shielding

From: George Perkins [mailto:spacework@...]

I'm interested in repair-able mobile colonies of a size that's good
for the life it contains. But I am speaking for all habitats really
as what I wrote is applicable, I would guess, to most any that's
expected to survive in space for the long term.

If you're speaking about habitats that provide a good life for the life
contained, or all habitats, then we're talking about O'Neill's vision.

Even a small craft
needn't be completely covered with the same amount of shielding

Certainly not. Especially since probably no one would live the rest of
their life in a small craft.

- it
depends on what you're shielding and how long you must shield it and
if there is any way you can reduce this shielding to save on energy
and resources.

If we're talking about a mobile habitat, then I agree with you that anything
which reduced the overall mass of the habitat by 80-90% would definitely
save you a bunch of thrust. For a non-mobile habitat, this would be less of
an issue. And in neither case would I worry about the shield being a waste
of resources. It's planned to make it out of the slag which will inevitably
result from the ore-refining process, so it will use material which will be
created anyway, and would have to be disposed of somehow if there were no
use for it.

I'm not interested in O'Neill's visions.. I have
enough of my own to wrestle with, if you don't mind.

So you want to go your own way. That's fine. But since what you're talking
about is so close to what O'Neill talked about, it may be inadvisable to
disregard the technical solutions he and several others arrived at after
much careful research.

One can also waste time re-inventing the wheel when choosing to disregard
previous proposals. I remember one fellow who independently re-invented
chevron shields and banded toruses. It's always nice to see independent
researchers come to the same solutions, but it was a bit of a waste of time
on his part to invent something in the year 2000 which was written about
quite extensively in the mid-1970's.

Yes. Normal space radiation consists of cosmic radiation.. I was
refering to serious storms of radiation that come and go, as far as a
shelter is needed to be employed. We have shelters to protect us
from the big stuff.. not the ever-present.

No, you were correct the first time when you said that we need 1-2 feet
thickness of shielding for "normal space radiation" (which we may choose to
define in a way which excludes heavy nuclei), but a much greater thickness
for cosmic rays and solar flare transients. Since cosmic rays are there all
the time, we need the 6-foot thickness if we want to talk about people
spending their lifetimes there.

>

No. You misunderstand. The shelter is for the transient serious
radiation we pass through, including solar flares.

Why do you say I misunderstand? I understood the shelter to be a flare
shelter, and I think I posted to that effect.

With less weight it's more easy to move out of the way of a shower of
rocks heading for your habitat.. plus you save the kids in the
process.

I can only assume that you haven't read "The High Frontier" (perhaps a good
idea for someone working on designs of mobile space habitats of a size
sufficient to provide a good life). In it O'Neill comments that even the
largest model, Island Three, might have to wait a million years for a
one-ton meteoroid to impact, and even that may not completely destroy the
habitat. Island Three could expect to be hit by a meteoroid the weight of a
tennis ball roughly every three years. Even if the meteoroid threat were
much greater than it is, I would question our ability to move an enormous
habitat out of the way of rocks coming in at several miles per second, even
sans shielding.

Between cosmic rays and meteoroids, the cosmic rays are the far more
insidious threat to life in space.

You should be more protective of the children and less loyal to
pasting two meters of heavy concrete everywhere.

My loyalty is to neither concrete or slag. It's to having babies with no
greater incidence of birth defects than is the case on Earth. It's to
having long-term residence with no greater incidence of cancers than is the
case on Earth. Nothing will accomplish that short of reducing radiation
levels to those found here on Earth. Nothing will accomplish that passively
short of around 6-feet of shielding.

An unfortunate fact, at least from the point of view of applying a thrust to
change the orbit of a space habitat, but we have to take the situation as it
is.

Regards,

Mike Combs

From:
George Perkins [mailto:spacework@...]
I'm interested in repair-able mobile colonies of a size that's good
for the life it contains. But I am speaking for all habitats really
as what I wrote is applicable, I would guess, to most any that's
expected to survive in space for the long term.

If you're speaking about habitats that provide a good life for the life contained, or all habitats, then we're talking about O'Neill's vision.

Even a small craft
needn't be completely covered with the same amount of shielding

Certainly not. Especially since probably no one would live the rest of their life in a small craft.

- it
depends on what you're shielding and how long you must shield it and
if there is any way you can reduce this shielding to save on energy
and resources.

If we're talking about a mobile habitat, then I agree with you that anything which reduced the overall mass of the habitat by 80-90% would definitely save you a bunch of thrust. For a non-mobile habitat, this would be less of an issue. And in neither case would I worry about the shield being a waste of resources. It's planned to make it out of the slag which will inevitably result from the ore-refining process, so it will use material which will be created anyway, and would have to be disposed of somehow if there were no use for it.

I'm not interested in O'Neill's visions.. I have
enough of my own to wrestle with, if you don't mind.

So you want to go your own way. That's fine. But since what you're talking about is so close to what O'Neill talked about, it may be inadvisable to disregard the technical solutions he and several others arrived at after much careful research.

One can also waste time re-inventing the wheel when choosing to disregard previous proposals. I remember one fellow who independently re-invented chevron shields and banded toruses. It's always nice to see independent researchers come to the same solutions, but it was a bit of a waste of time on his part to invent something in the year 2000 which was written about quite extensively in the mid-1970's.
Yes. Normal space radiation consists of cosmic radiation.. I was
refering to serious storms of radiation that come and go, as far as a
shelter is needed to be employed. We have shelters to protect us
from the big stuff.. not the ever-present.

No, you were correct the first time when you said that we need 1-2 feet thickness of shielding for "normal space radiation" (which we may choose to define in a way which excludes heavy nuclei), but a much greater thickness for cosmic rays and solar flare transients. Since cosmic rays are there all the time, we need the 6-foot thickness if we want to talk about people spending their lifetimes there.
>
No. You misunderstand. The shelter is for the transient serious
radiation we pass through, including solar flares.

Why do you say I misunderstand? I understood the shelter to be a flare shelter, and I think I posted to that effect.
With less weight it's more easy to move out of the way of a shower of
rocks heading for your habitat.. plus you save the kids in the
process.

I can only assume that you haven't read "The High Frontier" (perhaps a good idea for someone working on designs of mobile space habitats of a size sufficient to provide a good life). In it O'Neill comments that even the largest model, Island Three, might have to wait a million years for a one-ton meteoroid to impact, and even that may not completely destroy the habitat. Island Three could expect to be hit by a meteoroid the weight of a tennis ball roughly every three years. Even if the meteoroid threat were much greater than it is, I would question our ability to move an enormous habitat out of the way of rocks coming in at several miles per second, even sans shielding.

Between cosmic rays and meteoroids, the cosmic rays are the far more insidious threat to life in space.
You should be more protective of the children and less loyal to
pasting two meters of heavy concrete everywhere.

My loyalty is to neither concrete or slag. It's to having babies with no greater incidence of birth defects than is the case on Earth. It's to having long-term residence with no greater incidence of cancers than is the case on Earth. Nothing will accomplish that short of reducing radiation levels to those found here on Earth. Nothing will accomplish that passively short of around 6-feet of shielding.

An unfortunate fact, at least from the point of view of applying a thrust to change the orbit of a space habitat, but we have to take the situation as it is.

Regards,
Mike Combs