AGENDA – EMC FOR SPACE SYSTEMS, FACILITIES, AND EQUIPMENT
The following is a quote from Spacecraft EMC P R O B L E M S, www.evaluationengineering.com, April/May 2007. "There are many wise old sayings within the aerospace industry. Some of them are humorous, some of them may annoy your friends, and some may cause you to loose your attaboy. This one may be pushing the limit on my attaboy, but it is one of those sage aerospace tenets that conveys the differences between scientists and engineers. It goes like this: When the rocket gets off its pad and the payload successfully reaches its destination the scientists have had another break-through . . . but let that rocket blow up on the pad and the engineers have screwed up again."
An electromagnetic compatibility (EMC) problem induced launch failure is generally not as spectacular as having a solid fuel rocket blow up on the pad and scatter its remains over a 1/2 square mile area, but EMC has certainly accounted for a large number of very expensive mission losses. Some of these launch vehicle (LV) and spacecraft (SC) combinations can run around $3,000,000,000 and more. Yes! There is supposed to be 9 zeros! Consequently an EMC engineer working in the aerospace industry doesn’t want to be branded as one of those engineers that screwed up again. Plus you don't get a second chance! In the LV/SC world it has to be done right the first time, though in the case of the Hubble Telescope NASA did get to do some on-orbit repairs. A rarity in the LV/SC world. The picture at the left is the International Space Station.
This course covers the primary space systems EMC problems. It does not contain ITAR/EAR/DOD restricted information. The course is based entirely on published open source materials.
EMC FOR SPACE SYSTEMS, FACILITIES, AND EQUIPMENT
UNDERSTANDING EMC AND EMC REQUIREMENTS Course Overview EMC Terms and Definitions EMI Sources, Victims, and Paths Transients - Lightning, ESD, EMP FAST Analysis SPACE SYSTEMS EMI/EMC REQUIREMENTS A Brief Overview of LV/SC requirements Documents MIL-STD-461C/F TEST REQUIREMENTS AND PROCEDURES Determining the required tests based on platform and user Selected MIL-STD-461 test limits and test procedures Conducted emission tests Conducted susceptibility tests Radiated electric field (EF) emission Radiated electric field susceptibility tests Miscellaneous tests from MIL-STD-461C COMMERCIAL OFF THE SHELF EQUIPMENT EMC Limitations of Commercial Off The Shelf Equipment (COTS) COTS Pro and Con CI/NDI Overvoew from MIL-STD-237C Differences Between Commercial and Military Standards Risks of Using Commercial Test Data EMC SYSTEMS DESIGN/PROBLEM CONSIDERATIONS The 3 Most Important EMC Design Rules Key EMC Design Facilitators Circuit Response to EMI CONDUCTED VS RADIATED COUPLING Simplified Loop Radiation Simplified Loop Pickup Wavelength vs Frequency Amplitude vs Time vs Frequency Spectrum Density vs Pulse Shape EMC CIRCUIT DESIGN EMPHASIS Design Approaches Radiation Loops Making Loop Areas Smaller Basic PCB Layout CABLING EMC DESIGN & INSTALLATION Coupling by DM, CM, and Antenna Modes Differential Mode Loop Area Reduce DM Loops DM Radiation Pattern HF from Two Parallel Wires Twist Attenuation Use Shielded Cable Reducing DM Coupling Reducing Field to Cable DM Coupling Common Mode (CM) Loop Area Shielding to minimize DM and CM CABLE TO CABLE CROSSTALK Cable Design Cable Segregation/Isolation Electric and Magnetic Crosstalk Crosstalk Waveform Distortion DOD-W-83575A Wire Harness EED Wire/Cable Requirements FILTERS & ISOLATION TRANSFORMERS FOR CONTROL OF CE/CS Filters Inter and Intra System Filters Inductor-Capacitor Resonance Filter Attenuation vs Elements Prototype Butterworth LP Filter Filter Attenuation vs Source Impedance Isolation Transformers Performance of Ordinary Isolation Transformer Double-Shielded Isolation Transformer Typical attenuation Shielded-Isolation Transformers GROUNDING/BONDING Grounding and Bonding Rationale Single and Multipoint grounding Earth Grounding Lightning Protection for Power & Signal Cables Cable and Connector Grounding Box and System-Level Grounding Wire Grid and Plane Impedance Bonding Impedance vs Material Practical Solutions SHIELDING FUNDAMENTALS EF & HF from Small Antenna Wave Impedance vs Distance Shielding Equations Low Frequency HF Shielding Sources of Discontinuities Cable/Connector EMC Areas Shield Cable Connections Connector Shielding ENCLOSURE AND PAYLOAD FAIRING SHIELDING Scattering in Thin Materials Slot Aperture Circular Apertures Mechanical/Electrical Considerations Aperture Integrity Waveguide-Below-Cutoff Effect Cable Penetrations Cable Shielding Effects of Enclosure Size Modeling the Payload Fairing as a Shield Cavity Amplification Absorber Materials SEAM DESIGN AND CONSTRUCTION Butt Seams Compressive Seams SE vs Closure Pressure Shear Seams Four Popular RF Gasket Types Qualitative Shielding Effectiveness Shielding Degradation from Finish ELECTRO-GALVANIC COMPATIBILITY Corrosion Induced EMC Failures Galvanic Couples Oxidation/Reduction Reaction Preventing Corrosion Launch Site Protection Requirement MIL-STD-1250 -- Gold Reference LIGHTNING/ELECTROSTATIC DISCHARGE (ESD) Electron Mobility and Charge Creation Mechanism of ESD and Lightning ESD/Lightning Coupling into Electronic Systems Radial and Linear Current Flow Direct & Indirect Discharge ESD Shielding: Conductive vs Plastic Enclosures Facilities/Lightning Protection Launch Weather Constraints Circuit/Cabling Hardening ESD Test and Evaluation MULTIPACTION & SPACE CHARGING Ionization Breakdown RF Voltage Thresholds Radiation effects on electronic systems Single Event Effects (SEU/SEL/SEB) Photoelectric Emission Dielectric Charging from High energy Particles EMC/COSITE & OUT OF BAND INTERFERENCE Transmitter/Receiver EMC Problems Receiver Bandwidth Considerations Co-Channel EMI Adjacent Channel EMI Problems With Hand Held Transmitters Receiver Overload/Desensitization Transmitter Inhibits What is Out of band interference Field strength, power & antenna gain Intermodulation products Out of band Interference Control Rusty Bolt Intermodulation/Interference
Antenna EMC Characteristics Antenna Fundamentals Gain and Bandwidths Polarization Electric Field (EF) vs Power & Gain RADHAZ Cosite Antenna to Antenna Coupling Antenna Placement/Separation Re-Rad Antennas Isolation by Directional Antennas, Antenna Shrouds/Hats, Blanking and Adaptive Antennas Blockages from Superstructure, Launch Platform, Gantry, and Other Objects Reflections from Conducting Surfaces, Cylinders, and Corners RF Absorber Material Isolation by F A S T RF LINK MARGIN Simplified Link Model Influencing Factors Atmospheric Attenuation Signal Propagation