Abstract: To reduce the time required to build spacecraft, and to reduce costs, the spacecraft are members of a set of spacecraft. Each member has the same structural members, such as panels, but different members of the set are elongated by multiples of an increment such as five inches. The structural panels of larger members of the set are elongated in the longitudinal direction, to provide more surface area for mounting payload, and to provide more heat rejection surface. The propellant tank(s), which may be fuel and oxidizer tanks, are spherical in the shortest members of the set, and are increased in length by addition of cylindrical sections, to provide greater volume in larger members to thereby provide longer operating life. Similarly, the solar panels, heat pipes and the like may be elongated.

Abstract: A pitch momentum stabilized spacecraft includes an earth sensor for generating roll signals. The roll signals are applied to torquers for proportional (P) or proportional-integral PI control of roll and yaw. According to the invention, the sensed roll signals are bandpass filtered at the orbit rate, phase adjusted and applied to the roll and yaw torquers for closing a high gain degenerative feedback loop at the orbit rate, which reduces orbit-rate components of roll and yaw. A second bandpass filter at the second harmonic of the orbit rate is also connected to the earth sensor, for producing second harmonic signals, which are phase controlled and summed with the fundamental orbit rate signals, for degeneration of attitude perturbations occurring at twice the orbit frequency.

Abstract: The invention lies in a support transition which is affixed to a spacecraft for supporting the spacecraft on a support ring of a booster or launch vehicle. The transition is in the general form of a ring defining a longitudinal axis parallel to the axis of the spacecraft and the booster. The transition has a circular end adapted to mate with the booster support ring, and a polygonal end adapted to mate with the spacecraft, and makes a smooth transition between ends. The circumference of the transition, at any cross-section transverse to the longitudinal axis, is constant. The transition is advantageously made of a composite material such as fiber-reinforced solidified liquid or carbon-fiber reinforced resin. In a particular embodiment, the polygonal end is a square rectangle, with four straight sides and rounded corners. In a set of spacecraft, the transition remains the same size.

Abstract: A vibration suppression system senses undesired mechanical motion of a body, and continuously drives a proof mass actuator system to reduce disturbances. An inertial or relative displacement sensor is processed to determine the energy content of the motion, and a correction signal is generated which is summed with the actuator drive signal to minimize the sensed motion energy. The position of the proof mass is sensed, and processed by differentiating and scaling, and the processed proof mass position signal is also summed with the actuator drive signal. The system causes the proof mass actuator loop natural frequency to tend to track the frequency associated with the maximum vibrational energy.

Abstract: A unified spacecraft attitude control system includes a memory aboard the spacecraft, in which a linear transformation matrix [.alpha.] is stored, which includes information identifying pseudo-complementary pairs of thrusters, and the characteristics of each pseudo-complementary pair. During each control cycle of the spacecraft attitude control system, the error signal is multiplied by a gain representing a desired slew rate to form pulse-width signals {pw} for the pseudo-complementary paired thrusters. An augmented pulse-width vector matrix {PW} is formed by transformations, to eliminate negative values of pulse width. The actual thruster pulse widths {.DELTA.t} are calculated as {.DELTA.t}=[.alpha.]{PW}. The thrusters are energized by limited values of {.DELTA.t}.

Abstract: According to the invention, a two-dimensional active antenna array, operating at a number of different frequencies, is used to achieve directivity in two orthogonal planes, thereby providing a more constrained beam "footprint". The array includes a larger number of amplifiers than a line array, thereby increasing the total power which can be combined in space, to further increase the power in the footprint. For transmission, each of the information channels at a different frequency is applied, as in the prior art, to a different power divider array, each of which may be on a separate board. Power-divided signal from each of the information signal channels is applied to an N-input, M-output power combiner arrangement or board, which combines the signals. Each N.times.M power combiner arrangement includes N.times.M nodes. Each node represents the junction or crossing of one input and one output signal transmission path.

Abstract: An inductor uses high temperature superconductors in order to obtain high Q for high frequency operation. The superconductors are applied as thin films to substrates. In some embodiments, superconductor thin films are applied to opposite sides of the same substrate. Superconductive thin films are applied outside the magnetic field establishing superconductive thin films in order to shield against leakage of the magnetic field beyond the inductor. The inductor is connected to a capacitor to realize a resonant circuit used in a power conversion system.

Abstract: An apparatus and method for fastening together spacecraft panels includes the use of fastener pairs, one of which has preformed therein an aperture which is larger in diameter than the body of a tolerance takeup piece which is to pass therethrough. A washer which takes up the clearance is adhesively fastened to one of the fastener halves, and allowed to cure while the panels are in their desired position. Thus, a high-tolerance mating pair can be finalized in position at a late state in fabrication, without undesirable drilling or reaming. In a first particular embodiment, a flat washer, having an inside diameter which closely fits the corresponding bolt, is adhesively fastened over the preformed oversize aperture of a fitting.

Abstract: An inorganic paint suitable for harsh environments, and particularly suitable as a thermal control coating for spacecraft, includes a mixture of 50% or more dry weight barium titanate (BaTiO.sub.3) pigment powder with a binder of an alkali metal silicate such as potassium silicate K.sub.2 SiO.sub.3 or sodium silicate Na.sub.2 SiO.sub.3. Instead of alkali metal silicate binder, a glass frit may be used, which when fused binds the pigment to the substrate. The coefficient of thermal expansion of the pigment is about 12.times.10.sup.-6 /.degree.C. The coefficient of thermal expansion of the paint is moved toward the coefficient of expansion of the substrate by addition of a filler consisting of magnesia to increase the paint's coefficient of expansion, or alumina and/or silica to decrease the paint's coefficient of expansion. The paint survives harsh environments, ultraviolet radiation and a fluence of charged particles, while maintaining a low solar absorptance and high thermal emittance.

Abstract: Cylindrical battery cell vessels are coupled together in plural sets by pairs of half-shell sleeves. The sleeves conduct heat preferentially in an axial direction. Each sleeve set is mounted onto a heat rejection plate for direct radiation to space. Each satellite of a set of spacecraft has a North and/or South-facing region for mounting the heat rejection plates of the requisite number of cells. Each plate may be fitted with an optical solar reflector (OSR) for reflecting insolation, and for radiating heat energy.

Abstract: A satellite attitude control system is usable in the absence of any inertial yaw attitude reference, such as a gyroscope, and in the absence of a pitch bias momentum. Both the roll-yaw rigid body dynamics and the roll-yaw orbit kinematics are modelled. Pitch and roll attitude control are conventional. The model receives inputs from a roll sensor, and roll and yaw torques from reaction wheel monitors. The model produces estimated yaw which controls the spacecraft yaw attitude. The model further produces estimates of the constant component of the disturbance torques for compensation thereof.

Abstract: Two variable frequency, fixed bandwidth bandpass 10, 410 are cascaded to form a bandpass filter with variable center frequency and variable bandpass. Each filter 10, 410 includes first (16, 416) and second (24, 424) mixers separated by a fixed bandpass filter (20, 420). Each mixer includes a control input terminal 30, 32: 430, 432 which receives a control signal (f.sub.LO, f.sub.OFF). The center frequency of the filter arrangement is controlled by the frequency of control signal f.sub.LO, and the bandwidth is controlled by the difference frequency between f.sub.LO and f.sub.OFF. A tracking arrangement 456 allows direct control of the bandpass by control of the frequency of an offset oscillator 458.

Abstract: A high-frequency, low-profile transformer having at least one pair of magnetic poles includes a primary winding having a z-folded, continuous primary conductive film with a generally serpentine configuration disposed on a primary dielectric membrane and further includes a z-folded, continuous secondary winding constructed from a plurality of secondary conductive film portions disposed on a secondary dielectric membrane. Each of the secondary conductive film portions is configured to form a single continuous path enclosing each of the magnetic poles in such manner that each path encloses one pole of each pair of the magnetic poles of each adjacent layer of the secondary winding. Each path thus continues along a respective fold of the winding stack. The secondary winding layers are interleaved with the primary winding layers and electrically connected together.

Abstract: Cyanate ester polymer articles, particularly fiber-reinforced, are metallized by electroless deposition preceded by a series of pretreatment steps which improve adhesion of the metal layer or layers. Said steps include aqueous alkali followed by nitric acid treatment. They preferably also include an initial alkaline permanganate treatment, preferably preceded by aqueous alkali.

Abstract: A multichannel communication system carries signals having a different frequency range in each channel. In order to achieve a particular output power level from each channel, an amplifier is associated with each channel to boost the signal level. For reliability, a switching arrangement switches amplifiers among the channels in accordance with a priority, or substitutes a redundant amplifier for a degraded or failed unit in a channel. The amplifier is subject to distortion at the desired output level, and is cascaded with a distortion equalizer or linearizer for reducing the total distortion. In accordance with the invention, each distortion equalizer is fixedly connected in one channel, and is optimized for the relatively narrow frequency range of that channel, rather than being switched together with the amplifier and being optimized over the total or cumulative bandwidth of all the channels.

Abstract: An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The blanket includes a single dielectric sheet of polyimide film 1/2-mil thick. The surface of the film facing away from the reflector is coated with a transparent electrically conductive coating such as vapor-deposited indium-tin oxide. The surface of the film facing the reflector is reinforced by an adhesively attached polyester or glass mesh, which in turn is coated with a white paint. In a particular embodiment of the invention, polyurethane paint is used. In another embodiment of the invention, a layer of paint primer is applied to the mesh under a silicone paint, and the silicone paint is cured after application for several days at room temperature to enhance adhesion to the primer.

Abstract: An antenna suited for a communications satellite includes two separately located, mutually orthogonally polarized feed antennas such as vertically and horizontally polarized linear horns. The horns feed an active reflector antenna array. The array includes a plurality of mutually orthogonally polarized antenna elements such as crossed dipoles or square patch antenna with cross feeds for two independent orthogonal polarizations. The feeds of the antenna elements are coupled to amplifier modules. Each module includes a circulator for each polarization, coupled to a processor including a low noise amplifier, controlled phase shifter, variable gain amplifier and power amplifier. The output of the power amplifier feeds the antenna element through the circulator. The large number of radiating elements allows high power using power amplifier with relatively modest capabilities.

Abstract: A zero-dB hybrid or directional coupler includes a first through waveguide extending between first and third ports and a second through waveguide, parallel to the first waveguide, and extending between second and fourth ports. A plurality of branch waveguides extend between the first and second through waveguides, and are adjusted to couple signal from the first port only to the fourth port, and from the second port only to the third port (within in limits of systems isolation). Particular normalized branch line impedances provide best operation. A communication system especially adapted for use as a spacecraft uses a zero-dB coupler in a "planar" waveguide system to transpose or "crossover" the positions of two system ports, whereby the physical positions of the various ports are arranged in the same relation as their phase progression.

Abstract: A spacecraft includes bipropellant and monopropellant engines or thrusters. The oxidizer-fuel mixture ratio of the bipropellant engine is not known exactly. The spacecraft is loaded with only sufficient oxidizer to achieve the velocity for transfer from an intermediate orbit to geosynchronous orbit if the mixture ratio is nominal. Therefore, more fuel can be loaded. If the bipropellant engine burn is nominal, there is no excess oxidizer when on-orbit and more fuel is available for stationkeeping. If the burn is oxidizer-rich, there is a velocity shortfall, which is made up by firing monopropellant engines. If the burn is oxidizer-lean, the geosynchronous orbit is achieved with a load of excess oxidizer, which must be moved during each stationkeeping maneuver. A net gain of stationkeeping time results in any of the three mixture ratio cases by comparison with loading of sufficient oxidizer for a full bipropellant burn under worst-case mixture conditions.

Abstract: Arrays of helical antennas are desired for operation at spaced-apart frequencies, such as 1.5 and 2.5 GHz. In order to reduce mutual coupling between the antenna elements of the lower-frequency array, they are spaced apart by more than .lambda.. Grating lobes occur due to the spacing. The lengths of the lower-frequency helices are adjusted to move the nulls in their radiation patterns into congruence with the unwanted peaks of the array pattern, thereby suppressing the grating lobes. In order to reduce the total area of the combined arrays, the higher-frequency antennas of the second array are interleaved with the elements of the first array. At the higher frequency, the antenna elements of the second array are spaced apart even further, in terms of wavelength, than the elements of the first array, so mutual coupling of the antennas of the second array is reduced even more than in the first array.