An Experimental Kalman Filter Approach to the International Terrestrial Reference Frame Realization
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Kalman Filter↗
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Results for “space frame”
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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Development of inflatable antenna structures
Self-rigidizable spring-tape-reinforced (STR) booms were used to develop structural systems for large-aperture space inflatable radar antennas. The lightweight planar frames built with STR booms can be compactly stowed for launch, deployed by inflation pressure in space, and used to tension the RF membrane apertures of the antennas. Engineering models of a Ka-band reflectarray antenna and a L-band synthetic-aperture radar antenna were developed and have successfully demonstrated stowage and deployment, as well as RF performance. A design improvement was also being implemented to enhance long-term configuration stability and widen the application range of the STR booms.
inflatable antenna structures deployment↗
Candidate proof mass actuator control laws for the vibration suppression of a frame
The vibration of an experimental flexible space truss is controlled with internal control forces produced by several proof mass actuators. Four candidate control law strategies are evaluated in terms of performance and robustness. These control laws are experimentally implemented on a quasi free-free planar truss. Sensor and actuator dynamics are included in the model such that the final closed loop is self-equilibrated. The first two control laws considered are based on direct output feedback and consist of tuning the actuator feedback gains to the lowest mode intended to receive damping. The first method feeds back only the position and velocity of the proof mass relative to the structure; this results in a traditional vibration absorber. The second method includes the same feedback paths as the first plus feedback of the local structural velocity. The third law is designed with robust H infinity control theory. The fourth strategy is an active implementation of a viscous damper, where the actuator is configured to provide a bending moment at two points on the structure. The vibration control system is then evaluated in terms of how it would benefit the space structure's position control system.
Umland, Jeffrey W.↗
Toward 10(exp 9) GPS geodesy: Vector baselines, Earth rotation and reference frames
The University of Texas Center for Space Research research efforts under NASA Grant No. NAG-1936 from 1 Jan. 1992 - 31 Dec. 1992 were in the following areas: GPS orbit accuracy assessments and efforts to improve the accuracy; analysis of global GPS data collected during the first three months of the IGS campaign, and analysis of regional data. A brief summary of each of the above activities is presented in the following.
Schutz, Bob E.↗
The Rocket Balloon (Rocketball): Applications to Science, Technology, and Education
Originally envisioned to study upper atmospheric phenomena, the Rocket Balloon system (or Rocketball for short) has utility in a range of applications, including sprite detection and in-situ measurements, near-space measurements and calibration correlation with orbital assets, hurricane observation and characterization, technology testing and validation, ground observation, and education. A salient feature includes the need to reach space and near-space within a critical time-frame and in adverse local meteorological conditions. It can also provide for the execution of technology validation and operational demonstrations at a fraction of the cost of a space flight. In particular, planetary entry probe proof-of-concepts can be examined. A typical Rocketball operational scenario consists of a sounding rocket launch and subsequent deployment of a balloon above a desired location. An obvious advantage of this combination is the additional mission 'hang-time' rendered by the balloon once the sounding rocket flight is completed. The system leverages current and emergent technologies at the NASA Goddard Space Flight Center and other organizations.
Esper, Jaime↗
Integrable deformation of $\mathbb{C}$P n and generalised Kähler geometry
We build on the results of [1] for generalised frame fields on generalised quotient spaces and study integrable deformations for CP n . In particular we show how, when the target space of the Principal Chiral Model is a complex projective space, a two-parameter deformation can be introduced in principle. The second parameter can however be removed via a diffeomorphism, which we construct explicitly, in accordance with the results stemming from a thorough integrability analysis we carry out. We also elucidate how the deformed target space can be seen as an instance of generalised Kähler, or equivalently bi-Hermitian, geometry. In this respect, we find the generic form of the pure spinors for CP n and the explicit expression for the generalised Kähler potential for n = 1, 2.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Best-fit estimate of relativistic effects in time-delay experiments.
Time-delay experiments are analyzed within the frame of a curved space-time. Residuals from Newtonian best fits of relativistic data are used as a measure of the 'relativistic effects.' Radial transponder trajectories are considered. If the motion is towards the sun, the relativistic residuals are of the order of 100 m. If the motion is away from the sun, they are at the 10-km level and the fraction due to the second-order curvature of the metric is at the 1-km level. Those effects are significantly smaller than those calculated from the divergence of the Newtonian and relativistic predictions after exact fit of the initial measurements.
Richard, J.-P.↗
A new theory of gravity
A new relativistic theory of gravity is presented. This theory agrees with all experiments to date. It is a metric theory, it is Lagrangian-based, and it possesses a preferred frame with conformally-flat space slices. With an appropriate choice of certain adjustable functions and parameters, this theory possesses precisely the same post-Newtonian limit as general relativity.
Ni, W.↗
Which electromagnetic equations apply in rotating coordinates
It was discovered some years ago by Schiff that two equations for fields in vacuum do not carry over without change from an inertial frame to a frame with rotating axes of space coordinates, even for a region with all velocities much lower than the speed of light. However, the belief that all four of the field equations are invariant under such conditions is still prevalent and causes misconceptions in physical applications, including astrophysical and geophysical ones. The purpose of the present paper is therefore to call attention to Schiff's discovery, discussing its basis and its extension to fields in material media, and to interpret the additional terms that must be added to the equations in order to obtain valid transformations to rotating axes of coordinates.
Webster, D. L.↗
Cartesian-based control of a deformable robot manipulator
A control scheme for the 6-DOF Cincinnati-Milacron T3 robot arm is developed and demonstrated by means of numerical simulations. The arm is modeled as an open-loop articulated system with both actuators and position and velocity sensors at each joint, and a Cartesian-frame control algorithm is constructed in which (1) an adaptive scheme decouples the end-effector subsystem from the complex highly nonlinear main system and (2) a servo scheme drives the reduced system to follow a presumed end-effector trajectory on the basis of the Cartesian-frame feedback gains. The velocity transformation used to transfer the control forces from the Cartesian frame to joint-based space is explained, and the simulation results are presented in extensive graphs and diagrams. The control is found to respond well to system-topology changes and robot-environment impacts.
Chang, C. W.↗
Report of the panel on international programs
The panel recommends that NASA participate and take an active role in the continuous monitoring of existing regional networks, the realization of high resolution geopotential and topographic missions, the establishment of interconnection of the reference frames as defined by different space techniques, the development and implementation of automation for all ground-to-space observing systems, calibration and validation experiments for measuring techniques and data, the establishment of international space-based networks for real-time transmission of high density space data in standardized formats, tracking and support for non-NASA missions, and the extension of state-of-the art observing and analysis techniques to developing nations.
Anderson, Allen Joel↗
FIDEX: An expert system for satellite diagnostics
A Fault Isolation and Diagnostic Expert system (FIDEX) was developed for communication satellite diagnostics. It was designed specifically for the 30/20 GHz satellite transponder. The expert system was designed with a generic structure and features that make it applicable to other types of space systems. FIDEX is a frame based system that enjoys many of the inherent frame base features, such as hierarchy that describes the transponder's components, with other hierarchies that provide structural and fault information about the transponder. This architecture provides a flexible diagnostic structure and enhances maintenance of the system. FIDEX also includes an inexact reasoning technique and a primitive learning ability. Inexact reasoning was an important feature for this system due to the sparse number of sensors available to provide information on the transponder's performance. FIDEX can determine the most likely faulted component under the constraint of limited information. FIDEX learns about the most likely faults in the transponder by keeping a record of past established faults. FIDEX also has the ability to detect anomalies in the sensors that provide information on the transponders performance.
Durkin, John↗
Error coding simulations in C
When data is transmitted through a noisy channel, errors are produced within the data rendering it indecipherable. Through the use of error control coding techniques, the bit error rate can be reduced to any desired level without sacrificing the transmission data rate. The Astrionics Laboratory at Marshall Space Flight Center has decided to use a modular, end-to-end telemetry data simulator to simulate the transmission of data from flight to ground and various methods of error control. The simulator includes modules for random data generation, data compression, Consultative Committee for Space Data Systems (CCSDS) transfer frame formation, error correction/detection, error generation and error statistics. The simulator utilizes a concatenated coding scheme which includes CCSDS standard (255,223) Reed-Solomon (RS) code over GF(2(exp 8)) with interleave depth of 5 as the outermost code, (7, 1/2) convolutional code as an inner code and CCSDS recommended (n, n-16) cyclic redundancy check (CRC) code as the innermost code, where n is the number of information bits plus 16 parity bits. The received signal-to-noise for a desired bit error rate is greatly reduced through the use of forward error correction techniques. Even greater coding gain is provided through the use of a concatenated coding scheme. Interleaving/deinterleaving is necessary to randomize burst errors which may appear at the input of the RS decoder. The burst correction capability length is increased in proportion to the interleave depth. The modular nature of the simulator allows for inclusion or exclusion of modules as needed. This paper describes the development and operation of the simulator, the verification of a C-language Reed-Solomon code, and the possibility of using Comdisco SPW(tm) as a tool for determining optimal error control schemes.
Noble, Viveca K.↗
The Ethics of Human Spaceflight
This chapter intends to lay out some essential ethics questions that might frame the next step of space exploration. In this, I undertake two sorts of tasks. The first is to respond to the core ethic question: Is it ethical to travel in space? The second, assuming for the moment that I can convince you that the first premise can be justified, is to comment on what ethical challenges will face us there. It is appropriate to have a philosopher comment on this at the fortieth anniversary celebration, since it was also in 1962 that the National Academy of Science first convened a panel of philosophers to comment on space travel. They asked at that time whether it was indeed a worthwhile pursuit to travel in space and what might be expected of such an effort. What is at stake in any such boundary crossing is how the changing of essential human perimeters changes our own moral status. Will such boundary crossing worsen our human condition, or will it enhance it? In this way, the geopolitical quest is then linked to the quest for ontology, Pisarro hunting for the fountain of youth, for gold, and for territory. What follows are a series of ethical claims that link the problem of discovery in the larger world and the attendant ethical dilemmas of our explorations, as well as how this exploration alters our concepts of life on Earth. In this, the role of the ethicist is to function as both a skeptic and a stranger, aware of the optimism of science and the pessimism of philosophy.
Zoloth, Laurie↗
Segmented combustor
A combustor liner segment includes a panel having four sidewalls forming a rectangular outer perimeter. A plurality of integral supporting lugs are disposed substantially perpendicularly to the panel and extend from respective ones of the four sidewalls. A plurality of integral bosses are disposed substantially perpendicularly to the panel and extend from respective ones of the four sidewalls, with the bosses being shorter than the lugs. In one embodiment, the lugs extend through supporting holes in an annular frame for mounting the liner segments thereto, with the bosses abutting the frame for maintaining a predetermined spacing therefrom.
Halila, Ely E.↗
Structural Analysis Using Computer Based Methods
The stiffness of a flex hose that will be used in the umbilical arms of the Space Launch Systems mobile launcher needed to be determined in order to properly qualify ground umbilical plate behavior during vehicle separation post T-0. This data is also necessary to properly size and design the motors used to retract the umbilical arms. Therefore an experiment was created to determine the stiffness of the hose. Before the test apparatus for the experiment could be built, the structure had to be analyzed to ensure it would not fail under given loading conditions. The design model was imported into the analysis software and optimized to decrease runtime while still providing accurate rest~lts and allow for seamless meshing. Areas exceeding the allowable stresses in the structure were located and modified before submitting the design for fabrication. In addition, a mock up of a deep space habitat and the support frame was designed and needed to be analyzed for structural integrity under different loading conditions. The load cases were provided by the customer and were applied to the structure after optimizing the geometry. Once again, weak points in the structure were located and recommended design changes were made to the customer and the process was repeated until the load conditions were met without exceeding the allowable stresses. After the stresses met the required factors of safety the designs were released for fabrication.
Dietz, Matthew R.↗
Space-Age Shades
Silhouette's Titan Minimal Art frames possess a super elasticity that ensures a slip-free fit for wearing comfort, without causing irritating pressure points. The titanium alloy used in the frames also prevents allergic reactions. This technology is available to both NASA astronauts and public consumers in either corrective eyewear or sunglass models. The only difference between the sunwear used by NASA astronauts and the commercial models is the lens. Silhouette and Dr. Keith Manuel, the "official" optometrist overseeing the NASA Space Shuttle, the International Space Station, and various other vision-related space projects, brought NASA a lens that is considerably darker (5.5 percent overall light transmittance), with a thin gold coating that offers total protection, not only against ultraviolet (UV) radiation, but also against the harmful infrared radiation in space.
Source record↗
Observations of the Celestial Ephemeris Pole
Space-geodetic measurement systems are capable of determining: (1) a terrestrial, body-fixed reference frame defined in practice by the stated positions and secular motions of a set of observing stations, (2) a celestial, space-fixed reference frame defined in practice by the stated locations of celestial objects, and (3) the rotation parameters linking these two frames together.
terrestrial celestial parameters↗