In the last decades, space exploration has been revolutionized: the invention of the CubeSat format in 1999 made access to space easier and cheaper. CubeSats are small satellites characterized by standardized dimensions, that exploit technological miniaturization and commercial-off-the-shelf components to reduce the cost of building satellites. For years, CubeSats have only been employed in low Earth orbit. Then, in 2018 NASA launched Mars Cube One, the first CubeSat mission to deep space, which proved that small satellites can safely reach Mars. This mission could pave the way for a future in which large numbers of satellites are employed to study the Solar System planets and minor bodies. However, for such a scenario to become reality, one more step needs to be taken. Currently, spacecraft operations rely completely on human supervision. This limits the amount of satellites that can simultaneously be controlled in deep-space. Therefore, to allow extensive interplanetary exploration, and to further reduce costs, autonomous CubeSats need to be developed. This is the focus of the EXTREMA (Engineering Extremely Rare Events in Astrodynamics for Deep-Space Missions in Autonomy) project, which aims to enable self-driving spacecraft that, once launched, can autonomously arrive at their target. In order to reach this objective, many engineering challenges have to be overcome. One of them is the development of a robust and reliable guidance algorithm, that will compute the optimal trajectory from the spacecraft to the target. This algorithm will be tested via a hardware-in-the-loop experiment, which will simulate the behaviour of the satellite during its interplanetary transfer. This thesis deals with some of the tools necessary for the realization of the experiment. First, the orbit propagator that will be employed in the simulation is validated, by comparing its results with those of NASA's General Mission Analysis Tool. Then, an uncertainty propagation tool is developed, in order to estimate the uncertainty on the spacecraft state during the transfer. Finally, a detailed architecture of the experiment is devised, and an Earth-Mars transfer is simulated.
Nelle ultime decadi, l'esplorazione spaziale è stata rivoluzionata: l'invenzione del formato CubeSat, nel 1999, ha reso l'accesso allo spazio più semplice e più economico. I CubeSat sono piccoli satelliti caratterizzati da dimensioni standard, che sfruttano miniaturizzazione tecnologica e componenti commerciali per ridurre i costi di sviluppo. Per anni, i CubeSat sono stati utilizzati solo nella bassa orbita terrestre. Poi, nel 2018, la NASA ha lanciato Mars Cube One, la prima missione CubeSat verso lo spazio profondo, la quale ha dimostrato che questi piccoli satelliti possono raggiungere Marte in modo sicuro. Tale missione potrebbe gettare le basi per un futuro in cui i CubeSat sono utilizzati per studiare i pianeti e i corpi minori del Sistema Solare. Tuttavia, affinché tale scenario diventi realtà, è necessario compiere un ulteriore passo. Attualmente, i satelliti sono interamente controllati da operatori umani. Ciò limita la quantità di veicoli spaziali che possono essere controllati simultaneamente. Perciò, per rendere possibile una vasta esplorazione interplanetaria, e ridurre ulteriormente i costi, bisogna rendere i CubeSat autonomi. Questo è il focus del progetto EXTREMA (Engineering Extremely Rare Events in Astrodynamics for Deep-Space Missions in Autonomy), il quale punta a rendere possibili i satelliti auto-guidati che, una volta lanciati, possono raggiungere autonomamente la loro destinazione. Per raggiungere questo obiettivo è necessario superare molte sfide ingegneristiche; una delle principali è lo sviluppo di un algoritmo di guida affidabile e robusto, per calcolare la traiettoria ottimale dal satellite al target. L'algoritmo sarà testato tramite un esperimento integrato, che simulerà il comportamento del satellite durante la fase di trasferimento interplanetario. Questa tesi si occupa di alcuni degli elementi necessari per la realizzazione dell'esperimento. Innanzitutto, il propagatore orbitale impiegato nella simulazione è validato, comparando i risultati con quelli del software NASA General Mission Analysis Tool. Successivamente, un algoritmo per la propagazione dell'incertezza è sviluppato, per stimare l'incertezza sullo stato del satellite durante il trasferimento. Infine, un'architettura dettagliata dell'esperimento è studiata, e un trasferimento Terra-Marte è simulato.
Numerical simulations for the design of a hardware-in-the-loop experiment for interplanetary CubeSats
Piccolo, Felice
2019/2020
Abstract
In the last decades, space exploration has been revolutionized: the invention of the CubeSat format in 1999 made access to space easier and cheaper. CubeSats are small satellites characterized by standardized dimensions, that exploit technological miniaturization and commercial-off-the-shelf components to reduce the cost of building satellites. For years, CubeSats have only been employed in low Earth orbit. Then, in 2018 NASA launched Mars Cube One, the first CubeSat mission to deep space, which proved that small satellites can safely reach Mars. This mission could pave the way for a future in which large numbers of satellites are employed to study the Solar System planets and minor bodies. However, for such a scenario to become reality, one more step needs to be taken. Currently, spacecraft operations rely completely on human supervision. This limits the amount of satellites that can simultaneously be controlled in deep-space. Therefore, to allow extensive interplanetary exploration, and to further reduce costs, autonomous CubeSats need to be developed. This is the focus of the EXTREMA (Engineering Extremely Rare Events in Astrodynamics for Deep-Space Missions in Autonomy) project, which aims to enable self-driving spacecraft that, once launched, can autonomously arrive at their target. In order to reach this objective, many engineering challenges have to be overcome. One of them is the development of a robust and reliable guidance algorithm, that will compute the optimal trajectory from the spacecraft to the target. This algorithm will be tested via a hardware-in-the-loop experiment, which will simulate the behaviour of the satellite during its interplanetary transfer. This thesis deals with some of the tools necessary for the realization of the experiment. First, the orbit propagator that will be employed in the simulation is validated, by comparing its results with those of NASA's General Mission Analysis Tool. Then, an uncertainty propagation tool is developed, in order to estimate the uncertainty on the spacecraft state during the transfer. Finally, a detailed architecture of the experiment is devised, and an Earth-Mars transfer is simulated.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/170983