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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Fiber-Optic Bragg Gratings and Optical Holography Compared as Vibration Detectors

The NASA Glenn Research Center is interested in determining structural damage in engine components during flight to evaluate the health of aerospace propulsion systems. On the ground, we can use holography to detect structural damage by examining the characteristic mode shapes and frequencies of vibrating objects. We are studying the feasibility of using embedded fiber Bragg gratings (FBGs) to accomplish this goal in a flight-worthy system, by using the minimal intrusion and high sensitivity afforded by fiber optics. We have recently compared holographically imaged modes of vibrating plates with the corresponding dynamic strains detected by embedded FBGs. We constructed an experimental setup for studying the responses of FBGs to dynamic excitations. One of the plates was made of a polymer matrix composite (PMC) with an FBG embedded in it, and the other one was made of copper with surface-mounted FBGs. The instrumented plates were mounted and vibrated, and time-averaged holography was used to measure their surface displacements. Simultaneously, the signals from the FBGs were detected and sent via fiber-optic cable to a quiet location about 20 m away for interrogation. The the test configuration used for the PMC plate is shown. Experimental results are also shown. The FBG was embedded in the middle of the PMC plates, roughly within the center circular fringe in each of the interferograms shown. Two resonant excitation frequencies were used: 706 and 3062 Hz. The plot in this paper shows a larger FBG signal at the higher frequency; this is because the plate bends more at higher order resonant modes, causing higher strain. This contrasts to the smaller displacements characteristic of higher frequencies, which are measured by holographic techniques.

Adamovsky, Grigory↗
NASA NTRS1975

Design of an optical fiber cable link for lightning instrumentation

A lightning instrumentation system was designed to record current magnitudes of lightning strikes that hit a launch pad service structure at NASA's Kennedy Space Center. The instrumentation system consists of a lightning ground rod with a current sensor coil, an optical transmitter, an optical fiber cable link, a detector receiver, and a recording system. The transmitter is a wideband pulse transformer driving an IR LED emitter. The transmitter operates linearly as a transducer. A low loss fiber bundle provides isolation of the recorder system from the electromagnetic field of the lightning strike. The output of an optical detector receiver module is sampled and recorded in digital format. The significant factors considered in the design were dynamic range, linearity, mechanical configuration, electromagnetic isolation, and temperature compensation.

Grove, C. H.↗
NASA NTRS2014

Variable Acceleration Force Calibration System (VACS)

Conventionally, force balances have been calibrated manually, using a complex system of free hanging precision weights, bell cranks, and/or other mechanical components. Conventional methods may provide sufficient accuracy in some instances, but are often quite complex and labor-intensive, requiring three to four man-weeks to complete each full calibration. To ensure accuracy, gravity-based loading is typically utilized. However, this often causes difficulty when applying loads in three simultaneous, orthogonal axes. A complex system of levers, cranks, and cables must be used, introducing increased sources of systematic error, and significantly increasing the time and labor intensity required to complete the calibration. One aspect of the VACS is a method wherein the mass utilized for calibration is held constant, and the acceleration is changed to thereby generate relatively large forces with relatively small test masses. Multiple forces can be applied to a force balance without changing the test mass, and dynamic forces can be applied by rotation or oscillating acceleration. If rotational motion is utilized, a mass is rigidly attached to a force balance, and the mass is exposed to a rotational field. A large force can be applied by utilizing a large rotational velocity. A centrifuge or rotating table can be used to create the rotational field, and fixtures can be utilized to position the force balance. The acceleration may also be linear. For example, a table that moves linearly and accelerates in a sinusoidal manner may also be utilized. The test mass does not have to move in a path that is parallel to the ground, and no re-leveling is therefore required. Balance deflection corrections may be applied passively by monitoring the orientation of the force balance with a three-axis accelerometer package. Deflections are measured during each test run, and adjustments with respect to the true applied load can be made during the post-processing stage. This paper will present the development and testing of the VASC concept.

Rhew, Ray D.↗
NASA NTRS1976

Impact dynamics research facility for full-scale aircraft crash testing

An impact dynamics research facility (IDRF) was developed to crash test full-scale general aviation aircraft under free-flight test conditions. The aircraft are crashed into the impact surface as free bodies; a pendulum swing method is used to obtain desired flight paths and velocities. Flight paths up to -60 deg and aircraft velocities along the flight paths up to about 27.0 m/s can be obtained with a combination of swing-cable lengths and release heights made available by a large gantry. Seven twin engine, 2721-kg aircraft were successfully crash tested at the facility, and all systems functioned properly. Acquisition of data from signals generated by accelerometers on board the aircraft and from external and onboard camera coverage was successful in spite of the amount of damage which occurred during each crash. Test parameters at the IDRF are controllable with flight path angles accurate within 8 percent, aircraft velocity accurate within 6 percent, pitch angles accurate to 4.25 deg, and roll and yaw angles acceptable under wind velocities up to 4.5 m/s.

Vaughan, V. L. J.↗
NASA NTRS1963

Aeroelastic Tests of an Eight Percent Scale Saturn C-1 Block II

Buffet and flutter characteristics of Saturn Apollo mission were studied using a dynamically scaled model. The model was built around a central aluminum tube for scaled stiffness distribution and strength to resist loads imposed during testing. Styrofoam sections attached to the core provided the correct external contours. Lead weights were added for correct mass distribution. An electromagnetic shaker was used to excite the model in its flexible modes of vibration during portions of the test. The model was supported on a sting, mounted by leaf springs, cables and torsion bars. The support system provided for simulating the full scale rigid body pitch frequency with minimum restraint imposed on elastic deflections. Bending moments recorded by sensors on the aluminum tube. Several modified nose configurations were tested: The basic configuration was tested with and without a flow separator disk on the escape rocket motor, tests also were made with the escape tower and rocket motor removed completely. For the final test, the Apollo capsule was replaced with a Jupiter nose cone. The test program consisted of determining model response throughout the transonic speed range at angles of attack up to 6 degrees and measuring the aerodynamic damping over the same range for the basic model and the modified configurations. Signals from the model pickup were recorded on tape for later analysis. The data obtained were used to estimate bending moments that would be produced on the full-scale vehicle by aerodynamic forces due to buffeting.

EXPERIMENTS↗
NASA NTRS1991

Dynamic inter-limb resistance exercise device for long-duration space flight

Essential for fitness on Earth, resistive exercise is even more important for astronauts, who must maintain muscle and bone strength in the absence of gravity. To meet this need, designers and scientists at NASA Ames Research Center, Life Science Division, have worked to develop more effective exercise devices for long-duration exposure to microgravity. One of these concepts is the Inter-Limb Resistance Device which allows the subject to exercise one limb directly against another, strengthening muscle groups in the arms, legs, and back. It features a modular harness with an inelastic cable and instrumented pulley. Forces similar to other high resistance exercise equipment are generated. Sensors in the pulley measure force and velocity for performance feedback display and data acquisition. This free-floating apparatus avoids vibration of sensitive experiments on board spacecraft. Compact with low mass, this hardware is also well suited for a 'safe haven' from radiation on board Space Station Freedom, and may prove useful in confined environments on Earth, such as Antarctic stations, submarines, and other underwater habitats. Potential spin-offs of this technology include products for personal strengthening and cardiovascular conditioning, rehabilitation of hospital patients, fitness exercise for the disabled, and retraining after sports injuries.

Schwandt, Douglas F.↗
NASA NTRS1992

The trade-off characteristics of acoustic and pressure sensors for the NASP

Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty.

Winkler, Martin↗
NASA NTRS1992

Intelligent robots for planetary exploration and construction

Robots capable of practical applications in planetary exploration and construction will require realtime sensory-interactive goal-directed control systems. A reference model architecture based on the NIST Real-time Control System (RCS) for real-time intelligent control systems is suggested. RCS partitions the control problem into four basic elements: behavior generation (or task decomposition), world modeling, sensory processing, and value judgment. It clusters these elements into computational nodes that have responsibility for specific subsystems, and arranges these nodes in hierarchical layers such that each layer has characteristic functionality and timing. Planetary exploration robots should have mobility systems that can safely maneuver over rough surfaces at high speeds. Walking machines and wheeled vehicles with dynamic suspensions are candidates. The technology of sensing and sensory processing has progressed to the point where real-time autonomous path planning and obstacle avoidance behavior is feasible. Map-based navigation systems will support long-range mobility goals and plans. Planetary construction robots must have high strength-to-weight ratios for lifting and positioning tools and materials in six degrees-of-freedom over large working volumes. A new generation of cable-suspended Stewart platform devices and inflatable structures are suggested for lifting and positioning materials and structures, as well as for excavation, grading, and manipulating a variety of tools and construction machinery.

Albus, James S.↗
NASA NTRS1990

Cable delay compensator for microwave signal distribution over optical fibers

The basic principles of microwave fiber-optic systems are outlined with emphasis on fiber-optic cable delay compensators (CDC). Degradation of frequency and phase stability is considered, and it is pointed out that the long-term stability of a fiber-optic link is degraded by group delay variations due to temperature fluctuations in the optical fiber and low-frequency noise characteristics of the laser. A CDC employing a voltage-controlled oscillator to correct for phase variations in the optical fiber is presented, and the static as well as dynamic closed-loop analyses of the fiber-optic CDC are discussed. A constructed narrow-band fiber-optic CDC is shown to reduce phase variations caused by temperature fluctuations by a factor of 400. A wide-band CDC utilizing a temperature-controlled coil of fiber to compensate for phase delay is also proposed.

Primas, Lori E.↗
NASA NTRS2001

An Assessment of Helium Evolution from Helium-Saturated Propellant Depressurization in Space

Helium evolution from the transfer of helium-saturated propellant in space is quantified to assess its impacts from creating two-phase gas/liquid flow from the supply tank, gas injection into the receiving tank, and liquid discharge from the receiving tank. Propellant transfer takes place between two similar tanks whose maximum storage capacity is approximately 2.55 cubic meters each. The maximum on-orbit propellants transfer capability is 9000 lbm (fuel and oxidizer). The transfer line is approximately 1.27 cm in diameter and 6096 cm in length and comprised of the fluid interconnect system (FICS), the orbiter propellant transfer system (OPTS), and the International Space Station (ISS) propulsion module (ISSPM). The propellant transfer rate begins at approximately 11 liter per minute (lpm) and subsequently drops to approximately 0.5 lpm. The tank nominal operating pressure is approximately 1827 kPa (absolute). The line pressure drops for Monomethy1hydrazine (MMH) and Nitrogen tetroxide (NTO) at 11.3 lpm are approximately 202 kPa and 302 kPa, respectively. The pressure-drop results are based on a single-phase flow. The receiving tank is required to vent from approximately 1827 kPa to a lower pressure to affect propellant transfer. These pressure-drop scenarios cause the helium-saturated propellants to release excess helium. For tank ullage venting, the maximum volumes of helium evolved at tank pressure are approximately 0.5 ft3 for MMH and 2 ft3 for NTO. In microgravity environment, due to lack of body force, the helium evolution from a liquid body acts to propel it, which influences its fluid dynamics. For propellant transfer, the volume fractions of helium evolved at line pressure are 0.1% by volume for MMH and 0.6 % by volume for NTO at 11.3 lpm. The void fraction of helium evolved varies as an approximate second order power function of flow rate.

Nguyen, Bich N.↗
NASA NTRS1989

Computer network environment planning and analysis

The GSFC Computer Network Environment provides a broadband RF cable between campus buildings and ethernet spines in buildings for the interlinking of Local Area Networks (LANs). This system provides terminal and computer linkage among host and user systems thereby providing E-mail services, file exchange capability, and certain distributed computing opportunities. The Environment is designed to be transparent and supports multiple protocols. Networking at Goddard has a short history and has been under coordinated control of a Network Steering Committee for slightly more than two years; network growth has been rapid with more than 1500 nodes currently addressed and greater expansion expected. A new RF cable system with a different topology is being installed during summer 1989; consideration of a fiber optics system for the future will begin soon. Summmer study was directed toward Network Steering Committee operation and planning plus consideration of Center Network Environment analysis and modeling. Biweekly Steering Committee meetings were attended to learn the background of the network and the concerns of those managing it. Suggestions for historical data gathering have been made to support future planning and modeling. Data Systems Dynamic Simulator, a simulation package developed at NASA and maintained at GSFC was studied as a possible modeling tool for the network environment. A modeling concept based on a hierarchical model was hypothesized for further development. Such a model would allow input of newly updated parameters and would provide an estimation of the behavior of the network.

Dalphin, John F.↗
NASA NTRS2009

Findings from the Supersonic Qualification Program of the Mars Science Laboratory Parachute System

In 2012, the Mars Science Laboratory Mission (MSL) will deploy NASA's largest extra-terrestrial parachute, a technology integral to the safe landing of its advanced robotic explorer on the surface. The supersonic parachute system is a mortar deployed 21.5 m disk-gap-band (DGB) parachute, identical in geometric scaling to the Viking era DGB parachutes of the 1970's. The MSL parachute deployment conditions are Mach 2.3 at a dynamic pressure of 750 Pa. The Viking Balloon Launched Decelerator Test (BLDT) successfully demonstrated a maximum of 700 Pa at Mach 2.2 for a 16.1 m DGB parachute in its AV4 flight. All previous Mars deployments have derived their supersonic qualification from the Viking BLDT test series, preventing the need for full scale high altitude supersonic testing. The qualification programs for Mars Pathfinder, Mars Exploration Rover, and Phoenix Scout Missions were all limited to subsonic structural qualification, with supersonic performance and survivability bounded by the BLDT qualification. The MSL parachute, at the edge of the supersonic heritage deployment space and 33% larger than the Viking parachute, accepts a certain degree of risk without addressing the supersonic environment in which it will deploy. In addition, MSL will spend up to 10 seconds above Mach 1.5, an aerodynamic regime that is associated with a known parachute instability characterized by significant canopy projected area fluctuation and dynamic drag variation. This aerodynamic instability, referred to as "area oscillations" by the parachute community has drag performance, inflation stability, and structural implications, introducing risk to mission success if not quantified for the MSL parachute system. To minimize this risk and as an alternative to a prohibitively expensive high altitude test program, a multi-phase qualification program using computation simulation validated by subscale test was developed and implemented for MSL. The first phase consisted of 2% of fullscale supersonic wind tunnel testing of a rigid DGB parachute with entry-vehicle to validate two high fidelity computational fluid dynamics (CFD) tools. The computer codes utilized Large Eddy Simulation and Detached Eddy Simulation numerical approaches to accurately capture the turbulent wake of the entry vehicle and its coupling to the parachute bow-shock. The second phase was the development of fluid structure interaction (FSI) computational tools to predict parachute response to the supersonic flow field. The FSI development included the integration of the CFD from the first phase with a finite element structural model of the parachute membrane and cable elements. In this phase, a 4% of full-scale supersonic flexible parachute test program was conducted to provide validation data to the FSI code and an empirical dataset of the MSL parachute in a flight-like environment. The final phase is FSI simulations of the full-scale MSL parachute in a Mars type deployment. Findings from this program will be presented in terms of code development and validation, empirical findings from the supersonic testing, and drag performance during supersonic operation.

EDL↗
NASA NTRSDate not supplied

Countermeasures for Mitigation of Sensorimotor Decrements Following Head-Down Bed Rest

BACKGROUND Decrements in functional performance of tasks requiring postural and locomotor control remain common among crewmembers returning to Earth after6months on the International Space Station (ISS). These impairments will presumably be exacerbated after longer exploration-class missions with fewer exercise hardware options. Our recent studies suggest that an in-flight proprioceptive countermeasure may keep the proprioceptive system tuned to respond to upright balance challenges in a gravitational environment. Before testing a proprioceptive countermeasure in-flight, we must conduct an initial proof-of-concept study to determine its potential efficacy in a controlled unloading analog setting. OBJECTIVES We will determine if proprioceptive training during 60 days of 6° head down bed rest (HDBR) mitigates declines in functional task performance. We consider it critical to characterize the interaction between proprioceptive training and exercise. Thus, we will compare 3groupsof subjects(N=12 each): a proprioceptive training group, an exercise plus proprioceptive training group, and a control group(i.e. no training or exercise).The primary outcome measure will be the well-established and operationally relevant seat egress and walk test (also referred to as the functional mobility test)performed before and after HDBR. Other functional tests will also represent high priority exploration mission tasks that require high demand for dynamic control of postural stability. Additional measures will be used to identify the key physiological factors contributing to countermeasure benefits. COUNTERMEASURE METHODS We will use a ground version of our countermeasure to test the efficacy of proprioceptive training while maintaining HDBR constraints. Subjects will remain in the horizontal supine position on a sled that moves freely on air-bearings, similar to a puck on an air hockey table. Subjects will be loaded axially up to one full body weight via lateral cable pulleys towards their feet on an instrumented tilt board using a harness and weights system. Visual feedback of board tilt will be used to guide subjects while they make active tilts. Exercise and proprioceptive training prescriptions will represent those expected to be implemented during exploration spaceflight missions(e.g.20-minute proprioceptive training sessions3 times per week). RELEVANCE The deliverable from this project will be a proof-of-concept countermeasure design that has been fully assessed for efficacy in a spaceflight analog. The findings and lessons learned from this study will be translated for validation of this countermeasure on the ISS. An effective countermeasure will be added to the suite of operationally implemented in-flight sensorimotor countermeasures.

T R Macaulay↗
NASA NTRS2000

Ion Thruster Used to Propel the Deep Space 1 Spacecraft to Comet Encounters

The NASA Solar Electric Propulsion Technology Applications Readiness (NSTAR) Project provided a xenon ion propulsion system to the Deep Space 1 (DS1) spacecraft to validate the propulsion system as well as perform primary propulsion for asteroid and comet encounters. The On-Board Propulsion Branch of the NASA Glenn Research Center at Lewis Field developed engineering model versions of the 30-cm-diameter ion thruster and the 2.5-kW power processor unit (PPU). Glenn then transferred the thruster and PPU technologies to Hughes Electron Dynamics and managed the contract, which supplied two flight sets of thrusters and PPU s to the Deep Space 1 spacecraft and to a ground-based life verification test at the Jet Propulsion Laboratory (JPL). In addition to managing the DS1 spacecraft development, JPL was responsible for the NSTAR Project management, thruster life tests, the feed system, diagnostics, and propulsion subsystem integration. The ion propulsion development team included NASA Glenn, JPL, Hughes Electronics, Moog Inc., and Spectrum Astro Inc. The overall NSTAR subsystem dry mass, including thruster, PPU, controller, cables, and the xenon storage and feed system, is 48 kg. The mass of the xenon stored onboard DS1 was about 81 kg, and the spacecraft wet mass was approximately 500 kg.The DS1 spacecraft was launched on October 24, 1998, and on July 29, 1999, it flew within 16 miles of the small asteroid Braille (formerly 1992KD) at a relative speed of 35,000 mph. As of November 1999, the ion propulsion system had performed flawlessly for nearly 149 days of thrusting. NASA has approved an extension to the mission, which will allow DS1 to continue thrusting to encounters with two comets in 2001. The DS1 optical and plasma diagnostic instruments will be used to investigate the comet and space environments. The spacecraft is scheduled to fly past the dormant comet Wilson- Harrington in January 2001 and the very active comet Borrelly in September 2001, at which time approximately 500 days of ion engine thrusting will have been completed.

Sovey, James S.↗
NASA NTRS2002

Commercial-Off-The-Shelf Microelectromechanical Systems (MEMS) Flow-Measurement Probes Fabricated And Assembled

As an alternative to conventional tubing instrumentation for measuring airflow, designers and technicians at the NASA Glenn Research Center have been fabricating packaging components and assembling a set of unique probes using commercial-off-the-shelf microelectromechanical systems (MEMS) integrated circuits (computer chips). Using MEMS as an alternative has some compelling advantages over standard measurement devices. Sensor technologies have matured through high-production usage in industries such as automotive and aircraft manufacturers. Currently, MEMS are the choice in applications such as tire pressure monitors, altimeters, pneumatic controls, cable leak detectors, and consumer appliances. Conventional instrumentation uses tubing buried in the model aerodynamic surfaces or wind tunnel walls. The measurements are made when pressure is introduced at the tube opening. The pressure then must travel the tubing for lengths ranging from 20 to hundreds of feet before reaching an electronic signal conditioner. This condition causes a considerable amount of damping and requires measurements to be made only after the test rig has reached steady-state operation. The electronic MEMS pressure sensor is able to take readings continuously under dynamic states in nearly real time. The use of stainless steel tubing for pressure measurements requires many tubes to be cleaned, cut to length, carefully installed, and delicately deburred and spliced for use. A cluster of a few hundred 1/16-in.- (0.0625-in.-) diameter tubes (not uncommon in research testing facilities) can be several inches in diameter and may weigh enough to require two men to handle. Replacing hard tubing with electronic chips can eliminate much of the bulk. Each sensor would fit on the tip of the 1/16-in. tubing with room to spare. The P592 piezoresistive silicon pressure sensor (Lucas NovaSensor, Fremont, CA) was chosen for this project because of its cost, availability, and tolerance to extreme ambient conditions. The chip is 1 mm square by 0.6 mm thick (0.039 by 0.023 in.) with 0.12-mm (0.005-in.) wire connection tabs. Three MEMS chips were used to build the first type of flow-angularity probe. This MEMS probe will be demonstrated as an alternative to a standard tube type "Cobra Probe" now used routinely in wind tunnel and aeronautical hardware applications. The response time and accuracy would allow the probe to be translated on an actuator across a flow field, yielding precision dynamic measurements not possible with conventional instrumentation. The low profile, the minimal power requirement, the rugged construction, and the moderate cost all contribute to making MEMS sensors the enticing choice instrument in future research measurement needs. The MEMS probe efforts are a continuation of work initiated by Brian Willis, without whose foresight and efforts this project would never have been realized. This task was funded through cooperation with the NASA Electronic Parts and Packaging (NEPP) program at the Jet Propulsion Laboratory.

Redding, Chip↗
NASA NTRS2011

Orion Parachute Riser Cutter Development

This paper presents the tests and analytical approach used on the development of a steel riser cutter for the CEV Parachute Assembly System (CPAS) used on the Orion crew module. Figure 1 shows the riser cutter and the steel riser bundle which consists of six individual cables. Due to the highly compressed schedule, initial unavailability of the riser material and the Orion Forward Bay mechanical constraints, JSC primarily relied on a combination of internal ballistics analysis and LS-DYNA simulation for this project. Various one dimensional internal ballistics codes that use standard equation of state and conservation of energy have commonly used in the development of CAD devices for initial first order estimates and as an enhancement to the test program. While these codes are very accurate for propellant performance prediction, they usually lack a fully defined kinematic model for dynamic predictions. A simple piston device can easily and accurately be modeled using an equation of motion. However, the accuracy of analytical models is greatly reduced on more complicated devices with complex external loads, nonlinear trajectories or unique unlocking features. A 3D finite element model of CAD device with all critical features included can vastly improve the analytical ballistic predictions when it is used as a supplement to the ballistic code. During this project, LS-DYNA structural 3D model was used to predict the riser resisting load that was needed for the ballistic code. A Lagrangian model with eroding elements shown in Figure 2 was used for the blade, steel riser and the anvil. The riser material failure strain was fine tuned by matching the dent depth on the anvil with the actual test data. LS-DYNA model was also utilized to optimize the blade tip design for the most efficient cut. In parallel, the propellant type and the amount were determined by using CADPROG internal ballistics code. Initial test results showed a good match with LS-DYNA and CADPROG simulations. Final paper will present a detailed roadmap from initial ballistic modeling and LS-DYNA simulation to the performance testing. Blade shape optimization study will also be presented.

Oguz, Sirri↗
NASA NTRS1988

A 60-meter erectable assembly concept for a control of flexible structures flight experiment

A flight experiment which proposes to use a 60-m deployable/retractable truss beam attached to the Space Shuttle to study dynamic characterization and control of flexible structures is being studied by NASA. The concept requires a relatively complex mechanism for deploying and retracting the truss on-orbit. Development of such a mechanism having a high degree of reliability will be expensive. An alternative method for constructing the truss is discussed requiring no new technology development or complex mechanisms and has already been demonstrated on-orbit. The alternative method proposes an erectable truss beam which can be assembled by two astronauts in EVA. The EVA crew would have to manually assemble the beam from 468 struts and 165 nodes, and install 7 instrumentation platforms with signal and power cabling. The predicted assembly time is 3 hr and 23 min. The structure would also have to be disassembled and restowed following testing, thus 2 EVA days would be required. To allow 25 hr for data collection (probably a bare minimum to accomplish meaningful tests), current Shuttle operations policy dictates a 9-day mission. The design, assembly procedure and issues associated with the alternative concept are discussed.

Watson, Judith J.↗
NASA NTRS1998

Capillary-Driven Heat Transfer Experiment: Keeping It Cool in Space

Capillary-pumped loops (CPL's) are devices that are used to transport heat from one location to another--specifically to transfer heat away from something. In low-gravity applications, such as satellites (and possibly the International Space Station), CPL's are used to transfer heat from electrical devices to space radiators. This is accomplished by evaporating one liquid surface on the hot side of the CPL and condensing the vapor produced onto another liquid surface on the cold side. Capillary action, the phenomenon that causes paper towels to absorb spilled liquids, is used to "pump" the liquid back to the evaporating liquid surface (hot side) to complete the "loop." CPL's require no power to operate and can transfer heat over distances as large as 30 ft or more. Their reliance upon evaporation and condensation to transfer heat makes them much more economical in terms of weight than conventional heat transfer systems. Unfortunately, they have proven to be unreliable in space operations, and the explanation for this unreliability has been elusive. The Capillary-Driven Heat Transfer (CHT) experiment is investigating the fundamental fluid physics phenomena thought to be responsible for the failure of CPL's in low-gravity operations. If the failure mechanism can be identified, then appropriate design modifications can be developed to make capillary phase-change heat-transport devices a more viable option in space applications. CHT was conducted onboard the Space Shuttle Columbia during the first Microgravity Science Laboratory (MSL-1) mission, STS-94, which flew from July 1 to 17, 1997. The CHT glovebox investigation, which was conceived by Dr. Kevin Hallinan and Jeffrey Allen of the University of Dayton, focused on studying the dynamics associated with the heating and cooling at the evaporating meniscus within a capillary phase-change device in a low-gravity environment. The CHT experimental hardware was designed by a small team of engineers from Aerospace Design & Fabrication (ADF), the NASA Lewis Research Center, and the University of Dayton. The hardware consisted of two experiment modules that each contained an instrumented test loop (idealized capillary-pumped loop), a base unit for power conversion and backlighting, a display unit with 15 LED's (light-emitting diodes) to display temperatures, pressure, heater power, and time, a control unit to select heaters and heater settings, a cooling fan, and associated cables.

Lekan, Jack F.↗