Moonwards

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6:27 PM

Q: Is radiation dose from cosmic rays higher behind 50 cm of shielding, or lower?

I have seen it said that because high-energy GCR particles cause a spray of secondary particles when they pass through material, there is more radiation behind even quite thick shielding that there is if there is no shielding at all. A paper by Vanessa Aulessa was used to produce the graph below ...

i thought i'd sorted this out, but i got into a discussion with someone about it, and sadly we are both equally unable to assess the truth

Hohmannfan

6:43 PM

Extremely relevant for any design. This must be sorted out.

Hohmannfan

6:54 PM

@kimholder You are accepting answers of only about half of your questions. Any reason for that?

kim holder

it's for one of two reasons, depending on the question: there is no answer that i feel is complete or authoritative enough to be accepted, or there is more than one answer that has a lot of merit.

Hohmannfan

I can understand the first reason, but not the second one.

kim holder

i tend to ask questions that are a little on the open-ended side, so often it really can't be answered in a way where it would be reasonable to send the message 'there, this is the answer'.

because so many of my questions are like that, on those i only accept an answer if it has really covered all the ground very well, and that usually doesn't happen

in those cases, i really think upvotes sort answers much better

Hohmannfan

So accept the must upvoted one then :)

As far as I can see, you are the only high rep user doing this (except Mark, but he never asks questions)

kim holder

i think that sends the wrong message

by not accepting an answer, i am sort of saying 'read them all'

Hohmannfan

7:02 PM

Or telling people 'non of them are good enough'. It is impossible to distinguish that from the first reason.

But yeah, I am not saying you are wrong. I just noticed this when I filtered through some site data.

kim holder

actually, there are a bunch of cases where i don't think any answer is good enough to get the check mark

but, even if people wonder if i think no answer is good enough, i think they are more likely to read them all if none is accepted

Hohmannfan

So you want people reading bad answers :P

kim holder

[squint] you are the person who's the tough audience here

undermining all my explanations and all

Hohmannfan

It is just a minor side effect of physics overload, I have reached transcendence.

oh, like the movie?

7:10 PM

Never heard about it.

kim holder

he was turned into a computer. didn't go well.

Hohmannfan

noooooooo

kim holder

do you still have to write the physics uber-exam?

Hohmannfan

7:13 PM

The national contest is this week.

kim holder

i thought i remembered something like that

do you have to / get to travel again?

Hohmannfan

I am in Oslo at the moment

kim holder

oh, cool.

Hohmannfan

I am more inclined to believe the figures of marsjournal.org/contents/2006/0004/files/… it has so much more data.

"An astronaut on the surface of
the Moon is protected from the GCR environment in 2
π
directions by the lunar regolith. However, there are low
energy neutrons and light ions produced as a result of
interaction between the galactic cosmic rays and the lunar
regolith that make a small contribution to astronaut dose. For
these reasons, the radiation environment on the lunar surface
is slightly more than half as intense as that of free space."

Also, have you seen this? :

researchgate.net/profile/Mark_Anderson7/publication/…

kim holder

i recall puzzling over this a long time ago, and i think from somewhere i got the impression that the versions that only tail off are not considering the high-energy particles

yes, i was looking at that a little while ago. i almost included it in the question.

but most of it doesn't seem relevant

sites.nationalacademies.org/cs/groups/depssite/documents/…

that one is good too. it talks about the tools used to do the analysis

oltaris.nasa.gov

that is a tool you can sign up for to do an analysis of this kind of thing, but it seemed much better to seek clarity from someone who is really an expert.

i spent most of the morning looking into it. i was in a string of email exchanges that started off being about Zubrin's latest Mars statement, and veered in this direction.

Hohmannfan

7:33 PM

Ah, email:

kim holder

so now i have to sort it out. yeah, unfortunately, i don't know that i should send that to any of the people who were in the thread

i don't know them that well, and they aren't in that area, although several of them are engineers

i have to admit, when i saw the argument that the risk was so much lower, i brushed it off because there didn't seem to be any way, in my mind, that there could be two such wildly different results

when i finally checked the source, it was a legitimate issue. this is what happens when people don't put proper inline citations :P

kim holder

8:37 PM

i am keeping quiet in part because i think you should be experiencing Oslo, not talking to me. not even about cosmic radiation.

ok, i'm not keeping all that quiet, i just wanted to say i think that is important.

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