I " (Memo; G. K. O'Neill) . (Supplementary to "Graphics 12/10/75"and accompanying photograph and sketches} , ~ 12/16/75 On graphics for space-colony work: A request has just been received for my testimony before a Senate subcommittee in mid-January. In order to prepare for this, I have had to consider carefully the present state of. knowledge about physiological and mechanical constraints which would control the design of early space habitats. As I have emphasized, the details of habitat design are subsidiary to the key elements of the space-colony concept, but the many requests for information about graphics at this time force some tentative choices ·to be made, subject of course to later modification. The present best guesses obtained from senior ·people in physiology and shield design are that· with selection ( i.e. non-random population) similar to the selection which leads to the workforce on the Alaskan p~peline or _other demanding construction jobs a rotation up to 2 to 3 rpm would be possible. It is guessed ( at this point no solid information exists) that some time daily at a g-level of at least 1/3 earth-normal is necessary, to avoid bone calcium loss. For· economic and logistic reasons, it would be optimum to have an initial, lightweight construction_ station, unshielded against cosmic rays, which could build a habitat (longterm) in such a way that both habitat and construction station would end up shielded. There may be many solutions to this problem; the only one that I have seen so far that satisfies all these conditions, and in addition is economical of mass and provides a final habitat geometry which is spacious, ha~ a clear image of the sun, and would be safe against chain-reaction explosive failures in the event of window breakage is shown in the attached figure. It is only a slight variant of the Bernal-sphere geometry previously discussed. In the variant, the windows occupy the regions from 15 degrees to thirty degrees from the axes. The average sunangle corresponds to about 10:00 am on a June day. All elements of the geometry not shown are identical to the earlier Bernal-sphere studies. A : The initial construction station, a sphere 225 meters in diameter. Gravity at its equator would be 0.48 earth-normal, at a rotation rate of 1.95 rpm. The.volume would be 6 million cubic meters, or enough for up to 2 million square feet of floor space at a ceiling height of 9 feet. This would house the workforce and provide all the moderate~scale working areas for initial construction. In the final state it would be tethered by light cables to the equator of the larger sphere. B : The main sphere, 236 meters in diameter, would provide earth-normal gravity at its equator at a rotation rate of 1.95 rpm. The main difference from the earlier version of the sphere is that the sun-angle would correspond to a time closer to noon, and that the regions between 45 and 60 degrees from the equator, previously occupied by windows, are now usable (high terraced planting, steep paths, etc. Vineyards?) C : These are now planar mirrors, which need not rotate. They are backed by non-rotating shielding. D : These are conical shields, non-rotating, which complete the shield coverage, preventing slant cosmic rays from hitting the land areas. They can be about 12% thinner than the other shields due to slant angle. E : As before, this is a passage of 50 meter diameter, for air circulatio. to the radiator and to agricultural areas (if the latter is desired) and as a zero-gravity corridor for personnel and equipment moving to and from the loading docks. F: This is a zero-gravity region for practical access to (A) and also for recreation (human-powered flight etc.) It could be bounded by light nylon netting cylinders of 50 meter diameter. Low-gravity pools etc. could be either as before, or in (A). is desian is only ~. ~xl06tons.
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