With the recent news that the U.S. President’s $223 million “doomsday plane” is protected from electromagnetic pulse (EMP) came the inevitable questions. What is EMP and how is it created? How can a plane with a reported 165,000 pounds of state-of-the-art electronics possibly be protected from such a sinister attack?
EMP & Its Creation
EMP is a high amplitude, short duration, broadband pulse of electromagnetic energy which can have devastating effects on unprotected electronic equipment and systems.
The electromagnetic pulse effect was first observed during the early testing of high altitude airburst nuclear weapons. During the explosion, gamma rays (high energy photons) are rapidly released in all directions from the blast. These gamma rays interact with air molecules in the earth’s atmosphere, which creates electromagnetic energy. This interaction process is called the “Compton Effect.”
Energy of these pulses disperse across a broad spectrum, but the majority of pulse energy resides in the frequency spectrum of 10MHz-100MHz. For a large quantity of electronic equipment, this is the operating range and hence the greatest risk. Peak field strengths are estimated to reach into thousands of volts.
Non-nuclear EMP technologies – called “Directed Energy Weapons” – are increasingly being developed. They are capable of graduated effects on electronics ranging from disrupting operation, to permanent damage, and complete destruction. These weapons include:
- Arc Discharge EMP Generator
- Flux Compression Generator (FCG)
EMP Immunity Testing
The RS105 test method specified in MIL-STD-461F addresses the risk of radiated exposure to an EMP event. The U.S. Navy, among other military branches, requires RS105 testing for nearly every installation platform, from surface ships, submarines, and aircraft, to ground applications.
The test follows this procedure:
- Start at 10% of specified level
- Verify waveform
- Apply pulse 5 times at the rate of not more than 1 pulse per minute
- Rotate equipment under test (EUT) 90 degrees, and pulse 5 more times
- Rotate another 90 degrees and pulse 5 times
- Monitor for signs of degradation
The purpose of RS105 testing is not to damage the equipment, but to determine its immunity threshold to the electromagnetic pulse.
Hollywood’s Take on EMP
Last, and most important, was the EMP attack, or “pinch,” featured in the 2001 movie Ocean’s Eleven possible? If you remember, George Clooney and his fellow con artists utilize a “Z-pinch” that detonates an intense electromagnetic pulse that blacks out Las Vegas’ entire power grid for a few moments (in order for them to sneak into a casino vault).
No, says Sandia National Laboratories, owner of the world’s most powerful Z-pinch. The super-charged electrical generator creates a rainbow spectrum of intense x-rays, but a feeble EMP.
Read more about RS105 and other military electromagnetic compatibility (EMC) tests.