Digital archive of theses discussed at the University of Pisa


Thesis etd-08312018-100117

Thesis type
Tesi di laurea magistrale
Thesis title
Kick Stage design for small satellites in the framework of satellites constellation.
Course of study
relatore Prof. Marcuccio, Salvo
  • Green propulsion
  • Kick stage
Graduation session start date
Release date
This dissertation aims to design a kick stage for the small satellite platform of LuxSpace Sarl. The design is carried out under the framework of a theoretical mission involving a constellation of six small satellites. The objective of the thesis is to demonstrate the feasility of a kick stage design being implemented as the primary propulsion system for orbital transfers of a small satellite. Starting with the state of the art and mission scenario analysis, the transfer requirements to be achieved by the kick stage are realised. Three satellites each are to be placed in two operational orbits having the same plane with an inclination 63.4° and eccentricity 0.2098 but with one having the apogee in the northern hemisphere and the other having an apogee in the southern hemisphere. The perigee has an altitude of 400 km and the apogee has an altitude of 4000 km. The Kick Stage is required to provide for an orbital transfer from the launcher parking orbit to the working position in the operational orbit. This is done by first a semi major axis increase burn to move into the operational orbit and then a 10 day phasing maneuver to facilitate the phasing requirement of the constellation. Preliminary propulsion system design has been carried out using the inputs of the requirements of the mission scenario. The analysis of the propellant chemistry is demonstrated by using a frozen chemistry script. Conservative assumptions of specific heat ratio and molecular mass are assumed from the literature for the selected propellants to converge to a final propellant selection of ADN. The thermochemical analysis is carried out using NASA CEA software to provide a more accurate results of specific heat ratio k = 1.22 and molecular mass M = 24.8 for the selected ADN propellant. The frozen chemistry script provides the performance results of the preliminary propulsion system design. The Kick Stage is designed to have a specific impulse of 191.5 seconds, which when coupled with a thrust of 190 N it shall have a burn time of 13.8 minutes to satisfy a deltaV requirement of 800 m/s. In the initial design phase, a conservative dry mass for the system was selected. The calculation of the burn time however lacked the provision to include the propellant mass change with the respective burns. Not inclusion of dynamic propellant mass change causes the script to calculate a larger than needed propellant mass. This has been rectified by developing a script that negates the spent propellant mass from the total mass with every instant of burn time. The kick stage is defined to be fully autonomous and hence the propulsion system design is followed by preliminary subsystem design. ADCS subsystem is required to satisfy a large parasite torque caused by the thrust misalignment. The ADCS thrusters are designed to provide a high duty cycle to satisfy the disturbance torques. Two structural designs have been analysed and their applicability has been verified by Modal structural analysis to verify the suitability with the vibrational requirement of 50 Hz for the structural frame. The initial preliminary system design provides the results of mass budgets. The dry system mass as it turns out to be different than the previously assumed value has to be accommodated in the total impulse rectification script to recompute the required propellant mass. The new propellant mass requires a different tank and hence causes the structural frame to be re-designed. This loop of system design is re-iterated until an error of less than 3% is achieved between the values of the initial system mass and final system mass. The concluded design has a dry mass of 69.4 kg and a wet (dry + propellant + satellite) mass of 244 kg.
The use of a Kick Stage is found to be a beneficial solution as it provides for an effective orbital transfer in a shorter period of time as compared to an electric propulsion device. The engine shall be one of its kind high performance green propellant thruster.mass