Is internal dirt counted among radiation shielding?

> So, it would seem to me that you could forego the external radiation shield,
> at least for the areas of the habitat which are "underfoot."

Sorry, to follow up my own post here, but I've just found the Kalpana habitat design by Al Globus et al., described first in 2000 [1] and just presented again at the 25th ISDC [2]. This design does exactly what I was thinking: the radiation shielding is all inside the pressure shell, in the form of lunar regolith which doubles as soil for plants. The authors argue (correctly, I think) that having an external non-rotating shield introduces an unnecessary risk of catastrophic failure (i.e., collision with the shield).

The also happen to mirror some other design decisions I'd been favoring, such as having nested internal cylinders (which I call "decks") and the use of artificial lighting for agriculture. It's satisfying to see that people smarter than myself have come to these conclusions as well! Of course they also thought of some things I had not, such as the rotational instability of a long cylinder.

This is a very interesting design, and if you haven't seen it already, I highly recommend a read of the references below.

Best,
- Joe

[1] http://alglobus.net/NASAwork/papers/KalpanaOneASCE2006/KalpanaOneASCE2006.pdf
[2] http://alglobus.net/NASAwork/papers/NSS2006KalpanaOne.pdf

Joe Strout -- joe@...