Tradespace Investigation of a Telescope Architecture for Next-generation Space Astronomy and Exploration

Humanity’s endeavor to further its scientific understanding of the celestial heavens has led to the creation and evolution of increasingly powerful and complex space telescopes. Space telescopes provide a view of the solar system, galaxy, and universe unobstructed by Earth’s atmosphere and have profoundly changed the way people view space. In an effort to further advance space telescope capability and achieve the accompanying scientific understanding, the Massachusetts Institute of Technology (MIT), specifically, course 16.89 Space Systems Engineering, explored the tradespace of architectural enumerations encompassed within the design of an ultraviolet-optical-infrared (UVOIR) space telescope located at Sun-Earth Lagrangian Point Two (SE-L2). SE-L2 presents several advantages as an operating location for a UVOIR telescope such as a thermally stable environment and an orbit that allows the telescope to maintain a constant orientation with respect to all of the primary sources of heat and light. The main disadvantages associated with SE-L2 are caused by its relatively large distance from Earth, which marginalizes the effectiveness of real-time telerobotics because of latency and increases the cost of communications, launch, and servicing. Course 16.89 believes that, for this UVOIR application, the strengths of this operating location outweigh its weaknesses and therefore decided to explore the family of opportunities associated with SE-L2. This course used appropriate performance and system metrics to quantify the effectiveness of the aforementioned architectures and create a Pareto front of viable architectures. Evaluating the designs along the Pareto front allowed the course to characterize and group architectures and present these group-types to stakeholders for the selection of an optimal space telescope according to stakeholder requirements and resources. This course also developed sensitivity analysis, which allowed for a greater understanding of how architectural decisions affect the performance of the satellite. Segmentation, modularity, assembly, autonomy, and servicing were key aspects of this multidimensional analysis given the 16.8-meter class size and location of the telescope. Within the respective operating environment and for a spacecraft of similar characteristics, this model will allow stakeholders to predict the long-term operational effectiveness of different space telescope architectures and capture the synergistic effects of combining various architectural decisions into a spacecraft design. The following sections step through the aforesaid analysis and design efforts conducted in 16.89 beginning with Section III, which explicitly performs the stakeholder analysis and articulates the requirements of the mission. Section IV gives an overview of past designs and expands upon the architecture enumerations pertinent to this project, while Section V presents the methods and metrics by which those architectures will be evaluated and the system metrics which will be balanced and optimized in the creation of this space telescope. Section VI will present the model validation of this project and Section VII will discuss the results and analyses of the project. Finally, Section VIII will explore the future work opportunities of this project, while Section IX will present the conclusions and recommendations drawn from this project.MIT Department of Aeronautics and Astronautic

Analytical model and simulations of closed-loop rebreather systems for Earth and Space applications

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 181-187).Humans in extreme environments, regardless of whether in space or deep in the oceans of the Earth, rely on life support systems to be kept alive and perform their exploration missions. Diving is similar to extravehicular activities in its duration and the need for human respiratory sustaining. This thesis presents the development of an analytical rebreather model, which is the system that recirculates and conditions the air the diver is breathing during a dive. The capability of simulating rebreather performance is currently lacking in the diving commercial and military industry. We believe that the advantages of having such a model are multi-fold: it can be used for mission planning, evaluating the impact of adding a new technology or modifying existing parameters or operational regime on an hardware configuration without performing expensive and time consuming hardware tests. An analytical model, like the one developed in this thesis, can also be used in complement with hardware testing to fine tune systems and increase resource endurance through the application of different electronic control strategies. The developed Matlab/Simulink model of this rebreather is modular and can be generalized to study open, semi-closed or closed circuits, in which the breathing gas used is air, oxygen, nitrox or heliox. The system's operational environment can be the ocean's surface (1 atmosphere), space (less than 1 atmosphere pressure) or deep underwater (more than 1 atmosphere pressure). After introducing the analytical modeling process for the rebreather, this thesis goes on to explore the model's applications for the study of different oxygen control strategies in order to maximize the oxygen lifetime during a dive, as well as the model's applicability as an aid in accident investigations. We aim to determine what is the maximum endurance of a rebreather system, given a particular, set configuration of components, as well as to study the reverse problem: if we set a mission endurance, what architectures would be able to achieve this level? Additionally, we are interested in studying how the tradespace of diving depth versus the diving systems's endurance looks like and how more complex control methods can help in pushing the existent boundary toward higher endurance limits. We show that more complex control algorithms can extend the duration of the oxygen tanks in a rebreather by a factor of 6.35, and, when given a set endurance level, control can help lower the tank sizes by a factor of 4.by Ioana Josan-Drinceanu.S.M