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A-IX-2
A-IX-2
A-IX-2
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A-IX-2 (or hexal) is a Russian explosive used in modern Russian military shells. It consists of 73% RDX with 23% aluminium powder, phlegmatized with 4% wax.[1] Its relative effectiveness factor is 1.54.[2]

It has been in use by the Red Army since WWII.

References

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A-IX-2

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A-IX-2 (also known as Hexal) is a high-explosive composition originating from Soviet-era developments, primarily used as a bursting charge in Russian ordnance. It consists of 73% (cyclonite), 23% aluminum powder, and 4% as a phlegmatizer, making it an aluminized explosive that enhances blast effects through the addition of aluminum as a fuel. Developed as an improvement over earlier explosives like A-IX-1, A-IX-2 provides high from its base and enhanced in confined spaces due to aluminum afterburning that sustains . Mechanical tests reveal that A-IX-2 exhibits a stress-strain behavior with three distinct phases: a brittle elastic phase, a nonlinear elasto-plastic phase, and a strain-softening phase, indicating its sensitivity to high-strain-rate loading in applications like projectile impacts. A-IX-2 is employed across a wide range of Russian munitions, including high-explosive fragmentation shells (e.g., 152mm OF-25 with 6.4 kg fill), rounds (e.g., 125mm 3OF26 with 3.15-3.34 kg), systems (e.g., 122mm 9M22 Grad), mortar rounds (e.g., 120mm OF-49 with 4.9 kg), and cluster submunitions (e.g., 9N24 with 1.45 kg). Its versatility stems from the composition's castability and stability, allowing integration into both guided and unguided systems for anti-personnel, anti-armor, and area-denial roles. As of August 2025, A-IX-2 is being replaced by TNT-aluminum mixtures like TA-20 in some projectiles such as the 3OF27.

Composition

Ingredients

A-IX-2 is a composite explosive consisting of 73% cyclotrimethylenetrinitramine (), 23% aluminum powder, and 4% wax by weight, as specified in Soviet and Russian military technical documentation from the late . The primary component, , serves as the main high explosive base, delivering the core detonation velocity and essential to the mixture's performance. Aluminum powder functions as a fuel additive, boosting blast energy via post-detonation that produces thermobaric effects and amplifies destructiveness against targets. The wax, typically paraffin, acts as a phlegmatizer, desensitizing the composition to shock and while enhancing stability for safe handling and storage.
ComponentProportion (by weight)Role
73%Primary high explosive base for detonation power
Aluminum powder23%Fuel additive for enhanced blast via thermobaric effects
Wax (paraffin)4%Phlegmatizer for reduced sensitivity and improved stability

Formulation

A-IX-2 is prepared by mixing , aluminum powder, and to form a homogeneous composition suitable for or pressing. The acts as a desensitizer to reduce mechanical sensitivity while maintaining explosive performance, stabilizing the mixture against impact and friction and making it safer for handling compared to pure . The final product is a castable that is pressed into shells or molded into charges, achieving high uniformity for reliable . during emphasizes the elimination of air pockets and segregation through thorough agitation and sieving.

Properties

Physical properties

A-IX-2 possesses a density ranging from 1.70 to 1.75 g/cm³, lower than that of pure at 1.80 g/cm³ owing to the inclusion of aluminum (density approximately 2.70 g/cm³ but with low packing in powder form) and paraffin wax (density around 0.90 g/cm³). This reduced density compared to pure facilitates efficient loading and packing within munitions casings, optimizing volume utilization without compromising structural integrity. In terms of mechanical sensitivity, A-IX-2 demonstrates moderate impact sensitivity, with a 50% initiation height (h₅₀) of 60 cm in standard drop tests using a 2 kg weight. This renders it less sensitive than pure (h₅₀ ≈ 30 cm) due to the desensitizing effects of the binder but more sensitive than TNT (h₅₀ ≈ 140 cm). The material appears as a grayish, paste-like solid upon casting, attributable to the fine aluminum powder dispersed in . It is non-hygroscopic, resisting absorption, and exhibits low volatility, contributing to its stability during handling and storage. Thermally, A-IX-2 shows decomposition onset between 180–200°C, consistent with the behavior of its primary component, while the wax enables casting at approximately 80°C by lowering the effective of the mixture. It maintains stability for storage up to 60°C, aligning with standard guidelines for high explosives to prevent premature decomposition.

Explosive performance

A-IX-2 exhibits a ranging from 7,200 to 7,500 m/s, a value slightly lower than pure due to the incorporation of aluminum powder, which nonetheless enhances overall impulse through post-detonation of the metal additive. This velocity supports reliable propagation in confined munitions, contributing to effective generation during . The aluminum's role as a secondary , as outlined in the composition, amplifies the sustained energy release beyond the initial high-explosive phase. The and power of A-IX-2 are characterized by a relative effectiveness factor (REF) of 1.54 relative to TNT (set at 1.0), reflecting its capacity for fragmentation and structural disruption. This enhanced performance stems from the aluminized formulation, which boosts output during , providing greater demolishing potential than non-aluminized RDX-based mixtures in applications requiring both shatter and effects. In terms of blast effects, A-IX-2 generates thermobaric-like overpressure profiles, where the aluminum reacts with detonation products after the initial shock, prolonging the fireball and wave compared to conventional non-aluminized explosives. This extended duration intensifies impulse delivery, making it suitable for area-denial scenarios by combining high-velocity shock with lingering and hazards.

Development

History

A-IX-2 was developed in 1940 by Soviet naval engineer E.G. Ledin and colleagues, building on World War II-era research into hexogen (RDX). This development occurred amid efforts to create high-performance explosives for military applications during World War II. The explosive entered service during World War II, from 1942 onward, primarily for artillery and aerial munitions, where it replaced less powerful fillers such as TNT in shells. It saw use in Russian operations in Syria starting in 2015. It bears a relation to the earlier A-IX-1 formulation, though A-IX-2 incorporates enhancements for greater effectiveness. A-IX-1 serves as the primary predecessor to A-IX-2 in Soviet and Russian explosive development, formulated with 94–96% (hexogen) and 4–6% to phlegmatize the mixture and reduce sensitivity for use in older munitions such as PG-7 warheads. This composition results in a of approximately 7,950 m/s, providing reliable performance in bombs and shells but with higher impact sensitivity compared to aluminum-enhanced variants like A-IX-2 due to the absence of fuel additives that moderate shock response. A-IX-1's design prioritized for fragmentation effects in legacy systems, contrasting with A-IX-2's focus on sustained blast for broader anti-personnel roles. Hexogen, the pure form of , forms the foundational high in A-IX-2, consisting of 100% RDX crystals with a exceeding 8,700 m/s at densities around 1.8 g/cm³, enabling superior for penetrating or fragmenting impacts. Unlike A-IX-2, which incorporates aluminum to extend post-detonation and amplify in confined spaces, pure hexogen lacks this afterburning capability, limiting its effectiveness against soft targets and emphasizing instead high-velocity shock waves suitable for or anti-armor purposes. OKFOL represents a contemporary Soviet-era alternative to A-IX-2, developed in the 1980s as a phlegmatized -based explosive containing 96% (octogen) and 4% wax, achieving a of about 8,670 m/s for enhanced shaped-charge performance in anti-tank guided missiles like the . Although OKFOL delivers higher energy release and velocity than A-IX-2, its higher production costs and potential for corrosive byproducts from decomposition make A-IX-2 more favorable for general shells, where stability and economic viability support widespread deployment in blast-focused applications. Internationally, A-IX-2 shares conceptual similarities with the U.S. PBXN-109, a comprising 64% , 20% aluminum powder, and a binder for compliance in missiles like the Penguin anti-ship . However, A-IX-2's elevated aluminum content (23%) shifts emphasis toward thermobaric enhancement, promoting prolonged fireball and pressure waves for anti-personnel effects, whereas PBXN-109 balances armor penetration with reduced vulnerability in naval environments.

Applications

Military uses

A-IX-2 serves primarily as a high-explosive filler in Russian military munitions for delivering fragmentation and effects during , significantly enhancing lethality against soft targets such as and unarmored vehicles. Its aluminized formulation provides tactical advantages by boosting the relative explosive effectiveness to 1.54 times that of TNT, which translates to an approximate 15-20% increase in due to elevated post-detonation temperatures and pressures; this makes it well-suited for area denial operations and urban combat environments where maximizing is critical. In line with emphasizing massed indirect fires for anti- suppression, A-IX-2 became a standard filler in and systems from the late Soviet era onward, prioritizing enhanced to disrupt personnel in open or confined spaces. Its use in variants has been highlighted in UN reports on explosive remnants of war during the .

Specific munitions

A-IX-2 serves as the primary explosive charge in the Russian 152 mm OF-25 high-explosive fragmentation (HE-FRAG) , which contains approximately 6.8 kg of the filler for enhanced blast and shrapnel effects. This munition is compatible with 152 mm systems, including the self-propelled , achieving maximum ranges of up to 25 km with full charges. In rocket artillery, A-IX-2 is employed in cluster warheads such as the 9M55K variant for the 9K58 Smerch multiple launch rocket system, which disperses 72 submunitions including the 9N24 HE-FRAG type. Each 9N24 bomblet weighs 7.45 kg overall and incorporates 1.45 kg of A-IX-2 to generate fragmentation upon detonation. For tank ammunition, the 125 mm 3OF26 high-explosive fragmentation (HE-FRAG) round utilizes 3.15-3.34 kg of A-IX-2 as its main charge. This configuration is fired from and series main battle tanks. A-IX-2 is also used in other munitions, including the 122 mm 9M22 rocket for the multiple launch rocket system (6.4 kg fill), the 120 mm OF-49 mortar round (4.9 kg fill), and the VOG-25 (48 g fill).

References

  1. https://bulletpicker.com/a-ix-2.html
  2. https://patents.google.com/patent/US6110308A/en
  3. https://www.fenixinsight.com/blog/bulletins/change-of-explosive-fill-for-3of27-tank-gun-projectiles
  4. https://osmp.ngo/osmp68/
  5. https://www.researchgate.net/publication/348299403_Experimental_study_on_the_breaking_of_A-IX-2_explosive_by_submerged_cavitation_water_jet
  6. https://www.gichd.org/fileadmin/uploads/gichd/Publications/GICHD_Ukraine_Guide_2022_Second_Edition_web.pdf
  7. https://arconpartners.net/products/ammunition/large-caliber/125-mm-round-3vof36-with-high-explosive-fragmentation-fin-stabilized-projectile-3of26-he-frag-fs-for-125-mm-tank-gun-2a46-d81/
  8. https://www.globalsecurity.org/military/library/report/2002/iraq-osgjs-eod_03-markings-terms-etc.pdf
  9. https://www.bulletpicker.com/pdf/DST-1160Z-029-94.pdf
  10. https://19january2017snapshot.epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_contaminant_rdx_january2014_final.pdf
  11. https://link.springer.com/article/10.1007/s10573-008-0073-2
  12. https://www.sciencedirect.com/science/article/pii/0040603177800397
  13. https://miningandblasting.wordpress.com/wp-content/uploads/2009/09/explosives-6th-edition-by-meyer-kohler-and-homburg-2007.pdf
  14. https://repo.bg.wat.edu.pl/docstore/download.seam?entityType=article&entityId=WAT623dd6259c1f4c888d32ee36067ba19c&fileId=WATb83ee90dd1f5441ba78d94e2aac63a8c
  15. https://www.prvaiskra-namenska.com/rdx/
  16. https://scindeks-clanci.ceon.rs/data/pdf/1820-0206/2015/1820-02061503003B.pdf
  17. https://apps.dtic.mil/sti/tr/pdf/ADA279600.pdf
  18. https://repo.bg.wat.edu.pl/info/article/WAT623dd6259c1f4c888d32ee36067ba19c/
  19. https://www.gichd.org/fileadmin/uploads/gichd/Publications/Explosive_weapon_effects_web.pdf
  20. https://link.springer.com/article/10.1134/S0040579509020134
  21. https://forum.il2sturmovik.com/topic/21575-russian-planes-are-made-out-of/
  22. https://www.twz.com/ukraines-locally-produced-artillery-shells-have-reached-the-front
  23. https://armamentresearch.com/wp-content/uploads/2023/11/ARES-Special-Report-5-Cluster-Munitions-Submunitions-in-Syria.pdf
  24. https://apps.dtic.mil/sti/pdfs/ADA419438.pdf
  25. https://mezha.ua/en/2023/01/03/ukrainian-made-152-mm-shells-at-the-front/
  26. https://armamentresearch.com/soviet-9n24-submunitions-documented-in-ukraine-2022/
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