Last month, IIT-Madras announced it had developed a ‘ramjet-assisted artillery shell’, which essentially involves fitting a ‘ramjet’ onto a 155 mm (diameter) shell. For many reasons, the new, smart shell is an engineering marvel.
Ramjet is an engine that sucks in air as the vehicle rushes forward — the air gets naturally compressed, mixes with fuel and burns. This generates thrust without needing any moving parts like turbines.
Ramjets are regularly used in missiles. Even the large turbofans we see under the wings of commercial aircraft basically work on the principle of taking in air, compressing it, and letting it slip from the rear to generate thrust. But putting a ramjet on a metre-long shell is quite a wrestle.
Within the limited space, the ramjet must withstand the extremely high speed (Mach 2-3) and acceleration (10,000-20,000 g); withstand the consequent violent pressure and heat; and ignite just after the shell leaves the muzzle, but never earlier.
Range vs lethality
Apart from IIT-Madras, only the Norwegian company Nammo has developed a ramjet-assisted shell; the difference is that Nammo has a working version, whereas IIT-M’s shell is not yet in production.
Moreover, while the Norwegian shell has air intake tubes in the front, the Indian research team preferred to place them on the side, leaving the front for warheads, Prof. PA Ramakrishna of IIT-Madras told businessline. This retains the lethality of the shell but cuts into the extra range it could have got. Ramakrishna recalled that, many years ago, another team had worked on a ramjet for shells with front air intake, but had not been successful.
The Indian side seems to be satisfied with the range it has achieved. Ramakrishna conservatively says the ramjet raises the shell’s range by 50 per cent, but reports suggest the extra throw could go as high as 80-100 per cent, depending on the gun used. With the advanced towed artillery gun system (ATAGS), the range increases to 72 km, against 38 km without the ramjet; with the K9 Vajra howitzer (produced by L&T in collaboration with Korea’s Hanwha Aerospace), the range increases from 40 km to 62 km. Nammo is said to have a range of over 100 km, but the Indian researchers believe their product is more devastating.
An interesting engineering point about the ramjet shell is the positioning of the engine — it sits in the rear, replacing the conventional ‘base-bleed’ — a small, solid propellant gas generator used to maintain the back pressure. As the shell screams forward, it splits the air, which then flows around the shell and merges at the back. This creates a conical low-pressure zone behind the shell, and the pressure difference between the front and the back pushes the shell backwards. The gas from the base-bleed is used to neutralise this drag, which would otherwise reduce the kinetic energy and, thereby, the range of the shell.
“When ramjet is used, base-bleed is not required,” says Lt Gen PR Shankar, former director-general of artillery, who was part of the ramjet research team at IIT-Madras as a professor of practice.
Both the ramjet and the base-bleed use up real estate in the shell, but the ramjet is a better device as it is a propulsion system whereas the base-bleed is only an aerodynamic aid.
Tactical flexibility
The Indian technologists have given the country a first-of-its-kind, fully 3D-printed ramjet-assisted shell, which raises the firepower of the army. “While missiles offer long-range strike capability, they are expensive and complex. Artillery guns remain the backbone of battlefield firepower due to their simplicity, survivability and cost-effectiveness, but have traditionally faced hard technological limits on range,” says an IIT-Madras press release, which calls the ramjet-assisted shell “a significant milestone in the indigenous development of defence technology”.
“If fully realised, this technology could allow Indian artillery units to engage targets at nearly 50 per cent more distances, offering commanders greater tactical flexibility, deeper strike options and enhanced deterrence — without the need for new gun platforms or costly missile systems,” says Ramakrishna, adding that the design “ensures that the extended range does not dilute battlefield impact, maintaining the lethality”.
He says more tests are needed before the product can be readied for mass production — but that is only a matter of a few years. The only negative — if it can be called that — is that the shell is much more expensive at ₹2-3 lakh, compared with about ₹1.25 lakh for a conventional 155 mm shell. However, apart from the extra muscle the shell would give the army, it has given India a gloss of prestige. “There has been a lot of interest internationally,” says Ramakrishna.
There is, perhaps, one unfinished agenda: providing a guidance system for the shell. Finger-on-lips — perhaps the choice of side air-inlet is to create room in the front for a navigation system. Asked if the shell is guided, Shankar replied, “Not yet”. Two telling words.
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Published on February 9, 2026
