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OPTIMAL MULTIREVOLUTIONAL TRANSFERS BETWEEN NON-COPLANAR ELLIPTICAL ORBITS. 2nd International Symposium "LOw ThrUSt trajectories" (LOTUS-2). Tolouse, France, June 18-20, 2002 It is considered optimization of low-thrust trajectories between non-coplanar elliptical orbits. The optimal control problem is reduced to the two-point boundary value problem (TPBVP) by means of maximum principle. The numerical homotopic technique and modified newton technique are used to solve TPBVP. Differential equations of optimal motion are numerically averaged when TPBVP is solved. It was developed the robust and efficient software and a large number of optimal trajectories were calculated. New qualitative results were obtained. In particularity, there were found bifurcation of optimal solutions and existence of the critical initial inclination. The partial classification of optimal control structure was carried out. Presentation. Seminar of Space Research Institute (IKI) of Russian Academy of Sciences, June 2000. Homotopic (continuathion) method description. Low-thrust trajectories optimization in case of variable specific impulse: interplanetary and lunar trajectories. Low-thrust trajectory optimization in case of constant specific impulse: transfers between non-coplanar elliptical orbits. Low-Thrust trajectories optimization and evolution. Doctoral thesis, Moscow 1996 There are developed new numerical methods for low-thrust trajectory optimization based on homotopic (continuation) technique. These methods allow - to solve power-limited (variable specific impulse) problem routinely; - to solve constant ejection velocity problem using power-limited solution as initial approximation; - to find parametric families of optimal trajectories depending on various boundary and design parameters; - to optimize flyby and rendezvous missions; - to solve minimum-propellant and minimum-time problems; - to solve optimal control problem when jet power is function of spacecraft position. It is analyzed evolution of low-thrust trajectories due to third body perturbation. Particular and approximate solutions of averaged equations were obtained. It was carried out particular classification of these solutions. New developed methods allow to estimate main design parameters of spacecraft and they were used for interplanetary missions feasibility study, including space missions to planets, natural satellites, and asteroids. IN RUSSIAN ELECTRIC PROPULSION MISSION TO GEO USING SOYUZ/FREGAT LAUNCH VEHICLE, IAF-01-V.3.02 There are analyzed solar electric propulsion missions to geostationary orbit (GEO) using Soyuz launch vehicle and Fregat upper stage. The considered combined flight profile includes insertion into the low Earth orbit (LEO) using Soyuz/Fregat launch vehicle, transfer into an intermediate orbit providing by Fregat upper stage, and electric propulsion transfer into GEO. The purpose of study is search for commercially available space platform, which could be adopted to realize electric propulsion transfer into GEO using Soyuz launch vehicle. The transfer duration was considered as criteria of the mission commercial viability. Eighteen commercially available space platforms were analyzed. There were considered upgraded (electric propulsion) versions of these platforms: the conventional apogee propulsion system was considered to be replaced by electric propulsion unit. The SPT-100/140 and XIPS-13/25 thrusters were considered for the electric propulsion unit. The carried out analysis shows that the transfer duration is less then 3 months for 4 space platforms (STAR 1, STAR 2, HS 376HP, Spacebus 1000) and within 3-4 months for 6 space platforms (FS 1300HP, A2100, A2100AX, Eurostar 2000, Spacebus 2000, Spacebus 3000). LOW-THRUST TRAJECTORY OPTIMIZATION IN RUSSIA. ESA/ESTEC Workshop on Trajectory Design and Optimization. Noordwijk, October 24-25, 2002 Review SPACECRAFT INSERTION INTO HIGH WORKING ORBITS USING LIGHT-CLASS LAUNCHER AND ELECTRIC PROPULSION It is considered minimum-time transfer between elliptical and circular orbits. The optimization technique for multirevolutional low-thrust transfer is presented. It is presented the universal table of non-dimensional characteristic velocities, which could be used for fast estimation of optimal transfers between arbitrary elliptical and circular orbits. This technique is applied to the optimization of spacecraft insertion into target orbits using light-class launch vehicles and electric propulsion. Typical flight profile includes insertion into a parking orbit using launch vehicle, transfer into an elliptical intermediate orbit using high-thrust, and transfer into target orbit using electric propulsion. Presented results could be used for feasibility study of low-cost space missions. Associated Optimization of the Low-Thrust Trajectory and Parameters of the Nuclear Power Plant. IEPC-95-214 It is considered optimization of the main design parameters of the electric propulsion missions. It is supposed that onboard power source is a “Topaz”-type nuclear power plant (NPP). NPP parameters can be varied within some limits, which are defined by possibility of the modification of the developing basic NPP model NPP-25. There are considered NPP modifications that allow to enforce its output power for a different duration. This investigation concerns to coordination of the spacecraft design parameters and basic parameters of the NPP (electrical power, lifetime, mass, and size). APPLICATION OF THE POWER-LIMITED PROBLEM TO THE ELECTRIC PROPULSION MISSION DESIGN. IEPC-95-220 Two mathematical propulsion models have most frequently been used1. In the constant ejection velocity (CEV) model, either the thrust or thrust acceleration is bounded. In the power-limited (LP) model, power of the jet (the product of the thrust magnitude and the specific impulse) is bounded. This paper is concerned to comparison of the LP and CEV models. It is demonstrated that LP solution is a quite precise approximation of the CEV one. The possibility to use LP solution to solve CEV problem is considered. The corresponding continuation method is presented. ONE NUMERICAL METHOD TO CALCULATE OPTIMAL POWER-LIMITED TRAJECTORIES. IEPC-95-221 There are conventionally used different kinds of the Newton’s methods and the shooting ones to solve boundary value problems of the celestial mechanics and space flight mechanics. These classes of methods have a number of deficiencies. Small dimension of the convergence region is the most essential deficiency generally. This causes great difficulties to choose initial approximation for solving boundary value problems. It is considered the possibility to use method of differentiating with respect to parameter for constructing algorithm of solving of two point boundary value problem (TPBVP) to optimize power-limited transfers. The numerical algorithm of this method is described and examples of solutions are presented. COMBINED FLIGHT PROFILE TO INSERT TELECOMMUNICATION SATELLITE INTO GEOSTATIONARY ORBIT USING ROCKOT LIGHT-WEIGHT CLASS LAUNCH VEHICLE Khrunichev State Research and Production Space Center is carrying out Research & Development of unified space bus Yacht which should be inserted into the orbit using Rockot light-weight class launch vehicle. The Yacht space platform is equipped with electric propulsion module based on stationary plasma thrusters SPT-100. One of Yacht applications is geostationary telecommunication satellite. It is proposed to use combined flight profile to insert the geostationary satellite into GEO. Within this profile, the Breeze upper stage is used to form an elliptical transfer orbit. The insertion into GEO from the transfer orbit is provided by the spacecraft’s electric propulsion module. The electric propulsion module is used during the GEO operations as well, including station-keeping and reaction wheels unloading. The carried out study shows that spacecraft having mass 450-500 kg with 100-150 kg of telecommunication equipment can be delivered into GEO using Rockot launch vehicle from Plesetsk or Baykonur launch sites. | |||
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