Today�s mine detectors survive some tough treatment long before they ever reach the battlefields.
The mine detector, unique in its capability to spot the small, high-tech antipersonnel mines littering the landscapes in Afghanistan and Iraq, combines ground-penetrating radar and metal-detection technology to locate both metal and plastic mines lurking beneath battlefield surfaces. Our company was called on because of its experience to provide severe environmental stress testing of electronic devices to determine mean time between failures, a measurement of how long a device can be expected to operate under extreme conditions before failing.
Working closely with the military and CyTerra, the detector�s manufacturer, we created an environmental test profile of MIL-STD-810 tests that included stresses from temperature, vibration, sand, dust, altitude, shock, electromagnetic interference (EMI), and solar radiation. The tests simulate the extreme range of conditions that a device may be subjected to in mission situations worldwide. In an unusual move, we also performed human testing, or reliability and maintainability (RAM) tests, normally completed by the military.
Temperature
Because landmine detectors frequently are exposed to freezing temperatures during high-altitude flights followed by exposure to intense desert heat upon landing, high and low operating and storage temperatures were determined. A 10′ � 10′ � 10′ walk-in thermal chamber was used, and thermocouples were attached to critical components of the mine detector.
The detector was exposed to temperatures ranging from +135�C to -50�C for periods ranging from 24 to 240 hours. The detector performed without soft or hard failures, proving to be more than robust when exposed to thermal extremes.
Altitude
An airtight altitude chamber was used to simulate high-altitude flights. The mine detector was exposed to an air-pressure equivalent to 25,000 feet, typical of the pressure experienced inside the cargo hold of a military transport plane. The pressure was reduced for 12 hours, after which it was returned to a sea-level atmosphere, and the unit was tested to determine operability. No failures were experienced.
The unit was turned off and returned to the chamber. It then was exposed to an atmosphere equivalent of 10,000 feet and remotely operated from inside the chamber to simulate the high-altitude operation required in a mountainous region such as the Himalayas. No failures were experienced.
Solar Radiation
With intense desert sun always a concern in countries such as Iraq and Afghanistan, solar radiation tests were performed. The mine detector was placed inside a radiation chamber consisting of a walk-in room equipped with racks of high-intensity lamps. The lamps at 1,120 W/m2 were programmed to repeat an on/off cycle of 18 hours on and six hours off, simulating long days and short nights, for a period of 54 days at temperatures ranging to +71�C.
An IC in the detector�s computer processor failed during the test period. The chip, a commercial component, was replaced with a more robust version, and no subsequent failures were noted.
Sand and Dust
We simulated the effect of intense desert storms through creative use of a wind chamber. The detector was placed inside the wind chamber and exposed to 60-mph wind blasts at a temperature of 65�C over six faces for six hours each. During each exposure, sand was fed through the fan, simulating the effect of a desert sand storm. The detector, painted with a hardened chemical-agent resistant coating, experienced no failures during this virtual sandblasting.
Humidity
A temperature and humidity chamber was used to determine the detector�s operability in tropical climates. The detector was exposed to continual 95% relative humidity at 65�C for 240 hours. At the end of the exposure, the unit was turned on and found to operate properly.
Salt Atmosphere
Further tests were conducted to determine susceptibility to corrosion during exposure to salty tropical environments. The detector was placed inside a specially designed salt-atmosphere chamber and misted with a 5% saline solution at 95�F for 96 hours. No failures were noted.
Drop Shock
Drop shocks were performed with the mine detector contained in a military backpack to simulate potential field-transport conditions. The unit was dropped 26 times onto a concrete floor from a height of 36 inches and then examined for damage.
The unit remained operable but suffered a broken metal mounting bracket used to attach the electronic control interface to the detector framework. No design changes were required for the mine detector. A determination was made to redesign future backpacks to include additional padding to protect the connection.
Transportation Shock
More vigorous transportation shock tests were conducted using an LDS V9 Shaker System. The detector was subjected to brief pulses of 20g force on each of its six faces. Each 20-g pulse lasted for 11 ms for a total of 18 bursts or pulses. No failures were noted.
Loose Cargo Vibration
A simulated pickup truck bed, attached to an eccentric cam operating at high speed, provided random bumps to the mine detector for one hour, equivalent to 1,000 miles of normal military travel. One failure was noted. A clip that holds a cable to the detector frame assembly broke. The unit remained operable.
Rain
Tropical rainfall was simulated by exposing the mine detector to 50-mph winds and water spray from multiple nozzles at five gallons per minute for 30 minutes. No failures were noted.
EMI
Because it is imperative that the mine detector does not emit radiation that interferes with the operation of other equipment or cause a mine or other explosive to detonate, the unit was thoroughly tested for EMI transmission and reception. Various conducted and emitted EMI profiles were utilized. No failures were noted.
RAM
During the RAM test, the detector was subjected to 1,000 hours of packing and unpacking, assembly, and operation by our personnel in an outdoor environment. The RAM test exercised the battery and all components of the detector in real-life, real-time scenarios. No failures were noted, and the unit was determined to be adequate for mission use.
Conclusion
In all, Sypris exposed the innovative mine detector to approximately 1,000 hours of intense use in just six weeks. Currently, several thousand of these mine detectors are in use by the Army in Afghanistan, Iraq, and other global locations where mines pose a threat to U.S. military personnel and civilians.
The Army, which had originally planned to deploy the units over several years, moved up its timetable because of the Iraq and Afghanistan conflicts. Our company�s capability to rapidly conduct environmental and human testing was a significant factor in successfully meeting the new deadline.
About the Author
Arvin Blank is the environmental test engineering manager at Sypris Test & Measurement. He holds a B.S. in mechanical engineering from California State University and has 20 years experience as a stress analysis engineer, dynamic environmental engineer, aerodynamics engineer, and environmental test engineering manager. In addition to Sypris, Mr. Blank has worked at Ford Motor Company, Ford Aerospace, Loral Aerospace, and Lockheed Martin. Sypris Test & Measurement, 6120 Hanging Moss Rd., Orlando, FL 32807, 800-775-2550, ext. 206, e-mail: [email protected].
October 2005