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In a recent flight experiment to study hypersonic crossflow transition, boundary layer characteristics were documented. A smooth steel glove was mounted on the first stage delta wing of Orbital Sciences Corporation's Pegasus (R) launch vehicle and was flown at speeds of up to Mach 8 and altitudes of up to 250,000 ft. The wing-glove experiment was f...
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... for the glove and the ceramic-tile fairing, the vehicle is coated with an ablative for thermal protection. Figure 2 illustrates how the Pegasus ® is launched from the L-1011 and how the payload is put into orbit. Only the first-stage flight was relevant to the experiment since the glove was part of Stage 1. ...
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The near-wake of a separated flow behind a generic space launcher model with different afterbody extensions is studied experimentally in the hypersonic flow regime (Mach number 6.0 and unit Reynolds number 16 × 10 6 m −1) with the main objective being to show unsteady flow phenomena. This objective is based on the desire to control the base flow of...
Citations
... The Pegasus wing-glove experiment successfully flew in October 1998 (after many years in storage waiting for a launch opportunity). 11 The stated purpose for this flight test was to acquire CF data at approximately Mach 6 and 80-100 kft. This experiment was actually a secondary payload on a standard launch for a paying customer of the Orbital Sciences Pegasus launch vehicle, with a highly instrumented wing glove attached to the right side of the first-stage delta wing, as shown in Fig. 2. The glove was instrumented, as shown in Fig. 3, with surface pressure taps and backside thermocouples (type-K foil stick-on sensors). ...
Much has been learned about the physics underlying the transition process at supersonic and hypersonic speeds through years of analysis, experiment and computation. Generally, the application of this knowledge has been restricted to simple shapes like plates, cones and spherical bodies. However, flight reentry vehicles are in reality never simple. They typically are highly complex geometries flown at angle of attack so three-dimensional effects are very important, as are roughness effects due to surface features and/or ablation. This paper will review our present understanding of the physics of the transition process and look back at some of the recent flight test programs for their successes and failures. The goal of this paper is to develop rationale for new hypersonic boundary layer transition flight experiments. Motivations will be derived from both an inward look at what we believe constitutes a good flight test program as well as an outward review of the goals and objectives of some recent US based unclassified proposals and programs. As part of our recommendations, this paper will address the need for careful experimental work as per the guidelines enunciated years ago by the U.S. Transition Study Group. Following these guidelines is essential to obtaining reliable, usable data for allowing refinement of transition estimation techniques.
... 9 Efforts to improve transition prediction models include the application of linear stability theory to hypersonic transition and examination of data from the Pegasus flight experiment. 10,11 As a follow-on to the development and characterization of passive forced transition mechanisms for the X-43A flight experiment, alternative mechanisms that can provide "transition on demand" were investigated. The approach of using mass injection to force boundary layer transition was demonstrated experimentally at Mach 6 and Mach 10 conditions. ...
An overview of some of the activities in hypersonic airbreathing aerodynamics and propulsion airframe integration is presented for the Space Vehicle Technology Institute. The Institute is a multi-university joint NASA-DoD program that was created as a center for research and education in future launch vehicle technologies. Perhaps more than any other type of flight vehicle, next generation space launchers will have to be analyzed as completely integrated aerodynamic-propulsion systems. Optimal aerodynamics will be vital to the development of efficient, engine-integrated launch vehicle forms, especially using airbreathing propulsion. To this end, inverse design approaches, design tradeoffs, and an understanding of relevant basic flow physics are all part of the Space Vehicle Technology Institute program. The relevance of these efforts to NASA activities is also described.
در این مقاله به اهمیت برآورد صحیح رفتار آیرودینامیکی بالمثلثی در مرحله طراحی مفهومی یک موشک ماهوارهبر هواپایه پرداخته شده و
چندین روش تخمین و محاسبه ضرایب آیرودینامیکی بررسی و دقت این روشها سنجیده شده است. نرمافزارهای علمی و تجاری و نیز نرمافزار
فلوئنت بهعنوان شیوههای مختلف در دسترس انتخاب و از هندسه مشابه بالمثلثی نصبشده بر روی ماهوارهبر هواپایه پگاسوس بهعنوان الگو
استفاده شده است. ویژگی متمایز این بال، عدم استفاده از تونل باد در روند طراحی آن و پرواز در گستره وسیعی از جریانها میباشد. با توجه به
اینکه پارامترهای متعددی از جمله ضرایب نیرو و ممان آیرودینامیکی، مشتقات پایداری و کنترل، ضرایب بارگذاری بر روی سازه بال و ضریب
انتقال حرارت بال موردنیاز است، لذا توانمندی روشهای مختلف در تخمین و محاسبه ضرایب آیرودینامیکی بهعنوان مهمترین پارامترهای موثر
بر رفتار سیستم، ارزیابی شده و در هر رژیم جریان، نرمافزار یا تکنیک حل مناسب معرفی شده است. با توجه به قدرت و ظرفیت سامانه پردازش
موازی در دسترس، تکنیکهای متفاوت CFDباهم مقایسه و روش شبیهسازی گردابههای جدا شده ( )DESبهعنوان یک روش بسیار دقیق
بهکار گرفته شده است. دقت روشهای حل معادلات میانگین رینولدز ( )RANSو معادلات اویلر براساس مقایسه با نتایج حاصل از DES
سنجیده شده که محدودههای اعتبار و صحت این شیوههای سادهتر نیز پیشنهاد شده است. نتایج کلی حاصل، نشاندهنده مزیت نسبی روشهای
CFDبر نرمافزارهای صنعتی و کدهای نیمهتجربی است. نرمافزارهای صنعتی و کد نیمه تجربی عمدتاً در محدوده خطی یا زوایای حمله
کوچک، پاسخ های مطلوب ارایه میدهند
In this paper, the importance of accurate estimation of the aerodynamic performance of air-launch-to-orbit delta wing in the conceptual design phase has been mentioned. Some available and conventional methods of estimating the aerodynamic coefficients composed of CFD methods and industrial and commercial software have been selected and for comparison, a wing similar to delta wing mounted on Pegasus Air-launch-to-orbit missile as a template is being selected. The reason for this selection, mainly is the lack of wind tunnel in design process and flying in a wide range of flow regimes. As many parameters may be utilized in design process such as the aerodynamic force and moment coefficients, stability derivatives, heat transfer coefficient and the structural loading parameters are being required. In this study, the accuracy of the results of different methods in estimating the force and moment coefficients, as the most significant quantities for performance analysis, at any flow regime has been checked and the suitable method has been introduced in terms of the flight condition. With respect to available parallel processing system, different CFD methods are compared together. Then validity of solution of Reynolds-averaged equations (RANS) and Euler method have been evaluated based on the comparison by DES solutions. Therefore, the valid intervals of the subsequent methods have been presented. Results are indicating the advantage of computational methods to industrial and semi-empirical software. Semi-empirical code and industrial software are shown satisfactory for computation in the linear range i.e. the small angle of attacks.
