Radiation amount type risk mitigation

GW Johnson · 2017-11-30 09:16:08

"Actually, we chose Deimos with reason: Low density of 1.5 g/cm3 is very hard to explain absent volatile component. 50 wt% is consistent with both density and magnetospheric evidence. Water-evolution modeling suggests volatiles 20-60 m below polar surfaces. "

I don't doubt that what you say is true. I don't doubt that you are quoting some actual experts. My point is that this is not the only explanation for a low density. There is also (1) a dry rubble pile assembled with vacuum-containing voids due to extreme low gravity, and (2) voids left behind when the water sublimed away long ago.

But those aren't "popular" because they're unfavorable for planning missions based on exploiting local resources. You don't need 50% water to achieve that low a density. Something like ~25% vacuum-filled voids also explains it. We've already seen other small bodies like that.

My other point is that you cannot know the buried (hidden) water content is really there until you actually go there and dig/drill for it. Same is true for inferring water from hydrogen detected by remote sensing. Then, and only then, do you know who was right about a hidden resource. If you send a crew there counting on that water, and it turns out that the water is not really there, then you just killed that crew. I personally think that kind of bet is extremely unwise for a first mission.

The prudent course is to send that first crew there independent of the hidden local resource, and let them find it, or its absence. If it is really there, then subsequent crews can depend upon it.

As for an electromagnetic radiation shield, that is not an off-the-shelf piece of technology yet. The principle is valid, but nobody has any ready-to-use hardware yet that actually works. It usually takes 15-20 years to go from lab experiments to ready-to-use hardware. Unless you want to wait longer still, then why not hide behind water or propellants as your shield? You already have to have them anyway.

GW

Last edited by GW Johnson (2017-11-30 09:23:22)

elderflower · 2017-11-30 10:24:20

An EM shield will only divert charged particles, won't it? They will be diverted along field lines and onto the poles. So now you need increased mass shielding over the EM poles that you are generating.

RobertDyck · 2017-12-01 14:22:32

The papers I've readon on mimi-magnetosphere show a cylinder, not a "pumpkin". It's a lot more compact. And shows the cylinder of the device passing right through the spacecraft. Think of it as the core. Magnetic field lines pass through that core, you don't put radiation shielding there. The whole point is to deflect charged particle radiation, but that very same radiation adds to the plasma field, so the radiation itself adds to the strength of the protection field. That means charged particle plasma must pass through that core, emerging out the other side. You don't want anything to get in its way.

elderflower · 2017-12-02 05:16:00

A ferromagnetic core would maximise the field, not a hollow one. Then you will need to deal with the particles impacting the core or close to it and with any secondary radiation arising from that.

kbd512 · 2017-12-09 04:37:55

It's not like colonists are going to repeatedly go back and forth between Earth and Mars. That costs too much to begin with, so it's a non-issue for them from the word "go". Any plan to fill BFS with 130t of water from an asteroid is an unnecessary and expensive diversion for something that's not an actual problem for the colonists and a problem that we just ignore for astronauts who repeatedly go to ISS. The accumulated doses are no different, given their frequent missions to ISS, and to paraphrase Dr. Zubrin, there have been no radiological casualties within that group, nor would we expect there to be any. All NASA astronauts merely accept that their radiation doses are higher than on Earth. Space flight is a high risk activity by its very nature. Those unwilling to take the risk are under no obligation to go.

How many exploration missions can an astronaut reasonably undertake before someone else is sent in their place to maintain the knowledge base regarding how to do these missions? This isn't like taking a trip to Disney Land. Uncle Sam spends beaucoup bucks to send astronauts anywhere and the fare for the ride ain't any cheaper when the destination is tens of millions of miles from home. Astronauts aren't young dumb kids fresh out of college, either. To a person, they're all in their mid to late 30's when they start, they have years of training, they know the risks, and our training program weeds out all non-hackers.

BFS shielding is sufficient for a 3 month trip from Earth to Mars. If the colonists ever come back to Earth, it'll be an infrequent occurrence. I'd be a lot more concerned about keeping them alive and healthy on the surface of Mars. Deep space is simply a hostile and unforgiving place to live and work. Passive shielding is required for every space craft, but lighter passive shielding solutions exist right now (HDPE), even better ones are on the horizon (BNNT), and active shielding merely requires a series of experiments to evaluate the results of.

There are lots of other things that will kill a mission crew or colonists long before radiation becomes a real problem. All this mental masturbation over the non-issue of radiation is making my head hurt. Sooner or later, something is going to kill you, here, in space, or on the surface of Mars. There are real problems that need to be solved. Collecting a few more charged particles on the way to Mars isn't one of them.

Oldfart1939 · 2017-12-09 10:04:25

kbd512-

I agree with your statement completely, and further state the major health issue in long term exposure to microgravity. Just look at the condition of the ISS astronauts returning after a mission; most cannot even stand on their own for several days.

The only radiation I am concerned with is from short term events associated with solar flares.

This latest NASA "Rocket to Nowhere" neither mitigates microgravity exposure, nor includes and protection for solar flare events.

QED.

kbd512 · 2017-12-09 10:39:23

Oldfart1939,

Quite right. We already know that even short term exposure to zero G produces real deleterious health effects that aren't easy to overcome. Unless big pharma has a magic pill that can overcome basic human physiology, we need to get serious about rotating the habitation unit to provide centripetal one G.

To NASA's credit, Orion does have "configuration" radiation shielding to contend with solar flares, but that relies upon the crew detecting the SPE ahead of time, re-configuring the contents of their capsule to serve as radiation shielding, and then hiding in a hole until the event passes. My take on this is that the crew needs to be able to live and work in their spacecraft without hiding from SPE's. Non-structural BNNT liners could provide the necessary protection for a modest mass penalty.

Here's a tech brief on Orion radiation mitigation experimentation:

Orion Exploration Mission 1: Proposed Radiation Measurements in Cislunar Space

GW Johnson · 2017-12-09 12:42:34

I quite agree that SLS/Orion and the new DSG are nothing but corporate welfare programs for "old space".

I also quite agree that for exploration missions into deep space, cosmic radiation is not a threat but a risk willingly assumed. It merely means your accumulated years of space travel are not too numerous.

On the other hand, solar flare radiation is a threat easily passively shielded. This could be with plastics or similar new materials added as liners at a weight penalty to almost any design. Or, it could be by utilizing components and supplies you already have to have anyway, just also serving the purpose of shielding. That option offers less weight penalty, but restricts the vehicle designs and mission architectures you can have, to things bearing no resemblance to Apollo. Eventually, some sort of electromagnetic shield may be developed to the point of useful application, but it's going to be a while, so don't hold your breath for it.

It's not the radiation, it's the microgravity diseases that are the risk to astronauts traveling deep space. What we have really learned from all the zero-gee experience obtained over the years on ISS is that unless missions can be done in 6 months to a year, then artificial gravity is the "real cure" for this problem. But if you attempt to do that in any practical way, your vehicles and your mission architectures simply cannot resemble Apollo.

Has anybody really noticed how if it doesn't resemble Apollo made with tinkertoys left over from shuttle, NASA and "old space" don't want to do it? SLS/Orion and DSG both look like Apollo stuff. The $0.5T mission proposals for Mars all looked like Apollo stuff. Etc. (I'm including stuff that looks like Skylab in that assessment. It was literally made from Apollo stuff.)

THAT is proof positive that neither NASA nor "old space" are serious about sending men to Mars. Apollo stuff won't work to send men there because of the microgravity problem inherent with zero-gee transits between planets. Stuff that looks like Apollo has successfully sent a lot of probes and landers, but those requirements are different from the requirements for men to Mars.

Look at the deeds and the physical items, not the words. Talk is cheap.

GW

Last edited by GW Johnson (2017-12-09 12:48:19)

Oldfart1939 · 2017-12-11 19:08:33

The point being missed by most is the GCR exposure during a Mars mission of ~180 day transit time is approximately that of an ISS astronaut on a 1 year mission. GCR is not the show-stopper; only radiation from solar flares is problematic.

Spending so much mental effort on a plan to get water from Deimos is to me very discouraging. More thought should be concentrated on provision of artificial gravity for muscle wasting and bone decalcification prevention.

This strikes me as another diversion from a simple but effective mission architecture for Mars. Or, as Buzz Aldrin has so succinctly stated: Get Your Ass to Mars!

Oldfart1939 · 2017-12-16 18:37:28

kbd512-

You seem to be privy to some information that has somehow eluded me. I haven't seen anything in print that states clearly that Boeing & Lockheed Martin want to include spin gravity and radiation shielding. If you would be so kind as to include a reference I'd possibly be more likely to become more supportive of another Rocket to Nowhere. NASA has foisted this proposal for us to either like or lump. By the time we get there on a NASA designed spacecraft, the rockets will be landing at the Muskboro spaceport, and the distinguished visitors booking rooms at the Trump Mars Planetia.

kbd512 · 2017-12-16 19:52:37

Oldfart1939,

There are a variety of research articles on this topic, but Boeing is actively doing research and filing patents for these crucial technologies:

An exploration of the effectiveness of artificial mini-magnetospheres as a potential Solar Storm shelter for long term human space missions

Artificial Gravity for Low Earth Orbit (ISS) & Deep Space Exploration

The old space contractors know that there is a problem with long term habitability in deep space. It's a problem they're working on. Nobody has all the answers yet.

Oldfart1939 · 2018-01-20 11:30:49

As a comment here about radiation protection: extensive use of polyethylene-type plastics in the construction can attenuate some of the Solar Flare Event type radiation. I'm really NOT a fan of plastics as structural materials after having to replace all the Vinyl siding on my house after only a few years. I'm more in favor of a multilayered approach for space habitat construction, and actually favor a skin of Lithium-Aluminum alloy with an inner reinforcement of carbon fiber/polymer layer, followed by several skins of Kevlar fabric, then a blanket of the new Boron based nanotubes. The interior lining can also be made of LPE (linear polyethylene) with suitable crosslinkers added and stabilizers. This isn't really totally adequate, but some radiation shelters can be incorporated into a structure of done in such a manner as to maintain rotational balance of the bicycle wheel structure. It's more a problem of radiation attenuation than complete shielding.

GW Johnson · 2018-01-20 12:01:49

Layers of plastics and fabrics are precisely what the thick shells of the Bigelow inflatables are made of. The little one being evaluated at ISS is thinner, but the B-330 has a shell half a meter thick, and is supposed to offer twice as good a radiation protection as the modules of which ISS is made. That's not enough for a station outside the Van Allen belts exposed to a big solar flare by far, but it's enough for the radiation of small events.

Add something else, and you have your solar flare shelter. As I have often said, that "something else" could be water/wastewater tanks, propellant tanks, even frozen food storage bins, clustered around the outside of your manned module.

GW

SpaceNut · 2018-01-26 20:14:50

Sierra Nevada to Develop Ground Prototype Deep Space Main Habitat signing a contract to design and develop a prototype for a deep space habitat under Next Space Technologies for Exploration Partnerships-2 (NextSTEP-2).

or

https://www.sncorp.com/media/2359/nexts … 2-5-17.png

https://www.sncorp.com/press-releases/s … contracts/

SNC’s concepts could incorporate all of NASA’s key elements for a gateway:
LCM delivers a utility room that houses avionics, guidance and navigation control and life support systems.
A version of the LCM combined with the SEPM provides transportation, station keeping and orbit transfer while stationed around the moon.
Large inflatable fabric environment (LIFE) provides pressurized volume for living quarters, exercise equipment, experiment area, SNC’s advanced plant growth system and emergency radiation shelter for long-duration habitation.
Flexible airlock architecture allows for in-space assembly, extravehicular activities (EVA) by crew members and docking of visiting vehicles such as Orion.

Dream Chaser® spacecraft slated to start resupply missions to the International Space Station in 2020 under NASA’s Commercial Resupply Services-2 contract.

GW Johnson · 2018-05-11 10:12:31

To answer Oldfart1939's concern in post 108 above, the actual pressure "shell" layer is buried under successive layers of structural and insulating fabric layers half a meter thick, all of which are covered by the outer fabric layer or two, such that solar UV cannot degrade the pressure layer or the insulating layers. These insulating layers also provide the kind of radiation protection that petroleum-derived fabrics and plastics do.

It would appear to me that when the outer fabric skin looks to be degrading, that's when you replace it with some sort of "overcoat" sleeve, or else replace the module. You should not need to worry about anything deeper in, although that remains to be proven in actual practice. The BEAM module at ISS is layered the same way, but only about half as thick as a B-330 (something near 0.25 m), since it need be no better than the metal modules of the ISS to which it was sent. Last I heard, it was performing just fine, including expected radiation protection characteristics.

GW

Oldfart1939 · 2018-09-13 09:38:50

Total lack of any statements regarding either radiation protection for crew or provisions for artificial gravity. Totally irresponsible and bordering on criminal disregard for crew health or safety.

SpaceNut · 2018-09-13 17:09:44

The radiation protection absense is a real problem as the period of time for exposure is limited to just 30 days from what I am reading in the link....
Polar orbit is interesting as the past plans for the moons permanent presence would required the water in the deep craters and energy at the poles for solar.
No other plans are indicated in the article....

spacetechsforum · 2018-09-14 00:17:36

So maybe someone has an e-mail to NASA and can send them a message with questions regarding the radiation problem solution?
I mean, if they announced that they are going to do this, although the solution may still be a theory, they are going to pursue the design. If they succeed, existing radiation protection system for non-earth construction would probably alter all mission plans for any space expansion, since all would include it.

Last edited by spacetechsforum (2018-09-14 00:18:31)

Oldfart1939 · 2018-09-14 08:53:43

The radiation issue is centered around solar flares, and NOT GCR. Galactic Cosmic Radiation is always there, and the astronauts in the ISS are getting exposed the entire duration of their missions. Nearness to Earth mitigates the exposure by ~ 50%, and solar flare radiation is mitigated by the Earth's magnetosphere. The LOP-G has none of these, so the possibility of astronauts fried by solar flare proton flux is very real. This is another "Rockets to Nowhere" project. All it does is lamely justify continuing work on SLS.

spacetechsforum · 2018-10-02 14:20:10

The shallow articles like this one are exactly why I attempted to design my own version of "spaceship". I trust that you will correct me in this subject if I am wrong, since my understanding is still limited.

Indeed, the GCR is problematic, but we can solve the problem quite simply by limiting exposure via crew rotation on space stations or reasonable space travel time to Mars.
Currently the sun flares are bigger obstacle. Single short travel to Mars and back might be unlucky and get struck by it.The chances are low, so this is the risk we are willing to take. For the space stations with the rotational crews we are 100% percent sure that at some point we have dead people.

Shame no one knows a guy in NASA to get some tips on their solution to this problem with their new plan for the Moon space station.

EDIT: Ok, so i found better article on the subject (closer to source):
https://gumc.georgetown.edu/news/Animal … Astronauts

Still I am unable to find the original study to evaluate data. Any of you Americans had a better luck? The problem seems serious, since the author claims an "equivalent of a months-long period" radiation was delivered and this is exactly the time of BFR travel one way.

Last edited by spacetechsforum (2018-10-02 14:37:23)

GW Johnson · 2018-10-02 16:40:55

GCR is more of a problem for permanent colonists and mostly children. It varies more-or-less sinusoidally with the solar activity cycle from 24 REM per year to 60 REM per year. NASA astronaut radiation exposure rules include a yearly limit of 50 REM, no more than 25 REM in any one month, and a career cumulative limit that varies with age and gender, but is always 400 REM or less. A rough rule of thumb is that 500 REM in a short time like a day is a lethal dose to 100% of those exposed.

Given that there is some reduction from ship hulls, for most of the solar cycle, the astronauts are well within limits. Even the peak REM years are pretty close to a fuzzy limit. That limit is about twice what Earthly nuclear workers are allowed, and is based on what they think might be a 3% increased lifetime risk of cancer. The limit for children should be about half an order of magnitude to an order of magnitude lower, but no rules for that are yet established.

It is not GCR but solar flare radiation that is the lethal threat. That is a lower energy type of radiation more easily shielded passively, but it comes in very extremely-concentrated bursts, the big ones measuring a few 10^3 to several 10^4 REM PER HOUR(!!!), more or less similar to prompt nuclear blast fallout from a surface burst. 15-20 cm of water makes a pretty good shield even for the worst of these events, as would most propellants. They last for hours to at most a day or two. And the big ones happen every several months to a year or so. Erratically. More often during solar maximum.

Flying without solar flare shielding is what we did on Apollo, betting that in only 2 weeks of mission, none would happen. It is suicide for a mission outside the Van Allen Belts lasting months-to-years. Such an event WILL happen in that time frame. Same risk is posed to the new Gateway station around the moon, or for any base on the moon. Yet I see insufficient shielding built into any of the designs that NASA or its favorite contractors have proposed, for the moon, Gateway, or Mars.

You KNOW they are lying about radiation being a show-stopper for space travel when they point at GCR! It is the solar flare bursts that are the killer. None of the scare-mongers say a word about that.

GW

Last edited by GW Johnson (2018-10-02 16:42:05)

Void · 2018-10-02 17:01:36

I'm not taking sides in this. However I would like to see the problems mastered when and how possible.

This is something apparently NASA is working on:
https://www.nasa.gov/directorates/space … _Radiation

While this project may look too hard due to size, I think it is worth pondering what BFR/BFS could do to lift the mass to construct a thing. It could make it more plausible.

Other things I am aware of are methods to correct "Too Many Cells", and "Two Few Cells".

As for Cancer, of course there is work going on all the time.

Senescent Cells are not cancer, but inflammatory, and methods are being experimented on to get rid of them.
Stem Cell treatments for Parkinson’s is a method add cells where too few exist.

For the GI tract, it might be possible to create "Young" cells outside the body, and then add them to the injured patient, while getting rid of the Senescent cells.

But quite of this work which touches on HealthSpan Improvements / Lifespan Improvements are still a ways off.

Personally I think that BFS will go to Mars, but I think that maybe after the first explorers, magnetic protections/propulsions, and advance medicines as mentioned above may make traveling through the solar system much more safe.

GW Johnson · 2018-10-03 16:44:12

By the way, for people out on the surface of Mars (or the moon), you can cut the galactic cosmic radiation (GCR) exposure figures in half. That's because the planet beneath your feet is a shield blocking half the spherical "sky" about you. That cuts 24-to-60 REM/year out in space to 12-to-30 REM/year on the surface, well within the 50 REM/year limit.

As for solar flare radiation, half of thousands to tens-of-thousands of REM/hour is still thousands to tens-of-thousands of REM/hour, with 500 REM in a "short" time lethal to 100% of those so exposed. You need a shielded place to go hide, when flares like that hit. There is no way around that need. But 15 to 20 cm of water is a good-enough shield, and more is better. A meter or two of regolith serves, too. And like the water, more is better.

As I said in post 139 above, when somebody points at GCR as "too dangerous to go", you already KNOW they are LYING to you!!! I suggest you follow the money to find out why.

OK, on the surface of Mars or the moon, the GCR exposure is 12-to-30 REM/year. The average over an 11 year solar cycle is 21 REM/year. If your lifetime career limit is 350 REM, you could live on Mars OUT IN THE OPEN about 17 years and not exceed that NASA limit for astronauts. If it is 400 REM, you could live there OUT IN THE OPEN almost 20 years. That assumes you always duck into a good shelter when a flare hits.

Now, for the transit, there isn't much shielding. In a peak year (60 REM/year rate), you'll accumulate about 45 REM during the 9 month trip, which is 5 REM/month, well within the 25 REM in one month limit. You're still within the 50 REM in one year limit. You just need a good place to hide from the solar flares, which kill within minutes.

Question: Why does ANYONE still believe this scare talk nonsense about GCR being a reason not to go?

Second question: why does ANYONE NOT show a shielded place to hide from solar flares in their designs?

NASA, Boeing, Lockheed, I'm talking to you!!!! Spacex says they will provide that shield in the BFS, but as yet they fail to say how.

Bigelow says their meter-thick inflatable hulls are twice the shielding effect of the aluminum can modules NASA uses at ISS, but that's not quite really good enough, although much closer.

You just look up the numbers (right off NASA's own radiation website), and then just run the calculations. WHAT is so hard about THAT???? (Not one damn thing; it is exactly what I did, long ago.)

Passive shielding, no new technologies to develop. You could fly right now, using water, wastewater, and propellant, as your solar flare shield. Not to do so seems egregiously stupid to me. Not to mention entirely unethical.

Spacenut: this topic has come up of late in multiple threads. Perhaps you want to copy my two posts here, and put them there, too.

GW

Last edited by GW Johnson (2018-10-03 16:50:06)

Belter · 2018-10-04 14:05:39

Lockheed Martin's new lunar lander design looks like something from the late 70s, early 80s, or maybe a new Russian thing. I think that's the difference with Space Ex. He makes space seen sexy and bold rather than timid little half steps and ancient looking machinery.

https://video.foxnews.com/v/58443676570 … show-clips

SpaceNut · 2018-10-04 21:56:25

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.

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