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Ramjet Technologies

The U.S. Department of Defense and the Norwegian Ministry of Defence announced their intent to continue a bilateral effort to explore advanced solid fuel ramjet technologies. The Tactical High-speed Offensive Ramjet for Extended Range, or THOR-ER, is an Allied Prototyping Initiative (API) effort under the Directorate for Advanced Capabilities within the Office of the Under Secretary of Defense for Research and Engineering.

Norway and the U.S. will extend their THOR-ER project, which aims to jointly develop and integrate solid fuel ramjet technologies into full-size prototypes that are affordable and can attain high-speeds and extended ranges (Nammo photo)

The THOR-ER effort aims to cooperatively develop and integrate advancements in solid fuel ramjet technologies into full-size prototypes that are affordable, attain high-speeds, and achieve extended range, culminating in flight demonstrations in operationally relevant conditions. The effort will also consider potential U.S. and Norwegian co-production opportunities.

«This continuation is an important next step in advancing high-speed propulsion technologies with our Norwegian partners», said Doctor Michael Griffin, Under Secretary for Research and Engineering. «It will drive fielding of the critical technologies needed to ensure U.S. and Allied military superiority in hypersonic systems».

THOR-ER continues collaborative research efforts involving the U.S. Navy’s Naval Air Warfare Center, Weapons Division China Lake; the Norwegian Defence Research Establishment; and Norwegian industry partner Nammo.

«I am very pleased with the prospects of this initiative. Not only will it provide a game changing capability for our Armed Forces, it also brings bilateral cooperation to a whole new level», said Mr. Morten Tiller, Norwegian National Armaments Director. «The THOR-ER development incorporates the results of long term R&D on missile and rocket technology in Norway. In my opinion this merger of US and Norwegian R&D efforts and engineering skills strengthens alliance innovation, in addition it represents an opportunity for closer defence industrial base cooperation».

«Nammo’s new propulsion solutions are closing the range gap between the US and its future potential adversaries. Our involvement in THOR-ER allows us to bring together the best of US and Norwegian propulsion technology through the framework of a bilateral US-Norwegian partnership, and this fits perfectly with our long term ambitions», said Morten Brandtzæg, President and CEO of Nammo Group.

The Allied Prototyping Initiative, launched in 2019 by the Office of the Under Secretary of Defense for Research and Engineering through its Advanced Capabilities directorate, leverages new and existing frameworks for international cooperation in research and development, so that the U.S. and its closest Allies can co-develop prototypes to bolster their military superiority. The goal of the API is to rapidly co-develop high-impact, game-changing, large-scale operational prototypes and to explore opportunities to energize the industrial bases within the U.S. and its closest Allies.

Ramjet shell

For years, NATO artillery and missile systems have been at a range disadvantage compared to its future potential adversaries. New ramjet technology, however, has the potential to completely reverse the situation by closing the range gap.

Ramjet-powered artillery could reach as far out as 150 km/93 miles. With guidance, the projectile would be a mix of a missile and an artillery shell. The 155-mm HE-ExR (extreme range), as it is called, is scheduled for its first live-fire tests in 2020 (Photo/illustration: Nammo)

In the summer of 2016, Russia rolled out the latest version of the 9A52-4 Tornado rocket launcher. The «S»-variant now has the ability to fire shells at an enemy 120 kilometers/74.5 miles away, a remarkable improvement on the previous version. But even the previous version could reach targets 70 km/43.5 miles away.

At the same time, the country appears to be investing in other, more untraditional long-range missile systems. The recent accident near Severodvinsk – in what appears to have been a test of a new nuclear-powered cruise missile – is just one indication of this investment, as is the use of conventional cruise missiles in Syria.

NATO has favored a different approach: For decades, the alliance relied on air superiority. That situation is however changing rapidly. As air defense systems like the S-400 proliferate, Russian planners apparently hope to deny their opponents free use of the skies.

U.S. Army Chief of Staff, General Mark Milley, is one of many experts who now believe the situation has changed fundamentally – and put NATO forces at a disadvantage. When he appeared before the U.S. Senate Armed Services Committee in April 2016, Milley was asked whether the army was «outranged».

«We don’t like it, we don’t want it, but yes, technically [we are] outranged, outgunned on the ground», Milley said.

With superior range, artillery operators could simply disregard counter-battery fire, Thomas Danbolt, Nammo’s Vice President Large Caliber Ammunition, explains (Photo: Nammo)

 

The importance of range

Range – and especially the ability to hit at a distance where an opponent cannot retaliate – has been a prime concern on the battlefield since the days of the Romans. Sometimes, such an advantage has proven to be a deciding factor.

Roman triumvir Crassus is one who certainly would attest to that. When facing Parthian horse archers at the battle of Carrhae in 53 BC, his legions were wiped out when they could not counter their opponents’ range and mobility advantage.

Later, the English would inflict enormous damage on French forces in the Hundred Years’ war. At Crecy, Poitiers and Agincourt, English longbowmen significantly outranged their opponents. The great English victories here would effectively end the primacy of heavily armored knights, as well as adding decades to a conflict where the French held a great advantage in both resources and manpower.

Range also played a part in the U.S. War of Independence. Morgan’s Riflemen (famous for their long-range rifles) played their part in securing victory at important battles like Saratoga.

A computer-rendered illustration of what a future Ramjet missile could look like. Nammo hopes to have missiles ready in a few years – the motor testing is already well underway (Illustration: Nammo)

 

«There’s a race going on»

Longbows are however a thing of the past. But Nammo artillery and munitions expert Thomas Danbolt believes range is still of great importance to contemporary weapons, like artillery.

«Range is important. If you can shoot much farther than your opponent, counter-battery fire can simply be disregarded. Your own artillery will be safe, while at the same time you can strike enemy positions with impunity. I think we should not underestimate the consequences of having a range advantage», says Thomas Danbolt, Nammo’s Vice President Large Caliber Ammunition.

Danbolt thinks major nation-states have seen the importance of this, and are now scrambling to improve their defenses. His colleague, Frank Møller, has been part of designing rocket motors for missiles for decades. He sees a big change in that field as well.

«I think there’s a race going on internationally. Propulsion technology has improved. Cruise missiles are getting longer ranges, better sensors, improved accuracy, and the cost has gone down. But a reaction is coming: armed forces everywhere are scrambling to improve their missile defenses», says Frank Møller, Nammo’s VP of Strategy and Business Development (Aerospace Propulsion).

Nammo has already completed more than 150 motor tests. Testing so far has been very successful, showing ramjet motors can work in real life (Photo: Nammo)

 

150 km artillery range

As demand for longer range options increases, ramjet technology has been advancing steadily. It has now come to a point where it can has several new potential applications – both in missiles and artillery.

Nammo already has a long history of producing high-performing artillery ammunition. Now, it once again wants to be at the forefront, developing a new generation of shells covering all range requirements.

Nammo’s most ambitious project to date has been a Ramjet-powered, guided artillery shell with a range of up to 150 km/93 miles, now the subject of a development partnership with Boeing’s Phantom Works. The new design is expected to see its first live-fire tests in 2020.

«In practice, this is a mix of a missile and an artillery shell. We are talking about a range that is five to eight times greater than conventional artillery. With the guidance system, we believe we can consistently hit an area as small as the center of a football field. And even though the payload is somewhat smaller, the destructive force will likely be greater because of the accuracy», Danbolt says.

The Ramjet shell can be fired from every modern 155-mm L52 artillery gun – a trait it shares with all of Nammo’s other long-range shells.

 

The Ramjet revolution

Ramjets are also very well suited for missiles. In a conventional rocket motor, oxygen accounts for 80 percent of the fuel weight. But a Ramjet instead uses oxygen from the outside air. As a consequence, oxygen can be replaced with fuel, increasing the capacity four or five times. Erland Ørbekk, Nammo’s VP of Technology for Aerospace Propulsion, explains that the advantages are great if a missile can reach high enough speeds.

«In a traditional air breathing motor, you need a compressor, a combustion chamber and a turbine. But in a Ramjet, the oxygen pressure and temperature will be high enough just from reaching a high enough speed (roughly Mach 2.5). A Ramjet missile can have a burn time of up to 300 seconds (5 minutes), and can be throttled up and down, or even turned on and off», Ørbekk says.

What operational advantages can we expect?

«A Ramjet-powered missile will be superior to a conventional missile in all possible ways. Ground-based Ramjet missiles will be able to take out high-altitude targets. And if fired from aircraft, they will be effective against high-speed and highly maneuverable fighter jets at much greater distances than today. We believe they could even be effective against some of the new high-speed missiles being introduced outside NATO. If you have a good enough sensor system on the ground, it will be possible for Ramjet-powered missiles to intercept them».

 

Ready in a few years

Ramjet-powered artillery and missiles could be ready sooner than you think. Nammo has already completed more than 150 successful tests of its ramjet engines. While artillery ramjets could reach up to 150 km/93 miles, some air-to-air missiles could hit targets from an even more impressive 500 km/310 miles distance.

Frank Møller is sure we will see products on the market within a few years.

«Long-range Ramjet artillery will likely be on the market within two to four years. For missiles, it will take a bit longer, but we are confident that the technology is ready. What we are working on now is more focused on the practical applications and technical solutions».

Are you sure of that? Are you sure the technology will work?

«Absolutely. And it will be a momentous change».

The Bullet That Swims

While traditional ammunition is either stopped or deflected when it hits water, Nammo’s 30-mm Swimmer (APFSDS-T MK 258 Mod 1) swims straight through water, thanks to a groundbreaking design on the supercavitating projectile developed in cooperation with the U.S. Navy. In this article, first published in the 2018 Nammo BulletIN, design engineer Jan Hasslid discusses the implications of this new technology.

The Bullet That Swims Through Water
The Bullet That Swims Through Water

25 years ago, Norway became one of the first European countries to acquire an infantry fighting vehicle with a 30-mm × 173 gun, the CV9030N. At the same time, Raufoss Technology AS, now a part of Nammo, negotiated a contract with the Norwegian Army to develop a new generation of 30-mm ammunition. Today, with 30-mm guns becoming more prominent than ever, the experience gained through this early work has allowed Nammo, through its Strategic Alliance Agreement (SAA) with General Dynamics Ordnance and Tactical Systems (GD-OTS), to become one of the main providers of 30-mm ammunition for the U.S. Armed Forces. Following the recent signature of agreements with the U.S. Army and the U.S. Navy, both services are now adopting Nammo’s 30-mm APFSDS-T MK 258 Mod 1, or «Swimmer», for use from a multitude of platforms, including the U.S. Army’s latest addition, the Stryker variant known as «Dragoon».

Ammunition used by vehicles generally falls into three categories – armor piercing (APFSDS), for use against other vehicles; High Explosive Incendiary (HEI), for use against lighter targets and aircraft and Target Practice (TP) rounds, that allow cost-effective training.

Nammo today offers ten different types of 30-mm × 173 ammunition across all three categories, ranging from plastic blank and reduced range anti-armor to multipurpose and explosive rounds, as well as dedicated kinetic energy penetrators. The Swimmer round falls into the category of sub-caliber kinetic energy penetrators. These can most easily be described as arrows made out of very heavy materials that use the force of the impact rather than explosives to punch through armor. Traveling at speeds of more than 1 km per second, the energy generated by the impact melts the armor of the vehicle into a fluid and the arrow «swims» through the armored side of the vehicle. In the case of the Swimmer, the force of the arrow is sufficient to defeat anything except main battle tanks.

The U.S. Army's Stryker Dragoon will be using the Swimmer, as it has excellent capabilities against land vehicles as well as naval targets (U.S. Army photo by Sergeant John Onuoha)
The U.S. Army’s Stryker Dragoon will be using the Swimmer, as it has excellent capabilities against land vehicles as well as naval targets (U.S. Army photo by Sergeant John Onuoha)

Nammo’s penetrators, both for vehicles and other types of armor piercing ammunition, are made out of a super tough tungsten alloy, also known as wolfram. More than two times as heavy as steel, it has the second highest melting point of any element, making it ideal for use in armor piercing ammunition. For some ammunition types, including the 25-mm APEX for the F-35, tungsten is mixed with carbon, creating what is known as tungsten carbide. This makes the penetrators harder, but also more brittle, allowing them to fragment once they have penetrated the armor, causing added damage inside the target.

What makes the Swimmer unique, however, is the combination of powerful armor penetration and its ability to swim straight through water. This effect has until now been considered impossible to achieve by ammunition fired from air through water. As demonstrated by a number of popular science TV programs, traditional ammunition is either stopped or deflected when it hits water. In a worst-case scenario, a projectile could hit the surface, bounce off and hit something else. Thanks to the design effort for the kinetic energy penetrator originally developed for the Norwegian Army, and perfected by Nammo in combination with U.S. Navy supercavitation concepts, the Swimmer avoids the ricochet in water problem through the use of a supercavitation nose design. This means that the projectile creates a bubble of steam around itself big enough to pass through, substantially reducing the friction that stops traditional ammunition. This enables the Swimmer to be used in defense of either ships or coastal areas against submerged and surface mines, small underwater vehicles, torpedoes and even small fast attack crafts that might be concealed by waves. This is valuable not only for naval vessels, but also for land vehicles defending harbors, bridges or other key locations.

Going forward, Nammo expects that most armored vehicles armed with medium caliber guns such as the 30-mm will carry one armor piercing round, and one multirole round capable of acting as either a traditional high-explosive or an airburst round. With the Swimmer established as a leading armor piercing round, Nammo is now turning its attention towards developing a new type of programmable 30-mm ammunition that can be used against the kind of targets where the Swimmer is less effective. Based on the same technology as the 40-mm grenades that have been demonstrated against drones, this would allow fighting vehicles to program their ammunition to explode either in the air, or at a specific point inside a target. This would allow future combat vehicles to address the full range with only two ammunition types, and hence be ready for any mission, at any time.

Testing the Swimmer, Nammo’s Supercavitating Ammunition