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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

A Statistical Study of Solar Particle Events in Flux and Dose

The high-energy protons from solar energetic particle (SEP) events present a hazard to space systems: damage to science instruments/electronics/materials or to astronauts. A reliable estimate of the high-energy proton environment is critical to assure mission success. Important characteristics of an SEP event are fluence, peak flux, energy spectrum, time to reach the peak flux, time to reach peak dose, and properties of the cumulative dose profile after an event starts. All of these characteristics are important to understand in order to design space missions properly for both robotic and human missions. Because of the unpredictable and sporadic nature of SEP events, statistical models are often used to represent the SEP parameters described above. In a study by Jun et al. (2007), the statistics of event fluences, durations, and time intervals between events were investigated using the then available historical SEP dataset obtained from the instruments onboard the IMP-8 spacecraft. Since then, a more comprehensive SEP dataset based off of IMP-8 and GOES called Reference Data Set Version 2.0 (RDSv2.0) has become available covering the SEP events up to Year 2015 under a framework of the European Space Agency's (ESA's) Solar Energetic Particle Environment Modelling (SEPEM) project (Jiggens et al., 2018). The main objectives of this statistical study of SEP events are two-fold: First, the statistics of peak fluxes, event fluences, durations, and time intervals will be re-visited by using RDSv2.0; Second, the statistical analyses of flux and dose timing will be performed using the same dataset RDSv2.0. The results of this study will address the statistical properties of all key parameters for designing a spacecraft or a human mission where the SEP environment is an important consideration.

Whitman, K.↗
NASA NTRS2007

NASA's RPS Design Reference Mission Set for Solar System Exploration

NASA's 2006 Solar System Exploration (SSE) Strategic Roadmap identified a set of proposed large Flagship, medium New Frontiers and small Discovery class missions, addressing key exploration objectives. These objectives respond to the recommendations by the National Research Council (NRC), reported in the SSE Decadal Survey. The SSE Roadmap is down-selected from an over-subscribed set of missions, called the SSE Design Reference Mission (DRM) set. Missions in the Flagship and New Frontiers classes can consider Radioisotope Power Systems (RPSs), while small Discovery class missions are not permitted to use them, due to cost constraints. In line with the SSE DRM set and the SSE Roadmap missions, the RPS DRM set represents a set of missions, which can be enabled or enhanced by RPS technologies. At present, NASA has proposed the development of two new types of RPSs. These are the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), with static power conversion; and the Stirling Radioisotope Generator (SRG), with dynamic conversion. Advanced RPSs, under consideration for possible development, aim to increase specific power levels. In effect, this would either increase electric power generation for the same amount of fuel, or reduce fuel requirements for the same power output, compared to the proposed MMRTG or SRG. Operating environments could also influence the design, such that an RPS on the proposed Titan Explorer would use smaller fins to minimize heat rejection in the extreme cold environment; while the Venus Mobile Explorer long-lived in-situ mission would require the development of a new RPS, in order to tolerate the extreme hot environment, and to simultaneously provide active cooling to the payload and other electric components. This paper discusses NASA's SSE RPS DRM set, in line with the SSE DRM set. It gives a qualitative assessment regarding the impact of various RPS technology and configuration options on potential mission architectures, which could support NASA's RPS technology development planning, and provide an understanding of fuel need trades over the next three decades.

solar system↗
NASA NTRS1956

An Engineering Approach to the Variable Fluid Property Problem in Free Convection

An analysis is made for the variable fluid property problem for laminar free convection on an isothermal vertical flat plate. For a number of specific cases, solutions of the boundary layer equations appropriate to the variable property situation were carried out for gases and liquid mercury. Utilizing these findings, a simple and accurate shorthand procedure is presented for calculating free convection heat transfer under variable property conditions. This calculation method is well established in the heat transfer field. It involves the use of results which have been derived for constant property fluids, and of a set of rules (called reference temperatures) for extending these constant property results to variable property situations. For gases, the constant property heat transfer results are generalized to the variable property situation by replacing beta (expansion coefficient) by one over T sub infinity and evaluating the other properties at T sub r equals T sub w minus zero point thirty-eight (T sub w minus T sub infinity). For liquid mercury, the generalization may be accomplished by evaluating all the properties (including beta) at this same T sub r. It is worthwhile noting that for these fluids, the film temperature (with beta equals one over T sub infinity for gases) appears to serve as an adequate reference temperature for most applications. Results are also presented for boundary layer thickness and velocity parameters.

Gregg, J. L.↗
NASA NTRS1988

An adaptive identification and control scheme for large space structures

A unified identification and control scheme capable of achieving space at form performance objectives under nominal or failure conditions is described. Preliminary results are also presented, showing that the methodology offers much promise for effective robust control of large space structures. The control method is a multivariable, adaptive, output predictive controller called Model Predictive Control (MPC). MPC uses a state space model and input reference trajectories of set or tracking points to adaptively generate optimum commands. For a fixed model, MPC processes commands with great efficiency, and is also highly robust. A key feature of MPC is its ability to control either nonminimum phase or open loop unstable systems. As an output controller, MPC does not explicitly require full state feedback, as do most multivariable (e.g., Linear Quadratic) methods. Its features are very useful in LSS operations, as they allow non-collocated actuators and sensors. The identification scheme is based on canonical variate analysis (CVA) of input and output data. The CVA technique is particularly suited for the measurement and identification of structural dynamic processes - that is, unsteady transient or dynamically interacting processes such as between aerodynamics and structural deformation - from short, noisy data. CVA is structured so that the identification can be done in real or near real time, using computationally stable algorithms. Modeling LSS dynamics in 1-g laboratories has always been a major impediment not only to understanding their behavior in orbit, but also to controlling it. In cases where the theoretical model is not confirmed, current methods provide few clues concerning additional dynamical relationships that are not included in the theoretical models. CVA needs no a priori model data, or structure; all statistically significant dynamical states are determined using natural, entropy-based methods. Heretofore, a major limitation in applying adaptive controllers to LSS problems has been the requirement for accurate models. We feel that MPC coupled with the CVA identification scheme will resolve this limitation. The results are based on research performed under an SBIR grant, administered by the Air Force Office of Scientific Research.

Carroll, J. V.↗
NASA NTRS2012

Generating Ground Reference Data for a Global Impervious Surface Survey

We are developing an approach for generating ground reference data in support of a project to produce a 30m impervious cover data set of the entire Earth for the years 2000 and 2010 based on the Landsat Global Land Survey (GLS) data set. Since sufficient ground reference data for training and validation is not available from ground surveys, we are developing an interactive tool, called HSegLearn, to facilitate the photo-interpretation of 1 to 2 m spatial resolution imagery data, which we will use to generate the needed ground reference data at 30m. Through the submission of selected region objects and positive or negative examples of impervious surfaces, HSegLearn enables an analyst to automatically select groups of spectrally similar objects from a hierarchical set of image segmentations produced by the HSeg image segmentation program at an appropriate level of segmentation detail, and label these region objects as either impervious or nonimpervious.

Image Processing↗
NASA NTRS1991

Development and application of virtual reality for man/systems integration

While the graphical presentation of computer models signified a quantum leap over presentations limited to text and numbers, it still has the problem of presenting an interface barrier between the human user and the computer model. The user must learn a command language in order to orient themselves in the model. For example, to move left from the current viewpoint of the model, they might be required to type 'LEFT' at a keyboard. This command is fairly intuitive, but if the viewpoint moves far enough that there are no visual cues overlapping with the first view, the user does not know if the viewpoint has moved inches, feet, or miles to the left, or perhaps remained in the same position, but rotated to the left. Until the user becomes quite familiar with the interface language of the computer model presentation, they will be proned to lossing their bearings frequently. Even a highly skilled user will occasionally get lost in the model. A new approach to presenting type type of information is to directly interpret the user's body motions as the input language for determining what view to present. When the user's head turns 45 degrees to the left, the viewpoint should be rotated 45 degrees to the left. Since the head moves through several intermediate angles between the original view and the final one, several intermediate views should be presented, providing the user with a sense of continuity between the original view and the final one. Since the primary way a human physically interacts with their environment should monitor the movements of the user's hands and alter objects in the virtual model in a way consistent with the way an actual object would move when manipulated using the same hand movements. Since this approach to the man-computer interface closely models the same type of interface that humans have with the physical world, this type of interface is often called virtual reality, and the model is referred to as a virtual world. The task of this summer fellowship was to set up a virtual reality system at MSFC and begin applying it to some of the questions which concern scientists and engineers involved in space flight. A brief discussion of this work is presented.

Brown, Marcus↗
NASA NTRS2016

Spacecraft Fire Safety Research at NASA Glenn Research Center

Appropriate design of fire detection systems requires knowledge of both the expected fire signature and the background aerosol levels. Terrestrial fire detection systems have been developed based on extensive study of terrestrial fires. Unfortunately there is no corresponding data set for spacecraft fires and consequently the fire detectors in current spacecraft were developed based upon terrestrial designs. In low gravity, buoyant flow is negligible which causes particles to concentrate at the smoke source, increasing their residence time, and increasing the transport time to smoke detectors. Microgravity fires have significantly different structure than those in 1-g which can change the formation history of the smoke particles. Finally the materials used in spacecraft are different from typical terrestrial environments where smoke properties have been evaluated. It is critically important to detect a fire in its early phase before a flame is established, given the fixed volume of air on any spacecraft. Consequently, the primary target for spacecraft fire detection is pyrolysis products rather than soot. Experimental investigations have been performed at three different NASA facilities which characterize smoke aerosols from overheating common spacecraft materials. The earliest effort consists of aerosol measurements in low gravity, called the Smoke Aerosol Measurement Experiment (SAME), and subsequent ground-based testing of SAME smoke in 55-gallon drums with an aerosol reference instrument. Another set of experiments were performed at NASAs Johnson Space Center White Sands Test Facility (WSTF), with additional fuels and an alternate smoke production method. Measurements of these smoke products include mass and number concentration, and a thermal precipitator was designed for this investigation to capture particles for microscopic analysis. The final experiments presented are from NASAs Gases and Aerosols from Smoldering Polymers (GASP) Laboratory, with selected results focusing on realistic fuel preparations and heating profiles with regards to early detection of smoke. SAFFIRE is the upcoming large-scale fire experiment which will be executed in a Cygnus vehicle after it undocks from the ISS.

Aerosol↗
NASA NTRS2004

A New Approach to Micro-arcsecond Astrometry with SIM Allowing Early Mission Narrow Angle Measurements of Compelling Astronomical Targets

The Space Interferometry Mission (SIM) is capable of detecting and measuring the mass of terrestrial planets around stars other than our own. It can measure the mass of black holes and the visual orbits of radio and x-ray binary sources. SIM makes possible a new level of understanding of complex astrophysical processes. SIM achieves its high precision in the so-called narrow-angle regime. This is defined by a 1 degree diameter field in which the position of a target star is measured with respect to a set of reference stars. The observation is performed in two parts: first, SIM observes a grid of stars that spans the full sky. After a few years, repeated observations of the grid allow one to determine the orientation of the interferometer baseline. Second, throughout the mission, SIM periodically observes in the narrow-angle mode. Every narrow-angle observation is linked to the grid to determine the precise attitude and length of the baseline. The narrow angle process demands patience. It is not until five years after launch that SIM achieves its ultimate accuracy of 1 microarcsecond. The accuracy is degraded by a factor of approx. 2 at mid-mission. Our work proposes a technique for narrow angle astrometry that does not rely on the measurement of grid stars. This technique, called Gridless Narrow Angle Astrometry (GNAA) can obtain microarcsecond accuracy and can detect extra-solar planets and other exciting objects with a few days of observation. It can be applied as early as during the first six months of in-orbit calibration (IOC). The motivations for doing this are strong. First, and obviously, it is an insurance policy against a catastrophic mid-mission failure. Second, at the start of the mission, with several space-based interferometers in the planning or implementation phase, NASA will be eager to capture the public's imagination with interferometric science. Third, early results and a technique that can duplicate those results throughout the mission will give the analysts important experience in the proper use and calibration of SIM.

Shaklan, Stuart↗
NASA NTRS1986

Interactive algebraic grid-generation technique

An algebraic grid generation technique and use of an associated interactive computer program are described. The technique, called the two boundary technique, is based on Hermite cubic interpolation between two fixed, nonintersecting boundaries. The boundaries are referred to as the bottom and top, and they are defined by two ordered sets of points. Left and right side boundaries which intersect the bottom and top boundaries may also be specified by two ordered sets of points. when side boundaries are specified, linear blending functions are used to conform interior interpolation to the side boundaries. Spacing between physical grid coordinates is determined as a function of boundary data and uniformly space computational coordinates. Control functions relating computational coordinates to parametric intermediate variables that affect the distance between grid points are embedded in the interpolation formulas. A versatile control function technique with smooth-cubic-spline functions is presented. The technique works best in an interactive graphics environment where computational displays and user responses are quickly exchanged. An interactive computer program based on the technique and called TBGG (two boundary grid generation) is also described.

Smith, R. E.↗
NASA NTRS1987

Computation of diffuse sky irradiance from multidirectional radiance measurements

Accurate determination of the diffuse solar spectral irradiance directly above the land surface is important in characterizing the reflectance properties of these surfaces, especially vegetation canopies. This determination is also needed to infer the net radiation budget of the earth-atmosphere system above these surfaces. An algorithm is developed here for the computation of hemispheric diffuse irradiance using the measurements from an instrument called PARABOLA, which rapidly measures upwelling and downwelling radiances in three selected wavelength bands. The validity of the algorithm is established from simulations. The standard reference data set of diffuse radiances of Dave (1978), obtained by solving the radiative transfer equation numerically for realistic atmospheric models, is used to simulate PARABOLA radiances. Hemispheric diffuse irradiance is estimated from a subset of simulated radiances by using the algorithm described. The algorithm is validated by comparing the estimated diffuse irradiance with the true diffuse irradiance of the standard data set. The validations include sensitivity studies for two wavelength bands (visible, 0.65-0.67 micron; near infrared, 0.81-0.84 micron), different atmospheric conditions, solar elevations, and surface reflectances. In most cases the hemispheric diffuse irradiance computed from simulated PARABOLA radiances and the true irradiance obtained from radiative transfer calculations agree within 1-2 percent. This technique can be applied to other sampling instruments designed to estimate hemispheric diffuse sky irradiance.

Ahmad, Suraiya P.↗
NASA NTRS1998

Incorporating the APS Catalog of the POSS I and Image Archive in ADS

The primary purpose of this contract was to develop the software to both create and access an on-line database of images from digital scans of the Palomar Sky Survey. This required modifying our DBMS (called Star Base) to create an image database from the actual raw pixel data from the scans. The digitized images are processed into a set of coordinate-reference index and pixel files that are stored in run-length files, thus achieving an efficient lossless compression. For efficiency and ease of referencing, each digitized POSS I plate is then divided into 900 subplates. Our custom DBMS maps each query into the corresponding POSS plate(s) and subplate(s). All images from the appropriate subplates are retrieved from disk with byte-offsets taken from the index files. These are assembled on-the-fly into a GIF image file for browser display, and a FITS format image file for retrieval. The FITS images have a pixel size of 0.33 arcseconds. The FITS header contains astrometric and photometric information. This method keeps the disk requirements manageable while allowing for future improvements. When complete, the APS Image Database will contain over 130 Gb of data. A set of web pages query forms are available on-line, as well as an on-line tutorial and documentation. The database is distributed to the Internet by a high-speed SGI server and a high-bandwidth disk system. URL is http://aps.umn.edu/IDB/. The image database software is written in perl and C and has been compiled on SGI computers with MIX5.3. A copy of the written documentation is included and the software is on the accompanying exabyte tape.

Humphreys, Roberta M.↗
NASA NTRS2001

Optimizing Orbit-Instrument Configuration for Global Precipitation Mission (GPM) Satellite Fleet

Following the scientific success of the Tropical Rainfall Measuring Mission (TRMM) spearheaded by a group of NASA and NASDA scientists, their external scientific collaborators, and additional investigators within the European Union's TRMM Research Program (EUROTRMM), there has been substantial progress towards the development of a new internationally organized, global scale, and satellite-based precipitation measuring mission. The highlights of this newly developing mission are a greatly expanded scope of measuring capability and a more diversified set of science objectives. The mission is called the Global Precipitation Mission (GPM). Notionally, GPM will be a constellation-type mission involving a fleet of nine satellites. In this fleet, one member is referred to as the "core" spacecraft flown in an approximately 70 degree inclined non-sun-synchronous orbit, somewhat similar to TRMM in that it carries both a multi-channel polarized passive microwave radiometer (PMW) and a radar system, but in this case it will be a dual frequency Ku-Ka band radar system enabling explicit measurements of microphysical DSD properties. The remainder of fleet members are eight orbit-synchronized, sun-synchronous "constellation" spacecraft each carrying some type of multi-channel PMW radiometer, enabling no worse than 3-hour diurnal sampling over the entire globe. In this configuration the "core" spacecraft serves as a high quality reference platform for training and calibrating the PMW rain retrieval algorithms used with the "constellation" radiometers. Within NASA, GPM has advanced to the pre-formulation phase which has enabled the initiation of a set of science and technology studies which will help lead to the final mission design some time in the 2003 period. This presentation first provides an overview of the notional GPM program and mission design, including its organizational and programmatic concepts, scientific agenda, expected instrument package, and basic flight architecture. Following this introduction, we focus specifically on the last topic, that being an analysis which leads to an optimal flight architecture dictated in part by science requirements but constrained by allowable orbital mechanics, instrument scan patterns, and antenna aperture properties. Because the optimal architecture involves an interplay between orbit mechanics and instrument specifications, it is important to recognize that in attempting to serve various scientific themes, the final optimal architecture will represent a compromise concerning dynamic range, spatial resolution, sampling interval, pointing, beam coincidence, and measurement uncertainty. Moreover, cost becomes a major factor in seeking the optimal architecture through the pathways of antenna and instrument scan designs, as well as propulsion requirements associated with the orbit heights of various "constellation" members. Although the results presented at the IGARSS-2001 meeting will likely not be the fully refined flight architecture specifications, they are expected to be nearly complete.

Smith, Eric A.↗
NASA NTRS2004

Developing Advanced Support Technologies for Planetary Exploration Missions

The United States Vision for Space Exploration calls for sending robots and humans to explore the Earth s moon, the planet Mars, and beyond. The National Aeronautics and Space Administration (NASA) is developing a set of design reference missions that will provide further detail to these plans. Lunar missions are expected to provide a stepping stone, through operational research and evaluation, in developing the knowledge base necessary to send crews on long duration missions to Mars and other distant destinations. The NASA Exploration Systems Directorate (ExSD), in its program of bioastronautics research, manages the development of technologies that maintain human life, health, and performance in space. Using a systems engineering process and risk management methods, ExSD s Human Support Systems (HSS) Program selects and performs research and technology development in several critical areas and transfers the results of its efforts to NASA exploration mission/systems development programs in the form of developed technologies and new knowledge about the capabilities and constraints of systems required to support human existence beyond Low Earth Orbit. HSS efforts include the areas of advanced environmental monitoring and control, extravehicular activity, food technologies, life support systems, space human factors engineering, and systems integration of all these elements. The HSS Program provides a structured set of deliverable products to meet the needs of exploration programs. these products reduce the gaps that exist in our knowledge of and capabilities for human support for long duration, remote space missions. They also reduce the performance gap between the efficiency of current space systems and the greater efficiency that must be achieved to make human planetary exploration missions economically and logistically feasible. In conducting this research and technology development program, it is necessary for HSS technologists and program managers to develop a common currency for decision making and the allocation of funding. A high level assessment is made of both the knowledge gaps and the system performance gaps across the program s technical project portfolio. This allows decision making that assures proper emphasis areas and provides a key measure of annual technological progress, as exploration mission plans continue to mature.

Berdich, Debra P.↗
NASA NTRS2004

Developing Advanced Human Support Technologies for Planetary Exploration Missions

The United States Vision for Space Exploration calls for sending robots and humans to explore the Earth's moon, the planet Mars, and beyond. The National Aeronautics and Space Administration (NASA) is developing a set of design reference missions that will provide further detail to these plans. Lunar missions are expected to provide a stepping stone, through operational research and evaluation, in developing the knowledge base necessary to send crews on long duration missions to Mars and other distant destinations. The NASA Exploration Systems Directorate (ExSD), in its program of bioastronautics research, manages the development of technologies that maintain human life, health, and performance in space. Using a system engineering process and risk management methods, ExSD's Human Support Systems (HSS) Program selects and performs research and technology development in several critical areas and transfers the results of its efforts to NASA exploration mission/systems development programs in the form of developed technologies and new knowledge about the capabilities and constraints of systems required to support human existence beyond Low Earth Orbit. HSS efforts include the areas of advanced environmental monitoring and control, extravehicular activity, food technologies, life support systems, space human factors engineering, and systems integration of all these elements. The HSS Program provides a structured set of deliverable products to meet the needs of exploration programs. These products reduce the gaps that exist in our knowledge of and capabilities for human support for long duration, remote space missions. They also reduce the performance gap between the efficiency of current space systems and the greater efficiency that must be achieved to make human planetary exploration missions economically and logistically feasible. In conducting this research and technology development program, it is necessary for HSS technologists and program managers to develop a common currency for decision making and the allocation of funding. A high level assessment is made of both the knowledge gaps and the system performance gaps across the program s technical project portfolio. This allows decision making that assures proper emphasis areas and provides a key measure of annual technological progress, as exploration mission plans continue to mature.

Berdich, Debra P.↗
NASA NTRS2016

Promoting A-Priori Interoperability of HLA-Based Simulations in the Space Domain: The SISO Space Reference FOM Initiative

Distributed and Real-Time Simulation plays a key-role in the Space domain being exploited for missions and systems analysis and engineering as well as for crew training and operational support. One of the most popular standards is the 1516-2010 IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA). HLA supports the implementation of distributed simulations (called Federations) in which a set of simulation entities (called Federates) can interact using a Run-Time Infrastructure (RTI). In a given Federation, a Federate can publish and/or subscribes objects and interactions on the RTI only in accordance with their structures as defined in a FOM (Federation Object Model). Currently, the Space domain is characterized by a set of incompatible FOMs that, although meet the specific needs of different organizations and projects, increases the long-term cost for interoperability. In this context, the availability of a reference FOM for the Space domain will enable the development of interoperable HLA-based simulators for related joint projects and collaborations among worldwide organizations involved in the Space domain (e.g. NASA, ESA, Roscosmos, and JAXA). The paper presents a first set of results achieved by a SISO standardization effort that aims at providing a Space Reference FOM for international collaboration on Space systems simulations.

Moller, Bjorn↗
NASA NTRS2017

Answering the Call for Model-Relevant Observations of Aerosols and Clouds

We describe a technique for combining multiple A-Train aerosol data sets, namely MODIS spectral AOD (aerosol optical depth), OMI AAOD (absorption aerosol optical depth) and CALIOP aerosol backscatter retrievals (hereafter referred to as MOC retrievals) to estimate full spectral sets of aerosol radiative properties, and ultimately to calculate the 3-D distribution of direct aerosol radiative effects (DARE). We present MOC results using almost two years of data collected in 2007 and 2008, and show comparisons of the aerosol radiative property estimates to collocated AERONET retrievals. We compare the spatio-temporal distribution of the MOC retrievals and MOC-based calculations of seasonal clear-sky DARE to values derived from four models that participated in the Phase II AeroCom model intercomparison initiative. Comparisons of seasonal aerosol property to AeroCom Phase II results show generally good agreement best agreement with forcing results at TOA is found with GMI-MerraV3.We discuss the challenges in making observations that really address deficiencies in models, with some of the more relevant aspects being representativeness of the observations for climatological states, and whether a given model-measurement difference addresses a sampling or a model error.

Redemann, J.↗
NASA NTRSDate not supplied

A Lunar Water ISRU System Study for Human-Scale Propellant Production

NASA’s plans to return to the moon in the Artemis campaign include intentions for sustainable surface operations. In-Situ Resource Utilization (ISRU) is key to enabling sustainability. The use of water, which has been identified in the lunar polar regions [1-4], could be pivotal to a sustainable architecture. While water has been identified, there is limited information regarding its form and distribution. The Lunar Water ISRU Measurement Study (LWIMS) [5] outlined the current state of knowledge regarding water resources on the moon, what information is lacking, and how to approach a measurement campaign to close those knowledge gaps. However the NASA timeline necessitates that lunar surface water prospecting, or reconnaissance, efforts and ISRU system design to occur in parallel. ISRU hardware and systems development must proceed without key resource knowledge. Yet, engineering design requires come constraints and targets to work to. The goal of this study was to define a set of lunar water reference cases, based on the cur-rent lunar water information, to help focus ISRU de-sign and planning. This approach is similar to an study focused on Mars resources called Mars Water ISRU Planning (MWIP) [6].

Lunar Water↗
NASA NTRS2019

CHANGO: A Software Tool for Boost Stage Guidance of the Space Launch System Exploration Mission 1

The Day of Launch Initiation Load Update (DOLILU) System is the means by which the Space Launch System (SLS) Vehicle trajectory is designed, verified, and uploaded on the Day of Launch (DOL) in order to ensure a safe flight. Launch vehicles are designed to fly down a narrow angle of attack and sideslip angle corridor in order to keep them within structural load limits. The angle of attack and sideslip angle response to the launch vehicle experiences can vary significantly based upon the winds experienced on the DOL. SLS Boost Stage flight employs an open-loop guidance scheme through Solid Rocket Booster (SRB) separation. In the SLS open-loop scheme, the vehicle will fly a prescribed set of attitudes as a function of the change in altitude since launch. This set of reference attitude values and corresponding altitude reference independent values are designed with ground software using winds measured on the DOL with the goal of minimizing angle of attack and sideslip angle, thereby minimizing related ascent integrated vehicle structural loads. The table of Boost Stage attitude commands as a function of altitude gained since launch is called the chi table. A software tool called CHANGO (Chi Angle Optimizer) designs the Boost Stage chi table which is uploaded to the vehicle’s flight computer and used during ascent by the flight software (FSW). The wind and atmospheric conditions are measured prior to launch and pre-processed to become input to the CHANGO software along with a set of parameters developed in advance of the DOL. CHANGO’s target set consists of the heading and altitude rate at SRB separation determined well before launch by the Program to Optimize Simulated Trajectories (POST). CHANGO consists of a simplified three degree-of-freedom (3-DOF) simulation representing the SLS launch configuration. In general, the launch azimuth is strongly correlated with the heading at SRB separation, and the initial pitchover rate is strongly correlated with the altitude rate at SRB separation. CHANGO uses an adaptation of Powell’s method to vary the initial pitchover rate and launch azimuth to solve a 2-dimentional minimization problem. CHANGO’s trajectory simulation is phase-based, with flight events separating the phases. Each flight phase has different attitude alignment logic. CHANGO’s 3-DOF simulation starts when the vehicle’s thrust-to-weight ratio equals one, and ends at a pre-calculated SRB separation time.

Ahmad, Naeem↗