Questions on Physics and Space Exploration sites about Gravity Balloon Habitats

This blog is a bit of a tangent, which stemmed from questions which were being tossed around on the Q&A site Physics Stack Exchange.  Since I started writing, another site, Space Exploration Stack Exchange has started up.  I do ask questions about specific components of the gravity balloon habitat concept, but there have also been some relevant questions that other users ask, which just happen to be pertinent.  I went through and quickly grabbed a list of these questions here.  Surely there will be more in the future but this covers all that I could find today.  Some of them correspond exactly to posts on this blog, and that was my intention.

Physics (http://physics.stackexchange.com/)

• Keeping air in a giant gravitationally-bound space balloon -Addresses the basic concept of center-caves.
• Amount of material required for a pressure tank - Concluded that structural materials scale directly proportionally to the pressure x volume product with conventional pressure vessels.
• Stress in a thick-walled pressure vessel -Asks how the structural materials would change if the pressurized volume was small compared to the vessel.  It seems to be a more restrictive case.
• Attenuation mass-thickness for sunset light - I wanted to get these parameters for the transport of sunlight within large space habitats, and we found them.
• Can a minimum ultimate tensile strength (UTS) for an asteroid be established based on its diameter and rotation? - Turns out that some asteroids rotate so fast that their geosynchronous orbit is effectively below the surface.  This is rare, and exclusive to small bodies.
• Effect of water on wobble of rotating structure - Interesting query about management of rotating artificial gravity tubes.  Turns out that water will have some very spooky effects, like pushing a half-full jug of milk on the counter.  But this isn't necessarily a bad thing.
• Can structural trusses in centrifuges be helpful at all? -Compared the structural requirements of a "barbell" type of artificial gravity structure to a simple ring.  Turns out the barbell is easier to build, but for complicated reasons.

Space Exploration (http://space.stackexchange.com/)

• What is the hollow asteroid concept in "Mining the Sky" - A similar concept is purportedly mentioned in this book, although I have yet to find out what that concept is.
• Method to estimate asteroid density based on spectral type -I've started to use the method from my reference here.  You have to factor in porosity, which has potential problems, but it's better than using no density estimation routine.
• What stability issues plague long artificial gravity cylinders? -Kalpana One is a recent proposal for a rotating space station, which limits itself to a "stubby" shape.  Exactly why was discussed, and I've adopted the design thinking myself.
• How to derive asteroid mass/size estimate from JPL parameters - Absolute magnitude is a measure of brightness of an object from 1 AU, so this gives us a very good estimation of diameter of a spherical object if the albedo is know.  Albedo is often not known.
• Full list of asteroids that have been optically imaged as of 2013 - Similar to a post I made on the subject.  There turn out to be more than what I gave credit to.
• Theories of what asteroid macroporosity actually means - Some dialogue on the nature of rubble piles.  The packing factor is surprisingly low for some asteroids, and this reflects a fairly recent area of research.
• What is the range of strength for asteroidal materials? - I was somewhat thinking that asteroid materials could be used to build structures in space without any processing.  Still not sure if that works.
• Are there any theoretical size limits of man-made space stations/structures? - About self-gravitation.
• In space can the difference in temperature between the inside and outside, provide useful energy? - One of my favorite questions.  Has lot of interesting implications related to Landauer's Limit and our thermodynamic existence.
• What is the largest naturally occurring body that could be hollowed and safely lived in? - Question sort of converges on the idea of a gravity balloon, although it wasn't intended.