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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Design of Neural Networks for Fast Convergence and Accuracy

A novel procedure for the design and training of artificial neural networks, used for rapid and efficient controls and dynamics design and analysis for flexible space systems, has been developed. Artificial neural networks are employed to provide a means of evaluating the impact of design changes rapidly. Specifically, two-layer feedforward neural networks are designed to approximate the functional relationship between the component spacecraft design changes and measures of its performance. A training algorithm, based on statistical sampling theory, is presented, which guarantees that the trained networks provide a designer-specified degree of accuracy in mapping the functional relationship. Within each iteration of this statistical-based algorithm, a sequential design algorithm is used for the design and training of the feedforward network to provide rapid convergence to the network goals. Here, at each sequence a new network is trained to minimize the error of previous network. The design algorithm attempts to avoid the local minima phenomenon that hampers the traditional network training. A numerical example is performed on a spacecraft application in order to demonstrate the feasibility of the proposed approach.

Maghami, Peiman G.↗
NASA NTRS2005

NASA Langley Trajectory Simulation Capabilities for Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter will launch in August 2005 and will achieve Mars Orbit Insertion in March of 2006. It will then take approximately six months to use the process of aerobraking to shape its orbit into the desired science mapping orbit. This six-month period is arguably the phase of the Mars Reconnaissance Orbiter mission with the highest risk to the spacecraft, dipping to within 100 km of the planet. This process requires enough atmospheric drag to slow the spacecraft and circularize the orbit while remaining high enough in the Mars atmosphere as to not risk thermal degradation of spacecraft components. This paper will discuss the trajectory simulation and several analyses performed at NASA Langley Research Center to support a successful aerobraking phase of the Mars Reconnaissance Orbiter mission.

Prince, Jill L. Hanna↗
NASA NTRS2005

Genesis Preliminary Examination: Ellipsometry Overview

The Genesis spacecraft returned to Earth on September 8, 2004, experiencing a non-nominal reentry in which both the drogue and main parachutes failed to deploy causing the capsule to impact the surface of the UTTR desert at a speed of approximately 310 kph (193 mph). The impact caused severe damage to the capsule and a breach of the science canister in the field. The science canister was recovered and transported to the cleanroom at UTTR within approximately 8 hours of reentry. Although the ground water table did not rise to canister level before removal, damp soil and debris from the heat shield and other spacecraft components did enter the canister and contaminate some collector surfaces. The objective of preliminary examination of the Genesis collectors is to provide the science community with the information necessary to request the most useful samples for their analysis.

Stansbery, E. K.↗
NASA NTRS2005

The Role of Space Experiments in the Radiation Qualification of Electronic and Photonic Devices and Systems

Space experiments are occasionally launched to study the effects of radiation on electronic and photonic devices. This begs the following questions: Are space experiments necessary? Do the costs justify the benefits? How does one judge success of space experiment? What have we learned from past space experiments? How does one design a space experiment? This viewgraph presentation provides information on the usefulness of space and ground tests for simulating radiation damage to spacecraft components.

Buchner, S.↗
NASA NTRS2004

23rd Space Simulation Conference Proceedings

The proceedings of this conference address space environment simulation for full-scale ground tests of spacecraft, as well as testing of spacecraft components and instruments. Some of the testing and simulation techniques addressed in the conference papers include: thermal vacuum tests, cryogenic tests, thermal cycling tests, structural dynamics tests, vibration tests, magnetic tests, weightlessness simulation, solar simulation, and Mars environment simulation. The papers also address space environment test facilities, including their control systems.

Source record↗
NASA NTRS2005

Releasable Locking Mechanisms

In the aerospace field spacecraft components are held together by separation systems until a specific time when they must be separated or deployed. Customarily a threaded joining bolt engages one of the components to be joined, and a threaded nut is placed on that bolt against the other component so they can be drawn together by a releasable locking assembly. The releasable locking assembly herein includes a plunger having one end coupled to one end of a plunger bolt. The other end is flanged to abut and compress a coil spring when the plunger is advanced toward the interface plane between the two components. When the plunger is so advanced toward the interface plane, the end of the plunger bolt can be connected to the joining bolt. Thus during retraction the joining bolt is drawn to one side of the interface plane by the force of the expanding spring.

Rafiq Ahmed↗
NASA NTRS2006

Fabrication and Evaluation of Titanium and Zirconium based Wires for use during Extended, Deep Space, Missions

Novel materials and designs are necessary for transport vessels and propulsion systems to fulfill NASA's vision of easier access to space and the expansion of human exploration beyond low-earth orbit. Spacecraft components must necessarily be lighter and stronger than their predecessors and will likely be required to serve new purposes. Furthermore, they must be resilient to the thermal, vacuum, and radiation environment of space for extended periods of time and may need to perform in the near proximity of a nuclear fuel source. To this end research has been initiated to fabricate novel, composite, wires based on titanium and zirconium pearlitic alloys. It is expected that the fabricated wire will well endure in the space environment with application as tethers, sail components, fasteners, and a myriad of other (including earth-based) uses. A background on pearlitic wire, novel alloy development, microstructural characterization, and initial mechanical testing results will be presented and discussed.

Grugel, Richard N.↗
NASA NTRS1995

Vibration damping of the Cassini spacecraft structure

Cassini is a large robotic spacecraft currently under development at the Jet Propulsion Laboratory (JPL) whose interplanetary scientific mission is to explore Saturn, its ring, and its moons. Cassini is scheduled to launch on a Titan IV rocket with a Centaur upper stage booster, and will be protected during ascent through the atmosphere by a lightweight aluminum payload fairing (PLF). As a result of the extreme noise levels generated by the powerful Titan IV at liftoff, and the acoustic transparency of the PLF, Cassini is predicted to experience sever acoustic levels. Furthermore, the high acoustic levels, coupled with the size and configuration of the spacecraft, will induce unacceptable random vibration levels on the structure and critical spacecraft components. Studies showed that the use of Tuned Vibration Absorbers (TVAs) would be effective in reducing vibration. A series of reverberant acoustic tests were performed on a partial development test model (DTM) of Cassini to evaluate the effectiveness of TVAs in reducing the structural vibration. The test results showed that significant vibration attenuation was achieved.

vibration damping↗
NASA NTRS2005

A Genesis breakup and burnup analysis in off-nominal Earth return and atmospheric entry

The Genesis project conducted a detailed breakup/burnup analysis before the Earth return to determine if any spacecraft component could survive and reach the ground intact in case of an off-nominal entry. In addition, an independent JPL team was chartered with the responsibility of analyzing several definitive breakup scenarios to verify the official project analysis. This paper presents the analysis and results of this independent team.

off-nominal entry↗
NASA NTRS2006

Stardust Sample: Investigator's Guidebook

In January 2006, the Stardust spacecraft returned the first in situ collection of samples from a comet, and the first samples of contemporary interstellar dust. Stardust is the first US sample return mission from a planetary body since Apollo, and the first ever from beyond the moon. This handbook is a basic reference source for allocation procedures and policies for Stardust samples. These samples consist of particles and particle residues in aerogel collectors, in aluminum foil, and in spacecraft components. Contamination control samples and unflown collection media are also available for allocation.

Allen, Carl↗
NASA NTRS1978

Wall Covering

The attractive wall covering shown below is one of 132 styles in the Mirror Magic II line offered by The General Tire & Rubber Company, Akron, Ohio. The material is metallized plastic fabric, a spinoff from space programs. Wall coverings are one of many consumer applications of aluminized plastic film technology developed for NASA by a firm later bought by King-Seeley Thermos Company, Winchester, Massachusetts, which now produces the material. The original NASA use was in the Echo 1 passive communications satellite, a "space baloon" made of aluminized mylar; the high reflectivity of the metallized coating enabled relay of communications signals from one Earth station to another by "bouncing" them off the satellite. The reflectivity feature also made the material an extremely efficient insulator and it was subsequently widely used in the Apollo program for such purposes as temperature control of spacecraft components and insulation of tanks for fuels that must be maintained at very low temperatures. I Used as a wall covering, the aluminized material offers extra insulation, reflects light and I resists cracking. In addition to General Tire, King-Seeley also supplies wall covering material to Columbus Coated Fabrics Division of Borden, Incorporated, Columbus, Ohio, among others.

Source record↗
NASA NTRS2005

Releasable locking mechanisms

In the aerospace field spacecraft components are held together by separation systems until a specific time when they must be separated or deployed. Customarily a threaded joining bolt engages one of the components to be joined, and a threaded nut is placed on that bolt against the other component so they can be drawn together by a releasable locking assembly. The releasable locking assembly herein includes a plunger having one end coupled to one end of a plunger bolt. The other end is flanged to abut and compress a coil spring when the plunger is advanced toward the interface plane between the two components. When the plunger is so advanced toward the interface plane, the end of the plunger bolt can be connected to the joining bolt. Thus during retraction the joining bolt is drawn to one side of the interface plane by the force of the expanding spring.

Ahmed, Rafiq↗
NASA NTRS2009

Mechanical Overview of the International X-Ray Observatory

The International X-ray Observatory (IXO) is a new collaboration between NASA, ESA, and JAXA which is under study for launch in 2020. IXO will be a large 6600 kilogram Great Observatory-class mission which will build upon the legacies of the Chandra and XMM-Newton X-ray observatories. It combines elements from NASA's Constellation-X program and ESA's XEUS program. The observatory will have a 20-25 meter focal length, which necessitates the use of a deployable instrument module. Currently the project is actively trading configurations and layouts of the various instruments and spacecraft components. This paper will provide a snapshot of the latest observatory configuration under consideration and summarize the observatory from the mechanical engineering perspective.

Robinson, David W.↗
NASA NTRS2009

Materials International Space Station Experiment - 6A and 6B

Materials on the International Space Station Experiment 6 (MISSE-6A and 6B) is a test bed for materials and coatings attached to the outside of the space station that are being evaluated for the effects of atomic oxygen, direct sunlight, radiation and extremes of heat and cold. This experiment allows the development and testing of new materials to better withstand the rigors of space environments. Results will provide a better understanding of the durability of various materials in space, leading to the design of stronger, more durable spacecraft components.

Kinard, William H.↗
NASA NTRS2007

Foam Core Shielding for Spacecraft

A foam core shield (FCS) system is now being developed to supplant multilayer insulation (MLI) systems heretofore installed on spacecraft for thermal management and protection against meteoroid impacts. A typical FCS system consists of a core sandwiched between a face sheet and a back sheet. The core can consist of any of a variety of low-to-medium-density polymeric or inorganic foams chosen to satisfy application-specific requirements regarding heat transfer and temperature. The face sheet serves to shock and thereby shatter incident meteoroids, and is coated on its outer surface to optimize its absorptance and emittance for regulation of temperature. The back sheet can be dimpled to minimize undesired thermal contact with the underlying spacecraft component and can be metallized on the surface facing the component to optimize its absorptance and emittance. The FCS systems can perform better than do MLI systems, at lower mass and lower cost and with greater volumetric efficiency.

Adams, Marc↗
NASA NTRS2003

Spacecraft Design Thermal Control Subsystem

This slide presentation reviews the functions of the thermal control subsystem engineers in the design of spacecraft. The goal of the thermal control subsystem that will be used in a spacecraft is to maintain the temperature of all spacecraft components, subsystems, and all the flight systems within specified limits for all flight modes from launch to the end of the mission. For most thermal control subsystems the mass, power and control and sensing systems must be kept below 10% of the total flight system resources. This means that the thermal control engineer is involved in all other flight systems designs. The two concepts of thermal control, passive and active are reviewed and the use of thermal modeling tools are explained. The testing of the thermal control is also reviewed.

thermal control↗
NASA NTRS2009

Development of Backscatter X-Ray Imaging Techniques for Space Vehicle Applications

This slide presentation reviews the development of backscatter x ray (BSX) imaging techniques to perform inspection of spacecraft components. The techniques are currently being enhanced to advance Non-Destructive Testing (NDT) methods for future space vehicle applications. The presentation includes an overview of x ray techniques, a description of current BSX applications used on the space shuttle, the development for Constellation applications, and the use of the system for foam applications.

Bartha, Bence B.↗