International Journal of Satellite Communications and Networking
The rise of the commercial space industry has resulted in the development of megaconstellations t... more The rise of the commercial space industry has resulted in the development of megaconstellations that promise to provide global broadband. These constellations capitalize on advancements in technology, improved modeling capabilities, and reductions in launch cost. One of the significant open questions is whether these constellations will significantly increase access for uncovered and underserved communities, in addition to serving existing markets. This paper analyzes which constellation characteristics provide the best global coverage at the lowest operational cost. First, we present the demand model that assesses the number of under-served and uncovered users in a given region. Then, we present a genetic algorithm used to identify potential constellations. Finally, we conclude by identifying which characteristics are the most promising for broadband constellations, as well as predictions of how the market will develop in the coming years. Our analysis has found that geostationary (GEO) and medium Earth orbit (MEO) satellite constellations have the highest likelihood of profitability. LEO networks are on average 27% more expensive, but if designed wisely, they can be competitive. Our work shows that there are diminishing returns with large constellations, and that it is more cost effective to have a small number of highly capable satellites, rather than many low complexity satellites. Key technologies like high frequency bands and miniaturization of components can lead to further cost reductions and increase the competitiveness of LEO constellations.
This paper introduces a method for Model-based Ontology Coverage Analysis (MOCA) and applies it t... more This paper introduces a method for Model-based Ontology Coverage Analysis (MOCA) and applies it to SysML models of mission architectures. An ontology is a set of concepts that constitute a common language, standard terminology, and consistent pattern reference across multiple models within an organization, industry, or domain. The purpose of MOCA is to assess the overlap between a system architecture model and a given ontology, and thereby the architecture model's compliance with the ontology and the ontology's utilization by the architecture. We demonstrate MOCA on a SysML model of a humanitarian airlift mission, using a conceptual mission architecting SysML profile model that serves as the ontology. MOCA automates and simplifies reasoning over models, and creates digital model-based artifacts that support stakeholders in concept validation, decision making, and system/mission design. Thus, MOCA enhances digital systems engineering.
A renewed interest in lunar exploration with the focus on establishing a constant human presence ... more A renewed interest in lunar exploration with the focus on establishing a constant human presence on the Moon calls for developing new lunar human landing systems (HLS) which would deliver the crew from the prospective Lunar Gateway station to the surface of the Moon and back. Over the years, different human lunar lander architectures were proposed and multiple architecture studies were performed. However, those studies are relevant to the specific assumptions and lunar architectures proposed at the time of conducting the study. Since the current vision for lunar exploration includes new features, such as having the Lunar Gateway and switching to reusable systems, there is a need for a new HLS architecture study. Such studies are being performed by private companies; however, those are rarely publicly available. The goal of this paper is to address this gap and provide a publicly available architectural analysis within the current views on the future human lunar exploration. We assume the Lunar Gateway in an L2 near rectilinear halo orbit and a landing site at the lunar South Pole; the number of HLS crew of 4; the surface stay time of ~ 7 days, the payload mass delivered to the surface of 500 kg, and the payload mass returned from the surface of 250 kg. A set of parametric models including an HLS model and an HLS program cost model is developed for the analysis. 39 architectures with varying number of stages (1, 2, and 3 stages) and propellant combinations (LOX/LH2, LOX/CH4, and MMH/NTO) are explored. The Pareto analysis shows that there is a difference between typical performance trends for expendable and reusable architectures. For expendable architectures, the 2-stage option seems to be the most advantageous while, for reusable architectures, the 1-and 3-stage options are either comparable or win over the 2-stage option even for the number of system uses as low as 3. In terms of the propellant combinations, pure LOX/LH2 or combined LOX/LH2/LOX/CH4 architectures dominate the tradespace. Assuming that the inter-stage propellant compatibility is a preferred option for systems refueling from the Gateway, 1-stage and 3-stage all LOX/LH2 architectures are identified as the likeliest candidates to have lowest HLS-related production and launch costs. Further cost analysis of those two architectures shows that the 1-stage HLS wins over the 3-stage system in terms of the overall HLS program cost if a long-term exploration program (on the order of tens of missions) is assumed.
The digital transformation era is upon us. Digital transformation gradually crawls up the value c... more The digital transformation era is upon us. Digital transformation gradually crawls up the value chain from services and manufacturing to product design and systems engineering. In this paper we envision a cloud-based ecosystem of systems engineering, which is model-based by definition. The ecosystem model we propose is called 2MIDSTARs, which stands for: Model, Infrastructure, Data Services, Simulation, Testing, Analysis, and Repositories + Management, Interoperability, Digital Representation, System, Technology, Audit, and Reporting. The first MIDSTAR covers the intrinsic, core MBSE capabilities, while the second MIDSTAR facilitates the integration with the digital enterprise that surrounds the digital systems engineering ecosystem. In this paper we explain the importance of jointly considering all these elements together and outline the key roles and functionalities of each component.
A Digital Engineering Information Exchange supports an exchange of digital artifacts between syst... more A Digital Engineering Information Exchange supports an exchange of digital artifacts between system engineering entities (INCOSE). Such entities might include processes, models, and organizational elements associated with space missions design. Reducing complexity and errors, as well as improving efficiency are critical capabilities associated with a digital transformation of space missions design and delivery. In our work we propose an approach to manage a digital engineering information exchange through the DSM-based approach (Eppinger and Browning 2012). Applied to space systems architecture, the method allows keeping track of the information exchange throughout the product development. Such information includes the core entities and relationships of CubeSat’s subsystems. This would integrate systems engineering (MBSE) approaches and PLM methods. In our paper we apply the proposed approach to a CubeSat mission design. One of the forms of utility of the proposed approach is the ab...
Projects of the New Space economy such as SpaceShipTwo and New Shepard are on their way to shifti... more Projects of the New Space economy such as SpaceShipTwo and New Shepard are on their way to shifting the paradigms in space tourism and transportation. Being privately financed, they are also changing the way in which highly complex and formerly government-financed systems are now being developed. Looking to the future, we can envision humanity moving to space, an opportunity that will be available to many more of us as a result of these new paradigms. One of the core issues we encounter when we start the development of complex systems such as the suborbital transportation and space tourism systems is: what are the concepts available and how can these concepts be represented using strictly defined ontology and model semantics? In this work we present a model-based concept framework that aims to address this issue. First a concept framework methodology is presented, after which we demonstrate its applicability to suborbital human spaceflight missions – SpaceShipTwo and New Shepard. Th...
Der Ansari X-Prize legte den Grundstein für den suborbitalen Weltraumtourismus. Seitdem ist sowoh... more Der Ansari X-Prize legte den Grundstein für den suborbitalen Weltraumtourismus. Seitdem ist sowohl das technische wie auch wirtschaftliche Interesse deutlich angestiegen. Es stellt sich daher die augenscheinliche Frage: Welche System-Architektur verfügt über die beste Kombination aus Sicherheit und wirtschaftlicher Rentabilität? Das Ziel dieser Arbeit ist es, diese Frage zu adressieren. Dazu wird der architektonische Design Space gründlich durchsucht und jede optimierte Architektur nach Kosten-und Sicherheitskriterien ausgewertet. Im Allgemeinen haben Systeme, die für eine spezifische Funktion gebaut werden, gerade in frühen Phasen einen großen architektonischen Design Space. Es werden zahlreiche Konzepte entwickelt, gebaut und getestet. Sobald sich das Produkt weiterentwickelt, stellen sich bestimmte Konzepte als überlegen heraus und die im Einsatz befindliche Vielfalt reduziert sich [1]. Als Beispiel beachte man die Mannigfaltigkeit von "Flugmaschinen" in den Jahrzehnten vor und nach den Wrights Brüdern. Ursprüngliche architektonische Entscheidungen wie Doppeldecker, Druckpropeller oder Entenflügel überdauern nicht zwingend als das dominierende Konzept [2]. Dieses Phänomen einer großen Vielfalt an verschiedenen Konzepten kann derzeit in der suborbitalen Raumfahrttouristenbranche beobachtet werden. Das spezifische Ziel dieser Arbeit ist es, den Design Space so komplett wie möglich zu untersuchen und die Architekturen zu identifizieren, die realisierbar und voraussichtlich erfolgreich sind. Hierbei werden die Grenzen des plausiblen Design Space bestimmt und die Entscheidungen identifiziert, die diesen Entwurfsraum definieren. Anschließend wird ein parametrisches Modell für alle möglichen Optionen erstellt und die Architekturen hinsichtlich der Zielfunktionen optimiert. Die nicht-dominierten Architekturen werden in der Sicherheitsund Kostendimension bewertet. Aus diesen wird eine geringe Anzahl an Entwürfen ausgewählt, die eine detaillierte Analyse rechtfertigen. Zuletzt wird eine Handlungsempfehlung ausgesprochen, wie der Entscheidungsprozess für eine Architektur strukturiert werden könnte.
Remote-controlled or autonomous multi-rotor air vehicles, or drones, have become common and comme... more Remote-controlled or autonomous multi-rotor air vehicles, or drones, have become common and commercially available even to individual consumers, mostly for imaging purposes. Drones appeal to mission architects looking to extend the toolbox provided to operators performing challenging missions such as public safety operations. However, careful analysis of the operational context and concept of operations must take place before major acquisitions. The purpose of this paper is to propose a model-based operational architecture definition framework, which is based on the Department of Defense Architecture Framework (DoDAF) ontology and uses Object Process Methodology (OPM) as its underlying modeling language. Through careful mapping of DoDAF Operational Viewpoint (OV) ontology to OPM ontology, we were able to show that the entire OV ontology can be covered by a small set of objects, processes, relations among them, and constructs comprising them. We then show how to instantiate the ontology to create a model of an actual architecture of interest (AoI) while maintaining strong typing of the model elements to ensure validity, integrity, consistency, and continuous compliance with the OV. We demonstrate our approach on the case of using drones in public safety enterprises for the purpose of crowd management in massively attended events and locations. The proposed framework allows for capturing ConOps and OpsCon in a lightweight, yet robust and consistent manner, and improve communication and concept validation between operational stakeholders and enterprise architects.
We introduce the Concept→Model→Graph→View Cycle (CMGVC). The CMGVC facilitates coherent architect... more We introduce the Concept→Model→Graph→View Cycle (CMGVC). The CMGVC facilitates coherent architecture analysis, reasoning, insight, and decision making based on conceptual models that are transformed into a generic, robust graph data structure (GDS). The GDS is then transformed into multiple views of the model, which inform stakeholders in various ways. This GDS-based approach decouples the view from the model and constitutes a powerful enhancement of model-based systems engineering (MBSE). The CMGVC applies the rigorous foundations of Category Theory, a mathematical framework of representations and transformations. We show that modeling languages are categories, drawing an analogy to programming languages. The CMGVC architecture is superior to direct transformations and language-coupled common representations. We demonstrate the CMGVC to transform a conceptual system architecture model built with the Object Process Modeling Language (OPM) into dual graphs and a stakeholder-informing...
As of the end of 2019, 46.4% of the world's population does not have regular access to the Intern... more As of the end of 2019, 46.4% of the world's population does not have regular access to the Internet. Bringing the more than 3.5 billion individuals still unconnected online is the primary goal for multiple international organizations, including the ITU and the UN Broadband Commission. Two important barriers that restrict connectivity are the lack of infrastructure and affordability. To address these barriers, several novel concepts that involve spaceborne and airborne platforms have been proposed to provide connectivity at a lower cost (improve affordability) to a wider reach of people (extend infrastructure). We develop a techno-economic methodology to assess the potential impact of space and aerial concepts in expanding connectivity to uncovered and under-served regions. In particular, constellations of geostationary orbit (GEO) satellites, large constellations of medium Earth orbit (MEO) and low Earth orbit (LEO) satellites, and high-and low-altitude aerial platforms are studied. Results show that under the current scenario, the impact of space and aerial systems in terms of expanding connectivity would be rather modest; the current cost of satellite technology (∼$200 per Mbps/month) are affordable for less than 1% of the uncovered and under-served population in the countries of interest. In a future scenario in 8-10 years, space systems have the highest potential to bring uncovered and under-served populations online, being a viable technology for 24% of the population in these countries.
The development of a concept for a system is a key step towards creating the system's architectur... more The development of a concept for a system is a key step towards creating the system's architecture. Most previous concept development approaches focus on the procedures for the conceptual design activity-the sequence of activities and tasks. Our work is motivated by the desire to move the activities executed in a Concurrent Design Facility more upstream, in order to include choices and trade-offs among potential system concepts in a digital environment. Therefore, the objective of this work is to develop a concept framework that can systematically represent the concept's constituents, their definitions and interconnections, such that it can be used in a computational environment. We propose a concept framework that is based on six assertions rooted in design theory, that lead to 33 entries in the framework. In order to test the completeness and utility of this framework, we have mapped eight selected US patents to the framework. Patents are a legally viable means for defending an invention, and therefore the patents must logically contain a description of the concept underlying the invention. For this small N study, we chose eight US patents that represent a broad spectrum of engineering systems and methods. The success of this mapping from patents to the proposed concept framework is a necessary condition to demonstrating the completeness and utility of the framework.
Architecting the ground segment of an optical space communication network The MIT Faculty has mad... more Architecting the ground segment of an optical space communication network The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation del Portillo, Inigo et al. "Architecting the Ground Segment of an
This paper presents a methodology to explore the architectural trade space of Earth observing sat... more This paper presents a methodology to explore the architectural trade space of Earth observing satellite systems, and applies it to the Earth Science Decadal Survey. The architecting problem is formulated as a combinatorial optimization problem with three sets of architectural decisions: instrument selection, assignment of instruments to satellites, and mission scheduling. A computational tool was created to automatically synthesize architectures based on valid combinations of options for these three decisions, and evaluate them according to several figures of merit including satisfaction of program requirements, data continuity, affordability, and proxies for fairness, technical and programmatic risk. A population-based heuristic search algorithm is used to search the trade space. The novelty of the tool is that it uses a rule-based expert system to model the knowledge-intensive components of the problem, such as scientific requirements, and to capture the non-linear positive and negative interactions between instruments (synergies and interferences), which drive both requirement satisfaction and cost. The tool is first demonstrated on the past NASA Earth Observing System program and then applied to the Decadal Survey. Results suggest that the Decadal Survey architecture is dominated by other more distributed architectures in which DESDYNI and CLARREO are consistently broken down into individual instruments.
In this paper, we present an integrated tool to support the high level design decisions concernin... more In this paper, we present an integrated tool to support the high level design decisions concerning the assignment of instruments to satellites in an Earth Observation Program. 12 This integrated tool features a rulebased expert system to model scientific synergies between measurements and engineering incompatibilities between instruments. We introduce two matrices: the science Design Structure Matrix (DSM) and the engineering DSM. Both matrices are calculated using the expert system, and provide insight into how to decompose the initial set of instruments into smaller tractable clusters. Then, each cluster of instruments is efficiently explored using metaheuristic algorithms (i.e. non-exact optimization algorithms that use heuristics to search the tradespace). We apply the methodology to the Earth Science Decadal Survey (DS) and identify a few architectures that are different from the baseline architecture and potentially better.
This paper introduces the notion of using formal language principles and technologies to study co... more This paper introduces the notion of using formal language principles and technologies to study complex systems. We applied a domain-neutral executable metalanguage , Object Process Network (OPN), to create a Moon-Mars Exploration Architecture Generator. The OPN-based architecture generator simulates the vehicles, phases, and vehicle interactions required to execute a human mission to the Moon or Mars. Using the simulation features of OPN, the generator enumerated hundreds of unique architectures, enabling an extensive analysis of possible configurations for the NASA Moon-Mars Exploration Vision. This paper provides an example of how a system can be methodically studied by representing it using a customized language. Using a custom language of Moon-Mars exploration as an example, we define a vocabulary, syntax, and semantics that represents mission modes. We next show how this language can be computationally evaluated using the executable metalanguage OPN, providing the system architect with a set of feasible architectures for further study. As a validation of the generator, we verified that well known Mars and Moon mission proposals were automatically generated. These proposals included (but were not limited to) Zubrin's Mars Direct, the 1993 NASA Mars Design Reference Mission, and all three architectures considered in Houbolt's 1961 Lunar Orbit Rendezvous Report.
A decision support tool is presented that is especially tailored for architecting Earth observing... more A decision support tool is presented that is especially tailored for architecting Earth observing missions and programs. The tool features both a cost model and a performance model. This paper focuses on the description of the performance model. Indeed, while considerable effort has been put into the development of cost estimating models, comparably much less effort has been put into the development of quantitative methods to assess how well Earth Observing Mission satisfy scientific and societal needs. A literature review revealed that existing methods include a commercial approach, a value-of-information approach, end-to-end simulation, assimilation in Observing System Simulation Experiments, and simple expert judgment. Limitations of these methods include limited applicability, computational complexity, low modeling fidelity (e.g. abstraction of synergies between measurements), and subjectivity. Our method uses a knowledge-based system to store and manage large quantities of expert knowledge in the form of rules-of-thumb that replace expensive computations. Scientific and societal measurement requirements and instrument capabilities are expressed in the form of logical rules and data structures. An efficient pattern matching algorithm performs the comparison of the measurement requirements and the measurement capabilities on the basis of 64 different measurement attributes. The system is demonstrated on the Earth Science Decadal Survey. While the system is still under development, it shows great potential to enhance traceability in the modeling of scientific and societal value of Earth observing missions. Furthermore, the recursive nature of rule-based systems shows potential to model synergies between instruments and measurements, at a sufficient level of fidelity for architectural trade studies, especially for the ones conducted in committees with experts such as Decadal Surveys.
AIAA Guidance, Navigation and Control Conference and Exhibit, 2007
This paper compares various architectural philosophies used in the design of GN&C systems for NAS... more This paper compares various architectural philosophies used in the design of GN&C systems for NASA human-rated and robotic spacecraft during the last four decades. This comparison gives insight into the options available for the GN&C systems of the new generation of space vehicles to be developed under NASA's Constellation Program (CxP). This study focuses on the component interconnectivity features behind cross-strapping and channelization, the two main architecting approaches for designing fault-tolerant GN&C systems. The features of theses two approaches, as well as hybrid versions of these approaches, are explained. The paper also discusses their advantages and disadvantages in terms of complexity, reliability, and fault-tolerance. Several systems developed by NASA for human-rated systems and robotic systems are analyzed and compared from this perspective. The final goal of this paper is to lay the foundations for a more in-depth study to assess commonality among different GN&C architectures for the CxP.
The field of computational synthesis is emerging is an inter- disciplinary effort that encompasse... more The field of computational synthesis is emerging is an inter- disciplinary effort that encompasses applications in a variety of knowledge domains. Each domain has its own ontology, modeling methods, set of symbols, and syntax. The cross- cutting commonalities among the various implementation domains, which make computational synthesis a research do- main in its own right, are articulated for the most
1st Space Exploration Conference: Continuing the Voyage of Discovery, 2005
The sustainability of space exploration will depend in large part on its ability to consistently ... more The sustainability of space exploration will depend in large part on its ability to consistently and reliably deliver valued benefits to societal stakeholders over an extended period. This ongoing research studies the values of prospective stakeholders in the space exploration enterprise-both in the near term and with a perspective extending over decades. The immediate focus is human and robotic exploration of the Earth/Moon system, but extends to the exploration of Mars as well. Potential beneficiaries of space exploration are identified in broad societal sectors. An analysis of these stakeholders, their values and needs leads to the development of a comprehensive set of space exploration objectives that address those needs. The relative priority of exploration objectives is weighted using information about stakeholder characteristics, values, and their role and place in the exploration value stream. The weighted exploration objectives can then be used to assess the relative value of different technical system architectures, and to design exploration enterprise architecture, attributes and policy frameworks to enable value delivery to societal stakeholders. Ultimately, through stakeholders' continuing support, sustainable space exploration will be delivered.
International Journal of Satellite Communications and Networking
The rise of the commercial space industry has resulted in the development of megaconstellations t... more The rise of the commercial space industry has resulted in the development of megaconstellations that promise to provide global broadband. These constellations capitalize on advancements in technology, improved modeling capabilities, and reductions in launch cost. One of the significant open questions is whether these constellations will significantly increase access for uncovered and underserved communities, in addition to serving existing markets. This paper analyzes which constellation characteristics provide the best global coverage at the lowest operational cost. First, we present the demand model that assesses the number of under-served and uncovered users in a given region. Then, we present a genetic algorithm used to identify potential constellations. Finally, we conclude by identifying which characteristics are the most promising for broadband constellations, as well as predictions of how the market will develop in the coming years. Our analysis has found that geostationary (GEO) and medium Earth orbit (MEO) satellite constellations have the highest likelihood of profitability. LEO networks are on average 27% more expensive, but if designed wisely, they can be competitive. Our work shows that there are diminishing returns with large constellations, and that it is more cost effective to have a small number of highly capable satellites, rather than many low complexity satellites. Key technologies like high frequency bands and miniaturization of components can lead to further cost reductions and increase the competitiveness of LEO constellations.
This paper introduces a method for Model-based Ontology Coverage Analysis (MOCA) and applies it t... more This paper introduces a method for Model-based Ontology Coverage Analysis (MOCA) and applies it to SysML models of mission architectures. An ontology is a set of concepts that constitute a common language, standard terminology, and consistent pattern reference across multiple models within an organization, industry, or domain. The purpose of MOCA is to assess the overlap between a system architecture model and a given ontology, and thereby the architecture model's compliance with the ontology and the ontology's utilization by the architecture. We demonstrate MOCA on a SysML model of a humanitarian airlift mission, using a conceptual mission architecting SysML profile model that serves as the ontology. MOCA automates and simplifies reasoning over models, and creates digital model-based artifacts that support stakeholders in concept validation, decision making, and system/mission design. Thus, MOCA enhances digital systems engineering.
A renewed interest in lunar exploration with the focus on establishing a constant human presence ... more A renewed interest in lunar exploration with the focus on establishing a constant human presence on the Moon calls for developing new lunar human landing systems (HLS) which would deliver the crew from the prospective Lunar Gateway station to the surface of the Moon and back. Over the years, different human lunar lander architectures were proposed and multiple architecture studies were performed. However, those studies are relevant to the specific assumptions and lunar architectures proposed at the time of conducting the study. Since the current vision for lunar exploration includes new features, such as having the Lunar Gateway and switching to reusable systems, there is a need for a new HLS architecture study. Such studies are being performed by private companies; however, those are rarely publicly available. The goal of this paper is to address this gap and provide a publicly available architectural analysis within the current views on the future human lunar exploration. We assume the Lunar Gateway in an L2 near rectilinear halo orbit and a landing site at the lunar South Pole; the number of HLS crew of 4; the surface stay time of ~ 7 days, the payload mass delivered to the surface of 500 kg, and the payload mass returned from the surface of 250 kg. A set of parametric models including an HLS model and an HLS program cost model is developed for the analysis. 39 architectures with varying number of stages (1, 2, and 3 stages) and propellant combinations (LOX/LH2, LOX/CH4, and MMH/NTO) are explored. The Pareto analysis shows that there is a difference between typical performance trends for expendable and reusable architectures. For expendable architectures, the 2-stage option seems to be the most advantageous while, for reusable architectures, the 1-and 3-stage options are either comparable or win over the 2-stage option even for the number of system uses as low as 3. In terms of the propellant combinations, pure LOX/LH2 or combined LOX/LH2/LOX/CH4 architectures dominate the tradespace. Assuming that the inter-stage propellant compatibility is a preferred option for systems refueling from the Gateway, 1-stage and 3-stage all LOX/LH2 architectures are identified as the likeliest candidates to have lowest HLS-related production and launch costs. Further cost analysis of those two architectures shows that the 1-stage HLS wins over the 3-stage system in terms of the overall HLS program cost if a long-term exploration program (on the order of tens of missions) is assumed.
The digital transformation era is upon us. Digital transformation gradually crawls up the value c... more The digital transformation era is upon us. Digital transformation gradually crawls up the value chain from services and manufacturing to product design and systems engineering. In this paper we envision a cloud-based ecosystem of systems engineering, which is model-based by definition. The ecosystem model we propose is called 2MIDSTARs, which stands for: Model, Infrastructure, Data Services, Simulation, Testing, Analysis, and Repositories + Management, Interoperability, Digital Representation, System, Technology, Audit, and Reporting. The first MIDSTAR covers the intrinsic, core MBSE capabilities, while the second MIDSTAR facilitates the integration with the digital enterprise that surrounds the digital systems engineering ecosystem. In this paper we explain the importance of jointly considering all these elements together and outline the key roles and functionalities of each component.
A Digital Engineering Information Exchange supports an exchange of digital artifacts between syst... more A Digital Engineering Information Exchange supports an exchange of digital artifacts between system engineering entities (INCOSE). Such entities might include processes, models, and organizational elements associated with space missions design. Reducing complexity and errors, as well as improving efficiency are critical capabilities associated with a digital transformation of space missions design and delivery. In our work we propose an approach to manage a digital engineering information exchange through the DSM-based approach (Eppinger and Browning 2012). Applied to space systems architecture, the method allows keeping track of the information exchange throughout the product development. Such information includes the core entities and relationships of CubeSat’s subsystems. This would integrate systems engineering (MBSE) approaches and PLM methods. In our paper we apply the proposed approach to a CubeSat mission design. One of the forms of utility of the proposed approach is the ab...
Projects of the New Space economy such as SpaceShipTwo and New Shepard are on their way to shifti... more Projects of the New Space economy such as SpaceShipTwo and New Shepard are on their way to shifting the paradigms in space tourism and transportation. Being privately financed, they are also changing the way in which highly complex and formerly government-financed systems are now being developed. Looking to the future, we can envision humanity moving to space, an opportunity that will be available to many more of us as a result of these new paradigms. One of the core issues we encounter when we start the development of complex systems such as the suborbital transportation and space tourism systems is: what are the concepts available and how can these concepts be represented using strictly defined ontology and model semantics? In this work we present a model-based concept framework that aims to address this issue. First a concept framework methodology is presented, after which we demonstrate its applicability to suborbital human spaceflight missions – SpaceShipTwo and New Shepard. Th...
Der Ansari X-Prize legte den Grundstein für den suborbitalen Weltraumtourismus. Seitdem ist sowoh... more Der Ansari X-Prize legte den Grundstein für den suborbitalen Weltraumtourismus. Seitdem ist sowohl das technische wie auch wirtschaftliche Interesse deutlich angestiegen. Es stellt sich daher die augenscheinliche Frage: Welche System-Architektur verfügt über die beste Kombination aus Sicherheit und wirtschaftlicher Rentabilität? Das Ziel dieser Arbeit ist es, diese Frage zu adressieren. Dazu wird der architektonische Design Space gründlich durchsucht und jede optimierte Architektur nach Kosten-und Sicherheitskriterien ausgewertet. Im Allgemeinen haben Systeme, die für eine spezifische Funktion gebaut werden, gerade in frühen Phasen einen großen architektonischen Design Space. Es werden zahlreiche Konzepte entwickelt, gebaut und getestet. Sobald sich das Produkt weiterentwickelt, stellen sich bestimmte Konzepte als überlegen heraus und die im Einsatz befindliche Vielfalt reduziert sich [1]. Als Beispiel beachte man die Mannigfaltigkeit von "Flugmaschinen" in den Jahrzehnten vor und nach den Wrights Brüdern. Ursprüngliche architektonische Entscheidungen wie Doppeldecker, Druckpropeller oder Entenflügel überdauern nicht zwingend als das dominierende Konzept [2]. Dieses Phänomen einer großen Vielfalt an verschiedenen Konzepten kann derzeit in der suborbitalen Raumfahrttouristenbranche beobachtet werden. Das spezifische Ziel dieser Arbeit ist es, den Design Space so komplett wie möglich zu untersuchen und die Architekturen zu identifizieren, die realisierbar und voraussichtlich erfolgreich sind. Hierbei werden die Grenzen des plausiblen Design Space bestimmt und die Entscheidungen identifiziert, die diesen Entwurfsraum definieren. Anschließend wird ein parametrisches Modell für alle möglichen Optionen erstellt und die Architekturen hinsichtlich der Zielfunktionen optimiert. Die nicht-dominierten Architekturen werden in der Sicherheitsund Kostendimension bewertet. Aus diesen wird eine geringe Anzahl an Entwürfen ausgewählt, die eine detaillierte Analyse rechtfertigen. Zuletzt wird eine Handlungsempfehlung ausgesprochen, wie der Entscheidungsprozess für eine Architektur strukturiert werden könnte.
Remote-controlled or autonomous multi-rotor air vehicles, or drones, have become common and comme... more Remote-controlled or autonomous multi-rotor air vehicles, or drones, have become common and commercially available even to individual consumers, mostly for imaging purposes. Drones appeal to mission architects looking to extend the toolbox provided to operators performing challenging missions such as public safety operations. However, careful analysis of the operational context and concept of operations must take place before major acquisitions. The purpose of this paper is to propose a model-based operational architecture definition framework, which is based on the Department of Defense Architecture Framework (DoDAF) ontology and uses Object Process Methodology (OPM) as its underlying modeling language. Through careful mapping of DoDAF Operational Viewpoint (OV) ontology to OPM ontology, we were able to show that the entire OV ontology can be covered by a small set of objects, processes, relations among them, and constructs comprising them. We then show how to instantiate the ontology to create a model of an actual architecture of interest (AoI) while maintaining strong typing of the model elements to ensure validity, integrity, consistency, and continuous compliance with the OV. We demonstrate our approach on the case of using drones in public safety enterprises for the purpose of crowd management in massively attended events and locations. The proposed framework allows for capturing ConOps and OpsCon in a lightweight, yet robust and consistent manner, and improve communication and concept validation between operational stakeholders and enterprise architects.
We introduce the Concept→Model→Graph→View Cycle (CMGVC). The CMGVC facilitates coherent architect... more We introduce the Concept→Model→Graph→View Cycle (CMGVC). The CMGVC facilitates coherent architecture analysis, reasoning, insight, and decision making based on conceptual models that are transformed into a generic, robust graph data structure (GDS). The GDS is then transformed into multiple views of the model, which inform stakeholders in various ways. This GDS-based approach decouples the view from the model and constitutes a powerful enhancement of model-based systems engineering (MBSE). The CMGVC applies the rigorous foundations of Category Theory, a mathematical framework of representations and transformations. We show that modeling languages are categories, drawing an analogy to programming languages. The CMGVC architecture is superior to direct transformations and language-coupled common representations. We demonstrate the CMGVC to transform a conceptual system architecture model built with the Object Process Modeling Language (OPM) into dual graphs and a stakeholder-informing...
As of the end of 2019, 46.4% of the world's population does not have regular access to the Intern... more As of the end of 2019, 46.4% of the world's population does not have regular access to the Internet. Bringing the more than 3.5 billion individuals still unconnected online is the primary goal for multiple international organizations, including the ITU and the UN Broadband Commission. Two important barriers that restrict connectivity are the lack of infrastructure and affordability. To address these barriers, several novel concepts that involve spaceborne and airborne platforms have been proposed to provide connectivity at a lower cost (improve affordability) to a wider reach of people (extend infrastructure). We develop a techno-economic methodology to assess the potential impact of space and aerial concepts in expanding connectivity to uncovered and under-served regions. In particular, constellations of geostationary orbit (GEO) satellites, large constellations of medium Earth orbit (MEO) and low Earth orbit (LEO) satellites, and high-and low-altitude aerial platforms are studied. Results show that under the current scenario, the impact of space and aerial systems in terms of expanding connectivity would be rather modest; the current cost of satellite technology (∼$200 per Mbps/month) are affordable for less than 1% of the uncovered and under-served population in the countries of interest. In a future scenario in 8-10 years, space systems have the highest potential to bring uncovered and under-served populations online, being a viable technology for 24% of the population in these countries.
The development of a concept for a system is a key step towards creating the system's architectur... more The development of a concept for a system is a key step towards creating the system's architecture. Most previous concept development approaches focus on the procedures for the conceptual design activity-the sequence of activities and tasks. Our work is motivated by the desire to move the activities executed in a Concurrent Design Facility more upstream, in order to include choices and trade-offs among potential system concepts in a digital environment. Therefore, the objective of this work is to develop a concept framework that can systematically represent the concept's constituents, their definitions and interconnections, such that it can be used in a computational environment. We propose a concept framework that is based on six assertions rooted in design theory, that lead to 33 entries in the framework. In order to test the completeness and utility of this framework, we have mapped eight selected US patents to the framework. Patents are a legally viable means for defending an invention, and therefore the patents must logically contain a description of the concept underlying the invention. For this small N study, we chose eight US patents that represent a broad spectrum of engineering systems and methods. The success of this mapping from patents to the proposed concept framework is a necessary condition to demonstrating the completeness and utility of the framework.
Architecting the ground segment of an optical space communication network The MIT Faculty has mad... more Architecting the ground segment of an optical space communication network The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation del Portillo, Inigo et al. "Architecting the Ground Segment of an
This paper presents a methodology to explore the architectural trade space of Earth observing sat... more This paper presents a methodology to explore the architectural trade space of Earth observing satellite systems, and applies it to the Earth Science Decadal Survey. The architecting problem is formulated as a combinatorial optimization problem with three sets of architectural decisions: instrument selection, assignment of instruments to satellites, and mission scheduling. A computational tool was created to automatically synthesize architectures based on valid combinations of options for these three decisions, and evaluate them according to several figures of merit including satisfaction of program requirements, data continuity, affordability, and proxies for fairness, technical and programmatic risk. A population-based heuristic search algorithm is used to search the trade space. The novelty of the tool is that it uses a rule-based expert system to model the knowledge-intensive components of the problem, such as scientific requirements, and to capture the non-linear positive and negative interactions between instruments (synergies and interferences), which drive both requirement satisfaction and cost. The tool is first demonstrated on the past NASA Earth Observing System program and then applied to the Decadal Survey. Results suggest that the Decadal Survey architecture is dominated by other more distributed architectures in which DESDYNI and CLARREO are consistently broken down into individual instruments.
In this paper, we present an integrated tool to support the high level design decisions concernin... more In this paper, we present an integrated tool to support the high level design decisions concerning the assignment of instruments to satellites in an Earth Observation Program. 12 This integrated tool features a rulebased expert system to model scientific synergies between measurements and engineering incompatibilities between instruments. We introduce two matrices: the science Design Structure Matrix (DSM) and the engineering DSM. Both matrices are calculated using the expert system, and provide insight into how to decompose the initial set of instruments into smaller tractable clusters. Then, each cluster of instruments is efficiently explored using metaheuristic algorithms (i.e. non-exact optimization algorithms that use heuristics to search the tradespace). We apply the methodology to the Earth Science Decadal Survey (DS) and identify a few architectures that are different from the baseline architecture and potentially better.
This paper introduces the notion of using formal language principles and technologies to study co... more This paper introduces the notion of using formal language principles and technologies to study complex systems. We applied a domain-neutral executable metalanguage , Object Process Network (OPN), to create a Moon-Mars Exploration Architecture Generator. The OPN-based architecture generator simulates the vehicles, phases, and vehicle interactions required to execute a human mission to the Moon or Mars. Using the simulation features of OPN, the generator enumerated hundreds of unique architectures, enabling an extensive analysis of possible configurations for the NASA Moon-Mars Exploration Vision. This paper provides an example of how a system can be methodically studied by representing it using a customized language. Using a custom language of Moon-Mars exploration as an example, we define a vocabulary, syntax, and semantics that represents mission modes. We next show how this language can be computationally evaluated using the executable metalanguage OPN, providing the system architect with a set of feasible architectures for further study. As a validation of the generator, we verified that well known Mars and Moon mission proposals were automatically generated. These proposals included (but were not limited to) Zubrin's Mars Direct, the 1993 NASA Mars Design Reference Mission, and all three architectures considered in Houbolt's 1961 Lunar Orbit Rendezvous Report.
A decision support tool is presented that is especially tailored for architecting Earth observing... more A decision support tool is presented that is especially tailored for architecting Earth observing missions and programs. The tool features both a cost model and a performance model. This paper focuses on the description of the performance model. Indeed, while considerable effort has been put into the development of cost estimating models, comparably much less effort has been put into the development of quantitative methods to assess how well Earth Observing Mission satisfy scientific and societal needs. A literature review revealed that existing methods include a commercial approach, a value-of-information approach, end-to-end simulation, assimilation in Observing System Simulation Experiments, and simple expert judgment. Limitations of these methods include limited applicability, computational complexity, low modeling fidelity (e.g. abstraction of synergies between measurements), and subjectivity. Our method uses a knowledge-based system to store and manage large quantities of expert knowledge in the form of rules-of-thumb that replace expensive computations. Scientific and societal measurement requirements and instrument capabilities are expressed in the form of logical rules and data structures. An efficient pattern matching algorithm performs the comparison of the measurement requirements and the measurement capabilities on the basis of 64 different measurement attributes. The system is demonstrated on the Earth Science Decadal Survey. While the system is still under development, it shows great potential to enhance traceability in the modeling of scientific and societal value of Earth observing missions. Furthermore, the recursive nature of rule-based systems shows potential to model synergies between instruments and measurements, at a sufficient level of fidelity for architectural trade studies, especially for the ones conducted in committees with experts such as Decadal Surveys.
AIAA Guidance, Navigation and Control Conference and Exhibit, 2007
This paper compares various architectural philosophies used in the design of GN&C systems for NAS... more This paper compares various architectural philosophies used in the design of GN&C systems for NASA human-rated and robotic spacecraft during the last four decades. This comparison gives insight into the options available for the GN&C systems of the new generation of space vehicles to be developed under NASA's Constellation Program (CxP). This study focuses on the component interconnectivity features behind cross-strapping and channelization, the two main architecting approaches for designing fault-tolerant GN&C systems. The features of theses two approaches, as well as hybrid versions of these approaches, are explained. The paper also discusses their advantages and disadvantages in terms of complexity, reliability, and fault-tolerance. Several systems developed by NASA for human-rated systems and robotic systems are analyzed and compared from this perspective. The final goal of this paper is to lay the foundations for a more in-depth study to assess commonality among different GN&C architectures for the CxP.
The field of computational synthesis is emerging is an inter- disciplinary effort that encompasse... more The field of computational synthesis is emerging is an inter- disciplinary effort that encompasses applications in a variety of knowledge domains. Each domain has its own ontology, modeling methods, set of symbols, and syntax. The cross- cutting commonalities among the various implementation domains, which make computational synthesis a research do- main in its own right, are articulated for the most
1st Space Exploration Conference: Continuing the Voyage of Discovery, 2005
The sustainability of space exploration will depend in large part on its ability to consistently ... more The sustainability of space exploration will depend in large part on its ability to consistently and reliably deliver valued benefits to societal stakeholders over an extended period. This ongoing research studies the values of prospective stakeholders in the space exploration enterprise-both in the near term and with a perspective extending over decades. The immediate focus is human and robotic exploration of the Earth/Moon system, but extends to the exploration of Mars as well. Potential beneficiaries of space exploration are identified in broad societal sectors. An analysis of these stakeholders, their values and needs leads to the development of a comprehensive set of space exploration objectives that address those needs. The relative priority of exploration objectives is weighted using information about stakeholder characteristics, values, and their role and place in the exploration value stream. The weighted exploration objectives can then be used to assess the relative value of different technical system architectures, and to design exploration enterprise architecture, attributes and policy frameworks to enable value delivery to societal stakeholders. Ultimately, through stakeholders' continuing support, sustainable space exploration will be delivered.
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Papers by Edward Crawley