Minimum crew size for early Mars landings.

louis · 2018-05-09 05:13:20

I think what needs to be done re GCR (cosmic rays etc) is fairly well established now. Water or hydrogen rich plastics need to be used and
spacesuits need to incorporate protective material.

https://www.nasa.gov/feature/goddard/re … on-on-mars

I think this is one of the reason why Musk has gone "big": it's much easier to construct a protective environment for the crew if you have a big spaceship. If necessary, Space X could sacrifice 50 tonnes to protective material on the BFS. But appropriate placement of water tanks in the design will help greatly.

SpaceNut wrote:

https://s3.amazonaws.com/images.spacere … 18_Web.pdf
page 20 Human Health Countermeasures Element (HHC)
lots of good stuff in the document
page 22 Exploration Medical Capability Element

GW Johnson · 2018-05-09 08:40:24

GCR in the inner solar system runs roughly sinusoidally between 24 and 60 REM per year, varying with the 11 year sunspot cycle. It seems to be modulated by the strength of the solar wind, and reduced when the sun is stormy.

NASA astronaut exposure rules are about twice what a nuclear worker can be exposed to. There is a 50 REM in any one year limit, a 25 REM in any one month limit, and a career limit that varies with age and gender, but approaches 400 accumulated REM as the ultimate limit in all cases.

Given that spacecraft structures will provide at least some shielding effect, and could provide quite a bit more if water and propellant were used judiciously as shielding, something like 50 REM per year is achievable in a 60 REM/year year. In an off year, it's under 24 REM, nearer 20 REM.

GCR is not the bugaboo threat! Solar flare events are. This is short bursts of massive floods of much lower-energy radiation, of exactly the type we know how to shield. These are rather comparable to being outside in the first few hours after a surface burst with a small fission bomb. Lethal dose in minutes to an hour. Solar flares vary all over the map. But 10's of 1000's of REM per hour have been measured.

Solar flare radiation is shieldable by something like 20 cm water or equivalent. Again, judicious placement of water and propellant tanks can act as very effective shielding. But you cannot do this in an Apollo-like vehicle, not even Apollo-on-steroids Orion.

Bigelow's layers of fabric of relatively-low-weight atoms is about 0.5 m thick on its B-330 design, said to be twice as shielding in its effect as the tuna can modules from which ISS is made. That's not enough for a solar flare event out in deep space, both were intended to be shielded from the solar winds by Earth's magnetosphere.

You have to add a shelter to your spacecraft design, and some sort of warning that an event has occurred. Seeing the counters go up sharply is likely too late, unless you can reach the shelter in scant seconds.

Again, one way around that might be to cluster propellant tanks and water tanks around the designated shelter space. This sort of design bears no resemblance at all to Apollo-Saturn (or SLS-Orion) technology. It is far easier to implement for an orbit-to-orbit transport that is recovered and reused many times, never itself landing.

GW

Last edited by GW Johnson (2018-05-09 08:43:54)

louis · 2018-05-09 14:01:00

Might make sense to make the sleep areas the emergency shelters as well, rather than double up on volume.

GW Johnson wrote:

GCR in the inner solar system runs roughly sinusoidally between 24 and 60 REM per year, varying with the 11 year sunspot cycle. It seems to be modulated by the strength of the solar wind, and reduced when the sun is stormy.
NASA astronaut exposure rules are about twice what a nuclear worker can be exposed to. There is a 50 REM in any one year limit, a 25 REM in any one month limit, and a career limit that varies with age and gender, but approaches 400 accumulated REM as the ultimate limit in all cases.
Given that spacecraft structures will provide at least some shielding effect, and could provide quite a bit more if water and propellant were used judiciously as shielding, something like 50 REM per year is achievable in a 60 REM/year year. In an off year, it's under 24 REM, nearer 20 REM.
GCR is not the bugaboo threat! Solar flare events are. This is short bursts of massive floods of much lower-energy radiation, of exactly the type we know how to shield. These are rather comparable to being outside in the first few hours after a surface burst with a small fission bomb. Lethal dose in minutes to an hour. Solar flares vary all over the map. But 10's of 1000's of REM per hour have been measured.
Solar flare radiation is shieldable by something like 20 cm water or equivalent. Again, judicious placement of water and propellant tanks can act as very effective shielding. But you cannot do this in an Apollo-like vehicle, not even Apollo-on-steroids Orion.
Bigelow's layers of fabric of relatively-low-weight atoms is about 0.5 m thick on its B-330 design, said to be twice as shielding in its effect as the tuna can modules from which ISS is made. That's not enough for a solar flare event out in deep space, both were intended to be shielded from the solar winds by Earth's magnetosphere.
You have to add a shelter to your spacecraft design, and some sort of warning that an event has occurred. Seeing the counters go up sharply is likely too late, unless you can reach the shelter in scant seconds.
Again, one way around that might be to cluster propellant tanks and water tanks around the designated shelter space. This sort of design bears no resemblance at all to Apollo-Saturn (or SLS-Orion) technology. It is far easier to implement for an orbit-to-orbit transport that is recovered and reused many times, never itself landing.
GW

SpaceNut · 2018-05-09 16:43:27

None of the proposed are part of any design information as far as I know for transit to mars and back; not for Nasa and not in the BFR....Remember the moon is only a few days away so Nasa would not even want to lug around extra mass so the same would be true of the BFR. So layered protection like the Bigelow inflateables walls as structure is away to not increase mass for protection..

louis · 2018-05-09 16:47:22

Just a guess, but I think radiation protection will be taken v. seriously on the human BFS and that is one of the reasons there are going to be three other BFS cargo ships.

SpaceNut wrote:

None of the proposed are part of any design information as far as I know for transit to mars and back; not for Nasa and not in the BFR....Remember the moon is only a few days away so Nasa would not even want to lug around extra mass so the same would be true of the BFR. So layered protection like the Bigelow inflateables walls as structure is away to not increase mass for protection..

GW Johnson · 2018-05-11 10:04:25

Outside Earth's magnetosphere there is no protection from solar flare radiation, and not around or on the moon, either. The way NASA got away with no radiation protection on Apollo was by playing the odds. With a mission max of 2 weeks, it was more-or-less unlikely for an Apollo mission to the moon to be hit by flare radiation.

However, it was not as unlikely as they had hoped. Right between two Apollo flights to the moon, a flare struck in 1972 that would have killed any crew outside low Earth orbit within hours at most. Sudden, massive, lethal radiation poisoning is a very ugly death. Uncontrollable vomiting and nausea, bleeding from everywhere, skin falling apart into lesions, total physical incapacitation. Unrelievable, untreatable misery until death puts an end to it.

Now, for a return to the moon, you are looking at missions measured in months, not days. You cannot play the odds with respect to flare radiation, you WILL be hit by it. Sooner or later. For NASA and its favored contractors to continue to ignore flare radiation protection is one of those totally brain-dead, "dry empty skull" problems.

SpaceNut · 2018-05-11 18:36:00

post 3 & 4 of http://newmars.com/forums/viewtopic.php?id=7895

we did talk about some of the issue but If I recall orion was to have an rf energy static generated megnetosphere shield.

again in this topics first page http://newmars.com/forums/viewtopic.php?id=7199

SpaceNut · 2019-10-24 18:51:36

If we are in a holding pattern then why not solve for the small core of a 2 man mission if thats going to light a fire under nasa and others to get going to mars for real...

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#26 2018-05-09 05:13:20

Re: Minimum crew size for early Mars landings.

#27 2018-05-09 08:40:24

Re: Minimum crew size for early Mars landings.

#28 2018-05-09 14:01:00

Re: Minimum crew size for early Mars landings.

#29 2018-05-09 16:43:27

Re: Minimum crew size for early Mars landings.

#30 2018-05-09 16:47:22

Re: Minimum crew size for early Mars landings.

#31 2018-05-11 10:04:25

Re: Minimum crew size for early Mars landings.

#32 2018-05-11 18:36:00

Re: Minimum crew size for early Mars landings.

#33 2019-10-24 18:51:36

Re: Minimum crew size for early Mars landings.

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