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David Cox

Publications and source records attributed to David Cox.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Space Magnets Attracting Interest on Earth: Applications of Physical and Biological Techniques In the Study of Gravisensing and Response System of Plants

The BioTube/Magnetic Field Apparatus (MFA) research is designed to provide insight into the organization and operation of the gravity sensing systems of plants and other small organisms. This experiment on STS-107 uses magnetic fields to manipulate sensory cells in plant roots, thus using magnetic fields as a tool to study gravity-related phenomena. The experiment will be located in the SPACEHAB module and is about the size of a household microwave oven. The goal of the experiment is to improve our understanding of the basic phenomenon of how plants respond to gravity. The BioTube/MFA experiment specifically examines how gravitational forces serve as a directional signal for growth in the low-gravity environment of space. As with all basic research, this study will contribute to an improved understanding of how plants grow and will have important implications for improving plant growth and productivity on Earth. In BioTube/MFA, magnetic fields will be used to determine whether the distribution of subcellular starch grains, called amyloplasts, within plant cells predicts the direction in which roots will grow and curve in microgravity.

Karl H Hasenstein↗
NASA NTRSDate not supplied

TPSAS-NF1676L-12076-DND

AirSTAR is the collection of Ground Support Systems, Subscale Flight Vehicles and Operations Expertise required for conducting remotely piloted flight-dynamics and controls research.

David Cox↗
NASA NTRSDate not supplied

Preliminary Measurement of Pitch Damping of Blunt Entry Vehicles in a Subsonic Magnetic Suspension Wind Tunnel

Blunt bodies have been magnetically suspended in a 6-inch octagonal test-section low-subsonic wind tunnel in a free-to oscillate configuration. Capsule oscillations of two entry vehicle geometries were measured from high speed video of repeated test runs. An analytical solution to the 1degree-of-freedom equations of motion was fit to the measured oscillation histories to solve for a pitch damping coefficient. A six degree-of-freedom simulation was used to predict the wind tunnel data and assess the effect of magnetic forces on capsule dynamics. The predicted effect was used in the data reduction methodology to improved the pitch damping measurement. Pitch damping measurements are compared with heritage forced oscillation data and are in good agreement. Preliminary uncertainties are included with recommendations for improved data reduction.

Dynamic Stability↗
NASA NTRSDate not supplied

Uncertainty Analysis of the Pitch Damping Coefficient of Blunt Bodies, Measured from Magnetic Suspension Wind Tunnel Tests

Blunt body aerodynamics in re-entry conditions are characterized by oscillatory behavior that is often encapsulated by the pitch damping coefficient (Cmq). Magnetic Suspension Wind Tunnel (MSWT) testing with a Magnetic Suspension Balance System (MSBS) aims to improve blunt body wind tunnel testing by removing the sometimes unknown aerodynamic effects of traditional sting mounts, as well as generate more constrained outputs than vertical spin tunnel testing. Efforts to calculate the uncertainty of the pitch damping coefficient with a proposed Earth Entry Vehicle (EEV) capsule model have been made by fitting an analytic prediction of the attitude time history to video data of a free-to-oscillate MSBS test.

Magnetic suspension, dynamic stability, uncertaint↗
NASA NTRSDate not supplied

Blunt Body Pitch Damping Measurements from Multiple Subsonic Free-to-Pitch Magnetic Suspension Trials

The yaw damping coefficients of two blunt entry vehicle models, measured from free-to-oscillate tests in the ODU/NASA subsonic magnetic suspension wind tunnel are presented. Multiple repeat trials were conducted for both models. Two separate data reduction methods were used to extract damping coefficients and yaw moment slope. Both methods identified similar damping and stability values, with differences being consistent with their known limitations.

magnetic suspension↗
NASA NTRSDate not supplied

Preliminary Measurement of Pitch Damping of Blunt Entry Vehicles in a Subsonic Magnetic Suspension Wind Tunnel

The yaw damping coefficients of two blunt entry vehicle models, measured from free-to-oscillate tests in the ODU/NASA subsonic magnetic suspension wind tunnel are presented. Multiple repeat trials were conducted for both models. Two separate data reduction methods were used to extract damping coefficients and yaw moment slope. Both methods identified similar damping and stability values, with differences being consistent with their known limitations.

magnetic suspension↗
NASA NTRSDate not supplied

An Investigation of Bluff Body Corrections Using the NASA/ODU 6-inch MSBS

Spheres of different diameters were tested in the NASA/ODU 6-inch Magnetic Suspension Balance System (MSBS). The objective is to develop an improved understanding of blockage corrections to be made to other bluff-body geometries. Drag coefficients are shown with classical corrections applied, along with wall pressure signatures and base pressure measurements. Anomalous behavior was observed with the largest diameter, thought to be some form of flow breakdown, hence uncorrectable interference.

magnetic suspension↗
NASA NTRSDate not supplied

Comparison of Dynamic Stability Testing Techniques with Magnetic Suspension Wind Tunnel

Dynamic stability testing techniques currently utilized at NASA Langley Research Center (LaRC) are conducted in multiple facilities and consists of free flight, forced oscillation, and free-to-oscillate tests. The MIT/NASA/ODU Magnetic Suspension and Balance System (MSBS) has been recommissioned to explore its utility as an additional facility to expand the dynamic stability test capabilities currently available at NASA LaRC. Simulations were created to replicate each current test facility and method as closely as possible. Data collected from the simulated environments was corrupted with replicated noise sources of the different testing environments and then compared to real data collected during tests when such data was available. The corrupted data was then passed through data reduction and System Identification (SID) to estimate the accuracy of the results with the known aerodynamic model that was utilized within the simulation to generate the original data. Magnitudes of noise were varied utilizing Monte Carlo analysis to perform sensitivity analysis of each noise source on the extracted dynamic stability coefficients. Some preliminary results will be presented.

Otoniel Ramirez↗
NASA NTRSDate not supplied

Increasing the Dynamic Pressure Capability of the NASA Langley/ODU 6-inch MSBS

The 6-inch NASA/ODU Magnetic Suspension and Balance System (MSBS) has been configured for dynamic stability testing of blunt-body atmospheric entry capsules. Tests have been successfully accomplished in the low-speed, open-circuit wind tunnel, at speeds up to around 40 m/s. The wind tunnel is designed to reach around 150 m/s, resulting in dynamic pressures comparable to those projected to arise in a future supersonic MSBS facility. Extensive system upgrades are being undertaken to permit testing at higher speeds/dynamic pressures, including control system enhancements, revised position and attitude sensing, and activation of additional electromagnets in the existing array. This paper will review recent progress in all these areas.

Mark Schoenenberger↗
NASA NTRSDate not supplied

The Feasibility of Motion Tracking Camera System for Magnetic Suspension Wind Tunnel Tests

The Entry Systems Modeling (ESM) Program at NASA has actively participated in the re-development of the Magnetic Suspension Balance System (MSBS) at the six-inch subsonic wind tunnel at NASA Langley Research Center. This initiative aims to enhance the MSBS system's capabilities, enabling the testing of stingless entry vehicle models at supersonic speeds. To achieve this, control algorithms are required to ensure magnetic levitation control and stability for models during free-oscillation dynamic responses. Currently, the system relies on electromagnetic position sensors to provide real-time 3 degrees of freedom in a rigid body. While this approach has proven successful for subsonic speeds, expanding testing under higher pressure conditions may necessitate the incorporation of real-time roll and pitch measurements to quantify the dynamic stability characteristics of the models in free-oscillation. In collaboration with Old Dominion University, the team at NASA Langley Research Center proposes the implementation of a motion-tracking camera system. This system will provide real-time five degrees of freedom output, which will be utilized within a closed feedback control system and a two-step system identification model to isolate aerodynamic forces from their corresponding magnetic forces. The motion-tracking cameras will offer precise and accurate control over the levitation system, facilitating precise and repeatable experiments within the wind tunnel. The real-time feedback provided by the cameras enables prompt adjustments to ensure the maintenance of stable levitation throughout the testing process.

Entry Systems Modeling↗
NASA NTRSDate not supplied

Development of the X-57 Mod III/IV Piloted Simulator and Discussion of the Resultant Flighting Qualities Predictions

The all-electric X-57 Mod III aircraft was designed to demonstrate wingtip propulsion drag reduction benefits on a high-aspect-ratio wing. The X-57 Mod IV aircraft was designed to expand on the Mod III version and demonstrate the benefits of distributed electric propulsion. This paper discusses the development of theall-electricX-57 Mod III and Mod IV fixed-base pilot-in-the-loop nonlinear simulator. The paper describes the model development and the simulator cockpit construction for uses such as flight training and flying qualities analysis. Results from a stability and flying qualities analysis for both Mod III and Mod IV are presented. These results predict that both Mod III and Mod IV are stable throughout their flight envelopes. Mod III is predicted to have satisfactory flying qualities while Mod IV is predicted to have areas of adequate flying qualities.

Ryan Wallace↗
NASA NTRSDate not supplied

Comprehensive Static and Dynamic Modeling of a Magnetic Suspension and Balance System

Magnetic Suspension and Balance Systems (MSBS) are inherently complex multi-degree-of-freedom dynamic systems. Comprehensive, high-fidelity dynamic models are increasingly important due to the application of model-based controllers as well as demands for unsteady aerodynamic data derived from post-test system identification. This paper reviews some aspects of the development of a dynamic model of the NASA/ODU 6-inch MSBS.

blunt body↗
NASA NTRSDate not supplied

Forced Displacement Technique for Measuring Blunt Body Aerodynamics in a Magnetic Suspension Wind Tunnel

The Old Dominion University/NASA Langley 6-Inch Magnetic Suspension Wind Tunnel has developed the ability to levitate blunt bodies which can oscillate freely about the yaw axis. This allows for the measurement of static and dynamic stability coefficients without sting interference. The magneic suspension controller introduces other translational forces which affect the vehicle dynamics complicating data reduction. Exciting model oscillations in a reliable way has also been a challenge. A new test method has been developed that produces capsule oscillations from forced oscillatory translational motion at the resonant yaw oscillatory frequency of the capsule. After oscillations are excited, the translational forcing motion is suspended to record free oscillation behavior as well. A data reduction method whereby a linear model of the translational and oscillatory motion is used to fit to the measured data and solve for aerodynamic coefficients has also been developed. The work presented shows that the new data reduction

blunt body↗
NASA NTRSDate not supplied

Forced Displacement Technique for Measuring Blunt Body Aerodynamics in a Magnetic Suspension Wind Tunnel

The Old Dominion University/NASA Langley 6-Inch Magnetic Suspension Wind Tunnel has developed the ability to levitate blunt bodies which can oscillate freely about the yaw axis. This allows for the measurement of static and dynamic stability coefficients without sting interference. The magneic suspension controller introduces other translational forces which affect the vehicle dynamics complicating data reduction. Exciting model oscillations in a reliable way has also been a challenge. A new test method has been developed that produces capsule oscillations from forced oscillatory translational motion at the resonant yaw oscillatory frequency of the capsule. After oscillations are excited, the translational forcing motion is suspended to record free oscillation behavior as well. A data reduction method whereby a linear model of the translational and oscillatory motion is used to fit to the measured data and solve for aerodynamic coefficients has also been developed. The work presented shows that the new data reduction

blunt body↗