Military

Tests of solid fuel ramjet engine to extend artillery range over 100 km

Tests of solid fuel ramjet eng...
A ground test of the Solid Fuel Ramjet engine being developed for the US Army
A ground test of the Solid Fuel Ramjet engine being developed for the US Army
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A ground test of the Solid Fuel Ramjet engine being developed for the US Army
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A ground test of the Solid Fuel Ramjet engine being developed for the US Army

Northrop Grumman has carried out successful ground tests of a Solid Fuel RamJet (SFRJ) tactical engine that the company is developing for the US Army. Part of the Army's XM1155 Extended-Range Artillery Projectile (ERAP) program, the engine is designed to boost the effective range of a 155 mm artillery shell to over 62 miles (100 km).

Even in an age of missile-firing drones and laser weapons, artillery is still the cornerstone of fire support for infantry and other ground forces. The problem is that artillery pieces have a relatively short effective range. Worse, the shells that they fire can only follow a ballistic trajectory, which means that once the projectile leaves the gun muzzle, there's no way of altering its course, so it isn't very effective against a target that's actively avoiding the fall of shot.

There are a number of ways of overcoming this being explored and one of the more promising is the SFRJ. A ramjet is also known as a flying stovepipe because it is basically an empty tube into which fuel is sprayed. That may seem pointless, but when that tube is moving at high speed, especially in the supersonic range, its forward motion compresses the incoming air before burning the fuel, producing thrust without the need for moving parts.

A solid-fuel ramjet is a version that, as the name implies, uses a solid fuel lining the engine instead of injecting liquid jet fuel. The same compression and combustion occurs, producing thrust. It's technology that's being developed for a number of uses, including boosting hypersonic missiles and enhancing the performance of artillery.

Firing a SFRJ-equipped shell accelerates the engine to its operational velocity so it can ignite. Once it is running, it not only increases the range of the projectile, it also changes its flight characteristics because the engine keeps the shell from slowing down due to air resistance. In addition, it allows the shell to be steered in flight, making it more precise and capable of hitting a moving target.

The Phase One XM1155 ERAP ground tests included the firing of multiple rounds and determined that the SFRJ's survivability and the performance met predictions. The eventual goal is to produce a shell that can be used against stationary and moving high-level targets in all weather conditions and any terrain.

"Successful completion of the rigorous tests of the Solid Fuel Ramjet demonstrates maturation of the technology to survive the very challenging gun-launch environment and significantly extend the range of the US military’s current field artillery with a high level of confidence," says Pat Nolan, vice president, missile products, Northrop Grumman.

Source: Northrop Grumman

7 comments
Brian M
Probably better described as a gun launched missile! But clever idea, unless you are on the receiving end of course!
paul314
And the cost of these things compared to ordinary artillery? (Let alone to avoiding wars in the first place)
VincentWolf
Imagine a war in the future when your shot at with artillery and it never misses. Makes for a very short war.
Nelson Hyde Chick
War, the only half decent population control device at our disposal. As humanity grows and resources get thinner and thinner war is inevitable. For instance, with both Pakistan's and India's population growing and India controlling the water going to Pakistan, which they will have to hold back to grow the food they need for their population, war is inevitable between these two nuclear powers. If humanity makes it unravaged by environmental collapse caused by war by 2100 it will be a miracle beyond belief.
bahbah
The ram jet is the easy part. The tricky parts are the electronics and battery that can tolerate 20,000 g, also where to put the explosives (the shell is basically a tube), the hollow charge required for tank armour cannot be used, etc.
ljaques
62 mile range for artillery? Totally cool.
jerryd
These are not new but guidance systems are so much better making them useful now.
Making one into a ramjet is fairly easy and increases range 3x vs normal solid rockets. On Ram jets need certain shape intakes, inside the pipe to work best.
And since the 155mm cannon is common across the services the navy is likely the best use of it.
And it'll only be used in a guided version as the only way to hit a target that far away.