The Ramjet 155 Extended Range Artillery Projectile, developed by Boeing and Nammo, has successfully completed ground-fire testing, enabling long-range precise shots, which is one of the US Army’s top modernization goals.

Artillery is a type of heavy military ranged weapon that can fire explosives with a range and strength well beyond that of infantry weapons. Early artillery development centred on the ability to penetrate defensive walls and fortifications during sieges, resulting in large, stationary siege engines.

There are three ways to increase the range of artillery shells fired from a barrel:

• Rocket-assisted projectiles provide additional ‘push’ from a small rocket motor integrated into the projectile’s base, enhancing and maintaining the projectile’s velocity.
• Base bleed: employs a small pyrotechnic charge at the projectile’s base to deliver enough combustion products into the low-pressure zone behind the projectile’s base, which accounts for a significant percentage of the drag.
• Ramjet-assisted: Similar to rocket-assisted, but using a ramjet instead of a rocket motor; a ramjet-assisted 120-mm mortar projectile is expected to have a range of 22 miles (35 km).

The ramjet rocket motor technology developed by Nammo has completed a successful testing and development phase. During the development process, more than 300 completed rocket motor tests provided valuable feedback. The corporation now believes that the technology is well on its way to maturity and stability, as well as meeting performance goals.

Nammo is also working on the following projects: The 155mm HE-LR (long range) is one among them: A guided rocket-assisted projectile with a range of 70-85 kilometres. The first prototypes were recently tested, and work is nearing completion.

The 155MM HE-ER is the final product (extended range). This cannon has a range of more than 40 kilometres. In contrast to its siblings, it is constructed using traditional technology with the addition of a base bleed section that greatly reduces drag and hence increases range.

While less stunning than the others, it has the potential to have a significant influence on modern armies, effectively doubling their attack range.

Ramjet motors are currently being considered for use in artillery and missile systems, according to the business. Ramjet motors may now be fired from any L39 or L52/L58 artillery cannon, and have shown to be reliable in terms of ignition and in-house flight.

Nammo and Boeing have teamed up on a project to produce ramjets for 155mm artillery. Armed forces will gain from Boeing/experience Nammo’s in terms of increased range and a reduced demand for more expensive rockets. Furthermore, a common, survivable round design for both L39 and L52/L58 guns will reduce logistical challenges.

How does it work ? 

The first part of a ramjet is its diffuser (compressor) in which the forward motion of the ramjet is used to raise the pressure of its working fluid (air) as required for the combustion of fuel. It is then passed through a nozzle to accelerate it to supersonic speeds. This acceleration gives the ramjet forward thrust.

A ramjet is much less complex than a turbojet in so far as it comprises an air intake, a combustor, and a nozzle but no turbomachinery. Normally, the only moving parts are those in the turbopump, which sends the fuel to the spray nozzles in the combustor (liquid-fuel ramjet). Solid-fuel ramjets are simpler with no need for a fuel system.

A team from Boeing and the Norwegian company Nammo has conducted successful ground-fire tests of its Ramjet 155 Extended Range Artillery Projectile – a technology to enable long-range precision fires, one of the U.S. Army’s key modernization priorities.

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The tests, led by Nammo and conducted during the months of January and March in Norway, validated gun-launched survivability and performance predictions, and expanded Ramjet 155’s employment envelope.

Since 2019, Boeing Phantom Works and Nammo have been working together under a strategic partnership to jointly develop and produce the next generation of boosted artillery projectiles to meet the Army’s long-range, precision-fire priorities. Ramjet 155 uses an engine in which the air drawn in for combustion is compressed solely by the forward motion of the projectile at supersonic speeds. The program builds on the success of Boeing’s Joint Direct Attack Munition (JDAM) and Small Diameter Bomb (SDB) programs and addresses range, accuracy and volume of fire gaps between current artillery systems and those operated by potential adversaries.

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