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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Interconnect and Packaging Technologies for Terahertz Communication Systems

Using newly developed silicon micromachining technology that enables low-loss and highly integrated packaging solutions, we are developing vertically stacked transmitters and receivers at terahertz frequencies that can be used for communication and other terahertz systems. Although there are multiple ways to address the problem of interconnect and packaging solutions at these frequencies, such as system-on-package (SOP), multi-chip modules (MCM), substrate integrated waveguide (SIW), liquid crystal polymer (LCP) based multilayer technologies, and others, we show that deep reactive ion etching (DRIE) based silicon micromachining with vertical integration allows the most effective solutions at terahertz frequencies.

Micromachining↗
NASA NTRS2008

Development and Application of an Integrated Approach toward NASA Airspace Systems Research

The National Aeronautics and Space Administration's (NASA) Airspace Systems Program is contributing air traffic management research in support of the 2025 Next Generation Air Transportation System (NextGen). Contributions support research and development needs provided by the interagency Joint Planning and Development Office (JPDO). These needs generally call for integrated technical solutions that improve system-level performance and work effectively across multiple domains and planning time horizons. In response, the Airspace Systems Program is pursuing an integrated research approach and has adapted systems engineering best practices for application in a research environment. Systems engineering methods aim to enable researchers to methodically compare different technical approaches, consider system-level performance, and develop compatible solutions. Systems engineering activities are performed iteratively as the research matures. Products of this approach include a demand and needs analysis, system-level descriptions focusing on NASA research contributions, system assessment and design studies, and common systemlevel metrics, scenarios, and assumptions. Results from the first systems engineering iteration include a preliminary demand and needs analysis; a functional modeling tool; and initial system-level metrics, scenario characteristics, and assumptions. Demand and needs analysis results suggest that several advanced concepts can mitigate demand/capacity imbalances for NextGen, but fall short of enabling three-times current-day capacity at the nation s busiest airports and airspace. Current activities are focusing on standardizing metrics, scenarios, and assumptions, conducting system-level performance assessments of integrated research solutions, and exploring key system design interfaces.

Barhydt, Richard↗
NASA NTRS2018

Practical Orbit Determination for Aerobraking with Accumulated Accelerometer Data

Navigation during aerobraking missions has historically relied solely on radiometric Doppler data. Accelerometer data, available on all modern spacecraft, has the potential to supplement Doppler data, increasing operational tempos, filling tracking data gaps, and improving the accuracy of orbit determination solutions. However, integration of Doppler and accelerometer data into the batch filter solutions used for operational navigation has proven to be practically challenging, due to the narrow region of adequate linear approximation for acceleration incurred by drag. This work proposes to use the accumulated velocity changes derived from these values as a more compatible data type. Demonstrations of results focus on NASA’s Maven and ESA’s TGO mission, and how this technique can be used to improve operations for the upcoming Maven aerobraking phase with reduced tracking data and lighter staffing requirements.

Young, Brian↗
NASA NTRS1979

Applying integrals of motion to the numerical solution of differential equations

A method is developed for using the integrals of systems of nonlinear, ordinary differential equations in a numerical integration process to control the local errors in these integrals and reduce the global errors of the solution. The method is general and can be applied to either scaler or vector integrals. A number of example problems, with accompanying numerical results, are used to verify the analysis and support the conjecture of global error reduction.

Jezewski, D. J.↗
NASA NTRS1980

Applying integrals of motion to the numerical solution of differential equations

A method is developed for using the integrals of systems of nonlinear, ordinary, differential equations in a numerical integration process to control the local errors in these integrals and reduce the global errors of the solution. The method is general and can be applied to either scalar or vector integrals. A number of example problems, with accompanying numerical results, are used to verify the analysis and support the conjecture of global error reduction.

Vezewski, D. J.↗
NASA NTRS2019

Pterodactyl: An Uncoupled Range Control Approach to Fully Numerical Predictor-Corrector Entry Guidance

Entry, descent, and landing (EDL) has been identified as a core area of investment in NASA's Strategic Technology Investment Plan (NASA STIP). STIP lists the space technologies needed to help achieve NASA's science, technology, and exploration goals across the agency. Within the EDL core area, deployable hypersonic decelerators, also known as deployable entry vehicles (DEVs), have been identified as an area of investment, due to its potential to revolutionize payload delivery methods to Earth and other planets. These vehicles, which can deploy their heat shields or alter their shape before entry, exploit an increased and more effective drag ratio by using less mass than traditional blunt body vehicles with rigid aeroshells. DEVs like Adaptive Deployable Entry and Placement Technology (ADEPT) and Hypersonic Inflatable Aerodynamic Decelerator (HIAD) have demonstrated the capability of transporting the equivalent science payloads of blunt body rigid aeroshells, while using a significantly smaller diameter when stowed within a launch vehicle. While DEVs' increased energy dissipation for less mass is an attractive feature, their ability to contract and expand would require advancements in the current state-of-the-art guidance and control (G&C) architectures used by traditional rigid vehicles. Pterodactyl, a project funded by NASA's Space Technology Mission Directorate (STMD), aims to provide feasible integrated G&C solutions for DEVs, complete with optimized vehicle designs and packaging analyses. Structural and aerodynamic analyses for the explored control systems suggested a need for a bank angle guidance algorithm, a heritage guidance approach that has been used in many entry precision targeting vehicles, as well as an additional need for the development of a non-bank angle guidance. For this reason, Pterodactyl will consider four different G&C configurations during its design phase: i) a reaction control system for bank (sigma) control, ii) a mass movement system for angle of attack (alpha) sideslip (beta) control, iii) flaps for alpha - beta control, and iv) flaps for sigma control. To increase the applicability of each proposed integrated G&C architecture, an 11 km/s lunar return demonstration mission is selected to stress the developed technology capability. The Lifting Nano-ADEPT (LNA) vehicle is chosen as the DEV to demonstrate the integrated solutions. This paper will detail the trajectory design for a lunar return mission, using the validated bank control guidance algorithm Fully Numerical Predictor-Corrector Entry Guidance (FNPEG) and a newly developed guidance algorithm: FNPEG Uncoupled Range Control (URC). FNPEG-URC diverges from traditional bank angle guidances by producing alpha and beta commands to thereby decouple downrange and crossrange control. This presentation will discuss the development and overall performance of FNPEG and FNPEG-URC for each of the four G&C configurations. Successful G&C configurations are defined as those that can deliver payloads to the intended descent and landing site while abiding by trajectory constraints in the face of dispersions.

Johnson, Breanna↗
NASA NTRS1974

Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing

The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.

Kong, J. A.↗
NASA NTRS1990

A boundary integral approach to the scattering of nonplanar acoustic waves by rigid bodies

The acoustic scattering of an incident wave by a rigid body can be described by a singular Fredholm integral equation of the second kind. This equation is derived by solving the wave equation using generalized function theory, Green's function for the wave equation in unbounded space, and the acoustic boundary condition for a perfectly rigid body. This paper will discuss the derivation of the wave equation, its reformulation as a boundary integral equation, and the solution of the integral equation by the Galerkin method. The accuracy of the Galerkin method can be assessed by applying the technique outlined in the paper to reproduce the known pressure fields that are due to various point sources. From the analysis of these simpler cases, the accuracy of the Galerkin solution can be inferred for the scattered pressure field caused by the incidence of a dipole field on a rigid sphere. The solution by the Galerkin technique can then be applied to such problems as a dipole model of a propeller whose pressure field is incident on a rigid cylinder. This is the groundwork for modeling the scattering of rotating blade noise by airplane fuselages.

Gallman, Judith M.↗
NASA NTRS1980

An investigation of dynamic-analysis methods for variable-geometry structures

Selected space structure configurations were reviewed in order to define dynamic analysis problems associated with variable geometry. The dynamics of a beam being constructed from a flexible base and the relocation of the completed beam by rotating the remote manipulator system about the shoulder joint were selected. Equations of motion were formulated in physical coordinates for both of these problems, and FORTRAN programs were developed to generate solutions by numerically integrating the equations. These solutions served as a standard of comparison to gauge the accuracy of approximate solution techniques that were developed and studied. Good control was achieved in both problems. Unstable control system coupling with the system flexibility did not occur. An approximate method was developed for each problem to enable the analyst to investigate variable geometry effects during a short time span using standard fixed geometry programs such as NASTRAN. The average angle and average length techniques are discussed.

Austin, F.↗
NASA NTRS1984

The statistical theory of the fracture of fragile bodies. Part 2: The integral equation method

It is demonstrated how with the aid of a bending test, the Weibull fracture risk function can be determined - without postulating its analytical form - by resolving an integral equation. The respective solutions for rectangular and circular section beams are given. In the first case the function is expressed as an algorithm and in the second, in the form of series. Taking into account that the cumulative fracture probability appearing in the solution to the integral equation must be continuous and monotonically increasing, any case of fabrication or selection of samples can be treated.

Kittl, P.↗
NASA NTRS1986

Satellite attitude motion models for capture and retrieval investigations

The primary purpose of this research is to provide mathematical models which may be used in the investigation of various aspects of the remote capture and retrieval of uncontrolled satellites. Emphasis has been placed on analytical models; however, to verify analytical solutions, numerical integration must be used. Also, for satellites of certain types, numerical integration may be the only practical or perhaps the only possible method of solution. First, to provide a basis for analytical and numerical work, uncontrolled satellites were categorized using criteria based on: (1) orbital motions, (2) external angular momenta, (3) internal angular momenta, (4) physical characteristics, and (5) the stability of their equilibrium states. Several analytical solutions for the attitude motions of satellite models were compiled, checked, corrected in some minor respects and their short-term prediction capabilities were investigated. Single-rigid-body, dual-spin and multi-rotor configurations are treated. To verify the analytical models and to see how the true motion of a satellite which is acted upon by environmental torques differs from its corresponding torque-free motion, a numerical simulation code was developed. This code contains a relatively general satellite model and models for gravity-gradient and aerodynamic torques. The spacecraft physical model for the code and the equations of motion are given. The two environmental torque models are described.

Cochran, John E., Jr.↗
NASA NTRS2003

Sharing knowledge with the public during a crisis: NASA's public portal

This case study looks at integrating the web governance policies and procedures, migration to a single content management solution, and integrating best-of-breed technology with high-impact, interactive components. In particular, this case study is interesting in the dynamic scalability of this application to meet the needs of an organization on the front lines during a crisis.

organizational learning↗
NASA NTRSDate not supplied

Deep Learning-Based Negotiation Strategy Selection for Cooperative Conflict Resolution in Urban Air Mobility

This paper presents a collaborative conflict resolution technique using deep neural network-based intelligent search of the solution space. This approach offers a rapid convergence to a mutually acceptable solution for real-time conflict resolution, suitable for urban air mobility operations. Furthermore, the presented technique allows operational flexibility to the urban air mobility agents where these agents can collaboratively devise the solution via integrative negotiation, based on their local utility functions, as long as such a solution does not violate the global safety thresholds. The presented machine-to-machine negotiation method is built on our prior work on holistic assessment of the airspace and potential conflict detection implemented at-the-edge, onboard the unmanned aircraft systems. This paper extends the prior work to augment decision-making at-the-edge, thereby, promising a true distributed control architecture for urban air mobility. In this approach, each agent (a) builds a potential in-flight conflict map, (b) identifies the conflicting agents, (c) dynamically prepares a list of alternatives based on its current utility functions, (d) negotiates with the conflicting agents to pick one of these alternatives, and (e) implements the negotiated alternative to mutually resolve the conflict. Note that such an approach does not require a contingency plan to be made pre-flight, as the conflict resolution strategies are decided and negotiated in real time based on the present state of the agent. The contingency plan, if available, can serve as an input to the real-time conflict resolution strategy formulation, and also can be used as a fallback plan in case the negotiation fails and the impacted agents need to switch to a rule-based/supervisory resolution mode from the discussed distributed resolution mode. The presented collaborative negotiation-based conflict resolution technique incorporates a time-dependent reward function to catalyze collaborative resolution by incentivizing the agents with local and global rewards beneficial to their business operations.

Advanced Air Mobility↗
NASA NTRS1982

Study of tethered satellite active attitude control

Existing software was adapted for the study of tethered subsatellite rotational dynamics, an analytic solution for a stable configuration of a tethered subsatellite was developed, the analytic and numerical integrator (computer) solutions for this "test case' was compared in a two mass tether model program (DUMBEL), the existing multiple mass tether model (SKYHOOK) was modified to include subsatellite rotational dynamics, the analytic "test case,' was verified, and the use of the SKYHOOK rotational dynamics capability with a computer run showing the effect of a single off axis thruster on the behavior of the subsatellite was demonstrated. Subroutines for specific attitude control systems are developed and applied to the study of the behavior of the tethered subsatellite under realistic on orbit conditions. The effect of all tether "inputs,' including pendular oscillations, air drag, and electrodynamic interactions, on the dynamic behavior of the tether are included.

Colombo, G.↗
NASA NTRS2017

New Mathematical Functions for Vacuum System Analysis

A new bivariate function has been found that provides solutions of integrals having the form u (sup minus eta) e (sup u) du which arise when developing predictions for the behavior of pressure within a rigid volume under high vacuum conditions in the presence of venting as well as sources characterized by power law transient decay over the range [0,1] for eta and for u greater than or equal to 0. A few properties of the new function are explored in this work. For instance the eta equals 1/2 case reproduces the Dawson function. In addition, a slight variation of the solution technique reproduces the exponential integral for eta equals 1. The technique used to generate these functions leads to an approach for solving a more general class of nonlinear ordinary differential equations, with the potential for identifying other new functions that solve other integrals.

Dawson Function↗
NASA NTRS2016

Using Docker Containers to Extend Reproducibility Architecture for the NASA Earth Exchange (NEX)

NASA Earth Exchange (NEX) is a data, supercomputing and knowledge collaboratory that houses NASA satellite, climate and ancillary data where a focused community can come together to address large-scale challenges in Earth sciences. As NEX has been growing into a petabyte-size platform for analysis, experiments and data production, it has been increasingly important to enable users to easily retrace their steps, identify what datasets were produced by which process chains, and give them ability to readily reproduce their results. This can be a tedious and difficult task even for a small project, but is almost impossible on large processing pipelines. We have developed an initial reproducibility and knowledge capture solution for the NEX, however, if users want to move the code to another system, whether it is their home institution cluster, laptop or the cloud, they have to find, build and install all the required dependencies that would run their code. This can be a very tedious and tricky process and is a big impediment to moving code to data and reproducibility outside the original system. The NEX team has tried to assist users who wanted to move their code into OpenNEX on Amazon cloud by creating custom virtual machines with all the software and dependencies installed, but this, while solving some of the issues, creates a new bottleneck that requires the NEX team to be involved with any new request, updates to virtual machines and general maintenance support. In this presentation, we will describe a solution that integrates NEX and Docker to bridge the gap in code-to-data migration. The core of the solution is saemi-automatic conversion of science codes, tools and services that are already tracked and described in the NEX provenance system, to Docker - an open-source Linux container software. Docker is available on most computer platforms, easy to install and capable of seamlessly creating and/or executing any application packaged in the appropriate format. We believe this is an important step towards seamless process deployment in heterogeneous environments that will enhance community access to NASA data and tools in a scalable way, promote software reuse, and improve reproducibility of scientific results.

earth exchange↗