美国宇航局工艺标准：电缆和线束通用规范

电缆和线束通用规范
	电缆和线束通用规范 Often the most overlooked and ignored component of any electrical/electronic design, 电缆和线束es are essential to the accurate and rapid transmission of data and control signals.
PREFERRED BACKSHELL Connector backshells shall be potted and molded, or use stress relief boots as required, in accordance with applicable engineering documentation. NASA-STD-8739.4 [13.1.1.c]	PREFERRED BEND RADIUS Cables and harnesses shall not be subjected to bending forces resulting in radii less than the minimum specified for the most sensitive component (i.e.: coaxial, fiber, etc.) in the assembly. Best Workmanship Practice
PREFERRED COAXIAL/FIBER OPTIC CABLE LOCATION Harnesses should be designed so that coaxial/fiber optic cables are located at or near the bundle center to minimize flexure and to provide additional protection. Best Workmanship Practice	PREFERRED COAXIAL/FIBER OPTIC CABLES Coaxial cable (flexible, semi-rigid, rigid) and fiber optic cables shall exhibit a neatly organized layout, with smooth bends and sufficient stress relief. Best Workmanship Practice

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 1







电缆和线束通用规范 (cont.)
PREFERRED CONNECTOR STYLE Connectors shall be straight, right-angle or flange-mount. The use of right-angle connectors shall be minimized and restricted to applications where stress-free mounting of the cable assembly can be assured. Best Workmanship Practice	PREFERRED DISCRETE WIRE HARNESSES Harnesses exhibit a neatly organized layout with smooth bends and sufficient stress relief. Connector cable clamps and cable straps are properly set. NASA-STD-8739.4 [19.6.1.e]
PREFERRED DUST CAPS The mating surfaces of all unmated connectors shall be protected by covers during storage, handling and installation. Connectors on ESD sensitive hardware shall be protected by ESD rated dust caps/covers. NASA-STD-8739.4 [13.1.2], [16.2.4], [16.3.3]	PREFERRED HYBRID CABLES/HARNESSES Hybrid cables/harnesses (copper/fiber optic/coaxial conductors) shall be designed to comply with the requirements of the most sensitive and demanding component (typically the fiber optic cable) in the assembly. Best Workmanship Practice
PREFERRED IDENTIFICATION CABLES/HARNESSES Each cable/harness shall be identified by a permanent label/marking. NASA-STD-8739.4 [14.2.1]	PREFERRED IDENTIFICATION CONNECTOR Each connector shall be identified by a permanent label/marking affixed directly to the connector body, or to the cable adjacent to the connector. NASA-STD-8739.4 [14.2.2]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 2







电缆和线束 GENERAL REQUIRMENTS (cont.)
PREFERRED POLARIZATION/KEYING Interconnecting cables and harnesses shall be designed with physical constraints (keying, sizing, polarization, etc.) to prevent incorrect mating/interchanging with similar sized/colored connectors. NASA-STD-8739.4 [7.1]	PREFERRED RIBBON CABLE The cable assembly meets dimensional, layout and design requirements and exhibits a smooth, flat profile with no visible damage to the connectors or the insulation. Connectors are properly aligned and seated. Best Workmanship Practice
PREFERRED SHIELD TERMINATION - FLOATING Heat shrink tubing is properly installed, tightly shrunk and the termination is visible. Overlaps are of sufficient length to meet minimum electrical spacing. NASA-STD-8739.4 [9.8.1], [9.9], [11.5], [19.6.1]	PREFERRED SHIELD TERMINATION - GROUNDED Heat shrink sections are properly installed, tightly shrunk and the termination is visible. Overlaps meet minimum electrical spacing. Ground wire exhibits proper bend radius and strain relief. NASA-STD-8739.4 [7.3.22], [9.8.1], [9.9], [11.5], [19.6.1]
ACCEPTABLE SPOT TIES Spot ties shall consist of a clove hitch, followed by a square or other similar non-slip knot (i.e.: surgeon, etc.). NASA-STD-8739.4 [9.2.2]	ACCEPTABLE BACKSHELL ASSEMBLY Connector backshells, adapters and clamps shall be assembled and torqued per engineering documentation. NASA-STD-8739.4 [13.5]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 3







电缆和线束通用规范 (cont.)
ACCEPTABLE BACKSHELL SCREW PROTRUSION Screws shall protrude a minimum of 1-1/2 threads beyond the threaded hardware (e.g., nut, clamp, etc.), but shall not violate minimum electrical spacing or snag requirements, unless otherwise specified by engineering documentation. Best Workmanship Practice	UNACCEPTABLE EXCESSIVE THREAD PROTRUSION Excess thread protrusion represents an assembly, interference and electrical separation problem, as well as adds unnecessary weight to the assembly. Best Workmanship Practice
ACCEPTABLE BREAKOUT DRESS W/ FABRIC BRAID Braiding shall be dressed to form a smooth profile across the breakout. Braiding shall not be split, slit or punctured to provide a breakout opening. NASA-STD-8739.4 [9.3]	UNACCEPTABLE SPLIT/SLIT BRAIDING AT BREAKOUT Braiding shall not be split, slip or punctured to provide an opening at the breakout. NASA-STD-8739.4 [9.3]
ACCEPTABLE CABLE LACING RUNNING STITCH The lacing begins and ends with a knot. Wraps are properly spaced (relative to harness diameter) to maintain the wiring in a tight, neat bundle. Ends are properly trimmed. NASA-STD-8739.4 [9.2]	UNACCEPTABLE CABLE LAYUP Cables containing discrete conductors shall be fabricated in one or more layers, by winding the conductors together uniformly. Layup (twist) of each layer shall be 8-16 times the outer harness diameter. NASA-STD-8739.4 [7.3.20], [19.6.1.e.4]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 4







电缆和线束通用规范 (cont.)
ACCEPTABLE CABLE LACING SPOT TIES Ties are neat, tight and properly spaced (relative to harness diameter) to maintain the wiring in a tight, neat bundle. Ends are properly trimmed. NASA-STD-8739.4 [9.2.2]	UNACCEPTABLE LOOSE CABLE LACING The lacing has not been properly installed, resulting in a loose, unorganized bundle. NASA-STD-8739.4 [19.6.2.d.4]
ACCEPTABLE CABLE STRAPS/TIES Plastic straps should have metal tangs that lock securely into the ribbed portion of the strap. NASA-STD-8739.4 [7.3.4]	ACCEPTABLE CONDUCTOR DRESS All wires are dressed with even bends and sufficient strain relief. Conductor crossover is minimized. NASA-STD-8739.4 [19.6.1.e]
ACCEPTABLE CABLE TIES/TIE WRAPS The cable ties/tie wraps are sufficiently tight to prevent lateral movement along the cable bundle under normal handling, but can be rotated in place. Strap ends have been trimmed off square and flush with the face of strap head. NASA-STD-8739.4 [9.6]	UNACCEPTABLE UNTRIMMED CABLE TIES The strap end shall be trimmed off, flush with the back end of the strap head. NASA-STD-8739.4 [9.6], [19.6.2.d.5]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 5







电缆和线束通用规范 (cont.)
ACCEPTABLE CONNECTOR SAVERS The use of connector savers is recommended. Connector savers shall meet the same requirements as a flight connector. NASA-STD-8739.4 [17.2.7]	ACCEPTABLE DIRECT WEAVE FABRIC BRAID Fabric braids woven directly on interconnecting harnesses or cables may be loose or tight. The finish shall be smooth, without gaps in coverage, and without frayed ends. NASA-STD-8739.4 [9.4]
ACCEPTABLE DISCOLORATION/SCUFFING CONNECTOR Slight scuffing or discoloration is acceptable, provided there is no impact to form, fit or function, and there is no exposure of base metal. Best Workmanship Practice	ACCEPTABLE DISCOLORATION/SCUFFING INSULATION The cable does not exhibit evidence of insulation damage, such as cuts, nicks, scrapes, crushing, cold flow or burns. Slight scuffing or discoloration is acceptable. NASA-STD-8739.4 [19.6.2.e.9]
ACCEPTABLE FABRIC BRAIDED SLEEVING Prewoven fabric (unvarnished) braid sleeving may be installed over the wire harness. Sleeving shall be snug, secured at both ends and shall not slide freely. Ends shall not be frayed or unraveled, and shall be tucked under. NASA-STD-8739.4 [9.3]	ACCEPTABLE FABRIC BRAID SLEEVING ALTERNATE END DRESS The end of the braid may be secured by connector clamps, other hardware or potting. NASA-STD-8739.4 [9.3.2]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 6







电缆和线束通用规范 (cont.)
ACCEPTABLE FABRIC BRAID SLEEVING BASIC END TERMINATION The end of the braid shall be tucked under and secured with a spot tie or plastic strap. NASA-STD-8739.4 [9.3.1]	ACCEPTABLE GLASS BRAID SLEEVING The ends of glass braid may be bonded by use of adhesive, and then secured by spot tie or other means to prevent movement on the wire bundle. NASA-STD-8739.4 [9.3.3]
ACCEPTABLE GROUP SHIELD TERMINATION Shield ground leads shall be terminated to a common ground point. No more than 4 conductors, plus a drain wire, shall be terminated in a single splice. NASA-STD-8739.4 [11.6]	UNACCEPTABLE DAISY-CHAIN GROUND TERMINATION Shield ground leads terminated in a dasy-chain configuration are susceptible to a single-point failure, should one of the links break. NASA-STD-8739.4 [19.6.2.f.2]
ACCEPTABLE HEAT SHRINKABLE SLEEVING Sleeving shall be sized to provide a tight, smooth finish in the area of maximum diameter. Tubing shall be uniformly shrunk, without cracks, punctures, charred, burns or wrinkles. NASA-STD-8739.4 [9.8.1], [9.11], [19.6.1.e.13]	ACCEPTABLE HEAT SHRINK TUBING AS STRESS RELIEF The sleeving covers the termination and extends a minimum of 5 mm (0.20 in.) over the wire insulation. Tubing is fully shrunk, tight and sufficiently rigid to provide stress relief and prevent flexure at the solder termination. NASA-STD-8739.4 [9.9], [Fig. A]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 7







电缆和线束通用规范 (cont.)
ACCEPTABLE IDENTIFICATION Each cable/harness shall be identified by a permanent label/marking. Each connector shall be identified by a permanent label/marking affixed directly to the connector body, or to the cable adjacent to the connector. NASA-STD-8739.4 [14.2.1], [14.2.2]	ACCEPTABLE IN-LINE SPLICE The splice exhibits a smooth profile, proper strain relief and is located in an area of the harness not subjected to flexure. Best Workmanship Practice
ACCEPTABLE INSULATION WRAP Non-conductive tape/insulation wrap may be used in applications in which the use of heat-shrinkable tubing is impractical. Tape and wrapping materials shall be installed per engineering documentation. Best Workmanship Practice	ACCEPTABLE METAL BRAID SLEEVING Metal braid sleeving may be installed over harnesses by either direct weave or by use of prewoven tubing. An insulation/separation layer shall be installed between the harness and the metal braid. NASA-STD-8739.4 [9.7]
ACCEPTABLE OVERALL HARNESS SHIELDING An overall braided metallic shield provides mechanical and electrical protection (EMI/RFI) to the harness. Metallic shielding shall exhibit a smooth and tight finish, with a uniform distribution of coverage and no projecting strands. NASA-STD-8739.4 [11.1.3]	ACCEPTABLE POLYIMIDE/NYLON BRAID SLEEVING HOT KNIFE SEALING Polyimide or nylon braids (for use on ground support equipment) may have their ends sealed by use of a "hot knife" or similar instrument. NASA-STD-8739.4 [9.3.4]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 8







电缆和线束通用规范 (cont.)
ACCEPTABLE SHIELD/DRAIN WIRE The shield and drain wire have been properly terminated, per engineering documentation. NASA-STD-8739.4 [19.6.1.f.2]	ACCEPTABLE SPIRAL WRAP SLEEVING Spiral wrap shall be tight, uniformly spaced and shall not overlap. Ends shall be trimmed to eliminate sharp edges. Note: Spiral wrap shall not be used on spacecraft or launch vehicles. NASA-STD-8739.4 [9.5]
ACCEPTABLE SOLDER SLEEVE TERMINATION The solder sleeve has been properly installed and tightly shrunk. Strain relief is acceptable. Overlaps are of sufficient length to meet minimum electrical spacing. Solder fillet is visible, fully flowed and smooth. NASA-STD-8739.4 [11.4]	UNACCEPTABLE SOLDER SLEEVE TERMINATION The solder sleeve has not been completely shrunk and is improperly positioned, resulting in a poor fit that does not provide a good mechanical grip or seal, and which does not meet minimum overlap requirements. NASA-STD-8739.4 [9.8.1], [9.11]
ACCEPTABLE SPLICE ASSEMBLY PROFILE The location of splices shall be staggered to minimize the increase in profile to the harness. Final assembly profile shall not impact form, fit or function. Best Workmanship Practice	ACCEPTABLE STRAIN RELIEF The cable (shield/unshielded) should be dressed to ensure that the strain relief mechanism transfers structural stresses from the connector to the cable sheath (or strength member) rather than to the individual conductors. Best Workmanship Practice

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 9







电缆和线束通用规范 (cont.)
ACCEPTABLE SPLICE/SOLDER SLEEVE RESTRAINT Cable ties/lacing shall be installed at both ends of a splice or solder sleeve, but placement shall not violate stress relief requirements. Best Workmanship Practice	UNACCEPTABLE SPLICE/SOLDER SLEEVE RESTRAINT Cable ties/lacing shall not be installed across the splice/solder sleeve body, unless sufficient protection is provided to prevent compression damage to the termination and/or to the insulation of adjacent conductors. Best Workmanship Practice
ACCEPTABLE STRESS RELIEF Wires exiting from the connector shall be stress relieved. NASA-STD-8739.4 [7.3.22]	UNACCEPTABLE INSUFFICIENT STRESS RELIEF The placement of cable ties/straps shall not negate strain relief in cables or harnesses. Best Workmanship Practice
ACCEPTABLE TIE/WRAP SPACING Ties are neat, tight and properly spaced (relative to harness diameter) to maintain the wiring in a tight, neat bundle. NASA-STD-8739.4 [9.2], [19.6.1.e.5]	UNACCEPTABLE INCORRECT TIE SPACING Cable ties/wraps have not been properly spaced relative to bundle/harness diameter. NASA-STD-8739.4 [19.6.2.d.7]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 10







电缆和线束通用规范 (cont.)
ACCEPTABLE TIE/WRAP SPACING AT BREAKOUT Lacing or tie wraps have been placed on both sides of the harness breakouts. Ties are neat and tight. NASA-STD-8739.4 [9.6]	ACCEPTABLE UNIFORM CONDUCTOR TENSION The conductors exhibit uniform tension throughout the length of the harness. No bunching, bowing, looping, kinks, etc. NASA-STD-8739.4 [19.6.1.e.3]
ACCEPTABLE UNUSED/SPARE CONDUCTORS Unused or spare conductors shall be terminated by folding the unstripped end back on itself and then sealed with insulation sleeving or wrap. Conductor ends shall be secured to prevent unwanted movement, protrusion or snagging. NASA-STD-8739.4 [19.6.1.e.19]	UNACCEPTABLE DAMAGE CONNECTOR Damage to the connector (i.e.: cuts, gouges, cracks, deformed features, bent pins, exposed base metal, etc.). NASA-STD-8739.4 [19.6.1.e.1]
UNACCEPTABLE DAMAGE INSULATION Damage to the cable jacket, ribbon or conductor insulation (i.e.: cuts, pinching, nicks, scrapes, crazing, crushing, cold flow, exposed conductors, punctures, thinning or burns). NASA-STD-8739.4 [19.6.2.e.9]	UNACCEPTABLE EXPOSED POWER CONTACTS Active signal/live voltages shall be confined to connectors with sockets to preclude the exposure of voltage points when the connector is disconnected. NASA-STD-8739.4 [7.3.18]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 11







电缆和线束通用规范 (cont.)
UNACCEPTABLE IMPROPER BEND RADIUS The harness exhibits a bend radius that is less than the minimum recommended for the conductor type(s) used and overall harness diameter. NASA-STD-8739.4 [7.3.21]	UNACCEPTABLE IMPROPER CABLE TIE/WRAP TENSION Cable tie/wrap tension is too loose, allowing lateral movement along the cable bundle under normal handling. NASA-STD-8739.4 [19.6.2.d.4]
UNACCEPTABLE IMPROPER CABLE TIE/WRAP TENSION Cable tie/wrap tension is too high, resulting in deformation and pinching of the wire insulation. NASA-STD-8739.4 [19.6.2.d.3]	UNACCEPTABLE IMPROPER LACING KNOT The cable lacing has been secured with a bow-knot, rather than a square/non-slip knot. This tie may eventually loosen. NASA-STD-8739.4 [19.6.2.d.4]
UNACCEPTABLE IMPROPER ROUTING Cables and harnesses shall be routed so that they are protected from abrasion, cold flow, cut through, vibration, chafing, flexing and sharp edges. NASA-STD-8739.4 [7.3.14]	UNACCEPTABLE IMPROPER SPLICE GAUGE/SIZE Replacement conductors shall be of the same voltage and current rating as the original conductor. Best Workmanship Practice

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 12







电缆和线束通用规范 (cont.)
UNACCEPTABLE IMPROPER TERMINATION Solder and/or crimped terminations that do not meet the requirements of NASA-STD-8739.3 and/or NASA-STD-8739.4 shall be cause for rejection. NASA-STD-8739.4 [13.1]	UNACCEPTABLE INCOMPLETE COVERAGE OF METAL BRAID Metal braid sleeving shall exhit uniform coverage, to provide electrical and mechanical protection to the underlying harness. NASA-STD-8739.4 [19.6.2.b.8], [19.6.2.e.5]
UNACCEPTABLE INCORRECT LACING MATERIAL Waxed lacing shall not be used for spaceflight applications. NASA-STD-8739.4 [19.6.2.d.2]	UNACCEPTABLE PROJECTING SHIELD STRANDS The shield strands have been improperly dressed, resulting in projecting strands that may result in an electrical short or sharp object (punture/snag) concern. Best Workmanship Practice
UNACCEPTABLE SPLICES IN FLEXURE ZONE Splices shall not be installed in areas where the harness is designed to flex. Best Workmanship Practice	UNACCEPTABLE UNSEALED ENVIRONMENTAL CONNECTOR Sealing plugs or unused pins shall be installed in all unwired/unused holes to retain the environmental rating of the connector. NASA-STD-8739.4 [7.3.19]

美国宇航局工艺标准
	Released: 04.05.2002	Revision:	Revision Date:
	Book: 4	Section: 4.01	Page: 13

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