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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Measurement of very small phase fluctuations by means of the operational approach

Recently Noh, Fourgeres and Mandel (NFM) have improved the operational approach to the quantum phase problem substantially and measured the phase dispersion of coherent light down to very small means photon numbers of the order of 10(exp -2). This has prompted many other investigations and clarified some important questions in relation to what is actually measured. Although their treatment is rather general, we confine ourselves here to the case of a strong local oscillator (LO) and reproduce their measurement scheme. Surprisingly enough, this simultaneous measurement of the sine and the cosine of the phase difference is completely equivalent to an old proposal to measure the phase after strong linear amplification realized experimentally by the Welling group. The reason for this rests on the fact, that in both cases the results are determined by the Q function of the signal. This was shown for amplification in and for the measurement after beam splitting by Lai and Haus.

Bandilla, Arno↗
NASA NTRS1985

Other Challenges in the Development of the Orbiter Environmental Control Hardware

Development of the Space Shuttle orbiter environmental control and life support system (ECLSS) included the identification and resolution of several interesting problems in several systems. Some of these problems occurred late in the program, including the flight phase. Problems and solutions related to the ammonia boiler system (ABS), smoke detector, water/hydrogen separator, and waste collector system (WCS) are addressed.

Gibb, J. W.↗
NASA NTRS1987

The LQR/LTR procedure for multivariable feedback control design

This paper provides a tutorial overview of the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) design procedure for linear multivariable feedback systems. LQR/LTR is interpreted as the solution of a specific weighted H-squared tradeoff between transfer functions in the frequency domain. Properties of this solution are examined for both minimum-phase and nonminimum-phase systems. This leads to a formal weight augmentation procedure for the minimum-phase case which permits essentially arbitrary specification of system sensitivity functions in terms of the weights. While such arbitrary specifications are not possible for nonminimum-phase problems, a direct relationship between weights and sensitivities is developed for nonminimum-phase SISO and certain nonminimum-phase MIMO cases which guides the weight selection process.

Stein, Gunter↗
NASA NTRS1972

Two Phase Detonation Studies Conducted in 1971

The research covered by this third annual progress report represents a continuation of our efforts devoted to the study of detonation waves in liquid-gas systems. The motivation for the work is associated with liquid propellant rocket motor combustion instability although certainly the studies are also applicable to internal combustion engines, jet propulsion engines, safety aspects of spilled liquid fuel, coal mine explosions, and weaponry. The research has been divided into 5 phases, although all of them are intimately related. For the most part these phases are briefly summarized and the reader is referred to other publications for a more complete treatment. The exception to this is where the material herein represents the only printed information available on the particular facet of the problem. Phase A has been primarily concerned with the breakup and ignition of fuel drops by shock waves. The experimental portion of this study as well as a theoretical treatment of the ignition behavior was completed in the past year. The research is now concentrating on the passage of a shock wave over a burning drop. Phase B has been devoted to the assessment of the approximate energy release pattern in two phase detonations insofar as they affect the significant overpressures observed.

Nicholls, J. A.↗
NASA NTRS2012

Low-Cost Phased Array Antenna for Sounding Rockets, Missiles, and Expendable Launch Vehicles

A low-cost beamformer phased array antenna has been developed for expendable launch vehicles, rockets, and missiles. It utilizes a conformal array antenna of ring or individual radiators (design varies depending on application) that is designed to be fed by the recently developed hybrid electrical/mechanical (vendor-supplied) phased array beamformer. The combination of these new array antennas and the hybrid beamformer results in a conformal phased array antenna that has significantly higher gain than traditional omni antennas, and costs an order of magnitude or more less than traditional phased array designs. Existing omnidirectional antennas for sounding rockets, missiles, and expendable launch vehicles (ELVs) do not have sufficient gain to support the required communication data rates via the space network. Missiles and smaller ELVs are often stabilized in flight by a fast (i.e. 4 Hz) roll rate. This fast roll rate, combined with vehicle attitude changes, greatly increases the complexity of the high-gain antenna beam-tracking problem. Phased arrays for larger ELVs with roll control are prohibitively expensive. Prior techniques involved a traditional fully electronic phased array solution, combined with highly complex and very fast inertial measurement unit phased array beamformers. The functional operation of this phased array is substantially different from traditional phased arrays in that it uses a hybrid electrical/mechanical beamformer that creates the relative time delays for steering the antenna beam via a small physical movement of variable delay lines. This movement is controlled via an innovative antenna control unit that accesses an internal measurement unit for vehicle attitude information, computes a beam-pointing angle to the target, then points the beam via a stepper motor controller. The stepper motor on the beamformer controls the beamformer variable delay lines that apply the appropriate time delays to the individual array elements to properly steer the beam. The array of phased ring radiators is unique in that it provides improved gain for a small rocket or missile that uses spin stabilization for stability. The antenna pattern created is symmetric about the roll axis (like an omnidirectional wraparound), and is thus capable of providing continuous coverage that is compatible with very fast spinning rockets. For larger ELVs with roll control, a linear array of elements can be used for the 1D scanned beamformer and phased array, or a 2D scanned beamformer can be used with an NxN element array.

Mullinix, Daniel↗
NASA NTRS1974

Automation of the aircraft design process

The increasing use of the computer to automate the aerospace product development and engineering process is examined with emphasis on structural analysis and design. Examples of systems of computer programs in aerospace and other industries are reviewed and related to the characteristics of aircraft design in its conceptual, preliminary, and detailed phases. Problems with current procedures are identified, and potential improvements from optimum utilization of integrated disciplinary computer programs by a man/computer team are indicated.

Heldenfels, R. R.↗
NASA NTRS1979

Satellite communications for disaster relief operations

The use of communication satellite systems to provide assistance in disaster relief operations on a global basis is presented. Disaster problem phases such as detection, warning, and relief; requirements for the communication capability including remote data collection, imaging and voice broadcast; and the global disaster network are discussed. Utilization of Intelsat and Marisat systems and the size and type of ground terminals required for satellite access is considered, and estimates of communication requirements for a global system and of costs for satellite services to support relief operations are given. NASA disaster related activities including studies of direct-to-home disaster warning and determination of disaster response times are described, and it is concluded that existing international satellite communication systems offer real potential for the establishment of a reliable and flexible network devoted to disaster related communication services.

Sivo, J. N.↗
NASA NTRS1993

Array Simulations Platform (ASP) predicts NASA Data Link Module (NDLM) performance

Through a variety of imbedded theoretical and actual antenna patterns, the array simulation platform (ASP) enhanced analysis of the array antenna pattern effects for the KTx (Ku-Band Transmit) service of the NDLM (NASA Data Link Module). The ASP utilizes internally stored models of the NDLM antennas and can develop the overall pattern of antenna arrays through common array calculation techniques. ASP expertly assisted in the diagnosing of element phase shifter errors during KTx testing and was able to accurately predict the overall array pattern from combinations of the four internally held element patterns. This paper provides an overview of the use of the ASP software in the solving of array mis-phasing problems.

Snook, Allen David↗
NASA NTRS2018

Area Coverage Planning with 3-axis Steerable, 2D Framing Sensors

Existing algorithms for Agile Earth Observing Satellites((Lemaitre et al. 2002)) were largely created for 1D line sensors that acquire images in linear swaths. However, imaging satellites increasingly use 2D framing sensors (cameras) that capture discrete rectangular images. We describe tiling step-stare approaches that are more suited to rectangular image footprints than are 1D swath-based algorithms. Optimal area planning for these 2D framing instruments is an NPcomplete problem and intractable for large areas, so we present four approximation algorithms. Strategies are compared against a prior 2D framing instrument algorithm (Knight 2014) in three computational experiments. The impact of observer agility on schedule makespan is examined. Makespans vary more as observer agility decreases toward a critical point, then vary less after the critical point, suggesting a possible problem phase transition.

Chien, Steve↗
NASA NTRS2019

Europa Lander trajectory design: case studies for the direct-to-earth architecture

This paper presents interesting phasing problems that came up in support of design studies for a potential Europa Lander mission. Recent system trades were performed after the Mission Concept Review in fall 2017, when the NASA board recommended the Europa Lander project design a Direct-to-Earth architecture, i.e. where the Lander would communicate directly to the Earth, without data relay from the carrier vehicle.

Landau, Damon↗
NASA NTRSDate not supplied

Development Efforts and Status of Plume-Surface Interaction Capabilities for Propulsive Landing Systems

Rocket plume-surface interaction is a multi-phase problem characterized by plume flow physics, erosion physics, and ejecta dynamics. All propulsive landers will experience plume-surface interaction. The risks posed by such effects can vary greatly as a function of the local environment, lander concept of operations, configuration, and physical scale. Prior Lunar and Martian landers have overcome challenges posed by these environments, on the basis of scaled ground testing and subsequent flight experience, but the landing systems for present and future missions are planning to operate increasingly outside of NASA's current experience with plume-surface interaction. This presentation discusses the current efforts and status of activities within NASA to progress understanding of fundamental plume-surface interaction physics, the capability to predict resulting environments and effects, and the definition of implications for current and future Lunar and planetary landing systems.

Landing↗
NASA NTRS2014

Phase Transitions in Planning Problems: Design and Analysis of Parameterized Families of Hard Planning Problems

There are two common ways to evaluate algorithms: performance on benchmark problems derived from real applications and analysis of performance on parametrized families of problems. The two approaches complement each other, each having its advantages and disadvantages. The planning community has concentrated on the first approach, with few ways of generating parametrized families of hard problems known prior to this work. Our group's main interest is in comparing approaches to solving planning problems using a novel type of computational device - a quantum annealer - to existing state-of-the-art planning algorithms. Because only small-scale quantum annealers are available, we must compare on small problem sizes. Small problems are primarily useful for comparison only if they are instances of parametrized families of problems for which scaling analysis can be done. In this technical report, we discuss our approach to the generation of hard planning problems from classes of well-studied NP-complete problems that map naturally to planning problems or to aspects of planning problems that many practical planning problems share. These problem classes exhibit a phase transition between easy-to-solve and easy-to-show-unsolvable planning problems. The parametrized families of hard planning problems lie at the phase transition. The exponential scaling of hardness with problem size is apparent in these families even at very small problem sizes, thus enabling us to characterize even very small problems as hard. The families we developed will prove generally useful to the planning community in analyzing the performance of planning algorithms, providing a complementary approach to existing evaluation methods. We illustrate the hardness of these problems and their scaling with results on four state-of-the-art planners, observing significant differences between these planners on these problem families. Finally, we describe two general, and quite different, mappings of planning problems to QUBOs, the form of input required for a quantum annealing machine such as the D-Wave II.

Problems↗
NASA NTRS1987

A Von Karman integral approach to a two phase boundary layer problem

A Von Karman integral approximation of a two phase boundary layer is developed for bodies of arbitrary shape. The flow field considered is that of the injection of water through a porous airfoil. A solution for the special case of a flat plate is presented. The equations for the airfoil solution are developed and possible effects on airflow separation are discussed.

Henry, R.↗
NASA NTRS1978

The phase-integral method for radiative transfer problems with highly-peaked phase functions

Complete solutions to the radiative transfer equation, including both azimuth and depth dependence, are provided by the discrete-ordinate method of Chandrasekhar, but these solutions are often limited because of large computer requirements. This paper presents a 'phase-integral' method which greatly reduces the number of discrete ordinates needed in the solution for highly peaked phase functions. A composite quadrature method is shown to be effective in further reducing the number of discrete ordinates required for highly anisotropic phase functions. Examples are given to indicate convergence requirements and expected accuracy in the complete solution for Henyey-Greenstein and cloud-type phase functions.

Fricke, C. L.↗