By Carolanne Sacry Feiste

China Lake, Calif.--The Supersonic Naval Ordnance Research Track, commonly known as SNORT, at NAVAIR Weapons Division tests hard-target-penetration warheads capable of penetrating deep buried bunkers with thick walls of reinforced concrete. It requires the capability to move the test item at very high speeds—like a missile being fired from a jet.

The weapons under test are currently not available to the Fleet.

To enhance high speed testing track capabilities, NAVAIR China Lake has started a SNORT track-alignment project. The goal is to reduce vibration shocks and loads sleds encounter as the item moves along the track at very high speeds. A rough ride, inducing higher g-forces from vertical and lateral accelerations into the sled, can potentially damage the test item and/or the components.

Track alignment problems occur, every 50 feet, where the rail ends meet each other. Not actually aligned to some theoretical curve, the track is surveyed at adjustment points. A seven-point-cubic smoothing function is used at each adjustment point. With a smoother track, the sled experiences less vertical and lateral acceleration—extremely important for these high velocity tests.

Most recently, SNORT conducted a weapon effects test (WET) to check the ballistic profile of the newly aligned track. It helped to gain a better understanding of the vibration and thermal environment. The data, collected by a velocity measurement system (VMS), will be used in the future design and planning.

Induction coils, placed every 100 feet along the outside-edge of the track, receive a pulse of electric current as the sled passed along the track (created by magnets on the sled). Velocity was determined based on the time of arrival of the induced pulses. The VMS also helped determine speeds from zero - to peak speed- to stopping. In the recent test, the sled traveled 2,510 feet per second (fps)—about Mach 2.3.

The intended speed for a test is determined by engineers who use the complexities of weight, rocket motor thrust, and atmospheric conditions. It is also necessary to prepare the test item for the temperatures to which it will be subjected. As the rate of airflow increased across the test item, temperatures dramatically increased. The WET sled reached temperatures ranging between 500 and 600°F at Mach 2.3.

Modifying the design to meet specifications for new tests, the SNORT team can often reuse previously built sleds. The sled used in the WET test was a modified high-speed sled, designed and first used in 1986.

The WET results illustrated that the SNORT tests will continue to go faster and smoother, due to the track alignment. The people involved in test planning and execution expect to achieve Mach 4 soon.