Radiation Fatigue?

From: "victoriatangoman"
To:
Sent: Friday, July 19, 2002 12:08 PM
Subject: [spacesettlers] Radiation Fatigue?

> What effect will radiation have on the structure of the habitat?
>
> Consider that space vehicles degrade in performance as a function of
> time the radiation they receive.
>

Ok, but this performance degrade is due to the impact of radiation in
electronics (I think), not structure.

> Will the habitat need to be maintained like a ship (40 years between
> major overhauls or scrapping) or an airplane (also about 40 years
> before metal fatigue necessitates structural replacement.)
>

I tend to think more of habitats made of concrete or (in the case of very
large ones) "unobtanium" (carbon nanotubes or other supermaterial yet to
become popular) rather than metal. The classical argument favoring concrete
colonies are: (a) metal structures typically last decades, while
stone/concrete structures last centuries and (b) in case of decompression,
metal containers have a tendency to "pop", while concrete containers
preserve their shapes and the extension of fissures. Finally, on Earth at
least economics also favors concrete: the Petrona Towers, for instance, are
the tallest building in the world, but their construction cost was lower
than the WTC, because they are made of a new kind of "superconcrete". (If I
remember correctly.)

My gut feeling is that a metallic colony would need constant maintenance,
while a concrete one would be something to last "forever".

> What effect will the radiation in space have on the crystal bonds
> within the metal or concrete of the shell?
>

I really don't know. However, the gut feeling based on the little knowledge
that I have of chemistry/materials science tells me that crystal (ionic)
bonds tend to rearrange themselves, while covalent (molecular) bonds don't
get together again after disruption. Is my gut feeling wrong or right?

> Do you think that the shielding will degrade but that won't matter
> because it won't serve a structural function and the shell of the
> habitat will be protected by the shielding?
>

I tend to prefer designs where the shielding enveloped the whole colony
(including its structure) and does not rotate, or rotates at a much slower
speed. That decreases a little the structural requirements and also shields
the structure (not only against radiation, but also against impacts) as a
side effect.

> What does this say about designs that may want to incorporate the
> mass of shielding into the structure of the habitat rather than have
> it seperate?
>

I don't know, I have only the aforementioned gut feelings. ;-)

(...)
Lucio Coelho