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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Verification Test of Automated Robotic Assembly of Space Truss Structures

A multidisciplinary program has been conducted at the Langley Research Center to develop operational procedures for supervised autonomous assembly of truss structures suitable for large-aperture antennas. The hardware and operations required to assemble a 102-member tetrahedral truss and attach 12 hexagonal panels were developed and evaluated. A brute-force automation approach was used to develop baseline assembly hardware and software techniques. However, as the system matured and operations were proven, upgrades were incorporated and assessed against the baseline test results. These upgrades included the use of distributed microprocessors to control dedicated end-effector operations, machine vision guidance for strut installation, and the use of an expert system-based executive-control program. This paper summarizes the developmental phases of the program, the results of several assembly tests, and a series of proposed enhancements. No problems that would preclude automated in-space assembly or truss structures have been encountered. The test system was developed at a breadboard level and continued development at an enhanced level is warranted.

Rhodes, Marvin D.↗
NASA NTRS2001

Vibration Test Demonstrated Dynamic Capability of an Operating Stirling Convertor

The NASA Glenn Research Center and the U.S. Department of Energy are currently developing a high-efficiency, long-life, free piston Stirling convertor for use as an advanced spacecraft power system for future NASA missions. As part of this development, a Stirling Technology Demonstrator Converter (TDC), developed by Stirling Technology Company for the Department of Energy, was vibration tested at Glenn's Structural Dynamics Laboratory in November and December 1999. This testing demonstrated that the Stirling TDC is able to withstand the harsh random vibration (20 to 2000 Hz) seen during a typical spacecraft launch and to survive with no structural damage or functional power performance degradation, thereby enabling its use in future spacecraft power systems. Glenn and Stirling personnel conducted tests on a single 55 We TDC. The purpose was to characterize the TDC's structural response to vibration and to determine if the TDC could survive the vibration criteria established by the Jet Propulsion Laboratory for launch environments. The TDC was operated at full-stroke and full power conditions during the vibration testing.

Hughes, William O.↗
NASA NTRS1992

Experimental breakdown of selected anodized aluminum samples in dilute plasmas

Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

Grier, Norman T.↗
NASA NTRS1977

A gamma-ray testing technique for spacecraft

The simulated cosmic radiation effect on a spacecraft structure is evaluated by gamma ray testing in relation to structural thickness. A drawing of the test set-up is provided and measurement errors are discussed.

Gribov, B. S.↗
NASA NTRS1972

Dynamic testing for shuttle design verification

Space shuttle design verification requires dynamic data from full scale structural component and assembly tests. Wind tunnel and other scaled model tests are also required early in the development program to support the analytical models used in design verification. Presented is a design philosophy based on mathematical modeling of the structural system strongly supported by a comprehensive test program; some of the types of required tests are outlined.

Green, C. E.↗
NASA NTRS1968

High performance structures

Materials selection, structural geometry, proof testing and statistical screening, prestressing, and system energy as tools for designing optimum trusses and other high performance structures

Barnett, R. L.↗
NASA NTRS1992

ASRM subscale plume deflector testing

This paper reports the results of the scale model (1/22) testing of candidate refractory materials to be used as surface coatings for a solid rocket motor plume deflector structure. Five ROM tests were conducted to acquire data to support the selection, thickness determination, and placement of the materials. All data acquisition was achieved through nonintrusive methods. The tests demonstrated that little or no reductions in performance of the full-scale deflector would be experienced if the most economical materials were selected for construction.

Douglas, Freddie, III↗
NASA NTRSDate not supplied

AXAF Hypervelocity Impact Test Results

Composite and honeycomb panels are commonly used for spacecraft structural components. The impact test results and analysis of six different composite and honeycomb combinations for use on the advanced X-ray astrophysics facility (AXAF) are reported. The AXAF consists of an X-ray telescope and the associated detecting devices attached to an octagonal spacecraft with an internal propulsion system. The spacecraft's structural panels and optical bench are made of two different graphite fiber reinforced polyimides or composite panels bonded to either side of an aluminum honeycomb. The instrument is required to have at least a 0.92 probability of no failure of any of the critical elements due to meteoroids and debris. In relation to the no-failure probability determination in its low earth orbit environment, hypervelocity impact testing was performed to determine the ballistic limit range and the extent of damage due to impact. The test results for a power and signal cable bundle located behind a panel are presented. Tests planned for a multilayer insulation (MLI) blanket and four types of cable bundles are discussed.

Cynthia L Frost↗
NASA NTRS1982

Composite structural materials

Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

Ansell, G. S.↗
NASA NTRS1988

Multiple boundary condition test (MBCT) - Identification with mode shapes

The multiple boundary condition test (MBCT) approach is a ground test method to test a class of large flexible structures which cannot be ground tested by state-of-the-art test methods due to the adverse terrestrial environment. The ultimate objective of a ground test is considered to be the validation and update of a mathematical model of the structure. The research to date has indicated the MBCT does work on numerical simulations and on experimental laboratory hardware. To date only the eigenvalue has been used in the model correlation/update by inclusion of the information in the nonlinear terms resulting from the difference between the analytical and measured eigenvectors. This paper presents the results of utilizing additional information, namely the difference in the analytical and the test eigenvectors, in the validation and update of the mathematical model.

Kuo, C. P.↗
NASA NTRS1977

Results of graphite-polyimide isogrid panel testing

A procedure was developed for fabricating short-fiber HTS graphite and NR150B2 polyimide resin into an isogrid configuration. After fabrication, the panels were subjected to structural analysis and testing. The testing program is described.

Hyer, M. W.↗
NASA NTRS1973

Fatigue of supersonic transport materials using simulated flight-by-flight loading

Methods to reduce the fatigue test time for structural materials which are candidates for supersonic transport airplanes were investigated by conducting real-time and accelerated fatigue tests. The tests employed sequences of stresses and temperatures to simulate the flights of a Mach 3 transport airplane. Some of the simulated flights were altered to determine the effect of the design mean stress and the number of stress cycles per flight on fatigue life. Salt solution was also applied in other tests. Notched Ti-8Al-1Mo-1V and Ti-6Al-4V were used in the investigation.

Imig, L. A.↗
NASA NTRS2008

Two-Stage Passive Vibration Isolator

The design and testing of a structural system were implemented to hold the optics of the planned Space Interferometry Mission (SIM) at positions and orientations characterized by vibrational translation and rotation errors of no more than a few nanometers or a few milliarcseconds, respectively. Much of the effort was devoted to a test bed for verifying the predicted behavior of a vibration- isolation structural subsystem working together with an active control system for positioning and orienting the SIM optics. There was considerable emphasis on the vibration-isolation subsystem, which was passive and comprised two stages. The main sources of vibration were six reaction wheels in an assembly denoted the "backpack." The first vibration-isolation stage consisted of hexapod isolator mounts - one for each reaction wheel - characterized by a natural vibration frequency of 10 Hz. The second stage was a set of three beams, disposed between the backpack and the structure that held the SIM optics, that were flexured such that they transmitted only bending loads, with a natural vibrational frequency and damping of about 5 Hz and 4 percent, respectively. Preliminary test results were presented and characterized as demonstrating the effectiveness of the two-stage vibration-isolation design.

Goullioud, Renaud↗
NASA NTRS1993

An expert system executive for automated assembly of large space truss structures

Langley Research Center developed a unique test bed for investigating the practical problems associated with the assembly of large space truss structures using robotic manipulators. The test bed is the result of an interdisciplinary effort that encompasses the full spectrum of assembly problems - from the design of mechanisms to the development of software. The automated structures assembly test bed and its operation are described, the expert system executive and its development are detailed, and the planned system evolution is discussed. Emphasis is on the expert system implementation of the program executive. The executive program must direct and reliably perform complex assembly tasks with the flexibility to recover from realistic system errors. The employment of an expert system permits information that pertains to the operation of the system to be encapsulated concisely within a knowledge base. This consolidation substantially reduced code, increased flexibility, eased software upgrades, and realized a savings in software maintenance costs.

Allen, Cheryl L.↗
NASA NTRS2015

Transient Thermal Testing and Analysis of a Thermally Insulating Structural Sandwich Panel

A core configuration was devised for a thermally insulating structural sandwich panel. Two titanium prototype panels were constructed to illustrate the proposed sandwich panel geometry. The core of one of the titanium panels was filled with Saffil(trademark) alumina fibrous insulation and the panel was tested in a series of transient thermal tests. Finite element analysis was used to predict the thermal response of the panel using one- and two-dimensional models. Excellent agreement was obtained between predicted and measured temperature histories.

Blosser, Max L.↗
NASA NTRS2017

NASA's Space Launch System Gains Momentum Toward Integration and Testing

NASA's Space Launch System (SLS) entered a new phase in 2017, completing major structural manufacturing on the core stage and delivering the first flight hardware to NASA's Kennedy Space Center (KSC). The program is now transitioning to integration, assembly and testing in preparation for launch readiness in late 2019. Core stage prime contractor Boeing concluded welding of the major core stage components for Exploration Mission 1 (EM-1) with the liquid hydrogen flight tank, following completion of the engine section, liquid oxygen tank, and forward skirt. Technicians also completed assembly of the bolted intertank, and all sections are currently in hardware integration. The engine section structural test article was shipped to NASA's Marshall Space Flight Center (MSFC) and began testing in 2017. The core stage pathfinder shipped to NASA's Michoud Assembly Facility (MAF). Booster prime contractor Orbital ATK made significant progress casting motor segments for SLS, with several segments finishing processing and in storage. Forward and aft sections of the boosters are being refurbished at KSC. RS-25 prime contractor Aerojet Rocketdyne completed SLS adaptation testing and qualification of four new EM-1 controllers. The four EM-1 engines are ready and waiting for shipment from NASA's Stennis Space Center (SSC) to Michoud Assembly Facility (MAF) for core stage integration in preparation for green run testing at SSC. The EM-1 Interim Cryogenic Propulsion System (ICPS) became the first major piece of SLS to arrive at KSC. Welding is complete on the EM-1 Launch Vehicle Stage Adapter (LVSA) and the flight Orion Stage Adapter (OSA). SLS is critical to U.S. leadership in future human and robotic space exploration, including a presence on the moon in preparation for missions deeper into space. This paper will elaborate on 2017 SLS progress and progress envisioned for 2018.

Askins, Bruce R.↗
NASA NTRS1991

Structural evaluation of curved stiffened composite panels fabricated using a THERM-Xsm process

The use of composites in aircraft structures is often limited by material and manufacturing costs which, for some designs and applications, are prohibitively high. To increase the frequency of application of composites in primary airframe components alternative manufacturing processes are sought that reduce cost and/or enhance structural efficiency. One alternative process involves the use of THERM-Xsm as the pressure transfer medium during autoclave curing. THERM-Xsm, a silicon-based flow able polymer which behaves like a liquid under autoclave presssure, transmits quasi-hydrostatic pressure to all contacting surfaces of the part to be cured. Once the autoclave pressure is relieved, THERM-Xsm reverts back to the powdery solid state and can be reused many times. The THERM-Xsm process to be evaluated is depicted and consists of (1) enclosing the tool and part to be cured by a set of frames that create a box, (2) pouring THERM-Xsm powder onto the part and filling the box, and (3) placing a vacuum bag over the box assembly. In this program, a separating non-porous film (Teflon) was placed between the part to be cured and THERM-Xsm powder to avoid any contamination. The use of THERM-Xsm has two significant advantages over conventional manufacturing procedures. First, it eliminates complicated hard tooling since it guarantees uniform pressure transfer and thus, good compaction at complex structural details (such as frame-stiffener intersections and corners). Second, it greatly simplifies vacuum bagging, since once the part to be cured is covered by THERM-Xsm powder, the vacuum bag need only conform to a relatively flat shape reducing significantly the number of pleats required. A program is on-going at Sikorsky Aircraft to evaluate the structural performance of complex composite fuselage structures made with this THERM-Xsm process and to quantify the impact of THERM-Xsm on manufacturing labor hours and cost. The program involves fuselage panel optimization analysis, a building block test program where structural details representative of the full-scale article are analyzed and tested, and static and fatigue test/analysis of the full-scale test articles. The main results of this program are reported.

Kassapoglou, Christos↗