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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 NTRS1991

Vapor crystal growth technology development: Application to cadmium telluride

Growth of bulk crystals by physical vapor transport was developed and applied to cadmium telluride. The technology makes use of effusive ampoules, in which part of the vapor contents escapes to a vacuum shroud through defined leaks during the growth process. This approach has the advantage over traditional sealed ampoule techniques that impurity vapors and excess vapor constituents are continuously removed from the vicinity of the growing crystal. Thus, growth rates are obtained routinely at magnitudes that are rather difficult to achieve in closed ampoules. Other advantages of this effusive ampoule physical vapor transport (EAPVT) technique include the predetermination of transport rates based on simple fluid dynamics and engineering considerations, and the growth of the crystal from close to congruent vapors, which largely alleviates the compositional nonuniformities resulting from buoyancy driven convective transport. After concisely reviewing earlier work on improving transport rates, nucleation control, and minimization of crystal wall interactions in vapor crystal growth, a detail account is given of the largely computer controlled EAPVT experimentation.

Rosenberger, Franz↗

NASA NTRS1992

Joint Workshop on New Technologies for Lunar Resource Assessment

The workshop included talks on NASA's and DOE's role in Space Exploration Initiative, lunar geology, lunar resources, the strategy for the first lunar outpost, and an industry perspective on lunar resources. The sessions focused on four major aspects of lunar resource assessment: (1) Earth-based remote sensing of the Moon; (2) lunar orbital remote sensing; (3) lunar lander and roving investigations; and (4) geophysical and engineering consideration. The workshop ended with a spirited discussion of a number of issues related to resource assessment.

Elphic, Rick C.↗

NASA NTRS1992

From Earth to Orbit: An assessment of transportation options

The report assesses the requirements, benefits, technological feasibility, and roles of Earth-to-Orbit transportation systems and options that could be developed in support of future national space programs. Transportation requirements, including those for Mission-to-Planet Earth, Space Station Freedom assembly and operation, human exploration of space, space science missions, and other major civil space missions are examined. These requirements are compared with existing, planned, and potential launch capabilities, including expendable launch vehicles (ELV's), the Space Shuttle, the National Launch System (NLS), and new launch options. In addition, the report examines propulsion systems in the context of various launch vehicles. These include the Advanced Solid Rocket Motor (ASRM), the Redesigned Solid Rocket Motor (RSRM), the Solid Rocket Motor Upgrade (SRMU), the Space Shuttle Main Engine (SSME), the Space Transportation Main Engine (STME), existing expendable launch vehicle engines, and liquid-oxygen/hydrocarbon engines. Consideration is given to systems that have been proposed to accomplish the national interests in relatively cost effective ways, with the recognition that safety and reliability contribute to cost-effectiveness. Related resources, including technology, propulsion test facilities, and manufacturing capabilities are also discussed.

Gavin, Joseph G., Jr.↗

NASA NTRS1992

SALSA - A lunar submillimeter-wavelength array

A conceptual design for a Synthesis Array for Lunar Submillimeter Astronomy (SALSA) is described with emphasis on information relevant to its implementation. SALSA is optimized to synthesize images of astronomical sources at wavelengths between 60 and 300 microns with an angular resolution of 10 milliarcseconds at the shortest wavelength. The discussion covers engineering considerations and descriptions of subsystems, including the environmental shield, antenna, and beam transport.

Mahoney, M. J.↗

NASA NTRS1993

Comment on tangential wave motion in unstable combustors

An attempt is made to gain insight into the injection boundary instability mechanism as captured by a simple computational tool developed for liquid rocket engines. Considerable evidence is generated supporting a hypothesis that destructive tangential-mode instabilities in liquid-fuel combustors are driven by combustion processes occurring at the propellant-wetted injector face. The driving action is found to be directly analogous to a burning solid propellant surface mechanism, responsible for solid rocket motor instabilities. Since the proposed instability mechanism has not been fundamentally confirmed, experimental research is strongly recommended.

Litchford, Ron J.↗

NASA NTRS1993

Imaging spectrometry of the Earth and other solar system bodies

Imaging spectrometry is a relatively new tool for remote sensing of the Earth and other bodies of the solar system. The technique dates back to the late 1970's and early 1980's. It is a natural extension of the earlier multi-spectral imagers developed for remote sensing that acquire images in a few, usually broad spectral bands. Imaging spectrometers combine aspects of classical spectrometers and imaging systems, making it possible to acquire literally hundreds of images of an object, each image in a separate, narrow spectral band. It is thus possible to perform spectroscopy on a pixel-by-pixel basis with the data acquired with an imaging spectrometer. Two imaging spectrometers have flown in space and several others are planned for future Earth and planetary missions. The French-built Phobos Infrared Spectrometer (ISM) was part of the payload of the Soviet Mars mission in 1988, and the JPL-built Near Infrared Mapping Spectrometer (NIMS) is currently en route to Jupiter aboard the Galileo spacecraft. Several airborne imaging spectrometers have been built in the past decade including the JPL-built Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) which is the only such sensor that covers the full solar reflected portion of the spectrum in narrow, contiguous spectral bands. NASA plans two imaging spectrometers for its Earth Observing System, the Moderate and the High Resolution Imaging Spectrometers (MODIS and HIRIS). A brief overview of the applications of imaging spectrometry to Earth science will be presented to illustrate the value of the tool to remote sensing and indicate the types of measurements that are required. The system design for AVIRS and a planetary imaging spectrometer will be presented to illustrate the engineering considerations and challenges that must be met in building such instruments. Several key sensor technology areas will be discussed in which miniaturization and/or enhanced performance through micromachining and nanofabrication may allow smaller, more robust, and more capable imaging spectrometers to be built in the future.

Vane, Gregg↗

NASA NTRS1994

Pressure loss modulus correlation for Delta p across uniformly distributed-loss devices

A dimensionless group, called a pressure loss modulus (N(sub PL)), is introduced that, in conjunction with an appropriately defined Reynolds number, is of considerable engineering utility in correlating steady-state Delta p vs flow calibration data and subsequently as a predictor, using the same or a different fluid, in uniformly distributed pressure loss devices. It is particularly useful under operation in the transition regime. Applications of this simple bivariate correlation to three diverse devices of particular interest for small liquid rocket engine fluid systems are discussed: large L/D capillary tube restrictors, packed granular catalyst beds, and stacked vortex-loss disk restrictors.

Nunz, Gregory J.↗

NASA NTRS1999

Parallelizing OVERFLOW: Experiences, Lessons, Results

The computer code OVERFLOW is widely used in the aerodynamic community for the numerical solution of the Navier-Stokes equations. Current trends in computer systems and architectures are toward multiple processors and parallelism, including distributed memory. This report describes work that has been carried out by the author and others at Ames Research Center with the goal of parallelizing OVERFLOW using a variety of parallel architectures and parallelization strategies. This paper begins with a brief description of the OVERFLOW code. This description includes the basic numerical algorithm and some software engineering considerations. Next comes a description of a parallel version of OVERFLOW, OVERFLOW/PVM, using PVM (Parallel Virtual Machine). This parallel version of OVERFLOW uses the manager/worker style and is part of the standard OVERFLOW distribution. Then comes a description of a parallel version of OVERFLOW, OVERFLOW/MPI, using MPI (Message Passing Interface). This parallel version of OVERFLOW uses the SPMD (Single Program Multiple Data) style. Finally comes a discussion of alternatives to explicit message-passing in the context of parallelizing OVERFLOW.

Jespersen, Dennis C.↗

NASA NTRS2001

The Isothermal Dendritic Growth Experiment (IDGE)

Dendritic solidification is one of the simplest examples of pattern formation where a structureless melt evolves into a ramified crystalline microstructure; it is a common mode of solidification in many materials, but especially so in metals and alloys. There is considerable engineering interest in dendrites because of the role dendrites play in the determination of microstructure, and thereby in influencing the physical properties of cast metals and alloys. Dendritic solidification provides important examples of non-equilibrium physics, pattern formation dynamics, and models for computational condensed matter and material physics. Current theories of dendritic growth generally couple diffusion effects in the melt with the physics introduced by the interface. Unfortunately, in terrestrial based experiments, convective effects in the melt alter the growth process in such a manner as to prevent definitive analysis of convective, diffusive or interfacial effects. Thus, the effective elimination of convection in the melt by operating experiments on orbit were required to produce high-fidelity data needed for achieving further progress. This simple fact comprised the scientific justification for the IDGE.

Glicksman, M. E.↗

NASA NTRS1995

Review of the PDWA Concept for Combustion Enhancement in a Supersonic Air-Breathing Combustor Environment

This paper reviews the design of the Pulsed Detonation Wave Augmentor (PDWA) concept and the preliminary computational fluid dynamics studies that supported it. The PDWA relies on the rapid generation of detonation waves in a small tube, which are then injected into the supersonic stream of the main combustor. The blast waves thus generated are used to stimulate the mixing and combustion inside the main combustor. The mixing enhancement relies on various forms of the baroclinic interaction, where misaligned pressure and density gradients combine to produce vortical flow. By using unsteady shock waves, the concept also uses the Richtmyer-Meshkov effect to further increase the rate of mixing. By carefully designing the respective configurations of the combustor and the detonation tubes, one can also increase the penetration of the fuel into the supersonic air stream. The unsteady shocks produce lower stagnation pressure losses than steady shocks. Combustion enhancement can also be obtained through the transient shock-heating of the fuel-air interface, and the lowering of the ignition delay in these regions. The numerical simulations identify these processes, and show which configurations give the best results. Engineering considerations are also presented, and discuss the feasibility of the concept. Of primary importance are the enhancements in performance, the design simplicity, the minimization of the power, cost, and weight, and the methods to achieve very rapid cycling.

Canbier, Jean-Luc↗

NASA NTRS2004

Small Crater Morphology Within Gusev Crater and Isidis Planitia: Evidence for Widespread Secondaries on Mars

Large (greater than 2 km diameter) impact craters on the martian surface have been extensively studied and modeled. Craters smaller than this were known to exist but the lack of high-resolution images prevented detailed measurements and descriptions. Images obtained by the Mars Orbiter Camera (MOC) on Mars Global Surveyor are of sufficient resolution to perform detailed studies on the morphology of small (less than 1 km diameter) craters. Previous workers have suggested that many of these small craters are secondary craters; while others maintain that they represent primary impacts. The difference is significant, however, because of implications for surface age, climate change, impact generated regolith, provenance of surface rocks, engineering considerations (landing safety and rover trafficability), and the origin of martian meteorites.

Hurst, M.↗

NASA NTRS2005

MTRAP: The Magnetic Transition Region Probe

The Magnetic Transition Region Probe is a space telescope designed to measure the magnetic field at several heights and temperatures in the solar atmosphere, providing observations spanning the chromospheric region where the field is expected to become force free. The primary goal is to provide an early warning system (hours to days) for solar energetic particle events that pose a serious hazard to astronauts in deep space and to understand the source regions of these particles. The required magnetic field data consist of simultaneous circular and linear polarization measurements in several spectral lines over the wavelength range from 150 to 855 nm. Because the observations are photon limited an optical telescope with a large (>18sq m) collecting area is required. To keep the heat dissipation problem manageable we have chosen to implement MTRAP with six separate Gregorian telescopes, each with approx. 3 sq m collecting area, that are brought to a common focus. The large field of view (5 x 5 arcmin(sup 2)) and angular resolution (0.025 arcsec pixels) require large detector arrays and, because of the requirements on signal to noise (10(exp 3)), pixels with large full well depths to reduce the readout time and improve the temporal resolution. The optical and engineering considerations that have gone into the development of a concept that meets MTRAP's requirements are described.

Davis, J. M.↗

NASA NTRS2008

The NASA Engineering and Safety Center (NESC) GN and C Technical Discipline Team (TDT): Its Purpose, Practices and Experiences

This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this team operates and engages in its objective engineering and safety assessments of critical NASA projects. This paper will then describe key issues and findings from several of the recent GN&C-related independent assessments and consultations performed and/or supported by the NESC GN&C TDT. Among the examples of the GN&C TDT s work that will be addressed in this paper are the following: the Space Shuttle Orbiter Repair Maneuver (ORM) assessment, the ISS CMG failure root cause assessment, the Demonstration of Autonomous Rendezvous Technologies (DART) spacecraft mishap consultation, the Phoenix Mars lander thruster-based controllability consultation, the NASA in-house Crew Exploration Vehicle (CEV) Smart Buyer assessment and the assessment of key engineering considerations for the Design, Development, Test & Evaluation (DDT&E) of robust and reliable GN&C systems for human-rated spacecraft.

Dennehy, Cornelius J.↗

NASA NTRS2008

Multi-Layer Insulation Debris Sightings on Orbit

I would like to discuss a topic that has affected many previous white-light coronagraphs as well as the HI1 instruments on STEREO. By design, all of these instruments are extremely sensitive to very faint sources including, unfortunately, those generated by scattering from flakes of multi-layer insulation (MLI) that has been shed by the spacecraft. We will describe a rich history of these MLI debris sightings, and we note that engineering considerations are required to minimize these deleterious effects in the future.

SaintCyr, Chris↗

NASA NTRS2010

Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 sq. km, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as possible sites for near-continuous sources of solar power.

E. Mazarico↗

NASA NTRS2015

Data-Driven Surface Traversability Analysis for Mars 2020 Landing Site Selection

The objective of this paper is three-fold: 1) to describe the engineering challenges in the surface mobility of the Mars 2020 Rover mission that are considered in the landing site selection processs, 2) to introduce new automated traversability analysis capabilities, and 3) to present the preliminary analysis results for top candidate landing sites. The analysis capabilities presented in this paper include automated terrain classification, automated rock detection, digital elevation model (DEM) generation, and multi-ROI (region of interest) route planning. These analysis capabilities enable to fully utilize the vast volume of high-resolution orbiter imagery, quantitatively evaluate surface mobility requirements for each candidate site, and reject subjectivity in the comparison between sites in terms of engineering considerations. The analysis results supported the discussion in the Second Landing Site Workshop held in August 2015, which resulted in selecting eight candidate sites that will be considered in the third workshop.

Ono, Masahiro↗

NASA NTRS2020

LunaNet: a Flexible and Extensible Lunar Exploration Communications and Navigation Infrastructure

NASA has set the ambitious goal of establishing a sustainable human presence on the Moon. Diverse commercial and international partners are engaged in this effort to catalyze scientific discovery, lunar resource utilization and economic development on both the Earth and at the Moon. Lunar development will serve as a critical proving ground for deeper exploration into the solar system. Space communications and navigation infrastructure will play an integral part in realizing this goal. This paper provides a high-level description of an extensible and scalable lunar communications and navigation architecture, known as LunaNet. LunaNet is a services network to enable lunar operations. Three LunaNet service types are defined: networking services, position, navigation and timing services, and science utilization services. The LunaNet architecture encompasses a wide variety of topology implementations, including surface and orbiting provider nodes. In this paper several systems engineering considerations within the service architecture are highlighted. Additionally, several alternative LunaNet instantiations are presented. Extensibility of the LunaNet architecture to the solar system internet is discussed.

Israel, David J.↗

NASA NTRS2020

LunaNet: A Flexible and Extensible Lunar Exploration Communication and Navigation Infrastructure

Israel, David J.↗