Upgrading supersonic track

Crews work on supersonic track.

There’s lots of super-sophisticated reach going on at the Naval Air Weapons Station in China Lake, Calif. But when the 50-year-old Supersonic Naval Ordnance Research Track, known as SNORT, was due for its first upgrade and preventive maintenance program, it called for some plain and fancy m/w skills.

According to Rocketeer II, the official newspaper of the facility, SNORT is a test track where items are brought to study effects on them when they are subject to acceleration velocities and air flow at the design conditions. The four-mile test track currently consists of 432 50-foot sections of H-shaped steel crane rail, which forms the actual track, in a complex system that sinks three feet of concrete and steel into the earth, while allowing for up to 10 feet of horizontal expansion of the steel track in the summer heat. Aligned to within 60/1,000 of an inch, the track can test items using speeds up to Mach 6, although normal usage is at Mach 4 (about 3,000 mph) and below.

A significant part of the $2.4-million upgrading involves welding the track. When the track was built, technology wasn’t available to weld the sections together easily and precisely, but the designers planned for the future. The welding will make the track easier to align with greater precision, which will make it safer, stronger and better able to handle faster tests than before, according to Craig McKenzie, SNORT branch head.

Work on the project began in November 2006 with eight SNORT employees and about 10 from SA-TECH and Jacobs Engineering going down the track and disassembling all the nuts, bolts and anchors that hold the rails in place. These hadn’t been replaced in more than 50 years. Crews then sorted the various parts as reusable or recyclable, with the reusable parts being re-machined. The station machine shops made new parts, often with quick turnaround times in order to keep the work moving.

The new or rehabilitated parts are currently being installed at the rate of about 400 feet of track per day.

McKenzie praised the original design work on the track, noting that this upgrade is using all the original engineering work, which is still valid. New, improved materials such as asphalt that contains rubber to absorb more of the vibration and a heavy-duty marine-grade grease to sink the anchors into are being used to further improve performance and longevity of the track.

The welding work was contracted to Delta Railroad Construction, Inc., which brought 120 employees to perform the electric flash butt welding portion of the upgrade. Welding work was scheduled for six to eight weeks. The welding crew finishes about 700 feet of track per day, with crews working 60 hours per week.

The two ribbons of 171-pound rail are stretched and tensioned equivalent to the maximum temperature anticipated for the rail.

Some special effort is required to ensure the proper tension is re-achieved if the track is severed in an unfortunate testing event. However, it should not exceed the effort required to rebuild the track in its prior jointed state.

After the welding is complete, the precision alignment of the track begins. The high speeds of the tests dictate tight tolerances for the track alignment, and SNORT crews use a special laser to align the rails to within 60/1,000 of an inch. During this phase, three teams work to unscrew and adjust 25,000 alignment points. McKenzie estimates this will take 3.5 months.

When the project is complete, the SNORT team will go back to testing. From complex multiple- target penetration using live, high-explosive-filled warheads to missiles and rockets guidance and fusing, aircrew ejection systems, free-flight terminal ballistics, electronic warfare and counter measures and vehicle and barrier testing, SNORT has supported more than 750 programs during its tenure.

Thanks to some skilled m/w work, the facility will go on serving the nation’s military for years to come.

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