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EVA Walk-Back Limit Calculation Using the Virtual Spacesuit
No full textClaas Olthoff, Technical University of MunichICES403: Extravehicular Activity: OperationsThe 48th International Conference on Environmental Systems was held in Albuquerque, New Mexico, USA on 08 July 2018 through 12 July 2018.In order to ensure astronaut safety during extravehicular activities (EVA) on planetary surfaces, the operational paradigm is to limit the distance crew members would have to walk back to a safe haven in case of a hardware failure. For the Apollo missions, this distance was calculated prior to the mission based on the average consumption of oxygen, sublimator feedwater and battery power and assuming a constant walking velocity of the astronaut between the break-down site of the lunar roving vehicle and the lunar module. During the actual EVA the walk-back distance was recalculated based on the actual consumption rates.
This paper presents a method for the calculation of the walk-back limit for future human exploration missions that additionally takes additional, dynamic factors into account, for example the projected metabolic rate of the astronauts during the traverse back to the safe haven due to the slopes of the terrain. To achieve this, the Virtual Spacesuit (V-SUIT) is utilized, a dynamic EVA simulation system developed at the Technical University of Munich.
Two case studies are presented: An EVA from the Apollo 17 mission and a notional exploration EVA at the lunar south pole using a current NASA spacesuit architecture.
Results show that the walk-back limit used during Apollo 17 was conservative and they demonstrate the impact of new spacesuit technologies on the calculated distances
Continued Development and Validation of the Virtual Spacesuit Using Apollo 17 Data
Get PDFClaas Olthoff, National Aeronautics and Space Administration (NASA), USICES401: Extravehicular Activity: SystemsThe proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.This paper documents the continued development and further validation of a spacesuit simulation system called the Virtual Spacesuit (V-SUIT). V-SUIT is a MATLAB® application that combines models of a spacesuit pressure garment, portable life support system and a comprehensive human model, with a dynamic thermal simulation of the environment on an airless planetary surface like the Moon. This holistic approach enables V-SUIT to depict the complex interactions between spacesuit, human and the environment in different domains.
In a first validation step, the second extravehicular activity (EVA) of the Apollo 15 mission was recreated in V-SUIT and the simulation results were compared to original flight data, which was provided by NASA’s Spacesuit Knowledge Capture Program. This validation demonstrated that V-SUIT is capable of depicting the dynamic behavior of all components involved. It also uncovered shortcomings in the models and the underlying simulation system architecture, for example the inadequacy of the gas flow rate solver. This paper presents how these shortcomings were addressed and simulation results of the updated system presented.
Since the models were created using the Apollo 15 data as a guideline, it needed to be proven that the models are indeed generic and not custom-tailored to that specific EVA. The simulation system was therefore used to re-create the second EVA from the Apollo 17 mission, which used the same model of spacesuit, but with a different astronaut at a different location on the lunar surface. The validation data was again provided by the Spacesuit Knowledge Capture Program.
It is discussed how well V-SUIT is able to predict the dynamic behavior of the spacesuit and which areas of future work can be derived from the results
V-SUIT Model Validation Using PLSS 1.0 Test Results
Get PDFThe dynamic portable life support system (PLSS) simulation software Virtual Space Suit (V-SUIT) has been under development at the Technische Universitat Munchen since 2011 as a spin-off from the Virtual Habitat (V-HAB) project. The MATLAB(trademark)-based V-SUIT simulates space suit portable life support systems and their interaction with a detailed and also dynamic human model, as well as the dynamic external environment of a space suit moving on a planetary surface. To demonstrate the feasibility of a large, system level simulation like V-SUIT, a model of NASA's PLSS 1.0 prototype was created. This prototype was run through an extensive series of tests in 2011. Since the test setup was heavily instrumented, it produced a wealth of data making it ideal for model validation. The implemented model includes all components of the PLSS in both the ventilation and thermal loops. The major components are modeled in greater detail, while smaller and ancillary components are low fidelity black box models. The major components include the Rapid Cycle Amine (RCA) CO2 removal system, the Primary and Secondary Oxygen Assembly (POS/SOA), the Pressure Garment System Volume Simulator (PGSVS), the Human Metabolic Simulator (HMS), the heat exchanger between the ventilation and thermal loops, the Space Suit Water Membrane Evaporator (SWME) and finally the Liquid Cooling Garment Simulator (LCGS). Using the created model, dynamic simulations were performed using same test points also used during PLSS 1.0 testing. The results of the simulation were then compared to the test data with special focus on absolute values during the steady state phases and dynamic behavior during the transition between test points. Quantified simulation results are presented that demonstrate which areas of the V-SUIT model are in need of further refinement and those that are sufficiently close to the test results. Finally, lessons learned from the modelling and validation process are given in combination with implications for the future development of other PLSS models in V-SUIT
Validation of the Virtual Spacesuit Using Apollo 15 Data
No full textClaas Olthoff, Technical University of Munich, GermanyICES401: Extravehicular Activity: SystemsThe 47th International Conference on Environmental Systems was held in South Carolina, USA on 16 July 2017 through 20 July 2017.This paper presents results from the validation of a spacesuit simulation system called V-SUIT, which has been under development at the Technical University of Munich since 2012. V-SUIT combines models of spacesuit pressure garments, portable life support systems (PLSS) and a comprehensive human model, with a dynamic model of the thermal environment on an airless planetary surface. This holistic approach enables V-SUIT to depict the complex interactions between spacesuit, human and the environment in several different domains. For the purpose of validating V-SUIT, a model of the Apollo A7LB spacesuit was created and the extravehicular activities (EVAs) performed during the Apollo 15 mission were chosen as a case study. Original flight data recordings were provided by NASA’s Spacesuit Knowledge Capture program.
The results of the validation show that V-SUIT is generally capable of reproducing all important aspects of the system’s dynamic behavior. Even though the simulated values do not exactly match the flight data, the trends and time dependent changes are consistent. The differences between flight and simulation data can mostly be explained by the lack of exact technical specifications for the systems that were modeled, the uncertainty associated with metabolic rate as measured during the mission and other modeling inaccuracies.
As part of a global sensitivity analysis, the simulations of each of the three EVAs was performed on a model of the actual topography at the landing site, as well as on a flat surface, with identical surface properties and lighting conditions. The resulting data are also presented and discussed.
With this successful correlation, V-SUIT now has a reference case that can be used in the analysis of future spacesuit systems, enabling the study of changes to the system configuration like new PLSS components or different pressure garment layups
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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