Preliminary study of advanced hypersonic research aircraft
Flight constraints and aerodynamic characteristics of hypersonic research aircraft
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Flight constraints and aerodynamic characteristics of hypersonic research aircraft
Wind tunnel investigation of aerodynamic characteristics of wing-body and lifting body configurations for hypersonic cruise aircraft at hypersonic speeds
Heat transfer problem solutions with application to hypersonic cruise aircraft
The general problem of calculating the flow fields associated with hypersonic airbreathing aircrafts is presented. Unique aspects of hypersonic airplane aerodynamics are introduced and their demands on CFD are outlined. Example calculations associated with inlet/forebody integration and hypersonic nozzle design are presented to illustrate the nature of the problems considered.
The purpose of this study is to validate two existing codes used by the Systems Analysis Branch at NASA ARC, and to modify the codes so they can be used to generate and analyze waverider aircraft at on-design and off-design conditions. To generate waverider configurations and perform the on-design analysis, the appropriately named Waverider code is used. The Waverider code is based on the Taylor-Maccoll equations. Validation is accomplished via a comparison with previously published results. The Waverider code is modified to incorporate a fairing to close off the base area of the waverider configuration. This creates a more realistic waverider. The Hypersonic Aircraft Vehicle Optimization Code (HAVOC) is used to perform the off-design analysis of waverider configurations generated by the Waverider code. Various approximate analysis methods are used by HAVOC to predict the aerodynamic characteristics, which are validated via a comparison with experimental results from a hypersonic test model.
A theoretical study of the use of heat pipe structures for cooling the leading edges of hypersonic cruise aircraft was carried out over a Mach number range of 6 to 12. Preliminary design studies showed that a heat pipe cooling structure with a 33-in. chordwise length could maintain the maximum temperature of a 65 deg sweepback wing with a 0.5-in. leading edge radius below 1600 F during cruise at Mach 8. A few relatively minor changes in the steady-state design of the structure were found necessary to insure satisfactory cooling during the climb to cruise speed and altitude. It was concluded that heat pipe cooling is an attractive, feasible technique for limiting leading edge temperatures of hypersonic cruise aircraft.
A hypersonic cruise transport conceptual design is described. The integration of the subsonic, supersonic, and hypersonic propulsion systems with the aerodynamic design of the airframe is emphasized. An evaluation of various configurations of aircraft and propulsion integration concepts, and selection and refinement of a final design are given. This configuration was used as a baseline to compare two propulsion concepts - one using a fixed geometry dual combustion mode scramjet and the other a variable geometry ramjet engine. Both concepts used turbojet engines for takeoff, landing and acceleration to supersonic speed.
The paper reports on results of heat-transfer tests conducted on a 1/29-scale model of the X-24C-12I hypersonic research aircraft configuration in a Mach 6 tunnel at a Reynolds number of thirteen million using the phase-change heat transfer technique. Sequences of phase-change heat transfer pattern photographs are presented showing windward side and leeward side heating processes. Theoretical predictions of dimensionless heat transfer coefficients along a data line on lower fuselage and on fuselage side bracket the experimental values. A turbulent heating theory gives good agreement with data when shifted to a new virtual origin.
An ablative material composed of silica-filled elastomeric silicone was tested to evaluate its thermal and structural performance as an external insulator, or heat shield, for a hypersonic research aircraft. The material was also tested to determine whether it would form a durable char layer when initially heated and thereafter function primarily as an insulator with little further pyrolysis or char removal. Aerothermal tests were representative of nominal Mach 6 cruise conditions of the aircraft, and additional tests were representative of Mach 8 cruise and interference heating conditions. Radiant heating tests were used to simulate the complete nominal Mach 6 surface-temperature history. The silica char that formed during aerothermal tests was not durable. The char experienced a general and preferential surface recession, with the primary mechanism for char removal being erosion. Tests revealed that radiant heating is not a valid technique for simulating aerodynamic heating of the material.
A general discussion is given on the use of advanced computational fluid dynamics (CFD) in analyzing the hypersonic flow field around an airbreathing aircraft. Unique features of the hypersonic flow physics are presented and an assessment is given of the current algorithms in terms of their capability to model hypersonic flows. Several examples of advanced CFD applications are then presented.
Effects of elevon-induced three-dimensional shock-wave turbulent boundary-layer interactions on hypersonic aircraft surfaces are analyzed. Detailed surface pressure and heating rate distributions obtained on wing-elevon-fuselage models representative of aft portions of hypersonic aircraft are compared with analytical and experimental results from other sources. Examples are presented that may be used to evaluate the adequacy of current theoretical methods for estimating the effects of three-dimensional shock-wave turbulent boundary-layer interactions on hypersonic aircraft surfaces.
A development status evaluation is presented for CFD methods applicable to fuselage-integrated scramjet powerplant incorporating hypersonic vehicles; these methods are critically important due to the unavailability of experimental facilities for such elevated Mach number/high-enthalphy conditions. Advancements are required in algorithm robustness and speed, geometric flexibility, and the inclusion of more complete flow physics. The most serious deficiencies lie in turbulence modeling, the lack of complete transition-prediction methods, and combustion modeling.
An experimental investigation of the low-speed longitudinal, lateral, and directional stability characteristics of a lifting-body hypersonic research airplane concept was conducted in a low-speed tunnel with a 12-foot (3.66-meter) octagonal test section at the Langley Research Center. The model was tested with two sets of horizontal and vertical tip controls having different planform areas, a center vertical tail and two sets of canard controls having trapezoidal and delta planforms, and retracted and deployed engine modules and canopy. This investigation was conducted at a dynamic pressure of 239.4 Pa (5 psf) (Mach number of 0.06) and a Reynolds number of 2 million based on the fuselage length. The tests were conducted through an angle-of-attack range of 0 deg to 30 deg and through horizontal-tail deflections of 10 deg to minus 30 deg. The complete configuration exhibited excessive positive static longitudinal stability about the design center-of-gravity location. However, the configuration was unstable laterally at low angles of attack and unstable directionally throughout the angle-of-attack range. Longitudinal control was insufficient to trim at usable angles of attack. Experiments showed that a rearward shift of the center of gravity and the use of a center-located vertical tail would result in a stable and controllable vehicle.
Airbreathing hypersonic aircraft employing liquid hydrogen fuel have the potential of satisfying a number of mission requirements in the 1980-2000 time period. However, major advances in the technological state of the art are necessary before such aircraft can be considered either feasible or practical. The objective was to assess the research and development requirements for hypersonic aircraft and based on these requirements, to provide the NASA with characteristics of a number of desirable hypersonic research facilities. The study is organized in three phases. Phase I is a preliminary analysis of a broad group of concepts. The purpose of Phase I was to compare the characteristics of these facilities considering research capability, versatility, adaptability, system confidence and costs and based on these comparisons select those facilities that appear most attractive for parametric study and further refinement in Phase II. This part of Volume II presents the results of the design and cost synthesis of the flight research facilities.
Airbreathing hypersonic aircraft employing liquid hydrogen fuel have the potential of satisfying a number of mission requirements in the 1980-2000 time period. However, major advances in the technological state of the art are necessary before such aircraft can be considered either feasible or practical. The objective was to assess the research and development requirements for hypersonic aircraft and based on these requirements, to provide the NASA with characteristics of a number of desirable hypersonic research facilities. The study is organized in three phases. Phase I was a preliminary analysis of a broad group of concepts which were reduced to seven flight research facilities and eleven ground research facilities for Phase II study. The purpose of Phase II was to perform parametric studies to refine the facility designs and obtain sensitivity information in the neighborhood of "near optimum" designs, and to select those facilities that appear most attractive in the sense of research potential vs cost for further refinement in Phase III. This part of Volume III presents the results of the synthesis of the flight research facilities.
The longitudinal and lateral directional aerodynamic characteristics for two Mach 5 cruise aircraft concepts were determined for test Mach numbers of 2.96, 3.96, and 4.63. Estimates from hypersonic impact theory and first order supersonic linearized theory were compared with data to indicate the usefulness of these methods. The method which applied tangent cone empirical theory to the body and tangent wedge theory to the wings and to the horizontal and vertical tails provided the best estimates. The tangent cone empirical theory applied to all components showed poor agreement with data, and the linear theory estimates were accurate only for lift coefficient and drag coefficient at low angles of attack.
The feasibility of using a single metallic heat sink thermal protection system (TPS) over a projected flight test program for a hypersonic research vehicle was studied using transient thermal analyses and mission performance calculations. Four materials, aluminum, titanium, Lockalloy, and beryllium, as well as several combinations, were evaluated. Influence of trajectory parameters were considered on TPS and mission performance for both the clean vehicle configuration as well as with an experimental scramjet mounted. From this study it was concluded that a metallic heat sink TPS can be effectively employed for a hypersonic research airplane flight envelope which includes dash missions in excess of Mach 8 and 60 seconds of cruise at Mach numbers greater than 6. For best heat sink TPS match over the flight envelope, Lockalloy and titanium appear to be the most promising candidates
Conceptual vehicle configuration and propulsion approach for a Mach 6 transport aircraft capable of carring 200 passengers 9260 km was investigated. Wind tunnel test data for various hypersonic transport configurations were examined. Canidates for baseline reference vehicles were selected. An explanation of technical methods which were used and configuration details which were significant in the final vehicle concept are given.