melts. The solar furnace does not require additional power for operation however. Both of these techniques are not as familiar to metal processing as conventional techniques. This will involve additional experimentation in space before being selected for use. The cutting of the ET into segments is attractive for several reasons. The first is that the cutting of the hydrogen tank into strips can supply many pieces of aerospace grade weldable 2219 aluminium measuring 5 feet wide by 60 - 80 feet long. We also have all the engineering drawings for these strips (20). Almost any space structure is possible if the technology of cutting and welding is proven in space. The point in the cutting and welding process is that we are very familiar with the behavior of these pieces in ground based applications and can transfer this experience to orbital operations. Another reason for the orbital cutting is the isolation for future use of several aluminium alloys which make up the overall tank. The behavior of the alloys by themselves is well known. The different alloys that make up particular portions of the ET can be isolated from one another by carefully planned and executed cutting for future welding, melting, and forming into the desired structures (92). In a space-based operation, the cutting and welding of structures will be an early desired (if not required) activity. Because of the use of known technologies, the cutting and welding of the ET sections will be a valuable addition to the space construction ’bag of tricks’. It is not particularly complex and does not require a particularly expensive R&D investment. The challenge is what to do with an essentially unlimited supply of potential structural segments at the rate of 30 - 35,000 pounds per delivered ET. Clearly, some sort of market study needs to be made in this regard (20). IV. Complete Melting and Refining Another structural technique is the complete melting of the ET and the on-orbit fabrication of structural members such as thin shells, beams, rods, channel sections, or other controlled extrusion processes. There are a large number of proposed facilities for the melting of the ET in orbit and the future use of the melted aluminium from the melt. This is a somewhat more complex activity than the cutting and welding and will require additional R&D and training. The fabrication of structural members will require the
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