Cooking up ammunition

If you were a deer or a boar you might wander through a dense but well-kept wood in the middle of France and munch on some grass on the strange, rather steep hillocks dotted around here and there, stepping unhindered underneath silvery pipes, pleased that the tidy roads are so empty.

But if you are a human you will not be able to wander unaccompanied and will need to pass through several layers of strict security, having switched off all your electronic devices for this is no ordinary wood. This is the site, classified Seveso 2, at La Chapelle Sainte Ursin where the Nexter Ammunition Group makes ammunition from 20mm guns to the 155mm LU211 long range and also makes the explosives sections of torpedoes and missiles for MBDA and the French naval systems group DCNS.

Part of the production unit at the Nexter plant in La Chapelle Sainte Ursin

Part of the production unit at the Nexter plant in La Chapelle Sainte Ursin

As we were taken carefully around the site this morning (16th December) we were struck by certain things. First the sweet but acrid smell (it was TNT we learned) in some of the production workshops and the raw explosive itself that comes in the shape of flakes or a mixture (it was Compo B apparently) that looked for all the world like crumble pastry waiting to be put atop some apples and popped into the oven! Then the production workshops themselves, made out of 70cm thick reinforced concrete with one weak wall that faces those funny hills so that should something explode the blast would take the easiest path through the weak wall and then be deflated upwards by the hill.

If you thought that making a shell consisted in stuffing some explosive into a case, then think again. Didier Mery, head of the production engineering department, talked to us about how the casting for high explosive shells is made explaining that there are three production lines in the pyrotechnical section with 25 operators for each product line who over the year can fill between 35 to 40,000 shells. Every single one is X-rayed at the end of the production line and the image is then checked by humans to ensure there are no air holes or cracks. Mery explained that a shell has to withstand pressure of 18,000Gs when it is fired “which is what makes it particular.”

There are 38 different steps to making a meduim calibre ammunition case tube to take it from the solid steel rod that arrives at the plant and then shaping it and stretching it, covering it with soap and other products, checking and double-checking at every stage, before it undergoes eight separate surface treatments. The reason being that if the case is not exactly the right shape, particularly for ammunition that will be shot by the Rafale fighter aircraft or Tiger helicopter, the case could get caught up in the engine and then “the pilot will only have one option: his parachute,” as one of the product line managers remarked. For this procedure the plant is currently in the midst of shifting from a traditional to a lean manufacturing method that should be completed by mid-2016. For the moment both systems are working side by side and the difference is remarkable. In the lean, the machines are brand-new and well protected, everything is colour coded, there are clear marks on the marble floor and it is quiet. On the traditional side, strange potions are bubbling away in machines that are ridden by rust in a noisy, stuffy atmosphere. The new €2m fully automatic, 50m long machine for surface treatment should be able to treat one million cases a year.

The plant also contains Europe’s largest iso-static processing unit (read on!), bizarrely made out of an old ship’s gun barrel. The explosive material is moulded inside silicone moulds (similar to the ones you might have in your kitchen) and this is then set in the unit that is sunk 6m under the floor and is surrounded by oil. The whole thing is then covered with a 33-ton “lid” to contain any possible accident and everyone leaves. Meanwhile the incompressible oil is put under pressure thanks to hydraulic pumps and thus squeezes and compacts the explosive applying equal pressure at all points of the mould. The idea? When the shell explodes the explosion will be much more powerful.

I did find myself thinking about whether the employees always remember what the finality of their work is or are they so concentrated on the microcosm of ensuring these highly complex robots and other machines work smoothly that they forget what the end product is for.