55th International Astronautical Congress 2004 - Vancouver, Canada IAC-04-IAA.3.8.3.02 TECHNOLOGY DEVELOPMENT AND DEMONSTRATION CONCEPTS FOR THE SPACE ELEVATOR David V. Smitherman, Jr., Architect Technical Manager, Advanced Projects Office NASA Marshall Space Flight Center, Huntsville, Alabama, USA E-mail: [email protected] ABSTRACT In 1999, the author managed for the National Aeronautics and Space Administration (NASA), a space elevator workshop at the NASA Marshall Space Flight Center to explore the potential feasibility of space elevators in the 21st century, and to identify the critical technologies and demonstration missions needed to make the development of space elevators feasible. Since that time, a NASA Institute for Advanced Concepts (NIAC) funded study proposed a simpler concept for the first space elevator system using more near-term technologies. This paper will review some of the latest ideas for space elevator development, the critical technologies required, and some of the ideas proposed for demonstrating the feasibility for full-scale development of an Earth to Geostationary Earth Orbit (GEO) Space Elevator. In conclusion, this paper finds that the most critical technologies for an earth-based space elevator include Carbon Nano-Tube (CNT) composite materials development and object avoidance technologies; that the lack of successful development of these technologies need not preclude continued development of space elevator systems in general; and that the critical technologies required for the earth-based space elevator are not required for similar systems at the Moon, and other locations. BACKGROUND In the 1990’s, advances were made by NASA Study: several researchers indicating that carbon To investigate this possibility the author, in nano-tubes might be the high strength 1999, managed for NASA a space elevator material needed for fabrication of space workshop at the NASA Marshall Space elevators from geostationary orbit down to Flight Center in Huntsville, Alabama, to the surface of the Earth. These findings explore the potential feasibility of space have led to the continued development of elevators in the 21st century, and to identify nano-tubes for structural applications and the critical technologies and demonstration serious investigations into the space missions needed to make development of elevator concept as a potential space elevators feasible.1 Specifically, this infrastructure element for space science study identified CNT composites, tether missions, human space exploration, and demonstration missions, tall tower commercial space development. construction technology, electromagnetic ————————— propulsion, and space infrastructure development in general as major technology developments required before a space elevator could be developed. The time frame for possible space elevator 1 55th International Astronautical Congress 2004 - Vancouver, Canada construction was assumed to be greater In light of the prior studies, and the current than 50 years—in the latter half of the 21st activities, this paper will review some of the Century. latest ideas for space elevator development, the critical technologies required, and some NIAC Study: of the ideas proposed for demonstrating Since that time, a NIAC funded study of the their feasibility. Space Elevator proposed a concept for a simpler system using more near-term technologies.2 Not required were the former findings for tall tower construction CRITICAL TECHNOLOGIES technology, electromagnetic propulsion, or extensive space infrastructure development. NASA’s approach to developing new space Instead, this simpler approach used more systems for future deployment includes the near-term technologies including CNT identification of all critical technologies by composite ribbon development, electric ranking their level of maturity on a scale propulsion, wireless power transmission, known as a Technology Readiness Level mechanical crawlers, and collision (TRL), Figure 1. This approach makes it avoidance systems. In addition, the NIAC easy for technologist to identify the study resulted in a book “The Space technologies that need to be funded for Elevator”3 that provides a good detailed continued development, as well as providing description of the concept and the an overall gauge for project managers as to economics of the space elevator from a the likelihood that the project is ready, or not business perspective. The premise of this ready, for full scale development. study was that the space elevator can be built with more near-term technologies that Technology Readiness Levels: may make construction possible in the first Basic Technology Research comprises TRL half of this century—perhaps as early as 15 1: Basic principles observed and reported; years away. and TRL 2: Technology concept and/or application formulated. The CNT composite Current Activities: ribbon development is probably in the TRL 2 As a result of these studies, serious interest category because the CNT has been in the space elevator as a potential future observed to have the required strength at space infrastructure element has grown in the nano-scale, but large-scale composite both technical, public, and private circles. In fibers have yet to be developed with the 2004, NASA and the Institute for Scientific required strength for construction of a space Research established a cooperative elevator. Since the ribbon structure is the agreement to conduct further investigations primary component of the space elevator, into the space elevator concept. Specific and there are no know substitutes, the investigations to be conducted include a entire system for Earth to GEO applications more detailed systems engineering study of is considered an advanced concept worthy the entire concept, continued development of study and technology development, but of the high strength CNT composite not far enough along to warrant major materials, ribbon dynamics analysis for a full project funding. In other words, there is no length space elevator structure including guarantee that adequate time and money control systems concepts for object will mature this technology. Note also the avoidance, ribbon design, prototype red color coding, indicating that critical climbers, and collection and production of technologies at this level should not yet be technical papers and educational materials counted on for near-term projects. on the space elevator for the technical community and the general public. 2 55th International Astronautical Congress 2004 - Vancouver, Canada Figure 1: Technology Readiness Level Technology Development comprises TRL 3: environment; TRL 8: Actual system Analytical and experimental critical function completed and “flight qualified” through test and/or characteristic proof-of-concept; TRL and demonstration (Ground or Flight); and 4: Component and/or breadboard validation TRL 9: Actual system “flight proven” through in laboratory environment; and TRL 5: successful mission operations. Some of the Component and/or breadboard validation in tether deployment hardware, spacecraft relevant environment. Many of the systems, and ground stations fit into these mechanical systems for the space elevator categories because similar systems have fit into these categories, in that similar flown on previous space missions, or have mechanisms exist, but have never been put been tested in a relevant environment. into the configurations required for the When all technologies have reached this space elevator, and/or have never flown in a level of maturity, it is relatively easy to put space environment. All required together a cost and schedule for technologies in these categories are development that can be done, giving the assumed to be mature enough that they project manager a green light to successful could be developed for the project given project execution. enough time and money. Hence, the yellow color could be interpreted as proceed with TRL Evaluation: caution. Given the above categorization of critical technologies, a first cut was made at System/Subsystem Development comprises examining the space elevator elements in a TRL 6: System/subsystem model or work breakdown structure (WBS), and prototype demonstration in a relevant ranking them by TRL. The following Figures environment (Ground or Space); TRL 7: 2-4 list the space elevator WBS elements in System prototype demonstration in a space the left column, and then rank them by color 3 55th International Astronautical Congress 2004 - Vancouver, Canada coding indicating the kind of development identical indicating where we think the and testing likely required for maturity in the technologies are today for all the space following columns. Colors indicated are as elevator systems. The next 3 columns under described above, red for the lowest TRL 1- “Ground Tests” are designed to advance 2, (stop, we have a lot of work to do here); some technologies from a lower level TRL yellow for TRL 3-5 (send money and we will in red or yellow, to a higher TRL of yellow or make it work); and green for TRL 6-9 (we green. Note that the chart extends color know how to do this and can estimate a bands across all columns, but that not every reasonable cost and schedule for experiment uses every technology. The next development). 3 columns under “Space Flight Tests and Demonstrations” are designed to advance The columns following the WBS column are mid-range technologies in yellow into a progression of experiments and integrated systems for flight in green. Once developments