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An Exploration of Spotted White Dwarfs from K2
The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018The Kepler K2 mission has discovered a significant
population of white dwarf stars that exhibit
photometric variability due to surface inhomogeneities
likely related to magnetism. These “spotted”
white dwarfs present not only in temperature
regimes where we expect convection to dominate
white dwarf photospheres, but also where
radiation should dominate. We present an exploration
of spotted white dwarfs as a function of
various physical characteristics, including temperature,
magnetic field strength, and rotational period,
in order to better understand the origins of
these photometric variations.Astronom
Unsteady aerodynamic analysis of space shuttle vehicles. Part 2: Steady and unsteady aerodynamics of sharp-edged delta wings
An analysis of the steady and unsteady aerodynamics of sharp-edged slender wings has been performed. The results show that slender wing theory can be modified to give the potential flow static and dynamic characteristics in incompressible flow. A semiempirical approximation is developed for the vortex-induced loads, and it is shown that the analytic approximation for sharp-edged slender wings gives good prediction of experimentally determined steady and unsteady aerodynamics at M = 0 and M = 1. The predictions are good not only for delta wings but also for so-called arrow and diamond wings. The results indicate that the effects of delta planform lifting surfaces can be included in a simple manner when determining elastic launch vehicle dynamic characteristics. For Part 1 see (N73-32763)
Unsteady aerodynamic analysis of space shuttle vehicles. Part 4: Effect of control deflections on orbiter unsteady aerodynamics
The unsteady aerodynamics of the 040A orbiter have been explored experimentally. The results substantiate earlier predictions of the unsteady flow boundaries for a 60 deg swept delta wing at zero yaw and with no controls deflected. The test revealed a previously unknown region of discontinuous yaw characteristics at transonic speeds. Oilflow results indicate that this is the result of a coupling between wing and fuselage flows via the separated region forward of the deflected elevon. In fact, the large leeward elevon deflections are shown to produce a multitude of nonlinear stability effects which sometimes involve hysteresis. Predictions of the unsteady flow boundaries are made for the current orbiter. They should carry a good degree of confidence due to the present substantiation of previous predictions for the 040A. It is proposed that the present experiments be extended to the current configuration to define control-induced effects. Every effort should be made to account for Reynolds number, roughness, and possible hot-wall effects on any future experiments
Unsteady airfoil stall
Dynamic and static stall data in relation to airfoil stall at subsonic speed
Unsteady aerodynamic analysis of space shuttle vehicles. Part 1: Summary report
An analysis of the unsteady aerodynamics of space shuttle vehicles was performed. The results show that slender wing theory can be modified to give the potential flow static and dynamic characteristics over a large Mach number range from M = 0 to M 1. A semi-empirical analytic approximation is derived for the loads induced by the leading edge vortex; and it is shown that the developed analytic technique gives good prediction of experimentally determined steady and unsteady delta wing aerodynamics, including the effects of leading edge roundness. At supersonic speeds, attached leading edge flow is established and shock-induced flow separation effects become of concern. Analysis of experimental results for a variety of boost configurations led to a definition of the main features of the flow interference effects between orbiter (delta wing) and booster. The effects of control deflection on the unsteady aerodynamics of the delta-wing orbiter were also evaluated
Unsteady aerodynamic flow field analysis of the space shuttle configuration. Part 2: Launch vehicle aeroelastic analysis
An exploratory analysis has been made of the aeroelastic stability of the Space Shuttle Launch Configuration, with the objective of defining critical flow phenomena with adverse aeroelastic effects and developing simple analytic means of describing the time-dependent flow-interference effects so that they can be incorporated into a computer program to predict the aeroelastic stability of all free-free modes of the shuttle launch configuration. Three critical flow phenomana have been identified: (1) discontinuous jump of orbiter wing shock, (2) inlet flow between orbiter and booster, and (3) H.O. tank base flow. All involve highly nonlinear and often discontinuous aerodynamics which cause limit cycle oscillations of certain critical modes. Given the appropriate static data, the dynamic effects of the wing shock jump and the HO tank bulbous base effect can be analyzed using the developed quasi-steady techniques. However, further analytic and experimental efforts are required before the dynamic effects of the inlet flow phenomenon can be predicted for the shuttle launch configuration
Unsteady aerodynamic flow field analysis of the space shuttle configuration. Part 1: Orbiter aerodynamics
An analysis of the steady and unsteady aerodynamics of the space shuttle orbiter has been performed. It is shown that slender wing theory can be modified to account for the effect of Mach number and leading edge roundness on both attached and separated flow loads. The orbiter unsteady aerodynamics can be computed by defining two equivalent slender wings, one for attached flow loads and another for the vortex-induced loads. It is found that the orbiter is in the transonic speed region subject to vortex-shock-boundary layer interactions that cause highly nonlinear or discontinuous load changes which can endanger the structural integrity of the orbiter wing and possibly cause snap roll problems. It is presently impossible to simulate these interactions in a wind tunnel test even in the static case. Thus, a well planned combined analytic and experimental approach is needed to solve the problem
Review of delta wing space shuttle vehicle dynamics
The unsteady aerodynamics of the proposed delta planform, high cross range, shuttle orbiters, are investigated. It is found that these vehicles are subject to five unsteady-flow phenomena that could compromise the flight dynamics. The phenomena are as follows: (1) leeside shock-induced separation, (2) sudden leading-edge stall, (3) vortex burst, (4)bow shock-flap shock interaction, and (5) forebody vorticity. Trajectory shaping is seen as the most powerful means of avoiding deterimental effects of the stall phenomena; however, stall must be fixed or controlled when traversing the stall region. Other phenomana may be controlled by carefully programmed control deflections and some configuration modifications. Ways to alter the occurrence of the various flow conditions are explored
Unsteady airfoil stall and stall flutter
Unsteady airfoil stall characteristics using static data input for predicting stall flutter boundaries of space shuttle win
Gust penetration loads and elastic vehicle response for Saturn 5 launch vehicles
Analysis of gust penetration loads and associated elastic vehicle response of Saturn 5 launch vehicles AS-505 through AS-508 penetrating sinusoidal gust
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