Preprints of the 18th IFAC World Congress Milano (Italy) August 28 - September 2, 2011 Control Strategies of Spaceplane Docking and Undocking with Other Winged Vehicle Alexander Nebylov, Vladimir Nebylov State University of Aerospace Instrumentation, Saint-Petersburg, Russia (Fax: +7 812 4947018, e-mail: [email protected]) Abstract: The concept of aerospace plane (ASP) horizontal launch and landing with the assist of heavy plane or ekranoplane is analyzed1. It is shown, that their docking at a final stage of aerospace plane alighting is favorable to expansion of functional capacity of this space transportation system. Ekranoplane with mass of 1500 ton or more is capable to carry ASP with initial mass of 500 ton and landing mass of 60-70 ton. Ekranoplane can provide ASP with the primary speed of Mach 0.5-0.65 in required direction that allows the lowering of the requirements to ASP wing area and its engines. A number of other advantages of the offered transport system are connected with the possible use of an ekranoplane at ASP launch and landing. Undocking and docking are the important stages of ASP flight which require the perfect automatic control. The requirements to corresponding systems of motion control of both winged crafts are presented, the structure of the integrated system of relative motion control is offered. Keywords: space vehicles, aerospace engineering, automatic controllers, interactive vehicle control. 1. INTRODUCTION moving winged platform, especially at their separation and possible approach. These problems could be divided into three main groups: The cost reduction of useful mass injection into near-Earth orbit, mechanical, aerodynamic (especially mutual interference) and expansion of functionality of space transport systems and ecology control. The paper is devoted first of all to control problems and safety requirements are among the major problems of space strategies of their solving. engineering. Reusability of space transport vehicles, simplification and the cheapening of the necessary infrastructure for providing 2. THE CONCEPT OF “PLANE+ASP” SYSTEM their launch and landing are very important directions of feature This concept is well-known and deeply analyzed. Several famous space technologies development. Aerospace plane (ASP) with projects exist with different heavy planes application, both subsonic horizontal aircraft-like controlled launch and landing seems to be and hypersonic. The heaviest in the world subsonic aircraft An-225 undoubtedly the most applicable kind of vehicle to meet the MRIA originally intended for ASP “BURAN” transportation is requirements of reusability, wide functionality and minimization of used in the Russian project MAKS. land area for ASP landing needs. Although the decisions to close the X-33 program by NASA, the HOTOL by British Aerospace and MAKS multipurpose aerospace system consists of the subsonic MAKS by RSA seems to favor only vertical launch, but modern carrier aircraft and an orbital ASP with an external fuel tank designs of Skylon, SpaceShipOne and SpaceShipTwo again give mounted on it. The second stage of the system has three chances to horizontal launch. modifications: MAKS-OS, MAKS-T and MAKS-M (Fig.1). Future orbital ASP may definitely perform take off, ascend, The MAKS-OS second stage consists of a reusable orbital vehicle descend, and landing like conventional aircraft, providing true and an expendable fuel tank. The basic manned variant of the single-stage-to-orbit capability. Horizontal take off and landing of MAKS-OS vehicle has a two-seat crew cabin. The MAKS-T ASP may be feasible presently, but a single-stage-to-orbit ASP with modification with the expendable unmanned second stage is horizontal take off and landing cannot be constructed at near- intended to put into orbit heavy (up to 18 tons) payloads. The term steps of space launchers technology development. So, MAKS-M second stage is the reusable unmanned orbital vehicle. some winged heavy vehicle has to be used as reusable booster and probably moving platform for landing. MAKS-M is regarded as possible further direction of MAKS concept when the first two modifications were fully developed. Two kinds of flying vehicles which could serve as a moving When MAKS-OS, -T and -M are created, they should be platform for ASP initial acceleration at launch and possible assist at incorporated into the joint operation on the basis of a common landing: heavy plane and ekranoplane (wing-in-ground effect craft), carrier aircraft and the ground infrastructure. The development of are known. In both cases many specific problems have to be solved MAKS-M is connected with solving the complex technological for implementation the proper co-operative motion of ASP and problems. 1 The work was supported by the Russian Foundation for Basic Research under the project 09-08-00529-а. Copyright by the 2109 International Federation of Automatic Control (IFAC) Preprints of the 18th IFAC World Congress Milano (Italy) August 28 - September 2, 2011 provided if all equipment for docking is an accessory of ekranoplane. The mass of gear for landing on runway may be approximately 3% of empty mass or 2530% of payload. So, the use of ekranoplane can permit to increase the payload of ASP by 30% and to decrease correspondingly the specific cost of launch. 3. The landing point can be chosen at any area of ocean that gives broad possibilities for ASP landing trajectory selection. Nine variants of ASP landing with ekranoplane assist were analyzed (Nebylov and Tomita, 1998a,b). All such variants are applicable for any ASP irrespectively to the variant of its launch horizontal or vertical, with ekranoplane use or without it. But the variant of ASP landing to the deck of moving ekranoplane by the use of docking and mechanical mating is the most interesting and produces the harshest demands to motion control systems accuracy and reliability. 4. PECULIARITIES OF EKRANOPLANE AS CONTROLLED CRAFT It is known that the longitudinal stability of ekranoplane in flight requires the special structural solutions in aerodynamic scheme for creation of the necessary control forces and moments to be applied. Fig. 1. MAKS system configuration A special multi-channel automatic control system for stabilization and damping of heavy ekranoplane movement is necessary to For decrease of technical risk of the full-scale MAKS the creation of consider for each definite aerodynamic configuration at the initial more simple and light demonstrational system was considered by stage of design. The problem of high accuracy and reliability of Russian NPO “Molniya” together with British Aerospace, ANTK measurement of parameters of flight close to the rough sea surface Antonov and TCAGI (Lozino-Lozinsky and Bratukhin, 1997). have to be solved, as well (Nebylov, 2010; Nebylov, Wilson, 2002). The opportunity of ASP catch by plane at the last stage of Specific conditions of ekranoplane and ASP mutual motion at descent was considered by TCAGI also. undocking and possible docking make it impossible to use in this transport system an ekranoplane of the most known plane 3. THE CONCEPT OF “EKRANOPLANE+ASP” SYSTEM configuration or ekranoplane "carrying wing + tail assembly" due to The concept of ekranoplane use for ASP horizontal take off and its high tail. Therefore the tail assembly of any form located landing was developed by Y.Ohkami, N.Tomita and A.Nebylov near to a longitudinal axis of ekranoplane is inadmissible, and (Tomita and Ohkami, 1995; Nebylov and Tomita, 1996, 1997; any consoles are possible only under their sufficient Nebylov, and Tomita, 1998a,b). Ekranoplane is a large marine wing displacement from this axis in a cross direction. All central part craft which is capable to fly with application of wing-in-ground of ekranoplane deck should be practically flat for normal (WIG) effect at a small altitude above sea surface. The flight altitude accommodation and movement of ASP. So, the configurations has to be approximately one tenth of the wing chord. of ekranoplane-catamaran of «combined wing» and «tandem» are preferable. The ekranoplane of «combined wing» It is shown (Tomita, Nebylov, Sokolov, Ohkami(1999) that configuration with ASP displaced on its deck is shown in Fig.2. ekranoplane with its own mass of 1500 ton is able to launch ASP with starting mass more than 500 ton and landing mass of 60-70 ton. It can solve the problems of ASP transportation from the base to the launch point which is far from human settlements and advantageous for forming the required orbit parameters, ASP loading with fuel directly before launch and providing ASP with the primary speed of Mach 0.5-0.65 in required direction that allows to lower the requirements to the ASP wing area and its engines. The payload of the launch system “ASP+Ekranoplane” could be 3 times greater against the system MAKS-OS. Three main reasons may be pointed for application ekranoplane as an additional component in space transportation system: 1. The specially prepared runway is not required. 2. ASP can be supplied with simplified and lighted landing gear or has not gear at all when landing on ekranoplane moving with the Fig. 2. Ekranoplane of “Combined Wing” configuration with velocity equal to ASP one. Extremely large saving of mass will be ASP 2110 Preprints of the 18th IFAC World Congress Milano (Italy) August 28 - September 2, 2011 The control system of ekranoplane should ensure its given trajectory and improve dynamic properties. Nonlinear character of interrelations between separate channels of altitude, pitch, velocity, roll and yaw of this system, intensive wind and wave disturbances, the necessity of a special mode of turning away from surface obstacles and many other features give specificity to a task of system development, though in the task statement the categories ordinary for the theory of automatic control are used. Great inertia of heavy ekranoplane-catamaran in course maneuvering forces to put it on the given line of a linear motion in advance and actively operate only by absolute velocity at approach and docking with ASP.