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#51 2018-10-05 04:10:53

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Radiation amount type risk mitigation

Depends if you view the protection as structure or, effectively, cargo/payload along with the humans. I don't think protection has to be built into the hull. It could be fitted internally as plastic mass fitted behind panelling.

SpaceNut wrote:

We know the type, the durations, the amounts and even what materials to make use of but its the final design with materials that are not added mass for protection that hold the key to a long duration mission for man. We need to not trade a payload mass when its just not going to work to protect man.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#52 2018-10-05 10:08:39

Oldfart1939
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Registered: 2016-11-26
Posts: 2,306

Re: Radiation amount type risk mitigation

About a year or so ago, I was still designing something of a minimalist mission based on what the Falcon Heavy might (with some upgrades and modifications) be able to do with an enlarged and lengthened Dragon 2 system. My design incorporated sleeping "cocoons," for the astronauts which would conceivably be individual radiation shelters from Solar flare events. Any crew we send would undoubtedly be on rotating shifts or watches. Let's hypothesize that at any time 1/3 would be sacked out. The interior of my model incorporated large quantities of LPE (Linear Polyethyene) as structural material for the bunks with water storage tanks/food storage bins incorporated in the designs. There is really no "piloting" of a coasting spacecraft, but chores of food preparation and science experiments keep the idle hands busy. My other concept was incorporation of food storage bins within the external wall structures. This would be the Mars existence/survival food, such as massive quantities of legumes (beans, dried split peas), and grains (whole wheat, barley, rice, etc.). There could also be water tanks for Mars use, not in-transit consumption. Given space limitations, we can never really zero out the Solar Flare radiation, but only attenuate it to survivable levels.

Last edited by Oldfart1939 (2018-10-05 10:10:05)

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#53 2018-10-05 10:28:14

Oldfart1939
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Registered: 2016-11-26
Posts: 2,306

Re: Radiation amount type risk mitigation

Based on GW's suggested thickness for a water layer of 15 cm, I calculated a shelter within the BFS being a cylinder of meters diameter and 4 meters long. This would require roughly 6 Tonnes of H2O. A very reasonable amount of water being 6,000 liters. Rounding this off is 1,600 gallons. This water would not be consumable during travel, but available for on Mars usage. This could conceivable be reduced by residual fuel in the tankage.

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#54 2018-10-05 11:51:52

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,952
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Re: Radiation amount type risk mitigation

I'd use 15-20 cm of "water-equivalent" in a shadow shield,  made up of stuff you already have to have anyway,  such as propellant for the next burn,  water,  and wastewater (and maybe frozen food).  I just posted another radiation article on "exrocketman today (10-5-18) as "Space Radiation Risks:  GCR vs SFE".  It supersedes the one I posted in 2012,  but uses the same source data. 

In that posting,  I've got timeline plots of absorbed radiation dose for a 31-month Mars mission,  for a design with only a solar flare shelter,  and for a design with that plus shielding about the sleeping quarters.  It's even better if the whole habitable space in the spacecraft can be shielded.  All the numbers are there,  including exactly how I got them and used them. It is quite clear that solar flare events,  not GCR,  are the lethal threat.  Not all of them,  just the big ones. 

There's one concept sketch in my new posting of how to make a shadow shield out of conformal tanks of storable propellants docked about the periphery of the habitable volume of a long spacecraft design.  The gaps between the tanks get shadow-shielded inside the spacecraft pressure hull by the life support-associated water and wastewater plumbing,  plus any frozen food stores. 

This adds little or no dedicated shielding mass to the ship's design,  using instead stuff you already have to have,  anyway.  It is further quite compatible with a long ship configuration that could be spun end-over-end for artificial gravity. 

What all this goes to prove is that a ship design that properly addresses radiation risks in deep space will look nothing at all like anything we have ever done before.  Same is true of spin gravity.  Yet,  these are things that require no new technology demonstration and validation,  only verification testing of real hardware that we can design right now.  So when folks present designs that look like what we did in decades past,  you already know they have not thought these issues through.  That's true for returning to the moon as well as going to Mars. 

My radiation exposure figures also reveal exactly why the "scare literature" about GCR precluding manned deep space flight is utter nonsense.  It is so patently obvious that large SFE events are the real lethal threat,  and that the GCR scare literature is just pathetic (and ignorant) nonsense. 

GW

Last edited by GW Johnson (2018-10-05 11:57:32)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#55 2018-10-05 13:26:54

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

louis wrote:

Depends if you view the protection as structure or, effectively, cargo/payload along with the humans. I don't think protection has to be built into the hull. It could be fitted internally as plastic mass fitted behind panelling.

SpaceNut wrote:

We know the type, the durations, the amounts and even what materials to make use of but its the final design with materials that are not added mass for protection that hold the key to a long duration mission for man. We need to not trade a payload mass when its just not going to work to protect man.

Oldfart1939 & GW Johnson have given the what we do when adding materials for an intended purpose which is the second function of the material use. The outer hydrogenated plastic tank that holds water for the shield does cut into the payload as the water can not be used with the remaining will only be in place while the food is not eaten. So that is the same problem payload reduction to keep it in place for the total journey..

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#56 2018-10-07 04:01:03

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: Radiation amount type risk mitigation

Most water will be recycled. Mission designs will go to some lengths to ensure this. Therefore the  shielding tanks can be kept completely full at the expense of  separate consumable tanks, which will be run down over the mission duration, to cover for any losses of water.

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#57 2018-10-07 08:55:20

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

The blatter would need to be made so that it could not leak or be punchered, temperature control to remove risk from the crew area which would add structure and mass beyond the mass of the water to have the permanent water shield. Now to minimize this shrinks its size, mass for the purpose and location within the ship that it can be made in.

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#58 2019-07-21 15:18:27

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

We did not take any risk to going back to the moon but why are we dragging our heals...

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#59 2019-07-31 08:36:54

tahanson43206
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Registered: 2018-04-27
Posts: 12,008

Re: Radiation amount type risk mitigation

While selecting books for a college freshman, I remembered T.A. Heppenheimer "Colonies in Space'.

Used copies are still available, and even a few "new" copies are advertised.

I took a look at the copy that just arrived, and realized I'd forgotten much of the content.

In particular, for this topic, I found a thorough discussion of radiation dangers and possible countermeasures on page 223 of the small paperback.

In another topic, I had wondered about using electrostatic force to repel positively charged nuclei of atoms.  Heppenheimer confirms that would work, if the voltage is set to 10 billion volts (page 227). However (page 228) Heppenheimer goes on to clarify that while the positively charged particles would be repelled, the electrons would be accelerated toward the location, and upon arrival they would generate X-Rays.

As has been true for decades, Heppenheimer then settles on a layer of matter to absorb radiation.  Page 229 offers 6 feet of lunar soil as a reasonable amount.

The copy I have in hand is copywrite 1977.  It is fun seeing this old friend once again.

It seems to be holding up fairly well, everything considered.

(th)

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#60 2019-07-31 17:56:26

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

The knowledge is that we have still not solved the issue of radiation mitigation but some will say go without it and see what happens as they Astronauts to go will accept the risk even when knowing its out come as the Apollo crews did.

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#61 2019-08-01 11:18:34

tahanson43206
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Registered: 2018-04-27
Posts: 12,008

Re: Radiation amount type risk mitigation

For SpaceNut re #60 ...

Following up on post #59 about an electrostatic shield, as discussed in T.A. Heppenheimer ...

After thinking about the issue overnight, it occurred to me that at the time of publication of "Colonies in Space" (1977) Heppenheimer recorded the conclusion of the community that was active at the time.  2019 - 1977 >> 23 + 19 >> 42 years have gone by, and surely later thinkers have explored this topic.

The positively charged outer shell Heppenheimer described would (in his report) repel positively charged atom nuclei, if the charge level is about a billion volts.

He argues that electrons would be attracted to this shield.

Surely someone has thought about creating an inner shell that is negatively charged, to balance the charge of the outer shell.

The vulnerable shelter for humans would reside inside this dual shell structure.

SpaceNut, in recognition of your search skills, please see if you can find the argument against this proposal.

It must surely exist, because otherwise we'd have heard about this concept, long ago.

Not too long ago, in this forum, (as I recall) there was discussion of a concept for solar sailing using charged grids.

Edit: There's a lengthy discussion of billion volt speculations in a forum with a science orientation.  The majority of the posts were about lightning, and there was one post about Benjamin Franklin's work with lightning.  I had not previously read that he used copper cylinders and steel balls in an apparatus to investigate lightning.  He charged the cylinders with lightning (according to the post) and then got a satisfying discharge between the steel balls.

There must be a report of that experiment somewhere, because the poster remembered it (assuming it was true, and the memory was accurate).

However, it certainly sounds plausible, from what I've read about Franklin.

(th)

Last edited by tahanson43206 (2019-08-01 11:47:11)

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#62 2019-08-01 16:54:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

Here is what I posted in another topic:
This is a radiational shield created by magnetics....

https://medium.com/the-physics-arxiv-bl … ba6bfdf65d

1*pDybSxlxPQNRiCF7EFIh0A.png

1*6DoghdImxTLv2hR01wqPKg.png


Galactic cosmic rays (GCRs) consist of high energy protons (85%), helium (14%) and other high energy nuclei (HZE ions).

PIA17601-Comparisons-RadiationExposure-MarsTrip-20131209.png

http://www.buildtheenterprise.org/shielding

radiation-space-danger-130529b-02.jpg?interpolation=lanczos-none&downsize=600:*

Artificial Magnetosphere - Electromagnetic Induction

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#63 2020-01-12 20:28:30

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

https://www.nasa.gov/sites/default/file … 6-ADD2.pdf
Mars Design Reference Architecture 5.0 – Addendum #2

pg 490
lots of items and what happens for mans trip to mars

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#64 2020-01-20 19:38:38

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

Finally NASA-funded space radiation studies could save astronauts' lives

awarded a $550,000 grant to the Florida Institute of Technology in Melbourne to begin the three-year machine learning project next month.

Florida Tech is one of 14 universities NASA picked in November for funding to study an array of topics under the agency's Space Technology Research Grants program.

Other schools awarded funding are Rensselaer Polytechnic Institute, Troy, N.Y.; Purdue University, West Lafayette, Ind.; Auburn University, Auburn, Ala.; the University of Michigan, Ann Arbor; the University of Alabama-Tuscaloosa, and the University of California-Los Angeles.

Also, the University of Central Florida, Orlando; Florida State University, Tallahassee; University of Texas, El Paso; University of Illinois-Urbana-Champaign; New Jersey Institute of Technology, Newark, and Vanderbilt University, Nashville.

https://www.nasa.gov/hrp/elements/radiation

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#65 2020-05-13 07:24:32

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

Study suggests polymer composite could serve as lighter, non-toxic radiation shielding

We have known for a while that plastics made with a high hydrogen ration did help in the radiation shielding.

The bismuth trioxide compound is lightweight, effective at shielding against ionizing radiation such as gamma rays, and can be manufactured quickly - making it a promising material for use in applications such as space exploration, medical imaging and radiation therapy.

"Traditional radiation shielding materials, like lead, are often expensive, heavy and toxic to human health and the environment,"
"This proof-of-concept study shows that a bismuth trioxide compound could serve as effective radiation shielding, while mitigating the drawbacks associated with traditional shielding materials."

https://dx.doi.org/10.1016/j.net.2020.04.026

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#66 2022-04-09 16:04:51

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,753

Re: Radiation amount type risk mitigation

bump

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#67 2022-06-06 06:01:26

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 2,218

Re: Radiation amount type risk mitigation

Cosmic ray doserates at Gale Crater and similar low lying regions, average to about 250 micro-Sv per day.
http://planetary-science.org/wp-content … t-al-1.pdf

This works out at 91mSv per year.  It is estinated that 1Sv whole body dose raises mortality risk by 5%.  If we assume that on average a radiation induced mortality results in 30 years lost life expectancy, then exposure to 1 year of Mars surface dose, results in 50 days loss of life expectancy.  Exposure for fifty years would reduce life expectancy by 6.8 years.  Other health factors not withstanding, this suggests that life expectancy woukd be measurably reduced if humans were to spend 100% of time exposed to Mars surface radiation levels.

We can compare this to air pollution on Earth.  The average Chinese loses about five years of life expectancy due to air pollution.  So if we provided no cosmic ray shielding at all on Mars, the health impact would be comparable to air pollution in China.  That is a severe enough problem that mitigation deserves considedatiin and long term habitation should be shielded, especially given that it is relatively easy to do.

For early construction on Mars, living in unshielded structures within inflatable domes would not raise catastrophic risks.  If one spent ten years living and working in an unshielded structure, loss of life expectancy would be about 1 year, which is in with stastical noise for most people.  Likewise, if some time is spent in shielded areas and some time outside, then overall risk begins to look more acceptable.  If humans spend two-thirds of time in shielded structures and one third of time exposed to ambient cosmic dose, then total lifetime LLE is reduced to a little over two years, which is comparable to other common environmental hazards on Earth.  If a man spent 40 hours a week onnthe Martian surface, 50 weeks a year, for a 40 year career, then LLE woukd be 1.25 years.  That about the same as being exposed to air pollution in any urban area in the developed world.  There are many hundreds of millions of people that willingly do this.

So whilst we need to be mindful of radiation exposure on Mars, not all structures will need to be shielded.  Even if exposed to ambient Mars surface radiation for a significant fraction of time, it is unlikely that Martian life expectancy would be significantly reduced compared to Earth.  On the moon or in free space, the situation may be markedly different.

Last edited by Calliban (2022-06-06 06:46:48)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#68 2022-06-06 14:39:11

kbd512
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Registered: 2015-01-02
Posts: 6,228

Re: Radiation amount type risk mitigation

I think it's grossly unreasonable to expect no increase in exposure to radiation, but it's also grossly unrealistic to think that a slight elevation in radiation exposure is equivalent to living a shorter life.  There were plenty of people who were as near as they could be to ground zero at either Hiroshima and Nagasaki, without being incinerated or turned into jello from the blast over-pressure wave, who lived longer than people who had poor diets during the economic growth that followed WWII.

There are plenty of immediately fatal problems to contend with on Mars that have a much greater likelihood of reducing total life expectancy, as compared to notable but not dramatic increased radiation dose rates relative to Earth sea level.  Moreover, we already have simple and highly effective ways of dealing with increased radiation levels.

So...  Is radiation a problem?  Yes, but relative to all other problems it's more of an annoyance than a showstopper.  Short of remaining completely unprotected during a very powerful solar storm, you'd have to deliberately work at injuring or killing yourself via radiation exposure while living on the surface of Mars.  I don't think radiation makes the Top 10 List, with respect to the ways you're most likely to die or be seriously injured on Mars.  On the moon, radiation from solar storms might break into that list, but such events are (thankfully) pretty rare.  It's a non-zero risk that our rovers have quantified over the years, but we should accept that the mitigation strategies actually work and then move on to much more pressing problems.

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#69 2022-08-26 07:14:08

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 4,782

Re: Radiation amount type risk mitigation

Life on Mars? Estimating Radiation Risks for Martian Astronauts

https://eos.org/editor-highlights/life- … astronauts

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#70 2022-08-26 08:51:49

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,952
Website

Re: Radiation amount type risk mitigation

What gets lost in all these opinions about radiation is that there are two sources,  not one.  Cosmic radiation is a very slow drizzle of extremely high-energy particles that are thus very difficult to shield against,  no matter what approach you use for shielding.  These are the ones that have the most secondary scatter effects on higher-atomic weight passive shielding materials.  But the dose rate in our vicinity in the solar system is really quite low,  at about 60 REM per year when the solar wind is weaker,  and 24 REM per year when the solar wind is stronger.  NASA astronaut exposure standards call for no more than 50 REM per year.  With a bit of shielding,  you are OK,  just more shielding than a thin aluminum spacecraft shell. LD50 is about 300 REM in a short time,  and LD100 is about 500 REM in a short time. 

edit update 8-29-2022:  I misquoted the GCR exposures as milliREM which I have now corrected to REM.  100 REM = 1 Sievert,  for you metric guys.  Note that 50 REM over a year is not actually more than a 3% increase in cancer late in life.  50 REM in a "short" time, is the the monthly accumulated exposure limit in NASA's old standards.  That's well below any lethal dose,  but it might make you a bit sick after that month.  50 REM over hours or days will make you very,  very ill.  NASA old astronaut exposure standards were set at about twice those used for Earthly nuclear workers.

The other source is the erratically-occurring flood of lower-energy particles from the sun.  There is always some of this,  it's called the solar wind,  and it gets caught and concentrated as the radiation belts about Earth and some other planets.  But solar flares release a huge flood of these.  Synonyms include "coronal mass ejections",  but it's just an eruption from the sun.  Some are bigger than others  There are more of them when sunspot activity is high,  but they can occur at any time.  The worst of these you can shield fairly effectively with 15-20 cm of water,  or any other low molecular weight materials (to reduce secondary scatter effects).  The criterion NASA uses for this is whatever thickness gets you 15-20 g/cm2 of shielding material. 

These floods of solar particles are the lethal threat.  They are actually rather similar to,  and as lethal as,  the initial fallout from a nuclear ground burst close by.  Shielding against these is simply required for operations outside Earth's magnetic field or within its Van Allen radiation belts.  That is because sooner or later,  one of these will hit you.  It is only statistics that this will occur.  The longer you are out there,  the more likely you will be hit. 

Apollo ignored this,  and got away with it,  because the missions were only 10 days to 2 weeks long.  But the biggest radiation event we have ever seen hit between Apollo 16 and Apollo 17 in 1972.  Had a crew been out there when it hit,  they would have died within hours,  the same way you die within hours standing outside in nuclear fallout.  We're talking about 10,000 to 30,000 REM in a short time,  with events like that.  But that 15-20 g/cm2 of passive shielding cuts it to tolerable levels,  PRECISELY BECAUSE lower-energy particles are far easier to shield against. 

Update 8-29-2022:  The old NASA exposure standards claimed that Apollo's hull cut flare radiation exposures by about a factor of 10.  What was 5000 REM outside was about 500 REM inside,  estimated for the 1972 event.  Since this accumulates over hours to at most a couple of days,  that's "short",  and therefore still a lethal dose for essentially 100% of those so exposed. 

THAT picture is what you have to deal with,  for humans leaving LEO!  And NASA's Gateway station about the moon does NOT deal with it.  If they don't add some shielding,  then they will eventually kill a crew aboard it.  Mark my words!   Bigelow's meter of fabric insulation that was in its B-330 design would go a long way toward being the shield that is needed.

Update 8-29-2022:  the old NASA exposure standards are still on the internet at

http://srag.jsc.nasa.gov/Publications/T … chmemo.htm, titled Spaceflight Radiation Health Program at JSC. 

Go look at this thing for yourself. The newest reference in its reference list is dated 1993.  There is no date on the document as published on the internet.  This includes shuttle data,  but it predates ISS data.  It does project exposures for ISS,  that being one of its purposes.  As far as I know,  the actual ISS data are relatively in-line with these predictions. 

GW

Last edited by GW Johnson (2022-08-31 13:57:49)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#71 2022-08-28 06:29:02

Mars_B4_Moon
Member
Registered: 2006-03-23
Posts: 4,782

Re: Radiation amount type risk mitigation

ESA astronaut rad-detectors on Artemis

https://www.spacedaily.com/reports/ESA_ … s_999.html

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#72 2022-08-28 12:27:04

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,952
Website

Re: Radiation amount type risk mitigation

There's just enough cosmic ray radiation to worry about cancer late in life.  The lethal danger is the erratic occurrence of the odd high-energy solar flare that actually hits you. 

There's been no secret about this.  This stuff has been known and well-measured since the late 1960's early 1970's.  The ESA detectors on Artemis maty or may not see a flare,  but might add detail about the nature of the already-known cosmic ray issue.  If they see a flare,  they may well saturate without getting good data,  since the disparity is so large. 

Spacecraft hulls to date only offer minimal shielding effects.  Orion is no different.  Neither will be Gateway.  Same for Musk and his Starship (we have seen nothing yet about the purported presence of a "radiation shelter" in his design).  They're gonna kill a crew,  sooner or later,  by not planning for a direct hit by a huge flare event.  Simple as that.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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