EMP Susceptibility and Protection of Vehicles
Preamble: The word, “vehicles” means any form of transportation. such as bicycle, motor bike, motorcycle, car, truck, bus, aircraft, helicopter, railroad, subway, boat or ship. However, this discussion here covers only automobiles (autos or cars) and trucks when speaking of vehicles. Other vehicles are addressed in another volume.
Unlike EMP shielding a component, such as a cell phone, ipad or computer, EMP protecting a vehicle requires shielding because of (1) the (vast number of variables, (2) no inter-vehicle connected wiring and (3) partial shielding already offered by vehicle metal skin, metal frame, cables, and other nearby metal parts, not already plastic. Thus, without simulated EMP testing, forecasting EMP susceptibility is difficult because of the variables, such as the 26 shown in the chart below. The different combination of variables can result in a range in excess of 100 times (40 dB) In vehicle-system susceptibility. Therefore, the Hollywood myth that all EMP unprotected moving vehicles will stop, following an EMP event is untrue and misleading.
Summary of Findings and Comments:
● Vehicles after about 1982 started to use microprocessor (low voltage, wide band) controls of engine, breaking, air-bags, and other operations. Thus, later vintage gasoline-engine and diesel vehicles are more susceptible to malfunction than before 1982. And, more recent microprocessors are even more susceptible because of still more in number and lower voltages.
● From reported USA EMP Commission test results and from simulated radiation tests performed at White Sands Missile Test Facility*, some vehicles exhibit only active engine turnoff, but can be restarted. Others evidence comparable susceptibilities whether or not the engine is running. A few vehicles had to be rebooted by disconnecting and reconnecting the battery first upon starting. Tests, vehicles and test results were too limited to profile accurate susceptibility statistics
● Based on similar EMP test results on trucks by the EMP Commission, few effects were observed below about 12 kV/m. At higher field-strength levels, 70% or more of the trucks on the road will manifest some anomalous response following EMP exposure. Roughly 15% or more of the trucks will experience engine stall, sometimes with permanent damage that the driver cannot correct.
In summary, it is seen that the results mentioned above are far from conclusive and suggest that vehicles may/will not fail an EMP exposure in contrast to earlier perceptions and reports to the contrary. However, since many of the test were performed below 50kV/m, and since almost no diesel-engines were involved, conclusions and recommendations are difficult to make.
BTW, the reader is referred to website: www.FutureScience.com which has more information on EMP vehicle vulnerability. To learn about other ways to test vehicles outside of an EMP test chamber (get their equivalent shielding effectiveness), visit our companion article, "Quick-Look EMP Protection Testing."
Recommendations for vehicle manufacturers
● Design and test selected vehicles to meet MIL-STD-188-125 field strength 50 kV/m EMP limits. (the k = 1,000 multiplier)
● Provide a retrofit kit and services to reduce vehicle radiated susceptibility. Some measure of the safety margin must be reported along with its meaning by the manufacturer ● Provide vehicle owners with an EMP manual of vehicle use and parking recommendations (see below) ● The greater the vehicular sheet metal vs. plastic skin overage of engine and cab the lesser is susceptibility. Cover or coat microprocessors with metal foil or metal paint or deposition. ● Protect cable entry and exit with surge suppressors. Selected cables should be shielded. Cables should have ferrite clamps at both ends. Keep cables close to metal vehicle frame.
● Since air gaps in metal parts bread down at 3 kV/mm potential difference, insulation of some wiring and especially motors, generators, starter relays, and ignition coils are vulnerable. Increased EMI protection is needed.
● The 80 year old practice of grounding the negative terminal of the battery to the vehicle frame and use the frame as the return in circuits should be ended. The reason is that the circuit loop area is somewhere between 100 to 10,000 times (60-100 dB) greater than a replaced twisted wire pair. This means that all the potential EMI (electromagnetic interference) picked up from coupled transmitter radiations, local and distant, from radar and especially from EMP will be reduced accordingly. For less than $100 in wiring increase plus labor, the EMP hardening impact will be many times rewarded. (Remember you heard this here first).
Recommendations for for vehicle owners:
● Until the vehicle EMP susceptibility data base becomes far greater, the following will not eliminate EMP susceptibility; but will help reduce it.
● Park your vehicle in a sheet metal shed or steel building to further mitigate susceptibility. Further improvement would result from sheet metal placed over the floor. (acts as a HF/VHF capacitor to short the induced EMI/EMP) ● Temporary storage of vehicle: Ten mil sheet metal floor. Cover vehicle with some 18” - 24” overlapped. 1-3 mils (household aluminum foil). Secure overlap with duct tape and connect foil to mat flooring with widths of foil bonded to each with duct tape. (This is a crude tempo shield).
● In the northern latitudes above roughly 38 degrees, engine oil warmers are plugged into AC outlets to make starting the vehicle easier in cold winter in the following morning. Use cable surge suppressors and ferrite absorbers at the cable auto entrance points.
● Do not count on any significant susceptibility reduction if vehicle is parked in your resident garage, since walls are radiation unprotected and all wiring enters at the breaker panel from an octopus-like antenna house circuit wiring EMP radiation pickup system in the outer house walls.
● The greater the vehicular sheet or foil or deposited metal vs. plastic skin overage of engine and cab, the lesser is susceptibility. Are microprocessors metal foil or metalized covered and protected with surge suppressors? Is the cabling shielded and clamped to the metal frame?
● The problem with the above suggestions is that that there appears to exist no sound quantitative documentation on vehicle EMP susceptibility. This is especially unfortunate as USA lives in a litigious society. Thus, perhaps the AMA might nudge its members to do this by (1) establishing test set-up conditions and test procedure standards, and sharing costs and results. Meanwhile, some of the above EMP vehicle recommendations may represent an EMC overkill; and some are still inadequate for EMP protection. Quien sabe? This is an unthinkable and unprofessional situation; the year is not 1933.
EMP Test Facilities in USA
● * White Sands Missile Test Range, New Mexico. In addition to military testing, EMP test simulation facility is rented to automotive manufacturers.
● Naval Air System Command has an EMP test simulation facility in Pax River, Maryland.
● Oak Ridge National Laboratory, Tennessee
● Naval Weapons Center China Lake, Ridgecrest, CA
● Sandia Labs, Albuquerque, NM has a bounded wave simulator (4x11x5 m).
● Air Force Weapons Lab at Albuquerque, NM has an HPD and a VPD. The largest open-air, EMP simulator in the world.
● Edwards AFB, CA Also a site at Palmdale HPD for unique aircraft EMP testing
● Army at Ft. Monmouth, NJ. May have moved EMP facility to Aberdeen Proving Ground, Aberdeen, MD.
● More limited EMP testing can be done at: Dayton T. Brown,- Engineering & Test Division - 1175 Church Street - Bohemia, NY 11716. Email: email@example.com - Phone: 800.837.8456 - Fax: 631.589.3648
● Most of the EMI test houses that perform MIL-STD-461E or later testing, also perform RS105 and CS-115 testing. Some of the labs have large chambers to be able to test vehicles for the Army.