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#80
by
joek
on 10 Nov, 2012 20:08
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Sounds like the makings of a good sci-fi story. Imagine if NASA actually did that and it backfired; the GCR didn't diminish their lifespan but instead hardened it so that the astronauts became all but immortal! Imagine the civilian pressure to get people into space for "hardening"! What a story that would make! 
A very interesting thought experiment. My own have trended more towards the question of the effects on our current view of spaceflight (and specifically exploration) if/when productive human lifetimes are extended...
Say your nominal or productive working life is extended to 100-200 years? How would that change our view, approach or strategy to space exploration, colonization (e.g., becoming a "space-faring species"), etc.
Seriosly OT, but I've often thought that advances in the biological and medical sciences may have a far more profound long term effect on our space exploration strategy than advanced propulsion systems, BFR's, etc.
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#81
by
daveklingler
on 10 Nov, 2012 20:19
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I'm thinking that any eventual physical solution will be a kind of multi-layer sandwich using polyethylene and water as an easy-to-use low-maintenance hydrogen-rich fluid.
Water is one of the best radiation shielding materials you can get if you can afford the mass.
A third option might be an electrostatic shield.
After viewing that presentation, I kept coming back to another brute force electrostatic solution, expensive but great in the long term:
1. Plonk mass driver on lunar surface.
2. Fire compacted regolith to where it's needed for shielding, raw material.
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#82
by
MikeAtkinson
on 10 Nov, 2012 21:47
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I read that Bigelow were talking about adding a water layer to the inside of their composite habs to increase their BEO radiation tolerance. How effective would a water layer be against GCRs?
Water is one of the best radiation shielding materials you can get if you can afford the mass.
Water is good, but you still need a lot of it. Too much in my opinion for such a brute force approach to be used, hundreds of tonnes to shield a small hab. Unlike a relatively small storm shelter against solar storms, GCRs are constant so you need to shield the entire volume they will be living in.
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#83
by
Ben the Space Brit
on 10 Nov, 2012 22:24
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That's what I was thinking though. It strikes me that the NASA approach is partly hobbled by their seeming need to use ISS-legacy architecture. Maybe the right direction is another one - to build a far larger single hab module with internal divisions. Optimise the hab against GCRs and then include a fixed single-axis shield for increased solar protection.
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#84
by
RocketmanUS
on 11 Nov, 2012 03:41
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That's what I was thinking though. It strikes me that the NASA approach is partly hobbled by their seeming need to use ISS-legacy architecture. Maybe the right direction is another one - to build a far larger single hab module with internal divisions. Optimise the hab against GCRs and then include a fixed single-axis shield for increased solar protection.
Launching a larger single module instead of smaller pieces to make the larger one?
If we already had a HLV that could launch it, then I would say that would most likely be a good direction to go in. However we do not yet have such a launcher. So best to keep the habitable part in segments to be able to use the launchers that we do have. A flexible plan, if we don't get the HLV then we use multiple launches and still get a mission. If we do get the HLV then we could use less launches ( mainly for the propellent ). The smaller pieces also enable global launch capability. The solar power could come from one nation, the crew hab another, and the propulsion even from another nation or commercial investor in the mission(s).
From the looks of the DSH it could be possible to launch the 500 day version in two launches and add some of the internal components once in space by other launches. Water for the radiation shield for example.
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#85
by
Robotbeat
on 11 Nov, 2012 05:17
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I read that Bigelow were talking about adding a water layer to the inside of their composite habs to increase their BEO radiation tolerance. How effective would a water layer be against GCRs?
Water is one of the best radiation shielding materials you can get if you can afford the mass.
Water is good, but you still need a lot of it. Too much in my opinion for such a brute force approach to be used, hundreds of tonnes to shield a small hab. Unlike a relatively small storm shelter against solar storms, GCRs are constant so you need to shield the entire volume they will be living in.
No, you don't.
GCRs are over Emphasized. The risk for the astronaut is lower than the launch and other parts of the mission. GCR'S risk to the mission itself is practically nil.
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#86
by
MikeAtkinson
on 11 Nov, 2012 08:02
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I read that Bigelow were talking about adding a water layer to the inside of their composite habs to increase their BEO radiation tolerance. How effective would a water layer be against GCRs?
Water is one of the best radiation shielding materials you can get if you can afford the mass.
Water is good, but you still need a lot of it. Too much in my opinion for such a brute force approach to be used, hundreds of tonnes to shield a small hab. Unlike a relatively small storm shelter against solar storms, GCRs are constant so you need to shield the entire volume they will be living in.
No, you don't.
GCRs are over Emphasized. The risk for the astronaut is lower than the launch and other parts of the mission. GCR'S risk to the mission itself is practically nil.
I answered the question: How effective would a water layer be against GCRs?
Whether you need shielding depends on many factors the chief ones being mission duration and how many excess cancer deaths do you tolerate.
Taking all cancer risk factors into account (not just radiation) my guess (and it is just a guess because no one has done the research) is that for traditional DRM 5 type missions over 10 years there would be one excess astronaut death due to cancer.
Whether that excess death is acceptable or not is a matter for debate.
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#87
by
Ben the Space Brit
on 11 Nov, 2012 17:04
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That's what I was thinking though. It strikes me that the NASA approach is partly hobbled by their seeming need to use ISS-legacy architecture. Maybe the right direction is another one - to build a far larger single hab module with internal divisions. Optimise the hab against GCRs and then include a fixed single-axis shield for increased solar protection.
Launching a larger single module instead of smaller pieces to make the larger one?
Yes. Remember that larger module =/= larger launcher, thanks to inflatable hab modules that can be launched on much smaller vehicles. The ISS legacy that I was specifically referring to was the rigid 'coke can' concept. I'm not sure that this is the right way to go and might only be an attempt to save money but may, in the end, just end up compromising mission capability and crew safety.
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#88
by
woods170
on 12 Nov, 2012 10:32
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I read that Bigelow were talking about adding a water layer to the inside of their composite habs to increase their BEO radiation tolerance. How effective would a water layer be against GCRs?
Water is one of the best radiation shielding materials you can get if you can afford the mass.
Water is good, but you still need a lot of it. Too much in my opinion for such a brute force approach to be used, hundreds of tonnes to shield a small hab. Unlike a relatively small storm shelter against solar storms, GCRs are constant so you need to shield the entire volume they will be living in.
No, you don't.
GCRs are over Emphasized. The risk for the astronaut is lower than the launch and other parts of the mission. GCR'S risk to the mission itself is practically nil.
You know, your statement is actually correct. GCR's do their harmful work no fast enough to be a mission risk during the mission itself. But what do you think the fall-out will be (not just for NASA) when the astronauts, after having succesfully completed their BEO mission, die in the years afterwards from GCR induced cancer? There will be all hell to pay, particularly in the risk-adverse society we live in today.
The fact that NASA is studying these problems now, and identifying them for what they are (the sound barrier to break before really longterm exploration missions can take place) is a good thing. And should not be down-played by anyone.
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#89
by
Robotbeat
on 12 Nov, 2012 13:17
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You're over emphasizing the risk of cancer. Considering the very few number of astronauts likely to go on such a mission, I'm not even sure the increase in cancer risk is statistically significant (!). Getting cancer would not at all be a sure thing as you imply.
People WILL die in the future from spaceflight, the question is whether they will go anywhere first. It isn't a sure thing that they will get cancer from it. And, as I mentioned, there are other countermeasures. but if we don't go, it is guaranteed they'll never get to Mars.
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#90
by
Robotbeat
on 12 Nov, 2012 13:21
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It isn't a sound barrier. People need to stop talking about it as a kind of firm, physical barrier which it is not. We will never actually improve it if we don't hold the risk in the proper perspective.
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#91
by
woods170
on 12 Nov, 2012 13:38
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It isn't a sound barrier. People need to stop talking about it as a kind of firm, physical barrier which it is not. We will never actually improve it if we don't hold the risk in the proper perspective.
I think the statement in the NASA document is clear enough in itself. The sound barrier was broken in 1947. The referral to sound barrier clearly indicates that the authors do NOT think that the barrier raised by GCR is unbreakable. In other words: that barrier is a hurdle to take, like there are many other hurdles on the road to true manned interplanetary exploration.
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#92
by
woods170
on 12 Nov, 2012 13:47
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You're over emphasizing the risk of cancer. Considering the very few number of astronauts likely to go on such a mission, I'm not even sure the increase in cancer risk is statistically significant (!). Getting cancer would not at all be a sure thing as you imply.
Being statistically significant does not matter. Remember the fall-out of Challenger and Columbia? 14 Lives lost in accidents that could have been prevented. Their deaths were not statistically significant either considering how many people are killed in accidents that were perfectly preventable.
Yet both tragedies very nearly killed the shuttle program, because they were very public deaths.
Granted, astronauts dying of GCR induced cancer years after their mission will not be half as public, yet they will invoke the same emotion within the general public: "Why NASA, did you not prevent this while you could?"
It is for that reason that the risk of GCR is being investigated right now.
People WILL die in the future from spaceflight, the question is whether they will go anywhere first. It isn't a sure thing that they will get cancer from it. And, as I mentioned, there are other countermeasures. but if we don't go, it is guaranteed they'll never get to Mars.
Correct. So, there is your trade-off. Do we got to Mars later, after having taken all appropriate measures to safeguard the astronauts? Or, do we go to Mars earlier and risk losing people afterwards to something that could have been prevented?
With the risk-adverse society we have today I know what the answer will be. We go later.
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#93
by
Robotbeat
on 12 Nov, 2012 14:55
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It's still over-played. People keep making un-quantified assumptions about the risk, and this adds a sort of dark cloud of foreboding to everything about the topic. We need to use quantified estimates of the risk. For instance, the radiation level on much of the surface of Mars is lower than at ISS, yet we still go to ISS.
There's another elephant in the room: the estimates of cancer risk are extrapolated from extreme, acute radiation events like nuclear explosions, where the body has no time to repair itself (or increase its defenses) before getting more damage. We make this assumption because it is the conservative one.
In fact, it seems like every step along the way, we make the conservative assumption. This adds up to hugely over-emphasizing a risk which doesn't even threaten the success of the mission at all (!) while thus distracting resources from the much greater risks, such as launch failure, landing, ascent, docking, reentry, etc.
The astronauts need to know the risks and accept or reject them. Do we outlaw smoking for federal employees?
Look, if we shield against the vast majority of solar radiation (doable) and send the astronauts during solar max (when GCRs are half as much) and land on low-altitude parts of the surface where the GCR flux is already less than ISS and then partially shield the habs with Martian regolith, then this really isn't a situation where cancer is inevitable like you keep making it out to be. In fact, the risk is supposedly linear, so by this logic, we shouldn't even be launching astronauts to ISS, should we? And yet we are.
If we wait until we remove any kind of risk like this, we literally will never go.
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#94
by
Ben the Space Brit
on 12 Nov, 2012 15:36
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If we wait until we remove any kind of risk like this, we literally will never go.
I agree that full shielding isn't possible. However, that doesn't remove the responsibility to make reasonable mitigation efforts to reduce the dosage received during
any flight period - remember, it may not be possible to arrange interplanetary flights around solar maximum or minimum due to their duration.
One of the things in "
A Case For Mars" that set my teeth on edge was Zubrin's attempt to hand-wave away the radiation issue by suggesting it was more a moral failing of lack of courage. There is a hazard; let's at least make an attempt to address it in such a way that reduces the risk, even if it isn't possible to get it all the way down.
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#95
by
Robotbeat
on 12 Nov, 2012 15:46
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If we wait until we remove any kind of risk like this, we literally will never go.
I agree that full shielding isn't possible. However, that doesn't remove the responsibility to make reasonable mitigation efforts to reduce the dosage received during any flight period - remember, it may not be possible to arrange interplanetary flights around solar maximum or minimum due to their duration.
One of the things in "A Case For Mars" that set my teeth on edge was Zubrin's attempt to hand-wave away the radiation issue by suggesting it was more a moral failing of lack of courage. There is a hazard; let's at least make an attempt to address it in such a way that reduces the risk, even if it isn't possible to get it all the way down.
Well, he's basically right.
But we can reasonably shield against solar radiation, which accounts for at least half and actually can jeopardize the mission.
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#96
by
Ben the Space Brit
on 12 Nov, 2012 16:00
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If we wait until we remove any kind of risk like this, we literally will never go.
One of the things in "A Case For Mars" that set my teeth on edge was Zubrin's attempt to hand-wave away the radiation issue by suggesting it was more a moral failing of lack of courage. There is a hazard; let's at least make an attempt to address it in such a way that reduces the risk, even if it isn't possible to get it all the way down.
Well, he's basically right.
And it is there that we seriously differ.
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#97
by
Robotbeat
on 12 Nov, 2012 16:14
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If we wait until we remove any kind of risk like this, we literally will never go.
One of the things in "A Case For Mars" that set my teeth on edge was Zubrin's attempt to hand-wave away the radiation issue by suggesting it was more a moral failing of lack of courage. There is a hazard; let's at least make an attempt to address it in such a way that reduces the risk, even if it isn't possible to get it all the way down.
Well, he's basically right.
And it is there that we seriously differ.
How so? We won't think twice about spending a few extra billion to slightly reduce an astronaut's risk of cancer, but couldn't that few billion, if spent on Earth for preventative measures and/or screening, reduce the risk for hundreds of thousands of people? Heck, I bet that several billion spent on aggressive measures to reduce smoking could reduce the cancer risk for a
million people by more than the risk of cancer that the astronaut would face.
To not go just because of a risk of cancer not exceeding that of smoking is, indeed, a moral failure, IMHO.
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#98
by
Space Frog
on 12 Nov, 2012 18:50
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This might be getting off-topic, but I agree completely. Some folks want to basically scuttle all manned spaceflight because of radiation concerns that might not even exist. Until we actually go, we have absolutely no real, scientific data about the long-term effects of GCR on the human body in space. It's possible that the human body is perfectly capable of repairing the slow, chronic cellular damage that GCR causes; we don't really know. Even if the pessimistic view ends up being correct, it's still just a low risk - not a death sentence. There's also a low risk of dying from space junk, micrometeorite strike, launch vehicle failure, heat shield failure, and computer error. We can't eliminate these risks - so why should we insist of eliminating radiation risks, especially when we don't have enough actual long-term exposure data to be making intelligent decisions about it.
Airline pilots and staff have higher exposure to GCR's as well. It's part of the job. So do people living in the Andes (GCR exposure doubles with every 2,000 feet of altitude above sea level). We shouldn't demand that airplanes be surrounded by a shell of water a meter thick, or that people who live at high elevations be forcibly relocated to the lowlands. Hell, mountain climbers are getting bombarded like crazy, but they accept the risks. I think the radiation hysteria is very damaging to progress in human spaceflight. It would be nice if a member of the astronaut core just stood up and said "We're not afraid of GCR. Bring it on." Because the more GCR exposure our astronauts get, the better we'll understand the danger, if a serious danger exists at all. Just like all scientific work with regard to health risks, there is uncertainty. Shielding astronauts from GCRs means no progress will be made in understanding GCR damage. Honestly, it's like people want to cure malaria without having any malaria patients to study.
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#99
by
woods170
on 13 Nov, 2012 07:11
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This might be getting off-topic, but I agree completely. Some folks want to basically scuttle all manned spaceflight because of radiation concerns that might not even exist. Until we actually go, we have absolutely no real, scientific data about the long-term effects of GCR on the human body in space. It's possible that the human body is perfectly capable of repairing the slow, chronic cellular damage that GCR causes; we don't really know. Even if the pessimistic view ends up being correct, it's still just a low risk - not a death sentence. There's also a low risk of dying from space junk, micrometeorite strike, launch vehicle failure, heat shield failure, and computer error. We can't eliminate these risks - so why should we insist of eliminating radiation risks, especially when we don't have enough actual long-term exposure data to be making intelligent decisions about it.
Airline pilots and staff have higher exposure to GCR's as well. It's part of the job. So do people living in the Andes (GCR exposure doubles with every 2,000 feet of altitude above sea level). We shouldn't demand that airplanes be surrounded by a shell of water a meter thick, or that people who live at high elevations be forcibly relocated to the lowlands. Hell, mountain climbers are getting bombarded like crazy, but they accept the risks. I think the radiation hysteria is very damaging to progress in human spaceflight. It would be nice if a member of the astronaut core just stood up and said "We're not afraid of GCR. Bring it on." Because the more GCR exposure our astronauts get, the better we'll understand the danger, if a serious danger exists at all. Just like all scientific work with regard to health risks, there is uncertainty. Shielding astronauts from GCRs means no progress will be made in understanding GCR damage. Honestly, it's like people want to cure malaria without having any malaria patients to study.
On-orbit measurements and studies into the effects of radiation and particle exposure (for SPE, GCR and HZE) have been on-going since the days of Skylab, thru multiple missions of Salyut and Mir and are continued on ISS today. Those studies are the very reason why lifetime dosage limits have been imposed in the first place. Since the exact effects of prolonged exposure remain somewhat unknown, the limits have been imposed to stay on the safe side.
