Quote:
Originally Posted by Rupert
The effective gravity was given as 0.2g, and the diameter 650km, so the rotational period is about 2530 seconds, or ~0.024 rpm. The rotational velocity of the rim would be about 800 m/s.
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Radius 650 km, not diameter; the canonical rotation period for the original Gaea is 61 minutes and 3.5 seconds, and with a circumference of a hair over 4,000 km, a rotation speed of 1,114 m/s.
Quote:
Originally Posted by Anthony
It's debatable whether a ring configuration makes sense. The general virtue of a ring type configuration is that the atmospheric pressure can be supported the inside of the ring rather than along the entire radius of the spin compartment, reducing the amount of mass you need for atmospheric containment
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I thought the main virtue of a ring was that it's much simpler to set up passive sun-mirrors to light up the interior, without needing to install a large electrically-powered lighting system.
Quote:
Originally Posted by Anthony
, but this effect is reduced if there is a pressure difference between top and bottom of the chamber.
Judging from the diagram, the outer torus has a height of around 150 km. At 0.2G and 20C, the scale height of the atmosphere is roughly 40 km, so the pressure at the top is 2-3% of the pressure at the base, and you're barely saving anything.
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In Varley's source material, the spokes have valves at top and bottom, and have a regular cycle to pump air up three spokes at a time and down the other three.
Edit: With a ground-level atmospheric pressure of 2 bars, wouldn't that mean the atmospheric scale height is 80 km, so that at ~160 km, the "natural" pressure without pumping would be about 13% (or a quarter of a bar)?
Quote:
Originally Posted by Anthony
A cylinder with length 650 km and radius 250 km (i.e. just reversing the dimensions) has the same projected area but lower structural mass. It would rotate a bit faster (period about 26m instead of 42m) but has lower velocity, and is probably simpler to construct.
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In Spaceships terms, I think this would count as being built as SM+34 with 10 Open Space systems, instead of SM+35 with 5.
Thinking about it, it... has potential. The first choice I'd have to make is lighting, since the first options I can think of lead to different shapes. Eg, doubling the cylinder's surface area, making three sections transparent with long mirrors angled to shine down; or an electric sun-line down the middle; or go umbrella-style, with a large mirror focusing light down along a similar sun-line using mumble-mumble optics to distribute it down the whole length.
I can think of several reasons for this approach, and the only reasons I can think up against it are backfilled justifications involving handwaved long-term effects. (Well, plus the "reason" of the pure style of having a toroid the stars can be seen from. Maybe the sun-facing endcap of the cylinder could be a transparent hemisphere?)