SAVEinc
SURVIVABILITY and
VULNERABILITY
DESIGN GUIDELINES
| D - TOTAL DOSE | |
| Phenomena | Charge buildup in oxide layer degrades electrical parameters of semiconductor devices. |
Design Guidelines |
- Part selection - Circuit design to tolerate degradation - Electron shielding - mass |
| DEMP - DISPERSED ELECTROMAGNETIC PULSE | |
Phenomena |
DEMP couples energy to structures like RF energy is coupled to an antenna. |
Design Guidelines |
- Filtering - SGEMP hardening provides DEMP protection |
| ECEMP - ELECTRON CAUSED ELECTROMAGNETIC PULSE | |
Phenomena |
Electrons collect on floating metal eventually arcing to low potential; possible damaging a semiconductor device. |
Design Guidelines |
- Provide grounding path for all
floating metal; <1 Gohm. - Or shield charging flux to <0.3 pA/cm2 |
| EMP - ELECTROMAGNETIC PULSE | |
Phenomena |
Electromagnetic fields from nuclear events or other sources, will induce voltages and currents on all exposed conductive surfaces of enclosures, vehicles, shelters and interface cables. These voltages/currents, if not suppressed, could penetrate into the enclosures, vehicles or shelters and cause damage to electronic components inside or damage the electronic components connected to the interface cables. |
Design Guidelines |
- All covers, connectors and assemblies should have
EMP gaskets at the mating surfaces. Due to the
differences in threat levels, EMI gaskets may not provide
the protection required for the EMP threat. - Depending on the threat level and cover thickness, the fasteners holding the cover should be close enough together to minimize the buckling of the cover between the fasteners. - All cables should be shielded and the shields should be circumferentially terminated around the backshell of the connector. - All cables should be mounted as close to a ground plane as possible to minimize field pickup. - Any apertures in the enclosure for displays, cooling ducts, etc., should have screens or honeycomb covering the aperture to minimize penetration into the enclosure. The screen or honeycomb should be conductively terminated 360 degrees around the opening. - Any terminal protection devices (TPDs) required should have short leads and be mounted as close to the interface connector as possible and within a shielded enclosure, to prevent re-radiation. |
| G - DOSE RATE | |
Phenomena |
X- and gamma-rays cause transient ionization currents to flow in semiconductor devices resulting in upset, latchup, and possible burnout. |
Design Guidelines |
- Part selection - dielectric isolated
(least sensitive) - Current limiting; e.g. 2 ohm/V Vc limiting - Circuit design functional mechanization - Latchup radiation screening - Nuclear Event Detector (NED) and circumvention |
| N - NEUTRON FLUENCE | |
Phenomena |
Neutrons cause lattice displacement damage in semiconductor devices resulting in electrical parameter permanent degradation. Minority carrier devices are most sensitive (e.g., NPN and PNP transistors, especially when operated in the linear region. |
Design Guidelines |
- Parts selection - high frequency parts
hardest - Circuit design to tolerate degradation |
| NBC - NUCLEAR, BIOLOGICAL and CHEMICAL | |
Phenomena |
"Nuclear" produces fallout from low-level and surface-burst tactical nuclear weapons. Biological and chemical agents produce a variety of persistent and non-persistent contamination effects. |
Design Guidelines |
- All systems must be designed to be
operational by personnel wearing NBC and cold weather
protective clothing including the mission-oriented
protected posture (MOPP) level IV ensemble. - All exposed cables and connectors should be covered with the appropriate material to protect them from accumulation of the NBC contaminants and decontaminants. - The mechanical interface between the components of the system should be designed to eliminate cracks, crevices and traps for contaminants. - Removable fasteners should be hex-head bolts without depressions or cavities in the head. No slotted fasteners should be used in exposed areas of the system. - Plain washers and lock washers should not be used in exposed areas. Self-locking bolts will be used to hold the fasteners. - Bolt lengths will be short as possible to prevent exposed threads from trapping contaminants. - All gaskets used must be compatible with both the NBC and EMP/EMI environments. |
| S/C - SPACECRAFT CHARGING | |
Phenomena |
Electrons collect on external S/C materials eventually discharging to space or to low potential regions of S/C sending electrical transient into S/C. |
Design Guidelines |
- Periodic grounding of thermal blanket - Conductive paints - Potential buildup in paint is a function of paint thickness |
| SGEMP - SYSTEM GENERATED ELECTROMAGNETIC PULSE | |
| Phenomena | Results from the x- and gamma-ray induced electron emission from surfaces of materials. |
Design Guidelines |
- Coat surfaces with low atomic number
(Z) material; structures and PCB - RF tight enclosures to keep SGEMP fields out - RF shield cables - Terminal protection devices (TPDs) at I/Os - High-Z shielding to reduce x-rays |
| TMS - THERMOMECHANICAL SHOCK | |
Phenomena |
X-rays non-uniform energy deposition in surface materials causes shock wave to be sent through the material causing thermal and/or mechanical damage. |
Design Guidelines |
- Si optics harder than Ge optics - Weld or low-Z coat solder joints - Low-Z material harder than high-Z - X-ray shield; low-Z coated |
| AIR BLAST | |
| Phenomena | Rapid changes in air pressure cause a potentially crushing or displacing effect followed by wind and debris. |
| Design Guidelines | - Evaluate structural design and supports - Material selection - Shielding |
| THERMAL PULSE | |
| Phenomena | Rapid energy deposited on equipment surfaces causes surface heating, possibly charring, melting, or evaporating the surface, possibly causing heat fatigue or overheating |
| Design Guidelines | - Evaluate structural design and supports - Material selection - Shielding |
(714) 524-5231
fax (714) 572 - 3811
saveinc@earthlink.net
The Radiation Specialists