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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Asymmetrical booster guidance and control system design study. Volume 3: Space shuttle vehicle SRB actuator failure study

The investigation of single actuator failures on the space shuttle solid rocket booster required the analysis of both square pattern and diamond pattern actuator configurations. It was determined that for failures occuring near or prior to the region of maximum dynamic pressure, control gain adjustments can be used to achieve virtually nominal mid-boost vehicle behavior. A distinct worst case failure condition was established near staging that could significantly delay staging. It is recommended that the square pattern be retained as a viable alternative to the baseline diamond pattern because the staging transient is better controlled resulting in earlier staging.

Williams, F. E.↗
NASA NTRS1973

A new criterion for failure of materials by environment-induced cracking

A new criterion has been developed for predicting failure of materials by environment-induced cracking. The criterion has been developed by the use of fracture mechanics concepts and assumes that the relationship between crack-growth rate and stress intensity can be described by three separable regions of behavior as first suggested by Wiederhorn. The analytical form of the criterion relates failure time to the initial crack length and the critical crack length or alternatively, to the initial stress intensity and the fracture toughness for various conditions of stress and the environmental variables. The analytical expression is examined by the use of some experimental data on the hydrogen-induced cracking of Ti-5Al-2.5 Sn, and it is demonstrated that the expression predicts the general expected form of the relationship between the normalized stress intensity parameter and the failure time.

Williams, D. P.↗
NASA NTRS1973

Failure detection and isolation of redundant inertial systems for Space Shuttle

A failure detection and isolation technique is presented for application to 'off-the-shelf' type four-gimbaled inertial measurement units (IMUs) such as the KT-70 or Carousel IV. This study concentrates initially upon actual four-gimbaled IMU performance requirements for current Space Shuttle booster and orbiter mission phases. When this information is obtained for a simplex system, the remaining area of study necessary to attain redundant IMU capabilities is the establishment of mission-dependent performance failure detection thresholds. These thresholds, then, permit a careful evaluation of the capabilities of various 'off-the-shelf' four gimbaled IMUs to satisfy the Shuttle mission performance requirements with various failure detection and isolation methods.

Brown, H. E.↗
NASA NTRS1975

Maximum likelihood failure detection techniques applied to the shuttle orbiter reaction control subsystem

A technique for on-board detection and identification of hard failures and leaks of the shuttle orbiter reaction control subsystem jets, during the orbital flight phase, is presented. The method uses gimbal angle and linear accelerometer measurements from the orbiter inertial measurement unit and requires no additional hardware. Extended Kalman filters with residual traps are employed for state estimation, and generalized likelihood ratio tests for jet failure identification. Rigid body simulation results indicate identification times of less than 2 seconds for hard jet failures and less than 70 seconds for jet leaks.

Deckert, J. C.↗
NASA NTRS1976

A study of Mariner 10 flight experiences and some flight piece part failure rate computations

The problems and failures encountered in Mariner flight are discussed and the data available through a quantitative accounting of all electronic piece parts on the spacecraft are summarized. It also shows computed failure rates for electronic piece parts. It is intended that these computed data be used in the continued updating of the failure rate base used for trade-off studies and predictions for future JPL space missions.

Paul, F. A.↗
NASA NTRS1976

Preliminary input to the space shuttle reaction control subsystem failure detection and identification software requirements (uncontrolled)

The current baseline method and software implementation of the space shuttle reaction control subsystem failure detection and identification (RCS FDI) system is presented. This algorithm is recommended for conclusion in the redundancy management (RM) module of the space shuttle guidance, navigation, and control system. Supporting software is presented, and recommended for inclusion in the system management (SM) and display and control (D&C) systems. RCS FDI uses data from sensors in the jets, in the manifold isolation valves, and in the RCS fuel and oxidizer storage tanks. A list of jet failures and fuel imbalance warnings is generated for use by the jet selection algorithm of the on-orbit and entry flight control systems, and to inform the crew and ground controllers of RCS failure status. Manifold isolation valve close commands are generated in the event of failed on or leaking jets to prevent loss of large quantities of RCS fuel.

Bergmann, E.↗
NASA NTRS1976

Failure rate analysis of Goddard Space Flight Center spacecraft performance during orbital life

Space life performance data on 57 Goddard Space Flight Center spacecraft are analyzed from the standpoint of determining an appropriate reliability model and the associated reliability parameters. Data from published NASA reports, which cover the space performance of GSFC spacecraft launched in the 1960-1970 decade, form the basis of the analyses. The results of the analyses show that the time distribution of 449 malfunctions, of which 248 were classified as failures (not necessarily catastrophic), follow a reliability growth pattern that can be described with either the Duane model or a Weibull distribution. The advantages of both mathematical models are used in order to: identify space failure rates, observe chronological trends, and compare failure rates with those experienced during the prelaunch environmental tests of the flight model spacecraft.

Norris, H. P.↗
NASA NTRS1976

Progressive failure of notched composite laminates using finite elements

An incremental, nonlinear, finite element program capable of tracing the damage that occurs in a notched laminated composite, before ultimate failure takes place, is described. Computer predictions for the ultimate failure load and failure modes are compared to experimental results for two laminates containing holes and loaded in uniaxial tension. The comparison is quite favorable.

Nuismer, R. J.↗
NASA NTRS1977

Failure detection by pilots during automatic landing - Models and experiments

A model is proposed to describe the pilot as a monitor of automatic landing systems. The failures treated are equivalent to the addition of a dynamic change in the mean of the observation process. The failure detection model of the pilot consists of two stages: a linear estimator (Kalman filter) and a decision mechanism based on sequential analysis. The filter equations are derived from a simplified version of the linearized dynamics of the airplane and the control loop. The perceptual observation noise is modified to include the effects of allocation of attention among the several instruments. The final result is a simple model consisting of a high-pass filter to produce the observation residuals and a decision function which is a pure integration of the residuals minus a bias term. The dynamics of a Boeing 707 were used to simulate the fully coupled final approach in a fixed-base simulator. Observers monitored the approaches and detected the failures; their performance was compared with the predictions of the model.

Gai, E. G.↗
NASA NTRS1979

Detecting servo failures with software

Program detects hardware failure in servosystems by comparing actual servo valve position with predictions of software model. In addition, system will also pick up most computer input/output failures. Process presents faster and more reliable results than previous failure detection methods.

Lew, D.↗
NASA NTRS1978

Precursors to failure in rocks while undergoing anelastic deformations

Specimens of pyrophyllite, which exhibits large anelastic deformation before brittle failure, were stressed to failure in a biaxial press to model stress accumulation prior to an earthquake. Optical holography, sound velocity measurements and photography through transparent pistons were used to study the specimens. A zone of preferential deformation around the incipient fault was monitored at 50% or more of ultimate failure strength; reversals of seismic velocities and formation of en echelon cracks near the coming macrocrack were also observed. The dependence of the seismic velocity reversals on moisture was noted.

Sobolev, G.↗
NASA NTRS1978

Progressive failure of structures

A procedure is presented for determining the nonlinear behavior of structures subjected to extreme loading and the possibility of development of potential for progressive failure. The methodology takes into account the effect of both material and geometric nonlinearities. At a given stage of analysis, the individual components of the structure are checked against predetermined failure criteria. Subsequently, the failing components are removed and the modified structure is analyzed for overall failure. Examples, obtained from a computer program based on the proposed procedure, showing the applicability of the method are presented.

Khozeimeh, K.↗
NASA NTRS1979

Failure of underground concrete structures subjected to blast loadings

The response and failure of two edges of free reinforced concrete slabs subjected to intermediate blast loadings are examined. The failure of the reinforced concrete structures is defined as a condition where actual separation or fracture of the reinforcing elements has occurred. Approximate theoretical methods using stationary and moving plastic hinge mechanisms with linearly varying and time dependent loadings are developed. Equations developed to predict deflection and failure of reinforced concrete beams are presented and compared with the experimental results.

Ross, C. A.↗
NASA NTRS1980

Development of failure model for nickel cadmium cells

The development of a method for the life prediction of nickel cadmium cells is discussed. The approach described involves acquiring an understanding of the mechanisms of degradation and failure and at the same time developing nondestructive evaluation techniques for the nickel cadmium cells. The development of a statistical failure model which will describe the mechanisms of degradation and failure is outlined.

Gupta, A.↗
NASA NTRS1979

Mod 1 wind turbine generator failure modes and effects analysis

A failure modes and effects analysis (FMEA) was directed primarily at identifying those critical failure modes that would be hazardous to life or would result in major damage to the system. Each subsystem was approached from the top down, and broken down to successive lower levels where it appeared that the criticality of the failure mode warranted more detail analysis. The results were reviewed by specialists from outside the Mod 1 program, and corrective action taken wherever recommended.

Source record↗
NASA NTRS1979

Nonlinear temperature dependent failure analysis of finite width composite laminates

A quasi-three dimensional, nonlinear elastic finite element stress analysis of finite width composite laminates including curing stresses is presented. Cross-ply, angle-ply, and two quasi-isotropic graphite/epoxy laminates are studied. Curing stresses are calculated using temperature dependent elastic properties that are input as percent retention curves, and stresses due to mechanical loading in the form of an axial strain are calculated using tangent modulii obtained by Ramberg-Osgood parameters. It is shown that curing stresses and stresses due to tensile loading are significant as edge effects in all types of laminate studies. The tensor polynomial failure criterion is used to predict the initiation of failure. The mode of failure is predicted by examining individual stress contributions to the tensor polynomial.

Nagarkar, A. P.↗
NASA NTRS1980

NASTRAN analysis of heat-transfer fluid fill pipe failure

An example that shows the difficulties of failure analyses and the advantage of the finite element method (NASTRAN) in assisting in determining the true cause of a failure is presented. In this example, cracks were developing along a pipe weld. After discarding several possible causes for the failures, it was finally determined that the problem was due to stress corrosion cracking associated with a rather unusual and novel environmental condition.

Winter, J. R.↗