1201.pdf Practice: Derate applied stress levels for electrical, electronic, and electromechanical (EEE) part characteristics and parameters with respect to the maximum stress level ratings of the part. The allowed stress levels are established as the maximum levels in circuit applications.Benefits: Derating lowers the probability of failures occurring during assembly, test, and flight. Decreasing mechanical, thermal, and electrical stresses lowers the possibility of degradation or catastrophic failure.
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1214msfc.pdf Practice: Electrical grounding procedures must adhere to a proven set of requirements and design approaches to produce safe and trouble-free electrical and electronic circuits. Proper grounding is fundamental for reliable electronic circuits.Benefits: Grounding procedures used in the design and assembly of electrical and electronic systems will protect personnel and circuits from hazardous currents and damaging fault conditions. Benefits are prevention of potential damage to delicate space flight systems, subsystems and components, and protection of development, operations, and maintenance personnel. 1215-1: Preliminary Design Review
Practice No. PD-ED-1244 Practice: Minimize the adverse effects of electrostatic discharge (ESD) on spacecraft by implementing the following three design practices: Make all external surfaces of the spacecraft electrically conductive and grounded to the main structure.
Provide all internal metallic elements and other conductive elements with an "ESD conductive" path to the main structure.
Enclose all sensitive circuitry in an electrically conductive enclosure-- a "Faraday cage".
Benefit: The first two practices should dissipate most electric charges before a difference in potential can become high enough to cause an ESD. If a discharge occurs, the third practice lowers the coupling to sensitive circuits, reducing the probability or severity of the interference. 1245: Magnetic Dipole Allocation
1258jsc.pdf Practice: During system design, choose electronic components/devices which will provide maximum failure tolerance from Space Radiation Effects. The information below provides guidance in selection of radiation hardened (rad-hard) solid state devices and microcircuits for use in space vehicles which operate in low-earth orbits.Benefit: This practice provides enhanced reliability and availability as well as improved chances for mission success. Failure rates due to space radiation effects will be significantly lower, and thus system down time will be much lower, saving program cost and resources. 1259: Acoustic Noise Requirements
1268msfc.pdf Practice: Understanding and addressing the design environment, component interactions, and potential failure modes are the keys to high reliability in high performance liquid hydrogen turbopumps for launch vehicle engines. Designing and using a combination of unique sealing, cooling, processing, material selection, and balancing techniques in response to engine design requirements will permit the development, production, and reliable flights of hydrogen turbopumps.Benefit: Use of precision design; manufacturing; and advanced material selection, fabrication, and treatment techniques will ensure reliable operation of large, high performance liquid hydrogen turbopumps. Many of these practices will also lengthen the operational life of the turbopump, increasing the number of uses before teardown, inspection, refurbishment, and re-assembly for subsequent flights. In addition to higher reliability, lower costs and continued assurance of high performance are resulting benefits. 1269: High Performance Liquid Oxygen Turbopumps
Practice No. PD-AP-1307 Practice: Analyze all systems to identify potential failure modes by using a systematic study starting at the piece part or circuit functional block level and working up through assemblies and subsystems. Require formal project acceptance of any residual system risk identified by this process.Benefit: The FMECA process identifies mission critical failure modes and thereby precipitates formal acknowledgment of the risk to the project and provides an impetus for design alteration. 1308: Electromagnetic Interference Analysis of Circuit Transients
Practice No. PD-AP-1308 Practice: Network circuit analysis programs are valuable tools in the analysis of switching circuit transients which are capable of generating conducted and radiated electromagnetic interference (EMI). The analysis is performed to insure that disruptions or degradations due to EMI do not occur. EMI is capable of disrupting the normal operating environment of an electronic circuit or degrading the performance of such a circuit.Benefits: Circuit analysis for the purpose of evaluating the conducted and radiated EMI from a switching circuit has resulted in the proper design of switching circuit electronics. The devices connected to electronic switching circuits will not be adversely affected by transient currents and associated radiated fields generated by such currents. 1309: Analysis of Radiated EMI From ESD Events Caused by Space Charging
Practice No. PD-AP-1310 Practice: Unexpected interference in receivers can be avoided in a complex system of transmitters and receivers by performing an intermodulation analysis to identify and solve potential problems. Various emitters may be encountered during system test, launch, boost, separation and flight. There are a large number of these harmonics and intermodulation products from which potential sources of spurious radiated interferences are identified by a computer aided analysis and corrective measures evaluated.Benefit: Spurious radiated interference can be identified and evaluated during the design phase of the project. Solutions can be proposed and implemented in the design phase with far less impact on cost and schedule than when changes are required later. 1311: System Reliability Assessment Using Block Diagraming Methods
1314msfc.pdf Practice: Sneak circuit analysis is used in safety critical systems to identify latent paths which cause the occurrence of unwanted functions or inhibit desired functions, assuming all components are functioning properly. It is based upon the analysis of engineering and manufacturing documentation. Because of the high cost of a sneak circuit analysis, it should be conducted only in areas where there is a high potential for a hazard.Benefit: Identification of sneak circuits in the design phase of a project prior to manufacture can improve reliability; eliminate costly redesign and schedule delays; and eliminate problems in test, launch, on-orbit, and protracted space operations. Sneak circuit analysis can also be beneficial in identifying drawing errors and design concerns. 1315: Redundancy Switching Analysis
Practice No. PD-AP-1315 Practice: To verify that the failure of one of two redundant functions does not impair the ability to transfer to the second function, a rigorous failure modes, effects, and criticality analysis (FMECA) at the piece part-level is performed for all interfacing circuits.Benefits: By using a systematic method to assure the switching functionality of designed-in redundancy, the long-term performance of complex systems can be assured. 1316: Thick Dielectric Charging/Internal Electrostatic Discharge (IESD)
Practice No. PD-AP-1316 Practice: Dielectric compositions used in such spacecraft materials as circuit boards, cable insulation and thermal blankets will build up an imbedded charge when exposed to a natural space environment featuring energetic electrons. If the electric field resulting from the imbedded charge exceeds the breakdown threshold for the dielectric, an arc will occur, damaging the dielectric and producing an electromagnetic pulse which can couple into subsystem electronics. Enhance hardware reliability in an energetic electron environment by conducting a materials inventory, resistivity analysis, and shielding assessment. Ascertain material susceptibility to deep dielectric charging and explosive discharge when the material: Is exposed to an energetic electron flux exceeding 2x105 electrons/(cm2-s), and
Achieves an imbedded charge density greater than a threshold of 1011 electrons/cm2.
Benefit: Materials and design structures which represent possible internal electrostatic discharge (IESD) sources can be identified early in the program. Risk to hardware may be reduced through design changes which substitute materials having sufficient conductivity to permit charge bleed-off. Sensitive cable runs may be rerouted or shielded to reduce exposure to energetic electrons. Grounding schemes may be changed to ensure that otherwise isolated conductors are grounded and that grounds are designed to maximize the opportunity to bleed-off the charge from dielectric materials. 1317: Flight Load Analysis as a Spacecraft Design Tool
1410.pdf Practice: Each flight project provides requirements for defining and implementing a contamination control program applicable to the hardware for the program. The program consists first in defining the specific cleanliness requirements and setting forth the approaches to meeting them in a Contamination Control Plan. One significant part of the Contamination Control Plan is a comprehensive Materials and Process Program beginning at the design stage of the hardware. This program helps ensure the safety and success of the mission by the appropriate selection, processing, inspection, and testing of the materials employed to meet the operational requirements for the application. The following potential problem areas are considered when selecting materials: radiation effects, thermal cycling, stress corrosion cracking, galvanic corrosion, hydrogen embrittlement, lubrication, contamination of cooled surfaces, composite materials, atomic oxygen, useful life, vacuum outgassing, toxic offgassing, flammability, and fracture toughness. The practice described here for the collection and compilation of vacuum outgassing data is used in conjunction with a number of other processes in the selection of materials. Vacuum outgassing tests are conducted on materials intended for space flight use, and a compilation of outgassing data, Reference 1, is maintained and constantly updated as new materials are tested. This includes materials used in the manufacture of parts intended for space applications.Benefit: These test data provide outgassing information on a wide variety of materials and should be used as a guide by engineers in selecting materials with low outgassing properties. 1411: Heat Sinks for Parts Operated in Vacuum 2ff7e9595c
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