Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.mrao.cam.ac.uk/~tm419/downloads/The%20In-Situ%20Production%20of%20Oxygen%20Through%20the%20Vaporization%20of%20Lunar%20Regolith.pdf Дата изменения: Fri Apr 26 16:53:12 2013 Дата индексирования: Fri Feb 28 12:18:43 2014 Кодировка: Поисковые слова: propulsion

The In-Situ Production of Oxygen Through the Vaporization of Lunar Regolith

Tamela Maciel MUST Program at Goddard Space Flight Center Dr. Eric Cardiff, Mentor Summer 2008


Abstract and Introduction A vital component to our nation's current plan of extended lunar exploration is the ability for in-situ resource production. Oxygen is necessary for both life-support and rocket propulsion, so finding a way to effectively generate oxygen on the moon is of great interest to NASA and the future lunar missions. A variety of techniques have been proposed to extract oxygen from the metal oxide-abundant lunar soil. Taylor reviewed these techniques and suggested regolith pyrolysis as the optimal method of oxygen production [1]. Experimental testing at NASA GSFC is continuing to determine the feasibility of pyrolysis by indirect resistive heating for a number of applications, including oxygen production on the Moon. By subjecting the regolith to intense temperatures, the metal oxide bonds can be broken and the regolith vaporized, with the hope that the reduced oxides can then be condensed and the gaseous oxygen collected for use. The original prototype focused solar radiation through a large Fresnel lens and vaporized a sample of lunar regolith at temperatures upwards of 1500oC. Previous work has demonstrated that in the process, the metal oxide bonds within the soil will be broken [2]. The reduced oxides can then be rapidly condensed out while the oxygen remains gaseous and can be collected for later use. Terrestrial experiments to model this method have involved both solar radiation and resistive heating to vaporize different types of simulant lunar regolith, including MLS-1A and JSC-1A [3]. A new experimental setup is currently being assembled that improves on the prototype resistively-heated crucible. A larger vacuum chamber houses an uncovered, high-grade zirconia crucible wrapped with tungsten wire for heating, as shown in Figure 1 (Left). This wire connects to a power input from the bottom, delivering up to 160 DC volts. The crucible and stands are surrounded by several layers of tungsten foil shields, as shown in Figure 1 (Right).

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Tu ng ste n wir e- wra pp e d cru cib le Cha mb er Wa l l

Tu ng ste n fo il sh eets

Po wer in put

Figure 1. (Left) Wired-wrapped 1.65" diameter crucible connected to power. (Right) Side-view diagram of the chamber interior. Thermocouples fed through the top of the chamber measure the temperature of the simulant regolith as it is being heated, as well as the temperature of various points around the chamber itself. The turbo pump, pressure gauge, and an RGA mass spectrometer are mounted above the vacuum chamber, as shown in Figure 2. A window and shutter at the top of the chamber allow for IR temperature measurements and visual inspection during testing. This setup is designed to prove the possibility of releasing significant levels of oxygen and other volatiles from simulant regolith. RGA Turbo Pump

Thermocouples

Figure 2. Current setup for regolith pyrolysis without a cryocooler.

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Testing of this new setup is currently underway, with the crucible and wire both reaching high temperatures. The crucible structure is being investigated, as one test actually cracked the crucible due to extreme temperatures. A new crucible is being manufactured for further testing.

Goals and Purpose of the Project The idea of extracting and utilizing resources on the moon has been under development for a number of applications. The propulsion branch at Goddard is interested in pursuing oxygen production through pyrolysis because oxygen is a key oxidizing component to many rocket propellant systems, in addition to being essential for life support. Dr Eric Cardiff has been working with this concept for several years now, starting from scratch and refining and testing new ideas in the experimental setup and procedure. My aim this summer was to build a new setup, implementing some of the techniques learned in the previous summer, making the setup bigger, more thermally efficient, and more convenient for testing. I started ordering parts, drawing up models, and researching new crucible suppliers from the first week. As things gradually came together, I also tested some of the instruments to be used during experimentation, including an RGA mass spectrometer and optical pyrometer. The setup was just recently complete as of the second week in August, 2008, and initial testing has begun. Unfortunately, I will be unable to continue with the project, as I head back to school, but it will be passed over to my co-worker for further development. In short, the new setup seeks to improve the resistively-heated vacuum pyrolysis setup, and is designed to achieve a higher maximum crucible temperature and improved thermal efficiency. The previous chamber was limited to 1000°C, and the current setup can attain temperatures in excess of 1300°C.

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Impact of the MUST Internship on My Career Goals As a contrast to the astrophysical research I completed in the summer of 2007, this year I specifically requested to be placed in a lab for some hands on experience. As a physics major, I felt that an internship in an engineering branch would be an invaluable experience that would help shape the direction of my future education. I know that I am deeply passionate about astrophysics but I also know that I would find it difficult to spend my days in front of a computer running simulations or reading papers, as I saw so many of the astrophysicists doing last summer. Also, to date, my education has been primarily focused on theory and computation, with only basic physics lab courses. So I felt it essential to gain some much needed experience working on a hands-on project surrounded by engineers that could lend practical skills and advice to my education. Working in the propulsion branch this summer was exactly the type of internship I was looking for. My mentor, Dr Eric Cardiff, has a great way of offering advice and suggestions to guide the project, but leaves the bulk of the decisions and design up the student, so that they can glean the most from the experience as they immerse themselves in the project and really take ownership and pride in the work. Eric immediately let me get to work on the project and gave me the independence and trust that I was craving. From the beginning I felt like an equal team player, and although I had much to learn, I still felt respected for my opinion. This is the ideal kind of working environment that I would love to have later on in my career. After this summer, I strongly feel that I will need to have some sort of hands-on lab work as a part of my career in order to be truly happy with my job. I had such a wonderful time working in a lab all summer, bolting together vacuum chambers, setting up mass spectrometers, and learning so much practical knowledge along the way that I don't think I could ever be

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completely satisfied working without this aspect. This summer has made me determined to find a way to mesh the scientific theories of astrophysics with the hands-on design and testing of the spacecraft that are sent up to collect the data on which these theories are based. An ideal career for me would be to work as the lead scientist on a research based mission, helping to design and build the spacecraft such that the scientific goals are best accomplished. After two years in the MUST program, completing internships in two very different divisions, I have had the chance to see both the science and the engineering sides of NASA, and have found things I love in both. These opportunities have certainly shaped the type of career I intend to pursue and I remain eternally thankful to my mentors, Goddard Space Flight Center, and the MUST program for giving me the support to discover the possibilities that lie ahead.

References [1] Taylor L.A. & Carrier W.D. III. (1993). Oxygen Production on the Moon: An Overview and Evaluation, Resources of Near Earth Space. [2] Matchett J.P. (2005). Production of Lunar Oxygen Through Vacuum Pyrolysis. Masters Thesis. The George Washington University. [3] Cardiff E.H., Pomeroy B.R., Banks I.S., Benz A. (1997). Vacuum Pyrolysis and Related ISRU Techniques. STAIF Conference Paper.

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