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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 775 records · Page 43

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NASA NTRS1975

Modal test - Measurement and analysis requirements

Data from the Viking Orbiter Modal Test Program are used to illustrate modal test measurement and analysis requirements. The test was performed using a multiple shake dwell technique where data were acquired one channel at a time and recorded on paper tape. Up to ten shakers were used simultaneously, with a complete set of data consisting of 290 strain-gage readings and 125 accelerometer readings. The data analysis provided information sufficient to minimize errors in the data. The list of analyses in order of value is orthogonality, residual mass, frequency sweep, data checks to assure good test data, multilevel trends, global kinetic energy, and global strain energy.

Wada, B. K.↗

NASA NTRS1981

An optimization model for energy generation and distribution in a dynamic facility

An analytical model is described using linear programming for the optimum generation and distribution of energy demands among competing energy resources and different economic criteria. The model, which will be used as a general engineering tool in the analysis of the Deep Space Network ground facility, considers several essential decisions for better design and operation. The decisions sought for the particular energy application include: the optimum time to build an assembly of elements, inclusion of a storage medium of some type, and the size or capacity of the elements that will minimize the total life-cycle cost over a given number of years. The model, which is structured in multiple time divisions, employ the decomposition principle for large-size matrices, the branch-and-bound method in mixed-integer programming, and the revised simplex technique for efficient and economic computer use.

Lansing, F. L.↗

NASA NTRS1995

Dual Wall Angles Would Enhance Performance Of A Solar Pond

Proposed dual-angle design for Sun-facing wall of solar pond enhances solar-energy-storage performance of pond; increase in performance over that of similar pond with conventional (single-angle) wall estimated to be 25 percent. Design compromises between maximizing heating and minimizing convection. Top part of Sun-facing wall optimized for top colder layer of water, less tendency toward convective mixing. Bottom part of wall optimized for bottom, warmer layer of water, greater tendency towards convection. Optimization involves consideration of both anticipated temperature-vs.-depth profile (affects tendency toward convection) and latitude (affects angle of incidence of solar radiation and rate of heating).

Noever, David A.↗

NASA NTRS2006

Development of a Liner Design Methodology and Relevant Results of Acoustic Suppression in the Farfield for Mixer-Ejector Nozzles

We have developed a process to predict noise field interior to the ejector and in the farfield for any liner design for a mixer-ejector of arbitrary scale factor. However, a number of assumptions, not verified for the current application, utilized in this process, introduce uncertainties in the final result, especially, on a quantitative basis. The normal impedance model for bulk with perforated facesheet is based on homogeneous foam materials of low resistivity. The impact of flow conditions for HSCT application as well as the impact of perforated facesheet on predicted impedance is not properly accounted. Based on the measured normal impedance for deeper bulk samples (i.e., 2.0 in.) the predicted reactance is much higher compared to the data at frequencies above 2 kHz for T-foam and 200 ppi SiC. The resistance is under predicted at lower frequencies (below 4 kHz) for these samples. Thus, the use of such predicted data in acoustic suppression is likely to introduce inaccuracies. It should be noted that the impedance prediction methods developed recently under liner technology program are not utilized in the studies described in this report due to the program closeout. Acoustic suppression prediction is based on the uniform flow and temperature conditions in a two-sided treated constant area rectangular duct. In addition, assumptions of equal energy per mode noise field and interaction of all frequencies with the treated surface for the entire ejector length may not be accurate. While, the use of acoustic transfer factor minimizes the inaccuracies associated with the prediction for a known test case, the assumption of the same factor for other liner designs and with different linear scale factor ejectors seems to be very optimistic. As illustrated in appendix D that the predicted noise suppression for LSM-1 is lower compared to the measured data is an indication of the above argument. However, the process seems to be more reliable when used for the same scale models for different liner designs as demonstrated for Gen. 1 mixer-ejectors.

Salikuddin, M.↗

NASA NTRS2010

Material Properties of Three Candidate Elastomers for Space Seals Applications

A next-generation docking system is being developed by the National Aeronautics and Space Administration (NASA) to support Constellation Space Exploration Missions to low Earth orbit (LEO), to the Moon, and to Mars. A number of investigations were carried out to quantify the properties of candidate elastomer materials for use in the main interface seal of the Low Impact Docking System (LIDS). This seal forms the gas pressure seal between two mating spacecraft. Three candidate silicone elastomer compounds were examined: Esterline ELA-SA-401, Parker Hannifin S0383-70, and Parker Hannifin S0899-50. All three materials were characterized as low-outgassing compounds, per ASTM E595, so as to minimize the contamination of optical and solar array systems. Important seal properties such as outgas levels, durometer, tensile strength, elongation to failure, glass transition temperature, permeability, compression set, Yeoh strain energy coefficients, coefficients of friction, coefficients of thermal expansion, thermal conductivity and diffusivity were measured and are reported herein.

Bastrzyk, Marta B.↗

NASA NTRS2013

NASA Collaborative Research on the Ultra High Bypass Engine Cycle and Potential Benefits for Noise, Performance, and Emissions

The National Aeronautics and Space Administration has taken an active role in collaborative research with the U.S. aerospace industry to investigate technologies to minimize the impact of aviation on the environment. In December 2006, a new program, called the Fundamental Aeronautics Program, was established to enhance U.S. aeronautics technology and conduct research on energy, efficiency and the environment. A project within the overall program, the Subsonic Fixed Wing Project, was formed to focus on research related to subsonic aircraft with specific goals and time based milestones to reduce aircraft noise, emissions and fuel burn. This paper will present an overview of the Subsonic Fixed Wing Project environmental goals and describe a segment of the current research within NASA and also were worked collaboratively with partners from the U.S. aerospace industry related to the next generation of aircraft that will have lower noise, emissions and fuel burn.

Hughes, Christopher E.↗

NASA NTRS2026

Understanding and Controlling Hybrid Electric Gas Turbine Engine Transient Dynamics

The electrification of the gas turbine engine is known to increase the flexibility of aircraft architectures by enabling the generation of electrical power to distribute to other electrically based, thrust producing subsystems. It also has potential for direct performance benefits in the gas turbine engine itself, both at steady state and dynamically. Although the design focus of the gas turbine engine performance is primarily at steady state, it is often the instabilities occurring during transients that cause disequilibrium and constrain performance improvements. Instabilities arise due to the disequilibrium of the energy storage mechanisms within the traditional engine system and likewise for the electrified engine system. The primary energy storage mechanisms in the traditional system are the rotational inertia, gas path volumes, the thermal masses that make up the mechanical structure, and now, the electrical power system will provide additional contributions. Understanding the effect each of these energy storage mechanisms has on the others and controlling them appropriately allows for the suppression of state changes within the turbomachinery components to the degree that the components remain near steady state, thus reducing the disequilibrium within the system. The ability to tightly regulate the state changes of turbomachinery components, such as the compressor, minimizes the excursion of the compressor operating point from the operating line (operability), allowing for higher performing, more efficient compressor designs by decreasing the amount of stall margin needed for safe engine power level changes. Preliminary studies with the electrification of the turbine engine have shown that this is possible, and this concept can lead to design trades benefitting engine performance, weight, and volume. This paper explores in detail the energy storage mechanisms and control approaches for coordinating their state changes, and ultimately proposes that a higher performing, more efficient compressor design can result.

transient dynamics↗

NASA NTRS1999

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Edwards, David L.↗

NASA NTRS2016

Communication in Pipes Using Acoustic Modems that Provide Minimal Obstruction to Fluid Flow

A plurality of phased array acoustic communication devices are used to communicate data along a tubulation, such as a well. The phased array acoustic communication devices employ phased arrays of acoustic transducers, such as piezoelectric transducers, to direct acoustic energy in desired directions along the tubulation. The system is controlled by a computer-based controller. Information, including data and commands, is communicated using digital signaling.

Bar-Cohen, Yoseph↗

NASA NTRS1977

A hard X-ray imaging instrument for solar and cosmic sources

A hard X-ray imaging instrument is described which is capable of high-resolution imaging of solar and cosmic hard X-ray sources between 2 and 80 keV during Shuttle sortie flights. The properties of solar burst sources and the resulting instrument requirements are discussed. The instrument envelope of 1.2 x 1.2 x 3.0 meters includes a tungsten multigrid collimator which has 4-arcsec resolution, a 40-arcmin response envelope and a point-source effective area of 26 sq cm. A combination of periodic fan beams and nonperiodic pencil beams enables a unique deconvolution to be achieved within a 128 x 128 arcsec field without mechanical scanning. The detector system is a set of direct-readout 40 atm-cm xenon-filled proportional counters designed to minimize background. The instrument is capable of refurbishment to optimize the collimator configuration for specific solar or cosmic scientific objectives, to upgrade the angular resolution, or to extend the high-energy response.

Hurford, G. J.↗

NASA NTRS1980

STS-1 operational flight profile. Volume 5: Descent, cycle 3

The trajectory data presented are to be used for orbiter systems and subsystems evalation, flight and mission control center software verification, flight techniques and timeline development, crew training, and evaluation of operational mission suitability. The entry profile is very similar to cycle 2, however, elevon and body flap temperature margins have increased and the elevon schedule was changed. The terminal area energy management (TAEM) profile was completely reshaped to conform with new angle of attack constraints and left hand turn around the heading alignment cylinder. Also, the entry/TAEM interface was adjusted to minimize guidance induced angle of attack transients across the interface. The approach and landing phase was reshaped for a 20 deg glideslope and reduced velocity at touchdown. The definition of the runway threshold was standardized for all landing sites. This results in a shift at Edwards Air Force Base in aim points and touchdown relative to the threshold of 1000 feet. The rollout remains essentially unchanged with the exception of the speedbrake, which is now deployed to 50 percent at touchdown.

Moore, R.↗

NASA NTRS1989

The role of computerized modeling and simulation in the development of life support system technologies

Computerized modeling and simulation (CMAS) is a tool that can greatly reduce both the time and cost of technology development. CMAS refers to computer methods for correlating, storing, and retrieving property data for chemical species and for solving the phenomenological equations of physical/chemical processes. Furthermore, process conditions based on properties of materials, mass, and energy balances; equipment sizing based on rate processes; and the governing equations for unit operations can be determined using CMAS. CMAS systems can be used to evaluate an LSS process with minimal requirements for laboratory experimentation. A CMAS model is presented for a vapor compression distillation system(VCD) for reclaiming water from urine.

Modell, Michael↗

NASA NTRS1991

Advances in modeling the pressure correlation terms in the second moment equations

In developing turbulence models, various model constraints were proposed in an attempt to make the model equations more general (or universal). The most recent of these are the realizability principle, the linearity principle, the rapid distortion theory, and the material indifference principle. Several issues are discussed concerning these principles and special attention is payed to the realizability principle. Realizability (defined as the requirement of non-negative energy and Schwarz' inequality between any fluctuating quantities) is the basic physical and mathematical principle that any modeled equation should obey. Hence, it is the most universal, important and also the minimal requirement for a model equation to prevent it from producing unphysical results. The principle of realizability is described in detail, the realizability conditions are derived for various turbulence models, and the model forms are proposed for the pressure correlation terms in the second moment equations. Detailed comparisons of various turbulence models with experiments and direct numerical simulations are presented. As a special case of turbulence, the two dimensional two-component turbulence modeling is also discussed.

Shih, Tsan-Hsing↗

NASA NTRS1992

Advances in modeling the pressure correlation terms in the second moment equations

Shih, Tsan-Hsing↗

NASA NTRS1995

Electron excitation cross sections for the 2s(2)2p(3)4S(O) -- 2s(2)2p(3)2D(O) (forbidden) and 4S(O) -- 2s2p(4) 4P (resonance) transitions in O II

Experimental and theoretical excitation cross sections are reported for the first forbidden transition 4S(O) -- 2S(2)2p(3) 2D(O) (lambda-lambda 3726, 3729) and the first allowed (resonance) transition 4S(O) -- 2s2p(4) 4P(lambda-833) in O II. Use is made of electron energy loss and merged-beams methods. The electron energy range covered is 3.33 (threshold) to 15 eV for the S -- D transition, and 14.9 (threshold) to 40 eV for the S -- P transition. Care was taken to assess and minimize the metastable fraction of the O II beam. An electron mirror was designed and tested to reflect inelastically backscattered electrons into the forward direction to account for the full range of polar scattering angles. Comparisons are made between present experiments and 11-state R-matrix calculations. Calculations are also presented for the 4S(O) -- 2s(2)2p(3)2P(O) (lambda-2470) transition.

Zuo, M.↗

NASA NTRS2001

Solar Collector With Image-Forming Mirror Cavity to Irradiate Small Central Volume

A unique solar thermal chamber has been designed and fabricated to produce the maximum concentration of solar energy and higher temperature possible. Its primary purpose was for solar plasma propulsion experiments and related material specimen testing above 3000 K. The design not only maximized solar concentration, but also, minimized infrared heat loss. This paper provides the underlying theory and operation of the chamber and initial optical correlation to the actual fabricated hardware. The chamber is placed at the focal point of an existing primary concentrator with a 2.74 m (9 ft) focal length. A quartz lens focuses a small sun image at the inlet hole of the mirrored cavity. The lens focuses two image planes at prescribed positions; the sun at the cavity's entrance hole and the primary concentrator at the junction plane of two surfaces that form the cavity chamber. The back half is an ellipsoid reflector that produces a 1.27 cm diameter final sun image. The image is "suspended in space," 7.1 cm away from the nearest cavity surface, to minimize thermal and contaminate damage to the mirror surfaces. A hemisphere mirror makes up the front chamber and has its center of curvature at the target image, where rays leaving the target are reflected back upon themselves, minimizing radiation losses.

Buchele, Don↗

NASA NTRS2020

Free Space Optical Link Utilizing a Modulated Retro-Reflector Intended for Planetary Duplex Communication Links Between an Orbiter and Surface Unit

Presented are simulation and experimental results that provide duplex optical-free space communication links with minimal power and pointing requirements by using a modulated retro-reflector (MRR) for planetary communications. The design is the MRR resides on the surface of a planet or moon, where energy is scarce, while the source of the communication laser resides on an orbiter to achieve satellite-to-ground communications. Also, a simulated scenario using the Mars Reconnaissance Orbiter (MRO) is provided for real world potential results. The information sent through this communication path can range from raw scientific data to multimedia files such as videos and pictures. Bidirectional communications is established with the MRR by using a nested pulse position modulation (PPM) structure. This modulation scheme is then evaluated for its validity in a proof-of-concept experiment. Initial results indicate a promising return-link performance of at least 300 kbps in the nested arrangement.

Booth, Stephanie↗

NASA NTRS2023

Performance of High-Resolution Mo/Cu Transition Edge Sensors Fabricated Using a Lift-Off Process

The soft X-ray band below ≈0.5 keV is expected to provide rich information on metallicity, temperature, and distribution of hot gas in our galaxy and the intergalactic medium. Resolving these densely spaced emission lines requires energy resolution on the order of 1--2 eV. The low count rates from diffuse astrophysical sources also necessitate large collection areas, particularly for a sounding rocket instrument with short exposure times and limited resources. This translates to large pixel sizes (about 1 mm 2 ) for a reasonable number of read-out channels. To achieve the required energy resolution with 200 nm thin Au absorbers (heat capacity C about 1 pJ/K), we are developing TES microcalorimeters with very high temperature sensitivity (αI), low enough current sensitivity (βI), and minimal excess noise (M). Out of the various fabrication approaches for the TES bilayer we have explored, the lift-off approach (as pioneered for Mo/Au TES by Joel Weber at NIST) so far is the simplest to execute. The simple square TES geometries we have tested to date show promising results for αI and βI. Measured complex impedance and noise for bare devices without absorbers are well described by two-body thermal models and their excess noise is found to be consistent with predictions for mixed-down Johnson noise by Wessels et al. More sensitive measurements with larger heat capacity are planned to accurately determine excess noise. In this paper, we give an overview of the process and summarize results of our detailed characterization measurements for thermal conductance G, αI, βI, and noise for several devices across a range of bias points.

Felix T Jaeckel↗