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NASA NTRS2015

Marshall Space Flight Center Faculty Fellowship Program

The Faculty Fellowship program was revived in the summer of 2015 at NASA Marshall Space Flight Center, following a period of diminished faculty research activity here since 2006 when budget cuts in the Headquarters' Education Office required realignment. Several senior Marshall managers recognized the need to involve the Nation's academic research talent in NASA's missions and projects to the benefit of both entities. These managers invested their funds required to establish the renewed Faculty Fellowship program in 2015, a 10-week residential research involvement of 16 faculty in the laboratories and offices at Marshall. These faculty engineers and scientists worked with NASA collaborators on NASA projects, bringing new perspectives and solutions to bear. This Technical Memorandum is a compilation of the research reports of the 2015 Marshall Faculty Fellowship program, along with the Program Announcement (appendix A) and the Program Description (appendix B). The research touched on seven areas-propulsion, materials, instrumentation, fluid dynamics, human factors, control systems, and astrophysics. The propulsion studies included green propellants, gas bubble dynamics, and simulations of fluid and thermal transients. The materials investigations involved sandwich structures in composites, plug and friction stir welding, and additive manufacturing, including both strength characterization and thermosets curing in space. The instrumentation projects involved spectral interfero- metry, emissivity, and strain sensing in structures. The fluid dynamics project studied the water hammer effect. The human factors project investigated the requirements for close proximity operations in confined spaces. Another team proposed a controls system for small launch vehicles, while in astrophysics, one faculty researcher estimated the practicality of weather modification by blocking the Sun's insolation, and another found evidence in satellite data of the detection of a warm-hot intergalactic medium filament. Our goal is to continue the Faculty Fellowship effort with Center funds in succeeding summers.

Six, N. F.↗
NASA NTRS2007

Comparison Between Simulated and Experimentally Measured Performance of a Four Port Wave Rotor

Performance and operability testing has been completed on a laboratory-scale, four-port wave rotor, of the type suitable for use as a topping cycle on a gas turbine engine. Many design aspects, and performance estimates for the wave rotor were determined using a time-accurate, one-dimensional, computational fluid dynamics-based simulation code developed specifically for wave rotors. The code follows a single rotor passage as it moves past the various ports, which in this reference frame become boundary conditions. This paper compares wave rotor performance predicted with the code to that measured during laboratory testing. Both on and off-design operating conditions were examined. Overall, the match between code and rig was found to be quite good. At operating points where there were disparities, the assumption of larger than expected internal leakage rates successfully realigned code predictions and laboratory measurements. Possible mechanisms for such leakage rates are discussed.

Paxson, Daniel E.↗
NASA NTRS1993

Admittance model for the shuttle remote manipulator system in four configurations

A possible scenario for robot task performance in space is to mount two small, dexterous arms to the end of the Shuttle Remote Manipulator System (SRMS). As these small robots perform tasks, the flexibility of the SRMS may cause unsuccessful task executions. In order to simulate the dynamic coupling between the SRMS and the arms, admittance models of the SRMS in four brakes locked configurations were developed. The admittance model permits calculation of the SRMS end-effector response due to end-effector disturbing forces. The model will then be used in conjunction with a Stewart Platform, a vehicle emulation system. An application of the admittance model was shown by simulating the disturbing forces using two SRMS payloads, the Dextrous Orbital Servicing System (DOSS) manipulator and DOSS carrying a 1000 lb. cylinder. Mode by mode comparisons were conducted to determine the minimum number of modes required in the admittance model while retaining dynamic fidelity. It was determined that for all four SRMS configurations studied, between 4 and 6 modes of the SRMS structure (depending on the excitation loads) were sufficient to retain tolerance of 0.01 inches and 0.01 deg. These tolerances correspond to the DOSS manipulator carrying no object. When the DOSS carries the 1000 lb. cylinder, between 15 and 20 modes were sufficient, approximately three or four times as many modes as for the unloaded case.

Papadopoulos, Loukas↗
NASA NTRS2012

Small Radioisotope Power System at NASA Glenn Research Center

In April 2009, NASA Glenn Research Center (GRC) formed an integrated product team (IPT) to develop a Small Radioisotope Power System (SRPS) utilizing a single Advanced Stirling Convertor (ASC) with passive balancer for possible use by the International Lunar Network (ILN) program. The ILN program is studying the feasibility of implementing a multiple node seismometer network to investigate the internal lunar structure. A single ASC produces approximately 80 W(sub e) and could potentially supply sufficient power for that application. The IPT consists of Sunpower, Inc., to provide the single ASC with balancer, The Johns Hopkins University Applied Physics Laboratory (JHU/APL) to design an engineering model Single Convertor Controller (SCC) for an ASC with balancer, and NASA GRC to provide technical support to these tasks and to develop a simulated lunar lander test stand. A controller maintains stable operation of an ASC. It regulates the alternating current produced by the linear alternator of the convertor, provides a specified output voltage, and maintains operation at a steady piston amplitude and hot end temperature. JHU/APL also designed an ASC dynamic engine/alternator simulator to aid in the testing and troubleshooting of the SCC. This paper describes the requirements, design, and development of the SCC, including some of the key challenges and the solutions chosen to overcome those issues. In addition, it describes the plans to analyze the effectiveness of a passive balancer to minimize vibration from the ASC, characterize the effect of ASC vibration on a lunar lander, characterize the performance of the SCC, and integrate the single ASC, SCC, and lunar lander test stand to characterize performance of the overall system.

Dugala, Gina M.↗
NASA NTRS1984

Functional evaluation of the Galileo attitude and articulation control subsystem using FUNSIM

The functional performance of the Galileo spacecraft's attitude and articulation control subsystem is evaluated. The tests are performed utilizing the simulation program developed on an IBM 370 system known as the Functional Simulation (FUNSIM). FUNSIM is an entirely software-based simulation which uses the actual flight software in HAL/S and simulated spacecraft dynamics in FORTRAN language. A description of how the test cases were selected to verify that the algorithms perform functionally correctly, and a summary of the problems encountered are included in the paper. The benefits of having an alternative test bed such as FUNSIM to the real-time simulation test beds which utilize the spacecraft hardware components in discovering the problems are described. A sample test case which shows that the desired tasks were performed functionally correctly is included in the paper. The commands in this test are selected to start the dual-spin spacecraft initially in launch mode and lead it all the way to inertial mode. Major attitude control algorithms such as rotor and platform attitude estimators, clock and core platform attitude estimators, clock and core platform controllers, and the command turn and burn are examined.

Namiri, M. K.↗
NASA NTRS1987

Simulation investigation of the effects of helicopter hovering dynamics on pilot performance

A fixed base simulation has been performed to investigate the handling qualities requirements for the mid-term pitch response of a helicopter at hover and in low-speed flight. Pilot rating results from this simulation were compared with those from previous experiments to develop handling qualities limits on the frequency and damping of the oscillatory mode in the hovering cubic. Pilot performance data obtained during the experiment were used to confirm the pilot rating results. These data show the pilot performance to closely match that predicted by the theory of piloted control. A means of predicting pilot ratings from the open-loop aircraft dynamics is presented.

Aponso, Bimal L.↗
NASA NTRS1987

Space Station/Shuttle Orbiter dynamics during docking

Mathematical models of a reference space station configuration (Power Tower) and a Space Shuttle Orbiter are developed and used to study the dynamic behavior of the Space Station/Orbiter system just prior to and subsequent to an impulsive docking of the two spacecraft. The physical model of the space station is a collection of rigid and flexible bodies. The orbiter is modeled as a rigid body. An algorithm developed for use in digitally simulating the dynamics of the system is described and results of its application are presented.

Fitz-Coy, N. G.↗
NASA NTRS1993

Transfer of training for aerospace operations: How to measure, validate, and improve it

It has been a commonly accepted practice to train pilots and astronauts in expensive, extremely sophisticated, high fidelity simulators, with as much of the real-world feel and response as possible. High fidelity and high validity have often been assumed to be inextricably interwoven, although this assumption may not be warranted. The Project Mercury rate-damping task on the Naval Air Warfare Center's Human Centrifuge Dynamic Flight Simulator, the shuttle landing task on the NASA-ARC Vertical Motion Simulator, and the almost complete acceptance by the airline industry of full-up Boeing 767 flight simulators, are just a few examples of this approach. For obvious reasons, the classical models of transfer of training have never been adequately evaluated in aerospace operations, and there have been few, if any, scientifically valid replacements for the classical models. This paper reviews some of the earlier work involving transfer of training in aerospace operations, and discusses some of the methods by which appropriate criteria for assessing the validity of training may be established.

Cohen, Malcolm M.↗
NASA NTRS2012

End-To-End Simulation of Launch Vehicle Trajectories Including Stage Separation Dynamics

The development of methodologies, techniques, and tools for analysis and simulation of stage separation dynamics is critically needed for successful design and operation of multistage reusable launch vehicles. As a part of this activity, the Constraint Force Equation (CFE) methodology was developed and implemented in the Program to Optimize Simulated Trajectories II (POST2). The objective of this paper is to demonstrate the capability of POST2/CFE to simulate a complete end-to-end mission. The vehicle configuration selected was the Two-Stage-To-Orbit (TSTO) Langley Glide Back Booster (LGBB) bimese configuration, an in-house concept consisting of a reusable booster and an orbiter having identical outer mold lines. The proximity and isolated aerodynamic databases used for the simulation were assembled using wind-tunnel test data for this vehicle. POST2/CFE simulation results are presented for the entire mission, from lift-off, through stage separation, orbiter ascent to orbit, and booster glide back to the launch site. Additionally, POST2/CFE stage separation simulation results are compared with results from industry standard commercial software used for solving dynamics problems involving multiple bodies connected by joints.

Albertson, Cindy W.↗
NASA NTRSDate not supplied

Supersonic External-Compression Inlets for Mach 1.4 to 2.0

A series of supersonic, external-compression inlets were designed for freestream Mach numbers of Mach 1.4, 1.7, and 2.0. The types of inlets included axisymmetric pitot, axisymmetric spike, two-dimensional, two-dimensional bifurcated, and streamline-traced inlets. The inlets were designed as isolated from an aircraft with freestream conditions, engine-face geometry, and flow rates established from a reference NASA commercial aircraft concept. The inlets were designed using the NASA Supersonic Inlet Design and Analysis (SUPIN) Tool and the inlet performance was obtained from computational fluid dynamics (CFD) simulations. The study compares the physical dimensions and aerodynamic performance of the inlets to provide reference information for the selection of inlet types for commercial supersonic aircraft.

Supersonics↗
NASA NTRSDate not supplied

Supersonic External-Compression Inlets for Mach 1.4 to 2.0

A series of supersonic, external-compression inlets were designed for freestream Mach numbers of Mach 1.4, 1.7, and 2.0. The types of inlets included axisymmetric pitot, axisymmetric spike, two-dimensional, two-dimensional bifurcated, and streamline-traced inlets. The inlets were designed as isolated from an aircraft with freestream conditions, engine-face geometry, and flow rates established from a reference NASA commercial aircraft concept. The inlets were designed using the NASA Supersonic Inlet Design and Analysis (SUPIN) Tool and the inlet performance was obtained from computational fluid dynamics (CFD) simulations. The study compares the physical dimensions and aerodynamic performance of the inlets to provide reference information for the selection of inlet types for commercial supersonic aircraft.

Supersonics↗
NASA NTRS2002

Dynamic Modeling of ALS Systems

The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.

Jones, Harry↗
NASA NTRS1973

Results of solar electric thrust vector control system design, development and tests

Efforts to develop and test a thrust vector control system TVCS for a solar-energy-powered ion engine array are described. The results of solar electric propulsion system technology (SEPST) III real-time tests of present versions of TVCS hardware in combination with computer-simulated attitude dynamics of a solar electric multi-mission spacecraft (SEMMS) Phase A-type spacecraft configuration are summarized. Work on an improved solar electric TVCS, based on the use of a state estimator, is described. SEPST III tests of TVCS hardware have generally proved successful and dynamic response of the system is close to predictions. It appears that, if TVCS electronic hardware can be effectively replaced by control computer software, a significant advantage in control capability and flexibility can be gained in future developmental testing, with practical implications for flight systems as well. Finally, it is concluded from computer simulations that TVCS stabilization using rate estimation promises a substantial performance improvement over the present design.

Fleischer, G. E.↗
NASA NTRS2010

Data-Flow Based Model Analysis

The concept of (meta) modeling combines an intuitive way of formalizing the structure of an application domain with a high expressiveness that makes it suitable for a wide variety of use cases and has therefore become an integral part of many areas in computer science. While the definition of modeling languages through the use of meta models, e.g. in Unified Modeling Language (UML), is a well-understood process, their validation and the extraction of behavioral information is still a challenge. In this paper we present a novel approach for dynamic model analysis along with several fields of application. Examining the propagation of information along the edges and nodes of the model graph allows to extend and simplify the definition of semantic constraints in comparison to the capabilities offered by e.g. the Object Constraint Language. Performing a flow-based analysis also enables the simulation of dynamic behavior, thus providing an "abstract interpretation"-like analysis method for the modeling domain.

Saad, Christian↗
NASA NTRSDate not supplied

Generalized Predictive Control for Active Stability Augmentation and Vibration Reduction on an Aeroelastic Tiltrotor Model

Tiltrotor aircraft are defining the state-of-the-art in vertical lift technology as they have the potential to greatly expand rotary-wing operational boundaries. However, they are often limited in forward flight speed due to complex coupled rotor and wing dynamic instabilities. The U.S. Army and NASA have been developing a new wind tunnel model, the TiltRotor Aeroelastic Stability Testbed(TRAST), to test proprotors in the NASA Langley Research Center Transonic Dynamics Tunnel (TDT) to investigate aeroelastic stability in cruise. The test is intended to provide high-quality research data for analytical tool development and validation. In addition, the TRAST model will support, develop, and mature new technologies for the design of advanced proprotor aircraft. Stability augmentation and vibration reduction during testing is planned with the use of an active control methodology known as Generalized Predictive Control(GPC). GPC is an autoregressive control law that experimentally acquires a system identification to derive the input-output relation of controls and corresponding sensors. This type of control law is especially useful for complex dynamic interactions that are difficult to explicitly model such as proprotor pylon instability, often referred to as whirl flutter. GPC has been successfully employed on other tiltrotor vehicles to suppress whirl flutter instabilities and vibrations. To aid in the characterization of the wind-tunnel model and in tool development, an analytical representation of the wind-tunnel model was developed using the rotorcraft comprehensive analysis system (RCAS) that simulates structural dynamics and aerodynamics. RCAS was used to derive state-space estimates of the physical plant at various flight conditions to test control law effectiveness. This paper will present an overview of the test article development, a description of RCAS, an explanation of the GPC methodology, and results of GPC being applied to state-space plant estimates of the TRAST model. In these simulations, GPC was effective at stabilizing the aircraft beyond the whirl-flutter boundary while simultaneously reducing vibrations across the flight regime. Additionally, a modern advancement to GPC, termed advanced GPC (AGPC), is introduced that enables a self-adapting system identification. Preliminary results show that AGPC is successful at self-correction as the plant changes from what was used for system identification.

tiltrotor↗
NASA NTRSDate not supplied

Plant Watering in Low Gravity: The Study of the Fluid Dynamic Characteristics of Lunar Regolith Simulant for the Application of Crop Production Systems Using Scaled Capillary Devices

Bioregenerative life support is key to sustaining human life on the surface of other celestial bodies for missions beyond Low Earth Orbit (LEO). One example of such life support includes crop production systems capable of producing both plants and fungi for astronaut consumption. There have been numerous efforts to design and deploy such systems; however, there have been persistent fundamental issues with the water delivery systems. This study aims to understand and model the fluid dynamics of crop production systems to inform engineers about the key parameters needed for the design of such systems. The primary objective is to validate and expand upon NASA’s previous study, the Plant Water Management (PWM) experiments, to understand the fluid phenomena present in substrate-based systems. The model will then be expanded to include parameters for changing the test material of potential growth media as well as the varying water demands of the crop throughout its different stages in its life cycle. Specifically, this study is focused on the viability of using lunar regolith for agricultural purposes. Terrestrial-based scaled capillary models will be utilized to mimic the fluid phenomena occurring due to the low gravity environment seen on the lunar surface. Ultimately, the study will model the fluid flow present in the lunar regolith simulant and inform researchers on how to incorporate the material into crop production systems on the lunar surface.

gravity↗
NASA NTRSDate not supplied

Comparisons Between NO PLIF Imaging and CFD Simulations of Mixing Flowfields for High-Speed Fuel Injectors

The current work compares experimentally and computationally obtained nitric oxide (NO) planar laser-induced fluorescence (PLIF) images of the mixing flowfields for three types of high-speed fuel injectors: a strut, a ramp, and a rectangular flushwall. These injection devices, which exhibited promising mixing performance at lower flight Mach numbers, are currently being studied as a part of the Enhanced Injection and Mixing Project (EIMP) at the NASA Langley Research Center. The EIMP aims to investigate scramjet fuel injection and mixing physics, and improve the understanding of underlying physical processes relevant to flight Mach numbers greater than eight. In the experiments conducted in the NASA Langley Arc-Heated Scramjet Test Facility (AHSTF), the injectors are placed downstream of a Mach 6 facility nozzle, which simulates the high Mach number air flow at the entrance of a scramjet combustor. Helium is used as an inert substitute for hydrogen fuel. Both schlieren and PLIF techniques are applied to obtain mixing flowfield flow visualizations. The experimental PLIF is obtained by using a UV laser sheet to interrogate a plane of the flow by exciting fluorescence from the NO molecules that are present in the AHSTF air. Consequently, the absence of signal in the resulting PLIF images is an indication of pure helium (fuel). The computational PLIF is obtained by applying a fluorescence model for NO to the results of the Reynolds-averaged simulations (RAS) of the mixing flowfield carried out using the VULCAN-CFD solver. This approach is required because the PLIF signal is a nonlinear function of not only NO concentration, but also pressure, temperature, and the flow velocity. This complexity allows additional flow features to be identified and compared with those obtained from the computational fluid dynamics (CFD) simulations, however, such comparisons are only semiquantitative. Three-dimensional image reconstruction, similar to that used in magnetic resonance imaging, is also used to obtain images in the streamwise and spanwise planes from select cross-stream PLIF plane data. Synthetic schlieren is also computed from the RAS data. Good agreement between the experimental and computational results provides increased confidence in the CFD simulations for investigations of injector performance.

PLIF↗
NASA NTRSDate not supplied

Comparisons Between NO PLIF Imaging and CFD Simulations of Mixing Flowfields for High-Speed Fuel Injectors

The current work compares experimentally and computationally obtained nitric oxide (NO) planar laser-induced fluorescence (PLIF) images of the mixing flowfields for three types of high-speed fuel injectors: a strut, a ramp, and a rectangular flushwall. These injection devices, which exhibited promising mixing performance at lower flight Mach numbers, are currently being studied as a part of the Enhanced Injection and Mixing Project (EIMP) at the NASA Langley Research Center. The EIMP aims to investigate scramjet fuel injection and mixing physics, and improve the understanding of underlying physical processes relevant to flight Mach numbers greater than eight. In the experiments conducted in the NASA Langley Arc-Heated Scramjet Test Facility (AHSTF), the injectors are placed downstream of a Mach 6 facility nozzle, which simulates the high Mach number air flow at the entrance of a scramjet combustor. Helium is used as an inert substitute for hydrogen fuel. Both schlieren and PLIF techniques are applied to obtain mixing flowfield flow visualizations. The experimental PLIF is obtained by using a UV laser sheet to interrogate a plane of the flow by exciting fluorescence from the NO molecules that are present in the AHSTF air. Consequently, the absence of signal in the resulting PLIF images is an indication of pure helium (fuel). The computational PLIF is obtained by applying a fluorescence model for NO to the results of the Reynolds-averaged simulations (RAS) of the mixing flowfield carried out using the VULCAN-CFD solver. This approach is required because the PLIF signal is a nonlinear function of not only NO concentration, but also pressure, temperature, and the flow velocity. This complexity allows additional flow features to be identified and compared with those obtained from the computational fluid dynamics (CFD) simulations, however, such comparisons are only semiquantitative. Three-dimensional image reconstruction, similar to that used in magnetic resonance imaging, is also used to obtain images in the streamwise and spanwise planes from select cross-stream PLIF plane data. Synthetic schlieren is also computed from the RAS data. Good agreement between the experimental and computational results provides increased confidence in the CFD simulations for investigations of injector performance.

PLIF↗