CHENNAI: India is edging towards a quiet but consequential shift in land warfare. The Indian Army is testing a ramjet-powered 155-mm artillery shell, an air-breathing projectile that could dramatically extend the reach of conventional guns without altering existing artillery systems. If inducted, the programme would place India among a handful of countries globally to operationalise ramjet propulsion in tube artillery.
The technology has emerged from a long-running collaboration between the Army Technology Board and the Indian Institute of Technology Madras (IIT-M), reflecting a rare alignment of battlefield requirements and academic research. Unlike rocket-assisted projectiles, which carry both fuel and oxidiser and are constrained by limited onboard propellant, the ramjet shell carries only fuel and draws oxygen from the atmosphere once it reaches supersonic speed after launch.
Fired from a standard 155-mm gun, the shell exits the barrel at around Mach 2, sufficient to initiate ramjet operation. Incoming air is naturally compressed through the intake, mixed with fuel-rich gases generated inside the shell, and ignited to produce sustained thrust during flight. As an air-breathing system, the ramjet delivers a specific impulse exceeding 4,000 Ns/kg, significantly higher than the 2,400–2,500 Ns/kg typical of solid rocket motors, allowing far greater energy extraction for the same propellant mass.
The core challenge lay in making this physics work within the severe constraints of artillery design. “The difficulty was achieving efficient combustion within a very limited combustor length, while ensuring the system survives the extreme acceleration and stresses of gun launch,” P A Ramakrishna of IIT-Madras’ Department of Aerospace Engineering has noted in technical studies. Artillery shells must also remain spin-stabilised, further narrowing design margins.
To overcome this, the IIT-M team developed specialised fuel-rich solid propellants using aluminium, ammonium perchlorate and HTPB binders. Laboratory and simulation studies demonstrated zero-residue combustion, high burn rates at manageable chamber pressures, and mechanical robustness comparable to base-bleed units currently in service. Parallel aerodynamic studies explored front-intake ramjet configurations optimised for the Mach 2–3 flight regime, enabling efficient airflow without requiring any modification to existing gun barrels or breech mechanisms.
This design choice is strategically significant. The ramjet module can be retrofitted onto standard 155-mm shells and fired from the Army’s current artillery inventory, including the US-origin M777 ultra-light howitzer. Developmental and field trials, including firings at the Pokhran ranges, have already demonstrated the feasibility of the concept.
Army assessments indicate the ramjet shell could extend the effective range of tube artillery by 30–50 per cent while preserving payload and lethality. Operationally, this translates into deeper strikes without forward gun movement, reduced vulnerability to counter-battery fire, and enhanced flexibility across plains, deserts and high-altitude theatres.
It is expected to reach around 50-60 km, which is double the range of 155-mm artillery (24-30 km) .