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Space Colony Design Theory
Artist's concept of a Space Colony, circa 1976
Image Courtesy of NASA Ames Research Center
( The artwork is now in NASA archives )
We're going to build a "bicycle wheel" colony, such as is shown above and was discussed in the original version of O'Neill's The High Frontier, as a framework for a city in space. The internal environment will be much like living in a (shopping) mall that's three miles long and a hundred yards wide - and will require a lot less air to fill than a Bernall Sphere with the equivalent "gravity" environment would need. This design will also have considerably less usable area, and therefore a significantly smaller population capacity than other designs have, but our analysis indicates it's a more realistic initial goal.
We enthusiastically welcome comments on our analysis and efforts. A discussion group/forum and a mailing list will be established shortly, so that the discussion can be a public one.
Reference Model:
1 rpm rotation, 900 meters radius, "1 G" level 100 meters occupiable width divided between two counter-rotating sections. 8 "floors" within the level, each 5 meters closer to the axis than the previous, covers 80% of lower level, exposed area is sunlit. inner floor experiences .97 G. total colony area is 2,321,861 m 2, sunlit area is 565,487 m 2
2nd ring @ 450 meters ".5 G" (.46 G min) adds 1,145,326 m 2 total, 282,743 m 2 sunlit
2nd ring @ 600 meters (.67 G - .63 G) + 3rd ring @ 300 meters (.34 G - .30 G), instead of .5 G ring, adds 2,290,653 m 2 total, 565,487 m 2 sunlit - doubles sunlit, nearly doubles total area. Colony total area is 4,612,514 m 2, 1,130,973 m 2 sunlit.
Click here to see the spreadsheet calculation results.
assuming a colony population of 10,000, that allows 4965 ft 2 per person, of which 1217 ft 2 is sunlit. although this seems like a high number, that area has to include all manufacturing, recycling, food production and environment for the individual. otherwise, the colony cannot be self-sufficient.
if the average material depth for construction is 1/3 meter, nearly 1.6 million m 3 materials will be consumed. if enclosed space is 2x 5m-high floor volume, enclosed volume is 46 million m 3.
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Structure:
more tubular shape (i.e., more oval in sections on planes containing the axis of rotation, with the oval (ellipse) major axis parallel to the rotation axis) results in more surface area at a given [apparent] gravitation
fixed rotation rate concentric levels out to 1 G provide differing gravities for handicaps, experimentation, entertainment.
outer levels with lower angular velocities but higher linear rates also experience 1 G. construction outward is done at next inner's angular rate - with higher linear rate in effect - via suspension (very dangerous work if no safety net, best done by robots, lost parts become projectiles traveling at linear velocity on tangental track). once a keel is laid and suspended, it can be slowed to the correct angular rate for 1 G.
some colonies may want higher G rates for heavy-planet training.
counter-rotating rings/tubes cancel angular momentum. bearing plane between opposite rotations, with stepped velocity changes, provide wind barriers, block collisions. treadways on speed changes provide stepped travel rate increases. multiple barriers needed to isolate high speed changes. noise could be a problem. use mechanical track-jumping across speeds to reduce possibility of being caught between passing barriers - scissors effect. walkways probably wouldn't be workable - too much trouble maintaining seal integrity for air containment: shirt-sleeve environment would have to be provided by transit vessel.
central axis/tube stationary (as opposed to planar bearing surface) would concentrate the stresses on the core - too much torque?
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Materials:
tensile strength required to counteract centrifugal force may be limiting
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Distortions:
Things don't "fall" straight down - the apparent fall path bends against the direction of rotation.
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Vulnerabilities:
- mega meteor strike
- bomb blast disturbing structure
- panel attack from outside, screws pull out as panel buckles
- water leak from damaged panel
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Notes:
1 km radius, rotating once per 63.46975 seconds, lateral velocity 98.99494 m/s 9.8 m/s 2 (1 G) "downward" force, 6.283 km circumference (3.9 miles) - You're less than 2 miles walking distance from anywhere. speed differential between counter-rotating halves, at 1 G level, is 713 km/hr (443 mph)
1 rpm rotation (60 seconds), 900 meters radius, lateral velocity 94.24777 m/s 9.869604 m/s 2 (1.007 G), 5.655 km circumference (3.5 miles) - rotation can be used as a clock, two points on counter-rotating rims pass exactly 2x/minute. speed differential is 679 km/hr (398 mph)
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