Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “recovery”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Recovery of precious metals in space

This program is proceeding along the lines compatible with the objective of developing feasible separation and recovery processes for precious metals in a space environment. Efficient, compact, solvent extraction systems (both single and multistage) capable of high selectivity and rapid equilibration that are based on chelate and ion pair complexes are being explored. Two research projects were undertaken: (1) study of the time-dependent aspects of the formation of Pd(2) extractable chelate complexes; and (2) development of a multistage countercurrent distribution process for the separation and recovery of Pd(2) and Pt(2) ions.

Freiser, H.↗
NASA NTRS1990

The effect of swirl recovery vanes on the cruise noise of an advanced propeller

The SR-7A propeller was acoustically tested with and without downstream swirl recovery vanes to determine if any extra noise was caused by the interaction of the propeller wakes and vortices with these vanes. No additional noise was observed at the cruise condition over the angular range tested. The presence of the swirl recovery vanes did unload the propeller and some small peak noise reductions were observed from lower propeller loading noise. The propeller was also tested alone to investigate the behavior of the peak propeller noise with helical tip Mach number. As observed before on other propellers, the peak noise first rose with helical tip Mach number and then leveled off or decreased at higher helical tip Mach numbers. Detailed pressure-time histories indicate that a portion of the primary pressure pulse is progressively cancelled by a secondary pulse as the helical tip Mach number is increased. This cancellation appears to be responsible for the peak noise behavior at high helical tip Mach numbers.

Dittmar, James H.↗
NASA NTRS1990

A representation for error detection and recovery in robot task plans

A general definition is given of the problem of error detection and recovery in robot assembly systems, and a general representation is developed for dealing with the problem. This invariant representation involves a monitoring process which is concurrent, with one monitor per task plan. A plan hierarchy is discussed, showing how diagnosis and recovery can be handled using the representation.

Lyons, D. M.↗
NASA NTRS1991

Liquid booster engine reuse - A recovery system

The paper presents the design of a recovery system for a suborbital payload of an Atlas E rocket. This program utilizes off-the-shelf and previously qualified avionics, flotation, and decelerator systems. A brief history of liquid-engine recoveries is presented first, then the system design utilizing two self-contained structurally-identical pods diametrically mounted to the thrust section is outlined. A mortar-deployed drogue and the main parachute are described, and experimental procedures are considered. Data obtained from one tricluster drop employing a cylindrical test vehicle and helicopter is analyzed, and a satisfactory load balance between the parachutes is observed.

Von Eckroth, Wulf↗
NASA NTRS1991

Closed-loop transfer recovery with observer-based controllers. I - Analysis

The description of a novel problem in loop transfer recovery is presented. The problem of closed-loop recovery (CLTR) is examined using a measurement feedback-control law where the closed-loop transfer function from the external signal to the controlled output can be made either exactly equal or approximately close to the so-called target closed-loop transfer function achieved under full-state feedback. The analysis of CLTR applies specifically to the general class of observer-based controllers and focuses on three fundamental issues. The first issue is concerned with what can and cannot be achieved for a given system and for an arbitrary target closed-loop transfer function. The second issue is to develop necessary and/or sufficient conditions for a target closed-loop transfer function to be recoverable either exactly or approximately. The third issue deals with the necessary and/or sufficient conditions on a given system such that it has at least one recoverable target closed-loop transfer function. The result is applied to the lateral autopilot design for a commercial transport airplane.

Chen, Ben M.↗
NASA NTRS1992

Microbial biofilm studies of the environmental control and life support system water recovery test for Space Station Freedom

NASA is developing a water recovery system (WRS) for Space Station Freedom to reclaim human waste water for reuse by astronauts as hygiene or potable water. A water recovery test (WRT) currently in progress investigates the performance of a prototype of the WRS. Analysis of biofilm accumulation, the potential for microbially influenced corrosion (MIC) in the WRT, and studies of iodine disinfection of biofilm are reported. Analysis of WRT components indicated the presence of organic deposits and biofilms in selected tubing. Water samples for the WRT contained acid-producing and sulfate-reducing organisms implicated in corrosion processes. Corrosion of an aluminum alloy was accelerated in the presence of these water samples; however, stainless steel corrosion rates were not accelerated. Biofilm iodine sensitivity tests using an experimental laboratory scale recycled water system containing a microbial check valve (MCV) demonstrated that an iodine concentration of 1 to 2 mg/L was ineffective in eliminating microbial biofilm. For complete disinfection, an initial concentration of 16 mg/L was required, which was gradually reduced by the MCV over 4 to 8 hours to 1 to 2 mg/L. This treatment may be useful in controlling biofilm formation.

Rodgers, E. B.↗
NASA NTRS1991

Space Station Freedom regenerative water recovery system configuration selection

The Space Station Freedom (SSF) must recover water from various waste water sources to reduce 90 day water resupply demands for a four/eight person crew. The water recovery system options considered are summarized together with system configuration merits and demerits, resource advantages and disadvantages, and water quality considerations used to select the SSF water recovery system.

Reysa, R.↗
NASA NTRS1990

Zero assignment and loop transfer recovery in LQG design

The problem of loop transfer recovery (LTR) in linear quadratic Gaussian (LQG) design via observers is discussed. The LTR for both minimum and nonminimum phase systems is considered. For minimum phase systems, perfect recovery approaches are provided based on Luenberger proportional observer and proportional integral observer. For nonminimum phase systems, recent LTR approaches are summarized and the possibility of a new technique based on zero assignment is examined.

Shafai, B.↗
NASA NTRS1991

Memory management and compiler support for rapid recovery from failures in computer systems

This paper describes recent developments in the use of memory management and compiler technology to support rapid recovery from failures in computer systems. The techniques described include cache coherence protocols for user transparent checkpointing in multiprocessor systems, compiler-based checkpoint placement, compiler-based code modification for multiple instruction retry, and forward recovery in distributed systems utilizing optimistic execution.

Fuchs, W. K.↗
NASA NTRS1991

Bioregenerative technologies for waste processing and resource recovery in advanced space life support system

The Controlled Ecological Life Support System (CELSS) for producing oxygen, water, and food in space will require an interactive facility to process and return wastes as resources to the system. This paper examines the bioregenerative techologies for waste processing and resource recovery considered for a CELSS Resource Recovery system. The components of this system consist of a series of biological reactors to treat the liquid and solid material fractions, in which the aerobic and anaerobic reactors are combined in a block called the Combined Reactor Equipment (CORE) block. The CORE block accepts the human wastes, kitchen wastes, inedible refractory plant materials, grey waters from the CELLS system, and aquaculture solids and processes these materials in either aerobic or anaerobic reactors depending on the desired product and the rates required by the integrated system.

Chamberland, Dennis↗
NASA NTRS1991

Failure recovery control for space robotic systems

The problem of controlling a failed joint of a space manipulator is addressed. It is shown that failure-recovery control is possible when dynamic coupling exists between the link whose joint has failed and some other link whose joint is working and when the system inertia matrix is invariant with respect to the failed joint angle. A failure-recovery control technique is developed and applied to two simple examples.

Papadopoulos, Evangelos↗
NASA NTRS1992

Preosteoblast production in Cosmos 2044 rats - Short-term recovery of osteogenic potential

The influence of a 13.8-day spaceflight and about 8.5-11 h of recovery at 1 g on fibro blastlike osteoblast precursor cells was assessed in the periodontal ligament of rat maxillary first molars. Preosteoblasts (C + D cells), less differentiated progenitor cells (A + A prime cells), and nonosteogenic fibroblastlike cells (B cells) were identified by nuclear volume analysis. No differences were observed among flight, synchronous vivarium, and basal control groups in the A + A prime or C + D cell compartments. Compared with previous spaceflight experiments, the present data are consistent with a postflight response to replinish preosteoblasts and restore periodontal ligament osteogenic potential. These data emphasize the need to unequivocally determine the flight effect by killing the animals in-flight and further assess the postflight recovery phenomenon.

Garetto, Lawrence P.↗
NASA NTRS1990

Microbiological methods for the water recovery systems test, revision 1.1

Current microbiological parameters specified to verify microbiological quality of Space Station Freedom water quality include the enumeration of total bacteria, anaerobes, aerobes, yeasts and molds, enteric bacteria, gram positives, gram negatives, and E. coli. In addition, other parameters have been identified as necessary to support the Water Recovery Test activities to be conducted at the NASA/MSFC later this year. These other parameters include aerotolerant eutrophic mesophiles, legionellae, and an additional method for heterotrophic bacteria. If inter-laboratory data are to be compared to evaluate quality, analytical methods must be eliminated as a variable. Therefore, each participating laboratory must utilize the same analytical methods and procedures. Without this standardization, data can be neither compared nor validated between laboratories. Multiple laboratory participation represents a conservative approach to insure quality and completeness of data. Invariably, sample loss will occur in transport and analyses. Natural variance is a reality on any test of this magnitude and is further enhanced because biological entities, capable of growth and death, are specific parameters of interest. The large variation due to the participation of human test subjects has been noted with previous testing. The resultant data might be dismissed as 'out of control' unless intra-laboratory control is included as part of the method or if participating laboratories are not available for verification. The purpose of this document is to provide standardized laboratory procedures for the enumeration of certain microorganisms in water and wastewater specific to the water recovery systems test. The document consists of ten separate cultural methods and one direct count procedure. It is not intended nor is it implied to be a complete microbiological methods manual.

Rhoads, Tim↗
NASA NTRS1993

Compiler-Assisted Multiple Instruction Rollback Recovery Using a Read Buffer

Multiple instruction rollback (MIR) is a technique to provide rapid recovery from transient processor failures and was implemented in hardware by researchers and slow in mainframe computers. Hardware-based MIR designs eliminate rollback data hazards by providing data redundancy implemented in hardware. Compiler-based MIR designs were also developed which remove rollback data hazards directly with data flow manipulations, thus eliminating the need for most data redundancy hardware. Compiler-assisted techniques to achieve multiple instruction rollback recovery are addressed. It is observed that data some hazards resulting from instruction rollback can be resolved more efficiently by providing hardware redundancy while others are resolved more efficiently with compiler transformations. A compiler-assisted multiple instruction rollback scheme is developed which combines hardware-implemented data redundancy with compiler-driven hazard removal transformations. Experimental performance evaluations were conducted which indicate improved efficiency over previous hardware-based and compiler-based schemes. Various enhancements to the compiler transformations and to the data redundancy hardware developed for the compiler-assisted MIR scheme are described and evaluated. The final topic deals with the application of compiler-assisted MIR techniques to aid in exception repair and branch repair in a speculative execution architecture.

Alewine, Neal Jon↗
NASA NTRS1993

Compiler-assisted multiple instruction rollback recovery using a read buffer

Multiple instruction rollback (MIR) is a technique that has been implemented in mainframe computers to provide rapid recovery from transient processor failures. Hardware-based MIR designs eliminate rollback data hazards by providing data redundancy implemented in hardware. Compiler-based MIR designs have also been developed which remove rollback data hazards directly with data-flow transformations. This paper focuses on compiler-assisted techniques to achieve multiple instruction rollback recovery. We observe that some data hazards resulting from instruction rollback can be resolved efficiently by providing an operand read buffer while others are resolved more efficiently with compiler transformations. A compiler-assisted multiple instruction rollback scheme is developed which combines hardware-implemented data redundancy with compiler-driven hazard removal transformations. Experimental performance evaluations indicate improved efficiency over previous hardware-based and compiler-based schemes.

Alewine, N. J.↗
NASA NTRS1993

Process control and recovery in the Link Monitor and Control Operator Assistant

This paper describes our approach to providing process control and recovery functions in the Link Monitor and Control Operator Assistant (LMCOA). The focus of the LMCOA is to provide semi-automated monitor and control to support station operations in the Deep Space Network. The LMCOA will be demonstrated with precalibration operations for Very Long Baseline Interferometry on a 70-meter antenna. Precalibration, the task of setting up the equipment to support a communications link with a spacecraft, is a manual, time consuming and error-prone process. One problem with the current system is that it does not provide explicit feedback about the effects of control actions. The LMCOA uses a Temporal Dependency Network (TDN) to represent an end-to-end sequence of operational procedures and a Situation Manager (SM) module to provide process control, diagnosis, and recovery functions. The TDN is a directed network representing precedence, parallelism, precondition, and postcondition constraints. The SM maintains an internal model of the expected and actual states of the subsystems in order to determine if each control action executed successfully and to provide feedback to the user. The LMCOA is implemented on a NeXT workstation using Objective C, Interface Builder and the C Language Integrated Production System.

Lee, Lorrine↗
NASA NTRS1993

Application of compiler-assisted multiple instruction rollback recovery to speculative execution

Speculative execution is a method to increase instruction level parallelism which can be exploited by both super-scalar and VLIW architectures. The key to a successful general speculation strategy is a repair mechanism to handle mispredicted branches and accurate reporting of exceptions for speculated instructions. Multiple instruction rollback is a technique developed for recovery from transient processor failure. Many of the difficulties encountered during recovery from branch misprediction or from instruction re-execution due to exception in a speculative execution architecture are similar to those encountered during multiple instruction rollback. The applicability of a recently developed compiler-assisted multiple instruction rollback scheme to aid in speculative execution repair is investigated. Extensions to the compiler-assisted scheme to support branch and exception repair are presented along with performance measurements across ten application programs.

Alewine, N. J.↗