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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The simulation of time varying ascent loads on arrays of Shuttle tiles in a large transonic tunnel

A large variety of tests were made to determine the strength, fatigue and thermal characteristics of the thermal-protection system of the Shuttle orbiter. The present paper describes first-launch-critical tests which were conducted in the Langley 8-Foot Transonic Pressure Tunnel (8'TPT) which simulated the time histories of Shuttle ascent loads on tile arrays bonded to structures which accurately duplicated those of the Shuttle. The time varying free-stream conditions were provided by controlling the deflection angle history of diffuser spoiler flaps in an automated way. Time histories of the critical-load parameters imposed on the tile arrays in the tunnel are compared in the paper to those expected in flight. In addition, the effect of repeated load pulses on the smoothness of the surface and condition of the tiles is discussed briefly.

Bobbitt, P. J.↗
NASA NTRS1983

Supersonic loads due to shuttle-orbiter/external-tank attachment structures

A large variety of tests were conducted during development of the Space Shuttle to determine the strength, fatigue, and thermal characteristics of the thermal-protection system of the orbiter. The research and analysis carried out to accurately define and simulate the flow characteristics immediately ahead of the external tank attachment structures are described. The highest known acoustic pressure loads occur in these regions and tests to insure the ability of the titles to withstand these acoustic loads, plus those due to pressure gradient, were thought necessary. First flight-critical wind tunnel tests were therefore conducted in the Langley 8-Foot Transonic Pressure Tunnel (8-Ft. TPT), which simulated the time histories of Shuttle ascent loads on tile arrays bonded to structures which accurately duplicated those of the Shuttle. The time-varying free stream conditions were provided by controlling the deflection angle history of diffuser spoiler flaps in an automated way. Time histories of the critical load parameters imposed on the tile arrays in the tunnel are compared with those expected in flight.

Edwards, C. L. W.↗
NASA NTRS1983

IPACS Guidance Navigation and Control System Considerations and Test Activities

The MSFC facility proposed for the Space Station Attitude Control Simulator which consists of a large three degree of freedom table driven by computer controlled hydraulic actuators designed to give high bandwidth and extremely fine control through large angles is outlined. The facility includes star and solar simulators providing collimated light with the spectral content and intensity typical of Earth orbit.

Buchanan, H. J.↗
NASA NTRS1986

Hypersonic aerodynamic characteristics of a candidate entry research vehicle

Static longitudinal and lateral-directional aerodynamic characteristics of a candidate lifting entry research vehicle were measured at Mach numbers of 6 and 10 in air and at Mach 20 in helium. The effects of nose bluntness, body flap deflection, and elevon deflection were examined over a range of angle of attack. The vehicle demonstrated static longitudinal and lateral-directional stability at angles of attack from the maximum lift-to-drag ratio (L/D)max to high angles of attack. Sufficient control effectiveness existed to provide longitudinal trim from (L/D)max to high angles of attack. Aerodynamic coefficients predicted using the Hypersonic Arbitrary Body Program were compared to measurement. Good agreement was obtained for lift-to-drag values.

Brauckmann, G. J.↗
NASA NTRS1987

Aspects of Voyager photogrammetry

In January 1986, Voyager 2 took a series of pictures of Uranus and its satellites with the Imaging Science System (ISS) on board the spacecraft. Based on six stereo images from the ISS narrow-angle camera, a topographic map was compiled of the Southern Hemisphere of Miranda, one of Uranus' moons. Assuming a spherical figure, a 20-km surface relief is shown on the map. With three additional images from the ISS wide-angle camera, a control network of Miranda's Southern Hemisphere was established by analytical photogrammetry, producing 88 ground points for the control of multiple-model compilation on the AS-11AM analytical stereoplotter. Digital terrain data from the topographic map of Miranda have also been produced. By combining these data and the image data from the Voyager 2 mission, perspective views or even a movie of the mapped area can be made. The application of these newly developed techniques to Voyager 1 imagery, which includes a few overlapping pictures of Io and Ganymede, permits the compilation of contour maps or topographic profiles of these bodies on the analytical stereoplotters.

Wu, Sherman S. C.↗
NASA NTRS1987

Quasi-steady flight to quasi-steady flight transition in a windshear - Trajectory optimization and guidance

The near-optimum guidance of an aircraft from quasi-steady flight to quasi-steady flight in a windshear is studied. The take-off problem is considered with reference to flight in a vertical plane; allowance is made for the presence of a downdraft as well as horizontal shear. It is assumed that the power setting is held at the maximum value and that the aircraft is controlled through the angle of attack. While the shear guidance and the initial aftershear guidance use constant gain coefficients, the final aftershear guidance employs a variable gain coefficient. The results show that the guidance scheme for quasi-steady flight recovery yields a transition from quasi-steady flight to quasi-steady flight which is close to that of the optimal trajectory; it guarantees the restoration of the initial quasi-steady state and has good stability properties.

Miele, A.↗
NASA NTRS1988

Adaptive guidance for an aero-assisted boost vehicle

An adaptive guidance system incorporating dynamic pressure constraint is studied for a single stage to low earth orbit (LEO) aero-assist booster with thrust gimbal angle as the control variable. To derive an adaptive guidance law, cubic spline functions are used to represent the ascent profile. The booster flight to LEO is divided into initial and terminal phases. In the initial phase, the ascent profile is continuously updated to maximize the performance of the boost vehicle enroute. A linear feedback control is used in the terminal phase to guide the aero-assisted booster onto the desired LEO. The computer simulation of the vehicle dynamics considers a rotating spherical earth, inverse square (Newtonian) gravity field and an exponential model for the earth's atmospheric density. This adaptive guidance algorithm is capable of handling large deviations in both atmospheric conditions and modeling uncertainties, while ensuring maximum booster performance.

Pamadi, Bandu N.↗
NASA NTRS1988

Optimization and guidance of penetration landing trajectories in a windshear

The optimization and guidance of penetration landing trajectories in a windshear are considered. It is assumed that the aircraft is controlled by the angle of attack and the power setting. For the optimal trajectory, the performance index being minimized measures the deviation of the flight trajectory from the nominal trajectory. In turn, the nominal trajectory includes two parts: the approach part (nominal glide slope constant) and the flare part (nominal glide slope varying linearly with the horizontal distance). Numerical results show that the optimal trajectory deviates somewhat from the nominal trajectory in the shear region. A guidance scheme is developed to approximate the optimal trajectory. The angle of attack is determined by the windshear intensity, the absolute path inclination, and the glide slope angle, while the power setting is determined by the windshear intensity and the velocity. Numerical results indicate that the guidance trajectory is close to the optimal trajectory.

Miele, A.↗
NASA NTRS1989

Average-passage simulation of counter-rotating propfan propulsion systems as applied to cruise missiles

Counter-rotating propfan (CRP) propulsion technologies are currently being evaluated as cruise missile propulsion systems. The aerodynamic integration concerns associated with this application are being addressed through the computational modeling of the missile body-propfan flowfield interactions. The work described in this paper consists of a detailed analysis of the aerodynamic interactions between the control surfaces and the propfan blades through the solution of the average-passage equation system. Two baseline configurations were studied, the control fins mounted forward of the counter-rotating propeller and the control fins mounted aft of the counter-rotating propeller. In both cases, control fin-propfan separation distance and control fin deflection angle were varied.

Mulac, Richard A.↗
NASA NTRS1989

Abort landing guidance trajectories in the presence of windshear

The flight trajectory of abort landing in the presence of windshear is examined with reference to flight in a vertical plane. It is assumed that the only control is the angle of attack. Inequality constraints are imposed on both the angle of attack and its time derivative. Numerical results are obtained for several combinations of windshear intensities and initial altitudes. Guidance trajectories are considered, approximating the optimal trajectories and using local information on the state of the aircraft, the initial altitude, and the total wind velocity difference. Results are presented for optimal trajectories, guidance trajectories, simplified guidance trajectories, constant pitch trajectories, and maximum angle of attack trajectories.

Miele, A.↗
NASA NTRS1989

Average-passage simulation of counter-rotating propfan propulsion systems as applied to cruise missiles

Counter-rotating propfan (CRP) propulsion technologies are currently being evaluated as cruise missile propulsion systems. The aerodynamic integration concerns associated with this application are being addressed through the computational modeling of the missile body-propfan flowfield interactions. The work described in this paper consists of a detailed analysis of the aerodynamic interactions between the control surfaces and the propfan blades through the solution of the average-passage equation system. Two baseline configurations were studied, the control fins mounted forward of the counter-rotating propeller and the control fins mounted aft of the counter-rotating propeller. In both cases, control fin-propfan separation distance and control fin deflection angle were varied.

Mulac, Richard A.↗
NASA NTRS1990

Control of flow separation and mixing by aerodynamic excitation

The recent research in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of a fundamental nature, concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research includes influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

Rice, Edward J.↗
NASA NTRS1991

An analytically linearized helicopter model with improved modeling accuracy

An analytically linearized model for helicopter flight response including rotor blade dynamics and dynamic inflow, that was recently developed, was studied with the objective of increasing the understanding, the ease of use, and the accuracy of the model. The mathematical model is described along with a description of the UH-60A Black Hawk helicopter and flight test used to validate the model. To aid in utilization of the model for sensitivity analysis, a new, faster, and more efficient implementation of the model was developed. It is shown that several errors in the mathematical modeling of the system caused a reduction in accuracy. These errors in rotor force resolution, trim force and moment calculation, and rotor inertia terms were corrected along with improvements to the programming style and documentation. Use of a trim input file to drive the model is examined. Trim file errors in blade twist, control input phase angle, coning and lag angles, main and tail rotor pitch, and uniform induced velocity, were corrected. Finally, through direct comparison of the original and corrected model responses to flight test data, the effect of the corrections on overall model output is shown.

Jensen, Patrick T.↗
NASA NTRS1990

Control of flow separation and mixing by aerodynamic excitation

The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

Rice, Edward J.↗
NASA NTRS1992

Flow Over A Simplified-Rocket-Shaped Body

Report describes observations of supersonic flow of air over cylindrical body capped by hemisphere at its head and flared to cone at its tail end. Study prompted by need for greater aircraft control at high angles of attack.

Schiff, Lewis B.↗
NASA NTRS1992

An airborne system for collecting polarization imagery

This paper describes a recently completed electrooptical camera flying onboard the NASA ER-2 high altitude aircraft. The device includes a six-position filter wheel which can be fitted with a combination of polarizing and/or spectral filters. An alternate configuration will include a polarizing filter which can be rotated to any angle under computer control. The camera mount in the nose of the ER-2 can tilt forward or aft up to 40 degrees, both for bidirectional reflectance studies and for image motion compensation (the aircraft moves 34 meters between frame acquisitions). The ground resolution is nominally 5 meters from and altitude of 20 km. Spectral responsivity is that of the silicon imaging array (Kodak KAF-1400). Initial data sets were acquired in support of the International Satellite Cloud Climatology Program Regional Experiment of November, 1991, and will be used to study cirrus cloud properties.

Hildum, Edward A.↗
NASA NTRS1958

Effectiveness of Boundary-layer Control, Obtained by Blowing over a Plain Rear Flap in Combination with a Forward Slotted Flap, in Deflecting a Slipstream Downward for Vertical Take-off

The wing employed in this investigation had a 67-percent-chord slotted flap in combination with a 33-percent-chord plain rear flap equipped with a full-span blowing nozzle. The tests were conducted in a static-thrust facility at the Langley Aeronautical Laboratory. The investigation indicated that the plain rear flap alone with a low momentum coefficient for boundary-layer control provided larger turning angles than the combined slotted and plain flaps without boundary-layer control.

HIGH-LIFT DEVICES - COMPLETE WINGS↗