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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 577 records · Page 32

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NASA NTRS1979

High G pyrotechnic shock simulation using metal-to-metal impact

A technique for simulating high g level pyrotechnic shocks is described and the results of applying the technique to obtain the MIL-STD-1540A shock spectrum with a maximum acceleration of 18,000g at 2,000 Hz are presented. Designing the resonant beam and plate on which the test unit is mounted, and generating a proper impulsive load on them, were the essentials of the technique. One dimensional stress wave and Euler equations were employed in the design. A metal pendulum hammer was used to generate the impulsive load.

Bai, M.↗

NASA NTRS1983

Study for analysis of benefit versus cost of low thrust propulsion system

The benefits and costs associated with placing large space systems (LSS) in operational orbits were investigated, and a flexible computer model for analyzing these benefits and costs was developed. A mission model for LSS was identified that included both NASA/Commercial and DOD missions. This model included a total of 68 STS launches for the NASA/Commercial missions and 202 launches for the DOD missions. The mission catalog was of sufficient depth to define the structure type, mass and acceleration limits of each LSS. Conceptual primary propulsion stages (PPS) designs for orbital transfer were developed for three low thrust LO2/LH2 engines baselined for the study. The performance characteristics for each of these PPS was compared to the LSS mission catalog to create a mission capture. The costs involved in placing the LSS in their operational orbits were identified. The two primary costs were that of the PPS and of the STS launch. The cost of the LSS was not included as it is not a function of the PPS performance. The basic relationships and algorithms that could be used to describe the costs were established. The benefit criteria for the mission model were also defined. These included mission capture, reliability, technical risk, development time, and growth potential. Rating guidelines were established for each parameter. For flexibility, each parameter is assigned a weighting factor.

Hamlyn, K. M.↗

NASA NTRS1985

Direct Transient Analysis of a Fuze Assembly by Axisymmetric Solid Elements

A fuze assembly, which consists of three major parts, nose, collar and sleeve, was designed to survive severe transverse impact giving a maximum base acceleration of 20.000 G. It is shown that hoop failure occurred in the collar after the impact. They also showed that by bonding the collar to the nose, the collar was able to survive the same impact. To find out the effectiveness of the bonding quantitatively, axisymmetric solid elements TRAPAX and TRIAAX were used in modelling the fuze and direct transient analysis was performed. The dynamic stresses in selected elements on the bonded and unbonded collars were compared. The peak hoop stresses in the unbonded collar were found to be up to three times higher than those in the bonded collar. The NASTRAN results explained the observed hoop failure in the unbonded collar. In addition, static and eigenvalue runs were performed as checks on the models prior to the transient runs. The use of the MPCAX cards and the existence and contributors of the calculated first several nearly identical natural frequencies are addressed.

Dai, C. C.↗

NASA NTRS1985

Analytical investigation of the dynamics of tethered constellations in Earth orbit, phase 2

This Quarterly Report deals with the deployment maneuver of a single-axis, vertical constellation with three masses. A new, easy to handle, computer code that simulates the two-dimensional dynamics of the constellation has been implemented. This computer code is used for designing control laws for the deployment maneuver that minimizes the acceleration level of the low-g platform during the maneuver.

Lorenzini, E.↗

NASA NTRS1987

Six-Axis Superconducting Accelerometer

Sensitivity and short-term stability high. Design combines superconductivity and magnetic levitation to achieve linear-acceleration sensitivity greater than conventional linear accelerometers, and short-term angular stability better than conventional gyroscopes. Improved accelerometer used to increase precision in inertial navigation and surveying, as sensitive multiple-axis seismic sensor, as component of tensor gravity gradiometer, or to sense accelerations of stabilized platforms or spacecraft.

Paik, Ho Jung↗

NASA NTRS1988

A high voltage power converter for space astronomy applications

A dc-dc low-power, high-voltage converter for use in space is described which furnishes a commandable, low-noise dc output in the range of 0 to -7500 V. The converter is suitable for biasing of detectors commonly employed in space astronomy, microchannel plates, photomultipliers, and gas discharge detectors. The converter's reliability has been demonstrated by accelerated life testing under thermal vacuum. The electrical and mechanical design, packaging, layout and fabrication techniques, and tests employed are described.

Ray, David C.↗

NASA NTRS1989

Guidance, steering, load relief and control of an asymmetric launch vehicle

A new guidance, steering, and control concept is described and evaluated for the Third Phase of an asymmetrical configuration of the Advanced Launch System (ALS). The study also includes the consideration of trajectory shaping issues and trajectory design as well as the development of angular rate, angular acceleration, angle of attack, and dynamic pressure estimators. The Third Phase guidance, steering and control system is based on controlling the acceleration-direction of the vehicle after an initial launch maneuver. Unlike traditional concepts, the alignment of the estimated and commanded acceleration-directions is unimpaired by an add-on load relief. Instead, the acceleration-direction steering-control system features a control override that limits the product of estimated dynamic pressure and estimated angle of attack. When this product is not being limited, control is based exclusively on the commanded acceleration-direction without load relief. During limiting, control is based on nulling the error between the limited angle of attack and the estimated angle of attack. This limiting feature provides full freedom to the acceleration-direction steering and control to shape the trajectory within the limit, and also gives full priority to the limiting of angle of attack when necessary. The flight software concepts were analyzed on the basis of their effects on pitch plane motion.

Boelitz, Frederick W.↗

NASA NTRS1991

One shot methods for optimal control of distributed parameter systems 1: Finite dimensional control

The efficient numerical treatment of optimal control problems governed by elliptic partial differential equations (PDEs) and systems of elliptic PDEs, where the control is finite dimensional is discussed. Distributed control as well as boundary control cases are discussed. The main characteristic of the new methods is that they are designed to solve the full optimization problem directly, rather than accelerating a descent method by an efficient multigrid solver for the equations involved. The methods use the adjoint state in order to achieve efficient smoother and a robust coarsening strategy. The main idea is the treatment of the control variables on appropriate scales, i.e., control variables that correspond to smooth functions are solved for on coarse grids depending on the smoothness of these functions. Solution of the control problems is achieved with the cost of solving the constraint equations about two to three times (by a multigrid solver). Numerical examples demonstrate the effectiveness of the method proposed in distributed control case, pointwise control and boundary control problems.

Taasan, Shlomo↗

NASA NTRS1990

Interoperability among Space Station Freedom data systems - A field test of standards

A development status evaluation is presented for NASA efforts toward the achievement of interoperability among Space Station Freedom (SSF) data systems, despite the complexity created by the number and wide distribution of such systems, the intensive international participation, and the use of time-phased development cycles. Four areas have been identified as essential: communications interoperability, data interoperability, and crew and payload interface interoperability. Accelerated efforts are needed to define and refine detailed interface designs before developments by each of the SSF's international partners come to take fundamentally incompatible courses.

Whitelaw, Virginia A.↗

NASA NTRS1993

Vibration isolation technology: An executive summary of systems development and demonstration

A program was organized to develop the enabling technologies needed for the use of Space Station Freedom as a viable microgravity experimental platform. One of these development programs was the Vibration Isolation Technology (VIT). This technology development program grew because of increased awareness that the acceleration disturbances present on the Space Transportation System (STS) orbiter can and are detrimental to many microgravity experiments proposed for STS, and in the future, Space Station Freedom (SSF). Overall technological organization are covered of the VIT program. Emphasis is given to the results from development and demonstration of enabling technologies to achieve the acceleration requirements perceived as those most likely needed for a variety of microgravity science experiments. In so doing, a brief summary of general theoretical approaches to controlling the acceleration environment of an isolated space based payload and the design and/or performance of two prototype six degree of freedom active magnetic isolation systems is presented.

Grodsinsky, Carlos M.↗

NASA NTRS1993

Vibration isolation technology - An executive summary of systems development and demonstration

Grodsinsky, C. M.↗

NASA NTRS1993

Rarefied-flow shuttle aerodynamics flight model

A model of the Shuttle Orbiter rarefied-flow aerodynamic force coefficients has been derived from the ratio of flight acceleration measurements. The in-situ, low frequency, low level acceleration measurements are made during atmospheric reentry. The experiment equipment designed and used for this task is the High Resolution Accelerometer Package (HiRAP), one of the sensor packages in the Orbiter Experiments Program. To date, 12 HiRAP reentry mission data sets spanning a period of about 10 years have been processed. The HiRAP derived aerodynamics model is described in detail. The model includes normal and axial hypersonic continuum coefficient equations as functions of angle-of-attack, body flap deflection, and elevon deflection. Normal and axial free molecule flow coefficient equations as a function of angle-of-attack are also presented, along with flight derived rarefied-flow transition bridging formulas. Comparisons are made between the aerodynamics model and data from the Orbiter Operational Aerodynamic Design Data Book, and applicable computer simulations and wind-tunnel data.

Blanchard, Robert C.↗

NASA NTRS1922

The NACA Three Component Accelerometer

A new instrument known as the NACA three component accelerometer is described in this note. This instrument was designed by the technical staff of the NACA for recording accelerations along three mutually perpendicular axes, and is of the same type as the NACA single component accelerometer with the addition of two springs and a few minor improvements such as a pump for filling the dash-pots and a convenient method for aligning the springs. This note includes a few records as well as photographs of the instrument itself.

Reid, H J E↗

NASA NTRS1994

Design for dependability: A simulation-based approach

This research addresses issues in simulation-based system level dependability analysis of fault-tolerant computer systems. The issues and difficulties of providing a general simulation-based approach for system level analysis are discussed and a methodology that address and tackle these issues is presented. The proposed methodology is designed to permit the study of a wide variety of architectures under various fault conditions. It permits detailed functional modeling of architectural features such as sparing policies, repair schemes, routing algorithms as well as other fault-tolerant mechanisms, and it allows the execution of actual application software. One key benefit of this approach is that the behavior of a system under faults does not have to be pre-defined as it is normally done. Instead, a system can be simulated in detail and injected with faults to determine its failure modes. The thesis describes how object-oriented design is used to incorporate this methodology into a general purpose design and fault injection package called DEPEND. A software model is presented that uses abstractions of application programs to study the behavior and effect of software on hardware faults in the early design stage when actual code is not available. Finally, an acceleration technique that combines hierarchical simulation, time acceleration algorithms and hybrid simulation to reduce simulation time is introduced.

Goswami, Kumar K.↗

NASA NTRS1994

Micro-measurements of mechanical properties for adhesives and composites using digital imaging technology

The need for a constituent based durability or accelerated life prediction procedure to be used for the engineering design of polymer matrix composites is discussed in the light of current plans for the High Speed Civil Transport (HSCT) concerns about the U.S. infrastructure (bridges, pipelines, etc.) and other technological considerations of national concern. It is pointed out that good measurement procedures for insitu resin properties are needed for both adhesives and composites. A double cantilever beam (DCB) specimen which shows promise for the easy determination of adhesive shear properties is presented and compared with measurements of strains within the bondline using a new optical digital imaging micro-measurement system (DIMMS). The DCB specimen is also used to assess damage in a bonded joint using a dynamic mechanical thermal analysis system (DMTA). The possible utilization of the same DIMMS and DMTA procedures to determine the insitu properties of the resin in a composite specimen are discussed as well as the use of the procedures to evaluate long term mechanical and physical aging. Finally, a discussion on the state-of-the art of the measurement of strains in micron and sub-micron domains is given.

Brinson, Hal F.↗

NASA NTRS1996

Instrument For Simulation Of Piezoelectric Transducers

Electronic instrument designed to simulate dynamic output of integrated-circuit piezoelectric acceleration or pressure transducer. Operates in conjunction with external signal-conditioning circuit, generating square-wave signal of known amplitude for use in calibrating signal-conditioning circuit. Instrument also useful as special-purpose square-wave generator in other applications.

Mcnichol, Randal S.↗

NASA NTRS1996

Template-Directed Ligation of Peptides to Oligonucleotides

Synthetic oligonucleotides and peptides have enjoyed a wide range of applications in both biology and chemistry. As a consequence, oligonucleotide-peptide conjugates have received considerable attention, most notably in the development of antisense constructs with improved pharmacological properties. In addition, oligonucleotide-peptide conjugates have been used as molecular tags, in the assembly of supramolecular arrays and in the construction of encoded combinatorial libraries. To make these chimeric molecules more accessible for a broad range of investigations, we sought to develop a facile method for joining fully deprotected oligonucleotides and peptides through a stable amide bond linkage. Furthermore, we wished to make this ligation reaction addressable, enabling one to direct the ligation of specific oligonucleotide and peptide components.To confer specificity and accelerate the rate of the reaction, the ligation process was designed to be dependent on the presence of a complementary oligonucleotide template.

Bruick, Richard K.↗

NASA NTRS2001

Solar Flares and the High Energy Solar Spectroscopic Imager (HESSI)

Solar flares are the biggest explosions in the solar system. They are important both for understanding explosive events in the Universe and for their impact on human technology and communications. The satellite-based HESSI is designed to study the explosive release of energy and the acceleration of electrons, protons, and other charged particles to high energies in solar flares. HESSI produces "color" movies of the Sun in high-energy X rays and gamma rays radiated by these energetic particles. HESSI's X-ray and gamma-ray images of flares are obtained using techniques similar to those used in radio interferometry. Ground-based radio observations of the Sun provide an important complement to the HESSI observations of solar flares. I will describe the HESSI Project and the high-energy aspects of solar flares, and how these relate to radio astronomy techniques and observations.

Holman, Gordon D.↗