JED - February 2016 - (Page 44)

EW 101 Directed Energy Weapons - Part 5 HPRF Weapon Target Effects By Dave Adamy The Journal of Electronic Defense | February 2016 44 T his column is based on an excellent paper by Lt Col John Brunderman from the Center for Strategy and Technology at the US Air Force's Air War College. Target Response The targets for high power radio frequency (HPRF) weapons (also known as High-Power Electromagnetic - or HPEM - weapons) include humans and electronic devices. There are two ways that HPRF weapons can degrade a target: Molecular heating and electrical stimulation. Molecular heating occurs when powerful sine waves cause the molecules of material to rub together rapidly. This is what occurs in a microwave oven. Materials containing carbon or liquid are particularly susceptible to this process. The target is degraded when this heating raises fuel or explosive payload material above its flash point. This could cause a weapon to explode before the weapon reaches its target, or heat structural elements until they fail. If the object is to kill humans, this heating could destroy their brains or other vital body parts. The problem with molecular heating is that it requires a large amount of power and significant dwell time on the target. Electrical stimulation involves the induction of transient voltages and currents in electrical devices. This process re- quires significantly less power and illumination time than molecular heating. Narrow or wideband RF energy couples with any electrically conductive material illuminated by the beam to stimulate electron flow. Transient currents are generated in the material, and that material acts like an antenna, propagating spurious signals to other material and components to confuse or damage other sensitive parts of the target system. With enough received power, sparks will be generated or arcing will occur. This may ignite fuel or explosive material in a warhead, and will propagate around the target structure causing hot spots. These hot spots can be much stronger than the received field from the HPRF weapon. Note that an aircraftmounted rocket was set off by this effect on the USS Forrestal during the Vietnam war. Table 1 details the four types of effects that can be caused by an HPRF weapon. As you move down the table, each effect requires more received power in the target and/or greater illumination time. Upset requires less power that the other effects, but, like jamming, it only lasts as long as the target is illuminated. Thus, long-term denial of a target capability requires continuous application of the weapon. However, like jamming, the goal may be to just break a lock, causing a weapon to go to a reacquisition mode to continue an attack. Table 1: Types of Target Degradation from HPRF Weapons Effect on Target Description Upset Temporary disruption of normal circuit functions. Effects are reversed when the signal from the weapon no longer illuminates the target. Lockup Disruption of normal circuit functions. Requires specific action to reset and return circuit to normal function. Latch-up Some function of target is permanently destroyed. Requires repair of the target system to return it to normal function. Burnout Physical destruction of some part of the target system, typically when wires are melted by excessive current.

Table of Contents for the Digital Edition of JED - February 2016

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Alternatives to Positioning, Navigation and Timing
Future Operating Environment 2035
Technology Survey: FPGA Boards
The Heat is On
EW 101
AOC News
Index of Advertisers
JED Quick Look

JED - February 2016