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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Performance analysis of an integrated GPS/inertial attitude determination system

The performance of an integrated GPS/inertial attitude determination system is investigated using a linear covariance analysis. The principles of GPS interferometry are reviewed, and the major error sources of both interferometers and gyroscopes are discussed and modeled. A new figure of merit, attitude dilution of precision (ADOP), is defined for two possible GPS attitude determination methods, namely single difference and double difference interferometry. Based on this figure of merit, a satellite selection scheme is proposed. The performance of the integrated GPS/inertial attitude determination system is determined using a linear covariance analysis. Based on this analysis, it is concluded that the baseline errors (i.e., knowledge of the GPS interferometer baseline relative to the vehicle coordinate system) are the limiting factor in system performance. By reducing baseline errors, it should be possible to use lower quality gyroscopes without significantly reducing performance. For the cases considered, single difference interferometry is only marginally better than double difference interferometry. Finally, the performance of the system is found to be relatively insensitive to the satellite selection technique.

Sullivan, Wendy I.↗
NASA NTRS1976

Performance analysis of a laser propelled interorbital tansfer vehicle

Performance capabilities of a laser-propelled interorbital transfer vehicle receiving propulsive power from one ground-based transmitter was investigated. The laser transmits propulsive energy to the vehicle during successive station fly-overs. By applying a series of these propulsive maneuvers, large payloads can be economically transferred between low earth orbits and synchronous orbits. Operations involving the injection of large payloads onto escape trajectories are also studied. The duration of each successive engine burn must be carefully timed so that the vehicle reappears over the laser station to receive additional propulsive power within the shortest possible time. The analytical solution for determining these time intervals is presented, as is a solution to the problem of determining maximum injection payloads. Parameteric computer analysis based on these optimization studies is presented. The results show that relatively low beam powers, on the order of 50 MW to 60 MW, produce significant performance capabilities.

Minovitch, M. A.↗
NASA NTRS1977

Computer program for design and performance analysis of navigation-aid power systems. Program documentation. Volume 1: Software requirements document

A computer program has been developed for designing and analyzing the performance of solar array/battery power systems for the U.S. Coast Guard Navigational Aids. This program is called the Design Synthesis/Performance Analysis (DSPA) Computer Program. The basic function of the Design Synthesis portion of the DSPA program is to evaluate functional and economic criteria to provide specifications for viable solar array/battery power systems. The basic function of the Performance Analysis portion of the DSPA program is to simulate the operation of solar array/battery power systems under specific loads and environmental conditions. This document establishes the software requirements for the DSPA computer program, discusses the processing that occurs within the program, and defines the necessary interfaces for operation.

Goltz, G.↗
NASA NTRS1980

Performance analysis of the Spaceborne Laser Ranging System

The performance of the Spaceborne Laser Ranging System in the determination of distances between ground-based targets is discussed. The system consists of an orbiting pulsed laser distance measurement system that sequentially measures the distance to retroreflector arrays on the ground. Intersite distances are then determined from an analysis of the vertical distance data and the spacecraft orbital dynamics. Results of computer simulations indicate that for a six-day observing period with 50 percent cloud cover, uncertainties of 1 to 3 cm are expected for intertarget separations of 50 to 1200 km, with vertical uncertainties from 1 to 12 cm. Furthermore, it is found that by redetermining relative target positions, precision can be increased to less than 0.3 cm to 1 cm in the baseline and to 0.4 to 4 cm in vertical distance. It is concluded that with these precisions, strain and strain rate can be determined for crustal dynamics and earthquake studies, and geodetic surveys can be performed.

Kahn, W. D.↗
NASA NTRSDate not supplied

Robust Trajectory Optimization and GN&C Performance Analysis for NRHO Rendezvous

This paper evaluates several candidate Near-Rectilinear Halo Orbits (NRHO) rendezvous trajectory designs using linear covariance (LinCov) analysis and determines the optimal locations for NRHO rendezvous translational maneuver locations. The performance of several candidate relative trajectory designs are determined as a function of relative navigation accuracy (angles only), inertial optical navigation (OpNav), range observability maneuvers, maneuver execution errors, relative maneuver targeting, and environment uncertainties. Further, the optimal locations of rendezvous maneuvers are determined for each of the candidate reference trajectories. The long-term goal of this research is to utilize LinCov and a genetic optimization algorithm (GA) to determine a complete end-to-end optimal NRHO trajectory design that is robust to navigation errors, maneuver execution errors, and environment uncertainties. This paper represents a first step toward this goal. Three candidate rendezvous trajectories with varying numbers of range-observability maneuvers are evaluated for their robustness to uncertainties, errors, and total trajectory correction delta-v performance. Some key elements of this analysis include relative navigation performance in an NRHO, relative trajectory dispersion performance, and total 3-sigma delta-v performance. This development provides the foundation to then determine an optimal and robust end-to-end NRHO rendezvous trajectory, including the determination of the optimal locations of range observability maneuvers, if needed.

Linear Covariance Analysis↗
NASA NTRSDate not supplied

Performance Analysis of SmallSat Aerocapture at Venus

Aerocapture is a method of spacecraft orbital insertion that has the potential to provide mass savings as compared to aerobraking. In particular, aerocapture at Venus is desirable due to high atmospheric density and potential for science return. While promising, accurate orbital insertion by means of aerocapture requires an active guidance, navigation, and control architecture. This paper documents the initial assessment of the performance of two guidance algorithms, a generalized numerical predictor corrector and the Fully-Numeric Predictor- corrector for Aerocapture Guidance, applied to smallsat aerocapture at Venus using two different simulation environments with equivalent simulation inputs. Nominal trajectory performance is assessed. In addition, Monte Carlo analysis is performed to compare each guidance algorithm’s performance under uncertainty.

aerocapture↗
NASA NTRSDate not supplied

Performance Analysis of SmallSat Aerocapture at Venus

Aerocapture is a method of spacecraft orbital insertion that has the potential to provide mass savings as compared to aerobraking. In particular, aerocapture at Venus is desirable due to high atmospheric density and potential for science return. While promising, accurate orbital insertion by means of aerocapture requires an active guidance, navigation, and control architecture. This paper documents the initial assessment of the performance of two guidance algorithms, a generalized numerical predictor corrector and the Fully-Numeric Predictor-corrector for Aerocapture Guidance, applied to smallsat aerocapture at Venus using two different simulation environments with equivalent simulation inputs. Nominal trajectory performance is assessed. In addition, Monte Carlo analysis is performed to compare each guidance algorithm’s performance under uncertainty.

aerocapture↗
NASA NTRS1993

Recent refinements and increased capabilities in balloon vertical performance analysis

The NASA Thermal Trajectory analysis model for predicting the vertical performance of balloons is described in terms of two critical refinements and recent results. The model employs heat-balance equations and a vertical equation of motion, and revised methods are employed to predict maximum balloon volume, balloon shape, and the continuous computation of gas loss. Also incorporated are modeling techniques for assessing the solar radiation input that can affect the load tapes, and autoballast control algorithms are employed. The model permits the evaluation of the presence of cap layers as well as the effects of small leaks and programmed venting. The revised model is shown to give good predictions of balloon performance during flight in terms of altitude changes, descent rates, gas-mass flow, and leak potential. The model is found to be more versatile due to autoballasting and leak analysis, and good prediction are possible for the float phase and descent of current balloon shapes.

Conrad, G. R.↗
NASA NTRS1980

Performance analysis and simulation of the SPS reference phase control system

The solar power satellite (SPS) concept envisions several hundred thousand synchronized microwave power amplifiers operating in parallel to produce an aggregate power output of 5-10 GW. This power is to be transferred to earth with the aid of a microwave/millimeter-wave beaming system operating in a synchronous orbit. The reference phase control system is considered along with aspects of pilot signal parameter selection. A power transponder analysis is conducted and an SPS performance evaluation is performed. Attention is given to system jitters and imperfections, the definition of power transfer efficiency, and the effects of system imperfections on SPS efficiency. It is found that the power transfer efficiency is relatively insensitive to the amplitude jitters. However, the effects of location jitters can produce a severe degradation of efficiency.

Chie, C. M.↗
NASA NTRS1985

Performance analysis of the ALOHA protocol with replication in a fading channel for the Mobile Satellite Experiment

The analysis of the ALOHA random access protocol for communications channels with fading is presented. The protocol is modified to send multiple contiguous copies of a message at each transmission attempt. Both pure and slotted ALOHA channels are considered. A general two state model is used for the channel error process to account for the channel fading memory. It is shown that greater throughput and smaller delay may be achieved using repetitions. The model is applied to the analysis of the delay-throughput performance in a fading mobile communications environment. Numerical results are given for NASA's Mobile Satellite Experiment.

Clare, L. P.↗
NASA NTRS2012

Performance Analysis of a NASA Integrated Network Array

The Space Communications and Navigation (SCaN) Program is planning to integrate its individual networks into a unified network which will function as a single entity to provide services to user missions. This integrated network architecture is expected to provide SCaN customers with the capabilities to seamlessly use any of the available SCaN assets to support their missions to efficiently meet the collective needs of Agency missions. One potential optimal application of these assets, based on this envisioned architecture, is that of arraying across existing networks to significantly enhance data rates and/or link availabilities. As such, this document provides an analysis of the transmit and receive performance of a proposed SCaN inter-network antenna array. From the study, it is determined that a fully integrated internetwork array does not provide any significant advantage over an intra-network array, one in which the assets of an individual network are arrayed for enhanced performance. Therefore, it is the recommendation of this study that NASA proceed with an arraying concept, with a fundamental focus on a network-centric arraying.

Nessel, James A.↗
NASA NTRS1998

Inlet Performance Analysis Code Developed

The design characteristics of an inlet very much depend on whether the inlet is to be flown at subsonic, supersonic, or hypersonic speed. Whichever the case, the primary function of an inlet is to deliver free-stream air to the engine face at the highest stagnation pressure possible and with the lowest possible variation in both stagnation pressure and temperature. At high speeds, this is achieved by a system of oblique and/or normal shock waves, and possibly some isentropic compression. For both subsonic and supersonic flight, current design practice indicates that the inlet should deliver the air to the engine face at approximately Mach 0.45. As a result, even for flight in the high subsonic regime, the inlet must retard (or diffuse) the air substantially. Second, the design of an inlet is influenced largely by the compromise between high performance and low weight. This compromise involves tradeoffs between the mission requirements, flight trajectory, airframe aerodynamics, engine performance, and weight-all of which, in turn, influence each other. Therefore, to study the effects of some of these influential factors, the Propulsion System Analysis Office of the NASA Lewis Research Center developed the Inlet Performance Analysis Code (IPAC). This code uses oblique shock and Prandtl-Meyer expansion theory to predict inlet performance. It can be used to predict performance for a given inlet geometric design such as pitot, axisymmetric, and two-dimensional. IPAC also can be used to design preliminary inlet systems and to make subsequent performance analyses. It computes the total pressure, the recovery, the airflow, and the drag coefficients. The pressure recovery includes losses associated with normal and oblique shocks, internal and external friction, the sharp lip, and diffuser components. Flow rate includes captured, engine, spillage, bleed, and bypass flows. The aerodynamic drag calculation includes drags associated with spillage, cowl lip suction, wave, bleed, and bypass.

Jules, Kenol↗
NASA NTRS1980

Off-design performance analysis of MHD generator channels

A computer code for performing parametric design point calculations, and evaluating the off-design performance of MHD generators has been developed. The program is capable of analyzing Faraday, Hall, and DCW channels, including the effect of electrical shorting in the gas boundary layers and coal slag layers. Direct integration of the electrode voltage drops is included. The program can be run in either the design or off-design mode. Details of the computer code, together with results of a study of the design and off-design performance of the proposed ETF MHD generator are presented. Design point variations of pre-heat and stoichiometry were analyzed. The off-design study included variations in mass flow rate and oxygen enrichment.

Wilson, D. R.↗
NASA NTRS1972

Pulse performance analysis for small hypergolic propellant rocket engines

Small rocket engine tests were conducted for the purpose of obtaining pulse performance data to aid in preliminary design and evaluation of attitude control systems. Both monopropellant and hypergolic bipropellant engines of thrust levels from 5 to 445 N (1 to 100 lb) were tested. The performance data for the hypergolic propellant rockets are compared with theoretical performance calculated from idealized chamber filling and evacuation characteristics. Electromechanical delays in valve response and heat transfer characteristics were found to cause substantial deviation between theoretical performance and test performance. The theoretical analysis is modified to obtain a semiempirical model for hypergolic propellant rockets.

Smith, G. W.↗
NASA NTRS1972

Pulse performance analysis for small hypergolic-propellant rocket engines

Small rocket engine tests were conducted for the purpose of obtaining pulse performance data to aid in preliminary design and evaluation of attitude control systems. Both monopropellant and hypergolic bipropellant engines of thrust levels from 1 to 100 lbs were tested. The performance data for the hypergolic propellant rockets are compared with theoretical performance calculated from idealized chamber filling and evacuation characteristics. Electromechanical delays in valve response and heat transfer characteristics were found to cause substantial deviation between theoretical and test performance. The theoretical analysis is modified to obtain a semi-empirical model for hypergolic propellant rockets which is demonstrated to be reasonably accurate for two different engine configurations over a considerable range of duty cycles.

Smith, G. W.↗
NASA NTRSDate not supplied

NESC GN&C TDT Workshop on 2D Image Motion Optical Transfer Functions, Pointing Performance Analysis, and Requirements

This course was prepared by the author in support of the NASA GN&C Technical Discipline Team (TDT). The purpose of this two-day course is to inform practicing GN&C engineers, and other system and subsystem engineers, including payload engineers and mission analysts, of methodologies to analyze the pointing performance of spacecraft and to write unambiguous pointing requirements that are relevant to optical payload performance. It is hoped that the seminar will contribute to a best-practices manual and contribute to accepted and uniform means of requirements definition, validation, and verification. The course material is designed to address the needs of not only practicing GN&C engineers, but also system and subsystem engineers of other disciplines, payload engineers, mission analysts, and even astronomers who need to understand how they interface to a GN&C subsystem. Much revision is the direct result of active student participation during the presentations and from feedback obtained through course evaluation forms.

2D Image↗
NASA NTRS2015

Conflict Detection Performance Analysis for Function Allocation Using Time-Shifted Recorded Traffic Data

The performance of the conflict detection function in a separation assurance system is dependent on the content and quality of the data available to perform that function. Specifically, data quality and data content available to the conflict detection function have a direct impact on the accuracy of the prediction of an aircraft's future state or trajectory, which, in turn, impacts the ability to successfully anticipate potential losses of separation (detect future conflicts). Consequently, other separation assurance functions that rely on the conflict detection function - namely, conflict resolution - are prone to negative performance impacts. The many possible allocations and implementations of the conflict detection function between centralized and distributed systems drive the need to understand the key relationships that impact conflict detection performance, with respect to differences in data available. This paper presents the preliminary results of an analysis technique developed to investigate the impacts of data quality and data content on conflict detection performance. Flight track data recorded from a day of the National Airspace System is time-shifted to create conflicts not present in the un-shifted data. A methodology is used to smooth and filter the recorded data to eliminate sensor fusion noise, data drop-outs and other anomalies in the data. The metrics used to characterize conflict detection performance are presented and a set of preliminary results is discussed.

Guerreiro, Nelson M.↗