Ramjet Powered Artillery Round can penetrate anti-access/area denial networks

Rajesh Uppal February 17, 2023 Energy & Propulsion, Weapons Comments Off on Ramjet Powered Artillery Round can penetrate anti-access/area denial networks 401 Views

One of the major lessons from Ukraine’s artillery war is that the side that can shoot farthest dominates the battlefield. According to the report, Russian howitzers are expending 20,000 shells daily on average, compared to 6,000 fired by Ukraine. The ratio for rocket artillery and ballistic-missile launches is even worse. And Ukraine still risks exhausting its supply of Soviet-standard 152-mm shells even faster than Russia does.

Russia’s 152-millimeter 2S19 Msta-S self-propelled howitzers have a range of 24.7 kilometers, or 15.3 miles. Moscow’s newer 2S35 Koalitsiya self-propelled gun has a standard range of 40 kilometers, or 24.8 miles. These guns have outshot Ukraine’s 2S3 self-propelled howitzers, which had a range of just 10.8 miles. As a result, Ukrainian artillery forces have had to continually operate their guns within range of Russian guns, placing them in constant danger. Russian gunners, on the other hand, can stay out of reach of Ukrainian guns with careful planning.

Most artillery shells are sent downrange by the detonation of a propellant charge in the breech of the gun. The charge creates pressure behind the shell, which then pushes the shell out of the barrel and downrange to the target. More propellant can mean more range, but at a certain point that becomes dangerous. Instead, some shells inject a gas into their wake, reducing drag as the shell flies through the air, a method called “base bleed.” Other shells, so-called “rocket-assisted projectiles” (RAP), use actual rocket engines to fly farther.

“This could be a game-changer for artillery,” Thomas Danbolt, Vice President of Nammo’s Large Caliber Ammunitions division, said in a press release headlined “We are basically launching a missile from a cannon!” on June 12, 2018.

Ramjet Powered Artillery Round

Ramjets are air-breathing engines that suck in air at high speeds and then mix it with gasses produced by fuel combustion. The air and exhaust under pressure is then expelled through the rear nozzle, producing thrust. The ramjet round uses the force of launch to get it moving fast enough to start the ramjet motor. A solid fuel source will get the projectile up to a maximum speed of three times the speed of sound and keep it moving at that speed for approximately 50 seconds.

A ramjet-powered shell has a few advantages over base bleed and RAP technology. One, the shell uses the oxygen in the air itself as a propellant, and there’s plenty of oxygen in the atmosphere. This reduces the amount of onboard fuel the shell needs. This type of motor also reduces drag on the shell itself, since it’s actively pulling the projectile through the air. Second, unlike the other types of shell propulsion, the ramjet shell can accelerate over a greater distance, giving it greater speed up until impact. Traditionally, we would utilize a method called ‘base bleed’ where a chemical at the base of the shell burns emits gas to fill the vacuum behind the shell to reduce the base drag force. Base bleed enables an increase of range by 10 to 20 per cent. A ramjet-powered artillery round can increase range by over 100%.

Of course, a ramjet shell does have some disadvantages. For one, the addition of a ramjet engine makes it much more expensive than a typical artillery shell. Two, the shell must incorporate a guidance package, steering fins, and the ramjet, reducing the shell’s explosive payload.

A laser- or millimeter wave radar-guidance package could add additional flexibility to the system in the future. These systems could allow the projectile to hit moving targets at long ranges and, in the case of a laser-guided round, with manned or unmanned aircraft or forward-deployed troops on the ground designating the target with a laser or otherwise sharing that information with the artillery unit.

Ramjet 155 artillery shell

The new Ramjet 155 shell, jointly developed by Boeing and Norwegian defense company Nammo, is the first artillery shell to use a ramjet for propulsion. The shell has been in development since 2019, when the Army funded it as part of the XM1155 Extended Range Artillery Projectile program.

The latest Ramjet 155 test, announced by Boeing and Nammo was conducted in June 2022 at the Andøya Test Center in Norway. The shell’s ramjet engine ignited successfully and it “demonstrated flight stability with a well-controlled engine combustion process.”

Older artillery systems without precision guidance lacked the ability to land a shell directly on top of a target, instead neutralizing targets by dropping multiple shells nearby. Ramjet 155’s precision guidance system is likely accurate enough to drop a shell on top of the target. That requires fewer shells lobbed and less high explosives per shell. Artillery units will also be able to provide support to ground forces that was previously supplied by strike fighters and attack helicopters. Plus, the ability to shoot moving targets puts a bullseye on enemy tanks.

At Eurosatory 2018, Nammo’s Danbolt noted that that the ramjet round wouldn’t just extend the maximum range of a single howitzer, but would greatly expand the flexibility of individual artillery units to engage different targets. According to the executive, a six-gun battery would be able to hit anything within an approximately 1,500 square mile circle around their firing position with the new XM1113. The ramjet rounds would exponentially increase that possible target area to more than 12,000 square miles without the howitzers ever having to relocate.

What this means is that ground forces could operate far further from those elements while still having vital artillery support on call. Fewer artillery units could also cover a much wider front. Perhaps most importantly, it would allow the howitzers to sit much further removed from the front lines, better protecting them from immediate enemy counter-battery fire and air strikes.

Ramjet 155 isn’t a game changer by itself, as the gunners manning their howitzers can’t see enemy forces 44 miles away. The new shell will change the game once it is dropped into a reconnaissance-strike system that pairs drones and other intelligence-gathering systems with long-range artillery, the two groups connected by secure communications. Artillery units will be able to shoot deeper into enemy territory, and fire more shells without moving to avoid enemy fire. It’s a stunning combination that should give any potential adversary pause.

Indian development

The department of aerospace engineering at IIT Madras is working on developing a next-generation artillery shell that can be used by the Indian Army to hit targets that are nearly twice as far the existing distances, with greater precision. Extending the range of a shell would be highly useful in non-contact warfare scenario, like the situations on the western border. Indian Army’s Artillery units engage targets inside Pakistan quite regularly. A doubling of the range will allow the artillery units to hit targets much deeper inside Pakistan at a relatively lower cost. Thereby increasing the effectiveness of Artillery along the LoC.

When a shell travels for around 30kms, the normal methods of correction are applicable. However, when a shell travels 60kms, it would be affected by wind and weather conditions far more. So, we would incorporate some kind of system to keep it on the intended track. It is called a Precision Guided Kit. We will be developing the precision-guided kits, especially for such extended ranges.

The new shells are compatible with all the existing artillery guns such as Bofors, Dhanush, Vajra and ATAGS. It is a fact that each gun has its own characteristics, but the shell we are developing is of a 155mm calibre. Hence, it would be usable on all Indian or foreign platforms that utilize the 155mm shell.

The propellant used must have the following qualities :

To prevent accidental detonation the propellant must be shock resistant.
It must be a sufficiently fast burning fuel allowing the shell to fly faster. The size & mass restrictions means a propellant with high energy density in needed.
The propellant must have a greater proportion of fuel to oxidiser. In other words, the propellant must be fuel rich.
The fuel must undergo complete combustion leaving minimal amount of solid residue behind.
It must be cheap to produce. If the propellant is expensive then mass production will be a very expensive prospect. That will diminish the promise of this tech.

Material Selection:

The new propellant will have proven components. This will reduce risks. The components are :

Aluminum (Al) : Fuel
Iron Oxide (IO) : Desensitized reactant.
Hydroxyl Terminated Poly Butadiene (HTPB) : Binder
Poly Tetra Fluoro Ethylene (PTFE) : Activator
Ammonium Perchlorate (AP) : A very powerful oxidiser

References and Resources also include:

https://www.popularmechanics.com/military/weapons/a40864973/ramjet-powered-artillery/

https://www.strategicfront.org/research-work-in-ramjet-powered-artillery-shell-the-story-so-far/