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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 NTRS2019

Towards Resilient Autonomous Navigation of Drones

Robots and particularly drones are especially useful in exploring extreme environments that pose hazards to humans. To ensure safe operations in these situations, usually perceptually degraded and without good GNSS, it is critical to have a reliable and robust state estimation solution. The main body of literature in robot state estimation focuses on developing complex algorithms favoring accuracy. Typically, these approaches rely on a strong underlying assumption: the main estimation engine will not fail during operation. In contrast, we propose an architecture that pursues robustness in state estimation by considering redundancy and heterogeneity in both sensing and estimation algorithms. The architecture is designed to expect and detect failures and adapt the behavior of the system to ensure safety. To this end, we present HeRO (Heterogeneous Redundant Odometry): a stack of estimation algorithms running in parallel supervised by a resiliency logic. This logic carries out three main functions: a) perform confidence tests both in data quality and algorithm health; b) re-initialize those algorithms that might be malfunctioning; c) generate a smooth state estimate by multiplexing the inputs based on their quality. The state and quality estimates are used by the guidance and control modules to adapt the mobility behaviors of the system. The validation and utility of the approach are shown with real experiments on a ying robot for the use case of autonomous exploration of subterranean environments, with particular results from the STIX event of the DARPA Subterranean Challenge.

Agha-mohammadi, Ali-akbar↗
NASA NTRS2023

DPOD2020: A DORIS Extension of the ITRF2020 for Precise Orbit Determination

As one of the tracking systems used to determine orbits of the altimeter mission satellites (such as TOPEX/Poseidon, Envisat, Jason-1/-2/-3, CryoSat-2, Saral/Altika, Sentinel-3A/-3B, HY-2A/C/D, Jason-CS/Sentinel-6A, SWOT), DORIS (Doppler Orbitography Radiopositionning Integrated by Satellite) allows to determine positions and velocities of tracking stations that define a stable reference for the estimation of the precise orbits and thus are fundamental for the quality of the altimeter data and derived mean sea level products. Due to the time evolution of the DORIS ground network, some stations included in the 2020 realization of the International Terrestrial Reference Frame (ITRF2020) have been decommissioned and since 2021.0 a few new stations were added to the tracking network. Therefore, to satisfy operational requirements for POD (Precise Orbit Determination) and routine delivery of geodetic products, the International DORIS Service (IDS) regularly updates the DPOD (DORIS terrestrial reference frame for Precise Orbit Determination). The DPOD solutions include mean positions and velocities of all the DORIS stations since 1993.0 derived from the stacking of the latest IDS weekly combined series aligned to the current ITRF. In this paper, we first present the stacking process of the DPOD2020 version 1.0. Then, we address the validation procedure of the DPO2020 including comparison with ITRF2020 and POD tests. For eighty percent of all the time segments of all the DORIS stations, the station position differences between DPOD2020 version 1.0 and ITRF2020 are smaller than ten millimeters. The major position differences between these two solutions are associated with the DORIS sites either localized in the South Atlantic Anomaly region or with time spans smaller than one year. Compared to DPOD2014, the DPOD2020 shows reduction of the main statistics of the DORIS-to-DORIS tie residuals (differences between the estimated and measured ties). The POD tests showed similar results for DPOD2020 and DPOD2014 for most of the altimetric satellites (TOPEX/Poseidon, Jason-1, CryoSat-2, Jason-3). In addition, we observed better POD results with DPOD2020 for the latest altimetric satellite Sentinel-3A as well as a slight degradation for Jason-2. That degradation was fully explained by slightly worst results for the stations localized in the South Atlantic Anomaly region.

DORIS↗
NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Regenerative fuel cells (RFCs) are an attractive energy storage solution for lunar missions as a technology capable of providing a higher specific energy (i.e., W∙h/kg) than state-of-the-art packaged Li-ion battery systems. An RFC consists of the (1 & 2) electrochemical stacks (chemical to electrical energy conversion to supply electricity to an external load, i.e. the fuel cell reaction, and electrical to chemical energy conversion of supplied electrical power to dissociate water into hydrogen and oxygen gases, i.e. water electrolysis), (3) fluidic conditioning, (4) reactant storage, (5) avionics, (6) power management and distribution (PMAD), and (7) thermal management. NASA’s Glenn Research Center has designed, assembled, and tested a breadboard RFC sys-tem capable of operating autonomously for multiple simulated lunar day/night cycles in a laboratory environment. The system is comprised of a non-flow through proton exchange membrane (PEM) fuel cell stack and a liquid-anode feed PEM electrolyzer (EZ) stack designed to electrochemically compress the reactants at balanced pressures up to 12.4 MPa (1800 psia). The fluidic conditioning, avionics, PMAD, and thermal management sub-systems are largely comprised of commercial-off-the-shelf components for this system-level development effort. The hardware is controlled by a CubeSat space processor running an operational program based on core flight architecture that can control the RFC hardware autonomously through a state machine with fault monitoring. The testing results highlighted here were completed with the system in an open-loop configuration such that reactants generated through water electrolysis were vented while gas cylinders supplied fuel cell operation. The breadboard operated autonomously, but there were five unplanned transitions to a safe state that required a manual restart after reviewing the data, determining a root cause, and implementing a solution. Four of the transitions were caused by the thermal management subsystem and the fifth was caused by a water management control issue in the EZ sub-system. The RFC system operated for over 550 hours with the final cycle being slightly abbreviated due to reasons unrelated to system performance.

Kerrigan Cain↗
NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Regenerative fuel cells (RFCs) are an attractive energy storage solution for lunar missions as a technology capable of providing a higher specific energy (i.e., W∙h/kg) than state-of-the-art packaged Li-ion battery systems. An RFC consists of the (1 & 2) electrochemical stacks (chemical to electrical energy conversion to supply electricity to an external load, i.e. the fuel cell reaction, and electrical to chemical energy conversion of supplied electrical power to dissociate water into hydrogen and oxygen gases, i.e. water electrolysis), (3) fluidic conditioning, (4) reactant storage, (5) avionics, (6) power management and distribution (PMAD), and (7) thermal management. NASA’s Glenn Research Center has designed, assembled, and tested a breadboard RFC sys-tem capable of operating autonomously for multiple simulated lunar day/night cycles in a laboratory environment. The system is comprised of a non-flow through proton exchange membrane (PEM) fuel cell stack and a liquid-anode feed PEM electrolyzer (EZ) stack designed to electrochemically compress the reactants at balanced pressures up to 12.4 MPa (1800 psia). The fluidic conditioning, avionics, PMAD, and thermal management sub-systems are largely comprised of commercial-off-the-shelf components for this system-level development effort. The hardware is controlled by a CubeSat space processor running an operational program based on core flight architecture that can control the RFC hardware autonomously through a state machine with fault monitoring. The testing results highlighted here were completed with the system in an open-loop configuration such that reactants generated through water electrolysis were vented while gas cylinders supplied fuel cell operation. The breadboard operated autonomously, but there were five unplanned transitions to a safe state that required a manual restart after reviewing the data, determining a root cause, and implementing a solution. Four of the transitions were caused by the thermal management subsystem and the fifth was caused by a water management control issue in the EZ sub-system. The RFC system operated for over 550 hours with the final cycle being slightly abbreviated due to reasons unrelated to system performance.

Kerrigan Cain↗
NASA NTRS2003

Unitized Regenerative Fuel Cell System Development

Unitized Regenerative Fuel Cells (URFC) have recently been developed by several fuel cell manufacturers. These manufacturers have concentrated their efforts on the development of the cell stack technology itself, and have not up to this point devoted much effort to the design and development of the balance of plant. A fuel cell technology program at the Glenn Research Center (GRC) that has as its goal the definition and feasibility testing of the URFC system balance of plant. Besides testing the feasibility, the program also intends to minimize the system weight, volume, and parasitic power as its goal. The design concept currently being developed uses no pumps to circulate coolant or reactants, and minimizes the ancillary components to only the oxygen and hydrogen gas storage tanks, a water storage tank, a loop heat pipe to control the temperature and two pressure control devices to control the cell stack pressures during operation. The information contained in this paper describes the design and operational concepts employed in this concept. The paper also describes the NASA Glenn research program to develop this concept and test its feasibility.

Burke, Kenneth A.↗
NASA NTRS2019

Characterization of IM7/8552 Thin-Ply and Hybrid Thin-Ply Composites

Composite materials have increasingly been used for aerospace applications due to improved performance and reduced weight compared to their metallic counterparts. Inclusion of thin-ply material, plies with cured thickness half or less than standard composites, have potential to improve performance and reduce structural weight. Limited characterization of thin-ply IM7/8552 material in 30 and 70 grams per square meter fiber areal weights has been carried out using a series of selected American Society for Testing and Materials (ASTM) tests. Tests included unnotched tension, unnotched compression, v-notched rail shear, open-hole tension, and open-hole compression. Unidirectional, cross-ply, quasiisotropic and hybrid hard laminates were included in the study, and were compared to standard-ply laminates. Properties compared include fiber volume, laminate moduli, and failure strength, with failure modes also being examined. The thin-ply specimens exhibited similar or superior performance to standard ply laminates in many of the cases compared. Improvements in strength for laminates containing thin-ply material were seen for unidirectional laminates under unnotched tension, quasi-isotropic laminates under unnotched tension and compression, and hard laminates under open hole tension. Additional investigation is required to determine appropriate ply stacking rules for hybrids of thin and standard plies to avoid undesirable failure modes such as axial splitting. However, the observed performance improvements demonstrated by the conducted ASTM tests of hybrid thin-ply hard laminates could have benefits for improved structural weight in aircraft.

Lovejoy, Andrew E.↗
NASA NTRS1992

Extra high speed modified Lundell alternator parameters and open/short-circuit characteristics from global 3D-FE magnetic field solutions

The combined magnetic vector potential - magnetic scalar potential method of computation of 3D magnetic fields by finite elements, introduced in a companion paper, is used for global 3D field analysis and machine performance computations under open-circuit and short-circuit conditions for an example 14.3 kVA modified Lundell alternator, whose magnetic field is of intrinsic 3D nature. The computed voltages and currents under these machine test conditions were verified and found to be in very good agreement with corresponding test data. Results of use of this modelling and computation method in the study of a design alteration example, in which the stator stack length of the example alternator is stretched in order to increase voltage and volt-ampere rating, are given here. These results demonstrate the inadequacy of conventional 2D-based design concepts and the imperative of use of this type of 3D magnetic field modelling in the design and investigation of such machines.

Wang, R.↗
NASA NTRS2003

Thermal/Mechanical Durability of Polymer-Matrix Composites in Cryogenic Environments

In order to increase the reliability of the next generation of space transportation systems, the mechanical behavior of polymeric-matrix composite (PMC) materials at cryogenic temperatures must be investigated. This paper presents experimental data on the residual mechanical properties of a carbon fiber polymeric composite, IM7/PETI-5 as a function of temperature and aging. Tension modulus and strength were measured at room temperature, -196 C, and -269 C on five different specimens ply lay-ups. Specimens were preconditioned with one set of coupons being isothermally aged for 576 hours at -184 C, in an unloaded state. Another set of corresponding coupons were mounted in constant strain fixtures such that a constant uniaxial strain was applied to the specimens for 576 hours at -184 C. A third set was mechanically cycled in tension at -184 C. The measured properties indicated that temperature, aging, and loading mode can all have significant influence on performance. Moreover, this influence is a strong function of laminate stacking sequence. Thermal-stress calculations based on lamination theory predicted that the transverse tensile ply stresses could be quite high for cryogenic test temperatures. Microscopic examination of the surface morphology showed evidence of degradation along the exposed edges of the material because of aging at cryogenic temperatures. ________________

Gates, Thomas S.↗
NASA NTRS2007

The Ares I-1 Flight Test--Paving the Road for the Ares I Crew Launch Vehicle

In accordance with the U.S. Vision for Space Exploration and the nation's desire to again send humans to explore beyond Earth orbit, NASA has been tasked to send human beings to the moon, Mars, and beyond. It has been 30 years since the United States last designed and built a human-rated launch vehicle. NASA is now building the Ares I crew launch vehicle, which will loft the Orion crew exploration vehicle into orbit, and the Ares V cargo launch vehicle, which will launch the Lunar Surface Access Module and Earth departure stage to rendezvous Orion for missions to the moon. NASA has marshaled unique resources from the government and private sectors to perform the technically and programmatically complex work of delivering astronauts to orbit early next decade, followed by heavy cargo late next decade. Our experiences with Saturn and the Shuttle have taught us the value of adhering to sound systems engineering, such as the "test as you fly" principle, while applying aerospace best practices and lessons learned. If we are to fly humans safely aboard a launch vehicle, we must employ a variety of methodologies to reduce the technical, schedule, and cost risks inherent in the complex business of space transportation. During the Saturn development effort, NASA conducted multiple demonstration and verification flight tests to prove technology in its operating environment before relying upon it for human spaceflight. Less testing on the integrated Shuttle system did not reduce cost or schedule. NASA plans a progressive series of demonstration (ascent), verification (orbital), and mission flight tests to supplement ground research and high-altitude subsystem testing with real-world data, factoring the results of each test into the next one. In this way, sophisticated analytical models and tools, many of which were not available during Saturn and Shuttle, will be calibrated and we will gain confidence in their predictions, as we gain hands-on experience in operating the first of two new launch vehicle systems. The Ares I-1 flight test vehicle (FTV) will incorporate a mix of flight and mockup hardware, reflecting a configuration similar in mass, weight, and shape (outer mold line or OML) to the operational vehicle. It will be powered by a four-segment reusable solid rocket booster (RSRB), which is currently in Shuttle inventory, and will be modified to include a fifth, inert segment that makes it approximately the same size and weight as the five segment RSRB, which will be available for the second flight test in 2012. The Ares I-1 vehicle configuration is shown. Each test flight has specific objectives appropriate to the design analysis cycle in progress. The Ares I-1 demonstration test, slated for April 2009, gives NASA its first opportunity to gather critical data about the flight dynamics of the integrated launch vehicle stack, understand how to control its roll during flight, and other characterize the severe stage separation environment that the upper stage will experience during future operational flights. NASA also will begin the process of modifying the launch infrastructure and fine-tuning ground and mission operational scenarios, as NASA transitions from the Shuttle to the Ares/Orion system.

Davis, Stephan R.↗
NASA NTRS2008

Ares I-X Flight Test - The Future Begins Here

In less than two years, the National Aeronautics and Space Administration (NASA) will launch the Ares I-X mission. This will be the first flight of the Ares I crew launch vehicle, which, together with the Ares V cargo launch vehicle, will eventually send humans to the Moon, Mars, and beyond. As the countdown to this first Ares mission continues, personnel from across the Ares I-X Mission Management Office (MMO) are finalizing designs and fabricating vehicle hardware for an April 2009 launch. This paper will discuss the hardware and programmatic progress of the Ares I-X mission. Like the Apollo program, the Ares launch vehicles will rely upon extensive ground, flight, and orbital testing before sending the Orion crew exploration vehicle into space with humans on board. The first flight of Ares I, designated Ares I-X, will be a suborbital development flight test. Ares I-X gives NASA its first opportunity to gather critical data about the flight dynamics of the integrated launch vehicle stack; understand how to control its roll during flight; better characterize the severe stage separation environments that the upper stage engine will experience during future operational flights; and demonstrate the first stage recovery system. NASA also will begin modifying the launch infrastructure and fine-tuning ground and mission operations, as the agency makes the transition from the Space Shuttle to the Ares/Orion system.

Davis, Stephan R.↗
NASA NTRS2011

Modeling Powered Aerodynamics for the Orion Launch Abort Vehicle Aerodynamic Database

Modeling the aerodynamics of the Orion Launch Abort Vehicle (LAV) has presented many technical challenges to the developers of the Orion aerodynamic database. During a launch abort event, the aerodynamic environment around the LAV is very complex as multiple solid rocket plumes interact with each other and the vehicle. It is further complicated by vehicle separation events such as between the LAV and the launch vehicle stack or between the launch abort tower and the crew module. The aerodynamic database for the LAV was developed mainly from wind tunnel tests involving powered jet simulations of the rocket exhaust plumes, supported by computational fluid dynamic simulations. However, limitations in both methods have made it difficult to properly capture the aerodynamics of the LAV in experimental and numerical simulations. These limitations have also influenced decisions regarding the modeling and structure of the aerodynamic database for the LAV and led to compromises and creative solutions. Two database modeling approaches are presented in this paper (incremental aerodynamics and total aerodynamics), with examples showing strengths and weaknesses of each approach. In addition, the unique problems presented to the database developers by the large data space required for modeling a launch abort event illustrate the complexities of working with multi-dimensional data.

Chan, David T.↗
NASA NTRS2004

Data Management for Mars Exploration Rovers

Data Management for the Mars Exploration Rovers (MER) project is a comprehensive system addressing the needs of development, test, and operations phases of the mission. During development of flight software, including the science software, the data management system can be simulated using any POSIX file system. During testing, the on-board file system can be bit compared with files on the ground to verify proper behavior and end-to-end data flows. During mission operations, end-to-end accountability of data products is supported, from science observation concept to data products within the permanent ground repository. Automated and human-in-the-loop ground tools allow decisions regarding retransmitting, re-prioritizing, and deleting data products to be made using higher level information than is available to a protocol-stack approach such as the CCSDS File Delivery Protocol (CFDP).

Mars missions↗
NASA NTRS1988

Space shuttle phase B wind tunnel model and test information. Volume 3: Launch configuration

Archived wind tunnel test data are available for flyback booster or other alternate recoverable configuration as well as reusable orbiters studied during initial development (Phase B) of the Space Shuttle, including contractor data for an extensive variety of configurations with an array of wing and body planforms. The test data have been compiled into a database and are available for application to current winged flyback or recoverable booster aerodynamic studies. The Space Shuttle Phase B Wind Tunnel Database is structured by vehicle component and configuration. Basic components include booster, orbiter, and launch vehicle. Booster configuration types include straight and delta wings, canard, cylindrical, retroglide and twin body. Orbiter configurations include straight and delta wings, lifting body, drop tanks and double delta wings. Launch configurations include booster and orbiter components in various stacked and tandem combinations. The digital database consists of 220 files containing basic tunnel data. Database structure is documented in a series of reports which include configuration sketches for the various planforms tested. This is Volume 3 -- launch configurations.

Glynn, J. L.↗
NASA NTRS2010

Objectives and Progress on Ground Vibration Testing for the Ares Projects

Integrated vehicle ground vibration testing (IVGVT) will be a vital component for ensuring the safety of NASA s next generation of exploration vehicles to send human beings to the Moon and beyond. A ground vibration test (GVT) measures the fundamental dynamic characteristics of launch vehicles during various phases of flight. The Ares Flight & Integrated Test Office (FITO) will be conducting the IVGVT for the Ares I crew launch vehicle at Marshall Space Flight Center (MSFC) from 2012 to 2014 using Test Stand (TS) 4550. MSFC conducted similar GVT for the Saturn V and Space Shuttle vehicles. FITO will perform the IVGVT on the Ares I crew launch vehicle, which will lift the Orion crew exploration vehicle to low Earth orbit, and the Ares V cargo launch vehicle, which can launch the lunar lander into orbit and send the combined Orion/lander vehicles toward the Moon. Ares V consists of a six-engine core stage with two solid rocket boosters and an Earth departure stage (EDS). The same engine will power the EDS and the Ares I second stage. The current plan is to test six configurations in three unique test positions inside TS 4550. Four Ares I second stage test configurations will be tested in Position 3, consisting of the Upper Stage and Orion crew module in four nominal conditions: J-2X engine ignition, post Launch Abort System (LAS) jettison, critical slosh mass, and J-2X burn-out. Position 2 consists of the entire launch stack at first stage burn-out (using empty first stage segments). Position 1 represents the entire launch stack at lift-off (using inert first stage segments). Because of long disuse, TS 4550 is being repaired and modified for reactivation to conduct the Ares I IVGVT. The Shuttle-era platforms have been removed and are being replaced with mast climbers that provide ready access to the test articles and can be moved easily to support different positions within the test stand. Two new cranes will help move test articles at the test stand and at the Redstone Arsenal rail-head where first stage segments will be received in late 2010. The electrical system for TS 4550 also will be upgraded. The Hydraulic Support Systems (HDSs) used for Saturn and Shuttle are being disassembled and evaluated for use during IVGVT. Analyses indicate that the 45-year-old HDSs can be refurbished to support the Ares I IVGT. An alternate concept for a pneumatic suspension system is also being explored. A decision on which suspension system configuration to use for IVGVT will be made in 2010.

Tuma, Margaret L.↗
NASA NTRS1989

Experimental studies of adaptive structures for precision performance

An experimental study was made of the adaptive structure concept. Experimental data were obtained for a three-longeron, thirteen-bay truss-type test structure. This test structure can be softly suspended as well as rigidly clamped at the central bay. The load-carrying active member consists of a stack of concentric piezoelectric wafers, an eddy current displacement sensor, and a strain gage force sensor. A bridge (or compound) feedback technique developed in communication engineering is applied to the problem of active damping augmentation in adaptive structures. Using collocated force and velocity feedback around the active member, a desired output mechanical impedance can be implemented to maximize energy absorption by the active members. In addition, large gains can be implemented to linearize the active member's nonlinear behavior. Good agreements with linear finite element analysis was found for both static and dynamic structural responses. An 11 percent damping in the first bending mode was demonstrated in the closed-loop damping experiment.

Chen, G.-S.↗
NASA NTRS2007

A Microfabricated Segmented-Involute-Foil Regenerator for Enhancing Reliability and Performance of Stirling Engines

An actual-size microfabricated regenerator comprised of a stack of 42 disks, 19 mm diameter and 0.25 mm thick, with layers of microscopic, segmented, involute-shaped flow channels was fabricated and tested. The geometry resembles layers of uniformly-spaced segmented-parallel-plates, except the plates are curved. Each disk was made from electro-plated nickel using the LiGA process. This regenerator had feature sizes close to those required for an actual Stirling engine but the overall regenerator dimensions were sized for the NASA/Sunpower oscillating-flow regenerator test rig. Testing in the oscillating-flow test rig showed the regenerator performed extremely well, significantly better than currently used random-fiber material, producing the highest figures of merit ever recorded for any regenerator tested in that rig over its approximately 20 years of use.

Ibrahim, Mounir↗
NASA NTRSDate not supplied

Error Localization Examples: Looking for a Needle in a Hay-stack

Finite element models (FEM) are routinely developed and used during fabrication of high dollar-value hardware. NASA as part of the pre-flight certification of launch vehicles routinely conducts vibration and static tests to calibrate models used for flight-risk assessments. As part of the calibration process, certain areas in the model are modified, using engineering judgment and sensitivity analysis, to match the test results. Unfortunately, tools to identify problem areas in the FEM using test data directly are scarce. Over the years, Error Localization Algorithms (ELA) have been proposed with very limited success. Recently, the Analytical Dynamics Model Improvement (ADMI) algorithm, which computes closed-form mass and stiffness corrections to match the test data exactly, have been shown to be effective for error localization. The paper will present several FEM example problems where ELA is used with simulated test data to determine FEM problem areas. For each example, the correct answer is shown along with ELA results. It is shown that the ELA process is able to identify general problem areas in the FEM, which are consistent with known model perturbations. However, in most cases the ELA identified area of improvement is larger than the true answer. Nonetheless, with proper optimization tools, calibration results using the ELA identified areas provide excellent results.

error localization↗