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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 631 records · Page 35

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NASA NTRS1971

Study program of NASA/GSFC weld quality monitor system

The Weld Quality Monitor has provided online control through the application of linear transducers. The electronic systems must be upgraded to increase confidence level required in production. The Weld Quality Monitor has been used with a recent model solid state power supply to evaluate ability to differentiate between sound and defective weld joints. The Weld Quality Monitor has been evaluated on Dumet and Kovar to interconnect materials Nickel and Alloy 180 in weld joints used on microelectronic module fabrication. Distinct separation was achieved between low strength welds and sound welds by the Quality Monitor. Evaluation performed indicates a drift level at less than 2 percent on a series of 50 consecutive welds. Operation under shop conditions identified need for controlled electrode impact. This was achieved with pneumatic actuation.

Hutchinson, W. R.↗

NASA NTRS1971

Monolithic parallel processor, phase 1A

A four-bit parallel processor LSI array was designed and fabricated using COS/MOS integrated-circuit technology. The design features include the provision for interconnecting groups of parallel-processor chips to form an expanded processor of any desired word length. This 800-transistor "computer on a chip' circuit has the logic capability of a medium-size, medium-speed, general-purpose computer suitable for sophisticated scientific data processing. The ability to fabricate this device repetitively was demonstrated.

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NASA NTRS1971

Development of nondestructive testing techniques for plated-through holes in multilayer printed circuit boards

The development of a nondestructive test with the capability to interrogate plated-through holes as small as 0.51 millimeters inside diameter is discussed. The system can detect defects such as holes, voids, cracks, and thin spots that reduce the current carrying capability of plates-through interconnects by 20 percent or more. Efforts were directed toward the design and fabrication of magnetic circuitry mutual coupling probes and to evaluate the effectiveness of these devices for detecting in multilayer board plated-through holes.

Anthony, P. L.↗

NASA NTRS1971

Attitude stability of spinning flexible spacecraft

The stability of spinning flexible satellites in a force-free environment was analyzed. The satellite was modeled as a rigid core having attached to it a flexible appendage idealized as a collection of particles (point masses) interconnected by springs. Both Liapunov and Routh-Hurwitz stability procedures are used. In the former, the Hamiltonian of the system, constrained through the angular momentum integral so as to admit complete damping, is used as a testing function. Equations of motion are written using the hybrid coordinate formulation, which readily accepts a modal coordinate transformation ultimately allowing truncation to a level amenable to literal stability analysis. Closed form stability criteria are generated for the first mode of a restricted appendage model lying in a plane containing the system center of mass and orthogonal to the spin axis. The effects of spin on flexible bodies are discussed by considering a very elementary particle model. Control of passively unstable spacecraft is briefly considered.

Likins, P. W.↗

NASA NTRS1971

Apollo 11 Mission Report, Supplement 5: Performance of Lunar Module Reaction Control Systems

Spacecraft velocity data and crew reports indicated that RCS engine performance was nominal. It is estimated that the RCS engines accumulated a total of 1060 seconds on-time and 12,000 firings during the mission. The quad temperatures ranged from 132 to 232 F during the period when the heaters were active, within predicated ranges. The total propellant consumption from the RCS tanks was about 319 pounds, compared to a predicted value of 253 pounds. An additional 69 pounds of propellant were used from the ascent propulsion system tanks during interconnect feed operations associated with APS lift-off, following periods of rapid propellant usage. The only problems noted were two thrust chamber pressure switch failures on the quad one down-firing engine and on the quad 2 aft-firing engine. Engine performance was nominal on both engines, and the switch failures had no effect on the mission.

Blevins, D. R.↗

NASA NTRS1972

Data compression/error correction digital test system. Appendix 1: Operation

The DC/EC operating instructions are provided for anticipated operating conditions. The instructions are supported by illustrations and tables for the controls and indication of radiation-built equipment. The transmitter control panel provides a functional representation of the system configuration. Inputs and outputs of functional units are brought to jacks on the panel for interconnection and monitoring, and to allow independent use of subsystems of the transmitter.

Source record↗

NASA NTRS1972

The 110 watt per kilogram lightweight solar array system

This ultralightweight solar array system is applied to three generic mission types: (1) interplanetary, (2) geosynchronous, and (3) manned space station. The requirements of each of these missions, as they pertain to the solar array, are presented. Existing lightweight solar array system concepts are reviewed, along with conclusions regarding the applicability of this technology to the feasibility of the ultralightweight solar array system. Several system concepts are included for further evaluation. The existing technology base, as it pertains to solar cells, solar cell covers, interconnects and substrates, and deployable booms, is reviewed. The attitude control of spacecraft with large flexible solar arrays is also discussed.

Shepard, N. F.↗

NASA NTRS1971

The X-ray corona and the photospheric magnetic field.

Soft X-ray photographs of the solar corona have been obtained on four flights of a rocket-borne grazing incidence telescope having a resolution of a few arc sec. The configuration of the X-ray emitting structures in the corona has been compared to the magnetic field distribution measured by photospheric longitudinal magnetograms. The X-ray structures trace the three-dimensional configuration of the magnetic field through the lower corona. Active regions in the corona take the form of tubular structures connecting regions of opposite magnetic polarity within the same or adjacent chromospheric active regions. Higher, larger structures link widely separated active regions into complexes of activity covering substantial fractions of the disk. The complexes are separated by areas of low average field in the photosphere. Interconnections across the solar equator appear to originate over areas of preceding polarity.

Krieger, A. S.↗

NASA NTRS1971

Thermal excursion can cause bond problems.

The purpose of this paper is to illustrate the failure mode caused by thermal deformation and how thermal deformation affects bond integrity. Wege bonding in small-signal transistors, microcircuits and LSI circuits is the subject of this work. Repeated switching of the devices between high and low power at a rate that allows thermal expansion and contraction in the interconnecting wire causes the wire to flex at the point of reduced cross-sectional area until finally the wire breaks due to metal fatigue. It was observed that the thermal deformation was related to many factors such as device power dissipation, current density in the wire, wi *e dress and length, thermal time constant and frequency of operation.

Nowakowski, M. F.↗

NASA NTRS1971

A method for attitude control of a satellite in circular orbit by actively varying its inertia.

Equations are developed for a vehicle consisting of a system of particles which move in a generally prescribed fashion. These equations are then specialized to apply to a rigid vehicle with a constant amount of fluid contained in tanks and flowing through interconnecting lines. Various simplifications and specialized forms of the equations are derived, and relationships between mass and inertia that result from the fluid transfer logic and the physical constraints of the configuration are formulated. A tank arrangement and fluid transfer logic are devised which permit each vehicle product of inertia to be varied without varying the remaining elements of the inertia matrix or shifting the center of mass. Vehicle control is achieved by sensing angular rate and the local vertical and by transferring fluid as a function of these variables.

Clarke, W. D.↗

NASA NTRS1972

Description of electrical networks using wiring operators.

A scheme is presented for describing the interconnection of elements and subnetworks into networks by means of 'wiring operators.' This scheme is algebraic and is intended for conversing with computers. It is especially suitable for two-ports such as amplifiers, filters, microwave networks, and in general, transmission-type networks with an input and an output. The algebra is direct, convenient, and versatile. Each of the wiring operators corresponds to a specific set of calculations on the parameters of the networks involved.

Penfield, P., Jr.↗

NASA NTRS1972

Low frequency damping mechanisms in mechano-acoustical networks.

The response of a panel or window to the sonic boom and to other transient loads can often be found by deriving an equivalent lumped parameter model for the structure. The maximax response of such a mechano-acoustical system depends strongly upon the damping mechanisms of the components. This paper is concerned with finding realistic values for the lower bounds of the damping mechanisms in various mechano-acoustical systems. The results indicate that although part of the damping consists of radiation losses at openings, and radiation and viscous losses at narrow interconnecting hallways, the structural damping of the panel is of primary concern.

Seshadri, T. V.↗

NASA NTRS1972

Finite element appendage equations for hybrid coordinate dynamic analysis.

The increasingly common practice of idealizing a spacecraft as a collection of interconnected rigid bodies to some of which are attached linearly elastic flexible appendages leads to equations of motion expressed in terms of a combination of discrete coordinates describing the arbitrary rotational motions of the rigid bodies and distributed or modal coordinates describing the small, time-varying deformations of the appendages: such a formulation is said to employ a hybrid system of coordinates. In the present paper the existing literature is extended to provide hybrid coordinate equations of motion for a finite element model of a flexible appendage attached to a rigid base undergoing unrestricted motions and some of the advantages of the finite element approach are noted. Transformations to the modal coordinates appropriate for the general case are provided.

Likins, P. W.↗

NASA NTRS1971

Silicon solar cell interconnectors for low temperature applications.

Discussion of the design and techniques of solar cell interconnections meeting the requirements of mission life expectancies of 5 to 10 years in the face of the vibration stresses of launch and the stresses induced (especially between dissimilar materials with different thermal coefficients of expansion) by thermal cycling throughout the mission. Generalized stress equations are developed that give the minimum stress relief loop dimensions for a 'no fatigue' interconnector. Also, the thermal expansion stresses induced at the metal-to-silicon interface were investigated and generalized equations developed for determining the stresses in each of the members. These relationships, as verified by experimental tests, can be used to determine the maximum allowable interconnector thickness for failure prevention in thermal cycling environments.

Ralph, E. L.↗

NASA NTRS1972

Stability of large-scale systems with stable and unstable subsystems.

The purpose of this paper is to develop new methods for constructing vector Liapunov functions and broaden the application of Liapunov's theory to stability analysis of large-scale dynamic systems. The application, so far limited by the assumption that the large-scale systems are composed of exponentially stable subsystems, is extended via the general concept of comparison functions to systems which can be decomposed into asymptotically stable subsystems. Asymptotic stability of the composite system is tested by a simple algebraic criterion. With minor technical adjustments, the same criterion can be used to determine connective asymptotic stability of large-scale systems subject to structural perturbations. By redefining the constraints imposed on the interconnections among the subsystems, the considered class of systems is broadened in an essential way to include composite systems with unstable subsystems. In this way, the theory is brought substantially closer to reality since stability of all subsystems is no longer a necessary assumption in establishing stability of the overall composite system.

Grujic, Lj. T.↗

NASA NTRS1972

Shielded silicon gate complementary MOS integrated circuit.

An electrostatic shield for complementary MOS integrated circuits was developed to minimize the adverse effects of stray electric fields created by the potentials in the metal interconnections. The process is compatible with silicon gate technology. N-doped polycrystalline silicon was used for all the gates and the shield. The effectiveness of the shield was demonstrated by constructing a special field plate over certain transistors. The threshold voltages obtained on an oriented silicon substrate ranged from 1.5 to 3 V for either channel. Integrated inverters performed satisfactorily from 3 to 15 V, limited at the low end by the threshold voltages and at the high end by the drain breakdown voltage of the n-channel transistors. The stability of the new structure with an n-doped silicon gate as measured by the shift in C-V curve under 200 C plus or minus 20 V temperature-bias conditions was better than conventional aluminum gate or p-doped silicon gate devices, presumably due to the doping of gate oxide with phosphorous.

Lin, H. C.↗

NASA NTRS1973

Synchro phase selector aid

Phase selector permits multiple leads of synchro devices to be randomly connected while proper interconnections are determined by operating selector switches. Operation of these switches varies both phase and rotation relationship of synchro devices.

Austin, F. H.↗

NASA NTRS1973

A closed, digital telephone system

Digital system can accommodate sixteen or more telephone or data units and eight, simultaneous two-way conversations through only four interconnecting wires. It uses fewer circuit components, is not bulky or complex, and requires no central exchange control.

Monford, L. G., Jr.↗