Fortune:
When a 240-foot unmanned U.S. Army blimp broke free of its moorings and rampaged across two states in October, it looked like the embarrassing incident might spell the end of the troubled $2.7 billion JLENS program. But the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS) will fly again, the Department of Defense has confirmed, breathing new life—and new money—into the deflated program.
Secretary of Defense Ash Carter has given the Army the go-ahead to put two JLENS aircraft back in the air over Aberdeen Proving Ground northeast of Baltimore, where prior to October’s mishap, the program was conducting an operational exercise to demonstrate the system’s performance. The JLENS aircraft have been grounded ever since.
A recently-completed review of that October incident found that a series of errors led one of the aerostats to break free of its mooring and drag its heavy kevlar tether 160 miles across Maryland and Pennsylvania, damaging property, severing power lines, and leaving some 30,000 homes without electricity. Among those errors: Someone forgot to put batteries in an automatic deflator mechanism designed to activate in exactly this kind of situation.
“Design, human, and procedural issues all contributed to the incident,” said Maj. Beth Smith, a spokeswoman for the North American Aerospace Defense Command (NORAD), which launched the exercise last year.
Built by defense contractor Raytheon, JLENS consists of two aerostats carrying radars designed to track cruise missiles, drones, and other potential threats over wide areas. From a vantage point up to 10,000 feet overhead those radars can see for 340 miles in any direction, according to Raytheon, offering 360-degree, around-the-clock threat monitoring that land and sea-based radars simply can’t match. Each 7,000-pound aerostat is anchored to the ground by kevlar tethers more than an inch thick.
The operational exercise at Aberdeen is designed to demonstrate that the system could help defend the capitol region from airborne threats like sea-launched cruise missiles. But when the wind picked up one day last October, a series of things began to go wrong. First a device meant to measure air pressure within the blimp malfunctioned. Ordinarily, the aerostat’s onboard systems would respond to increasing winds by boosting the pressure within the aircraft. Instead, pressure within the aircraft began falling.
This caused the aircraft to turn perpendicular to the prevailing wind at a time when gusts were reaching nearly 70 miles per hour. The aerostats tail fins began to warp under the strain from the winds, increasing the aircraft’s instability. This in turn put extreme stresses on the tether, which eventually failed.
Still, all of this should’ve been mitigated by a safety device that automatically deflates the aerostat should its tether break. That device requires power, however, and batteries to power it had not been installed. Instead of deflating within a couple of miles of its original mooring, the aerostat rampaged across two states, coming to rest eventually in some trees in southeastern Pennsylvania…
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