Abstract: A simple, nearly passive apparatus is disclosed that allows a spacecraft sensor to be driven to a potential close to that of a plasma where the ion concentration exceeds about 100 cm.sup.-3 even in the presence of a large vehicle potential. The apparatus includes a conductive reference surface insulated from all spacecraft elements. The reference surface is situated on the spacecraft such that it faces in the direction of motion, and collects ions thereon. There is developed on the surface a plasma potential. The reference surface is connected to the inverting input of an operational amplifier that is powered by floating voltages referenced to the potential at the noninverting input of the amplifier. Since the operational amplifier has to maintain equal voltages at both inputs, the amplifier will drive against spacecraft ground until the voltage at the noninverting input is substantially equal to the voltage at the inverting input.

Abstract: A method of providing lightning protection for non-metallic component structures, aircraft skins, etc. including sandwich-type skins on aircraft where fast removal and easy access is required between components of the lightning protection electrical circuit path. The electrical circuit path between aircraft structures utilizes a flexible clip not requiring fastener connection and removal when a component at the end of the circuit path is required to be replaced.

Abstract: In a composite aircraft formed of graphite reinforced epoxy plates forming walls (14, 16) of the aircraft and walls of fuel tanks (12) therein, for example, there is an adhesive seal (36) for bonding overlapping faying plate surfaces together. The seal (36) is formed of spaced glass fibers (58) impregnated with a resin and with a filler of conductive material (50). The conductive filler is carbon in the form of approximate microspheres (52, 54), generally hollow, and having diameters in the range of 5 to 150 microns. The resin is cured on the faying surfaces after they have been secured together by fasteners (28) coated with a dielectric (30). The carbon microspheres (50) function to weaken the adhesive seal (36) between the plates (16, 22) so that they can be forcibly separated without structural damage to the plates.

Abstract: The invention relates to a method and to a structural element for protecting an aircraft against the building-up, when flying, of electrostatic charges on the external metallic surface of the aircraft normally coated with a finishing dielectric paint.The structural element of the aircraft is subjected to a treatment consisting in applying on the external metallic surface of the aircraft, prior to the depositing of the finishing paint, a resistive electrostatic protection layer having a surface resistivity of between 1 and 100 M.OMEGA. per square and being connected to the reference electric potential (i.e., ground or mass) of the frame or body of the aircraft.The the protective layer is provided, for example, by applying at least a paint layer forming, once dry, a coating exhibiting the required surface resistivity.

Abstract: A carbon fibre or aramid fibre fabric in a matrix of thermoset plastic is coated first with a thin layer of nickel, then with a highly conductive second layer, and on the outside once more with nickel. If the metals are deposited under wet-chemical currentless conditions, the flexible fabric will be electrically highly conductive. The composite material is particularly suitable for lightning and NEMP protection.

Abstract: A lightning diverter strip is provided with button elements in the form of diamond-shaped conducting segments which arranged longitudinally on the strip in spaced-apart relation, with the sharp corners of each of the button conductive elements in longitudinal alignment with each other and with the opposite corners presented along the edges of the strip. The spacings of the conductive elements at the corners may be varied so that some of the elements are spaced more closely together than are other ones of the elements, to provide a lightning diverter strip having a lower break-down voltage potential.

Abstract: Method and structures for enhancing the conductivity of graphite composite materials for lightning protection and prevention of attachment of lightning to fasteners. The integral lightning protection for composite aircraft skins, including skins with fasteners penetrating into fuel tanks, utilizes metal coated or plated graphite fibers which are woven into the outer layer of tape or fabric of the structural component requiring protection.

Abstract: Spacecraft are subject to electron bombardment resulting in electrical charge build-up on dielectric materials, such as thermal blankets, used to control heat gain and loss from the craft. The invention provides a multiple-layer material including inner and outer thermally insulating layers and an intermediate conductive layer, the outer insulating layer having a thickness such that many of the bombarding electrons will come to rest at or near the conductive layer and the resulting charge conducted away. Material may be in the form of a blanket with e.g. Kapton inner and outer layers or in the form of a glass tile. Material is also usable in other situations where electrical charge build-up may be a problem, e.g. for insulating explosive liquid containers.

Abstract: Method and structures for enhancing the conductivity of graphite composite materials for lightning protection and prevention of attachment of lightning to fasteners. The integral lightning protection system for composite aircraft skins, including skins with fasteners penetrating into fuel tanks, utilizes nickel-plated graphite fibers (24) which are woven into the outer layer of fabric of the structural component (10) requiring protection.

Abstract: An ionization-type lightning diverter strip structure having improved environmental edge and tip sealing. Semi-conductive particle edge configurations and particle distribution geometries for improved streamer formation include forward strip and conductive particle termination and particle distribution geometries having variation along the length of the ionization-type lightning diverter strip structures and multilayer particle distribution geometries to resist particle impact erosion (e.g. rain erosion).

Abstract: A flush, zero drag discharger system for dissipating static electric charges from surfaces of high performance aircraft and similar vehicles which is capable of withstanding a severe lightning environment without substantial degradation of the system. The discharger system includes a configuration of the vehicle secondary structure into non-electrically conductive areas, conductive high corona threshold areas, and controlled low corona threshold electrostatic discharge areas which are protected from the detrimental effects of lightning by the utilization of ionization-type lightning diverters.

Abstract: A controlled dielectric barrier is created surrounding a fastener to isolate its sparking areas. The barrier is formed by creating a cap to define a desired cavity between the cap and the fastener and then dielectric isolation material is placed in the cavity and held in place by the cap until hardened. The cap may then be removed from the fastener as desired.

Abstract: A member suitable for use at the exterior surface of an aircraft for structural or containment purposes includes a nonmetallic base or core and a thin electrical shield over that surface of the base that is presented outwardly. Preferably the base is a composite consisting of graphite fibers and a cured resin in which the fibers are embedded. The shield is tin or a tin alloy that is bonded to the surface of the base, preferably by metal spraying techniques. An electrical discharge, such as lightning, that attaches to the member is dissipated through the shield without impairing the strength or containment capabilities of the base.

Abstract: A dielectric film is provided with a metallic back layer for use as the outer layer in a multi layer "thermal blanket" employed as part of the temperature control system for a spacecraft. The dielectric film is repeatedly punctured from the metallized side in order to produce a plurality of small holes, which collect a disproportionately large current from the plasma and adjacent charged surface. The rough edges of these holes also act to initiate frequent, small, field emissions, thereby preventing large surface potentials from building up in the presence of a "hot" space plasma or electron beam environment.

Abstract: Passive and active devices reduce stored electrostatic charge levels on dielectric surfaces, while at the same time reducing electromagnetic interference due to streamer currents, by means of appropriately applied conductors, use of direct or alternating current power sources, ion flooding, fluid flooding and boundry layer control. In addition, the devices detect the presence, polarity and magnitude of triboelectric charging or stored charges on a dielectric surface for the purpose of signalling or of controlling active charge reduction devices. Moreover, the devices can be used to discourage lightning strikes. The devices can be applied with little if any impairment to optical or radio frequency energy transmission or reception.

Abstract: Apparatus for removing electrostatic charge from an aircraft windscreen includes a conductive member arranged to be supported in contact with or in juxtaposition to the windscreen and connected to the aircraft "earth". If in contact, the member may be of conductive rubber. If juxtaposed, it may be of metal or other rigid material. The linkage supporting the member is arranged to allow it to be swept over the windscreen surface to clear an extended area thereof of charge.

Abstract: Construction parts are protected against lightening by a layer which releases a cloud of ionized and ionizable particles to spread the area affected by the lightening flash and to fan out the current path. The layer may include additives which swell when heated to increase the volume and density of the cloud. An electrically and thermal conductive layer or two such layers each having predominantly one of these properties is provided underneath the releasing layer.

Abstract: Electrical apparatus and power distribution systems are protected from lightning strike currents and voltages by the addition of mutually coupled chokes, such as bifilarly wound chokes, in electrical series relationship with the apparatus and the power distribution system to increase the impedance therebetween and cause lightning currents to flow along alternate current paths.

Abstract: An electrostatic discharge system for neutralizing the charge accumulated an aircraft utilizes a pair of unequal length probes to sense the intensity of the external electric field. A transformer arrangement energizes these probes with out-of-phase voltages such that the corona currents flow in opposite directions through these probes. The dual probe configuration eliminates any errors due to environmental changes, while the out-of-phase excitation mode allows the AC component of the output signal to be canceled at a load resistor in the sensor circuit by a subtractive process, a feature which greatly simplifies the filtering operation.

Abstract: Lightning protection means for aircraft structural components includes thin, perforated, dielectric and metallic layers applied to the ordinarily lightning-accessible surfaces of composite structures. Where the outer metallic layer of the lightning protection means is formed from sprayed metal, ground connection means to the metallic layer preferably comprises a section of wire screen fused with the sprayed metal on the dielectric layer, a thin metal plate brazed to the wire screen, and a metal attachment connecting the metal plate to adjacent ground structure. Composite-to-metal or composite-to-composite structural joints are protected by making the entire bonded and bolted interface areas conductive for transfer of lightning current, or by isolating the bonded interface area to control the transfer path of the lightning current through the bolted interface area only.

Abstract: A cylindrical discharge manifold for an electrostatic gas-dynamic discharge ystem in a helicopter comprising four symmetrically positioned air outlets set in the end of a tubular manifold casing which protrudes out from the helicopter fuselage. The outlets connect to a central high-velocity air-stream inlet pipe in the casing by way of a plurality of air passages extending radially outward from the central inlet pipe. This manifold design insures a symmetrical air distribution, significantly reduces drag pressure on the aircraft, and obviates the requirement for "Y" air hose connections.

Abstract: A potential induced on the surface of an orbiting spacecraft is neutralized to the potential of a plasma through which the spacecraft is traveling by directing charged particles into the plasma from the spacecraft surface. The induced potential occurs in response to bombardment of the spacecraft surface by ambient charged particles which may be negative or positive. The charged particles directed into the plasma from the surface have the same polarity as the induced potential to provide the neutralization. The invention can be utilized to maintain different, electrically isolated segments of a spacecraft surface at the same potential to prevent electric discharges between the different parts and thereby protect electric circuits within the spacecraft. The invention can also be utilized to enable charged particle detectors on the surface of a spacecraft to operate more accurately so that the particles are not perturbed by a potential difference between the spacecraft surface and the plasma.

Abstract: A process and structure are described for protecting objects from the damaging effects of electrical discharges by employing a coating of a conductive, ablative material such as graphite. Upon occurrence of an intense electrical discharge to this material, it evaporates to dissipate the heat produced by the discharge and protect the structural integrity of the object.