Space Exploration Systems, Strategies and Solutions

The present thesis describes the PhD research activities dealing with the topic “Space Exploration Systems, Strategies and Solutions”. Traveling beyond low Earth orbit is the next step in the conquest of the solar system and so far, a human expedition to Mars is considered the most interesting goal of future human space exploration. Due to the technological and operational challenges associated with such a mission, it is necessary to define an opportune path of exploration, relying on many missions to intermediate and “easier” destinations, which would allow a gradual achievement of the capabilities required for the human Mars mission. The main scope of this research has been the development of a rigorous and versatile methodology to define and analyze evolutionary exploration scenarios and to provide a detailed technologies’ database, to support strategic decisions for human space exploration. The very innovative aspect of this work regards the development of a flexible methodology which can be followed to assess which are the next destinations for the exploration of space beyond LEO and to preliminarily define mission’s architectures, identifying the most significant needed elements and advanced technologies. The obtained results should be seen as a pure technical reference, as no cost and/or political considerations have been included, and can be exploited to opportunely drive the decisions of the agencies to place investments for the development of specific technologies and get ready for future exploration missions. The first part of the work has been devoted to the definition of a reference human space exploration scenario, which relies on both robotic and human missions towards several destinations, pursuing an increasing complexity approach and looking at a human expedition to Mars as final target. The scenario has been characterized through the assessment of the missions and the relative phases and concepts of operations. Accordingly, the needed space elements, or building blocks, have been identified. In this frame, the concept design of two specific elements has been performed: the first is a pressurized habitation module (Deep Space Habitat) for hosting astronauts during deep space missions; the second is an electrical propulsive module (Space Tug), mainly envisioned for satellites servicing. The last part of the work has focused on the analysis of innovative and enabling technologies, with particular attention to the aspects related to their on-orbit demonstration/validation, prior to their actual implementation in real exploration missions. The PhD has been sponsored by Thales Alenia Space - Italy and the overall work has been performed in different frameworks along the three years, as well as participating to several additional activities. In line with the objectives of the PhD, in 2012 a collaboration between Politecnico di Torino and Massachusetts Institute of Technology has been established (MITOR Project, managed by MIT-Italy Program), with the support of Thales Alenia Space as industrial partner. The MITOR project, titled “Human Space Exploration: from Scenario to Technologies”, has been aimed at identifying and investigating state of the art for Human Space Ex- ploration, enabling elements, subsystems and technologies with reference to a selected scenario and relevant missions and architectures. Part of the nine months activities has been carried out at MIT AeroAstro department. Besides MITOR project, the PhD activities have been carried out in synergy with some other research programs, such as ESA “Human Spaceflight & Exploration Scenario Studies” and STEPS2 project (Sistemi e Tecnologie per l’EsPlorazione Spaziale - phase 2). Furthermore, in 2013 a specific study has been performed in collabora- tion with university “La Sapienza” (Rome), “Osservatorio Astrofisico di Torino” (Astrophysical Observatory of Torino) and DLR (Deutsches Zentrum fr Luft- und Raumfahrt) in Bremen; its main objective has been the analysis of an interplanetary cubesats mission, aimed at space weather evaluations and technologies demonstration

A DEEP SPACE HABITAT FOR EXPLORATION

The paper describes a habitable module to be used for long duration space exploration missions. The Deep Space Habitat (DSH) is conceived as a cis-lunar orbital infrastructure and a space-ship for deep space exploration missions. It will represent the first outpost beyond LEO, being deployed at the first Earth-Moon Lagrangian point (EML1), and is envisaged as a human-tended infrastructure with crew visits periodically foreseen. The DSH has to be firstly used as a platform for research and to demonstrate a set of critical technologies and associated operations required to perform a deep space human exploration mission (e.g. to a NEO). In this regard, placing the module at EML1 allows reproducing conditions that would be encountered during a travel to an asteroid (or to Mars), thus guaranteeing the possibility to test specific technologies in a more significant environment with respect to what possible on ground or in LEO (e.g. effects of radiations on human body outside the protection of the Van Allen belts and radiation protection system test). Besides being a technology test bed, the DSH will support lunar human exploration missions, providing a staging post and a safe haven for crew working on the Moon surface. The overall architecture of the DSH has derived from a set of system trade-off performed accordingly to the objectives to be accomplished: the most important features are described within the paper. The DSH deployed at EML1 can be seen as a first unit to be utilized as a precursor for a habitation module to be actually adopted for hosting the crew during a deep space mission (to a NEO or to Mars). Indeed, a second unit is envisaged, which exploits the experience gained through its precursor, having a common core with it and implementing technologies previously tested on it. Only minor changes shall be envisioned due to the peculiarities of the mission for which it is used. In particular, the description of the second unit presented in the paper refers to a specific reference mission to a NEO lasting one year. The first part of the paper focuses on the main performed trade-offs, as well as the obtained results, in terms of both system architecture and operations, highlighting the major differences between the two envisioned units. The second part is devoted to the critical and enabling technologies, with particular attention to advanced regenerative ECLSS, rapid prototyping and radiation protection syste

Conceptual design of a habitation module for a deep space exploration mission

The paper deals with the conceptual design of a habitable module conceived for long duration space exploration missions. The pressurized habitation module (HAB) was specifically sized for a Near Earth Asteroid (NEA) mission, named AENEA ―humAn Exploration mission to a Near Earth Asteroid‖. This mission is conceived as an intermediate step before going to further destinations and aims at testing technologies necessary for reaching more challenging targets. In accordance to the mission objectives, the HAB was devised as a reusable space infrastructure, suitable for different exploration scenarios with only minor changes in the architecture/design. The paper describes the design process that, starting from the mission statement, was followed to define the objectives, the requirements and the architecture of the module in terms of system and subsystems configuration. In particular, the HAB was designed to safely sustain the life of 4 astronauts, for a mission to a NEA lasting about 6 months. The main subsystems of the HAB were sized in order to provide the astronauts with the needed resources, support the activities during all operational phases, including the Extra Vehicular Activities (EVA) on the asteroid's surface, and protect them against the external environment, with particular attention to the space radiation, one of the most critical aspects of this kind of mission. In this regard, appropriate analyses were carried out for selecting the best shielding strategy. For the execution of the EVAs on the asteroid surface, a dedicated airlock and specific EVA support tools were included. The paper reports a detailed description of the subsystems and their innovative aspects. Starting from the mission phases and the related scenarios, different modes of operations were identified. System budgets were evaluated for the envisaged operational modes. The paper illustrates both the applied methodologies and the results, highlighting the major criticalities to be faced (long exposure to space radiations, EVA operations on the asteroid surface) and the key technologies (radiation shielding, inflatable technology, EVA support tools

Diseño conceptual del subsistema de comunicaciones de un sistema CubeSat interplanetario

En el Proyecto Fin de Carrera se plantea el estudio de alternativas de comunicación de un satélite CubeSat con la Tierra para señales de radiofrecuencia y para señales ópticas. El objetivo es disponer de datos suficientes para decidir cuál sería la opción más adecuada. La tecnología CubeSat consiste en un tipo de picosatélites que se forman con la unión de varios cubos de 10cm de lado y aproximadamente 1kg. Últimamente ha habido un desarrollo de estos tipos de sistemas debido al avance en la tecnología, consiguiendo sistemas de tamaño cada vez más pequeño, lo que permite una reducción bastante significativa del coste de dichas misiones. El satélite para el cuál se va a realizar el estudio es un módulo de 6 unidades que se situará en el Punto de Libración L1 entre el Sol y la Tierra y tendrá como objetivo realizar medidas solares y de las condiciones climatológicas del universo. En cuanto a la comunicación se refiere, el uso de señales de radiofrecuencia ha sido la técnica utilizada hasta el momento para misiones espaciales ya que permite la realización de la comunicación con una amplia cobertura utilizando reflectores parabólicos que dotan a la señal de una alta ganancia. Sin embargo, en los últimos años se ha considerado la posibilidad de la utilización de señales ópticas para este fin. Dichos sistemas concentran la potencia en menos espacio por lo que pueden utilizarse en enlaces de gran distancia, soportando mayor tasa de datos y su peso y dimensiones son menores. En este trabajo, se realizará el análisis del enlace con diversas combinaciones de posibles escenarios en los que se utilicen tanto sistemas de radiofrecuencia como sistemas ópticos. Los resultados obtenidos servirán para valorar el tipo de sistema más adecuado

FUTURE SPACE EXPLORATION: FROM REFERENCE SCENARIO DEFINITION TO KEY TECHNOLOGIES ROADMAPS

The human exploration of multiple deep space destinations (e.g. Cis-lunar, NEAs), in view of the final challenge of sending astronauts to Mars, represents a current and consistent study domain especially in terms of its possible scenarios and mission architectures assessments, as proved by the numerous on-going activities about this topic and moreover by the Global Exploration Roadmap. After exploring and analysing different possible solutions to identify the most flexible path, a detailed characterization of one out of several Design Reference Missions (DRM) represents a necessity in order to evaluate the feasibility and affordability of deep space exploration missions, specifically in terms of enabling technological capabilities. A human expedition to a NEA, milestone of the GER ‘Asteroid Next' scenario, is considered the mission that would offer the largest suite of benefits in terms of scientific return, operational experience and familiarity on human deep space missions, test of technologies and assessment of human factors for future long-duration expeditions (including planetary bodies), evaluation of In-Situ Resource Utilization (ISRU) and, more specifically, opportunity to test asteroid collision avoidance techniques. The study started from the identification and analysis of feasible evolutionary scenarios for Deep Space Exploration. Different destinations were considered as targets, with particular attention to Earth-Moon Lagrangian points, NEA and Mars as an alternative path to a Moon campaign. In the frame of the scenario selected as the preferable one, a DRM to a NEA (reference target) was defined in detail in terms of architecture and mission elements, as well as of the subsystems composing them. Successively, the critical subsystems and the relevant key technologies were investigated in detail, from their status-of-the-art up to an assessment of their development roadmaps. They shall enable the DRM and support the whole scenario. The paper describes the process that was followed within the study and reports the major obtained results, in terms of scenarios and mission analysis. Furthermore the key technologies that were identified are listed and described highlighting the derived roadmaps for their development according to the reference scenario

Reusable space tug concept and mission

The paper deals with the conceptual design of a space tug to be used in support to Earth satellites transfer ma-noeuvres. Usually Earth satellites are released in a non-definitive low orbit, depending on the adopted launcher, and they need to be equipped with an adequate propulsion system able to perform the transfer to their final operational location. In order to reduce the mass at launch of the satellite system, an element pre-deployed on orbit, i.e. the space tug, can be exploited to perform the transfer manoeuvres; this allows simplifying the propulsion requirements for the satellite, with a consequent decrease of mass and volume, in favour of larger payloads. The space tug here presented is conceived to be used for the transfer of a few satellites from low to high orbits, and vice versa, if needed. To support these manoeuvres, dedicated refuelling operations are envisaged. The paper starts from on overview of the mission scenario, the concept of operations and the related architecture elements. Then it focuses on the detailed definition of the space tug, from the requirements' assessment up to the budgets' development, through an iterative and recursive design process. The overall mission scenario has been derived from a set of trade-off analyses that have been performed to choose the mission architecture and operations that better satisfy stakeholder expectations: the most important features of these analyses and their results are described within the paper. Eventually, in the last part of the work main conclusions are drawn on the selected mission scenario and space tug and further utilizations of this innovative system in the frame of future space exploration are discussed. Specifically, an enhanced version of the space tug that has been described in the paper could be used to support on orbit assembly of large spacecraft for distant and long exploration missions. The Space Tug development is an activity carried on in the frame of the SAPERE project (Space Advanced Project Excellence in Research and Enterprise), supported by Italian Ministry of Research and University (MIUR), and specifically in its STRONG sub-project (Systems Technology and Research National Global Operations) and related to the theme of space exploration and access to space

A methodology to support strategic decisions in future human space exploration: from scenario definition to building blocks assessment

The human exploration of multiple deep space destinations (e.g. Cis-Lunar, NEAs), in view of the final challenge of sending astronauts to Mars, represents a current and consistent study domain especially in terms of its possible scenarios and mission architectures assessments, as proved by the numerous on-going activities about this topic and moreover by the global exploration roadmap. After exploring and analysing different possible solutions to identify the most flexible path, a detailed characterisation of several Design Reference Missions (DRMs) represents a necessity in order to evaluate the feasibility and affordability of deep space exploration missions, specifically in terms of enabling technological capabilities. The study presented in this paper was aimed at defining an evolutionary scenario for deep space exploration in the next 30 years with the final goal of sending astronauts on the surface of Mars by the end of 2030 decade. Different destinations were considered as targets to build the human exploration scenario, with particular attention to Earth-Moon Lagrangian points, NEA and Moon. For all the destinations selected as part of the exploration scenario, the assessment and characterisation of the relative Design Reference Missions were performed. Specifically they were defined in terms of strategies, architectures and mission elements. All the analyses were based on a pure technical approach with the objective of evaluating the feasibility of a long term strategy for capabilities achievement and technological development to enable future space exploration. This paper describes the process that was followed within the study, focusing on the adopted methodology, and reports the major obtained results, in terms of scenario and mission analysi

Interplanetary CubeSats system for space weather evaluations and technology demonstration

The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats system to be implemented in the L1 Earth-Sun Lagrangian Point mission for solar observation and in-situ space weather measurements. Interplanetary CubeSats could be an interesting alternative to big missions, to fulfill both scientific and technological tasks in deep space, as proved by the growing interest in this kind of application in the scientific community and most of all at NASA. Such systems allow less costly missions, due to their reduced sizes and volumes, and consequently less demanding launches requirements. The CubeSats mission presented in this paper is aimed at supporting measurements of space weather. The mission envisages the deployment of a 6U CubeSats system in the L1 Earth-Sun Lagrangian Point, where solar observations for in situ measurements of space weather to provide additional warning time to Earth can be carried out. The proposed mission is also intended as a technology validation mission, giving the chance to test advanced technologies, such as telecommunications and solar sails, envisaged as propulsion system. Furthermore, traveling outside the Van Allen belts, the 6U CubeSats system gives the opportunity to further investigate the space radiation environment: radiation dosimeters and advanced materials are envisaged to be imple- mented, in order to test their response to the harsh space environment, even in view of future implementation on other spacecrafts (e.g. manned spacecrafts). The main issue related to CubeSats is how to fit big science within a small package - namely power, mass, volume, and data limitations. One of the objectives of the work is therefore to identify and size the required subsystems and equipment, needed to accomplish specific mission objectives, and to investigate the most suitable configuration, in order to be compatible with the typical CubeSats (multi units) standards

ITINERANT HUMAN OUTPOST FOR FUTURE SPACE EXPLORATION

The exploration of space has so far been attempted only through a limited sequence of missions, not strictly linked among them in terms of accumulation of achieved experience and hardware utilization. The paper presents an innovative approach to the exploration of regions beyond Low Earth Orbit, which is assumed to occur through an orderly sequence of interlinked missions, targeted to specific locations, where human outposts are put in place, to progressively enlarge the boundaries of human presence in the Solar System. Each human outpost is built "on the shoulders" of the precedent one, through physical transfer at the new location of all or at least some of the major building blocks of the previous outpost. Dedicated building blocks may also be considered to build up the final architecture of the new outpost. The new approach proposes therefore the development of an "Itinerant Human Outpost" for future space exploration, growing eventually in complexity and transforming itself. At each step of the space exploration journey the outpost is utilized as technology and operation test-bed to prepare the "next step". The sequence of locations starts with an Equatorial Low Earth Orbit Human Outpost. Next locations are Earth-Moon Lagrangian Points, Near Earth Asteroids Region, Low Lunar Orbits and Martian Orbits to finally build up Martian human outposts in Low Martian Orbits or on one Martian natural satellite. The overall scenario can be considered the "Grand Tour of the Earth Neighbours", performed by the "Itinerant Human Outposts", whose successive multiple utilization and growth potential have to be taken into account as design requirements of each building block. The practice of introducing in the design the "Revolutionary Approach" of the "6R Space Systems", i.e. the "Repairable, Refurbishable, Replaceable, Reconfigurable, Retrievable and Reusable Space Systems", has to be adopted as well, in order to optimize in the long term the costs of the outposts building up and of their operations, even if in the front end such an approach requires more complex and costing solutions. The paper describes into some detail the proposed new approach, establishes the main requirements and defines the System of Systems Architecture of the first Human Outpost in Equatorial Low Earth Orbit. The significant endeavours, required to sustain over quite a long period of time such an initiative, are going to offer to new generations perspectives that will act as catalyst of economical growth and will encourage the involvement of the Private Secto

How does the human presence impact a mission to a Near Earth Asteroid?

The paper deals with the major impacts that the human presence has on an exploration mission to a Near Earth Asteroid. This topic was addressed in the framework of the fifth edition of the postgraduate SEEDS Master course, which aimed at the preliminary design of a human exploration mission to a NEA, called AENEA. A mission to an asteroid may be seen as an intermediate step before going to further destination such as Mars, since it offers the possibility to test several capabilities, both in terms of technologies and human aspects, required to reach further targets. The target of AENEA mission is the 1999 RA32 asteroid. The mission has an overall duration of about 6 months and the maximum distance between Earth and the spacecraft reached during the travel is about 0.2 AU. Many benefits would derive by the presence of humans in such kind of mission, with respect to having only robotics. As a matter of fact, the asteroid is a harsh and not known environment and the flexibility and capabilities of humans would be necessary to eventually face in an easier and more efficient way not expected situations, and avoid the risk of compromising the entire mission. Of course, a human mission is usually more complex, and consequently more costly, than a robotic one due to several issues that must be accounted for, as for example the effects of the long exposure to space radiations or to microgravity. Moreover, the long duration and the far distance from Earth make AENEA a very challenging mission even from a psychological point of view. Particular attention was devoted to this aspect in designing the mission, both in terms of systems and operations. The paper highlights the advantages of having humans in this kind of exploration mission, describing the major implications it has on the design of the entire mission. Furthermore, the importance of a having a complementary contribution of both robotics and human capabilities for such kind of mission robotic contribution is underline