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Hardware developers started experimenting with Scrum to accelerate their product development. However, it is not possible to implement Scrum in the same way as it was done for software systems, where the approach is already well established. One of the processes required in Scrum is the estimate of task efforts when creating a backlog for an Agile Sprint. This article presents a pilot validation experiment of a novel Agile framework for the development of hardware systems, including a parametric tool to estimate task effort in a more rigorous way than traditional confidence votes. This article presents the validation of electronic hardware design task estimation and overall project performance. The validation is performed through experimental work with teams of junior engineering students. The validation experiment showed an improvement from a minimum of eight to a maximum of eighteen percent when employing the presented tool during planning phases of the development.

As small satellites are finding increased applicability in a number of space missions, the community is actively exploring the feasibility of missions employing active instruments on small spacecraft. In particular, synthetic aperture radars are of interest as they prove to be versatile tools for Earth Observation purposes. This paper proposes a trade space exploration model to identify designs for space-borne satellite synthetic aperture radars that address the desired instrument requirements. Two trade space analysis approaches are proposed, based on a multivariate analysis with two evaluation metrics and using parallel coordinate plots. The paper demonstrates the utility of the trade space model by considering two case studies. The first study looks at radar instruments on a broad range of small satellite platforms. This study narrows down a trade space of 1265 feasible radar designs to less than 44 Pareto optimal designs at different center frequencies (C- and X-band), elicits conditions for L-band SARs feasibility, and discusses the feasibility bounds and technical constraints on associated instrument and spacecraft requirements. The second study considers radars for 3U CubeSat platforms. The study identifies 44 Pareto optimal designs within 12,928 feasible designs and sheds light on the operational constraints required for the development of such innovative miniaturized radars.

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.

A substantial body of literature on global design optimization techniques is based on an implicit assumption that a system under optimization is designed by a perfectly centralized design team with all team members committed to a global optimum solution. This assumption enables the system engineers to minimize all the objective functions simultaneously while controlling all design decisions at the same time. Recent research suggested that this inherent assumption may need to be revisited. This paper proposes a novel framework for design optimization using game theory, which represents a design process as a normal-form game and unifies two fundamental decisions of discipline designers, namely a system-global or a discipline-local optimum solution. This paper provides a general mathematical formulation of the framework for a design process with any number of discipline designers. The framework introduces the notion of the Nash front, which is a set of design solutions consisting of the Nash equilibria derived through the reallocation of design authority between discipline designers. This paper then tests the framework on a numerical optimization case study of a Stirling micro combined heat and power plant with two discipline designers. The result indicates that for the system capital cost and the system power output the difference between global Pareto-optimum designs and the Nash front designs on average across five different scenarios of design authority allocation was 22% and 16%, correspondingly. The application of the novel framework in different fields of engineering could help to build models that are more realistic and prevent impractical technical objectives.

This paper proposes the concept of experiential systems engineering (ESE) as a hands-on education approach for teaching systems engineering (SE) tools and methods in postgraduate university courses, following the conceive, design, implement, and operate (CDIO) approach to modern engineering education. It describes ESE as implemented by the author and his research team in the Space Systems Engineering courses at Skoltech over the course of Fall 2014–Spring 2017. It describes the experience of student cohorts in applying SE to stratospheric balloon missions for education purposes, simulating real-life project experience including customer interface management, and operating projects designing and implementing an SE management plan. It describes the proposed approach and provides lessons learnt to generalize ESE to any specific engineering discipline of interest. A mapping between the learning objectives of ESE and the CDIO education framework is proposed. It extends the concept of hands-on SE education. It will be useful to educators interested in novel approaches to SE education and to experiment new ways to deliver a subject that is traditionally believed difficult to teach in university.

This paper defines Federations of Systems, introduces a tailored architecting framework, and demonstrates it in a satellite design case study. While certainly not being new concepts in the literature, federations are a class of Systems of Systems (SoS) that have not been extensively explored due to the scarcity of applied examples and still few practitioners facing their specific design challenges. This is expected to change with the advent of the Internet of Things, Machine to Machine applications, collaborative consumption, and Federated Satellite Systems. It has become henceforth necessary to develop approaches in design and architecting capable of addressing such interconnected sets of systems. Federations are SoS characterized by the absence of global goals and stakeholders, and cooperation enabled only on an opportunistic basis. Systems engage in federations when the perceived benefit exceeds the costs of the necessary interfaces. The proposed framework quantifies the upper limits to the net benefits of cooperation between systems through the concept of synergy. Using synergy as a heuristic to navigate federated design spaces, the framework predicts the appearance and evolution of federations. The demonstration of the framework in a six‐satellite federation shows that advantages of federating emerge with the collaboration between just two systems. Interface costs, architectural cost preferences, and network topology drive the achievable benefits. Specifically, when considering communication architectures under 80 MUSD for satellite systems, federating is advantageous when the interface lifecycle costs are below 15 MUSD. This demonstration case exemplifies how federating can assist systems in achieving design points that dominate the solutions of their local tradespace.

This work addresses a critical topic in federated satellites development: the lack of trust between stakeholders that would prevent any stakeholder joining a satellite federation owned and operated by multiple parties. A characterisation of security needs for federated satellite systems is proposed, showing that in order for a federation to offer an environment for a beneficial cooperation, a notion of identity, both user identity and data authentication, has to be introduced, and stakeholders' security requirements have to be satisfied. This paper presents a public key infrastructure (PKI) based protocol for addressing stakeholders' security requirements and ensuring data authentication, integrity and confidentiality in data transfer operations within satellite federations. The performance and cost overheads of the proposed security protocol are first characterised with an experimental implementation on a Raspberry Pi 2 platform, used as a representative proxy testbed of commercial off-the-shelf avionics for small satellites, and then with a benchmark on a range of CPUs to analyse which platforms achieve set performance goals with radio-based and laser-based communications. Recommendations for implementing security mechanisms in federated satellite systems are thus derived.

This paper develops a framework to simulate and evaluate pricing policies of spacecraft trading commodities, such as data routing, in a federated satellite network. Federated satellite systems allow the reallocation of underutilized assets, enabling their use as services between owners and third parties. The paper, by means of game theory, focuses on sealed-bid reverse auction pricing schemes, benchmarks first-price and second-price auction strategies, and evaluates the associated trade-offs in terms of performance and cost, and losses in Pareto efficiency introduced by system-level operation constraints. The analysis considers an application case study for federated satellite systems operating in Low Earth Orbit for commercial purposes. Satellite federations are a novel paradigm envisioning on-orbit opportunistic sharing of resources through an ad hoc mobile satellite network. The architecture creates the basis for the realization of a commercial cloud computing environment in orbit, with spacecraft establishing communications links between each other leveraging on system design margins. The results of the case study in space provide new insights on the design of federated satellites and their operations while characterizing emergent behaviors and efficient trade-offs on the Pareto front of the cost–performance curve.

This paper proposes a novel model-based approach to technology planning and roadmapping, consisting of two complementary steps: technology forecasting and game-theoretic planning. The inherent uncertainty of target technology performances, timelines and risks impact the roadmapping process. Reducing this uncertainty is a major challenge and allows elaborating different options and scenarios. A formal methodology is proposed for quantitative forecasting in a multi-dimensional space (different performance metrics and time) based on past technology development trend information. The method adopts concepts and approaches from econometrics and is formulated as a convex optimization problem with different constraints on the frontier's shape. It provides useful product line assessment benchmarks and helps to set reasonable goals for future technology developments. Game-theoretic planning allows addressing the strategic decisions to take, considering the technology landscape, markets, and competition. The strategic decisions affect in turn other companies as well, which is the basis for the application of game theory, in the form of best-response functions to determine the subsequent reactions and movements of rivals in a technological landscape. The result is a simulation of a sequential game in technology space, allowing evaluating possible technological development pathways and determining optimal models on the Pareto frontiers, potential targets for technology roadmapping.

Traditionally, the space industry produced large and sophisticated spacecraft handcrafted by large teams of engineers and budgets within the reach of only a few large government-backed institutions. However, over the last decade, the space industry experienced an increased interest towards smaller missions and recent advances in commercial-off-the-shelf (COTS) technology miniaturization spurred the development of small spacecraft missions based on the CubeSat standard. CubeSats were initially envisioned primarily as educational tools or low cost technology demonstration platforms that could be developed and launched within one or two years. Recently, however, more advanced CubeSat missions have been developed and proposed, indicating that CubeSats clearly started to transition from being solely educational and technology demonstration platforms to offer opportunities for low-cost real science missions with potential high value in terms of science return and commercial revenue. Despite the significant progress made in CubeSat research and development over the last decade, some fundamental questions still habitually arise about the CubeSat capabilities, limitations, and ultimately about their scientific and commercial value. The main objective of this review is to evaluate the state of the art CubeSat capabilities with a special focus on advanced scientific missions and a goal of assessing the potential of CubeSat platforms as capable spacecraft. A total of over 1200 launched and proposed missions have been analyzed from various sources including peer-reviewed journal publications, conference proceedings, mission webpages as well as other publicly available satellite databases and about 130 relatively high performance missions were downselected and categorized into six groups based on the primary mission objectives including “Earth Science and Spaceborne Applications”, “Deep Space Exploration”, “Heliophysics: Space Weather”, “Astrophysics”, “Spaceborne In Situ Laboratory”, and “Technology Demonstration” for in-detail analysis. Additionally, the evolution of CubeSat enabling technologies are surveyed for evaluating the current technology state of the art as well as identifying potential areas that will benefit the most from further technology developments for enabling high performance science missions based on CubeSat platforms.

Novel space mission concepts such as Federated Satellite Systems promise to enhance sustainability, robustness, and reliability of current missions by means of in-orbit sharing of space assets. This new paradigm requires the utilization of several technologies in order to confer flexibility and re-configurability to communications systems among heterogeneous spacecrafts. This paper illustrates the results of the experimental demonstration of the value proposition of federated satellites through two stratospheric balloons interoperating with a tracking ground station through Commercial Off-The-Shelf Software Defined Radios (SDRs). The paper reports telemetry analysis and characterizes the communications network that was realized in-flight. Furthermore, it provides details on an in-flight anomaly experienced by one of the balloons, which was recovered through the use of the federated technology that has been developed. The anomaly experienced led to the early loss of the directional link from the ground station to the affected stratospheric balloon node after 15 min in flight. Nevertheless, thanks to the federated approach among the systems, the ground station was still able to retrieve the balloon׳s data in real time through the network system, for which the other balloon operated as a federated relay for 45 min in flight, uninterrupted. In other words, the federated approach to the system allowed triplicating the useful lifetime of the defective system, which would have not been possible to realize otherwise. Such anomaly coincidentally demonstrated the value of the federated approach to space systems design. The paper paves the way for future tests on space assets.

This paper analyzes the design implications for space missions participating in opportunistic satellite federations. Satellite federations are a novel instance of distributed satellite systems implementing the concept of opportunistic collaboration in space among heterogeneous missions; trading resources, such as data relay; storage; and computing power among participant missions. The ability of a spacecraft to join a federation is mainly constrained by bus power availability and spacecraft attitude. The paper quantifies design implications for missions to participate in satellite federations. In particular, the paper quantifies the overall spacecraft mass impacts associated with operations on margins within a federation. A systems-level spacecraft model is developed to show that overall system mass impacts for typical-use low-Earth-orbit spacecraft participating in a satellite federation are 12, 1.1, and 0.6% for small-, medium-, and large-class platforms, respectively. It is shown that up to 500 s−1 pe...

This paper defines the paradigm of Federated Satellite Systems (FSS) as a novel distributed space systems architecture. FSS are networks of spacecraft trading previously inefficiently allocated and unused resources such as downlink bandwidth, storage, processing power, and instrument time. FSS holds the promise to enhance cost-effectiveness, performance and reliability of existing and future space missions, by networking different missions and effectively creating a pool of resources to exchange between participants in the federation. This paper introduces and describes the FSS paradigm, and develops an approach integrating mission analysis and economic assessments to evaluate the feasibility of the business case of FSS. The approach is demonstrated on a case study on opportunities enabled by FSS to enhance space exploration programs, with particular reference to the International Space Station. The application of the proposed methodology shows that the FSS concept is potentially able to create large commercial markets of in-space resources, by providing the technical platform to offer the opportunity for spacecraft to share or make use of unused resources within their orbital neighborhood. It is shown how the concept is beneficial to satellite operators, space agencies, and other stakeholders of the space industry to more flexibly interoperate space systems as a portfolio of assets, allowing unprecedented collaboration among heterogeneous types of missions.

As small satellites and Sun Synchronous Earth Observation systems are assuming an increased role in nowadays space activities, including commercial investments, it is of interest to assess how infrastructures could be developed to support the development of such systems and other spacecraft that could benefit from having a data relay service in Low Earth Orbit (LEO), as opposed to traditional Geostationary relays. This paper presents a tradespace exploration study of the architecture of such LEO commercial satellite data relay systems, here defined as Earth Orbiting Support Systems (EOSS). The paper proposes a methodology to formulate architectural decisions for EOSS constellations, and enumerate the corresponding tradespace of feasible architectures. Evaluation metrics are proposed to measure benefits and costs of architectures; lastly, a multicriteria Pareto criterion is used to downselect optimal architectures for subsequent analysis. The methodology is applied to two case studies for a set of 30 and 100 customer-spacecraft respectively, representing potential markets for LEO services in Exploration, Earth Observation, Science, and CubeSats. Pareto analysis shows how increased performance of the constellation is always achieved by an increased node size, as measured by the gain of the communications antenna mounted on EOSS spacecraft. On the other hand, nonlinear trends in optimal orbital altitude, number of satellites per plane, and number of orbital planes, are found in both cases. An upward trend in individual node memory capacity is found, although never exceeding 256 Gbits of onboard memory for both cases that have been considered, assuming the availability of a polar ground station for EOSS data downlink. System architects can use the proposed methodology to identify optimal EOSS constellations for a given service pricing strategy and customer target, thus identifying alternatives for selection by decision makers.

The purpose of this work is to propose a tradespace exploration framework for the design and system analysis of Stirling engines. The framework can be used to execute trade studies for different objectives. The framework obtains Pareto frontiers of optimal designs by evaluating performance (power, efficiency) and cost metrics for 750 Stirling engine design alternatives. The proposed system design framework integrates four domain models. An engine cycle thermodynamic model is to calculate engine cycle and performance parameters. A heat exchanger model is to estimate areas of heat exchangers. An economic model to predict the capital cost of the engine system. And a tradespace model based on five design parameters identified as drivers of the design: Stirling engine type (alpha, beta, or gamma), engine bore, stroke, hot space temperature, and cold space temperature. The results of the model shed insights on the design of Stirling engines and develop guidelines to identify the most suitable combinations of engine architectures and design parameters to address specific applications. The paper shows how the proposed framework can be applied to the design of Stirling engines for two different applications, namely waste heat recovery and combined heat and power generation for residential real estate units. Considering the identified customer needs for these two applications, the results of the study indicate that alpha-type Stirling engines are more appropriate for industrial waste heat recovery, e.g. heat treating furnaces and cement kilns, having a power output 50% higher for a given efficiency then other engine types. Beta-type engines result more beneficial for residential combined heat and power generation. Gamma-type engines result advantageous for low power applications such as toy models and tool kit engines.

Matching high ambitions with scarce resources is one of the primary challenges of aerospace and other industries concerned with the development of unprecedented infrastructures, on par with the technical challenges associated with developing new technology. Stakeholder objectives are often unclear due to highly exploratory business cases. Further ambiguity emerges from disagreement between stakeholders and decision makers called to formulate scientific, technological and policy requirements for new systems. This paper develops a structured approach, called the Delphi-based Systems Architecting Framework (DB-SAF), which has been conceived to develop recommendations to system architects concerned with the design of unprecedented large infrastructures for which objectives are ambiguous or unclear. The objectives of DB-SAF are to identify sources of ambiguity in the value proposition of a system architecture and the associated trade-space exploration, characterize and model sources of ambiguity, and assess the impact of requirement ambiguities on the architectural trade space. The proposed systems architecting approach is demonstrated in this paper through the assessment of a robotic Mars Sample Return Campaign, which serves as a test bed case study to describe the proposed methodology and to discuss its extension to other fields of engineering. The proposed framework integrates methods from systems engineering, computational systems architecting, multidisciplinary systems design and optimization, uncertainty modeling, utility theory, and social science research. It allows decision makers to visualize an architectural synthesis of aerospace systems, understanding adverse impacts of ambiguity, and supporting negotiations among stakeholders for efficient compromise in systems architecting.

A = total mass stage gear ratio A1 = propellant mass stage gear ratio Isp = stage specific impulse, s mEDS = total Earth-departure-stage stage mass (reference case is overlined), kg md = stage inert mass (reference case is overlined), kg mp = Earth-departure-stage propellant mass (reference case is overlined), kg mpl = cargo launch-vehicle payload mass (reference case is overlined), kg mp0 = Earth-departure-stage payload mass (reference case is overlined), kg mptank = tanker launch vehicle propellant payload mass (reference case is overlined), kg mtot = cargo launch-vehicle total mass (reference case is overlined), kg α = propellant fill ratio coefficient β = payload growth rate Γ = packaging efficiency ΔV0 = design delta V (reference case is overlined), m∕s λ = tare overhead fraction μ = stage inert mass fraction

Future large telescope arrays require careful balancing of satisfaction across the stakeholders’ community. Development programs usually cannot afford to explicitly address all stakeholder tradeoffs during the conceptual design stage, but rather confine the analysis to performance, cost, and schedule discussions, treating policy and budget as constraints defining the envelope of the investigation. Thus, it is of interest to develop an integrated stakeholder analysis approach to explicitly address the impact of all stakeholder interactions on the design of large telescope arrays to address future science and exploration needs. This paper offers a quantitative approach for modeling some of the stakeholder influences relevant to large telescope array designs—the linkages between a given mission and the wider NASA community. The main goal of the analysis is to explore the tradespace of large telescope designs and understand the effects of different design decisions in the stakeholders’ network. Proposed architectures that offer benefits to existing constellations of systems, institutions, and mission plans are expected to yield political and engineering benefits for NASA stakeholders’ wider objectives. If such synergistic architectures are privileged in subsequent analysis, regions of the tradespace that better meet the needs of the wider NASA community can be selected for further development.