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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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A computer simulation program to model the redistribution of particulate contaminants on a spacecraft after launch was developed. The component models for particulate adhesion, meteoroid impact, and electrostatic forces are described and intermediate results are presented. The results of a sample calculation show that the recontamination process is important.
The capture and berthing of a controlled spacecraft using a robotic manipulator is an important technology for future space missions and is presently being considered as a backup option for direct docking of the Space Shuttle to the Space Station during assembly missions. The dynamics and control of spacecraft configurations that are manipulator-coupled with each spacecraft having independent attitude control systems is not well understood and NASA is actively involved in both analytic research on this three dimensional control problem for manipulator coupled active spacecraft and experimental research using a two dimensional ground based facility at the Marshall Space Flight Center (MSFC). This paper first describes the MSFC testbed and then describes a two link arm simulator that has been developed to facilitate control theory development and test planning. The motion of the arms and the payload is controlled by motors located at the shoulder, elbow, and wrist.
A flow simulation for charged and neutral particles around spacecraft is given that combines the fully coupled effects of neutral particle flow, plasma flow, electromagnetic field effects, and spacecraft charging. The simulation allows for chemically reacting flows (associative ionization, dissociation, and chain exchange) and for thermal accommodation at a spacecraft surface. The solution procedure was applied to several types of flows with orbital altitudes ranging from 250 km to 500 km. Excellent agreement with previously verified computational algorithms was obtained for both the neutral and charged particle cases. Results for the full flow simulation are presented for altitudes of 250 km and 500 km.
Television-type, out-window visual simulation image generator design and specifications for aircraft or spacecraft manned flight simulation
The overall objective of the experiment was to evaluate the effect of the space environment on components considered for a Space-Based Radar (SBR) Phased-Array Antenna. Of primary interest was a study of the degradation of the polyimide film Kapton (DuPont trademark), the material considered for use in the antenna plane. The most striking result of the experiment was the overall good condition of the Kapton antenna planes and Kapton tensile specimens, despite nearly six years of exposure to the space environment. This was largely attributable to the orientation of the Kapton (parallel and flush on the space end) and the stability of the Long Duration Exposure Facility (LDEF) in orbit. However, weathering of exposed Kapton surfaces was not insignificant. Results on elongation and mechanical properties of the plain and the fiberglass-reinforced Kapton are presented. Reduction in strain to failure of flight-exposed Kapton is attributed to surface defects of these specimens. Physical property testing of the materials to date reveals no significant difference between flight-exposed and control material. The second objective was to investigate the interaction between high-voltage electrodes and typical spacecraft contaminants in simulation of discharge triggering across differentially charged dielectric surfaces (spacecraft charging conditions). Electronic data acquisition and memory systems appeared to operate correctly, but very few discharges were recorded. Induced radioactivity, contamination, impacts, and orientation features of atomic oxygen erosion were observed.
Environmental test facilities are not suitable in any case to comply with special or complex test requirements without modifications. Dedicated upgrades of the test facility and their subsystems with respect to the test requirements and specifications are often necessary. The Flight Model of the Planck Space Telescope was tested in the Large Space Simulator (LSS) of the ESTEC Test Centre. Main goals of the test were the verification of the deformation of the Telescope during thermal vacuum conditions at different temperature levels and the validation of the Thermal Model. The deformations of the telescope have been traced by two Videogrammetry canisters. In order to provide different view positions with respect to the PLANCK Telescope it was necessary to rotate the specimen by +/- 180deg. In addition very stringent requirements for the low temperature level of the thermal environment has lead to a comprehensive test set-up which was divided in four main elements: Dedicated support structure for the Videogrammetry canisters providing several DoF for adjustment. Structure to support three Infrared panels around the specimen. MLI curtain to cover the LSS 8m auxiliary chamber opening. System providing LN2 supply for the rotating PLANCK telescope cold panel. The design, manufacturing and integration of the necessary mechanical ground support to install for instance the canisters and to ensure the 180 rotation of the telescope under cold and high vacuum conditions was an extensive and important part of the entire test program. This paper will concentrate on the design issues, the implementation and verification of the MGSE provided for the Planck Space Telescope FM Videogrammetry Test in the LSS and the troubleshooting caused by a failure during the first rotation under cold conditions.
The spacecraft system that plays the greatest role throughout the program lifecycle is the Command and Data Handling System (C&DH), along with the associated algorithms and software. The C&DH takes on this role as cost driver because it is the brains of the spacecraft and is the element of the system that is primarily responsible for the integration and interoperability of all spacecraft subsystems. During design and development, many activities associated with mission design, system engineering, and subsystem development result in products that are directly supported by the C&DH, such as interfaces, algorithms, flight software (FSW), and parameter sets. A modular system architecture has been developed that provides a means for rapid spacecraft assembly, test, and integration. This modular C&DH software architecture, which can be targeted and adapted to a wide variety of spacecraft architectures, payloads, and mission requirements, eliminates the current practice of rewriting the spacecraft software and test environment for every mission. This software allows missionspecific software and algorithms to be rapidly integrated and tested, significantly decreasing time involved in the software development cycle. Additionally, the FSW includes an Onboard Dynamic Simulation System (ODySSy) that allows the C&DH software to support rapid integration and test. With this solution, the C&DH software capabilities will encompass all phases of the spacecraft lifecycle. ODySSy is an on-board simulation capability built directly into the FSW that provides dynamic built-in test capabilities as soon as the FSW image is loaded onto the processor. It includes a six-degrees- of-freedom, high-fidelity simulation that allows complete closed-loop and hardware-in-the-loop testing of a spacecraft in a ground processing environment without any additional external stimuli. ODySSy can intercept and modify sensor inputs using mathematical sensor models, and can intercept and respond to actuator commands. ODySSy integration is unique in that it allows testing of actual mission sequences on the flight vehicle while the spacecraft is in various stages of assembly, test, and launch operations all without any external support equipment or simulators. The ODySSy component of the FSW significantly decreases the time required for integration and test by providing an automated, standardized, and modular approach to integrated avionics and component interface and functional verification. ODySSy further provides the capability for on-orbit support in the form of autonomous mission planning and fault protection.
In this paper, we describe a simulation testbed under development for measuring MOC's performance in a high-fidelity entry, descent, and landing environment, and provide our preliminary simulation result.
Two effects of noncollimation of solar light beams in spacecraft thermal testing simulation chamber
Three methods of numerically simulating the motion of a spacecraft with a magnetic damper are compared. Simulations of motion of the initial assembly stage of Space Station Freedom show that results obtained with the first approach are in general agreement with those based on the second approach, while results from the third method are incorrect unless the spacecraft is nearly at rest in a local-vertical-local-horizontal reference frame. Simulations based on the second method proceed much more quickly than simulations based on the first. An integral of equations of motion governing the behavior of a spacecraft, and a sphere, which is part of the damper is presented. The integral can be used to test the results of numerical integrations performed in connection with the first and second approaches.
Half-scale thermal model of Mariner IV SPACECRAFT tested in simulated solar environment
Universal Simulation Executive (USE) program accelerates and eases generation of application programs for numerical simulation of continuous trajectories interrupted by or containing discrete events. Developed for simulation of multiple spacecraft trajectories with events as one spacecraft crossing the equator, two spacecraft meeting or parting, or firing rocket engine. USE also simulates operation of chemical batch processing factory. Written in Ada.
NASA’s planned Europa Clipper mission seeks to assess the habitability of Jupiter’s moon Europa, which exhibits strong evidence of an ocean of liquid water underneath its icy crust. The sheer number of unique instruments, all of which require quiescent environments in order to operate, compounded with Jupiter’s distance from the Sun and Earth, make this planned mission challenging and resource-constrained. High fidelity, mission-level simulations that model the spacecraft, ground, and environment from launch to end-of-mission with a given trajectory and mission plan have been employed early in the project lifecycle to better understand the interactions between various components of the mission and how design changes impact the entire system. These simulations have already resulted in tangible benefits to the project by providing vital input to key spacecraft trades, assessing impacts to operability, and quantifying how well the scientific objectives of the mission can be achieved. Improvements to simulation performance and to the process by which information defining the system is gathered and built into models used by simulations have the potential to further expand the scope of their use on Europa Clipper and future missions.
The question: Which set of modes furnishes a higher fidelity math model of dynamics of a multibody, deformable spacecraft (hinges-free or hinges-locked vehicle modes) is answered. Two sets of general, discretized, linear equations of motion of a spacecraft with an arbitrary number of deformable appendages, each articulated directly to the core body, are obtained using the above two families of modes. By a comparison of these equations, ten sets of modal identities are constructed which involve modal momenta coefficients and frequencies associated with both classes of modes. The sums of infinite series that appear in the identities are obtained in terms of mass, and first and second moments of inertia of the appendages, core body, and vehicle by using certain basic identities concerning appendage modes. Applying the above identities to a four-body spacecraft, the hinges-locked vehicle modes are found to yield a higher fidelity model than hinges-free modes, because the latter modes have nonconverging modal coefficients; a characteristic proved and illustrated.
Solar beam divergence effects on thermal characteristics of spacecraft tested in solar simulator
The work presented is motivated by the need for a national satellite rescue policy, not the ad hoc policy now in place. In studying different approaches for a national policy, the issue of capture and stabilization of a tumbling spacecraft must be addressed. For a rescue mission involving a tumbling spacecraft, it may be advantageous to have a rescue vehicle which is compact and 'rigid' during the rendezvous/capture phase. After capture, passive stabilization techniques could be utilized as an efficient means of detumbling the resulting system (i.e., both the rescue vehicle and captures spacecraft). Since the rescue vehicle is initially compact and 'rigid,' significant passive stabilization through energy dissipation can only be achieved through the deployment of flexible appendages. Once stabilization is accomplished, retraction of the appendages before maneuvering the system to its final destination may also prove advantageous. It is therefore of paramount interest that we study the effect of appendage deployment/retraction on the attitude stability of a spacecraft. Particular interest should be paid to appendage retraction, since if this process is destabilizing, passive stabilization as proposed may not be useful. Over the past three decades, it has been an 'on-again-off-again affair' with the problem of spacecraft appendage deployment. In most instances, these studies have been numerical simulations of specific spacecraft configurations for which there were specific concerns. The primary focus of these studies was the behavior of the appendage during deployment; the effects of appendage retraction was considered only in one of these studies. What is missing in the literature is a thorough study of the effects of appendage deployment/retraction on the attitude stability of a spacecraft. This paper presents a rigorous analysis of the stability of a spinning spacecraft during the deployment or the retraction of an appendage. The analysis is simplified such that meaningful insights into the problem can be inferred; it is not overly simplified such that critical dynamical behavior is neglected. The system is analyzed assuming that the spacecraft hub is rigid. The appendage deployment mechanism is modeled as a point mass on a massless rod whose length undergoes prescribed changes. Simplified flexibility effects of the appendage are included. The system is examined for stability by linearizing the equations in terms of small deviations from steady, noninterfering coning motion. Routh's procedure for analyzing small deviations from steady motion in dynamical systems is utilized in the analysis. The system of equations are nondimensionalized to facilitate parametric studies. The results are presented in terms of a reduced number of nondimensional parameters so that some general conclusions may be drawn. Verification of the linear analysis is presented through numerical simulations of the complete nonlinear, nonautonomous, coupled equations.
Propellant management in spacecraft propulsion systems is complex. In many current and future crewed and robotic spacecraft propulsion systems, a number of unintended or unavoidable scenarios can occasionally lead to liquid “slugs” of propellant accumulating in unwanted locations and thereafter being rapidly accelerated through complex and arbitrary tubing networks otherwise filled with vapor or gas. To develop better understanding of the multiphase fluid dynamics associated with these “slug launch” scenarios, NASA Marshal Space Flight Center’s (MSFC) ER42 branch – the propulsion fluid dynamics research branch – conducted 3D multiphase transient Volume of Fluid (VOF) CFD simulations using an in-house tool called LOCI-Stream VOF on semi-canonical tube networks with straight sections, bends, and bend complexes. In addition, high-speed flow visualization validation experiments using propellants were conducted on similar tube network geometries at the NASA White Sands Test Facility (WSTF). These simulations and flow-visualization experiments found these scenarios lead to a variety of unique multiphase fluid dynamic effects involving the leading and trailing edges of the slug in both straight sections and curved bends as well as the progressive erosion, acceleration, and eventual “punch-through” of the driving gas through the liquid slug. Understanding these multiphase fluid dynamic effects has led to unique and often counter-intuitive observations which have been of critical relevance to important engineering concerns associated with these “slug launch” scenarios.