Results for “VECTOR SPACE” — Page 22

NASA NTRS2007

Compact and Rugged Transceiver for Coherent Doppler Wind Lidar Applications in Space

High-accuracy, vertical profiles of the horizontal vector wind in earth s atmosphere, with the global coverage of an orbiting sensor, are a highly desired measurement of NASA, NOAA, and many other agencies and countries. It is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and has recently demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology.

Kavaya, Michael J.↗

NASA NTRS1977

Space Shuttle Solid Rocket booster nozzle flexible seal pivot point dynamics

The NASA Space Shuttle Solid Rocket Motor (SRM) uses an omniaxial flexible seal for vectoring the nozzle. This flexible seal, being built under the technical management of Marshall Space Flight Center in Huntsville, Alabama, is the first ever to be used on a manned spacecraft booster. Since no test history on the particular type of flexible seal being used was available and since flexible seal dynamics characteristics affect many vehicle hardware design and manufacture requirements, a rigorous test program to assess the integrity and operating characteristics of the seal was developed and executed. Vector requirements of the SRM flexible seal and results of subscale and full-scale prototype seal verification tests are included. The advantages of an improved method of calculating actuator stroke versus vector angle and pressure over the more classical method of calculating actuator strokes using pivot point envelopes are discussed. Results presented show that the SRM seal design will satisfy flight requirements.

Gaffin, R. D.↗

NASA NTRSDate not supplied

SelenITA: A dual-spacecraft lunar CubeSat mission to characterize the near-surface electromagnetic plasma environment

SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package. PLAIN LANGUAGE ABSTRACT – SelenITA comes from the greek word for Moon, selene, with the addition of “ITA” as a reference to the Brazilian teammate, Instituto Tecnológico de Aeronáutica. In addition, in Portuguese "ita" is a prefix similar to "ite" in English, used in naming minerals, so Selenita could be seen as a lunar gemstone. In Spanish, “ita” is a diminutive suffix for “little” which is appropriate for this CubeSat mission which consists of twin 12U CubeSats in low lunar orbit. The primary science goal of the mission is to distinguish time varying features within the electromagnetic plasma environment near the surface of the Moon. The science objectives include investigating the origins of crustal magnetic fields, plasma interactions with these fields, plasma waves, surface potential, and interior properties. This mission is also interested in the radiation environment at the Moon and the amount of dust at the lunar poles. This is important because it helps us understand how future astronauts will live and work on the lunar surface and identify hazards.

space weather↗

NASA NTRSDate not supplied

SelenITA: A Dual-Spacecraft Lunar Cubesat Mission to Characterize the Near-Surface Electromagnetic Plasma Environment

SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package.

space weather↗

NASA NTRSDate not supplied

SelenITA: A Dual-Spacecraft Lunar CubeSat Mission to Characterize the Near-Surface Electromagnetic Plasma Environment

SelenITA is an international interdisciplinary mission consisting of two CubeSats that will provide the first multi-point measurement in a sustained low lunar orbit. This mission will advance the understanding of spatiotemporal differentiation of the electromagnetic space environment at the Moon in support of Artemis crew and the geosciences. The mission science objectives are to: (1) further constrain the origins of crustal magnetic fields and their applications; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface potential in all plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include: 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), energetic particles (protons, electrons, gamma rays), and dust. SelenITA builds on a rich history of electromagnetic plasma observations of the near lunar surface and space environment, and it answers high level science questions with state of the art instruments in a small package. PLAIN LANGUAGE ABSTRACT – SelenITA comes from the greek word for Moon, selene, with the addition of “ITA” as a reference to the Brazilian teammate, Instituto Tecnológico de Aeronáutica. In addition, in Portuguese "ita" is a prefix similar to "ite" in English, used in naming minerals, so Selenita could be seen as a lunar gemstone. In Spanish, “ita” is a diminutive suffix for “little” which is appropriate for this CubeSat mission which consists of twin 12U CubeSats in low lunar orbit. The primary science goal of the mission is to distinguish time varying features within the electromagnetic plasma environment near the surface of the Moon. The science objectives include investigating the origins of crustal magnetic fields, plasma interactions with these fields, plasma waves, surface potential, and interior properties. This mission is also interested in the radiation environment at the Moon and the amount of dust at the lunar poles. This is important because it helps us understand how future astronauts will live and work on the lunar surface and identify hazards.

space weather↗

NASA NTRS1993

Modeling of LDEF contamination environment

The Long Duration Exposure Facility (LDEF) satellite was unique in many ways. It was a large structure that was in space for an extended period of time and was stable in orientation relative to the velocity vector. There are obvious and well documented effects of contamination and space environment effects on the LDEF satellite. In order to examine the interaction of LDEF with its environment and the resulting effect on the satellite, the Integrated Spacecraft Environments Model (ISEM) was used to model the LDEF-induced neutral environment at several different times and altitudes during the mission.

Carruth, M. Ralph, Jr.↗

NASA NTRS2000

Quasi-Steady Acceleration Direction Indicator in Three Dimensions

Many materials processing and fluids physics experiments conducted in a microgravity environment require knowledge of the orientation of the low-frequency acceleration vector. This need becomes especially acute for space experiments such as directional solidification of a molten semiconductor, which is extremely sensitive to orientation and may involve tens of hours of operations of a materials furnace. These low-frequency acceleration data have been measured for many Shuttle missions with the Orbital Acceleration Research Experiment. Previous attempts at using fluid chambers for acceleration measurements have met with limited success due to pointing and vehicle attitude complications. An acceleration direction indicator is described, which is comprised of two orthogonal short cylinders of fluid, each with a small bubble. The motion and the position of the bubble within the chamber will indicate the direction of the acceleration experienced at the sensor location. The direction of the acceleration vector may then be calculated from these data. The frequency response of such an instrument may be tailored for particular experiments with the proper selection of fluid and gas parameters, surface type, and geometry. A three-dimensional system for sensing and displaying the low-frequency acceleration direction via an innovative technique described in this paper has advantages in terms of size, mass, and power compared with electronic instrumentation systems.

DeLombard, Richard↗

NASA NTRS1996

Two Reduced Resolution Filter Approaches to Data Assimilation

In this paper we evaluate the performance of two reduced resolution filter approaches to data assimilation. The main distinction between these approaches is in the manner they propagate error covariances. Both account for error covariances in a space with dimension m smaller than the model's state vector dimension n. In the first approach the m dimensional error covariance matrix is interpolated to the n-dimensional space and propagated with the n-dimensional dynamics. In the second approach the low-dimensional error covariance matrix is propagated by a dynamical operator generated in the m-dimensional space. Our experiments indicate that the first approach provides a more reliable simplified scheme for error covariance propagation than the second approach.

Todling, Ricardo↗

NASA NTRS1974

Derivation of formulas for root-mean-square errors in location, orientation, and shape in triangulation solution of an elongated object in space

Formulas are derived for the root-mean-square (rms) displacement, slope, and curvature errors in an azimuth-elevation image trace of an elongated object in space, as functions of the number and spacing of the input data points and the rms elevation error in the individual input data points from a single observation station. Also, formulas are derived for the total rms displacement, slope, and curvature error vectors in the triangulation solution of an elongated object in space due to the rms displacement, slope, and curvature errors, respectively, in the azimuth-elevation image traces from different observation stations. The total rms displacement, slope, and curvature error vectors provide useful measure numbers for determining the relative merits of two or more different triangulation procedures applicable to elongated objects in space.

Long, S. A. T.↗

NASA NTRS1982

On the possibility of detecting large-scale crustal remanent magnetization with Magsat vector magnetic anomaly data

Magnetic anomaly component data measured by Magsat is compared with synthetic anomaly component fields arising from an equivalent source dipole array at the earth's surface generated from total field anomaly data alone. It is found that the synthetic components fit the component data regardless of the dipole orientation assigned to the equivalent sources and of the dipole spacing. Tentative conclusions are: (1) over the U.S., vector anomaly fields can be determined to the accuracy of the measurements from the total field anomaly data alone; and (2) the equivalent source technique is not useful for determining the direction of large-scale crustal magnetization.

Galliher, S. C.↗

NASA NTRSDate not supplied

Structural Dynamics Observations in Space Launch System Green Run Hot Fire Testing

The Space Launch System (SLS) Core Stage (CS) Thrust Vector Control (TVC) system is comprised of eight mechanical feedback Shuttle heritage Type III TVC actuators and four RS-25 engines, each attached to a Shuttle heritage gimbal block/bearing. Two actuators are used to move each engine in two planes perpendicular to one another (i.e., pitch and yaw). The TVC system design leverages hardware from the Space Shuttle program as well as new hardware designed specifically for the Core Stage. The Green Run Hot Fire (GRHF) of the SLS Core Stage provided a flight-like ground test environment for verification of integrated vehicle TVC performance. A TVC model coupled to a vehicle structural dynamic model has been developed previously and incrementally validated in subsystem tests and simulations. Still, some aspects of TVC performance in GRHF were not anticipated. The ensuing investigation demonstrated the need for well-instrumented test environments, various levels of modeling fidelity, test-representative structural models, and caution in reuse of legacy components. This paper is the sixth installment in a seven-paper series surveying the design, engineering, test validation, and flight performance of the Core Stage Thrust Vector Control system. It introduces the salient structural dynamic phenomena uncovered in ambient and hot fire testing. During the Green Run test campaign, a comparison of ambient and hot fire step responses showed a significant change in apparent damping due to the presence of friction, challenging long standing assumptions that friction could be neglected. Additionally, the characteristic response of the engine and thrust structure during GRHF proved to be more complex than anticipated, as evidenced by the available actuator, thrust structure, and engine measurements. While the string-potentiometer based test instrumentation was intended to allow for reconstruction of the engine angles along the two control axes, the geometric placement, location uncertainty, and responses in overlapping frequency spectra revealed additional phenomena requiring further analysis and post-processing. The observations from both modal and frequency response testing during the Green Run ambient and hot fire configurations led to Engine and Core Stage FEM (finite element model) updates. When evidence of unexpected engine motion was found in engine section accelerometer data, the authors pursued additional structural analysis leading to FEM updates associated with the TVC gimbal and thrust structure. Through collaboration between structures, TVC, and flight control disciplines, the test-informed models and root-cause analysis led to confident flight rationale for the first flight of the SLS launch vehicle.

Richard K. Moore↗

NASA NTRSDate not supplied

Structural Dynamics Observations in Space Launch System Green Run Hot Fire Testing

The Space Launch System (SLS) Core Stage (CS) Thrust Vector Control (TVC) system is comprised of eight mechanical feedback Shuttle heritage Type III TVC actuators and four RS-25 engines, each attached to a Shuttle heritage gimbal block/bearing. Two actuators are used to move each engine in two planes perpendicular to one another (i.e., pitch and yaw). The TVC system design leverages hardware from the Space Shuttle program as well as new hardware designed specifically for the Core Stage. The Green Run Hot Fire (GRHF) of the SLS Core Stage provided a flight-like ground test environment for verification of integrated vehicle TVC performance. A TVC model coupled to a vehicle structural dynamic model has been developed previously and incrementally validated in subsystem tests and simulations. Still, some aspects of TVC performance in GRHF were not anticipated. The ensuing investigation demonstrated the need for well-instrumented test environments, various levels of modeling fidelity, test-representative structural models, and caution in reuse of legacy components. This paper is the sixth installment in a seven-paper series surveying the design, engineering, test validation, and flight performance of the Core Stage Thrust Vector Control system. It introduces the salient structural dynamic phenomena uncovered in ambient and hot fire testing. During the Green Run test campaign, a comparison of ambient and hot fire step responses showed a significant change in apparent damping due to the presence of friction, challenging long standing assumptions that friction could be neglected. Additionally, the characteristic response of the engine and thrust structure during GRHF proved to be more complex than anticipated, as evidenced by the available actuator, thrust structure, and engine measurements. While the string-potentiometer based test instrumentation was intended to allow for reconstruction of the engine angles along the two control axes, the geometric placement, location uncertainty, and responses in overlapping frequency spectra revealed additional phenomena requiring further analysis and post-processing. The observations from both modal and frequency response testing during the Green Run ambient and hot fire configurations led to Engine and Core Stage FEM (finite element model) updates. When evidence of unexpected engine motion was found in engine section accelerometer data, the authors pursued additional structural analysis leading to FEM updates associated with the TVC gimbal and thrust structure. Through collaboration between structures, TVC, and flight control disciplines, the test-informed models and root-cause analysis led to confident flight rationale for the first flight of the SLS launch vehicle.

Richard Moore↗

DOE OSTI2024

Collocation methods for nonlinear differential equations on low-rank manifolds

We introduce new methods for integrating nonlinear differential equations on low-rank manifolds. These methods rely on interpolatory projections onto the tangent space, enabling low-rank time integration of vector fields that can be evaluated entry-wise. A key advantage of our approach is that it does not require the vector field to exhibit low-rank structure, thereby overcoming significant limitations of traditional dynamical low-rank methods based on orthogonal projection. To construct the interpolatory projectors, we develop a sparse tensor sampling algorithm based on the discrete empirical interpolation method (DEIM) that parameterizes tensor train manifolds and their tangent spaces with cross interpolation. Using these projectors, we propose two time integration schemes on low-rank tensor train manifolds. The first scheme integrates the solution at selected interpolation indices and constructs the solution with cross interpolation. The second scheme generalizes the well-known orthogonal projector-splitting integrator to interpolatory projectors. We demonstrate the proposed methods with applications to several tensor differential equations arising from the discretization of partial differential equations.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1984

Riemann Curvature tensor in nonholonomic coordinates and non-Riemannian space-times

The calculation of the Riemann Curvature from the deviation of a vector undergoing parallel transport around a closed loop takes a very simple form when expressed in generalized geometrical notation. The parallel transport of a vector and the type of closed loop used in the calculation are discussed. The method generalizes similar work of Morganstern (1977) to nonholonomic coordinates and non-Riemannian space-times.

Smalley, L. L.↗

NASA NTRSDate not supplied

Core Stage TVC Systems Engineering Challenges in Reusing Heritage Hardware

The Space Launch System (SLS) Core Stage (CS) Thrust Vector Control (TVC) system is comprised of 8 mechanical feedback Shuttle heritage Type III TVC actuators and four RS-25 engines, each attached to a Shuttle heritage gimbal block/bearing. Two actuators are used to move each engine in two planes perpendicular to one another (i.e., pitch and yaw). The TVC system design leverages hardware from the Space Shuttle program as well as new hardware designed specifically for the Core Stage. The Space Shuttle heritage hardware directly reused on SLS includes the Orbiter TVC hydraulic servo-actuators (with two slight design modifications), the Orbiter hydraulic circulation pumps, the Orbiter gimbal block/bearing, and the Solid Rocket Booster hydraulic pumps. The Core Auxiliary Power Unit (CAPU) is derived from the Orbiter Auxiliary Power Unit (APU). The Orbiter and Solid Rocket Booster APU turbines are powered by hot gas produced by catalyzed hydrazine decomposition. On the SLS Core Stage, the CAPU turbine is spun using cold gas tapped-off from the RS-25 to CS liquid hydrogen autogenous pressurization line. While direct reuse or slight modification of existing hardware may seem to be a triple-win for a program in cost, schedule, and technical risk mitigation, those benefits can only be realized when its degree of application in a new system is carefully and thoughtfully managed. The heritage hardware reuse should be prescribed within the heritage design capability and reuse environments must lie within the envelope of heritage qualification testing. Despite the significant test and flight experience of the Shuttle heritage hardware components, successful integration with the newly designed CS TVC components and incorporation into the stage design proved to be a challenge which required re-qualification of the heritage hardware as well as thorough integrated testing to support flight certification. Examples of the challenges that were overcome include: re-qualifying heritage hardware to survive new shock and vibration environments, certifying performance of extensively modified heritage hardware, regenerating design insight due to lack of available heritage vendor data, showing compliance to modern structural design standards, translation of heritage requirements for analog avionics to modern digital avionics, and interfacing heritage mechanical hardware with newly designed avionics. This paper is the second installment in a seven-paper series surveying the design, engineering, test validation, and flight performance of the Core Stage Thrust Vector Control system. This paper will discuss several engineering challenges encountered during the development process for SLS CS TVC and how they were successfully overcome to reach flight readiness.

Thrust Vector Control↗

NASA NTRS1988

Real-time optical laboratory solution of parabolic differential equations

An optical laboratory matrix-vector processor is used to solve parabolic differential equations (the transient diffusion equation with two space variables and time) by an explicit algorithm. This includes optical matrix-vector nonbase-2 encoded laboratory data, the combination of nonbase-2 and frequency-multiplexed data on such processors, a high-accuracy optical laboratory solution of a partial differential equation, new data partitioning techniques, and a discussion of a multiprocessor optical matrix-vector architecture.

Casasent, David↗

NASA NTRS1995

Blending Velocities In Task Space In Computing Robot Motions

Blending of linear and angular velocities between sequential specified points in task space constitutes theoretical basis of improved method of computing trajectories followed by robotic manipulators. In method, generalized velocity-vector-blending technique provides relatively simple, common conceptual framework for blending linear, angular, and other parametric velocities. Velocity vectors originate from straight-line segments connecting specified task-space points, called "via frames" and represent specified robot poses. Linear-velocity-blending functions chosen from among first-order, third-order-polynomial, and cycloidal options. Angular velocities blended by use of first-order approximation of previous orientation-matrix-blending formulation. Angular-velocity approximation yields small residual error, quantified and corrected. Method offers both relative simplicity and speed needed for generation of robot-manipulator trajectories in real time.

Volpe, Richard A.↗

NASA NTRS1981

Investigation of electrodynamic stabilization and control of long orbiting tethers

An algorithm for using electric currents to control pendular oscillations induced by various perturbing forces on the Skyhook wire is considered. Transverse and vertical forces on the tether; tether instability modes and causes during retrieval by space shuttle; simple and spherical pendulum motion and vector damping; and current generation and control are discussed. A computer program for numerical integration of the in-plane and out-of-plane displacements of the tether vs time was developed for heuristic study. Some techniques for controlling instabilities during payload retrieval and methods for employing the tether for launching satellites from the space shuttle are considered. Derivations and analyses of a general nature used in all of the areas studied are included.

Arnold, D. A.↗