Procedure of providing Yamal unmanned spacecraft flight with synergetic propellant margin of electric thrusters

For accomplishing the mission program by Yamal unmanned spacecraft (USC), i.e. GEO communication satellites, two tasks shall be solved: holding in place of location and controlling the orbital attitude. For the purpose of solving the first task spacecraft maneuvers are periodically performed using electric thrusters (ET). The other task is solved by using electric engine-flywheels, which are desaturated from accumulated angular momentum using ET and gas engines operating on the same propellant, i.e. xenon. Therefore, the propellant margin defines operational efficiency of the mission program associated with duration of USC execution of its functional tasks. The paper presents a procedure used to derive additional synergetic propellant margin based on the knowledge of the onboard processes. Experience has proven that through involvement of a comprehensive information model of USC as a complicated dynamic system while performing the same mission program dynamic operations with propellant consumption an additional margin can be derived.