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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Moisture interaction and stability of ZOT (Zinc Orthotitanate) thermal control spacecraft coating

Two of the many performance requirements of the zinc orthotitanate (ZOT) ceramic thermal control paint covering parts of the Jupiter-bound Galileo spacecraft are that it be sufficiently electrically conductive so as to prevent electrostatic discharge (ESD) damage to onboard electronics and that it adhere to and protect the substrate from corrosion in terrestrial environments. The bulk electrical resistivity of ZOT on an aluminum substrate was measured over the ranges 22 C to 90 C and 0 percent RH to 100 percent RH, and also in soft (10 (minus 2) Torr) and hard (10 (minus 7) Torr) vacuums. No significant temperature dependence was evident, but measured resistivity values ranged over 9 orders of magnitude: 10 to the 5th power ohm-cm at 100 percent RH greater than 10 to the 12th power ohm-cm in a hard vacuum. The latter value violates the ESD criterion for a typical 0.019 cm thick coating. The corrosion study involved exposing typical ZOT substrate combinations to two moisture environments - 30 C/85 percent RH and 85 C/85 percent RH - for 2000 hours, during which time the samples were periodically removed for front-to-back electrical resistance and scratch/peel test measurements. It was determined that the ZOT/Al and ZOT/Mg systems are stable (no ZOT delamination), although some corrosion (oxide formation) and resistivity increases observed among the ZOT/Mg samples warrant that exposure of some parts to humid environments be minimized.

Mon, Gordon R.↗
NASA NTRS1970

Spacecraft control

Developing attitude control single-axis simulator for Thermoelectric Outer Planet Spacecraft

Source record↗
NASA NTRS2019

A Distributed Hierarchical Framework for Autonomous Spacecraft Control

Future human space missions for exploring beyond low Earth orbit are in the conceptual design stage. One such mission describes a habitat in cis-lunar orbit that is visited by crew periodically, others describe missions to Mars. These missions have one important thing in common: the need for autonomy on the spacecraft. This need stems from the latency and bandwidth constraints on communications between the vehicle and ground control. A variable amount of autonomy may be necessary whether the spacecraft has crew on board or not. Spacecraft are complex systems that are engineered as a collection of subsystems. These subsystems work together to control the overall state of the spacecraft. As such, solutions that increase the autonomy of the spacecraft (called autonomous functions) should respect both the independence and interconnectedness of the spacecraft subsystems. This distributed and hierarchical approach to system monitoring and control is a key idea in the Modular Autonomous Systems Technology (MAST) framework. The MAST framework enables a component-based architecture that provides interfaces and structure to developing autonomous technologies. The framework enforces a distributed, hierarchical architecture for autonomous control systems across subsystems, systems, elements, and vehicles. An example autonomous system was implemented in this framework and tested using realistic spacecraft software and hardware simulations. This paper will discuss the framework, tests conducted, results, and future work.

Badger, Julia M.↗
NASA NTRS1976

Distributed microprocessors for spacecraft control and data handling

The Unified Data System (UDS) group at JPL is attempting to reduce total mission costs by designing a spacecraft data system which takes advantage of the natural and historical partitioning of a spacecraft into subsystems. Each subsystem is assigned a microprocessor which needs just enough capability to control the sensors and actuators of that subsystem, collect its data and maintain time synchronization with the rest of the spacecraft. The resulting distributed system avoids many of the overhead costs of a single centralized multi-processing system. To minimize complexity and therefore minimize total mission costs, a variety of standards and restrictions are imposed on the design of hardware, software, and communications. Articulation of these standards and restrictions is a major benefit deriving from the UDS program.

Lesh, F.↗
NASA NTRS1994

Highly-Autonomous Event-Driven Spacecraft Control

Future JPL missions will continue to be scientifically and technically more ambitious, and will demand more autonomy to accomplish complex tasks in uncertain environments and in close proximity to extraterrestrial surfaces. A prime example is small body rendezvous and sample return.

attitude and control subsystem (ACS) rendezvous ta↗
NASA NTRS2003

Design and Analysis of the ST7 Disturbance Reduction System (DRS) Spacecraft Controller

The Space Technology 7 experiment will perform an on-orbit system-level validation of two specific Disturbance Reduction System technologies: a gravitational reference sensor employing a free-floating test mass and a set of micronewton colloidal thrusters. The Disturbance Reduction System is designed to maintain a spacecraft's position with respect to the free-floating test mass to less than 10 nm/square root of Hz, over the frequency range 10(exp -3) Hz to 10(exp -2) Hz. This paper presents the design and analysis of the coupled drag-free and attitude control system that closes the loop between the gravitational reference sensor and the micronewton thrusters while incorporating star tracker data at low frequencies. The effects of actuation and measurement noise and disturbances on the spacecraft and test masses are evaluated in a seven-degree-of-freedom planar model incorporating two translational and one rotational degrees of freedom for the spacecraft and two translational degrees of freedom for each test mass.

Maghami, P. G.↗
NASA NTRS1975

Computer program system for dynamic simulation and stability analysis of passive and actively controlled spacecraft. Volume 1. Theory

A theoretical development and associated digital computer program system is presented. The dynamic system (spacecraft) is modeled as an assembly of rigid and/or flexible bodies not necessarily in a topological tree configuration. The computer program system may be used to investigate total system dynamic characteristics including interaction effects between rigid and/or flexible bodies, control systems, and a wide range of environmental loadings. Additionally, the program system may be used for design of attitude control systems and for evaluation of total dynamic system performance including time domain response and frequency domain stability analyses. Volume 1 presents the theoretical developments including a description of the physical system, the equations of dynamic equilibrium, discussion of kinematics and system topology, a complete treatment of momentum wheel coupling, and a discussion of gravity gradient and environmental effects. Volume 2, is a program users' guide and includes a description of the overall digital program code, individual subroutines and a description of required program input and generated program output. Volume 3 presents the results of selected demonstration problems that illustrate all program system capabilities.

Bodley, C. S.↗
NASA NTRS1993

Simulation modeling for long duration spacecraft control systems

The use of simulation is described and it is contrasted to analytical solution techniques for evaluation of analytical reliability models. The role importance sampling plays in simulation of models of this type was also discussed. The simulator tool used for our analysis is described. Finally, the use of the simulator tool was demonstrated by applying it to evaluate the reliability of a fault tolerant hypercube multiprocessor intended for spacecraft designed for long duration missions. The reliability analysis was used to highlight the advantages and disadvantages offered by simulation over analytical solution of Markovian and non-Markovian reliability models.

Boyd, Mark A.↗
NASA NTRS1968

Spacecraft control

Partial inertial system integration tests, automatic lens design, and vibration and shock analyses of electrostatic gyroscope

Source record↗
NASA NTRS1982

Design practices for controlling spacecraft charging interactions

A design guidelines handbook prepared to provide criteria for assessing and minimizing spacecraft charging interactions is described. An evaluation philosophy of analyzing specific satellite designs in a substorm environment specification with NASCAP is proposed. Criteria for possible discharges are given and a technique for computing the discharge transients is outlined. The charging of a three axis stabilized satellite is examined to illustrate the philosophy. Possible discharge locations are found and transients computed. The effect of changing selected surface coatings is evaluated and found to substantially reduce charging levels.

Stevens, N. J.↗
NASA NTRS1986

Rapid torque-limited line-of-sight pointing of SCOLE (Spacecraft Control Laboratory Experiment) configuration

The design concept of a control for rapid torque-limited slewing of a rigid-mast version of the NASA SCOLE configuration is presented and demonstrated by means of numerical simulation. The time-optimal control problem for the system is decomposed into separate single-axis problems, expanding analytically the implicit nonlinear transcendental expression for the SCOLE line-of-sight error, and the final Euler attitude angles and slew angles are determined. The simulation results are presented in tables and graphs, and it is found that bang-bang or bang-pause-bang slew maneuvers with control moment applied to the Shuttle and control force applied to the reflector, and with a 5-deg/s slew-rate limit, produce the best pointing accuracy and the shortest slew times, although the specified line-of-sight error of 0.02 deg cannot be achieved using such open-loop single-axis maneuvers.

Lin, J. G.↗
NASA NTRS1987

Slew maneuver dynamics of the Spacecraft Control Laboratory experiment

Mathematical expressions for slew maneuver dynamics are presented. The total kinetic energy expression of the system is given as T = T(0) + T(1) + T(2), where T(0), T(1), and T(2) refer to the kinetic energies of the shuttle, the flexible beam, and the tip mass (the reflector), respectively. The specific equations for each of these are defined and integrated into the total energy expression. Using the chain rule in the Lagrange equations and an expression allowing the transformation of the orbiter angular velocity from the inertial frame to the body-fixed frame, the rotational equations are obtained. Finally, the vibration equations for the beam are derived, again using the Lagrange equations.

Kakad, Y. P.↗
NASA NTRS1985

Prototype fault isolation expert system for spacecraft control

A program which illustrates how an expert system might perform fault handling for a satellite propulsion subsystem is discussed. The program runs on a VAX 11/780 under VMS with a VT100 interface and is written in FRANZ/LISP. The program presents a series of menus to the user. Once the user selects from the menu, the program simulates the behavior of the hydrazine propulsion system under the fault condition, detects the presence of the fault, and then determines what set of actions to perform in implementing the fault workaround.

Truszkowski, Walt↗
NASA NTRS1987

Automation of spacecraft control centers

The objective is to describe the further automation of the Payload Operations Control Centers, specifically the Mission Operations Room, by using a series of expert systems interconnected together. The feasibility of using expert systems in the Mission Operations Room is presently being determined. The expert system under development is called the Communications Link Expert Assistance Resource (CLEAR) project. It is the first control center expert system being designed and implemented at Goddard. It will demonstrate the feasibility and practicality of expert systems in a real-time control center environment. There is a two-fold purpose. First is to briefly describe the present effort of the CLEAR expert system under development. The second is to describe how a series of interacting expert systems could be developed to almost totally automate the Mission Operations Room within the control center. How these expert systems would be put together and what functions they could perform in the control center is described. These efforts will provide a great deal of applicability toward the automation of the space station.

Dutilly, Robert↗