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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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NASA NTRS1996

On-orbit application of H-infinity to the middeck active controls experiment: Overview of results

The Middeck Active Control Experiment (MACE) was successfully completed during the flight of STS-67 in March 1995. MACE provided an on-orbit validation of modem robust control theory and system identification techniques through the testing of a flexible, multi-instrument, science platform in the micro-gravity environment of the Space Shuttle's Middeck. As part of this experiment, H-infinity control design was validated in zero gravity (0-G) environment. The control objective was to isolate a payload sensor from a 5O Hz bandwidth disturbance occurring on the test article. Controllers were designed with the use of finite element models developed using 1 -G measurements and a measurement model obtained by applying system identification techniques to open loop data obtained on orbit. Over 50 single-input, single-output and multi-input, multi-output, single and multi-axis H-infinity control designs were evaluated on-orbit. Up to 19 dB reduction in vibration levels and 25 Hz bandwidth of control were achieved.

Woods-Vedeler, Jessica A.↗

NASA NTRS1990

Decentralized control experiments on the JPL flexible spacecraft

Decentralized control experiments were successfully demonstrated for the JPL/AFAL Flexible Structure. A simulation package using MATRIXx showed strong correlation between the simulations and experimental result, while providing a means for test and debug of the various control strategies. Implementation was simplified by a modular software design that was easily transported from the simulation environment to the experimental environment. Control designs worked well for suppression of the dominant modes of the structure. Static decentralized output feedback dampened the excited modes of the structure, but sometimes excited higher order modes upon startup of the controller. A second-order frequency shaping controller helped to eliminate excitation of the higher order modes by attenuating high frequencies in the control effort. However, it also resulted in slightly longer settling times.

Ozguner, U.↗

NASA NTRS1990

Dynamics and control of multipayload platforms - The Middeck Active Control Experiment (MACE)

A flight experiment entitled the Middeck Active Control Experiment (MACE) proposed by the Space Engineering Research Center (SERC) at the Massachusetts Institute of Technology is described. The objective of this program is to investigate and validate the modeling of the dynamics of an actively controlled flexible, articulating, multibody platform free floating in zero gravity. A rationale and experimental approach for the program are presented. The rationale shows that on-orbit testing, coupled with ground testing and a strong analytical program, is necessary in order to fully understand both how flexibility of the platform affects the pointing problem, as well as how gravity perturbs this structural flexibility causing deviations between 1-and 0-gravity behavior. The experimental approach captures the essential physics of multibody platforms, by identifying the appropriate attributes, tests, and performance metrics of the test article, and defines the tests required to successfully validate the analytical framework.

Miller, David W.↗

NASA NTRS1992

The Middeck Active Control Experiment (MACE)

Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: program objectives; program features; flight experiment features; current activities; MACE development model lab testing; MACE test article deployed on STS middeck; and development model testing.

Miller, David W.↗

NASA NTRS1991

The Middeck Active Control Experiment (MACE)

Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: science program objectives and rationale; science requirements; capturing the essential physics; science development approach; development model hardware; development model test plan; and flight hardware and operations.

Miller, David W.↗

NASA NTRS1992

In-step Two-phase Flow (TPF) Thermal Control Experiment

The Two-Phase Flow Thermal Control Experiment is part of the NASA/OAST In-Space Technology Experiments (In-STEP) Program. The experiment is configured for the Hitchhiker Shuttle payload system and consists of a capillary pumped loop, heatpipe radiator, and two-phase flow heat exchanger. The flight experiment design approach, test plan, payload design, and test components are described in outline and graphic form.

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NASA NTRS1984

A deployable structure and solar array controls experiment for STEP

A candidate configuration for a controls experiment on the Space Technology Experiments Platform (STEP) is described. The elements of the experiment are the mast, the solar array, and an articulation module between the two. The characteristic dimensions are very compatible for integration on a pallet such a STEP's proposed configuration. The controls' objective would be the measurement of orbiter interaction as well as the system identification of the appendages. The flight experiment configuration would also provide a test bed for various active vibration controls concepts. The instrumentation being considered would measure accelerations, strains, displacements, and temperatures. The deployable mast has eight elements defining a structural bay. Uniaxial measurements would be required to define loads at a cross section of the structure. Displacements due to thermal distortion of the mast and the local state of the solar concentrator may be measured by an optical ranging technique from the orbiter aft flight deck.

Nishimoto, T. S.↗

NASA NTRS1989

Tank Pressure Control Experiment on the Space Shuttle

The tank pressure control experiment is a demonstration of NASA intent to develop new technology for low-gravity management of the cryogenic fluids that will be required for future space systems. The experiment will use freon as the test fluid to measure the effects of jet-induced fluid mixing on storage tank pressure and will produce data on low-gravity mixing processes critical to the design of on-orbit cryogenic storage and resupply systems. Basic data on fluid motion and thermodynamics in low gravity is limited, but such data is critical to the development of space transfer vehicles and spacecraft resupply facilities. An in-space experiment is needed to obtain reliable data on fluid mixing and pressure control because none of the available microgravity test facilities provide a low enough gravity level for a sufficient duration to duplicate in-space flow patterns and thermal processes. Normal gravity tests do not represent the fluid behavior properly; drop-tower tests are limited in length of time available; aircraft low-gravity tests cannot provide the steady near-zero gravity level and long duration needed to study the subtle processes expected in space.

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NASA NTRS1978

A feasibility study of orbiter flight control experiments

The results of a feasibility study of orbiter flight control experiments performed are summarized. Feasibility studies were performed on a group of 14 experiments selected from a candidate list of 35 submitted to the study contractor by the flight control community. Concepts and requirements were developed for the 14 selected experiments and they were ranked on a basis of technical value, feasibility, and cost. It was concluded that all the selected experiments can be considered as potential candidates for the Orbiter Experiment program, which is being formulated for the Orbiter Flight Tests and subsequent operational flights, regardless of the relative ranking established during the study. None of the selected experiments has significant safety implications and the cost of most was estimated to be less than $200K.

Geissler, W. H.↗

NASA NTRS1997

Enhanced Attitude Control Experiment for SSTI Lewis Spacecraft

The enhanced attitude control system experiment is a technology demonstration experiment on the NASA's small spacecraft technology initiative program's Lewis spacecraft to evaluate advanced attitude control strategies. The purpose of the enhanced attitude control system experiment is to evaluate the feasibility of designing and implementing robust multi-input/multi-output attitude control strategies for enhanced pointing performance of spacecraft to improve the quality of the measurements of the science instruments. Different control design strategies based on modern and robust control theories are being considered for the enhanced attitude control system experiment. This paper describes the experiment as well as the design and synthesis of a mixed H(sub 2)/H(sub infinity) controller for attitude control. The control synthesis uses a nonlinear programming technique to tune the controller parameters and impose robustness and performance constraints. Simulations are carried out to demonstrate the feasibility of the proposed attitude control design strategy. Introduction

Maghami, Peoman G.↗

NASA NTRS1992

Advanced Communications Technology Satellite high burst rate link evaluation terminal experiment control and monitor software maintenance manual, version 1.0

The Experiment Control and Monitor (EC&M) software was developed at NASA Lewis Research Center to support the Advanced Communications Technology Satellite (ACTS) High Burst Rate Link Evaluation Terminal (HBR-LET). The HBR-LET is an experimenter's terminal to communicate with the ACTS for various investigations by government agencies, universities, and industry. The EC&M software is one segment of the Control and Performance Monitoring (C&PM) software system of the HBR-LET. The EC&M software allows users to initialize, control, and monitor the instrumentation within the HBR-LET using a predefined sequence of commands. Besides instrument control, the C&PM software system is also responsible for computer communication between the HBR-LET and the ACTS NASA Ground Station and for uplink power control of the HBR-LET to demonstrate power augmentation during rain fade events. The EC&M Software User's Guide, Version 1.0 (NASA-CR-189160) outlines the commands required to install and operate the EC&M software. Input and output file descriptions, operator commands, and error recovery procedures are discussed in the document. The EC&M Software Maintenance Manual, Version 1.0 (NASA-CR-189161) is a programmer's guide that describes current implementation of the EC&M software from a technical perspective. An overview of the EC&M software, computer algorithms, format representation, and computer hardware configuration are included in the manual.

Reinhart, Richard C.↗

NASA NTRS1990

Tank Pressure Control Experiment - A low-g mixing investigation

The Tank Pressure Control Experiment (TPCE) was conceived to meet the need for an aspect of cryogenic fluid management technology that is critical to several future national space missions: control of cryogenic storage tank pressures by active mixing. In-space testing is the only means of obtaining the fluid dynamic data necessary to develop and test predictive models of mixing. These models, when validated, will allow future cryogenic systems to be designed with more efficient and reliable pressure control systems. The objectives of the TPCE project are to characterize the fluid dynamics of jet-induced mixing in low gravity, evaluate the validity of empirical models and correlations, and provide data for use in developing and validating computational fluid dynamic models. This paper discusses prior studies of low-g mixing, the objectives and benefits of TPCE, the design and status of the payload, and preliminary results obtained from low-g aircraft testing.

Bentz, M. D.↗

NASA NTRS1992

Advanced communications technology satellite high burst rate link evaluation terminal experiment control and monitor software user's guide, version 1.0

Reinhart, Richard C.↗

NASA NTRS1992

The middeck active control experiment: Gravity and suspension effects

Viewgraphs on the Middeck Active Control Experiment (MACE): Gravity and Suspension Effects are presented. Topics covered include: gravity and suspension influences; gravity and suspension effects on structure; gravity effects on sensors and actuators; modeling of gravity and suspension effects on structure; geometric stiffness theory and initial static deformation calculation; modeling gravity's effect on accelerometers and PMA's; application to MACE; MACE EM configuration study; and MACE DM configuration study.

Crawley, Edward F.↗

NASA NTRS2015

Preliminary Simulations of the Ullage Dynamics in Microgravity during the Jet Mixing Portion of Tank Pressure Control Experiments

The results of CFD simulations of microgravity tank pressure control experiments performed on the Space Shuttle are presented. A 13.7 liter acrylic model tank was used in these experiments. The tank was filled to an 83 percent fill fraction with Freon refrigerant to simulate cryogenic propellants stored in space. In the experiments, a single liquid jet near the bottom of the tank was used for mixing the tank. Simulations at a range of jet Weber numbers were performed. Qualitative comparisons of the liquid and gas interface dynamics observed and recorded in the experiments and those computed are shown and discussed. The simulations were able to correctly capture jet penetration of the ullage, qualitatively reproduce ullage shapes and dynamics, as well as the final equilibrium position of the ullage.

jet mixing↗

NASA NTRS2015

Preliminary Simulations of the Ullage Dynamics in Microgravity During the Jet Mixing Portion of Tank Pressure Control Experiments

simulation↗

NASA NTRS1991

Active member vibration control experiment in a KC-135 reduced gravity environment

An active member vibration control experiment in a KC-135 reduced gravity environment was carried out by the Air Force Flight Dynamics Laboratory and the Jet Propulsion Laboratory. Two active members, consisting of piezoelectric actuators, displacement sensors, and load cells, were incorporated into a 12-meter, 104 kg box-type test structure. The active member control design involved the use of bridge (compound) feedback concept, in which the collocated force and velocity signals are feedback locally. An impact-type test was designed to accommodate the extremely short duration of the reduced gravity testing window in each parabolic flight. The moving block analysis technique was used to estimate the modal frequencies and dampings from the free-decay responses. A broadband damping performance was demonstrated up to the ninth mode of 40 Hz. The best damping performance achieved in the flight test was about 5 percent in the fourth mode of the test structure.

Lawrence, C. R.↗

NASA NTRS1990

Progress on control experiments of flexible structures

Progress at the NASA Langley Research Center in the area of control experiments for flexible structures is described. First the author presents the experimental results for a linear model which represents slewing maneuvers of a generic space station solar panel carried out to evaluate experimentally some control technologies. Then the status of the rotational/translational maneuvering experiment of a flexible steel panel carried by a translation cart is presented. Finally, experimental results of the NASA minimast testbed using velocity command stepper motors as reaction mass reactors are shown. All the test configurations are briefly described, including actuator and sensor, test setup, and test software. The status of some research activities oriented primarily to the experimental methods for control of flexible structures is presented.

Juang, Jer-Nan↗