In particular concerning the drafting of the SFA Boeing X-51 on the initiative of the U.S. Air Force in cooperation with NASA and the Australian Defence Force realized multipurpose programm flight tests HiFire, which initially called AFRL FRESH. It is planned to study experimentally the main hypersonic technology, first scramjet in real criteria. Programmke on each flight will be carried out in advance of the most detailed numerical calculations and experiments in the wind tunnel. Results flying experience should be compared with these data to determine the correlations and the amendments to the results of ground tests in order to bring them to reality.
Allocated for the implementation of programs from $ 56 million, and the role it attracted 5 SIC NASA, many institutions in Australia and the United States, the center CUBRC, United Technology Research Center, a division of «Phantom Wax» and other U.S. funds 5 flight, Australia — four clarity regarding the tenth flight yet. In the founding documents programm HiFire evaluated as a unique opportunity to conduct basic research in the real criteria when applicable costs for tests. The program provides for the subsequent study of problems: transient conditions in the boundary layer and the viscous-inviscid interaction; interaction of shock waves on the edges of a boundary layer and aerodynamic heating; real gas effects and chemical non-equilibrium flows; evaporative cooling; three-dimensional separated flows (jet exhaust); control and resistance to thermal flow using magneto-ways; spatial around the body, the appearance and interaction of shock waves among themselves and with the boundary layer.
Flight tests programmke HiFire to Woomera in Australia were to be made along with the unit tests X-51 to 2012 inclusive flight 1-3 times a year. In each flight planned research 4 types spanning among other such regimes, which can not be reproduced in terrestrial criteria. Implementation of Woomera is associated with certain limitations on terms. Weather conditions for starting the machine HiFire optimal only twice a year (March — April and October — November). This large-scale project is realized on the basis of experience in programm HyShot and HyCAUSE. Need to ship using a two-stage accelerator «Terriers — Orion» is displayed on the height of the order of 290 km, and then enters the atmosphere at a steep dive mode, reaching the estimated number of M = 4-8. During the descent the main measure produced. First means to obtain the data necessary for applets of success X-51. At the same time create a reliable database for the development of promising reusable carriers, reconnaissance and strike SFA also tactical hypersonic long-range guns.
Flight tests are divided into two groups: the first — three tests without the power plant; Second — seven with the simulation of SU. Each flight is planned in four or five options to choose more firmly implemented, burning and perspective on the results. Each flight is unique in the sense of tasks, methods and techniques of research, mass and shape of the payload — experimental module. The only common to all test equipment had to be a computer for information processing, as expected, on the basis of computer PC104 «Texas Instruments». But after the flight programs and HyShot HyCAUSE revealed a need for improved microprocessor because some disk imaging principle could not be restored. Data collected during flight will be transmitted to the ground station on three channels at a rate of 10 Mbyte / s. Every flight in all qualities modeled on earth. Currently, numerical and experimental research work in ADT and on the boards much more busy professionals, particularly if in flight training. Due to the use of standard accelerator «Terriers — Orion» launch price is slightly lower than in the flight tests on other applets.
Planned in-flight experimental studies classified according to their importance. So, the first flight was supposed to experience one major significance, three — and one secondary — tertiary. The latter means that the equipment is tested for off-design operation, but, at least, it is revealed whether it is applicable in general. For example, under the terms of the first flight is unlikely appearance of plasma, the respective sensor was mounted to clarify a number of features. The program HiFire characterized as highly flexible, allowing the incorporation of new technologies, although the preparation of each flight takes more than 5 months. First flight was dedicated to one hundred percent of basic research: the transition of laminar boundary layer on a cone in turbulent; interaction of shock waves with the boundary layer and the crossing; detailed investigation of the thermal flows and state structures; optical measurements in the flow simulator for in vozduhopoglotitele.
The parent company in the preparation and conduct of the second flight is ATK; in the experimental module embedded mini scramjet channel developed laboratory AFRL and NASA. Manage third flight belongs Australian side; planned research workers traits scramjet. In the fourth start-up meant the free flight of the experimental module for the purpose of testing navigation and control systems. In this flight, the company is particularly interested «Boeing», since the module is waveriders. In the fifth flight investigated spatial hypersonic flow module in the form of an elliptic cone. In other missions will be explored scramjet work, perhaps combined with volnoletnogo body type. This body will not copy machine body X-51, as puzzles programs SED-WR HiFire and all the same variety. There is evidence that the results of flight tests will be classified.
The immense computational and experimental research in the wind tunnel and on the boards were aimed at identifying good experimental module configuration, type and number of sensors and their placement on the module, a detailed study of the processes that are meant to explore in flight, so that in the coming associate and correlate data and flight purchased from ADT also critically evaluate various numerical and empirical methods of calculation. Experimental module weighing 105 kg is made in the form of a rotationally symmetric body: head cone — cylinder — a truncated cone (skirt) with a total length of 1,816 m (according to other sources, 2.5 m). Diameter base section skirt is 0.356 m, which corresponds to the cross section is the accelerator «Orion». Length SFA together with the accelerator is about 13 m to ship remains docked with the second stage of the accelerator until the end of the flight. During reentry active pitch control and tilt is not provided, but the SFA will aim at the required angle of pitch by blowing cool gas.
In connection with the choice of the assembly tests were conducted in a wind tunnel models with varying geometric characteristics within wide limits, including full-scale tests of the module in the final version. Angle of a nose cone, created for the study of free transition from laminar to turbulent boundary layer is equal to 7 °, and the radius of the bluntness of the sock — 2.5 mm. Dull was chosen in view of the judgments that may very sharp toe melted, and the increase of the radius of blunting promotes stabilization of the boundary layer, ie, the transition can be displaced by a clot beyond the boundaries of the cone.
Results of tests to determine the pipe position transition to a cone with an angle of 7 ° and a suitable number of Re can not be specifically attributed to programmke HiFire, as in terrestrial experience strong effects of acoustic disturbances and adiabatic heating walls ADT. Yet, for a thorough assessment, the flight number Re transition on the cone will be approximately 6 x 10 (the distance from the tip of the cone), and the highest temperature of about 2000 sock-head cone K. Because experimental module has an integral sock length about 0.1 m from alloy TZM (titanium, zirconium, molybdenum) with a melting point of 2800 K. The rest of the cone has a duralumin trim width of 20 mm. According to calculations, this part of the largest heating achieves approximately 400 K on the rise and about 475 K on the descent. Time for measurement does not exceed 3-4 seconds. That at any development flow to obtain data on the transition in the boundary layer of hypervelocity on one side of the cone baffles installed. Tilt angle forming a truncated cone included in the assembly to generate shock, elected equal 33 ° (first was 37 °). The first draft of the module was composed of only a sharp cone and truncated. But numerical simulations showed that the tear area can spread to the nose cone right up to his middle, which can not afford to differentiate transition in the boundary layer. Because cones inserted between the cylinder.
Special issue — surface finish. It is shown that on a cone over a length of 0.1 m from the nose very allowable roughness does not exceed 3 x 10 m, and the rms least 10 m as the distance from the tip boundary layer becomes stable, because completely satisfactory standard 8 x 10 m Advances in miniaturization measuring techniques have allowed located in a small module 326 highly sensitive sensors with a special performance, fixing significantly nonlinear and time-dependent properties, including the feeble pressure and temperature fluctuations. Namely, for the measurement of thermal flows used coaxial thermocouple diameter of about 1.5 mm. Full-scale tests of the equipped sensors module conducted at the research center in CUBRC ADT LENS-1 with working part diameter of 2.44 m simulated hypersonic modes (M = 6-8) at different altitudes in the trajectory calculation points SFA. Together with measurements made flow speed photography, shadow visualized way. The results are used to evaluate a number of methods of calculation and transition criteria; clarified the limits of applicability and the ability to improve. Noteworthy that the best agreement with experimental fruits not found any of the numerical methods and semi-empirical (Van Driest 2).
Line motion flight apparatus HiFire first flight was chosen similar apparatus HyShot 2, but was later recalculated. At the time of re-entry speed SFA corresponds to the number M = 8. Given that the height of the atmosphere about 80 km, it becomes obvious that only the first and last about 45 seconds of flight tested in its borders — a reserve of time to perform the measurements. Because in subsequent tests instead conventional ballistic line of motion will be more gentle slope, to extend the time available experience. The solution to this puzzles, very difficult when you start with the standard accelerators («shot — forget») is assigned to NASA. Calculations depending very attainable height and range of the mass of the payload when running under different angles to the horizon show that the average increase in weight of the cargo at 18 kg lowers the peak about 15 km, the largest number of M — 0.25. The position and orientation of the SFA in flight (angle of attack, pitch angle, etc.) must be recorded with the highest accuracy for a particular interpretation of measurement results.
First successful flight on programmke HiFire held March 22, 2010 weighing 105 kg module entered the atmosphere at a rate corresponding to the number of M = 7.2. In reality, it was the second flight. First in May 2009 ended in failure: the desired goods lost at an altitude of 25 km, apparently deviated from the calculated line of motion due to inaccurate entry into the atmosphere. Procedure for the following flights revised. In 2011 were planned third, fourth, second, eighth and fifth flights, in 2012 — the seventh and ninth. With all of this third and seventh flights — on the Pacific U.S. military ground, seven flights — at Woomera. Parallel to the work on adaptation accelerators «Terriers — Orion» to the first flight tests analyzed the possibility of using a stronger second stage launches in 2011-2012. U.S. Department of Defense is considering aaplet HiFire as a significant contribution to the strategy of combining air and of cosmic spaces and transformation of the Air Force in aerospace.
At first glance programm HiFire not associated with the flight of cosmic. But the results are very large and painstaking research in the boundary layer have tremendous value creation for all spacecraft, designed for re-entry, and not only the Earth, and other planets. Reliable experimental data on heat transfer to the SFA and thermal protection systems, their first resource will move from the empirical choice of material and thickness of the thermal barrier coatings to scientifically substantiated. HiFire project should be brought to the sixth level of readiness (TRL-6) — the end of the test layout in real criteria. Based on the results acquired tactical missile with a scramjet could be ready by 2018 Moreover, According to experts of «Boeing», with appropriate funding combat hypersonic long-range missile (1000-1800 km), Curb scramjet, can be designed for 5 10 years, the plane — for 10-20 years, reusable economical carrier for spacecraft — for 15-30 years.
In case of successful execution described applets not excluded second step to performing tests on assignments researchers Germany, Italy and the land of the rising sun. Namely, the Italian news agency CIRA expects to hold flight tests unmanned spacecraft with marching number M = 8, held for 15 seconds. Japanese researchers plan to test in the real criteria promising scramjet at speeds respectively M = 8.