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At least 1,027 records · Page 57

Task 4 supporting technology. Part 1: Detailed test plan for leading edge tile development. Leading edge material development and testing

This task develops two alternative candidate tile materials for leading edge applications: coated alumina enhanced thermal barrier (AETB) tile and silicone impregnated reusable ceramic ablator (SIRCA) tile. Upon reentry of the X-33/RLV space vehicle, the leading edges experience the highest heating rates and temperatures. The wing leading edge and nose cap experience peak temperatures in the range 2000 to 2700 F. Replacing reinforced carbon-carbon (RCC) with tile-based thermal protection system (TPS) materials is the primary objective. Weight, complexity, coating impact damage, and repairability are among the problems that this tile technology development addresses. The following subtasks will be performed in this development effort: tile coating development; SIRCA tile development; robustness testing of tiles; tile repair development; tile operations/processing; tile leading edge configuration; and life cycle testing.

Hogenson, P. A.↗

DNA-DSB in CHO-K1 cells induced by heavy-ions: Break rejoining and residual damage (GSI)

DNA double strand breaks (DSB's) are the critical lesions involved in cellular effects of ionizing radiation. Therefore, the evaluation of DSB induction in mammalian cells after heavy ion irradiation is an essential task for the assessment of high-LET radiation risk in space. Of particular interest has been the question of how the biological efficiency for the cellular inactivation endpoint relates to the initial lesions (DSBs) at varying LETs. For cell killing, an increased Relative Biological Efficiency (RBE) has been determined for highLET radiation around 100-200 keV/mu m. At higher LET, the RBE's decrease again to values below one for the very heavy particles. At GSI, DSB-induction was measured in CHO-K1 cells following irradiation with accelerated particles covering a wide LET range. The electrophoretic elution of fragmented DNA out of agarose plugs in a constant electrical field was applied for the detection of DSB's. The fraction of DNA retained was determined considering the relative intensities of ethidium bromide fluorescence in the well and in the gel lane. Dose-effect curves were established, from which the RBE for DSB induction was calculated at a fraction of 0.7 of DNA retained In summary, these rejoining studies are in line with an enhanced severity of the DNA DSB's at higher LET's, resulting in a decreased repairability of the induced lesions. However, no information concerning the fidelity of strand breaks rejoining is provided in these studies. To assess correct rejoining of DNA fragments an experimental system involving individual DNA hybridization bands has been set up. In preliminary experiments Sal I generated DNA fragments of 0.9 Mbp were irradiated with xrays and incubated for repair However, restitution of the original signals was not observed, probably due to the high radiation dose necessary for breakage of a fragment of this size. A banding pattern with NotI hybridization signals in a higher MW range (3Mbp) has been obtained by varying the electrophoretic conditions and correct rejoining studies will be further developed in this system.

Taucher-Scholz, G.↗

Special-Purpose Robotic Welder

Robotic-welding apparatus developed for use in repairing main combustion chamber of rocket engine. Design features beneficial in other robotic-welding applications; for example, manufacture and repair of pressure vessels, chemical-processing vessels, etc. Design problem solved by iterative application of computer-aided techniques.

Mcferrin, David C.↗

Chill-Bar Assembly For Cooling Areas Adjacent To Welds

Assembly of custom-shaped water-cooled chill bars developed for use during repair process in which cracks and pinholes in rocket-engine combustion chamber welded closed. Held in required relative geometric relationships by rigid framework, chill bars pressed against surface of chamber to conduct heat away from areas surrounding welds, preventing damage caused by overheating of areas not meant to be welded. Design features beneficial in other welding applications; for example, manufacture and repair of pressure vessels, chemical-processing vessels, and complexly shaped laboratory vacuum vessels.

Hoffman, David S.↗

Particulate electron beam weld emission hazards in space

The electron-beam welding process is well adapted to function in the environment of space. The Soviets were the first to demonstrate welding in space in the mid-1980's. Under the auspices of the International Space Welding Experiment (ISWE), an on-orbit test of a Ukrainian designed electron-beam welder (the Universal Hand Tool or 'UHT') is scheduled for October of 1997. The potential for sustained presence in space with the development of the international space station raises the possibility of the need for construction and repair in space. While welding is not scheduled to be used in the assembly of the space station, repair of damage from orbiting debris or meteorites is a potential need. Furthermore, safe and successful welding in the space environment may open new avenues for design and construction. The safety issue has been raised with regard to hot particle emissions (spatter) sometimes observed from the weld during operations. On earth the hot particles pose no particular hazard, but in space there exists the possibility for burn-through of the space suit which could be potentially lethal. Contamination of the payload bay by emitted particles could also be a problem.

Bunton, Patrick H.↗

Design and evaluation of a bolted joint for a discrete carbon-epoxy rod-reinforced hat section

The use of prefabricated pultruded carbon-epoxy rods has reduced the manufacturing complexity and costs of stiffened composite panels while increasing the damage tolerance of the panels. However, repairability of these highly efficient discrete stiffeners has been a concern. Design, analysis, and test results are presented in this paper for a bolted-joint repair for the pultruded rod concept that is capable of efficiently transferring axial loads in a hat-section stiffener on the upper skin segment of a heavily loaded aircraft wing component. A tension and a compression joint design were evaluated. The tension joint design achieved approximately 1.0% strain in the carbon-epoxy rod-reinforced hat-section and failed in a metal fitting at 166% of the design ultimate load. The compression joint design failed in the carbon-epoxy rod-reinforced hat-section test specimen area at approximately 0.7% strain and at 110% of the design ultimate load. This strain level of 0.7% in compression is similar to the failure strain observed in previously reported carbon-epoxy rod-reinforced hat-section column tests.

Rousseau, Carl Q.↗

Design and Evaluation of a Bolted Joint for a Discrete Carbon-Epoxy Rod-Reinforced Hat Section

The use of pre-fabricated pultruded carbon-epoxy rods has reduced the manufacturing complexity and costs of stiffened composite panels while increasing the damage tolerance of the panels. However, repairability of these highly efficient discrete stiffeners has been a concern. Design, analysis, and test results are presented in this paper for a bolted-joint repair for the pultruded rod concept that is capable of efficiently transferring axial loads in a hat-section stiffener on the upper skin segment of a heavily loaded aircraft wing component. A tension and a compression joint design were evaluated. The tension joint design achieved approximately 1.0 percent strain in the carbon-epoxy rod-reinforced hat-section and failed in a metal fitting at 166 percent of the design ultimate load. The compression joint design failed in the carbon-epoxy rod-reinforced hat-section test specimen area at approximately 0.7 percent strain and at 110 percent of the design ultimate load. This strain level of 0.7 percent in compression is similar to the failure strain observed in previously reported carbon-epoxy rod-reinforced hat-section column tests.

Baker, Donald J.↗

Hubble Space Telescope - First Servicing Mission: Down to Earth Logistics - From GSFC to KSC and Back

The Hubble Space Telescope First Servicing Mission is a major accomplishment for NASA and has drawn world-wide attention and interest. The extravehicular servicing and repair activities performed by the STS-61 crew were the most ambitious ever undertaken. Their unprecedented success in performing on-orbit repair and maintenance, particularly in correcting the aberration in the primary mirror, has enabled the HST to provide sensational images and the anticipation of exciting scientific discoveries. Although the whole world watched the televised logistics activities (on-orbit maintenance) that took place in space, few are aware of the time and effort that went into planning and executing the space logistics that takes place with our feet on the ground. This paper addresses a major part of that effort - the packaging, handling, and transportation (PH&T) activities required to ship the GSFC HST space flight hardware and ground support equipment to KSC for launch and the post launch return to GSFC. It addresses the logistics and transportation planning for the containers for the Solar Array Carrier, the Orbital Replacement Unit Carrier, and the Flight Support System and their transporters, and the over land and water portions of the shipments.

Kubicko, Richard M.↗

Development and Implementation of Environmentally Compatible Solid Film Lubricants

Multi-body launch vehicles require the use of Solid Film Lubricants (SFLs) to allow for unrestricted relative motion between structural assemblies and components during lift off and ascent into orbit. The Space Shuttle Solid Rocket Booster (SRB), uses a dual coat, ceramic-bonded high temperature SFL in several locations such as restraint hardware between the SRB aft skirt and the Mobile Launch Platform (MLP), the aft SRB/External Tank (ET) attach struts, and the forward skirt SRB/ET attach ball assembly. The proposed National Launch System (NLS) may require similar applications of SFLs for attachment and restraint hardware. A family of environmentally compatible nonlead/antimony bearing alternative SFLs have been developed including a compatible repair material. In addition, commercial applications for SFLs on transportation equipment, all types of lubricated fasteners, and energy related equipment allow for wide usage of these new lubricants. The new SFLs named BOOSTERLUBE is a family of single layer thin film (0.001 inch maximum) coatings that are a unique mixture of non-hazardous pigments in a compatible resin system that allows for low temperature curing (450 F). Significant savings in energy and processing time as well as elimination of hazardous material usage and disposal would result from the non-toxic onestep SFL application. Compatible air-dry field repair lubricants will help eliminate disassembly of launch vehicle restraint hardware during critical time sensitive assembly operations.

Novak, Howard L.↗

Development and Implementation of Environmentally Compatible Solid Film Lubricants

Multi-body launch vehicles require the use of Solid Film Lubricants (SFLs) to allow for unrestricted relative motion between structural assemblies and components during lift-off and ascent into orbit. The Space Shuttle Solid Rocket Booster (SRB), uses a dual coat, ceramic-bonded high temperature SFL in several locations such as restraint hardware between the SRB aft skirt and the Mobile Launch Platform (MLP), the aft SRB/External Tank (ET) attach struts, and the forward skirt SRB/ET attach ball assembly. Future launch systems may require similar applications of SFLs for attachment and restraint hardware. A family of environmentally compatible non-lead/antimony bearing alternative SFLs have been developed including a compatible repair material. In addition, commercial applications for SFLs on transportation equipment, all types of lubricated fasteners, and energy related equipment allow for wide usage's of these new lubricants. The new SFLs trade named BOOSTERLUBE is a family of single layer thin film (0.001 inch maximum) coatings that are a unique mixture of non-hazardous pigments in a compatible resin system that allows for low temperature curing (450 F). Significant savings in energy and processing time as well as elimination of hazardous material usage and disposal would result from the non-toxic one-step SFL application. Compatible air-dry field repair lubricants will help eliminate disassembly of launch vehicle restraint hardware during critical time sensitive assembly operations.

Novak, Howard L.↗

Development and Implementation of Environmentally Compatible Solid Film Lubricants

Multi-body launch vehicles require the use of Solid Film Lubricants (SFLS) to allow for unrestricted relative motion between structural assemblies and components during lift-off and ascent into orbit. The Space Shuttle Solid Rocket Booster (SRB), uses a dual coat, ceramic-bonded high temperature SFL in several locations such as restraint hardware between the SRB aft skirt and the Mobile Launch Platform (MLP), the aft SRB/External Tank (ET) attach struts, and the forward skirt SRB/ET attach ball assembly. Future launch systems may require similar applications of SFLs for attachment and restraint hardware. A family of environmentally compatible non-lead/antimony bearing alternative SFLs have been developed including a compatible repair material. In addition, commercial applications for SFLs on transportation equipment, all types of lubricated fasteners, and energy related equipment allow for wide usage's of these new lubricants. The new SFLs trade named BOOSTERLUBE is a family of single layer thin film (0.001 inch maximum) coatings that are a unique mixture of non-hazardous pigments in a compatible resin system that allows for low temperature curing (450F). Significant savings in energy and processing time as well as elimination of hazardous material usage and disposal would result from the non-toxic one-step SFL application. Compatible air-dry field repair lubricants will help eliminate disassembly of launch vehicle restraint hardware during critical time sensitive assembly operations.

Novak, Howard L.↗

Carbon Fiber Reinforced/Silicon Carbide Turbine Blisk Testing in the SIMPLEX Turbopump

A program designed to implement a ceramic matrix composite integrally bladed disk (blisk) into rocket engine style turbomachinery has successfully completed testing. The Marshall Space Flight Center (MSFC) program, utilizing the MSFC turbomachinery design, analysis, and testing capabilities along with materials development capabilities from both Glenn Research Center (GRC) and MSFC, has tested two carbon fiber reinforced silicon carbide blisks in the Simplex Turbopump at MSFC's Test Stand 500. One blisk contained a polar woven fiber preform, while the second blisk tested utilized a quasi-isotropic preform. Vhile earlier papers have chronicled the program's design, material testing, and torque testing efforts, this paper focuses on the testing of the blisks in the Simplex turbopump. Emphasis will be placed on the actual condition of the blisks before and after the testing test program design methodology, and conclusions that can be drawn from the test data and blisk final conditions. The program performed three separate test series. The first series was needed to validate that the Simplex turbopump was correctly re-built following a major incident to the turbopump. The turbopump had two major differences from the original design. The most obvious difference was the sleeve required throughout the bore of the main housing. The second major difference was modifications to the pump diffuser to improve performance. Several areas were burnt during the incident and were either repaired by weld repair (pump inlet housing) or simply smoothed out (turbine nozzle discharge). The test series was designed to weed out any turbopump design and manufacturing flaws or fatigue issues prior to putting the C/SiC blisks into it. The second and third series were the C/SiC blisk test series. The primary goal of these series was to expose the blisks to as much fatigue causing dynamic stress as possible to examine the material's capability. Initially, the test plan was to put equal time on the two blisks, however, as the test series progressed, the funding allowed additional testing to occur. The additional test time was placed on the polar weave blisk. The total test time accrued on the polar blisk was 2550 seconds with 860 seconds near the turbopump design speed of 25,000 rpm. This testing included 6 tests / 775 seconds pumping liquid nitrogen and 7 tests / 1775 seconds pumping liquid oxygen. The drive gas for all of the tests was gaseous nitrogen due to the lack of hot gas source for the Simplex turbopump. The quasi-isotropic blisk was tested for XX total tests and XXXX seconds with X tests/XXXX seconds pumping liquid nitrogen and X tests/XXXX seconds pumping liquid \oxygen.During the test series, the blisks were inspected following each test. Inspections initially were viewed from the downstream side of the blisks only. Midway through the testing, a method of borescoping the leading edges of the blades was devised, and subsequently, both sides of the blades were inspected following each test. The leading and trailing edges of the polar blisk held up better than the quasi-isotropic blisk. This was a known possibility due to the varying fiber direction in the blades as the rectangular preform weave is cut in a circular pattern. The surprising fact about the testing was that there was no measurable performance loss due to the inaccuracies in the blade manufacturing in the C/SiC blisks, the surface roughness C/SiC of the blades, or the loss of the material in the polar blisk. A performance shift was seen in the quasi-isotropic blisk as portions of the leading and trailing edges were lost. After the testing was completed, detailed inspections of the blisks were performed. The largest surprise was the polar blisk had a obvious crack in a single blade that was located nearly midspan which was not detected in test. The crack ran completely through the blade circumferenciary and through the radial length of the blade. However, the crack does not appear to extend into the blisk hub. Although the cause of the crack is still under investigation, the material appears to be tolerant of this crack, and other hairline cracks discovered under higher magnification. This bodies well for eventual use of this material in actual flight turbopumps where monolithic fracture toughness issues limit its use.

Genge, Gary G.↗

Restoration of the Hypersonic Tunnel Facility at NASA Glenn Research Center, Plum Brook Station

The NASA Glenn Research Center's Hypersonic Tunnel Facility (HTF), located at the Plum Brook Station in Sandusky, Ohio, is a non-vitiated, free-jet facility, capable of testing large-scale propulsion systems at Mach Numbers from 5 to 7. As a result of a component failure in September of 1996, a restoration project was initiated in mid- 1997 to repair the damage to the facility. Following the 2-1/2 year effort, the HTF has been returned to an operational condition. Significant repairs and operational improvements have been implemented in order to ensure facility reliability and personnel safety. As of January 2000, this unique, state-of-the-art facility was ready for integrated systems testing.

Woodling, Mark A.↗

Wind Tunnel Management and Resource Optimization: A Systems Modeling Approach

Time, money, and, personnel are becoming increasingly scarce resources within government agencies due to a reduction in funding and the desire to demonstrate responsible economic efficiency. The ability of an organization to plan and schedule resources effectively can provide the necessary leverage to improve productivity, provide continuous support to all projects, and insure flexibility in a rapidly changing environment. Without adequate internal controls the organization is forced to rely on external support, waste precious resources, and risk an inefficient response to change. Management systems must be developed and applied that strive to maximize the utility of existing resources in order to achieve the goal of "faster, cheaper, better". An area of concern within NASA Langley Research Center was the scheduling, planning, and resource management of the Wind Tunnel Enterprise operations. Nine wind tunnels make up the Enterprise. Prior to this research, these wind tunnel groups did not employ a rigorous or standardized management planning system. In addition, each wind tunnel unit operated from a position of autonomy, with little coordination of clients, resources, or project control. For operating and planning purposes, each wind tunnel operating unit must balance inputs from a variety of sources. Although each unit is managed by individual Facility Operations groups, other stakeholders influence wind tunnel operations. These groups include, for example, the various researchers and clients who use the facility, the Facility System Engineering Division (FSED) tasked with wind tunnel repair and upgrade, the Langley Research Center (LaRC) Fabrication (FAB) group which fabricates repair parts and provides test model upkeep, the NASA and LARC Strategic Plans, and unscheduled use of the facilities by important clients. Expanding these influences horizontally through nine wind tunnel operations and vertically along the NASA management structure greatly increases the complexity of developing a model that can be used for successfully implementing a standardized management planning tool. The objective of this study was to implement an Integrated Wind Tunnel Planning System to improve the operations within the aeronautics testing and research group, in particular Wind Tunnel Enterprise. The study included following steps: Conducted literature search and expert discussions (NASA and Old Dominion University faculty), Performed environmental scan of NASA Langley wind tunnel operations as foundation for problem definition. Established operation requirements and evaluation methodologies. Examined windtunnel operations to map out the common characteristics, critical components, and system structure. Reviewed and evaluated various project scheduling and management systems for implementation, Evaluated and implemented "Theory of Constraints (TOC)" project scheduling methodology at NASA Langley wind tunnel operations together with NASA staff.

Jacobs, Derya, A.↗

Ames Research Center Mars/Pathfinder Heat Shield Design Verification ARC-JET Test

Design verification tests were performed on samples representing the aerobrake of the Mars/Pathfinder vehicle. The test specimens consisted of the SLA-561V ablator bonded to the honeycomb structure. The primary objective was to evaluate the ablation materials performance and to measure temperatures within the ablator, at the structural bondline and at the back sheet of the honeycomb structure. Other objectives were to evaluate the effect of ablative repair plug material treatment and voids in the heat shield. A total of 29 models were provided for testing in the Ames 60MW arc-jet facility. Of these, 23 models were flat-faced and six remaining models were curved edge ones, intended to simulate the conditions on the curved rim of the forebody where the maximum shear occurred. Eight sets of test conditions were used. The stagnation point heating rates varied from 47 to 240 W/cm2 and the stagnation pressures from 0.15 to 0.27 atm. (The maximum flight values are 132 W/cm2 and 0.25 atm) The majority of these runs were made at a nominal stagnation pressure of 0.25 atm. Two higher pressure runs were made to check the current (denser) ablation material for spallation, or other forms of thermal stress failure. Over 60% of the flatfaced models yielded good thermocouple data and all produced useful surface recession information. Of the five curved-edge models that were tested, only one gave good data; the remaining ones experienced model-holder failure. The test results can be summarized by noting that no failure of the ablative material was observed on any model. Also, the bondline temperature design limit of 250 C was never reached within an equivalent flight time despite a stagnation point heat load that exceeded the maximum flight value by up to 130%. At heating rates of over 200W/cm2 and stagnation pressures of 0.25 atm, or greater, the average surface recessions exceeded 0.5 cm on some models. The surface roughness increased dramatically at pressures above 0.25 atm and was four times greater at 0.27 atm than at 0.25 atm. Procured repair plug material performed much better than room-temperature cured plugs, as observed in the previous tests. Voids in the ablator did not increase local temperatures and gaps did not grow during testing.

Tran, Huy K.↗

Model Based Autonomy for Robust Mars Operations

Space missions have historically relied upon a large ground staff, numbering in the hundreds for complex missions, to maintain routine operations. When an anomaly occurs, this small army of engineers attempts to identify and work around the problem. A piloted Mars mission, with its multiyear duration, cost pressures, half-hour communication delays and two-week blackouts cannot be closely controlled by a battalion of engineers on Earth. Flight crew involvement in routine system operations must also be minimized to maximize science return. It also may be unrealistic to require the crew have the expertise in each mission subsystem needed to diagnose a system failure and effect a timely repair, as engineers did for Apollo 13. Enter model-based autonomy, which allows complex systems to autonomously maintain operation despite failures or anomalous conditions, contributing to safe, robust, and minimally supervised operation of spacecraft, life support, In Situ Resource Utilization (ISRU) and power systems. Autonomous reasoning is central to the approach. A reasoning algorithm uses a logical or mathematical model of a system to infer how to operate the system, diagnose failures and generate appropriate behavior to repair or reconfigure the system in response. The 'plug and play' nature of the models enables low cost development of autonomy for multiple platforms. Declarative, reusable models capture relevant aspects of the behavior of simple devices (e.g. valves or thrusters). Reasoning algorithms combine device models to create a model of the system-wide interactions and behavior of a complex, unique artifact such as a spacecraft. Rather than requiring engineers to all possible interactions and failures at design time or perform analysis during the mission, the reasoning engine generates the appropriate response to the current situation, taking into account its system-wide knowledge, the current state, and even sensor failures or unexpected behavior.

Kurien, James A.↗

Robosphere1: Building A Self-Sustaining Robotic Ecology for Mars Exploration

Robotic exploration of Mars has been a "one shot" approach where each surface mission is planned typically with a rover that will perform a series of experiments for a few weeks or months, until the robot becomes unable to operate in the harsh Mars conditions and simply "dies". It would clearly be desirable to have robots on Mars that can last for much longer periods of time, I propose that there is an approach to sustained robotic exploration that can also pave the way to future human presence. The idea is to continue building a robotic infrastructure with every mission we send. The approach is to built a team of modular robots that could repair individual members when they break down. We could "seed" areas of interest with sturdy power stations (solar, chemical) that teams of robots could use to recharge themselves. We could also seed parts and modules the robots could access for self-repair. No mission could really "fail" if we simply keep adding to and maintaining the existing infrastructure. Simply landing a package of parts will be a success. In time we create a loose infrastructure that can be controlled and augmented from earth on a continuing basis, and which could eventually pave the way for human exploration. I propose that we could begin to build this infrastructure from relatively simple modular robots. Imagine 2 "spider-like" robots built out of small modular snap-in pieces, a bin of these pieces and a bin of snap-in end effectors. One of the spiders breaks down, i.e. one of its modules needs to be replaced. The second spider comes to the rescue and helps the first one replace the broken module. Assuming the input of fresh modules, this process can continue indefinetly. Now start separating robotic explorers from robotic "mechanics", start adding, a category of mechanics that are able to fix at least some of the broken modules (and which in turn can be fixed by the original mechanics), The need for a fresh influx of modules is thus reduced. I submit that we could bootstrap a robotic ecology until it needs very little material from earth and can rely mostly on in-situ resources., We can experiment with this concept in an earthbound facility that can also simulate Mars conditions. I propose that we call this facility Robosphere1.

Colombano, Silvano P.↗

Structural Analysis

After an 800-foot-tall offshore oil recovery platform collapsed, the engineers at Engineering Dynamics, Inc., Kenner, LA, needed to learn the cause of the collapse, and analyze the proposed repairs. They used STAGSC-1, a NASA structural analysis program with geometric and nonlinear buckling analysis. The program allowed engineers to determine the deflected and buckling shapes of the structural elements. They could then view the proposed repairs under the pressure that caused the original collapse.

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