Space debris are one of the main threats for an affordable and safe space exploration and exploitation. Even if launch of satellites stops now their number continue to grow due to collisions effects. Since satellites will be even more fundamental in human activity, launches stop is not a practicable solution. Thus, in order to try to almost freeze the problem an end-life decommissioning strategy is needed. For Low Earth Orbit satellites this strategy consist in a burning re-entry in atmosphere. To do this, a propulsive system is needed. Compactness, reliability, readiness, and construction simplicity make the technology of solid rocket motor very appealing for this purpose. On other hand, on solid rocket systems there is not any throttling capability at run-time, since pressure-time evolution is defined at the design phase. This lack of mission flexibility makes their missions sensitive to deviations. For this reason, the reliability of predictions and reproducibility of performances represent a primary goal in this field. Objective of this thesis is the investigation of solid rocket motor uncertainties through the application of the Monte Carlo method to a dedicated model of internal ballistics of D-SAT rocket motor and how they propagate on the re-entry trajectory. D-SAT is a satellite with the size of a 3 cube-sat units. It is a demonstrator and it will be the first artificial object to perform an active and controlled re-entry from Earth orbit. The Monte Carlo method is a numerical approach to statistics requiring the creation of a numerical model for the analysis of rocket performances. In this work, the internal ballistic model was based on 0-D quasi-steady equations with the introduction of 'correction factors' on regressive burning rate. Ballistic coefficient, efficiencies, mass and geometry of propellant, and the so-called correction factors are considered to investigate sources of uncertainties. Comparison between numerical and experimental data was accomplished. The Monte Carlo simulations on internal ballistic model give as result the propagation of uncertainties towards rocket performance parameters (burning time, maximum thrust and pressure, specific impulse and total impulse). A successively Monte Carlo simulation studies the propagation of internal ballistic uncertainty on the re-entry trajectory performance parameters (ΔV, delivered and effective total impulses, position of impact with atmosphere). Each source of uncertainty was analysed independently to verify its influence. Multivariate simulations with all uncertainties were done as well.
Per un'esplorazione e la commercializzazione dello spazio bisogna sempre più tenere in considerazione il problema dei detriti spaziali. Il loro numero è in continuo aumento non solo per il continuo lancio di satelliti in orbita, ma anche per effetti di collisioni. Per cercare di congelare il problema al numero attuale di detriti è necessario attivare una strategia di decommissione dei satelliti a fine vita. Per fare ciò, D-orbit propone di far effettuare ad un satellite in orbita bassa (LEO) un rientro controllato in atmosfera attraverso un motore a propellente solido. I motori a razzo a propellente solido sono molto utilizzati anche per la loro elevata affidabilità, compattezza e semplicità di costruzione, caratteristiche necessarie a questo proposito di utilizzo. Dall'altro lato la loro spinta nel tempo non può subire regolazioni ma rimane nei limiti delle variazioni sistemiche quella fissata durante il design del motore. Questo fa si che le missioni equipaggiate con propulsori solidi siano molto sensibili a variazioni dei parametri da quelli nominali di design. E' importante quindi avere una certa affidabilità nella previsione e riproducibilità delle performance del motore. In questo lavoro si è studiato come incertezze interne al motore solido di D-SAT, il satellite dimostratore che verrà lanciato in orbita ad Aprile 2017, si propagano sulle performance del motore stesso e sull'orbita finale di rientro in atmosfera. Il modello della balistica interna del motore è un modello quasi-stazionario 0-D a cui sono stati introdotto coefficienti correttivi sul rateo di combustione. L'analisi statistica delle performance è stata effettuata attraverso il metodo Monte Carlo.
Propagation of internal ballistics uncertainty over D-SAT de-orbiting maneuver
BENETTI, MOSE'
2015/2016
Abstract
Space debris are one of the main threats for an affordable and safe space exploration and exploitation. Even if launch of satellites stops now their number continue to grow due to collisions effects. Since satellites will be even more fundamental in human activity, launches stop is not a practicable solution. Thus, in order to try to almost freeze the problem an end-life decommissioning strategy is needed. For Low Earth Orbit satellites this strategy consist in a burning re-entry in atmosphere. To do this, a propulsive system is needed. Compactness, reliability, readiness, and construction simplicity make the technology of solid rocket motor very appealing for this purpose. On other hand, on solid rocket systems there is not any throttling capability at run-time, since pressure-time evolution is defined at the design phase. This lack of mission flexibility makes their missions sensitive to deviations. For this reason, the reliability of predictions and reproducibility of performances represent a primary goal in this field. Objective of this thesis is the investigation of solid rocket motor uncertainties through the application of the Monte Carlo method to a dedicated model of internal ballistics of D-SAT rocket motor and how they propagate on the re-entry trajectory. D-SAT is a satellite with the size of a 3 cube-sat units. It is a demonstrator and it will be the first artificial object to perform an active and controlled re-entry from Earth orbit. The Monte Carlo method is a numerical approach to statistics requiring the creation of a numerical model for the analysis of rocket performances. In this work, the internal ballistic model was based on 0-D quasi-steady equations with the introduction of 'correction factors' on regressive burning rate. Ballistic coefficient, efficiencies, mass and geometry of propellant, and the so-called correction factors are considered to investigate sources of uncertainties. Comparison between numerical and experimental data was accomplished. The Monte Carlo simulations on internal ballistic model give as result the propagation of uncertainties towards rocket performance parameters (burning time, maximum thrust and pressure, specific impulse and total impulse). A successively Monte Carlo simulation studies the propagation of internal ballistic uncertainty on the re-entry trajectory performance parameters (ΔV, delivered and effective total impulses, position of impact with atmosphere). Each source of uncertainty was analysed independently to verify its influence. Multivariate simulations with all uncertainties were done as well.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/134019