Tom Brosz said:

>That's a lot of pressure for those glass ceilings to hold in. But I
>hereby dub the canyon colony the "Handramit Outpost."

The air pressure is why there's a layer of heated water between the layers of glass / fuzed silica. The glass would be thick enough that one could drive a truck over it and the water would be at least 5 feet thick. There's a design trade-off that's not clear to me. One doesn't want pure oxygen in the habitat because of the fire danger. That conclusion means 0.2 atm is the minimum pressure limit. However one doesn't want full pressure at 1 atm because it leads to too much mass in the ceiling. Too much ceiling also has the problem of reduced light transmission through the water. Five feet should allow adequate light transmission and provide good cosmic ray shielding but 50 feet would be too thick. I suspect that 0.5 atm pressure is the magic value for human habitation. However does that provide adequate fire protection? For agriculture only areas, the pressure could go down to 0.2 atm for a pure carbon dioxide atmosphere (the plants would like that). Farmers would have to wear oxygen bottles and breath pure oxygen through a mask. The canyon colony concept is full of interesting engineering tradeoffs.

I have about half a dozen more figures and diagrams to include (mostly spacecraft trajectory related). I'll throw in some commentary and then take it over to the Space Board. I don't want to take this "prime time" while the presentation is still half baked.

Gary