With K-4 SLBM, India’s Nuclear Triad Finally Becomes Credible

Image by @Grok

Multiple reliable sources, including the ToI, report that the Indian Strategic Command test-launched a K-4 SLBM (Sea-Launched Ballistic Missile) from its SSBN INS Arighat on December 23, 2025.

There was no official word from the Indian Ministry of Defence (MoD) on the missile test reportedly conducted off the coast of Visakhapatnam from the 6,000-tonne INS Arighat, which is operated by the tri-service Strategic Forces Command.

Notably, in the past as well, there has been no official confirmation of SLBM tests by the MoD.

The ToI quotes a source as saying, “A comprehensive analysis will determine whether Tuesday’s test actually met all laid-down technical parameters and mission objectives or revealed some shortcomings. It usually takes several tests for ballistic missiles, especially those launched from submarines, to achieve full operational status.”

Earlier Test

Earlier, in November 2024, the Strategic Command had carried out a test launch of the 3,500-km-range missile from the then newly inducted nuclear submarine INS Arighat.

The missile was launched almost to its full range, marking the first K-4 launch from an operational submarine (previous tests used submersible platforms).

INS Arighat, the Strategic Command’s second SSBN, was commissioned in August 2024.

How SLBMs Differ from Land-Based Strategic Missiles

SLBMs differ from land-based strategic ballistic missiles in their configuration and construction. An underwater-launched missile has to deal with the pressure of a 10-m column of water above it. SLBMs are sturdier in build and consequently heavier. Compared to land-based strategic missiles of the Agni series, SLBMs carry a lot of dead weight.

The K-4 is the second operational SLBM deployed by the Strategic Forces. The first operational SLBM was the 750-km-range K-15 (aka BO-5).

K-4 Development

Some of the key components of the K-4 were designed and developed at the three facilities of the Pune-headquartered Armament and Combat Engineering (ACE) cluster of the DRDO.

The facilities are:

High Energy Material Research Laboratory (HEMRL), Pune

Research and Development Establishment (Engineers), aka R&DE (Engrs), Pune

Advanced Centre for Energetic Materials (ACEM), Nashik

The rocket motor systems of the missile have been designed, developed, and manufactured by HEMRL and ACEM. The launch system of the missile has been developed by R&DE (Engrs).

HEMRL has additionally developed propellants and motor systems for almost all DRDO missiles, including Prithvi, various versions of Agni, Akash, and Nag.

Some of these systems have been produced by ACEM, which is a facility that processes composite propellants for various DRDO programmes.

The Naval Systems Group of the DRDO has developed the launch system of the K-4 missile.

Specifications

The solid-fuelled K-4 is 10 to 12 m long and 1.3 m in diameter. It weighs between 17 and 20 tonnes and is capable of carrying a 2-tonne warhead.

The missile warhead is capable of manoeuvring to avoid adversary missile defences and yet strike with a 100-m CEP (Circular Error Probability).

Follow-up SLBMs

India’s first two SSBNs, INS Arihant and INS Arighat, carry either four 3,500-km-range K-4 missiles or twelve 750-km-range K-15 (aka BO-5) missiles.

A longer, 5,000-km-range, 12-m-long SLBM known as K-5 is under development for future use.

K-6 SLBM

DRDO is also reported to be developing a 6,000-km-range missile named K-6.

This three-stage solid-fuel K-6 is reportedly completely different from the K-4 and K-5.

Over 12 metres tall and over 2 metres in diameter, it will carry a three-tonne warhead. The 6,000-km range of the missile will allow its carrier SSBN to remain on deterrence patrol, operating from secured zones near the Indian coast.

A former head of India’s Strategic Forces Command alluded during an event in Washington that India’s sea-based deterrent would eventually “be secured in havens, waters we are pretty sure of, by virtue of the range of the missiles. We will be operating in a pool in our own maritime backyard.”

Recent reports claim that the missile is a hypersonic weapon with a multiple independently targeted re-entry vehicle (MIRV) warhead. Capable of a top speed of Mach 7.5, it can carry two to three nuclear or conventional warheads, allowing it to evade terminal missile defences.

The missile is 12 metres long, has a 2-metre diameter, and weighs around 20 tonnes. It is being claimed that initial tests of the missile from submerged pontoons are likely in the near future.

Follow-up SSBNs

India’s two operational SSBNs, INS Arihant and INS Arighat, will be followed by two Arihant-class Stretch submarines with 7,000-tonne displacement and 125-metre length. They are fitted with a 10-m-long, 1,000-tonne plug with room for an additional four missile tubes.

Whereas Arihant-class SSBNs carry four K-4 missiles or twelve K-15 missiles, or a mix of the two, Arihant-class Stretch SSBNs carry eight K-4 missiles or twenty-four K-15 missiles, or a mix of the two.

During the Navy Day press conference in Delhi on December 2, 2025, Indian Navy Chief Admiral Dinesh K. Tripathi reportedly said that INS Aridhaman, the third indigenous nuclear-powered ballistic missile submarine (SSBN), would be commissioned very soon.

The Arihant-class Stretch will be followed by a clean-sheet new-design SSBN with 13,300-tonne displacement, carrying twelve K-6 6,000-km-range ballistic missiles. The new design, referred to as the S-5-class submarine, will be powered by a 190-MW reactor designed by the Bhabha Atomic Research Centre.

Conclusion

Successful completion of user trials of the K-4 SLBM would be a landmark event. For the first time, it would make the undersea leg of India’s deterrence triad credible. The limited 750-km range of the K-15 missile, currently operational on INS Arihant and INS Arighat, lends little credence to India’s undersea-based deterrence capability.

Reports that India is on the verge of testing the K-6 SLBM with ICBM capability must be taken with the proverbial pinch of salt, considering that the DRDO has yet to conduct a full flight test of the K-5 SLBM.

Akash NG: A Clean-Sheet Next-Generation Air Defence Missile Delivered in Record Time

Screenshot from DRDO released video of the test.

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

The NG system had successfully completed User Evaluation Trials of the missile, meeting all PSQR requirements.

Earlier Tests

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

Follow-up tests were conducted in March 2021 and July 2021.

The missile was tested for the second time on July 21, 2021, once again without its active seeker, against an electronic target.

In a follow-up test on July 25, 2021, the missile, fitted with an active seeker, successfully intercepted a high-speed unmanned aerial target.

The test validated the functioning of the complete weapon system, consisting of the RF seeker, launcher, multi-function radar, and command, control & communication system.

Akash NG Overview

The Akash-NG project, which was sanctioned in September 2016, is a new-generation interceptor missile system. It is a clean-sheet design, not a derivative of the Akash missile.

The earlier Akash interceptor was based on the Soviet-era SA-6 (NATO codename Gainful) missile. It used a ramjet propulsion sustainer and a TVM (Track Via Missile) seeker. A TVM seeker combines SARH (semi-active radar homing) and command guidance. TVM homing is jam-proof, but its accuracy drops with target range.

In contrast, the Akash NG uses a dual-pulse rocket motor and an indigenously developed active seeker. The tracking ability of an active seeker does not degrade with target range. Also, the active seeker gives the missile endgame fire-and-forget capability. Dual-pulse motors provide good endgame manoeuvrability. The active seeker of the missile is being manufactured by Bharat Electronics Limited (BEL).

One drawback of an active seeker is that it is prone to jamming.

The Akash NG was developed for the Indian Air Force and Indian Army to facilitate interception of high-manoeuvring, low-RCS aerial threats. It was developed with excellent mobility and field storage in mind. It is mounted on a wheeled vehicle/trailer and uses six missile canisters for storage and launch.

The system is designed and developed by the DRDO and manufactured by Pune-based Electropneumatics and Hydraulics (India) Pvt Ltd (EHPL).

EOTS

The Akash NG system features an indigenously developed electro-optical tracking system (EOTS) for passively acquiring and tracking targets.

DRDO’s IRDE designed and developed the Stabilised Electro-Optical Sight (SEOS). Mounted on a mobile platform such as a tank, fast-moving boat, or a fighter aircraft, the two-axis stabilised panoramic sight can passively acquire targets up to 40 km away.

The SEOS comprises a laser range finder, CCD camera, thermal imager, and automatic video tracker.

Hyderabad-based VEM Tech has been designated to manufacture the systems for supply to the Defence Ministry.

Akash-NG Capabilities

The missile, which has an intercept range of 30 km, is capable of engaging multiple targets.

According to EHPL, the system operates to an elevation of 20–70° and an azimuth of 360°, and it is designed for reloading two canister missile stacks within 10 minutes.

The reaction time of the system is 10 seconds from target acquisition by the command-and-control unit when a single missile is launched.

For three missiles, the system’s firing rate is 20 seconds. It takes the missile system 20 minutes to transition from transportation mode to ready-to-fire state and vice versa.

The system consists of six canister missiles mounted on a mobile platform for transportation.

Russia Unveils Expanded Su-57 Production and Export Strategy Backed by New Product 177 Alternative Engine

Product 177 engine fitted on Su-57 (via Rostec)

Russia has for the first time flown a Su-57 fighter with the new Product 177 engine, according to Rostec's press service.

The Product 177 engine worked normally and reliably during the first flight, reported the General Designer–Director of the A. Lyulka Design Bureau, a branch of PJSC UEC-UMPO of the United Engine Corporation, Evgeny Marchukov.

“The first test flight marked the beginning of joint work with colleagues from the UAC for flight tests of the Su-57 with the latest engine. During the flight, the new engine worked normally and showed reliable operation as part of the Su-57 aircraft,” the Rostec press service quoted Marchukov as saying.

According to Marchukov, the Product 177 engine has significantly improved technical characteristics compared to the power plants of the previous generation. The engine made it possible to incorporate the latest technologies, materials, and innovative design solutions.

The Product 177 has been created by UEC for use in fifth-generation aviation systems. It features a maximum thrust of 16,000 kilograms-force (kgf). Additionally, it has lower fuel consumption in all flight modes and an increased service life.

What Happened to the AL-51F Engine?

Current production Su-57 fighters are widely reported to be powered by AL-51F engines.

The AL-51F1, also known as Izdeliye 30 (Product 30), is a two-shaft low-bypass afterburning turbofan engine with a dry thrust of 108 kN and a maximum afterburner thrust of 167 kN. The engine was developed by UEC-Saturn for second-stage production Su-57 fighters. First-stage production aircraft feature Product 117, also known as the AL-41F1 engine.

Product 177 engine fitted Su-57 (via Rostec)

AL-51F First Flight

On December 5, 2017, the T-50 flew for the first time powered by Stage 2 Product 30 engines. The flight was performed by Hero of the Russian Federation and chief pilot of PJSC “Sukhoi Company” (as part of the UAC), Sergei Bogdan. The flight duration was 17 minutes and was completed in accordance with the conditions of the flight assignment.

Photos and video of the flight showed the Product 30 installed in the No. 1, or port-side, engine position, with a Product 117 engine remaining on the starboard side. The Product 30 features a serrated engine nozzle, compared to the flat nozzle on the Product 117.

The flight test was conducted by the second Su-57 aircraft prototype, also known as T-50-2.

In 2024, TASS reported, quoting sources, that 10 Su-57 fighters delivered to the RuAF in 2023 were powered by Stage 2 Izdeliye 30 engines. All Su-57 aircraft to be delivered in 2024 would feature the Stage 2 engine.

On December 11, 2024, an experimental Su-57 fighter equipped with the latest AL-51F1 turbofan engine featuring a shaped stealth nozzle and thrust vector control was showcased in the trailer for the documentary Lords of the Skies, aired by Russia’s Channel One.

Product 177 5th-Gen Engine

Rostec pitches the Product 177 as a fifth-generation aeroengine.

Under Rostec classification, a fifth-generation engine features a turbine inlet temperature of 1,750 K, 3D cooling techniques, advanced superalloys, and ceramic coatings.

A fourth-generation engine features a turbine inlet temperature of ~1,600 K, single-crystal turbine blades, and advanced coatings (thermal barrier coatings—TBCs).

The Product 177 engine was possibly developed to replace the AL-51F1 / Product 30 engine, incorporating improvements in technology since the initial flight of the Product 30 engine on a Su-57 in 2017.

If so, it is a more evolved variant of the AL-51F engine with more thrust and better fuel efficiency.

Based on technical disclosures such as thrust rating, the Product 177 engine is a closely related Product 30 variant and is dimensionally identical to the AL-51F engine.

There exists the possibility that Product 177 is an alternative powerplant for the export variant of the Su-57 fighter, with some of the advanced features of the AL-51F1 held back.

Over the past year or so, Rostec has pitched its Product 177S engine at airshows for export. (I dwell on the Product 177S in detail below.)

Notably, on December 22 the UAC announced that it is expanding its production capacity to increase the supply of Su-57 fighters to Russian troops and promote these aircraft for export.

“United Aircraft Corporation is currently implementing a program to expand production capacity. This will increase the volume of deliveries of the fighter to the troops, as well as actively offer the Su-57 in the export version for foreign customers,” the report says.

Under the circumstances, an alternative engine could be required both to meet additional engine requirements and to safeguard some critical technologies.

Product 177 engine fitted on Su-57 (via Rostec)

Product 177S Engine

The Product 177S is likely a smaller, lower-thrust variant of the Product 177 engine developed exclusively for the export market.

UEC first displayed the Product 177S at the Dubai Airshow 2025 as a fifth-generation engine that is superior to foreign counterparts in terms of tactical and technical characteristics and can be used as part of existing and future aircraft.

The 177S provides up to 14.5 tons of thrust, while its service life is three times higher—that is, the service life of the engine is significantly increased compared to engines of the previous generation.

The 177S provides more thrust than the AL-31F/FP fitted on Su-family aircraft, but has identical dimensions. It can replace AL-31F/FP engines fitted on Su-family aircraft without any modifications.

The engine has a service life of 6,000 hours. It can be operated above its rated maximum thrust by sacrificing some engine service life.

Higher engine thrust facilitates greater electrical power generation for the operation of additional electronic systems. It also allows the aircraft to perform more complex aerobatic maneuvers.

Fuel consumption in all flight modes is lower by 7%, leading to reduced operating costs and increased flight range.

Conclusion

The announced increase in production of the Su-57 and the development of an alternative engine would make the Su-57 an even more attractive proposition than before for countries like India, which is interested in acquiring three to four squadrons of an interim stealth fighter to plug the operational capability gap until the start of serial production of the AMCA fighter.

If the MoD were to acquire the Su-57 with Product 177 engines, it could also acquire and locally manufacture Product 177S engines for its Su-30MKI upgrade program. The commonality between the two engines would make maintenance much easier.

A First in Aerial Warfare? Assessing the Reported Geran Air-to-Air Kill

Photo Credit: Ukraine's Defence Intelligence Unit

A Russian Geran-2 drone may have scored its first air-to-air kill, creating aviation history. The supporting evidence, however, is largely circumstantial so far.

A Ukrainian Mi-24 helicopter from the 12th Separate Army Aviation Brigade was lost in combat on December 17, 2025.

The specific location or area of operation has not been publicly disclosed. However, in recent months, Ukrainian combat helicopters have not been operating near the front, so the loss cannot be attributed to a ground-launched missile.

In fact, Ukrainian combat helicopters have been largely co-opted for counter-drone operations, making it more likely that the loss occurred during such operations.

Official Ukrainian sources admit the downing as a combat loss. While it is possible that the helicopter was brought down by a Geran-2 drone, either by ramming or through the use of an air-to-air missile, there are other possibilities too, including controlled flight into terrain (CFIT) while positioning for an attack on a drone.

All four crew members were killed in the incident.

The Making of a 'Hero of Ukraine'

The Mi-24 was piloted by the deputy commander of the brigade, a “Hero of Ukraine,” Lieutenant Colonel Shemet.

A native of the Chernihiv region, Colonel Shemet graduated from the Syzran Higher Military Aviation School. After serving in the Ukrainian Armed Forces as a helicopter pilot, he retired before the start of the war.

He was recalled to duty following the start of the war and participated in the defence of the Azovstal steel plant in Mariupol between March and May 2022.

In an operation codenamed Air Corridor (also known as Air Breakthrough to Azovstal), Ukrainian Mi-8 helicopters flew daring resupply and evacuation missions amid the Russian siege of Mariupol.

In order to avoid detection by Russian radar and air defences, they flew a nap-of-the-earth (NOE) profile, sometimes as low as 20 ft above the ground or water, carrying critical supplies such as Stinger and Javelin missiles, ammunition, medicine, and Starlink satellite internet equipment to the besieged defenders. On their return to Ukrainian-held territory, they evacuated wounded soldiers.

Colonel Shemet was decorated with the “Hero of Ukraine” title for his participation in the operation.

Air-to-Air Combat Loss?

In early December, Ukrainian sources reported that Russian forces had operationally deployed upgraded Geran drones capable of launching R-60 air-to-air missiles. The Soviet-era short-range missile is mounted on a launcher on top of the drone. After launch, the heat-seeking missile can autonomously fly to its target.

The interceptor variant of the Geran drone operates as part of a swarm that includes other Geran drones configured for electronic warfare, photo reconnaissance, ELINT, communication relay, and decoy missions.

When launched from a fast-flying fighter aircraft, the R-60 has a range of 7–10 km. When launched from a slow-flying drone, its range would be significantly less.

For a successful engagement, the operator flying the drone remotely would need to establish visual contact with the target and maneuver the drone such that the missile’s seeker can obtain a lock onto the target.

According to the Defence Intelligence of Ukraine, Russia has adapted the Soviet R-60 air-to-air missile for drone launch in order to shoot down Ukrainian helicopters and airplanes that intercept Russian drones. The drone is equipped with two cameras—one in the nose and one behind the launcher. The placement of the cameras is likely aimed at helping the drone operator align the drone accurately towards the target.

Broadband communication between the drone and its remote pilot is facilitated through a mesh network, with several other Geran drones operating as communication relays.

Using the video streams relayed through the broadband communication link, the remote pilot can acquire the target using the stream from the front camera, align the drone with the target using video streams from the front and rear cameras, and launch the missile when in range.

The interceptor drone additionally features SATNAV (satellite navigation) hardened against electronic warfare, with a 12-channel jammer-proof Kometa module.

Following launch, the missile independently captures the target using its thermal seeker and autonomously steers itself towards it.

There is also a variant with preliminary target acquisition by the warhead and confirmation by the operator before launch.

The Geran drones armed with R-60 air-to-air missiles are primarily deployed to disrupt the use of combat helicopters and trainer aircraft for counter-drone operations.

It is likely that Ukrainian helicopters and trainer aircraft engaged in counter-drone warfare are already being equipped with defensive suites comprising sensors to detect missile threats and countermeasures such as heat flares.

Conclusion

While the exact reason for the combat loss of the Ukrainian Mi-24 helicopter is not known, it is clearly linked to the rapid evolution of drone warfare and the consequent need for counter-drone operations. Both are set to be part of any future warfare. Notably, both represent affordable forms of warfare that would be attractive to nations or groups with limited resources.

From India’s point of view, drone and counter-drone warfare represent technologies that can be handled exclusively by the private sector. Developing a Geran-type drone family, including a drone capable of launching a heat-seeking air-to-air missile, is a task that could well be executed by TASL or L&T. The same applies to interceptor drones.

Russia’s evolutionary development of drone technology is worth taking note of. More than technology alone, time and evolutionary iterations are critical to the development of an effective weapon system.

 

Dark Eagle vs S-500: Hypersonic Deterrence, Oreshnik, and the New Balance of Power

 

Image by @Grok

In the context of a recent announcement by President Putin that the Oreshnik missile will be placed on combat duty, a Russian military analyst told TASS that Russia has the industrial base to produce “tens, even hundreds” of Oreshnik missiles per year.

Alexander Stepanov, an analyst at the Institute of Law and National Security of the Russian Presidential Academy of National Economy and Public Administration, claimed that the missiles would provide strategic coverage for all critical areas and facilities in Russia’s border regions.

Stepanov believes that if the West escalates the conflict in Ukraine, Russia could use the Oreshnik missile to strike military-industrial targets supporting the escalation in Ukraine and in any NATO country providing military-technical support to Kyiv.

Dark Eagle

In his interaction with TASS, Stepanov also alluded to recent reports that the U.S. Army is poised to deploy the Dark Eagle hypersonic missile. In an earlier blog post, I covered the capabilities and the consequent threats posed by the missile.

Stepanov told TASS, “The S-500 is a multifunctional air-defense and missile-defense system, designed to destroy, among other things, low-orbit targets. The missiles will neutralize the enemy’s strategic potential, ensuring reliable interception of hypersonic missiles and the destruction of satellites in low orbits.”

How credible is Stepanov’s claim that the S-500 can reliably intercept hypersonic missiles?

Dark Eagle Trajectory

As mentioned in my earlier blog post, Dark Eagle is a boost-glide hypersonic weapon. As such, it needs to climb to a substantial altitude before the Common Hypersonic Glide Body (C-HGB) can detach and begin its hypersonic (Mach 10) flight to a maximum-range target 3,500 km away. Consequently, Dark Eagle would remain within the S-500’s detection and engagement zone for a certain period of time.

I sought confirmation from Grok with the following question:

"Dark Eagle: For striking a target at max range of 3,500 km, how high would the missile need to go to sustain speeds exceeding Mach 10?"

Grok's response was 

60 kilometers

To explain the solution for this closed-ended mathematics question:

The Dark Eagle is a boost-glide hypersonic missile. For a range of 3,500 km while sustaining speeds exceeding Mach 10, the glide phase occurs in the upper atmosphere to minimize drag and heating. Based on modeling hypersonic glide trajectories and comparisons with similar systems like the DF-17, the missile must reach an altitude of approximately 60 km to initiate and sustain the glide phase at these speeds. This altitude allows for low density to reduce deceleration while providing sufficient lift for the range. 

Lower altitudes would increase drag, causing the speed to drop below Mach 10 too quickly, while higher altitudes would require more energy from the booster, potentially reducing the effective range. The calculation involves equilibrium glide equations balancing lift, drag, gravity, and centrifugal force, using parameters like L/D = 2.6 and ballistic coefficient adjusted for hypersonic vehicles, leading to this altitude for the given conditions.

Glide Body Interception

Going by Grok's explanation, it is clear that the C-HGB will remain within the S-500’s detection and engagement zone for an adequate period of time. However, this does not imply that the S-500 will be able to reliably intercept the glide body, because the glide body would be maneuvering unpredictably.

S-500 System

The S-500 Prometheus air and missile defense system employs multiple interceptor types, with the long-range ones being the 77N6 and 77N6-N1 missiles. These are primarily designed for anti-ballistic missile (ABM) and anti-satellite roles, and are capable of engaging hypersonic threats, intercontinental ballistic missiles (ICBMs), and other high-altitude targets.

Their reported range is 500–600 km, depending on target type and configuration.

The system also includes the shorter-range 40N6M interceptor (up to 400 km) for anti-aircraft and cruise missile defense.

A formidable advantage of the S-500 is the ability of its interceptor missiles, such as the 77N6 series, to reach their maximum hypersonic speeds (around 5,500 m/s, or roughly Mach 16) within 4–5 seconds after launch.

However, interception of missiles or aircraft generally relies on calculating a “meeting point” in the sky based on the current speed, direction, and trajectory of both the target and the interceptor. When both are traveling at hypersonic speeds, the extreme rate of closure results in a very small engagement window.

Unpredictable maneuvering further compounds the challenge. The Dark Eagle’s hypersonic glide body can suddenly dip, weave, or change altitude mid-flight, thanks to its design and control surfaces. An intercept-point prediction algorithm can neither assume a steady trajectory nor reliably anticipate such maneuvers. In either case, it risks chasing a predicted position that is no longer accurate.

At hypersonic speeds, due to frictional heating, the glide body would be enveloped in a glowing plasma cloud that can obscure it from radar and other sensors. This makes it difficult to obtain a clear, real-time lock on its position, speed, or maneuvers. It is akin to trying to track a car through thick fog while it is swerving on a highway—you might catch brief glimpses, but not enough to accurately predict where it will veer next.

Interceptor Missile's Activer Radar Seeker

The active radar seeker on missiles such as the 40N6 (used in the S-500) provides significant advantages. It enables terminal-phase autonomy, which is particularly useful against unpredictably maneuvering hypersonic threats, as the seeker can adjust in real time to evasive actions or plasma interference at high speeds, improving hit probability compared to semi-active systems that rely on external guidance.

Active radar seekers also enable fire-and-forget launches and allow the system to handle multiple engagements simultaneously.

Conclusion

The S-500 system certainly has the capability to intercept the Dark Eagle. However, that does not imply it has the ability to do so reliably. For reliable interception, the interceptor needs to be substantially faster than the target. The U.S. Army claims that the Dark Eagle can cruise at least at Mach 10, while some reports place its cruise speed as high as Mach 17. At such speeds, the glide body could be faster than the S-500’s Mach 16 77N6 interceptor, which would reduce the reliability of interception. That said, the actual speed of the glide body would vary depending on range and trajectory.

The most lethal facet of the Dark Eagle is its high mobility. It is possible that the system could eventually feature air mobility. Because of this mobility, the positioning of an S-500 system cannot be dictated by the known locations of deployed Dark Eagle units. As a result, the U.S. Army could use the Dark Eagle to strike targets not protected by S-500 systems, or even target S-500 systems while they are on the move.

Additionally, Russia currently has only one operational S-500 system. Even with sustained serial production, it is unlikely to field enough systems to protect all strategic conventional and nuclear targets.

Dark Eagle: America’s Hypersonic Tool for Undermining Adversary Nuclear Deterrence

 

On December 12, the US Army and Navy successfully completed integrated testing of the Dark Eagle Long-Range Hypersonic Weapon (LRHW).

“The responsiveness, maneuverability, and survivability of hypersonic weapons are unmatched by traditional precision strike weapons,” said Lt. Gen. Robert A. Rush, Director of Hypersonic Systems at the Rapid Capabilities and Critical Technologies Office (RCCTO).

The US Army plans to integrate its version of the system onto a mobile, land-based platform. The US Navy will integrate its version, called Conventional Prompt Strike (CPS), with the capability to be launched from surface ships and submarines.

Dark Eagle Characteristics

The Dark Eagle is an intermediate-range boost-glide system featuring a booster rocket that carries a hypersonic glide body (C-HGB, Common Hypersonic Glide Body) housed in its nose cone. Once the booster rocket reaches a predetermined altitude and velocity, the C-HGB separates from the booster and begins its glide phase, descending toward the target while trading altitude for speed and maneuvering at hypersonic velocities.

The missile is claimed to have a range of approximately 2,175 miles (3,500 km) and speeds exceeding Mach 5. In all likelihood, the missile can travel significantly faster than Mach 5, based on the calculations below.

The missile is reportedly capable of flying its maximum 3,500 km range in under 20 minutes while maneuvering unpredictably. If this claim is accurate, the missile must cruise at speeds far in excess of Mach 5. At Mach 5, at lower altitudes where the speed of sound is approximately 1,100–1,200 km/h, the Dark Eagle would take roughly 35–38 minutes to reach its target. Factoring in unpredictable maneuvering, the flight time would be even longer—possibly exceeding 40 minutes. In other words, to meet the reported timelines, the missile must be capable of sustained cruise speeds closer to Mach 10.

It is therefore highly likely that Mach 5 represents the terminal speed of the missile rather than its cruising speed.

Destructive Capabilities

The weight and dimensions of the missile remain classified. However, based on analysis of available photographic evidence, the missile’s weight is estimated to be between 15 and 16 tonnes, with a length of approximately 11–14 meters and a diameter of about 0.876 meters.

The extremely high impact speed of the warhead is possibly corroborated by reports indicating that the missile’s blast-fragmentation warhead contains a relatively small explosive charge—approximately 30 pounds (13.6 kg)—but incorporates a very large number of fragments.

In other words, the missile relies primarily on the dissipation of the immense kinetic energy of its C-HGB, distributed through a wide spread of high-velocity fragments, rather than on explosive yield alone.

These fragments can cover a large area, making the missile particularly suitable for destroying targets such as S-400 air defense systems, training camps, and command-and-control nodes.

Outstanding Features

The four most notable characteristics of the Dark Eagle are its very high cruising and terminal speeds, relatively compact size, high mobility, and the wide yet lethal dispersal pattern of its warhead.

Its high cruise speed, low flight altitude, and unpredictable maneuvering would severely compress detection and engagement windows, even for adversaries equipped with advanced missile defense systems such as the S-400 or S-500.

The relatively small size of the containerized missile—comparable to the Chinese DF-17 with a range of 1,500 km—combined with twin launch containers mounted on a semi-trailer, would make pre-launch detection and counter-battery engagement extremely challenging.

The wide fragmentation pattern of the warhead would help compensate for any navigational inaccuracies caused by electronic warfare (EW) over the target area or by constrained maneuvering at hypersonic speeds.

As is the case with the ATACMS system, it would eventually be possible to airlift the Dark Eagle launcher and support vehicle(s) to any point on the globe, program the system with target coordinates in flight, and promptly launch the missiles on landing. 

Because the missile is not susceptible to easy interception by existing air defense systems, it is ideally suited for preemptive strikes against adversary air defense assets and command-and-control infrastructure.

Conclusion

Both Russia and China have developed surface-launched hypersonic weapons, but neither country has fielded a hypersonic weapon conceptually identical to the Dark Eagle.

Russia’s Oreshnik, for example, is also an intermediate-range ballistic missile capable of hypersonic speeds, but it is optimized to saturate adversary air defense systems using multiple independently targetable reentry vehicles (MIRVs). In contrast, the Dark Eagle prioritizes precision and kinetic impact, relying on its ability to penetrate air defenses rather than overwhelm them.

China’s DF-17 hypersonic missile was developed primarily for precision land-attack missions, such as degrading enemy air and missile defenses or striking fixed targets like US military bases in the Western Pacific. Like the Dark Eagle, it is designed to evade air defenses through hypersonic speed and maneuverability. However, its more limited range makes it a less versatile system.

Highlighting the Dark Eagle’s reach, an officer presenting the missile system to Secretary of Defense Pete Hegseth reportedly stated that its range would allow it to strike “mainland China from Guam, Moscow from London, and Tehran from Qatar.”

Conceptually, the conventionally armed Dark Eagle can be described as a weapon system designed to degrade an adversary’s deterrence capabilities—both conventional and nuclear. It is, fundamentally, a weapon intended to enable the US to fight and win wars under the protective umbrella of nuclear deterrence.

Ukraine’s Underwater Drone Marks a Major Leap in Naval Warfare

 

The Russian Black Sea Fleet (BSF) has denied any damage or casualties as a result of a Ukrainian attack on December 15 on a Russian submarine docked at the Black Sea port of Novorossiysk.

Following the attack, Ukrainian sources posted a video showing an explosion in close proximity to a Project 636 Varshavyanka submarine, an advanced variant of the Kilo-class submarine. The attack is claimed to have been executed by the SBU (Security Service of Ukraine) using a Sub Sea Baby UUV.

A naval attack by the SBU is, in reality, a euphemism for an attack by British special services.

The head of the fleet's press service, Captain 1st Rank Alexei Rulev, stated that the enemy’s attempt to carry out sabotage using an Underwater Unmanned Vessel (UUV) did not achieve its objectives and that no ships or submarines, nor their crews, sustained any damage and are operating as normal.

Going by the video footage posted online, the Ukrainian UUV struck near the stern of the Varshavyanka submarine, where critical propulsion and control systems are located, such as the propeller, vertical rudder, and aft horizontal rudders.

Interestingly, in the past, the BSF has not commented on the outcomes of Ukrainian attacks on Russian warships and submarines.

Sub Sea Baby

The Sub Sea Baby UUV is likely a derivative of the Sea Baby unmanned surface vehicle (USV) designed for operation on the water’s surface. The USV has a maximum speed of 90 km/h and a range of at least 1,000 km.

It is highly likely that the Sub Sea Baby has the capability to cruise on the sea surface as well as subsurface. Based on its likely routing, the Sub Sea Baby UUV would have travelled a distance of approximately 700 km for the attack. In order to achieve the extended range, it is likely that it used an optimum cruising speed of 40 km/h (22 knots). If so, it would have taken the drone 17 hours to traverse the distance.

Major Technical Advance

Clearly, the UUV attack represents a major Ukrainian technical advance. During subsurface cruise, the UUV would have to be capable of remote piloting, which is technically challenging. Executing the attack would require real-time ISR and situational awareness over a vast expanse of the sea to avoid detection by Russian drones.

The Sub Sea Baby could have evaded detection by drones patrolling the Black Sea by switching to subsurface cruise. On other occasions, the drone would have switched to surface cruise to avoid nets guarding the port against subsurface attacks.

Notably, Ukrainian sources were never secretive about their intent to use UUVs against the BSF. They flaunted the capability as soon as they achieved it.

It is not clear why the BSF was not able to intercept the UUV. The most likely reason would be that NATO ISR assets participated in the attack by providing real-time intelligence.

Also, it is conceivable that, in the days leading up to the attack, the SBU struck Russian commercial shipping in the Black Sea to divert Russian attention away from the threat posed by its UUVs.

Conclusion

Notwithstanding the uncertainty surrounding the outcome of the strike, extended-range UUVs have added a new dimension to the threat faced by Russian warships and commercial shipping in the Black Sea.

Update

Image via Military Informant Telegram Channel

A satellite image posted online indicates that the Sub Sea Baby drone missed the stern of the Varshavyanka sub by approximately 20 m. Damage to the docking pier is visible in the satellite imagery.

Additional Reading

Analysis by Mike Mihajiovic

Closing the Apache Chapter: Indian Army Bets on Prachand LCH

 

On December 15, 2025, The Times of India reported that the IA is set to receive the last three AH-64E Apache helicopters on order from Boeing Aerospace.

Three of the six AH-64E helicopters ordered by the IA arrived at Hindon Air Base on July 22, 2025. It was then reported that the remaining three helicopters would be delivered by November 2025.

The Indian MoD ordered six AH-64E helicopters from Boeing under an $800 million deal signed in February 2020, during the visit of former US President Donald Trump to India.

At the time of contract signing, Boeing had committed to deliver all six helicopters by February 2024.

IAF AH-64E Procurement

The IAF earlier acquired 22 AH-64E helicopters from Boeing under a $3 billion contract, which also included the supply of 15 CH-47F Chinook helicopters.

The IAF reportedly received the last batch of the 22 AH-64E helicopters it ordered in July 2020.

IA Forgoes Additional AH-64E Procurement

In early 2014, the Army received “in-principle” approval for “ownership” of 39 Apache AH-64 gunships to equip its “strike” formations. However, no additional orders have been placed beyond the six helicopters ordered. The Army now appears committed to expanding its fleet with indigenous options, such as the 5.8-ton, twin-engined Prachand Light Combat Helicopter (LCH).

The Prachand is powered by two Shakti engines and inherits many technical features of the Advanced Light Helicopter. Features unique to the LCH include a sleek and narrow fuselage, tricycle crashworthy landing gear, crashworthy and self-sealing fuel tanks, armour protection, and nuclear and low-visibility features, which make the LCH lethal, agile, and survivable.

The Prachand outperforms the AH-64E in its ability to operate at altitudes above 5,000 m, which is a critical requirement for Himalayan deployments. The programme targets over 65% indigenous content, involving over 250 domestic companies.

Prachand LCH

Indigenously developed weapon systems can more effectively address threat perspective–driven qualitative requirements (QRs). India’s requirement for a combat helicopter honed for high-altitude operations is unique. India’s disputed borders run through mountainous terrain. The Indian Army and Air Force need a combat helicopter that can fly at high altitudes with the agility to safely negotiate tight airspaces between mountains, allowing pilots to find and engage targets with ease.

MoD’s Unprecedented Large-Volume Order

The Indian MoD, on March 28, 2025, signed two contracts with Hindustan Aeronautics Limited (HAL) for the supply of 156 Prachand helicopters, along with training and other associated equipment, worth ₹62,700 crore. The first contract is for the supply of 66 LCHs to the Indian Air Force (IAF), and the second is for the supply of 90 LCHs to the Indian Army.

Deliveries will begin in the third year (2027–28) and continue over five years, with HAL producing about 30 helicopters annually from its Bengaluru and Tumkur facilities.

The new order will add to the 15 LSP variants of the helicopter (10 IAF and five Army) already inducted under a ₹3,887 crore contract inked in 2022. HAL completed delivery of the 15 LSP helicopters in early August 2023.

Prachand Capabilities

The Prachand is a low-observable (LO) design with reduced visual, aural, radar, and infrared (IR) signatures. It features canted panels for a lower radar cross-section and an IR suppressor for reduced IR signature.

The helicopter has a maximum speed of 275 kmph (148 kt), a combat radius of 500 km, and is capable of high-altitude warfare with an operational ceiling of 16,000 to 18,000 feet.

Prachand’s stub wings/armament booms have four weapon attachment stations, two on each side. Each station can carry ATGMs, rockets, or air-to-air missiles.

The helicopter has fixed armour plating on the sides and crashworthy landing gear for improved survivability.

Prachand Sensors

The Prachand is equipped with an electro-optical pod consisting of a CCD camera, FLIR, laser range finder (LRF), and laser designator (LD), giving the attack helicopter the ability to detect and acquire targets day or night.

It is not known whether an AESA radar is proposed for development for the LCH. Weight constraints might rule out this option, in which case the Prachand’s ability to carry long-range missiles may be severely constrained.

Prachand Communication Suite

Not much is known about Prachand’s communication suite in the public domain. A modern combat helicopter needs high-bandwidth communications, with support for direct connectivity with UAVs.

It is unlikely that the Prachand currently has a high-bandwidth communication suite adapted to operate within a battlefield command-and-control system. If that is indeed the case, an improved communication suite would be a priority item on HAL’s Prachand to-do list.

Weapon Systems

The Prachand will be equipped with the indigenously developed Helina surface-to-air missile, which can engage targets at ranges between 500 m and 7 km.

Helina features a 640 × 512 px FPA (focal plane array) imaging infrared (IIR) seeker. As a result, the Helina seeker can image the target—not just detect it—giving the missile the ability to recognise the target and ignore other heat sources in its vicinity.

Helina always uses LOBL (lock-on before launch) tracking, making it a “fire-and-forget” missile. Once the electro-optic (EO) system of the ALH identifies the target, it automatically hands it over to the missile.

Reposing Confidence in HAL’s Ability to Deliver

A single order volume of 156 helicopters is unprecedented for attack helicopters. By comparison, the Russian MoD’s last order for the combat-proven Ka-52M was for 114 helicopters.

The MoD’s large order is likely aimed at addressing concerns that, in the past, HAL has not been able to meet weapon system delivery timelines because the MoD did not place orders in time or for adequate volumes. Clearly, this time the MoD has reposed considerable faith in HAL’s ability to deliver.

Conclusion

The Prachand could well become an HAL success story, as it is derived from the Dhruv ALH, which entered operational service in 2002 and has accumulated approximately 450,000 flight hours.

The IA and MoD have placed a large order for the helicopter and given HAL more than two years to commence deliveries. It is almost certain that if HAL and DRDO deliver on the promise of the Prachand, there will be further orders for more advanced variants.