Abstract: A spacecraft equipment panel including heat pipes operable in a zero-gravity environment for cooling the equipment mounted to the panel is not operable in an Earth-gravity environment because the two-phase working fluid in the heat pipes tends to pool at the bottom of the heat pipe when the heat pipe is vertical. An apparatus and method for overcoming this condition employs infrared lamps positioned on a mounting frame to heat the bottoms of the heat pipes to vaporize the working fluid therein, whereby the heat pipes become operable for transporting heat while in a vertical orientation and under the influence of gravity.

Abstract: A release device is actuated to release a workpiece by operation of either of two elongated shape memory metal alloy (SMMA) members. Each SMMA member has on one end a feature that engages a fitting on the workpiece, while its other end is mounted to a housing. A heater on each SMMA member raises its temperature to a transition temperature at which it returns to an unstressed (e.g. shorter) length, thereby releasing the workpiece. The two SMMA elements may be disposed in opposite directions from the housing or may be coaxial or offset and disposed in the same direction.

Abstract: A thermally-actuated switch includes a pair of switch contacts openable or closeable in response to a change in the length of a shape memory metal (SMM) rod. The SMM rod is caused to change its length by having its temperature increased by heat produced when electrical power dissipated in a heating element that is coupled in electrical circuit with the switch contacts. To this end, the heating element is thermally coupled to the SMM rod, such as by a common heatsink. Where the switch is to be openable, the heating element is preferably in series circuit with the contacts, and where the contacts are closeable, the heating element is preferably in parallel therewith.

Abstract: A structural panel has thin inner and outer facesheets bonded to a lightweight structural interior core of a honeycomb material. The inner facesheet is for receiving equipment that generates heat to be dissipated and the outer facesheet is adapted to dissipate such heat, such as by radiation. A plurality of closely-spaced heat pipes interior to the panel are thermally coupled to each other and to the inner facesheet for receiving heat from the equipment mounted thereon. A plurality of spaced-apart heat pipes interior to the panel are at about right angles to the closely-spaced heat pipes and are thermally coupled to the outer facesheet and to the closely-spaced heat pipes proximate their intersections therewith. Heat to be dissipated flows along short, direct and efficient paths from the equipment to the inner facesheet, to the closely-spaced heat pipes, to the spaced-apart heat pipes and to the outer facesheet from whence it is dissipated.

Abstract: An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The membrane includes at least two dielectric sheets of polyimide film 1 mil thick. The surface of the outer film facing away from the reflector is coated with an electrically semiconductive coating such as vapor-deposited germanium having a thickness in the range of 200 .ANG. to 600 .ANG.. A member, such as a glass fiber mat, may be located in the space between the two dielectric sheets for maintaining the sheets in spaced-apart relationship. In another embodiment of the invention, the surface of the film facing the reflector may be reinforced by an adhesively attached polyester or glass fiber mesh.

Abstract: An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The membrane includes a single dielectric sheet of polyimide film 1 mil thick. The surface of the film facing away from the reflector is coated with a layer of semiconductor material such as vapor-deposited germanium having a thickness in the range of 200 .ANG. to 600 .ANG.. In another embodiment of the invention, the surface of the film facing the reflector may be reinforced by an adhesively attached polyester or glass fiber mesh.

Abstract: A spacecraft adapted for operation in a low inclination angle earth orbit comprises north, south, east and west panels defining a spacecraft interior volume. The north and south panels are oppositely disposed with respect to each other and the east and west panels are oppositely disposed with respect to each other. The spacecraft interior volume generally and preferably lacks structural elements that substantially restrict thermal radiation among the panels. The north and south panels, to which spacecraft equipment is usually mounted, each include conductive heat pipes for reducing the temperature differences across each panel. The exterior surfaces of the north, south, east and west panels have a covering, preferably of optical solar reflectors (OSRs), for radiating thermal energy therefrom, wherein the OSRs have a solar absorptivity that is substantially less than their thermal emissivity.

Abstract: A process and apparatus for making high purity aluminum nitride from organometallic aluminum, such as an alkylaluminum compound. A gaseous alkylaluminum compound and gaseous ammonia are introduced into a heated reaction zone where the gases are mixed and high purity aluminum nitride is produced. The high purity aluminum nitride is collected in the form of a powder or deposited as a thick, dense layer on an appropriate substrate mounted in the reaction chamber. A carrier gas such as hydrogen gas, may be used to conduct the alkylaluminum compound from a suitable reservoir containing liquid alkylaluminum compound to the reaction chamber. A preferred alkylaluminum compound is triethylaluminum.

Abstract: A shape memory alloy (SMA) actuator predeformed in compression actuates a cable cutter mechanism. A cable or other item to be cut is placed between an anvil and a movable blade affixed to the SMA element. The SMA element is heated by an electrical resistance heater to cause it to return to its undeformed elongated state, thereby moving the blade against the anvil to compress and sever the cable or other item. Ones of the shape memory alloy actuator have a plurality of parallelly arranged SMA elements, every other one of which is predeformed in compression and intermediate ones of which are predeformed in tension. The elements are coupled end-to-end so that, when they are heated to cause them to return to their undeformed states, their respective elongations and shrinkages combine at the output to produce an actuation that is the cumulation in the same direction of the changes of all the elements. The plurality of elements may be in a side-by-side or concentric arrangement.

Abstract: A shape memory alloy (SMA) actuator predeformed in tension actuates a separation device mechanism. A segmented nut, which engages a threaded bolt to be held and released, is held together by a nut retainer that is movable with respect to the nut and is affixed to the SMA element. The SMA element is heated by an electrical resistance heater to cause it to return to its undeformed state, thereby moving the retainer relative to the nut segments. When the retainer disengages from the segments, the segments are free to move outwardly thereby releasing the bolt or other item. Ones of the shape memory alloy actuator have a plurality of parallelly arranged SMA elements, every other one of which is predeformed in compression and intermediate ones of which are predeformed in tension.

Abstract: A printed circuit radiating element comprises a geometrically symmetric planar area of a conducting material separated from a ground plane by a dielectric medium. The driving point of the radiating element is at the base of a notch in one side thereof so that the driving impedance is reduced from that obtained when the element is driven at its edge. Symmetrically disposed on opposite sides of an axis of symmetry of the element along which the driving point lies are two notches which restore the electrical symmetry of the radiating element thereby to suppress higher order modes. The suppression of these higher order modes results in a radiation pattern with minimal cross-polarized energy in the principal planes and high port-to-port isolation which could not be achieved with an asymmetrical element. Two driving points may be employed with the radiating element to produce a dual linearly polarized antenna and a reactive combiner or hybrid may be employed to obtain circularly-polarized radiations.

Abstract: An interface circuit includes a generator for driving an interface signal to a receiver which produces an output signal in response thereto. The generator (or driver) includes a pair of relatively larger complementary conductivity field effect transistors and a pair of relatively smaller complementary conductivity field effect transistors (FETs), each pair in series circuit between the supply rails. The interface signal is produced at a connection of the center points of both pairs of FETs. A control device renders like ones of the FETs in each pair alternately conductive responsive to the input signal, however, the control device generates control signals for the FETs such that the relatively smaller FET of a given conductivity becomes conductive before the larger FET of that same conductivity. The receiver includes a voltage divider to attenuating and coupling the received interface signal to a high-gain amplifier which produces the output signal.

Abstract: 102 composition. The coating composition of the present invention is a moisture-curable polymethyl-n-hexylsilsesquioxane having a partially water-hydrolyzed, silane catalyst-containing condensation product of n-hexyltrimethoxysilane and methyltrimethoxysilane, the silane catalyst having at least one aminoalkyl-substituted group and at least one alkoxy-substituted group having at least 2 carbon atoms in the alkoxy group. The silane catalyst is also a co-curing agent and condenses with the n-hexyltrimethoxysilane and the methyltrimethoxysilane.

Abstract: A fuel or fluid level measurement arrangement for a spacecraft includes one or more electromagnetic transmission lines extending into the reservoir. The presence of fuel adjacent the transmission line changes the dielectric constant or loss characteristics of the transmission line(s) in a measurable manner. In one embodiment, strip transmission lines extend parallel to the fluid surface at various degrees of ullage, and the fuel level can be established to within the spacing between the transmission lines.

Abstract: A spacecraft structure for orbital assembly and servicing includes a payload module, a propulsion module and a bus module each of these modules includes attachement means for separately attching to the cargo bay of the Shuttle directly and via planar cradles. The bus module includes module docking and latching fittings at each end and matching locking and latching fittings at one end of each of said payload and propulsion modules. The bus module includes sectionalized assemblies forming a matrix of identical cavities adapted to receive orbital replacement submodules that allow easy replacement of equipment in orbit by an astronaut.

Abstract: A connector for an Orbital Replacement Unit (ORU) includes a screw in an active connector structure which mates with a floating nut in a passive connector structure. Two alignment pins in active structure mate with sockets in the passive structure. As the screw is turned, a push rod assembly in the active structure couples to a one-axis restraint in the passive structure. One alignment pin has a two-axis restraint and the other has a three-axis restraint. The screw is driven manually or by a robot to cooperate with the alignment pins and sockets to provide a three point mount.

Abstract: The invention relates to a connective apparatus between a truss beam and another object, e.g., a second truss beam or another device, for rigidly joining the two together. The connective apparatus comprises a unitary attachment device which is connected to one of the frame elements in a truss beam. The device includes a rabbet member capable of attachment to a pair of struts of the frame element and a connector member attached to the rabbet member. A connector strut is provided for joining two or more truss beams to each other by interconnecting two nodes of the respective beams.

Abstract: An attitude control system using magnetic torquing is enhanced using a momentum wheel which is pivoted if the sensed error signal about the roll axis exceeds a given threshold. The momentum wheel is pivoted under control of a stepping motor through a first angle proportional to the detected average roll error, and one-half nutation period later through an equal angle in the same direction. Alternatively, the momentum wheel is pivoted over first and second angles of different values wherein the difference is related to nutation.

Abstract: A thick film, multi-layer interconnected circuit board includes a substrate of an electrical insulating material which will withstand high temperatures, such as alumina, having over a surface thereof a plurality of stacked layers of a glass dielectric. Between each pair of dielectric layers is a thick film conductor layer. The dielectric layers have openings or vias therethrough which are filled with a conductive material which makes electrical contact with the adjacent conductive layers. A contact pad is over the topmost dielectric layer and is electrically connected to a via conductor material in the topmost dielectric layer. The contact pad is of a thick film conductive material which is a layer of glass having particles of a conductive material, such as a noble metal or mixture of noble metals, dispersed therein. A bonding layer is between the contact pad and the topmost dielectric layer and is bonded to both.

Abstract: A transmitter has an interleaver that sets an interleaving interval in accordance with the fading characteristic of a channel and transmits in another channel. The inteleaver duration is indicated by a synchronization signal and typically is 3 to 10 times the mean time between fades (decorrelation time). If the two channels substantially differ in frequency, a scaling factor can be used. A receiver has an adaptive deinterleaver that has a deinterleaving time in accordance with the synchronization signal occurring at the interleaving interval.