On board the USS Nimitz, Creare tests the Slot Measurement Assembly device.

The catapult that launches a naval airplane from the deck of an aircraft carrier accelerates a 48,000-pound craft to 165 mph in two seconds. The 4G driving force is exerted by pistons moving inside a cylinder under the influence of high-pressure steam. A narrow axial gap in the top of the cylinder wall allows the pistons to be attached to a sliding shuttle, which connects to a T-bar on the plane’s nose gear during the launch.

One of the critical safety issues for the catapult system is maintaining the size of the gap through which the piston attaches to the shuttle. The small gap runs the entire 350-foot length of the catapult and tends to widen as a result of normal operating stresses. If the gap width varies beyond accepted tolerances, the takeoff speeds are negatively impacted, increasing the peril for all involved.

There are four catapults on most modern carriers, and providing regular testing on all widths for an aircraft carrier fleet that spans the globe has been a challenge for the Navy. Manual methods require disassembly of the catapult and deck plating, a prohibitively time-consuming procedure. An automated measuring unit exists, but it has become unreliable, cumbersome, and outdated.

For the Naval Air Systems Command at Lakehurst, NJ, Creare engineers used next-generation technologies to design a new system for measuring the cylinder gap. It uses an autonomous robotic device that independently moves along the catapult gap and takes essential readings. The measurements are wirelessly transmitted to a ruggedized laptop computer operated by naval personnel. In addition, a camera embedded in the system allows the operator to visually inspect the gap and nearby components.

The system primarily relies on a robotic Slot Measurement Assembly (SMA) device. It uses precise gap width sensors that are highly accurate and which operate reliably under a variety of harsh shipboard environmental conditions. The SMA weighs approximately 20 pounds, and the entire system fits into a carry-on suitcase.

The system uses commercial-off-the-shelf (COTS) technology, including a “586-engine” CPU programmed in C/C++, facilitating our vision of an open source solution. By using a wireless RF data and control link we reduced the power requirements, making the measurement system self-contained and battery-operated. A user-friendly graphical interface enables intuitive system operation and data management. Our system reduces set-up time, delivers more accurate data, and decreases inspection and maintenance costs. The U.S. Navy has estimated that this system reduces labor costs by 94%.

Two first-generation prototypes delivered to the Navy were tested and over 90 catapult readings were obtained for multiple aircraft carriers. Creare recently delivered eight additional units which have now been used successfully all over the world on every active aircraft carrier in the U.S. Navy fleet. To date, not a single failure of any kind has been reported. It has been an honor for us to work with the dedicated safety personnel on the aircraft carriers and to make a contribution to such a critical area of need for the Navy.

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