 2025.

The YJ-20 cruises at speeds exceeding Mach 6, has a reported range of 1,500 km, and reaches terminal speeds of Mach 10. It is compact enough for air launch from the H-6K bomber and vertical launch from Type 052D and Type 055 destroyers. It may also be deployable from both nuclear- and diesel-electric-powered submarines.

Russia’s Zircon is another hypersonic anti-shipping missile deployable from ships and submarines; however, it is a scramjet-powered cruise missile, not a boost-glide system.

YJ-20 and LR-AShM Comparison

There are notable similarities between the LR-AShM and the YJ-20.

Both are hypersonic boost-glide systems designed for anti-ship roles. However, the YJ-20 employs biconic aerodynamics, likely enhancing manoeuvrability.

Both have publicly stated ranges of around 1,500 km, though actual operational ranges are likely higher.

Both achieve Mach 5+ speeds with high terminal velocities, attack targets in a near-vertical dive, and present significant interception challenges.

Conclusion

Despite its prominent display during the Republic Day parade, the LR-AShM remains in an early stage of development. It may take several years before DRDO can demonstrate the accuracy required to reliably cripple a manoeuvring aircraft carrier using a conventional warhead.

Given its intended deployment with coastal batteries, fitting a nuclear warhead is unlikely, even though the MoD press release notes that the missile “is designed to carry various payloads.”

Copyright © Vijainder K Thakur. First published on Thumkar.

Why India's BM-04 Boost-Glide Missile Raises the Cost for Adversaries - An Analysis

 

BM-04 in Flight by @Grok

The DRDO has reportedly received a go-ahead from the MoD to

develop the BM-04 Short-Range Ballistic Missile (SRBM).

A full-scale mock-up of the missile was unveiled at the

Vigyan Vaibhav 2025 defence exhibition in Hyderabad (February 28

to March 2, 2025).

The design of the re-entry vehicle armed with the missile warhead suggests that it is a boost-glide hypersonic weapon. However, the placard placed next to the missile mock-up, displaying its specifications, did not specify its speed.

Specifications

The canister-launched missile is 10.2 metres long, 1.2 metres in diameter, and weighs 11,500 kg. It features a two-stage solid-fuel propulsion system and carries a 500 kg conventional warhead.

It is deployed using a six-axle indigenous Transport Erector Launcher (TEL).

#DRDO's new BM-04 missile with MaRV warhead🇮🇳 pic.twitter.com/pQMOpV3qDn

— News IADN (@NewsIADN) February 28, 2025

Missile Capabilities

The missile features a precision-strike-capable 500 kg conventional warhead and has a range of 400–1,500 km. It uses satellite-aided inertial navigation, incorporating GPS and the Indian Regional Navigation Satellite System (IRNSS). A CEP of less than 30 m is claimed.

The BM-04 uses a two-stage solid-fuel propulsion system and navigates using a combination of an Inertial Navigation System (INS) and a Satellite Navigation System (SATNAV). The missile does not have terminal homing capability and has a CEP of 30 metres.

Physical Characteristics

The missile features a conical-shaped re-entry vehicle, likely a boost-glide vehicle with a Common Hypersonic Glide Body (C-HGB). The inclusion of a C-HGB, along with features such as fixed wings and control fins on the re-entry vehicle, suggests hypersonic speeds with manoeuvrability during both exo-atmospheric and endo-atmospheric phases, enabling evasion of radar and missile defence systems.

Analysis

The BM-04 shares visual and technological similarities with the Agni-I and Agni-Prime (Agni-P) missiles but is tailored for conventional roles, with a smaller payload and hypersonic capabilities.

The missile’s range allows it to be stored deep within Indian territory, complicating adversaries’ ability to target launch sites. Its canisterised design also supports a “shoot-and-scoot” capability for rapid, pre-emptive strikes.

The hypersonic enabling technologies for the BM-04 were likely developed under the Long-Range Hypersonic Missile (LRHM) programme, which was maiden-tested in November 2024.

The @DRDO_India has successfully conducted a flight trial of its long range hypersonic missile on 16th Nov 2024 from Dr APJ Abdul Kalam Island, off-the-coast of Odisha.

Raksha Mantri Shri @rajnathsingh has congratulated DRDO, Armed Forces and the Industry for successful flight… pic.twitter.com/wq7yM2YS9f

— रक्षा मंत्री कार्यालय/ RMO India (@DefenceMinIndia) November 17, 2024

Maneuvering hypersonic missiles have demonstrated the ability to penetrate the most advanced air defence systems in the world. The BM-04’s precision-strike capability and ability to operate in contested airspace would allow it to rapidly erode an adversary’s warfighting capability while remaining well below the nuclear escalation threshold.

The BM-04 missile and the Long-Range Hypersonic Missile (LRHM) tested by DRDO in November 2024 are likely not the same missile. However, they share technological similarities and are part of DRDO’s broader hypersonic missile development programme.

DRDO may have used the LRHM as a hypersonic boost-glide technology development and demonstration testbed. The “Long-Range” designation of the LRHM, along with the claimed range of more than 1,500 km in the PIB press release announcing the maiden test, suggests that the LRHM may eventually be developed into a long-range hypersonic missile.

Copyright © Vijainder K Thakur. First published on Thumkar.

AMCA Timeline Slips Again: DRDO’s Projections Face Another Reality Check

 

A scale model of the AMCA on display at AI 2019

Speaking on the sidelines of an event marking 25 years of the LCA Tejas flight programme, DRDO Chief Samir V. Kamat reportedly said that the AMCA is likely to be rolled out by the end of 2028. The aircraft’s first flight may take place in early 2029.

Let us look back at HAL/DRDO’s AMCA rollout projections since 2019.

In January 2021, the Chairman and Managing Director of Hindustan Aeronautics Ltd, R. Madhavan, said, “The prototype of the aircraft is likely to be ready by 2026, and its production could start by 2030.”

In September 2021, Girish S. Deodhare, Programme Director (Combat Aircraft) and Director, ADA, upped the ante by projecting a first flight in 2025.

He said, “We are moving to a critical design review by the middle of next year, with the roll-out planned in 2024 and the first flight planned in 2025.”

Dr A. K. Ghosh, Project Director of AMCA, stated during DefExpo 2022, “Once the project sanction is received, the first prototype can be rolled out in three years, and the first flight can take place one to one-and-a-half years after that.”

Considering that the AMCA project received its go-ahead in 2024, the timeline projected by Dr Ghosh would translate to a first flight by the end of 2028.

Now, the first flight is being projected in 2029.

The IAF, which has had a long association with DRDO and HAL, has remained sceptical.

When DRDO first projected the AMCA development timeline to the Indian Air Force (IAF) in 2019, it assured operational induction by 2035.

The IAF’s top leadership, despite its enthusiasm and wholehearted support for a home-grown stealth fighter, considered the timeline ambitious. In July 2020, the IAF euphemistically described the timeline as “very tight.”

However, senior DRDO and HAL officials ignored the IAF’s reservations.

In November 2022, the Chief of the Air Staff (CAS), Air Chief Marshal V. R. Chaudhari, advised “prudence.” He recommended foreign tie-ups as a fallback for developing “alternative systems and sensors” in case indigenous development slipped off the timeline.

The IAF has projected to the MoD a requirement for 2-3 squadrons of an interim stealth fighter to plug the operational gap due to the absence of stealth fighters in IAF inventory. 

It's time for the government to act, because the writing is on the wall 

Why SPICE-1000 Will Augment, Not Replace, DRDO’s Gaurav Glide Bomb

SPICE-1000 Glide Bomb Kit at Aero India 2015

The DAC recently approved the procurement of SPICE-1000 long-range guidance kits for the Indian Air Force (IAF). The PIB press release announcing the DAC approval stated, “SPICE-1000 will enhance the long-range precision strike capability of the Indian Air Force.”

The SPICE-1000 is a glide-cum-navigation kit that can be fitted to a dumb 1,000 lb general-purpose penetrator bomb to convert it into a long-range PGM, much like the UMPK kits that Russian forces are using extensively in Ukraine.

Notably, DRDO is developing and has tested its own glide bomb kits. This raises the question: why does the IAF need to procure SPICE-1000 kits from Israel, particularly when the imported kits are woefully expensive?

SPICE-1000 Glide Kits

The SPICE (Smart, Precise Impact, Cost-Effective) 1000 kits are equipped with a mid-body fold-out wing assembly and a rear cruciform tail control fin set for gliding; INS and SATNAV for mid-course navigation; and electro-optical/infrared (EO/IR) guidance for target acquisition and terminal homing.

The IAF has earlier acquired SPICE-2000 bomb kits and SPICE-250 bombs and used them operationally to strike terrorist camps in Balakot.

All three SPICE variants are equipped with an Automatic Target Acquisition (ATA) capability—an autonomous electro-optic scene-matching technology designed to overcome GPS jamming, navigation errors, and target location inaccuracies when engaging fixed targets. On approach to the target, the scene-matching algorithm compares the electro-optical image received in real time via the weapon seeker with mission reference data stored in the weapon’s onboard computer.

The EO/GPS-guided seeker in the SPICE kit or bomb has a CEP of less than 3 m in day/night and adverse weather conditions. The seeker is two-way data-linked to the launch or control aircraft (which may be different platforms).

The kit gives the 1,000 lb penetrator bomb a range of up to 125 km from the release point.

SPICE Kit Operational Capability

Either on the ground or in the air, the bomb can be programmed with up to 100 different mission profiles, including target coordinates, desired terminal glide and azimuth angles, topographical data, and target imagery.

Before release, the pilot selects the mission profile. Depending on the release altitude and the selected profile, the SPICE-1000 bomb may be released up to 125 km away from the target.

Following release, the weapon autonomously glides toward the target.

As it approaches the target, the seeker uses scene-matching algorithms to compare the EO sensor image with the stored target image and identify the target.

Once the target is identified, the weapon autonomously homes onto it, adjusting its flight path to achieve the desired impact angle and azimuth.

If the target is obscured, the bomb reverts to GPS guidance.

Via the datalink, the pilot or WSO can view the seeker image on the cockpit TV/IIR display and manually guide the bomb to the target using a joystick.

If the target is obscured, precluding both scene matching and manual joystick guidance, and GPS signals in the target area are jammed, the bomb may deviate from its intended flight path.

DRDO Glide Bombs

In 2013, DRDO announced a project to develop glide bomb kits. Since then, DRDO has indigenously developed glide bomb warheads and glide kits for 250 kg, 500 kg, and 1,000 kg class bombs.

DRDO’s Gaurav Long Range Glide Bomb (LRGB), designed and developed indigenously by the Research Centre Imarat (RCI), Hyderabad, is a navigation and glide kit for the DRDO-developed 1,000 kg High Speed Low Drag (HSLD) bomb.

The Gaurav LRGB uses a combination of INS and SATNAV for both mid-course and terminal navigation. Reportedly, it can be fitted with a Semi-Active Laser Homing (SALH) seeker, which would require the target to be laser-illuminated by a high-flying drone.

Adani Defence and Bharat Forge are Development-cum-Production Partners for the bomb.

DRDO successfully conducted release trials of Gaurav during April 8–10, 2025, from a Su-30MKI.

Earlier, on August 13, 2024, DRDO carried out a successful maiden flight test of the bomb from an IAF Su-30MKI off the Odisha coast.

Gaurav is reported to have a range of 30–150 km, depending on release altitude. For maximum range, it typically needs to be released from around 10 km altitude.

During trials, it has demonstrated a maximum range of 100 km.

With laser illumination of the target, Gaurav can achieve pinpoint accuracy. Without laser illumination, accuracy is reduced.

A Su-30MKI fighter can carry Gaurav-kitted bombs on multiple stations.

Gaurav Limitations

Compared to the SPICE-1000, Gaurav kits have certain operational limitations—specifically, the lack of an EO seeker, which constrains mission planning, and the reliance on target illumination.

Once released from its carrier aircraft, a Gaurav bomb glides directly toward its target. Without stored target-area imagery, it cannot select attack geometry or approach direction in the way the SPICE-1000 can.

Gaurav’s reliance on target illumination makes it significantly less versatile than the SPICE-1000. A MALE drone equipped with a laser designator must loiter over the target area to guide the weapon, exposing the platform to adversary air-defence systems. In addition, atmospheric obscurants such as cloud cover, dust, or smoke can degrade or even prevent effective laser illumination.

Conclusion

A SPICE-1000 kit typically costs around $480,000. As such, it is not suitable for extensive use. The IAF would not be able to employ these kits as liberally as Russian forces have used UMPK kits in Ukraine. However, SPICE-1000 is essential when near-pinpoint accuracy is required.

Gaurav can also achieve pinpoint accuracy, but only when laser target illumination is available, which may not always be the case.

The optimal solution for the IAF is to acquire SPICE-1000 kits in limited numbers and Gaurav-1000 kits in larger quantities.

Russian UMPK kits—which, like Gaurav, lack EO seekers and rely exclusively on INS and SATNAV for guidance—have demonstrated acceptable accuracy, successfully striking bridges and buildings.

The UMPK kits use 8- or 12-node SATNAV modules that are resilient to EW spoofing and can achieve accuracy comparable to military SATNAV signals.

Over time, DRDO is expected to upgrade the Gaurav-1000 kits with EO seekers and advanced mission-profiling capabilities.

Copyright © Vijainder K Thakur. First published on Thumkar.