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High Reynolds Number Testing of the NATO AVT-298 SWiFT Configuration at the National Transonic Facility

A high Reynolds number wind tunnel test of the NATO AVT-298 Swept Wing Flow Test (SWiFT) configuration was conducted in the National Transonic Facility at the NASA Langley Research Center during the summer of 2023. The SWiFT research model geometry has relevance to both blended/hybrid wing body (BWB/HWB) and unmanned combat aerial vehicle (UCAV) configurations, and the test campaign was the culmination of an international collaboration under the NATO AVT-298 research task group. The main objectives of the test were to investigate Reynolds number scaling effects on low-speed stability & control characteristics and to examine the onset and progression of flow separation on the wings particularly near the wing crank. Force & moment and surface pressure data were acquired at Mach numbers from 0.2 to 0.8, Reynolds numbers from 2.5 to 34 million, angles of attack from -3 to 20 degrees, and sideslip angles from -10 to 10 degrees. Boundary layer transition detection techniques utilizing static pressure taps, unsteady pressure transducers, and sublimating chemicals were used on the model in a free/natural transition state or a forced transition state using trip dots. Pressure sensitive paint was used to obtain a global surface pressure profile on the model and an advanced laser velocimetry technique was used to obtain velocity measurements in the wake downstream of the wing crank. The results from the test showed clear Reynolds number scaling effects on the maximum lift coefficient and pitching moment coefficient at Mach 0.2, while also capturing significant hysteresis effects. The data acquired from the test will ultimately help improve computational aerodynamic analysis and design tools for application to future BWB-type vehicle configurations.

BWB/HWB↗

NASA NTRS1998

Wide Panel Testing Technique for Evaluating Repair Weld Strengths

This paper describes a new tensile testing technique for evaluating the overall effect of a repair weld on the strength of a welded joint. Previously, repair weld strengths have been evaluated using one-inch width tensile specimens, but this technique does not capture all of the effects that result from a repair. The new technique involves testing of "wide panel" tensile specimens which contain the full length of a repair weld within a longer initial weld, allowing the specimen to capture the combined effects of residual stresses, local strength degradation, and load redistribution around a repair. The development of strains in the repair area of standard aluminum alloy specimens and new high-performance aluminum-lithium alloy specimens was observed and evaluated using photoelastic material. The results of this evaluation show an increased sensitivity to repair welding residual stresses in the aluminum-lithium alloy specimens.

Rogers, Patrick R.↗

NASA NTRS2012

Large-Eddy / Reynolds-Averaged Navier-Stokes Simulations of a Dual-Mode Scramjet Combustor

Numerical simulations of reacting and non-reacting flows within a scramjet combustor configuration experimentally mapped at the University of Virginia s Scramjet Combustion Facility (operating with Configuration A ) are described in this paper. Reynolds-Averaged Navier-Stokes (RANS) and hybrid Large Eddy Simulation / Reynolds-Averaged Navier-Stokes (LES / RANS) methods are utilized, with the intent of comparing essentially blind predictions with results from non-intrusive flow-field measurement methods including coherent anti-Stokes Raman spectroscopy (CARS), hydroxyl radical planar laser-induced fluorescence (OH-PLIF), stereoscopic particle image velocimetry (SPIV), wavelength modulation spectroscopy (WMS), and focusing Schlieren. NC State's REACTMB solver was used both for RANS and LES / RANS, along with a 9-species, 19- reaction H2-air kinetics mechanism by Jachimowski. Inviscid fluxes were evaluated using Edwards LDFSS flux-splitting scheme, and the Menter BSL turbulence model was utilized in both full-domain RANS simulations and as the unsteady RANS portion of the LES / RANS closure. Simulations were executed and compared with experiment at two equivalence ratios, PHI = 0.17 and PHI = 0.34. Results show that the PHI = 0.17 flame is hotter near the injector while the PHI = 0.34 flame is displaced further downstream in the combustor, though it is still anchored to the injector. Reactant mixing was predicted to be much better at the lower equivalence ratio. The LES / RANS model appears to predict lower overall heat release compared to RANS (at least for PHI = 0.17), and its capability to capture the direct effects of larger turbulent eddies leads to much better predictions of reactant mixing and combustion in the flame stabilization region downstream of the fuel injector. Numerical results from the LES/RANS model also show very good agreement with OH-PLIF and SPIV measurements. An un-damped long-wave oscillation of the pre-combustion shock train, which caused convergence problems in some RANS simulations, was also captured in LES / RANS simulations, which were able to accommodate its effects accurately.

Fulton, Jesse A.↗

NASA NTRS1993

Orbital simulations of satellite escape/capture and the origin of satellites such as Triton

We investigate satellite escape/capture in the context of the restricted, circular three body problem as applied to the Sun, Neptune, and Triton. We have computed a large number of coplanar prograde and retrograde orbital simulations over a range of initial distances and velocities. The satellite starts at superior conjunction within approximately 2 Hill radii of Neptune and has a velocity orthogonal to the Sun-planet line. Orbits with these initial conditions can be reflected with respect to time, so an escape is simply the reverse of a capture. We numerically integrate the equations of motion to compute the satellite's position until it escapes, collides with Neptune, or after 100 planetary years fails to escape, when computations cease. The initial distance x and velocity v in the restricted problem uniquely define the Jacobi constant C, a conserved energy-like quantity. Plots of the simulation outcomes in the prograde and retrograde C, x phase spaces reveal distinct zones in which temporary satellites approach the planet closely enough that permanent capture can be effected by gas drag with a protoplanetary nebula or by collision with a pre-existing satellite. Single and double close-flybys constitute the most common possible capture orbits. Long term multiple flyby orbits occur near the stability limits between bound and unbound orbits, and are more common among retrograde captures.

Benner, Lance A. M.↗

NASA NTRS2017

Thermal Modeling of Mars Ground for Surface Missions

Thermal analysis packages are capable of including ground temperature effects for orbital and surface thermal analyses. In particular, Thermal Desktop® offers the option of specifying ground temperatures as a function of time for planetary surface modeling. While suitable for many cases, this approach is not sufficient if an object has local interactions with the ground that could significantly affect the ground temperature. Ground modeling is necessary for the Mars 2020 rover thermal design and analysis since shadowing and heat dissipation from the rover’s Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) can result in significant temperature deviations of the local ground. The Mars 2020 thermal team is explicitly modeling the Martian ground so that these local temperature effects can be captured. The upper portion of the ground is modeled, and material and optical properties of the ground are varied in order to match data collected from orbiting science instruments. Atmospheric surface temperature, sky temperatures, and solar loads from a Mars General Circulation Model (GCM) are used as boundary conditions, resulting in a ground surface temperature profile consistent with the GCM predictions. The rover model is then placed on this modeled ground so that the effects of shadowing and MMRTG dissipation on the ground temperature can be captured.

Farias, Edgardo↗

NASA NTRS1991

Experimental validation of docking and capture using space robotics testbeds

Docking concepts include capture, berthing, and docking. The definitions of these terms, consistent with AIAA, are as follows: (1) capture (grasping)--the use of a manipulator to make initial contact and attachment between transfer vehicle and a platform; (2) berthing--positioning of a transfer vehicle or payload into platform restraints using a manipulator; and (3) docking--propulsive mechanical connection between vehicle and platform. The combination of the capture and berthing operations is effectively the same as docking; i.e., capture (grasping) + berthing = docking. These concepts are discussed in terms of Martin Marietta's ability to develop validation methods using robotics testbeds.

Spofford, John↗

NASA NTRS1977

New contributions to the problem of capture

Libration-point capture is analyzed in the framework of the restricted three-body problem in order to obtain general results capable of predicting the major features of an arbitrary postcapture orbit, with specific reference to capture as the presumed mode of origin of Jupiter's outer satellites. Some examples of libration-point capture are computed, the time a body remains captured is estimated, and a long-term numerical integration of orbits is carried out which shows that the equation used to estimate capture lifetimes is quite conservative. An extended capture criterion is proposed and used to demonstrate that direct postcapture orbits lie outside retrograde ones. Mass change involving one or both primaries is evaluated as a means of producing permanent capture, it is found that mass-change effects can produce 'pull-down capture', and consideration is given to the orbital evolution of Jupiter's outer satellites. The effect of drag in the solar nebula or in a nebula around proto-Jupiter on the capture process is briefly investigated. It is concluded that a capture origin for the outer satellites is improbable within the last 4.6 billion years but that either mass change or nebula drag could have been effective in producing capture.

Heppenheimer, T. A.↗

NASA NTRS1995

Micro-abrasion package capture cell experiment on the trailing edge of LDEF: Impactor chemistry and whipple bumper shield efficiencies

Four of the eight available double layer microparticle capture cells, flown as the experiment A0023 on the trailing (West) face of LDEF, have been extensively studied. An investigation of the chemistry of impactors has been made using SEM/EDX techniques and the effectiveness of the capture cells as bumper shields has also been examined. Studies of these capture cells gave positive EDX results, with 53 percent of impact sites indicating the presence of some chemical residues, the predominant residue identified as being silicon in varying quantities.

Fitzgerald, Howard J.↗

NASA NTRS2010

CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response.

Sances, Dillon J.↗

NASA NTRS1973

Dynamically plausible hypotheses of lunar origin

The implausibility of the capture hypothesis of lunar origin is pointed out. The reason for this implausibility is the extreme weakness of the only known energy sink for pure capture, tidal friction. A mechanism proposed by Alfven and Arrhenius (1972) is the locking of the moon in synchronization with a longitudinal variation in the earth's gravitational field. It is shown that collision with preexisting satellite matter is the most effective means of capturing a moon.

Kaula, W. M.↗

NASA NTRS1976

Georgia Institute of Technology research on the Gas Core Actinide Transmutation Reactor (GCATR)

The program reviewed is a study of the feasibility, design, and optimization of the GCATR. The program is designed to take advantage of initial results and to continue work carried out on the Gas Core Breeder Reactor. The program complements NASA's program of developing UF6 fueled cavity reactors for power, nuclear pumped lasers, and other advanced technology applications. The program comprises: (1) General Studies--Parametric survey calculations performed to examine the effects of reactor spectrum and flux level on the actinide transmutation for GCATR conditions. The sensitivity of the results to neutron cross sections are to be assessed. Specifically, the parametric calculations of the actinide transmutation are to include the mass, isotope composition, fission and capture rates, reactivity effects, and neutron activity of recycled actinides. (2) GCATR Design Studies--This task is a major thrust of the proposed research program. Several subtasks are considered: optimization criteria studies of the blanket and fuel reprocessing, the actinide insertion and recirculation system, and the system integration. A brief review of the background of the GCATR and ongoing research is presented.

Clement, J. D.↗

NASA NTRS2012

Plume-Free Stream Interaction Heating Effects During Orion Crew Module Reentry

During reentry of the Orion Crew Module (CM), vehicle attitude control will be performed by firing reaction control system (RCS) thrusters. Simulation of RCS plumes and their interaction with the oncoming flow has been difficult for the analysis community due to the large scarf angles of the RCS thrusters and the unsteady nature of the Orion capsule backshell environments. The model for the aerothermal database has thus relied on wind tunnel test data to capture the heating effects of thruster plume interactions with the freestream. These data are only valid for the continuum flow regime of the reentry trajectory. A Direct Simulation Monte Carlo (DSMC) analysis was performed to study the vehicle heating effects that result from the RCS thruster plume interaction with the oncoming freestream flow at high altitudes during Orion CM reentry. The study was performed with the DSMC Analysis Code (DAC). The inflow boundary conditions for the jets were obtained from Data Parallel Line Relaxation (DPLR) computational fluid dynamics (CFD) solutions. Simulations were performed for the roll, yaw, pitch-up and pitch-down jets at altitudes of 105 km, 125 km and 160 km as well as vacuum conditions. For comparison purposes (see Figure 1), the freestream conditions were based on previous DAC simulations performed without active RCS to populate the aerodynamic database for the Orion CM. Other inputs to the analysis included a constant Orbital reentry velocity of 7.5 km/s and angle of attack of 160 degrees. The results of the study showed that the interaction effects decrease quickly with increasing altitude. Also, jets with highly scarfed nozzles cause more severe heating compared to the nozzles with lower scarf angles. The difficulty of performing these simulations was based on the maximum number density and the ratio of number densities between the freestream and the plume for each simulation. The lowest altitude solutions required a substantial amount of computational resources (up to 1800 processors) to simulate approximately 2 billion molecules for the refined (adapted) solutions.

Marichalar, J.↗

NASA NTRS1994

Laboratory simulation of intact capture of cometary and asteroidal dust particles in ISAS

In order to develop a collector for intact capturing of cometary dust particles in the SOCCER mission and regolith dust particles released from asteroid surfaces by the impact of projectiles launched from a flying-by spacecraft, various kinds of materials as the collector candidates have been exposed to hypervelocity projectiles in our laboratory. Data based on the penetration characteristics of various materials (penetration depth, hole profile, effectiveness for intact capturing) are greatly increased. The materials tested for these simulation experiments include various kinds of low-density media and multisheet stacks; these are foamed plastics (polystyrene 0.01 g/cc), silica aerogels (0.04 g/cc), air (0.001 g/cc), liquid, and multisheet stack consisting of thin Al sheets (thickness 0.002 to 0.1 mm) or polyethylene sheets. Projectiles used are spheres or cylinders of nylon, polycarbonate, basalt, copper, iron, and volatile organics (e.g.,paradichlorobenzene) of size ranging from 30 micrometers to 1 cm launched by a two-stage light gas gun and a rail gun in ISAS at velocity up to about 7 km/s. Some results obtained by using nylon projectiles of velocity less than about 5 km/s are presented; the penetration depth vs. bulk density of the collector material for several kinds of materials and the velocity at which the projectiles begin to fragment vs. material density for foamed polystyrene.

Fujiwara, A.↗

NASA NTRS2019

Evaluation of Ionic Liquids for Closed Air Revitalization

This document is the final report resulting from the work conducted by undergraduate students at the University of South Alabama during the 2018/2019 academic year and was prepared by the undergraduate students. As NASA pushes the boundaries further into space, the current technologies within the various life support systems must be improved upon. One such improvement is needed to the current air revitalization systems, specifically sorbents that can capture CO2 more effectively from enclosed habitats. Ionic liquids (ILs) have been considered as absorbents for flue gas, but little research has been done to test the ability of ILs at ambient pressures and relatively low concentration of CO2. The experiment outlined below utilizes the task-specific ionic liquid, tetramethylammonium taurinate (TMN), in a commercial off the shelf absorption system to capture CO2. The CO2 stream is combined with nitrogen to produce an inlet gas concentration relevant to close air revitalization applications. At an inlet gas flow with a CO2 partial pressure of 3.8 torr the system was capable of removing just under 97% of the inlet CO2. The concentration of CO2 in the outlet stream, partial pressure 0.16 torr, was less than that of atmospheric air. The duty required to separate the absorbed gas from the ionic liquid as well to cool the ionic liquid to be reintroduced to the column were acquired utilizing laboratory cooling/heating baths. These results show that TMN may be an efficient candidate for consideration in closed air revitalization.

Duck, Gerald↗

NASA NTRS1988

Transonic Navier-Stokes computations of strake-generated vortex interactions for a fighter-like configuration

Transonic Euler/Navier-Stokes computations are accomplished for wing-body flow fields using a computer program called Transonic Navier-Stokes (TNS). The wing-body grids are generated using a program called ZONER, which subdivides a coarse grid about a fighter-like aircraft configuration into smaller zones, which are tailored to local grid requirements. These zones can be either finely clustered for capture of viscous effects, or coarsely clustered for inviscid portions of the flow field. Different equation sets may be solved in the different zone types. This modular approach also affords the opportunity to modify a local region of the grid without recomputing the global grid. This capability speeds up the design optimization process when quick modifications to the geometry definition are desired. The solution algorithm embodied in TNS is implicit, and is capable of capturing pressure gradients associated with shocks. The algebraic turbulence model employed has proven adequate for viscous interactions with moderate separation. Results confirm that the TNS program can successfully be used to simulate transonic viscous flows about complicated 3-D geometries.

Reznick, Steve↗

NASA NTRS1985

A nonoscillatory shock capturing scheme using flux limited dissipation

A method for modifying the third order dissipative terms by the introduction of flux limiters is proposed. The first order dissipative terms can then be eliminated entirely, and in the case of a scalar conservation law the scheme is converted into a total variation diminishing scheme provided that an appropriate value is chosen for the dissipative coefficient. Particular attention is given to: (1) the treatment of the scalar conservation law; (2) the treatment of the Euler equations for inviscid compressible flow; (3) the boundary conditions; and (4) multistage time stepping and multigrid schemes. Numerical results for transonic flows suggest that a central difference scheme augmented by flux limited dissipative terms can lead to an effective nonoscillatory shock capturing method.

Jameson, A.↗

NASA NTRS1997

Binary Oscillatory Crossflow Electrophoresis

Electrophoresis has long been recognized as an effective analytic technique for the separation of proteins and other charged species, however attempts at scaling up to accommodate commercial volumes have met with limited success. In this report we describe a novel electrophoretic separation technique - Binary Oscillatory Crossflow Electrophoresis (BOCE). Numerical simulations indicate that the technique has the potential for preparative scale throughputs with high resolution, while simultaneously avoiding many problems common to conventional electrophoresis. The technique utilizes the interaction of an oscillatory electric field and a transverse oscillatory shear flow to create an active binary filter for the separation of charged protein species. An oscillatory electric field is applied across the narrow gap of a rectangular channel inducing a periodic motion of charged protein species. The amplitude of this motion depends on the dimensionless electrophoretic mobility, alpha = E(sub o)mu/(omega)d, where E(sub o) is the amplitude of the electric field oscillations, mu is the dimensional mobility, omega is the angular frequency of oscillation and d is the channel gap width. An oscillatory shear flow is induced along the length of the channel resulting in the separation of species with different mobilities. We present a model that predicts the oscillatory behavior of charged species and allows estimation of both the magnitude of the induced convective velocity and the effective diffusivity as a function of a in infinitely long channels. Numerical results indicate that in addition to the mobility dependence, the steady state behavior of solute species may be strongly affected by oscillating fluid into and out of the active electric field region at the ends of the cell. The effect is most pronounced using time dependent shear flows of the same frequency (cos((omega)t)) flow mode) as the electric field oscillations. Under such conditions, experiments indicate that solute is drawn into the cell from reservoirs at both ends of the cell leading to a large mass build up. As a consequence, any initially induced mass flux will vanish after short times. This effect was not captured by the infinite channel model and hence numerical and experimental results deviated significantly. The revised model including finite cell lengths and reservoir volumes allowed quantitative predictions of the time history of the concentration profile throughout the system. This latter model accurately describes the fluxes observed for both oscillatory flow modes in experiments using single protein species. Based on the results obtained from research funded under NASA grant NAG-8-1080.S, we conclude that binary separations are not possible using purely oscillatory flow modes because of end effects associated with the cos((omega)t) mode. Our research shows, however, that a combination of cos(2(omega)t) and steady flow should lead to efficient separation free of end effects. This possibility is currently under investigation.

Molloy, Richard F.↗

NASA NTRS1990

Numerical prediction of turbulent flow over airfoil sections with a new nonequilibrium turbulence model

A new nonequilibrium turbulence closure model has been developed for computing wall bounded two-dimensional turbulent flows. This two-layer eddy viscosity model was motivated by the success of the Johnson-King model in separated flow regions. The influence of history effects are described by an ordinary differential equation developed from the turbulent kinetic energy equation. The performance of the present model has been evaluated by solving the flow around three airfoils using the Reynolds time-averaged Navier-Stokes equations. Excellent results were obtained for both attached and separated turbulent flows about the NACA 0012 airfoil, the RAE 2822 airfoil, and the Integrated Technology A 153W airfoil. Based on the comparison of the numerical solutions with the available experimental data, it is concluded that the new nonequilibrium turbulence model accurately captures the history effects of convection and diffusion on turbulence.

Ahmed, S.↗