Design and development of advanced load sensors for the International Space Station

Abstract

In preparation for the construction of the International Space Station (ISS) a risk mitigation experiment was conducted to quantify the crew-induced disturbances to the microgravity environment on board a spacecraft during a long duration space flight. Achieving a microgravity environment for scientific experiments is one of the primary objectives of the ISS. While numerous measurements have been made to characterize the overall acceleratory environment on the Space Shuttle and on Mir, the contribution of astronaut motion to the disturbances was little understood. During the first phase of the ISS Program, the stay of U.S. astronauts on the Russian Orbital Complex Mir, the Enhanced Dynamic Load Sensors (EDLS) Spaceflight Experiment measured from May 1996 to May 1997 the forces and moments that astronaut exerted on the space station. Using four instrumented crew restraining and mobility devices, a handhold, two foot loops, and a touchpad, 133 hours of data was recorded during nominal crew activities and scientific experiments. The thesis gives a historical overview of the research that has been conducted to quantify the crew spacecraft interaction. A description of the EDLS experiment set-up and timeline as well as the custom-designed experiment hardware and software is provided. Due to an on-orbit failure of the original data acquisition system, a replacement computer was used to continue the experiment. The post-flight efforts to calibrate the replacement hardware, catalog the data files, and the tests to determine the condition of the sensors are presented. A cross-platform EDLS-specific software package was developed to aid in the analysis of the spaceflight data. The requirements, underlying signal processing equations, and the implementation in MATLAB are discussed. A preliminary design of advanced sensors for the ISS is developed in the thesis. While, retaining the proven strain-gage based method of sensing forces and moments, the restraining portion of the sensors was redesigned to aid astronauts better and can be easily exchanged for a different functionality. While having a volume of only 5800 cubic centimeters, the sensor electronics unit (SEU) incorporates most of the features of the original computer eight times its size. The SEU features an advanced embedded computer system and a Java-based operating system. Feedback on the loads applied can be provided in near real-time to the crew to aid the astronauts in maintaining a quiescent environment on the station during critical microgravity experiments.