The influence of the combined propulsion system parameters on the integral dose of radiation when putting a spacecraft into a geostationary orbit

At present to transfer a spacecraft from a low earth to geostationary orbits propulsion systems of two types are most widely used: chemical and electric. Each type has its advantages and disadvantages. The application of any one of them does not always satisfy conflicting requirements. A possible solution may be the use of a combined propulsion system consisting of a chemical and electric propulsion system. This combination allows the spacecraft to be launched faster than using only electric motors, and it is more efficient in terms of the payload mass than using only a chemical propul- sion system. Electric propulsion engines (plasma or ionic) need energy sources. Usually, solar batteries are used for these purposes. The idea of using such a combined propulsion system, consisting of a solar electric propulsion sys- tem and the Fregat upper stage, was considered within the “Dvina TM” research project. The use of such a propulsion system requires, even at the design stage, to determine the parameters of the various types of engines that make up its structure. For a reasonable choice it is necessary to have information about the influence of the various propulsion system parameters on the final characteristics of the maneuver. When putting a spacecraft into orbit, it is necessary for the spacecraft to overcome Van Allen belts while the ele- ments of its design are subjected to intensive action of charged particles, which can significantly limit the period of ac- tive existence. Using a combined propulsion system, it is possible to shorten the time of being in a field of high radiation level significantly. The aim of the study was to synthesize a method for estimating the effect of the combined propulsion system parame- ters on the integral dose of radiation accumulated during the maneuver, when putting a spacecraft into a geostationary orbit. Different variations of the combined propulsion system application (thrust variations) allow to optimize the maneuver of the spacecraft and to reduce the integral dose of radiation. As a result of the work, a method was proposed to evaluate the influence of the parameters of the combined propul- sion system taking into account the passage of the Earth radiation belts, the program was implemented, calculations were made and the results were analyzed.