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NASA NTRS2001

Durability Characterization of Advanced Polymeric Composites at Cryogenic Temperatures

The next generation of reusable launch vehicles will require technology development in several key areas. Of these key areas, the development of polymeric composite cryogenic fuel tanks promises to present one of the most difficult technical challenges. It is envisioned that a polymer matrix composite (PMC) tank would be a large shell structure capable of containing cryogenic fuels and carrying a range of structural loads. The criteria that will be imposed on such a design include reduced weight, conformal geometry, and impermeability. It is this last criterion, impermeability, that will provide the focus of this paper. The essence of the impermeability criterion is that the tank remains leak free throughout its design lifetime. To address this criterion, one of the first steps is to conduct a complete durability assessment of the PMC materials. At Langley Research Center, a durability assessment of promising new polyimide-based PMCs is underway. This durability program has focused on designing a set of critical laboratory experiments that will determine fundamental material properties under combined thermal-mechanical loading at cryogenic temperatures. The test program provides measurements of lamina and laminate properties, including strength, stiffness, and fracture toughness. The performance of the PMC materials is monitored as a function of exposure conditions and aging time. Residual properties after exposure are measured at cryogenic temperatures and provide quantitative values of residual strength and stiffness. Primary degradation mechanisms and the associated damage modes are measured with both destructive and nondestructive techniques. In addition to mechanical properties, a range of physical properties, such as weight, glass transition, and crack density, are measured and correlated with the test conditions. This paper will report on the progress of this research program and present critical results and illustrative examples of current findings.

Gates, T. S.↗

NASA NTRS2004

Understanding the Global Structure and Evolution of Coronal Mass Ejections in the Solar Wind

This report summarizes the technical progress made during the first six months of the second year of the NASA Living with a Star program contract Understanding the global structure and evolution of coronal mass ejections in the solar wind, between NASA and Science Applications International Corporation, and covers the period November 18, 2003 - May 17,2004. Under this contract SAIC has conducted numerical and data analysis related to fundamental issues concerning the origin, intrinsic properties, global structure, and evolution of coronal mass ejections in the solar wind. During this working period we have focused on a quantitative assessment of 5 flux rope fitting techniques. In the following sections we summarize the main aspects of this work and our proposed investigation plan for the next reporting period. Thus far, our investigation has resulted in 6 refereed scientific publications and we have presented the results at a number of scientific meetings and workshops.

Riley, Pete↗

NASA NTRS2006

The State of Space Propulsion Research

The current state of space propulsion research is assessed from both a historical perspective, spanning the decades since Apollo, and a forward-looking perspective, as defined by the enabling technologies required for a meaningful and sustainable human and robotic exploration program over the forthcoming decades. Previous research and technology investment approaches are examined and a course of action suggested for obtaining a more balanced portfolio of basic and applied research. The central recommendation is the establishment of a robust national Space Propulsion Research Initiative that would run parallel with systems development and include basic research activities. The basic framework and technical approach for this proposed initiative are defined and a potential implementation approach is recommended.

Sackheim, R. L.↗

NASA NTRS2016

Assessment of the Impacts of ACLS on the ISS Life Support System Using Dynamic Simulations in V-HAB

The Advanced Closed Loop System (ACLS) is currently under development by Airbus Defense and Space and is slated for launch to the International Space Station (ISS) in 2017. The addition of new hardware into an already complex system such as the ISS life support system (LSS) always poses operational risks. It is therefore important to understand the impacts ACLS will have on the existing systems to ensure smooth operations for the ISS. This analysis can be done by using dynamic computer simulations and one possible tool for such a simulation is the Virtual Habitat (V-HAB). Based on MATLAB, V-HAB has been under development at the Institute of Astronautics of the Technical University of Munich (TUM) since 2004 and in the past has been successfully used to simulate the ISS life support systems. The existing V-HAB ISS simulation model treated the interior volume of the space station as one large, ideally-stirred container. This model was improved to allow the calculation of the atmospheric composition inside individual modules of the ISS by splitting it into twelve distinct volumes. The virtual volumes are connected by a simulation of the inter-module ventilation flows. This allows for a combined simulation of the LSS hardware and the atmospheric composition aboard the ISS. A dynamic model of ACLS is added to the ISS Simulation and several different operating modes for both ACLS and the existing ISS life support systems are studied and the impacts of ACLS on the rest of the system are determined. The results suggest that the US, Russian and ACLS CO2 systems can operate at the same time without impeding each other. Furthermore, based on the results of this analysis, the US and ACLS Sabatier systems can be operated in parallel as well to a achieve a very low CO2 concentration in the cabin atmosphere.

Putz, Daniel↗

NASA NTRS2016

Assessment of the Impacts of ACLS on the ISS Life Support System using Dynamic Simulations in V-HAB

The Advanced Closed Loop System (ACLS) is currently under development by Airbus Defense and Space and is slated for launch to the International Space Station (ISS) in 2017. The addition of new hardware into an already complex system such as the ISS life support system (LSS) always poses operational risks. It is therefore important to understand the impacts ACLS will have on the existing systems to ensure smooth operations for the ISS. This analysis can be done by using dynamic computer simulations and one possible tool for such a simulation is Virtual Habitat (V-HAB). Based on Matlab (Registered Trademark) V-HAB has been under development at the Institute of Astronautics of the Technical University Munich (TUM) since 2006 and in the past has been successfully used to simulate the ISS life support systems. The existing V-HAB ISS simulation model treated the interior volume of the space station as one large ideally-stirred container. This model was improved to allow the calculation of the atmospheric composition inside the individual modules of the ISS by splitting it into ten distinct volumes. The virtual volumes are connected by a simulation of the inter-module ventilation flows. This allows for a combined simulation of the LSS hardware and the atmospheric composition aboard the ISS. A dynamic model of ACLS is added to the ISS simulation and different operating modes for both ACLS and the existing ISS life support systems are studied to determine the impacts of ACLS on the rest of the system. The results suggest that the US, Russian and ACLS CO2 systems can operate at the same time without impeding each other. Furthermore, based on the results of this analysis, the US and ACLS Sabatier systems can be operated in parallel as well to achieve the highest possible CO2 recycling together with a low CO2 concentration.

Puetz, Daniel↗

NASA NTRSDate not supplied

Sizing and Performance Analysis of a MW-Class Electrified Aircraft Propulsion (Eap) System for A Parallel Hybrid Turboprop Concept

Aircraft electrification has emerged as a pivotal research and development focus in the 21st century, gaining international momentum as a strategic approach to curtail fuel consumption and emissions in the civil aviation sector. Under the Electrified Powertrain Flight Demonstration (EPFD) project, NASA and industry partners are raising the technical readiness, addressing integration challenges and gathering data for future standards and regulations for demonstrate Megawatt (MW) class Electrified Aircraft Propulsion (EAP) systems which can be utilized on regional turboprop or single aisle transports. With the rapid emergence of novel EAP concepts, risk reduction efforts are focused on developing the capabilities to evaluate the impacts of electrification at the conceptual design level where high variability in the EAP system architecture must be accounted for. This paper details an integrated, approach to parametric sizing of multi-MW EAP systems with the primary goal of assessing vehicle-level performance sensitivities to variations in electrical system component-level performance metrics. The focus of this work is to investigate the degree to which EAP component parameters such as specific power, efficiency, and energy density impact range and overall fuel savings.

EAP↗

NASA NTRSDate not supplied

Sizing and Performance Analysis of a MegaWatt-Class Electrified Aircraft Propulsion (EAP) System for a Parallel Hybrid Turboprop Concept

EAP↗

NASA NTRS2016

Architecture Modeling on the Europa Project

In 2015 NASA chartered a partnership between the Jet Propulsion Laboratory (JPL) and the Johns Hopkins Applied Physics Laboratory (APL) to begin planning a mission to study the Jovian moon Europa. The project has adopted a Model-Based Systems Engineering (MBSE) approach to its architecting process since its early formulation, developing certain modeling practices and tools as needed, with the expectation that this process would result in a more consistent and verifiable architecture than with a more traditional document-based approach. A sound architecture is essential to provide the rationale for requirements on the system design, and to define the trade space of acceptable design points within which technical and programmatic concerns as well as project objectives can be addressed. This paper provides an overview of the framework used by the Europa project to describe the mission architecture and discusses how a system model was instrumental in providing a single-source-of-truth for this description. Several key modeling patterns to represent the architecture are presented, along with audit methods to ensure the consistency and the correctness of the model. Finally, the benefits and challenges of using a model-based approach to generate traditional requirements documents and other gate products are assessed.

Dubos, Gregory F.↗

NASA NTRS1979

The 18/30 GHz fixed communications system service demand assessment. Volume 2: Main text

The total demand for communications services, and satellite transmission services at the 4/6 GHz, 12/14 GHz, and 18/30 GHz frequencies is assessed. The services are voice, video, and data services. Traffic demand, by service, is distributed by geographical regions, population density, and distance between serving points. Further distribution of traffic is made among four major end user groups: business, government, institutions and private individuals. A traffic demand analysis is performed on a typical metropolitan city to examine service distribution trends. The projected cost of C and Ku band satellite systems are compared on an individual service basis to projected terrestrial rates. Separation of traffic between transmission systems, including 18/30 GHz systems, is based on cost, user, and technical considerations.

Gabriszeski, T.↗

NASA NTRS1983

Thermal behavior of laboratory models of honeycomb-covered solar ponds

Laboratory experiments were conducted to provide insight into the technical feasibility of honeycomb-covered solar ponds. Cooling tests using honeycomb panels of various materials and geometries showed that a 5.7-cm-thick one-tier panel insulated as effectively as a 10-cm fiberglass slab. Heating tests demonstrated that a model pond covered with a polycarbonate panel boiled upon 16 hours of continuous exposure to a 150-W spotlight. Analysis of the experimental data indicates positively that honeycomb-covered solar ponds can be expected to perform satisfactorily, and that larger-scale outdoor tests should be conducted to provide a more realistic assessment and a more refined performance estimate.

Lin, E. I. H.↗

NASA NTRS1993

Lunar-base construction equipment and methods evaluation

A process for evaluating lunar-base construction equipment and methods concepts is presented. The process is driven by the need for more quantitative, systematic, and logical methods for assessing further research and development requirements in an area where uncertainties are high, dependence upon terrestrial heuristics is questionable, and quantitative methods are seldom applied. Decision theory concepts are used in determining the value of accurate information and the process is structured as a construction-equipment-and-methods selection methodology. Total construction-related, earth-launch mass is the measure of merit chosen for mathematical modeling purposes. The work is based upon the scope of the lunar base as described in the National Aeronautics and Space Administration's Office of Exploration's 'Exploration Studies Technical Report, FY 1989 Status'. Nine sets of conceptually designed construction equipment are selected as alternative concepts. It is concluded that the evaluation process is well suited for assisting in the establishment of research agendas in an approach that is first broad, with a low level of detail, followed by more-detailed investigations into areas that are identified as critical due to high degrees of uncertainty and sensitivity.

Boles, Walter W.↗

NASA NTRS1989

An assessment of multibody simulation tools for articulated spacecraft

A survey of multibody simulation codes was conducted in the spring of 1988, to obtain an assessment of the state of the art in multibody simulation codes from the users of the codes. This survey covers the most often used articulated multibody simulation codes in the spacecraft and robotics community. There was no attempt to perform a complete survey of all available multibody codes in all disciplines. Furthermore, this is not an exhaustive evaluation of even robotics and spacecraft multibody simulation codes, as the survey was designed to capture feedback on issues most important to the users of simulation codes. We must keep in mind that the information received was limited and the technical background of the respondents varied greatly. Therefore, only the most often cited observations from the questionnaire are reported here. In this survey, it was found that no one code had both many users (reports) and no limitations. The first section is a report on multibody code applications. Following applications is a discussion of execution time, which is the most troublesome issue for flexible multibody codes. The representation of component flexible bodies, which affects both simulation setup time as well as execution time, is presented next. Following component data preparation, two sections address the accessibility or usability of a code, evaluated by considering its user interface design and examining the overall simulation integrated environment. A summary of user efforts at code verification is reported, before a tabular summary of the questionnaire responses. Finally, some conclusions are drawn.

Man, Guy K.↗

NASA NTRS1995

Performance seeking control excitation mode

Flight testing of the performance seeking control (PSC) excitation mode was successfully completed at NASA Dryden on the F-15 highly integrated digital electronic control (HIDEC) aircraft. Although the excitation mode was not one of the original objectives of the PSC program, it was rapidly prototyped and implemented into the architecture of the PSC algorithm, allowing valuable and timely research data to be gathered. The primary flight test objective was to investigate the feasibility of a future measurement-based performance optimization algorithm. This future algorithm, called AdAPT, which stands for adaptive aircraft performance technology, generates and applies excitation inputs to selected control effectors. Fourier transformations are used to convert measured response and control effector data into frequency domain models which are mapped into state space models using multiterm frequency matching. Formal optimization principles are applied to produce an integrated, performance optimal effector suite. The key technical challenge of the measurement-based approach is the identification of the gradient of the performance index to the selected control effector. This concern was addressed by the excitation mode flight test. The AdAPT feasibility study utilized the PSC excitation mode to apply separate sinusoidal excitation trims to the controls - one aircraft, inlet first ramp (cowl), and one engine, throat area. Aircraft control and response data were recorded using on-board instrumentation and analyzed post-flight. Sensor noise characteristics, axial acceleration performance gradients, and repeatability were determined. Results were compared to pilot comments to assess the ride quality. Flight test results indicate that performance gradients were identified at all flight conditions, sensor noise levels were acceptable at the frequencies of interest, and excitations were generally not sensed by the pilot.

Schkolnik, Gerard↗

NASA NTRS2001

Design and Performance of 40 cm Ion Optics

A 40 cm ion thruster is being developed at the NASA Glenn Research Center to obtain input power and propellant throughput capabilities of 10 kW and 550 kg. respectively. The technical approach here is a continuation of the "derating" technique used for the NSTAR ion thruster. The 40 cm ion thruster presently utilizes the NSTAR ion optics aperture geometry to take advantage of the large database of lifetime and performance data already available. Dome-shaped grids were chosen for the design of the 40 cm ion optics because this design is naturally suited for large-area ion optics. Ion extraction capabilities and electron backstreaming limits for the 40 cm ion optics were estimated by utilizing NSTAR 30 cm ion optics data. A preliminary service life assessment showed that the propellant throughput goal of 550 kg of xenon may be possible with molybdenum 40 cm ion optics. One 40 cm ion optics' set has been successfully fabricated to date. Additional ion optics' sets are presently being fabricated. Preliminary performance tests were conducted on a laboratory model 40 cm ion thruster.

Soulas, George C.↗

NASA NTRS2007

The NASA Dryden Flight Research Center Unmanned Aircraft System Service Capabilities

Over 60 years of Unmanned Aircraft System (UAS) expertise at the NASA Dryden Flight Research Center are being leveraged to provide capability and expertise to the international UAS community. The DFRC brings together technical experts, UAS, and an operational environment to provide government and industry a broad capability to conduct research, perform operations, and mature systems, sensors, and regulation. The cornerstone of this effort is the acquisition of both a Global Hawk (Northrop Grumman Corporation, Los Angeles, California) and Predator B (General Atomics Aeronautical Systems, Inc., San Diego, California) unmanned aircraft system (UAS). In addition, a test range for small UAS will allow developers to conduct research and development flights without the need to obtain approval from civil authorities. Finally, experts are available to government and industry to provide safety assessments in support of operations in civil airspace. These services will allow developers to utilize limited resources to their maximum capability in a highly competitive environment.

Bauer, Jeff↗

NASA NTRS2007

The NASA Dryden Flight Research Center Unmanned Aircraft System Service Capabilities

Over 60 years of Unmanned Aircraft System (UAS) expertise at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center are being leveraged to provide capability and expertise to the international UAS community. The DFRC brings together technical experts, UAS, and an operational environment to provide government and industry a broad capability to conduct research, perform operations, and mature systems, sensors, and regulation. The cornerstone of this effort is the acquisition of both a Global Hawk (Northrop Grumman Corporation, Los Angeles, California) and Predator B (General Atomics Aeronautical Systems, Inc., San Diego, California) unmanned aircraft system (UAS). In addition, a test range for small UAS will allow developers to conduct research and development flights without the need to obtain approval from civil authorities. Finally, experts are available to government and industry to provide safety assessments in support of operations in civil airspace. These services will allow developers to utilize limited resources to their maximum capability in a highly competitive environment.

Bauer, Jeff↗

NASA NTRS2009

Systematic Benchmarking of Diagnostic Technologies for an Electrical Power System

Automated health management is a critical functionality for complex aerospace systems. A wide variety of diagnostic algorithms have been developed to address this technical challenge. Unfortunately, the lack of support to perform large-scale V&V (verification and validation) of diagnostic technologies continues to create barriers to effective development and deployment of such algorithms for aerospace vehicles. In this paper, we describe a formal framework developed for benchmarking of diagnostic technologies. The diagnosed system is the Advanced Diagnostics and Prognostics Testbed (ADAPT), a real-world electrical power system (EPS), developed and maintained at the NASA Ames Research Center. The benchmarking approach provides a systematic, empirical basis to the testing of diagnostic software and is used to provide performance assessment for different diagnostic algorithms.

Kurtoglu, Tolga↗

NASA NTRS2006

Assessment of Lithium-based Battery Electrolytes Developed under the NASA PERS Program

Recently, NASA formally completed the Polymer Energy Rechargeable System (PERS) Program, which was established in 2000 in collaboration with the Air Force Research Laboratory (AFRL) to support the development of polymer-based, lithium-based cell chemistries and battery technologies to address the next generation of aerospace applications and mission needs. The goal of this program was to ultimately develop an advanced, space-qualified battery technology, which embodied a solid polymer electrolyte (SPE) and complementary components, with improved performance characteristics that would address future aerospace battery requirements. Programmatically, the PERS initiative exploited both interagency collaborations to address common technology and engineering issues and the active participation of academia and private industry. The initial program phases focused on R&D activities to address the critical technical issues and challenges at the cell level. A variety of cell and polymeric electrolyte concepts were pursued as part of the development efforts undertaken at numerous governmental, industrial and academic laboratories. Numerous candidate electrolyte materials were developed, synthesized and optimized for evaluation. Utilizing the component screening facility and the "standardized" test procedures developed at the NASA Glenn Research Center, electrochemical screening and performance evaluations of promising candidate materials were completed. This overview summarizes test results for a variety of candidate electrolyte materials that were developed under the PERS Program. Electrolyte properties are contrasted and compared to the original project goals, and the strengths and weaknesses of the electrolyte chemistries are discussed. Limited cycling data for full-cells using lithium metal and vanadium oxide electrodes are also presented. Based on measured electrolyte properties, the projected performance characteristics and temperature limitations of batteries utilizing the advanced electrolytes and components have been estimated. Limitations for the achievement of practical performance levels are also discussed, as well as needs for future research and development.

Bennett, William R.↗