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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Ground Based Microgravity Emissions Testing Of Flight Hardware

To control microgravity environment on the International Space Station (ISS), NASA developed payloads have to meet the payload integration requirements of the Space Station Program, specifically a microgravity allocation plan. The Microgravity Emissions Laboratory (MEL) was developed at NASA Glenn Research Center (GRC) for verification of the payloads compliance with payload integration requirements. MEL is a 6 degree of freedom inertial measurement system capable of characterizing the microgravity emissions, generated by a disturber, down to a micro g. Microgravity Emissions tests provide a payload developer with a tool to assess payload's compliance with the requirements, i.e. forces and moments, generated by the payload at its center of gravity. Forces and moments are presented in time domain for both stationary and transient signals, and in frequency domain for the stationary signals. To date, MEL conducted over thirty tests of ISS hardware. The test results are being successfully used by the payload developers for design verification and improvement.

Samorezov, Sergey↗
NASA NTRS2003

Light Microscopy Module Fan Disturbance Characterized Through Microgravity Emissions Laboratory Testing

A Light Microscopy Module (LMM) is being engineered, designed, and developed at the NASA Glenn Research Center. The LMM is planned as a remotely controllable on-orbit microscope subrack facility, allowing flexible scheduling and control of physical science and biological science experiments within Glenn s Fluids Integrated Rack on the International Space Station. The LMM concept is a modified commercial research imaging light microscope with powerful laser-diagnostic hardware and interfaces, creating a one-of-a-kind, state-of-the-art microscopic research facility. The microscope will house several different objectives, corresponding to magnifications of 10, 40, 50, 63, and 100. Features of the LMM include high-resolution color video microscopy, brightfield, darkfield, phase contrast, differential interference contrast, spectrophotometry, and confocal microscopy combined in a single configuration. Also, laser tweezers are integrated with the diagnostics as a sample manipulation technique. As part of the development phase of the LMM, it was necessary to quantify the microgravity disturbances generated by the control box fan. Isolating the fan was deemed necessary to reduce the fan speed harmonic amplitudes and to eliminate any broadband disturbances across the 60- to 70-Hz and 160- to 170-Hz frequency ranges. The accelerations generated by a control box fan component of the LMM were measured in the Microgravity Emissions Laboratory (MEL). The MEL is a low-frequency measurement system developed to simulate and verify the on-orbit International Space Station (ISS) microgravity environment. The accelerations generated by various operating components of the ISS, if too large, could hinder the science performed onboard by disturbing the microgravity environment. The MEL facility gives customers a test-verified way of measuring their compliance with ISS limitations on vibratory disturbance levels. The facility is unique in that inertial forces in 6 degrees of freedom can be characterized simultaneously for an operating test article. Vibratory disturbance levels are measured for engineering or flight-level hardware following development from component to subassembly through the rack-level configuration. The MEL can measure accelerations as small as 10-7g, the accuracy needed to confirm compliance with ISS requirements.

McNelis, Anne M.↗
NASA NTRS2005

Enhancements of Tow-Steering Design Techniques: Design of Rectangular Panel Under Combined Loads

An extension to existing design tools that utilize tow-steering is presented which is used to investigate the use of elastic tailoring for a flat panel with a central hole under combined loads of compression and shear. The elastic tailoring is characterized by tow-steering within individual lamina as well as a novel approach based on selective reinforcement, which attempts to minimize compliance through the use of Cellular Automata design concepts. The selective reinforcement designs lack any consideration of manufacturing constraints, so a new tow-steered path definition was developed to translate the prototype selective reinforcement designs into manufacturable plies. The minimum weight design of a flat panel under combined loading was based on a model provided by NASA-Langley personnel and analyzed by STAGS within the OLGA design environment. Baseline designs using traditional straight fiber plies were generated, as well as tow-steered designs which incorporated parallel, tow-drop, and overlap plies within the laminate. These results indicated that the overlap method provided the best improvement with regards to weight and performance as compared to traditional constant stiffness monocoque panels, though the laminates did not measure up to similar designs from the literature using sandwich and isogrid constructions. Further design studies were conducted using various numbers of the selective reinforcement plies at the core and outer surface of the laminate. None of these configurations exhibited notable advantages with regard to weight or buckling performance. This was due to the fact that the minimization of the compliance tended to direct the major stresses toward the center of the panel, which decreased the ability of the structure to withstand loads leading to instability.

Tatting, Brian F.↗
NASA NTRS2004

Materials and Processes for the New Millennium

The single greatest threat to material availability over the last decade has been Compliance to New Environmental Regulations. Federal Regulations: a) Clean Air Acts Amendments - 1990 - Titles I, III and VI; b) NASA Interim Policy- 1995 end date; c) Montreal Protocol - 2000 and 2005 end dates; d) Industrial Toxics Project - HAP emissions by 1995; e) Florida DER - VOC limits by 1995 (CA); f) OSHA Health Related Regulations 1) Carcinogens 2) Mutagens 3). Material availability is complicated by local and state regulations and their own compliance schedules.

Hayes, Paul W.↗
NASA NTRS1994

Adaptive Force Control in Compliant Motion

This paper addresses the problem of controlling a manipulator in compliant motion while in contact with an environment having an unknown stiffness. Two classes of solutions are discussed: adaptive admittance control and adaptive compliance control. In both admittance and compliance control schemes, compensator adaptation is used to ensure a stable and uniform system performance.

manipulators↗
NASA NTRS2006

Numerical Simulations and an Experimental Investigation of a Finger Seal

Besides sealing, the other main goal of a successful finger seal design is to exhibit appropriate compliance to outside forces. The ability of the seal to ride or float along the rotor without rubbing or excessive heating is essential to the successful operation of the seal. The compliance of the finger must only occur in the radial plane; The seal needs to be as sturdy as possible in the axial direction. The compliant finger that moves radially outward with rotor growth and motion has to be able to ride the rotor back down as the rotor diameter recovers or the rotor moves "away". Thus there is an optimum stiffness for the finger.

Braun, Minel↗
NASA NTRS2007

Boeing Crew Exploration Vehicle Environmental Control and Life Support System Architecture Overview

The Boeing Company under the teaming agreement with the Northrop Grumman Systems Corporation and in compliance with the NASA Phase 1 contract, had the responsibilities for the CEV architecture development of the Environmental control and life support (ECLS) system under the NASA Phase 1 contract. The ECLS system was comprised of the various subsystems which provided for a shirt-sleeve habitable environment for crew to live and work in the crew module of the CEV. This architecture met the NASA requirements to ferry cargo and crew to ISS, and Lunar sortie missions, with extensibility to long duration missions to Moon and MARS. This paper provides a summary overview of the CEV ECLS subsystems which was proposed in compliance with the contract activities.

Saiidi, Mo↗
NASA NTRS2001

Dual-mass vibratory rate gyroscope with suppressed translational acceleration response and quadrature-error correction capability

A microfabricated vibratory rate gyroscope to measure rotation includes two proof-masses mounted in a suspension system anchored to a substrate. The suspension has two principal modes of compliance, one of which is driven into oscillation. The driven oscillation combined with rotation of the substrate about an axis perpendicular to the substrate results in Coriolis acceleration along the other mode of compliance, the sense-mode. The sense-mode is designed to respond to Coriolis accelerationwhile suppressing the response to translational acceleration. This is accomplished using one or more rigid levers connecting the two proof-masses. The lever allows the proof-masses to move in opposite directions in response to Coriolis acceleration. The invention includes a means for canceling errors, termed quadrature error, due to imperfections in implementation of the sensor. Quadrature-error cancellation utilizes electrostatic forces to cancel out undesired sense-axis motion in phase with drive-mode position.

Clark, William A.↗
NASA NTRS2008

Prototype Flight Management Capabilities to Explore Temporal RNP Concepts

Next Generation Air Transportation System (NextGen) concepts of operation may require aircraft to fly planned trajectories in four dimensions three spatial dimensions and time. A prototype 4D flight management capability is being developed by NASA to facilitate the development of these concepts. New trajectory generation functions extend today's flight management system (FMS) capabilities that meet a single Required Time of Arrival (RTA) to trajectory solutions that comply with multiple RTA constraints. When a solution is not possible, a constraint management capability relaxes constraints to achieve a trajectory solution that meets the most important constraints as specified by candidate NextGen concepts. New flight guidance functions provide continuous guidance to the aircraft s flight control system to enable it to fly specified 4D trajectories. Guidance options developed for research investigations include a moving time window with varying tolerances that are a function of proximity to imposed constraints, and guidance that recalculates the aircraft s planned trajectory as a function of the estimation of current compliance. Compliance tolerances are related to required navigation performance (RNP) through the extension of existing RNP concepts for lateral containment. A conceptual temporal RNP implementation and prototype display symbology are proposed.

Ballin, Mark G.↗
NASA NTRS2006

International Space Station Acoustics

The International Space Station (ISS) presents a significant acoustics challenge considering all of the Modules and equipment that make it an on-orbit laboratory workshop and home with long-term crew occupation. This challenge is further complicated by the fact there are numerous and a wide variety suppliers of Station hardware, including International Partners. This paper addresses how ISS acoustics are managed to ensure a safe and habitable environment by establishing requirements, providing oversight and design support, sharing lessons learned and information, testing for hardware compliance, predicting future acoustic levels, and performing on-orbit measurement and monitoring of actual acoustic levels. ISS acoustic requirements are classified by the type of hardware involved, in three categories: Modules; payloads; and Government Furnished Equipment (GFE). Current status of overall ISS acoustics for each of these hardware categories will be discussed. In addition, the following items will be discussed: examples where NASA design support has been used to aid in obtaining compliance; difficulties encountered; and areas of concern.

Goodman, Jerry↗
NASA NTRS2008

Human Rating Requirements for NASA's Constellation Program

NASA s Constellation Program (CxP) will conduct a series of human space expeditions of increasing scope, starting with missions supporting the International Space Station and expanding to encompass the Moon and Mars. Although human-rating is an integral part of all CxP activities throughout their life cycle, NASA Procedural Requirements document NPR 8705.2B, Human-Rating Requirements (HRR) for Space Flight Systems, defines the additional processes, procedures, and requirements necessary to produce human-rated space systems that protect the safety of crew members and passengers on these NASA missions. In order to be in compliance with 8705.2B the CxP must show appropriate implementation or progression toward the HRR, or justification for an exception. Compliance includes an explanation of how the CxP intends to meet the HRR, analyses to be performed to determine implementation; and a matrix to trace the HRR to CxP requirements. The HRR requires the CxP to establish a human system integration team (HSIT), consisting of astronauts, mission operations personnel, training personnel, ground processing personnel, human factors personnel, and human engineering experts, with clearly defined authority, responsibility, and accountability to lead the human-system integration. For example, per the HRR the HSIT is involved in the evaluation of crew workload, human-in-the-loop usability evaluations, determining associated criteria, and in assessment of how these activities influenced system design. In essence, the HSIT is invaluable in CxP s ability to meet the three fundamental tenets of human rating: the process of designing, evaluating, and assuring that the total system can safely conduct the required human missions; the incorporation of design features and capabilities that accommodate human interaction with the system to enhance overall safety and mission success; and the incorporation of design features and capabilities to enable safe recovery of the crew from hazardous situations.

Berdich, Debbie↗
NASA NTRS2004

Managing Risk to Ensure a Successful Cassini/Huygens Saturn Orbit Insertion (SOI)

I. Design: a) S/C designed to be largely single fault tolerant; b) Operate in flight demonstrated envelope, with margin; and c) Strict compliance with requirements & flight rules. II. Test: a) Baseline, fault & stress testing using flight system testbeds (H/W & S/W); b) In-flight checkout & demos to remove first time events. III. Failure Analysis: a) Critical event driven fault tree analysis; b) Risk mitigation & development of contingencies. IV) Residual Risks: a) Accepted pre-launch waivers to Single Point Failures; b) Unavoidable risks (e.g. natural disaster). V) Mission Assurance: a) Strict process for characterization of variances (ISAs, PFRs & Waivers; b) Full time Mission Assurance Manager reports to Program Manager: 1) Independent assessment of compliance with institutional standards; 2) Oversight & risk assessment of ISAs, PFRs & Waivers etc.; and 3) Risk Management Process facilitator.

risk managment↗
NASA NTRS2009

Assessment of Composite Delamination Self-Healing Under Cyclic Loading

Recently, the promise of self-healing materials for enhanced autonomous durability has been introduced using a micro-encapsulation technique where a polymer based healing agent is encapsulated in thin walled spheres and embedded into a base polymer along with a catalyst phase. For this study, composite skin-stiffener flange debonding specimens were manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin-walled spheres. Constant amplitude fatigue tests in three-point bending showed the effect of self-healing on the fatigue response of the skin-stiffener flange coupons. After the cycling that created debonding, fatigue tests were held at the mean load for 24 hours. For roughly half the specimens tested, when the cyclic loading was resumed a decrease in compliance (increase in stiffness) was observed, indicating that some healing had occurred. However, with continued cycling, the specimen compliance eventually increased to the original level before the hold, indicating that the damage had returned to its original state. As was noted in a prevoius study conducted with specimens tested under monotonically increasing loads to failure, healing achieved via the micro-encapsulation technique may be limited to the volume of healing agent available relative to the crack volume.

O'Brien, T. Kevin↗
NASA NTRS2009

An Effective Health and Medical Technical Authority

The NASA Governance model directed the formation of three Technical Authorities, Engineering; Safety and Mission Assurance; and Health and Medical, to ensure that risks are identified and adjudicated efficiently and transparently in concert with the spaceflight programs and projects. The Health and Medical Technical Authority (HMTA) has been implemented at the Johnson Space Center (JSC) and consists of the Chief Medical Office (CMO), the Deputy CMO, and HMTA Delegates. The JSC HMTA achieves the goals of risk identification and adjudication through the discharge of the appropriate technical expertise to human space flight programs and projects and the escalation of issues within program and technical authority boards. The JSC HMTA relies on subject matter experts (SMEs) in the Space Life Sciences Directorate at JSC as well as experts from other Centers to work crew health and performance issues at the technical level, develop requirements, oversee implementation and validation of requirements, and identify risks and non-compliances. Once a risk or potential noncompliance has been identified and reported to the programs or projects, the JSC HMTA begins to track it and closely monitor the program's or project's response. As a risk is developed or a non-compliance negotiated, positions from various levels of decision makers are sought at the program and project control boards. The HMTA may support a program or project position if it is satisfied with the decision making and vetting processes (ex. the subject matter expert voiced his/her concerns and all dissenting opinions were documented) and finds that the position both acknowledges the risk and cost of the mitigation and resolves the issue without changing NASA risk posture. The HMTA may disagree with a program or project position if the NASA risk posture has been elevated or obfuscated. If the HMTA does disagree with the program or project position, it will appeal to successively higher levels of authority so that risk acceptance and risk trades will be acknowledged and sanctioned at the highest appropriate level; this includes Program Managers, Mission Directorate Associate Administrators and the Agency Administrator.

Fogarty, Jennifer A.↗
NASA NTRS2009

Shear Moduli for Non-Isotropic, Open Cell Foams Using a General Elongated Kelvin Foam Model

Equations for calculating the shear modulus of non-isotropic, open cell foams in the plane perpendicular to the rise direction and in a plane parallel to the rise direction are derived using an elongated Kelvin foam model. This Kelvin foam model is more general than that employed by previous authors as the size and shape of the unit cell are defined by specifying three independent cell dimensions. The equations for the shear compliances are derived as a function of three unit cell dimensions and the section properties of the cell edges. From the compliance equations, the shear modulus equations are obtained and written as a function of the relative density and two unit cell shape parameters. The dependence of the two shear moduli on the relative density and the two shape parameters is demonstrated.

Sullivan, Roy M.↗
NASA NTRS2010

Effects of Secondary Task Modality and Processing Code on Automation Trust and Utilization During Simulated Airline Luggage Screening

The purpose of this research was to examine the impact of environmental distractions on human trust and utilization of automation during the process of visual search. Participants performed a computer-simulated airline luggage screening task with the assistance of a 70% reliable automated decision aid (called DETECTOR) both with and without environmental distractions. The distraction was implemented as a secondary task in either a competing modality (visual) or non-competing modality (auditory). The secondary task processing code either competed with the luggage screening task (spatial code) or with the automation's textual directives (verbal code). We measured participants' system trust, perceived reliability of the system (when a target weapon was present and absent), compliance, reliance, and confidence when agreeing and disagreeing with the system under both distracted and undistracted conditions. Results revealed that system trust was lower in the visual-spatial and auditory-verbal conditions than in the visual-verbal and auditory-spatial conditions. Perceived reliability of the system (when the target was present) was significantly higher when the secondary task was visual rather than auditory. Compliance with the aid increased in all conditions except for the auditory-verbal condition, where it decreased. Similar to the pattern for trust, reliance on the automation was lower in the visual-spatial and auditory-verbal conditions than in the visual-verbal and auditory-spatial conditions. Confidence when agreeing with the system decreased with the addition of any kind of distraction; however, confidence when disagreeing increased with the addition of an auditory secondary task but decreased with the addition of a visual task. A model was developed to represent the research findings and demonstrate the relationship between secondary task modality, processing code, and automation use. Results suggest that the nature of environmental distractions influence interaction with automation via significant effects on trust and system utilization. These findings have implications for both automation design and operator training.

Phillips, Rachel↗
NASA NTRS2010

Back-Face Strain for Monitoring Stable Crack Extension in Precracked Flexure Specimens

Calibrations relating back-face strain to crack length in precracked flexure specimens were developed for different strain gage sizes. The functions were verified via experimental compliance measurements of notched and precracked ceramic beams. Good agreement between the functions and experiments occurred, and fracture toughness was calculated via several operational methods: maximum test load and optically measured precrack length; load at 2 percent crack extension and optical precrack length; maximum load and back-face strain crack length. All the methods gave vary comparable results. The initiation toughness, K(sub Ii) , was also estimated from the initial compliance and load.The results demonstrate that stability of precracked ceramics specimens tested in four-point flexure is a common occurrence, and that methods such as remotely-monitored load-point displacement are only adequate for detecting stable extension of relatively deep cracks.

Salem, Jonathan A.↗
NASA NTRS2011

International Space Station (ISS) Risk Reduction Activities

As the assembly of the ISS nears completion, it is worthwhile to step back and review some of the actions pursued by the Program in recent years to reduce risk and enhance the safety and health of ISS crewmembers, visitors, and space flight participants. While the ISS requirements and initial design were intended to provide the best practicable levels of safety, it is always possible to reduce risk -- given the determination and commitment to do so. The following is a summary of some of the steps taken by the ISS Program Manager, by our International Partners, by hardware and software designers, by operational specialists, and by safety personnel to continuously enhance the safety of the ISS. While decades of work went into developing the ISS requirements, there are many things in a Program like the ISS that can only be learned through actual operational experience. These risk reduction activities can be divided into roughly three categories: (1) Areas that were initially noncompliant which have subsequently been brought into compliance or near compliance (i.e., Micrometeoroid and Orbital Debris [MMOD] protection, acoustics) (2) Areas where initial design requirements were eventually considered inadequate and were subsequently augmented (i.e., Toxicity Level 4 materials, emergency hardware and procedures) (3) Areas where risks were initially underestimated, and have subsequently been addressed through additional mitigation (i.e., Extravehicular Activity [EVA] sharp edges, plasma shock hazards) Due to the hard work and cooperation of many parties working together across the span of nearly a decade, the ISS is now a safer and healthier environment for our crew, in many cases exceeding the risk reduction targets inherent in the intent of the original design. It will provide a safe and stable platform for utilization and discovery.

Fodroci, Michael↗