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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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NASA NTRS1985

Wind measurements with the High Resolution Doppler Imager (HRDI)

The Upper Atmosphere Research Satellite (UARS), to be launched in 1989, is to provide a global data set required to understand the mechanisms controlling upper atmosphere structure and processes, as well as the response of the upper atmosphere to natural and human perturbations. The High Resolution Doppler Imager (HRDI) is the primary instrument for measuring the dynamics of the stratosphere and mesosphere. The goal of HRDI is to measure wind velocities in the stratosphere and mesosphere during the day and the mesosphere and thermosphere at night with an accuracy of 5 m/sec. HRDI will determine winds by measuring Doppler shifts of atmosphere absorption and emission features. Line of sight winds will be taken in two directions, thus allowing the wind vector to be formed. The HRDI instrument is overviewed. The basis of the measurement is explained, as is an outline of the instrument. Since neither instrument nor observational techniques is fully mature, only a brief sketch is presented.

Skinner, W. R.↗

NASA NTRS1995

Neural-Network Controller For Vibration Suppression

Neural-network-based adaptive-control system proposed for vibration suppression of flexible space structures. Controller features three-layer neural network and utilizes output feedback. Measurements generated by various sensors on structure. Feed forward path also included to speed up response in case plant exhibits predominantly linear dynamic behavior. System applicable to single-input single-output systems. Work extended to multiple-input multiple-output systems as well.

Boussalis, Dhemetrios↗

NASA NTRS1999

Smagglce: Surface Modeling and Grid Generation for Iced Airfoils: Phase 1 Results

SmaggIce (Surface Modeling and Grid Generation for Iced Airfoils) is a software toolkit used in the process of aerodynamic performance prediction of iced airfoils with grid-based Computational Fluid Dynamics (CFD). It includes tools for data probing, boundary smoothing, domain decomposition, and structured grid generation and refinement. SmaggIce provides the underlying computations to perform these functions, a GUI (Graphical User Interface) to control and interact with those functions, and graphical displays of results, it is being developed at NASA Glenn Research Center. This paper discusses the overall design of SmaggIce as well as what has been implemented in Phase 1. Phase 1 results provide two types of software tools: interactive ice shape probing and interactive ice shape control. The ice shape probing tools will provide aircraft icing engineers and scientists with an interactive means to measure the physical characteristics of ice shapes. On the other hand, the ice shape control features of SmaggIce will allow engineers to examine input geometry data, correct or modify any deficiencies in the geometry, and perform controlled systematic smoothing to a level that will make the CFD process manageable.

Vickerman, Mary B.↗

NASA NTRS1997

Aeroservoelastic and Structural Dynamics Research on Smart Structures Conducted at NASA Langley Research Center

An overview of smart structures research currently underway at the NASA Langley Research Center in the areas of aeroservoelasticity and structural dynamics is presented. Analytical and experimental results, plans, potential technology pay-offs, and challenges are discussed. The goal of this research is to develop the enabling technologies to actively and passively control aircraft and rotorcraft vibration and loads using smart devices. These enabling technologies and related research efforts include developing experimentally-validated finite element and aeroservoelastic modeling techniques; conducting bench experimental tests to assess feasibility and understand system trade-offs; and conducting large-scale wind tunnel tests to demonstrate system performance. The key aeroservoelastic applications of this research include: active twist control of rotor blades using interdigitated electrode piezoelectric composites and active control of flutter, and gust and buffeting responses using discrete piezoelectric patches. In addition, NASA Langley is an active participant in the DARPA/Air Force Research Laboratory/NASA/Northrop Grumman Smart Wing program which is assessing aerodynamic performance benefits using smart materials.

McGowan, Anna-Maria Rivas↗

NASA NTRS2005

Management of Vortices Trailing Flapped Wings via Separation Control

A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management via separation control. Passive control was achieved by means of a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressure ports, was used to predict vortex characteristics by means of inviscid rollup relations. Furthermore, vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over both outboard and inboard edge vortices while producing negligible lift excursions. Dynamic separation and attachment control was found to be an effective means for dynamically perturbing the vortex from arbitrarily long wavelengths down to wavelengths less than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

Greenblatt, David↗

NASA NTRS2001

Dynamical networks with topological self-organization

Coupled evolution of state and topology of dynamical networks is introduced. Due to the well organized tensor structure, the governing equations are presented in a canonical form, and required attractors as well as their basins can be easily implanted and controlled.

neural net architecture self organizing feature ma↗

NASA NTRS2006

Managing Flap Vortices via Separation Control

A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management by means of boundary layer separation control. Passive control was achieved using a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressures, was used to predict vortex characteristics based on inviscid rollup relations and vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over either outboard or inboard edge vortices while producing small lift and moment excursions. Unsteady surface pressures indicated that dynamic separation and attachment control can be exploited to perturb vortices at wavelengths shorter than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

Greenblatt, David↗

NASA NTRS2007

Advanced NASA Earth Science Mission Concept for Vegetation 3D Structure, Biomass and Disturbance

Carbon in forest canopies represents about 85% of the total carbon in the Earth's aboveground biomass (Olson et al., 1983). A major source of uncertainty in global carbon budgets derives from large errors in the current estimates of these carbon stocks (IPCC, 2001). The magnitudes and distributions of terrestrial carbon storage along with changes in sources and sinks for atmospheric C02 due to land use change remain the most significant uncertainties in Earth's carbon budget. These uncertainties severely limit accurate terrestrial carbon accounting; our ability to evaluate terrestrial carbon management schemes; and the veracity of atmospheric C02 projections in response to further fossil fuel combustion and other human activities. Measurements of vegetation three-dimensional (3D) structural characteristics over the Earth's land surface are needed to estimate biomass and carbon stocks and to quantify biomass recovery following disturbance. These measurements include vegetation height, the vertical profile of canopy elements (i.e., leaves, stems, branches), andlor the volume scattering of canopy elements. They are critical for reducing uncertainties in the global carbon budget. Disturbance by natural phenomena, such as fire or wind, as well as by human activities, such as forest harvest, and subsequent recovery, complicate the quantification of carbon storage and release. The resulting spatial and temporal heterogeneity of terrestrial biomass and carbon in vegetation make it very difficult to estimate terrestrial carbon stocks and quantify their dynamics. Vegetation height profiles and disturbance recovery patterns are also required to assess ecosystem health and characterize habitat. The three-dimensional structure of vegetation provides habitats for many species and is a control on biodiversity. Canopy height and structure influence habitat use and specialization, two fundamental processes that modify species richness and abundance across ecosystems. Accurate and consistent 3D measurements of forest structure at the landscape scale are needed for assessing impacts to animal habitats and biodiversity following disturbance.

Ranson, K. Jon↗

NASA NTRS2018

Update on the Development of a Flutter Analysis Capability for Unconventional Aircraft Concepts Using HCDstruct

Following years of development, the Higher-fidelity Conceptual Design and structural optimization (HCDstruct) tool is being extended to support dynamic aeroservoelastic analysis and structural optimization for advanced aircraft concepts. These required enhancements include: the development of an aerodynamic matching routine for correcting Nastran’s doublet-lattice method aerodynamics; the implementation of control surface structural models; and the implementation of support for Nastran’s flutter solution sequence (SOL 145). This paper presents an update on the implementation of generalized control surface structural models and support for Nastran SOL 145.

Quinlan, Jesse R.↗

NASA NTRS2019

Analyzing Seasonal Forcing Mechanisms of the Martian Polar Warming with the NASA Ames Mars Global Climate Model

The meridional transport of heat, momentum, water, dust, trace species and gases is critical for the control of Mars’ climate. Though the nature and structure of the mean meridional circulation has been previously studied, questions remain regarding the seasonal forcing mechanisms, and the implications on the combined thermal and dynamical response for Mars’ climate. A useful diagnostic of the mean meridional circulation and transport in the middle atmosphere is polar warming.

Brecht, A. S.↗

NASA NTRSDate not supplied

Lunar Lander Landing Modeling and Simulation in Simscape

The landing gear is a critical subsystem of a lander for a successful landing on the moon or a planet. During a landing event, structural loading, energy absorption and toppling stability are important factors for the landing gear development. These aspects can be studied using simulations. The landing gear comprising the primary struct, secondary structs, footpad, and joints, is easily modeled using Simscape Multibody toolbox. The energy absorption mechanisms in the structs is readily modeled using Simulink and Multibody blocks based on the relative motions of the inner and outer cylinder of the structures. During touchdown, the footpads strike the lunar surface, and the contact forces can be modeled including the soil mechanical properties. Slosh dynamics are included using a mechanical pendulum model. Tip-over controllers are developed using Simulink blocks and toolboxes. This model was intensively tested manually then additionally with Monte Carlo simulation. It offers the opportunity for landing stability study, i.e. the max slope a lander can land without tipping over in 3D realistic landing situations.

Wei Wu↗

NASA NTRS1967

A modal combination computer program for dynamic analysis of structures

Computer program determines the response of a composite linear structure to sinusoidal base motion of a restrained structure or sinusoidal forces of a free structure. This program is applied to problems of testing practices and closed-loop stability of autopilot controlled space vehicles. It is written for the IBM 7094 in FORTRAN 4 language.

Bamford, R. M.↗

NASA NTRS1991

An adaptive grid method for computing time accurate solutions on structured grids

The solution method consists of three parts: a grid movement scheme; an unsteady Euler equation solver; and a temporal coupling routine that links the dynamic grid to the Euler solver. The grid movement scheme is an algebraic method containing grid controls that generate a smooth grid that resolves the severe solution gradients and the sharp transitions in the solution gradients. The temporal coupling is performed with a grid prediction correction procedure that is simple to implement and provides a grid that does not lag the solution in time. The adaptive solution method is tested by computing the unsteady inviscid solutions for a one dimensional shock tube and a two dimensional shock vortex iteraction.

Bockelie, Michael J.↗

NASA NTRS2009

Synthesis and Control of Flexible Systems with Component-Level Uncertainties

An efficient and computationally robust method for synthesis of component dynamics is developed. The method defines the interface forces/moments as feasible vectors in transformed coordinates to ensure that connectivity requirements of the combined structure are met. The synthesized system is then defined in a transformed set of feasible coordinates. The simplicity of form is exploited to effectively deal with modeling parametric and non-parametric uncertainties at the substructure level. Uncertainty models of reasonable size and complexity are synthesized for the combined structure from those in the substructure models. In particular, we address frequency and damping uncertainties at the component level. The approach first considers the robustness of synthesized flexible systems. It is then extended to deal with non-synthesized dynamic models with component-level uncertainties by projecting uncertainties to the system level. A numerical example is given to demonstrate the feasibility of the proposed approach.

Maghami, Peiman G.↗

NASA NTRS1990

Robust tracking of a flexible spacecraft subject to induced disturbances and parametric uncertainties

A variable structure control technique combined with an operator spline for bilinear systems is implemented to a fast moving deformable structure for purposes of achieving robust tracking performance. The control torque applied to the structure is based on estimates of the structure parameters and on upper bounds of the model errors. For a rapid rotation of the deformable structure, the elastic response can be modeled by oscillators driven by angular acceleration, where stiffness and damping coefficients are also angular velocity and acceleration dependent. By transforming this 'slew-driven' elastic dynamics into a bilinear form, an operator spline can be constructed, that gives a low order estimate of the induced disturbance. An upper bound between the estimated deformation and the unknown exact deformation is also generated, which can be used where required in the sliding control correction.

Karray, Fakhreddine↗

NASA NTRS1988

A parametric LQ approach to multiobjective control system design

The synthesis of a constant parameter output feedback control law of constrained structure is set in a multiple-objective linear quadratic regulator (MOLQR) framework. The use of intuitive objective functions such as model-following ability and closed-loop trajectory sensitivity allows multiple-objective decision-making techniques, such as the surrogate worth tradeoff method, to be applied. For the continuous-time deterministic problem with an infinite time horizon, dynamic compensators as well as static output feedback controllers can be synthesized using a descent Anderson-Moore algorithm modified to impose linear equality constraints on the feedback gains by moving in feasible directions. Results of three different examples are presented, including a unique reformulation of the sensitivity reduction problem.

Kyr, Doug↗

NASA NTRS1976

Long duration exposure facility - A multipurpose free-flying experiment carrier

The Long Duration Exposure Facility (LDEF) is being developed to accommodate, using the Shuttle, a class of technology, science, and applications experiments which do not require a sophisticated or dedicated satellite. The LDEF is a simple reusable structure approximately 4.3 m in diameter and 9 m in length. The basic LDEF consists of a structural framework whose cross section is a 12-sided regular polygon. A facility description is provided, taking into account the structure, aspects of attitude stabilization, the experiment trays, the experiment exposure control canister, the environment monitoring system, and Shuttle bay environment measurements. Missions and questions of experiment selection are discussed, giving attention to orbits, dynamic motions, a space debris damage experiment, thermal coating experiments, the solar cells and arrays experiment, and the active optical components experiment.

Kinard, W. H.↗

NASA NTRS1982

Thermal capabilities and graphical output of PAFEC

The program for automatic finite element calculations (PAFEC) developed for the computation of heat transfer in structures is discussed. The passive and interactive graphics capabilities of the PAFEC system are presented and future developments are outlined. This finite element system is shown to have significant thermal capabilities in support of its general structures. The program offers the following types of analysis: interactive graphics; user defined program control steps; steady state, transient heat transfer; boundary element methods; linear static, stress and displacements; modes and frequencies calculations; direct dynamic time intergration; frequency response analysis; elastohydrodynamic lubrication; large deflection analysis, buckling; creep and plasticity analysis; and substructures analysis.

Akin, J. E.↗