Research On Nutation Instability Process And Restrain Program For Rotating Rocket

For the nutation instability during the launching process of rotating rocket spacecraft,adopting the combination method of the theoretical analysis and numerical simulation, thereason of the nutation amplification of rotating rocket spacecraft was researched, the restrainscheme of the nutation amplification was propsed.From the general definition of variable mass system, a integral and rigorousmathematical equations has been derived. It can be easily applied to the actual rotating rocketspacecraft systems after a reasonable assumption and simplification. It was found that thethrust vector and the Coriolis force are the main force which are generated by the massvariation of the rotating rocket spacecraft. Because of the mass variation of the spacecraft, Jetdamping torque and the torque generated by inertia are the main torques which affect theattitude motion. Axisymmetric model with dual body has being used to study the influence ofthe mass variation of motor on the spacecraft attitude. Three propellant model of end burnpropellant, internal and external burn propellant, internal and end burn propellant wasresearched. The variation of mass and moment of inertia caused by the combustion way ofthese three propellant was calculated accurately. The variation law of axial angular rate andlateral angular rate of spacecraft using the three propellant model was given. It was found thatnozzle/propellant diameter ratio has a greater effect on rotation angular rate of the spacecraftsystem, and the aspect ratio of propellant has a greater effect on lateral angular rate of thespacecraft system. When the end burn propellant was used, appropriate nozzle/propellantdiameter ratio and propellant aspect ratio can make the rotation angular rate of the spacecraftstable, simultaneously the lateral angular rate is dissipated rapidly. When the internal andexternal burn propellant model was used, appropriate nozzle/propellant diameter ratio andpropellant aspect ratio also be used to make the rotation angular rate of the spacecraft stableand the lateral angular rate dissipated rapidly. When the internal and end burn propellant wasused, the lateral angular rate of spacecraft was diverged. From other side, it explains thereason that lateral angular rate amplification rapidly is related to the mode of propellant in theworking process of rotating spacecraft which uses the STAR-48motor, indicating that thesemode of propellant do not apply to rotating spacecraft. From the standpoint of the energy dissipation caused by the mas reduction of thespacecraft system, the equations of angular rate and nutation of spacecraft system wasdeduced, and was calculated through a appropriate method. The parametric variation ofspacecraft with rotating nutation instability was calculated using this method. The effects ofother parameters variation of spacecraft on the variation of the angular rate and nutation angleof the spacecraft system was studied. It was found that the axial moment of inertia, the lateralmoment of inertia, the mass flow, the center of gravity and other parameters all have effectson the process of nutation of spacecraft systems. The effect of nutation of spacecraft systemcan be changed by changing these parameters. Through increasing the axial moment of inertiaof spacecraft systems, reducing the lateral moment of inertia, the position of mass center andmass flow of motor, the effects of nutation of spacecraft system can be weakened; conversely,the effect of nutation can be enhanced.The internal flow field of rotating solid rocket motor was simulated by using the methodof Euler-Lagrange gas-solid two phase flow. It was found that in the later period ofcombustion of rotating motor, with the chamber radius increasing, the Coriolis force increasedgradually, at the same time, the particles in the chamber coupled with rotating of spacecraftand gathering in the after zone of submerged nozzle under the effect of combustion gas flow.In order to describe the effect on spacecraft movements caused by particles which gatheringin the after zone of submerged nozzle, it was proposed that using the movement of a mass ballin the chamber to simulate the movement of aggregated particles. The motion equations of thespacecraft at the time of the ball moving was derived, when the actual spacecraft parameterswas put into this motion equations to calculate, it was achieved that the increasing of lateralangular rate of spacecraft consistent with the measured law. It shows that the proposedcomputational model in this text can be used to predict the increase of lateral angular rate ofthe spacecraft which have the movements of the condensed phase Al₂O₃slag in the chamber,and in the other side, it was can be confirmed that the movements of the condensed phaseAl₂O₃slag is one of the reasons that nutation instability of rotating spacecraft.Contraposing the phenomenon of nutation instability in the working process of rotatingspacecraft solid rocket motor, combining with the characteristics of nutation damper, theone-dimensional movement nutation damper control model and the two-dimensionalmovement nutation damper control model was proposed to suppress the nutation process. By simplifying the model, motion equations of two models was derived. The Routh criterionwas used to analysis the stability of the one-dimensional movement nutation damper controlmodel, it was found that under the effect of the one-dimensional movement nutation damper,when the damper located after the mass center of the spacecraft, as long as the thrust of thespacecraft and the coefficient of elasticity of the damper spring are large enough, themaximum axis stability rules of the moment of inertia of the slender body rotating spacecraftcan be changed, make it to rotate steadily around the axis of the minimum moment of inertia.So the one-dimensional movement nutation damper control model can the damp the nutationof the slender body rotating spacecraft, and make it to rotate steadily. The Lyapunov secondmethod was used to analysis the stability of the two-dimensional movement nutation dampercontrol model, it was found that under the effect of the two-dimensional movement nutationdamper, the maximum axis stability rules of the moment of inertia of the slender body rotatingspacecraft also can be changed, make it to rotate steadily around the axis of the minimummoment of inertia, and play a role in the nutation of the rotating spacecraft. Through theperturbation analysis method, the nutation damping time constant of two kind of nutationcontrol program was given, when designing the nutation program, should make the nutationdamping time constant of the system is least, that making the system stable in the least time.Using the method of numerical simulation to calculate the motion state of the spacecraft withthe two kind of control program, verifying the result of the stability analysis, assessing thesuppression effect of the nutation control program on the spacecraft, it was found that both ofthe two programs can have damping effects on in big margin nutation swing of the rotatingspacecraft. The damping effect of the two-dimensional movement nutation damper controlmodel is better than one-dimensional, it can make the nutation of spacecraft stabilize morequickly.