Takuto Ishimatsu

Hazard Analysis of Complex Spacecraft Using Systems-Theoretic Process Analysis

A new hazard analysis technique, called systems-theoretic process analysis, is capable of identifying potential hazardous design flaws, including software and system design errors and unsafe interactions among multiple system components. Detailed procedures for performing the hazard analysis were developed, and the feasibility and utility of using it on complex systems was demonstrated by applying it to the Japanese Aerospace Exploration Agency H-II Transfer Vehicle. In a comparison of the results of this new hazard analysis technique to those of the standard fault tree analysis used in the design and certification of the H-II Transfer Vehicle, systems-theoretic hazard analysis found all the hazardous scenarios identified in the fault tree analysis as well as additional causal factors that had not been identified by fault tree analysis.

Generalized Multicommodity Network Flow Model for the Earth–Moon–Mars Logistics System

Simple logistics strategies such as “carry-along” and Earth-based “resupply” were sufficient for past human space programs. Next-generation space logistics paradigms are expected to be more complex, involving multiple exploration destinations and in situ resource utilization. Optional in situ resource utilization brings additional complexity to the interplanetary supply chain network design problem. This paper presents an interdependent network flow modeling method for determining optimal logistics strategies for space exploration and its application to the human exploration of Mars. It is found that a strategy using lunar resources in the cislunar network may improve overall launch mass to low Earth orbit for recurring missions to Mars compared to NASA’s Mars Design Reference Architecture 5.0, even when including the mass of the in situ resource utilization infrastructures that need to be predeployed. Other findings suggest that chemical propulsion using liquid oxygen/liquid hydrogen, lunar in situ resou...

Planning an itinerary for an electric vehicle

The steady increase in oil prices and awareness regarding environmental risks due to carbon dioxide emissions are promoting the current interest in electric vehicles. However, the current relatively low driving range (autonomy) of these vehicles, especially compared with the autonomy of existing internal combustion vehicles, remains an obstacle to their development. In order to reassure a driver of an electric vehicle and allow him to reach his destinations beyond the battery capacity, we describe a system which generates an energy plan for the driver. We present in this paper the electric vehicle ecosystem and we focus on the contribution of using the generalized multi-commodity network flow (GMCNF) model as a vehicle routing model that considers energy consumption and charging time in order to ensure the usage of an electric vehicle beyond its embedded autonomy by selecting the best routes to reach the destination with minimal time and/or cost. We also present some perspectives related to the utilization of autonomous electric vehicles and wireless charging systems. We conclude with some open research questions.

A Proposal for Graph-Theoretic Modeling Approach to Resource-Economy in Spaceflight Campaign Logistics

NASA’s new direction for human spaceflight reaffirms that Mars is the ultimate goal of human exploration of the inner solar system. In response to this background, we can expect to see an increasing number of robotic explorations of Mars over the next several decades, followed by human missions. In a period of transition to a new era of space exploration, the question is what the next space logistics paradigm should be. Adding to the technical challenges, logistical concerns should be considered far in advance. A well-planned logistics strategy is essential to balance risks, ensure robustness, and achieve maximum exploration capability. Space logistics is an emerging topic in recent years as we start to see space exploration not as a set of isolated missions but as an intricately-linked exploration campaign. A vast body of research exists for terrestrial transportation networks and supply chain logistics in business and military applications. However, space exploration introduces several fundamental differences such as infrequent launch windows, long transport durations, and minimal cargo capacity. The past studies on space logistics have been mainly focused on a “vehicle” perspective such as propulsive feasibility, cargo capacity constraints, manifesting strategies, and demand satisfaction, assuming a pre-defined logistics network. However, there is more than one way to define a logistics network (transfer points) between origin and destination such as ISRU on the surface nodes and resource depots in orbital nodes or Lagrangian nodes. Therefore, this paper proposes a graph-theoretic modeling approach to analyze spaceflight campaign logistics seeking for “resource-economy” from a “network” perspective. We define resource-economy in the context of space exploration, identify the building blocks of logistics network (nodes, arcs, and costs), and present a quick example to show the potential benefits of ISRU and resource depots. Once the generic framework has been modeled and implemented, it will be able to be used a proof of concept, providing a useful index of resource-economy to quantitatively compare different concepts of exploration. Moreover, this framework will not only evaluate and compare specific scenarios but also find the key drivers of resource-economy in space logistics.

Near-Term Mars Sample Return Using In-Situ Oxygen Generation

A Mars sample return mission was designed to transport a 0.5-kg sample from the Martian surface to Earth using oxygen manufactured from in-situ resources to burn fuel brought from Earth. The use of locally-generated oxygen (In-Situ Resource Utilization, or ISRU) can reduce the mass of ascent-related systems required to be landed on Mars for a fixed payload size, or can increase the payload returned from Mars for a fixed mass of ascent systems. For the baseline case of a 0.5-kg sample, a 32% savings occurs in the landed mass of the ascent systems, which transport samples from the surface to orbit. Additionally, the benefits of locally-generated oxygen increase considerably as the sample size increases.

LIMIT: Lunar Infrared Modular Interferometric Telescope

The goal to return humans to the Moon by 2020 raises the possibility of leveraging both the transportation architecture currently under development by the Constellation program and the physical presence of humans on the Moon. This paper presents the design of an interferometric telescope array at the lunar south pole that takes advantage of these transportation and deployment capabilities. A permanently shadowed lunar crater provides a stable site for very low temperature observations, ideal for observing extrasolar planets, star formation and active galactic nuclei.

A Graph-Theoretic Modeling Framework for Resource-Economy in Space Logistics

In transition to a new era of space exploration, the question is what the next space logistics paradigm should be. The past studies on space logistics have been mainly focused on a “vehicle” perspective such as propulsive feasibility, cargo capacity constraints, manifesting strategies, and crew and vehicle demand, all assuming a predefined logistics network. Against this background, a graph-theoretic modeling approach to space-based resourceeconomy from a “network” perspective has been proposed. Built on this proposal, this paper continuously develops a graph-theoretic modeling framework and presents a multicommodity network flow formulation using flow transformation matrix. The proposed modeling method is demonstrated with a case study of cislunar architecture for human exploration of Mars. Mars capture orbit (MCO) is selected as a problem boundary node with a demand based on Mars Design Reference Architecture 5.0 and the problem is formulated as a linear programming (LP). The optimized network flow suggests that the resource depot should be located in Earth-Moon Lagrange point 2 (EML2), the orbital transfer vehicle should travel between geostationary transfer orbit (GTO) and EML2 like a pickup bus, and the Mars Transit Vehicle (MTV) should be injected into trans-Mars trajectory from EML2. It is found that utilization of lunar resources could reduce the total resource required to satisfy the same demand at MCO by up to 35.8%. Nomenclature