June 3, 2013
When Industrial Laser Systems was asked to fabricate a tubular frame for a military vehicle, it rose to the challenge to cut, makes some holes, bend, and swage the tube ends. The result is a tubular frame that is affixed to the outside of patrol vehicles; combined with Kevlar® netting, the system prevents explosive projectiles from hitting the vehicle, with great success.
Bomber aircraft, nuclear-powered submarines, and aircraft carriers are among the most awe-inspiring and technologically advanced weapons delivery systems, but a weapon doesn’t have to be overwhelming to be deadly. Small, portable devices that combine lethal firepower with the ability to get close to targets undetected are just as threatening. Few are as fearsome as the rocket-propelled grenade (RPG). Initially developed during World War II as an anti-tank weapon, it is fired from a hand-held launcher, powered by an internal rocket motor, and stabilized by fins that deploy in flight.
They aren’t used just against tanks, but work against any sort of vehicle. Mine-resistant, ambush-protected (MRAP) vehicles are armored to withstand this threat, but armor has drawbacks. It increases the cost, weight, and fuel consumption and makes the vehicle slower and top-heavy, increasing the likelihood of a rollover.
“Some of the original MRAP vehicles weigh 50,000 to 60,000 lbs. They are huge,” said Sloan MacKarvich, president of Industrial Laser Solutions, Atlanta, a fabricator that does some defense work. Using these in a region with paved roads and fairly flat topography, like much of Iraq, is one thing; using them in a mountainous region with poor roads, which describes most of Afghanistan, is something else altogether, MacKarvich explained. Even the sand in Afghanistan is a bigger hazard than the sand found in other regions.
“The sand is like quicksand,” he said. “They call it space dust.” A big vehicle would sink quickly, so the military needed lighter vehicles and something other than conventional armor to protect them.
One such system, developed by QinetiQ North America and named Q-Net™, traps the RPG in flight, preventing it from detonating. The system weighs little because it’s made from high-strength-to-weight materials—the netting is Kevlar®, and the frame is made from steel tube.
Industrial Laser Solutions cuts the tube to length, puts holes in it, bends it, and swages the ends. Much of the project involves run-of-the-mill tube bending, MacKarvich said, but the holes presented an interesting challenge.
“We got a little creative for this project,” he said. “We already were making some weldments for a similar project, so we were familiar with the system. Not only are the tubes rotary draw-bent, they are also swaged so that one end fits into the next. All the connection points have holes in them because they are pinned together, and the hole locations had to be held within 0.020 inch. This prevents the pins from clattering when the vehicle is going down the road.”
A competing supplier had the contract, but it couldn’t keep up with the demand. It machined the holes after the tube was swaged, but ILS figured it could make them faster by laser cutting the holes first, then tweaking the swaging process so it didn’t deform the hole as the tube end expanded.
“We eliminated postprocess machining and end trimming, which really cut the time it takes to produce them,” MacKarvich said.
When an RPG strikes a stationary object, the impact depresses a plunger at the front of the weapon that ignites an internal fuse. The Q-Net system doesn’t stop the RPG; it is designed to disable it. It relies on a network of hard, sharp, pointed devices that damage the RPG.
“Features of the net actually tear into the RPG and break up the internal components,” said Don Steinman, vice president of technology solutions for QinetiQ North America. The net short-circuits the fuse, rendering the charge useless, Steinman explained.
The system can be installed in just a few hours. It bolts onto the hard points that military vehicles have for this sort of purpose, such as an external ammunition rack or water can holder, Steinman said. Mindful of soldiers’ needs, QinetiQ North America designed the Q-Net so it can be used in addition to other accessories, not instead of them.
How well does the netting work? According to “New net armor proves its worth,” an article posted at www.army.mil, the system was combat-tested in an incident shortly after being deployed in Ghazni Province in Afghanistan. Vehicles involved in this incident took three direct hits, and the netting snagged all of the RPGs, sparing all of the soldiers’ lives.
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