Defense

September 13, 2013

At times, even munitions must shake, rattle and roll

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Cassandra Mainiero and Edward Lopez
Pacatinny Arsenal, N.J.

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Providing the war fighter with a variety of weapons and munitions such as a mortars and mines involves much more than whether they will function at a basic level.

Will they perform as designed at various altitudes, or at extremes of hot and cold temperatures? Will they remain intact if transported over rough terrain that produces constant shaking and jolts? Will various levels of humidity affect their performance? Will the munitions still function if accidentally dropped from various heights?

Finding the answers to these questions is the realm of personnel at Picatinny Arsenal who work at the Environmental Test Lab, which is part of the Quality Engineering and System Assurance Directorate.

The lab is spread out among a variety of buildings that specialize in certain types of environmental tests, and includes a 120-foot drop tower. Items tested include fuses, mines, artillery rounds, fire control systems, telemetry, mortars, howitzers, small arms, pyrotechnics and packaging.
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The testing lab aims to ensure reliability and to assure safe and functional items that can survive a variety of conditions throughout their life cycle.

Development engineers, test engineers and technicians who work at the lab tackle such questions as: Can the item handle the temperature conditions it’s intended for? What type of packaging and storage will be used for this item? Will the product remain intact when exposed to high altitude versus a lower altitude?
“We give them (the customer) an indication of whether the item is suitable for further development or not,” explained Mike Menegus, a lab engineer.

The organization also tackles a range of environmental concerns through a wide variety of tests, including vibration testing, temperature shock, jolt and jumble testing, altitude (low pressure) testing, as well as several others.
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Jolt testing, for example, tests to ensure that fuses and safety devices don’t fall apart or become unsafe to handle after they’re hit with mechanical shock and vibration. The test involves 1,750 repetitive shocks to an item in three different orientations, such as sending a shock and vibration from the side of a fuse versus from above.

A jumble test determines if a fuse would remain intact if it were loose in its container. It functions like a clothes dryer as the item tumbles around a large wood or plastic box and the machine rotates at 30 rpm, sending the item from one corner to another.

Soft-catch air guns are also popular and used to test fuses and any item that can be launched, such as from a gun or missile launcher. The test simulates what happens inside a gun when the propellant is burning and the projectile is accelerating down the tube.

The Environmental Lab has three different sizes of air guns, a two-inch, a five-inch, and a 155 millimeter.

“Much of the munitions today are smart munitions and use a lot of electronics,” said Alexander Plotkin, lead test engineer. “When you shoot a projectile, you have to propel it very fast, so that when it exits the barrel it’s still functional and did not break inside of the gun barrel. So, any item like that can be tested here, without going out into the field.”

Finding the best test

Still, an item is rarely tested in just one way.

Instead, an item may often be put through a sequence of different tests, which can take from one day to years, depending on the item and its intended use.
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The number of testing samples can also range anywhere from small to large group sizes, such as six small armament samples versus hundreds.

When customers seek testing from the lab, they typically specify what type of tests they want the item to undergo. When customers don’t have a definite test plan, lab personnel ask about the customers’ goals to help narrow down the possibilities.

As a result, testing may be a combination of input from both lab personnel and customers.

“It’s all agreed upon before we start the tests,” said Mike Menegus. “Even when they [customers] have a test plan, we sometimes look at the plan and say ‘No, that’s not quite right. We’d be better trying this test instead,’ or we change the sequence of tests.”

However, temperature shock testing is often a starting point.

Temperature shock uses a climactic test chamber, a large box divided into two sides, to see how a device will function when shifted between two extremes, hot and cold. When an item fails the temperature shock tests, though, the likelihood that it will withstand any other tests is slim, Menegus and Plotkin said.

“Sometimes when we test items, they don’t function in the way they’re intended to function,” said Plotkin.

“However, we don’t fix the problems; we find the problems and provide test data and recommendations to design engineers to resolve deficiencies.”

New solar testing

The Environmental Lab was built in the mid 1960s, specifically to handle small quantities of energetic items, such as explosives and loaded materials, as well as perform environmental testing.

While 90 percent of its work is for customers in Picatinny organizations, the lab performs testing for other military branches (the Army, Air Force, and the Navy) as well as for private industries. The lab says it has competitive pricing, can save on travel costs associated with testing and can modify testing quickly.

Moreover, the lab’s air guns offer a form of testing that many other facilities cannot provide.

The directorate under which the lab operates is part of the Armament Research, Development and Engineering Center, which in turn is part of the U.S. Army Research, Development and Engineering Command.

Recently, testing for the effects of solar radiation was added at the lab.

Such testing helps to evaluate how a composite ages when it is exposed to different amounts and types of solar energy, whether it’s in dry desert or a subtropical climate.

“Not too many people are aware we have it,” said Alex Plotkin. “But it’s brand new and we’re very excited.”




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