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#1 2013-12-16 08:07:28

Quaoar
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Registered: 2013-12-13
Posts: 518

Mini magnetosphere radiation shielding for a manned mission

Hi to all, I'm Quaoar,

I'm an Italian physician and amateur SF writer, very interested in space exploration.

Surfing in many space forums I found a lot of people posting that a manned mission to Mars is almost impossible for cosmic ray hazard, as found by Curiosity.

Cosmic rays hazard is real, but there are also solutions: http://earthweb.ess.washington.edu/spac … elding.pdf

the devicie proposed in the article by Dr. Robert Winglee is an electromagnet with an elicon antenna inside and a gas injector. The elicon antenna ionizes the gas, that inflates the magnetic field of the electromagnet, creating a kilometer size plasma bubble, that protect the spaceship from solar and galactic cosmic ray. The devicie has the dimension of a water melon, a weight of almost 30 Kg, and needs a pulsatile power of 100 KW, that can be easly suppiled by 6-8 KW solar panel. So it can be easly implemented in a manned Red Dragon.

I don't know why it is not considered for a Mars reference mission.

Last edited by Quaoar (2013-12-16 08:11:21)

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#2 2013-12-16 16:51:53

Terraformer
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Re: Mini magnetosphere radiation shielding for a manned mission

Welcome, Quaoar. You're a physician, you say? That's good; we have plenty of engineers here, but we're somewhat lacking on the biology front.

I don't think anyone has demonstrated a working system yet. Certainly, it's something that needs to be done, but people are wary of designing a mission to rely on technology that hasn't been developed yet.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#3 2013-12-16 21:32:13

SpaceNut
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#4 2013-12-16 21:43:23

JoshNH4H
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Re: Mini magnetosphere radiation shielding for a manned mission

Hi Quaoar.  Welcome to Newmars!  I hope we see a lot of you in the future smile

In fact, my take on the Curiosity results is that Radiation is not very big of a concern.  What we've seen from the radiation results from the RAD instrument is that the radiation derived from a trip to Mars is an increased cancer risk of a few, perhaps 5%.  I'd imagine that any astronaut would be willing to go for that, and for a mission of this groundbreaking nature a 5% increased cancer risk isn't even particularly significant.

Intelligently designing the habitat by putting the places where the crew will spend the largest amounts of their time in the middle, where there is the most shielding, and otherwise putting mass between the crewmembers and the directions from which radiation will be coming (The Sun in particular but also everywhere in general, depending what kind of radiation we're talking about). 

In space, the magnetospheric idea is certainly a good one, if it could be done with low power expenditure.  I wouldn't expect the technology to be ready for a first mission, and that's not particularly an issue, so far as I'm concerned.  However, it would be nice for follow-up missions and routine transportation (when we get to that point) to be able to reduce the radiation experienced by members of the crew.  I think it's a solid idea.  I think it's also probably safer and lower mass than an electrostatic field.


-Josh

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#5 2013-12-17 08:59:52

Quaoar
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Registered: 2013-12-13
Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

JoshNH4H wrote:

Hi Quaoar.  Welcome to Newmars!  I hope we see a lot of you in the future smile

Thanks a lot smile and excuse me for my poor English.

JoshNH4H wrote:

In fact, my take on the Curiosity results is that Radiation is not very big of a concern.  What we've seen from the radiation results from the RAD instrument is that the radiation derived from a trip to Mars is an increased cancer risk of a few, perhaps 5%.  I'd imagine that any astronaut would be willing to go for that, and for a mission of this groundbreaking nature a 5% increased cancer risk isn't even particularly significant.

I agree. 25 mSv/h on the Mars surface are almost the same than in LEO, but the astronaut can use regolith to screen the habitat (or ice if the will land in a place like this http://www.space.com/1371-ice-lake-mars.html ), so they surely will take less radiation than people on the ISS. Even the habitat of the rover may be screened putting the water and the LOX-LCH4 tanks on the roof and during the EVA the astronauts may use heavier isovolumetric suits, made in the same matherials of Bigelow habitats, having a quite good protection against 200 MeV solar protons. Curiosity landed at -4000 m of altitude but if the astronauts will land in a lower place (like Hellas Basin at -8000) where the athmosphere is denser, they will teke much less radiation.

JoshNH4H wrote:

Intelligently designing the habitat by putting the places where the crew will spend the largest amounts of their time in the middle, where there is the most shielding, and otherwise putting mass between the crewmembers and the directions from which radiation will be coming (The Sun in particular but also everywhere in general, depending what kind of radiation we're talking about). 

In space, the magnetospheric idea is certainly a good one, if it could be done with low power expenditure.  I wouldn't expect the technology to be ready for a first mission, and that's not particularly an issue, so far as I'm concerned.  However, it would be nice for follow-up missions and routine transportation (when we get to that point) to be able to reduce the radiation experienced by members of the crew.  I think it's a solid idea.  I think it's also probably safer and lower mass than an electrostatic field.

I'm sure that magnetosphere is very promising and it eventually will work, if we will do R&D on it. But even without it we have a lot of strategy in cosmic rays mitigation: a double walled habitat with the water tank in the middle; building the habitat with long chain polyethilene based matherial ( http://science.nasa.gov/science-news/sc … paceships/ ). And we can also choose a fast transit mission: spending a litte more propellant, we can go to Mars in 4 month instead of 8, reducing the exposure of the astronauts ( http://www.marsjournal.org/contents/200 … 7_0002.pdf ).

Using all theese strategy, during the whoole mission, the astronauts will take less radiation than Valeri Poliakov, who spent 678 days in LEO and is still alive.

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#6 2013-12-17 15:38:46

GW Johnson
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Re: Mini magnetosphere radiation shielding for a manned mission

From what I read,  the galactic cosmic radiation (GCR) varies with sunspot cycle,  every 11 years.  Minimum GCR at solar max is 24 rem/year,  and maximum GCR at solar min is 60 rem/year.  NASA astronauts currently have a limit of 50 rem/yr. 

We don't violate that limit by very much at all,  worst case,  and stay well under it most of the cycle.  Close to max exposure,  one starts bumping into career limits with younger astronauts if the mission runs over 2.5 years.  And that doesn't take into account the half-sky shielding effect of the planet for the approximately 1-year stay at Mars,  nor the slight shielding effects of spacecraft structures (admittedly very slight).  Nor does it consider atmospheric shielding at Mars,  which is more effective than any of us had hoped.  But,  the crew that makes this trip doesn't need to fly one like it again. 

Radiation that kills is more likely a big solar flare event.  The worst of these only needs about 20 cm of water for an effective shield.  Any craft on a 2.5 year voyage will have water and wastewater tanks.  You just wrap them around your designated shelter zone.  The smart designer would make that the flight control station. 

Radiation as a reason not to go to Mars is an canard and an excuse.  We've known what has to be done for a few decades now.  And we have known how to do it for those same decades now.

GW

Last edited by GW Johnson (2013-12-17 15:41:17)


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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#7 2013-12-17 16:52:06

Quaoar
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Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

GW Johnson wrote:

From what I read,  the galactic cosmic radiation (GCR) varies with sunspot cycle,  every 11 years.  Minimum GCR at solar max is 24 rem/year,  and maximum GCR at solar min is 60 rem/year.  NASA astronauts currently have a limit of 50 rem/yr. 

We don't violate that limit by very much at all,  worst case,  and stay well under it most of the cycle.  Close to max exposure,  one starts bumping into career limits with younger astronauts if the mission runs over 2.5 years.  And that doesn't take into account the half-sky shielding effect of the planet for the approximately 1-year stay at Mars,  nor the slight shielding effects of spacecraft structures (admittedly very slight).  Nor does it consider atmospheric shielding at Mars,  which is more effective than any of us had hoped.  But,  the crew that makes this trip doesn't need to fly one like it again. 

Radiation that kills is more likely a big solar flare event.  The worst of these only needs about 20 cm of water for an effective shield.  Any craft on a 2.5 year voyage will have water and wastewater tanks.  You just wrap them around your designated shelter zone.  The smart designer would make that the flight control station. 

Radiation as a reason not to go to Mars is an canard and an excuse.  We've known what has to be done for a few decades now.  And we have known how to do it for those same decades now.

GW

Another strategy is to use some kind of drug that may protect cell from radiation. It's interesting to note that Ginkgo Biloba trees are very, very resistant to radiation (in Nagaski I've seen many ginkgos that have survived to the atomic bombing). Now ginkgo's very strong anioxidant properties are under study, and there are some evidences that may suggest it can be also used as a protection treatment for the astronauts against cosmic rays.

http://www.ncbi.nlm.nih.gov/pubmed/21716624

http://medfac.mans.edu.eg/english/foren … .%204_.pdf

http://www.sciencedaily.com/releases/20 … 122956.htm

Last edited by Quaoar (2013-12-17 16:55:09)

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#8 2013-12-17 18:05:59

JoshNH4H
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Re: Mini magnetosphere radiation shielding for a manned mission

Because we won't have time to go through extensive trials, drugs that counter radiation strike me as something to use (if they can be determined to be non-harmful) on top of radiation protection measures that are adequate by themselves.  Having said that, if there are harmless anti-radiation pills that we have good reason to believe will help the astronauts, then by all means!

I've wondered at times about using pressurized CO2, in its liquid form, at ambient Martian temperatures as radiation shielding while on-planet.  Because the CO2 is everywhere the only mass you need to bring is a container and a pump!


-Josh

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#9 2013-12-19 03:59:49

Quaoar
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Re: Mini magnetosphere radiation shielding for a manned mission

JoshNH4H wrote:

Because we won't have time to go through extensive trials, drugs that counter radiation strike me as something to use (if they can be determined to be non-harmful) on top of radiation protection measures that are adequate by themselves.  Having said that, if there are harmless anti-radiation pills that we have good reason to believe will help the astronauts, then by all means!

I've wondered at times about using pressurized CO2, in its liquid form, at ambient Martian temperatures as radiation shielding while on-planet.  Because the CO2 is everywhere the only mass you need to bring is a container and a pump!

Gingko is safe: its seeds are eaten for centuries by Japanese, and there are also gingko tablets like these in commerce ( http://www.saninforma.it/Sezione.jsp?id … neRif=2543 ).

Liquid CO2 is interesting: it may also be used as a coolant for the rover engine.

I'have found in this article an interesting Mars radiation evironment map: http://journalofcosmology.com/Mars130.html

On the Hellas Basin radiation are 10 REM/yr, so a fast transit mission (120 days travel + 600 days stay + 120 days travel) will have 20 + 16.6 + 20 = 56.6 REM/840 days = 24.2 REM/yr: well below the 50 REM/yr limit and only just a bit more of 20 REM years of ISS astronauts

Last edited by Quaoar (2013-12-19 04:02:51)

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#10 2013-12-19 08:39:08

JoshNH4H
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Re: Mini magnetosphere radiation shielding for a manned mission

We normally talk about 180 day transits, rather than 120.  The reasoning for this is that 120 day transits have excessively high delta-V requirements which makes them more-or-less unfeasible.  Having said that, if some level of medical research suggests that they are in protecting people from the negative effects of radiation that would probably meet my standards for "safe".  (Having said that, people in parts of the world have been smoking tobacco for thousands of years, and that is certainly not safe or healthy!).

Having said that, are these claims of radiation effect alleviation stemming from legitimate medical research, or are they proffered by the same people who are pushing "Homeopathic 'Medicine'", "Herbal Supplements", "'Alternative' 'Medicine'", or any of that nonsense?


-Josh

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#11 2013-12-19 09:27:15

RobertDyck
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Re: Mini magnetosphere radiation shielding for a manned mission

Mars Direct, devised by Dr. Robert Zubrin and Dr. Baker, used a 180 day transit, 425 day surface stay, and 180 days back. Also bring empty sand bags and a shovel. Astronauts would fill them with Mars dirt and pile them on the roof. It would only be one layer deep, not 2 metres, but still provide some radiation shielding.

My criteria for location: low altitude (more radiation shielding), near equator (warmer, no winter), flat and smooth (safe to land), and identified subsurface water ice. Definately below the datum, the lower the better. Some valleys have water, but landing in a canyon is very dangerous. The only location that meets all this criteria is Elysium Planetia. Hellas Basin is deeper, but not within the tropics.

Radiation exposure during transit can be reduced by launching during a year of solar minimum. Radiation in space measured by Mars Odyssey was 2/3 that measured by Curiosity. That's because Curiosity launched during solar maximum.

I have posted before about the mini-magnetosphere. Also posted a link to the University of Washington. But you're a medical doctor, so more qualified than me.

Last edited by RobertDyck (2013-12-19 09:31:04)

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#12 2013-12-19 10:03:11

Quaoar
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Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

JoshNH4H wrote:

We normally talk about 180 day transits, rather than 120.  The reasoning for this is that 120 day transits have excessively high delta-V requirements which makes them more-or-less unfeasible.

In this study ( http://www.marsjournal.org/contents/200 … 7_0002.pdf ) in 2020 an Earth departure delta-V is 3.76 km/s for a 180 days transfert orbit and 4.19 km/s for a 120 days transfert orbit: using a direct entry with aerobraking (entry velocity 7.8 km/s) and an ISPP for the return travel, I think it can be done.... with a ERV with LOX-LCH4 rocket with 3.7 km/s of exaust velocity and mass ratio of 7 instead of 5.5... Yes, You are right: it's more difficoult on the return travel.

a 180 days transfer is easier: it's also a safer free return mission: 180 EM travel + 425 stay + 180 ME travel : 30 + 11.8 + 30 REM = 71.8 REM/785 days = 33.38 REM/year
We are still below the 50 REM/year limit even with a 180 days transfer. Considering also that the 11.8 REM on Mars surface will be very less because the astronauts will leave in a habitat screened with Mars regolith.

JoshNH4H wrote:

Having said that, are these claims of radiation effect alleviation stemming from legitimate medical research, or are they proffered by the same people who are pushing "Homeopathic 'Medicine'", "Herbal Supplements", "'Alternative' 'Medicine'", or any of that nonsense?

Gingko is under study on protecting neoplastic patient of side effect of radiotherapy. Preliminary data may suggest in a future it can also be used on the astronauts, to mitigate the effect of comsic ray, but naturally it has to be prooved.

Last edited by Quaoar (2013-12-19 10:30:14)

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#13 2013-12-19 11:50:06

Quaoar
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Registered: 2013-12-13
Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

RobertDyck wrote:

Mars Direct, devised by Dr. Robert Zubrin and Dr. Baker, used a 180 day transit, 425 day surface stay, and 180 days back. Also bring empty sand bags and a shovel. Astronauts would fill them with Mars dirt and pile them on the roof. It would only be one layer deep, not 2 metres, but still provide some radiation shielding.

My criteria for location: low altitude (more radiation shielding), near equator (warmer, no winter), flat and smooth (safe to land), and identified subsurface water ice. Definately below the datum, the lower the better. Some valleys have water, but landing in a canyon is very dangerous. The only location that meets all this criteria is Elysium Planetia. Hellas Basin is deeper, but not within the tropics.

What about this nice place in vastitas borealis? http://www.space.com/1371-ice-lake-mars.html

Radiation exposure during transit can be reduced by launching during a year of solar minimum. Radiation in space measured by Mars Odyssey was 2/3 that measured by Curiosity. That's because Curiosity launched during solar maximum.

RobertDyck wrote:

I have posted before about the mini-magnetosphere. Also posted a link to the University of Washington. But you're a medical doctor, so more qualified than me.

Elyseum Planetia may be very good: it's 1500-2000 meter below the MOLA 0 ( http://www.pianetamarte.net/mappature_p … _marte.htm ) and this is fine for landing and according to the Mars radiation map ( http://journalofcosmology.com/Mars130.html ) it's only 15 REM/yr. So the whole dose for a mission will be 35 REM/tr vs 33 REM/yer of Hellas Basin (without habitat screening).
Do you fear the winter because solar panels energy output may be to low for ISPP?

Last edited by Quaoar (2013-12-21 03:22:45)

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#14 2013-12-19 13:34:19

RobertDyck
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Re: Mini magnetosphere radiation shielding for a manned mission

Quaoar wrote:

What about this nice place in vastitas borealis? http://www.space.com/1371-ice-lake-mars.html

Interesting location, and beautiful picture. I pointed this out to a friend, who printed a high-resolution colour image and framed it. It's on his wall. But it's too far north. For warmth, and to avoid winter all together, I would like to restrict the landing location to between the northern and southern tropic.

One issue is that subsurface water is plentiful close to the poles, rare close to the equator. But you want to be close to the equator. So how do you find both? Elysium Planetia is the bottom of the dried up ocean basin. Most of that basin is in the northern hemisphere, but Elysium Planetia is where it extends south and actually crosses the equator. The pack ice is just 5° north.
http://www.space.com/812-ice-packs-meth … -life.html

The ice exists in a block that resemble polar ice on Earth, according to the research team. It measures about 497 by 559 miles (800 by 900 kilometers) and averages up to 150 feet (45 meters) deep.

I should point out, I complained there was no location that met all of my criteria. Then members of NewMars reminded me of the pack ice. Ok. That's now my favourite location.

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#15 2013-12-19 18:59:26

GW Johnson
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Re: Mini magnetosphere radiation shielding for a manned mission

Sure would be nice to get some ground truth on that site,  wouldn't it?  If it really is buried massive freshwater ice,  then that is a very inviting site.

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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#16 2013-12-19 19:17:38

RobertDyck
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Re: Mini magnetosphere radiation shielding for a manned mission

Just got notice through the Canadian Space Agency that the European Space Agency is accepting landing site proposals for their ExoMars rover (2018). Hmm. This may be too recent to meet their criteria. The Space.com article on pack ice said it's "just 2 million to 5 million years old -- recent in geologic terms. It formed when early hominids were roaming Earth."

ESA requirements:

1.The site must be ancient (older than 3.6 Ga)—from Mars’ early, habitable period: Pre- to late-Noachian (Phyllosian), possibly extending into the Hesperian;
2.The site must show abundant morphological and mineralogical evidence for long-duration, or frequently reoccurring, aqueous activity;
3.The site must include numerous sedimentary rock outcrops;
4.The outcrops must be distributed over the landing ellipse to ensure that the rover can get to some of them (typical rover traverse range is a few km);
5.The site must have little dust coverage.

Last edited by RobertDyck (2013-12-19 19:19:12)

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#17 2013-12-20 00:51:57

JoshNH4H
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Re: Mini magnetosphere radiation shielding for a manned mission

I'm quite surprised that the mini-magnetospheric plasma propulsion idea hasn't gotten a lot more press/funding in general.  It seems to me that it has the ability to have a higher thrust per unit power than any other form of electric propulsion.


-Josh

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#18 2013-12-20 01:46:34

RobertDyck
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Re: Mini magnetosphere radiation shielding for a manned mission

JoshNH4H wrote:

I'm quite surprised that the mini-magnetospheric plasma propulsion idea hasn't gotten a lot more press/funding in general.  It seems to me that it has the ability to have a higher thrust per unit power than any other form of electric propulsion.

And that's the problem. The only researchers to get funding have attempted to produce a magnetic sail. Instead of radiation shielding, they're trying to produce propulsion. But any sort of "sail" will always be very low acceleration, very slow. And when you talk to congress, as soon as you say the word "sail" they'll think of wooden sailing ships. But space is supposed to be high-tech, not old and slow low-tech. That is what they think. I haven't met any US congressmen in person, but I've gotten to know a lot of Canadian politicians. If you pitch this as a Star Trek force field that can protect against radiation, then you will get funding.

force field = funding
propulsion = dead

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#19 2013-12-20 02:04:42

JoshNH4H
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Re: Mini magnetosphere radiation shielding for a manned mission

Haha well I've fortunately never had such direct exposure to a politician, but perhaps I'll call my congressman up on the matter and see if I can get some strings pulled.  Because it's a pretty minuscule budget item, and one where the public typically does not produce a whole lot of input, I believe Space policy is a great way for members of the American public to produce positive change in NASA.


-Josh

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#20 2013-12-20 05:38:28

Quaoar
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Registered: 2013-12-13
Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

RobertDyck wrote:
JoshNH4H wrote:

I'm quite surprised that the mini-magnetospheric plasma propulsion idea hasn't gotten a lot more press/funding in general.  It seems to me that it has the ability to have a higher thrust per unit power than any other form of electric propulsion.

And that's the problem. The only researchers to get funding have attempted to produce a magnetic sail. Instead of radiation shielding, they're trying to produce propulsion. But any sort of "sail" will always be very low acceleration, very slow. And when you talk to congress, as soon as you say the word "sail" they'll think of wooden sailing ships. But space is supposed to be high-tech, not old and slow low-tech. That is what they think. I haven't met any US congressmen in person, but I've gotten to know a lot of Canadian politicians. If you pitch this as a Star Trek force field that can protect against radiation, then you will get funding.

force field = funding
propulsion = dead

The most promising approach is to use the m2p2 not alone, but in assotiation with classical chemical rocket, like a sort of space motorsailer: chemical rocket insert the spaceship in a classical low energy transfer orbit and m2p2 enlarge the orbit shortening the transit.

http://www.lpi.usra.edu/publications/re … wash01.pdf

But the work above assume that m2p2 thrust is constant and indipendent from solar wind speed: the magnetic bubble would enlarge in low wind and contract in strong wind acting like a furling jib. But we dont know if it will happen really, and there will be some risk of missing the planet. So I think that in the first mission m2p2 will be used only as a shield for cosmic rays.

Last edited by Quaoar (2013-12-20 05:40:31)

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#21 2013-12-21 14:33:32

Quaoar
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Posts: 518

Re: Mini magnetosphere radiation shielding for a manned mission

RobertDyck wrote:

Interesting location, and beautiful picture. I pointed this out to a friend, who printed a high-resolution colour image and framed it. It's on his wall. But it's too far north. For warmth, and to avoid winter all together, I would like to restrict the landing location to between the northern and southern tropic.

Do you prefer to avoid winter because solar panels output may be to low to feed ISPP?

RobertDyck wrote:

One issue is that subsurface water is plentiful close to the poles, rare close to the equator. But you want to be close to the equator. So how do you find both? Elysium Planetia is the bottom of the dried up ocean basin. Most of that basin is in the northern hemisphere, but Elysium Planetia is where it extends south and actually crosses the equator. The pack ice is just 5° north.
http://www.space.com/812-ice-packs-meth … -life.html

The ice exists in a block that resemble polar ice on Earth, according to the research team. It measures about 497 by 559 miles (800 by 900 kilometers) and averages up to 150 feet (45 meters) deep.

I should point out, I complained there was no location that met all of my criteria. Then members of NewMars reminded me of the pack ice. Ok. That's now my favourite location.

It may be interest to know how deep is the water pack under the regolith terrain. If it is few meters, it will be possible to project an ERV with a drill probe to melt ice and get water for ISPP. It dosn't need to bring LH2 from home.
The proposed Red Dragon mission will have a drill to probe the soil, for water searching?

Last edited by Quaoar (2013-12-21 14:45:52)

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#22 2013-12-21 16:15:26

RobertDyck
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Re: Mini magnetosphere radiation shielding for a manned mission

Quaoar wrote:

Do you prefer to avoid winter because solar panels output may be to low to feed ISPP?

Solar panel output, greenhouse yield, power load for heating, and to ensure astronauts can go outside during their entire stay. You don't want them cooped up in the hab for months at a time. Temperature at night in summer can get down to -80°C. The low recorded by Mars Pathfinder during the 3 days it recorded weather was -77°C. Viking 2 operated for more than a year, it's record low was -111°C. You need very special boot sole material to withstand that cold. You don't want instruments to fail due to polymer embrittlement. Once I went through synthetic rubber materials on the website for Dow Corning, found one that wouldn't embrittle until -112°C. That's really pushing it; don't want astronaut boot soles cracking under their weight. PCTFE is a transparent polymer film suitable for a Mars greenhouse; it becomes brittle at -240°C. The coldest spot on Mars is the south pole in winter, the coldest temperature recorded by MGS the first year it operated was -140°C. So PCTFE film can handle cold without trouble. Orthofabric, the white exterior of EMU suits, can withstand -184°C (-300°F). But what about things like rubber for boot soles? Or other instruments? Helmet visors are polycarbonate, which has a low working temperature of -40°C. If the visor gets cold, it could crack. Best to go where cold isn't so extreme.

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#23 2013-12-21 16:56:16

SpaceNut
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#24 2013-12-21 19:00:14

GW Johnson
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Re: Mini magnetosphere radiation shielding for a manned mission

If rubber cracks,  try leather.  I never heard of leather cracking in the cold.  Oops,  you need MCP done as vacuum-protective underwear to use leather boots. 

The visor problem is more intractable.  Sounds like layers to me.  The inner one is warm enough to provide a seal even if the outer layer cracks in the cold.  At least you get to go back inside.  Some of the snow goggle materials used at South Pole Station might be worthy of consideration.  The latest record cold there is -136 F (-93 C). 

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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#25 2013-12-21 23:23:24

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,384
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Re: Mini magnetosphere radiation shielding for a manned mission

Skin-tight spandex suit with leather boots? Black leather with spike heels? Oops! This is for Mars.

What does NASA use? Spacesuits for LEO (eg EMU) are rated for +120°C to -150°C. They've used polycarbonate since Apollo. Don't know what Mercury or Gemini suits used. How do they do it? Just use helmet air to moderate visor temperature?

Or a visor of PCTFE? It's service temperature is +132°C to -240°C. I was thinking of multiple panes to control temperature. Mars has thin atmosphere, but convective heat loss may lose more heat than LEO. Make the inner panes a film just thick enough to be rigid. I'm thinking of plastic packaging for Christmas toys. The rigid shape would hold the panes in place, and prevent wrinkles. Should help prevent condensation. Each pane would still be thick enough to hold suit pressure, and sealed to the visor frame. The outer pane would be as thick as a normal helmet visor. Inner panes would be primarily for temperature control, but would act as backup pressure layers. I also want an MCP suit to use a head-worn helmet, built like a closed face motorcycle helmet. This would be a crash helmet, useful when riding an ATV. That's what they're using at FMARS and MDRS. Because a crash helmet can crack, add a soft plastic film "bag" inside the helmet, with foam separating the hard shell from the "bag". If the shell cracks, the "bag" would contain pressure. Additional comfort layer foam inside the bag.

NASA developed a scratch resistant coating for polycarbonate visors. It was commercialized, for polymer eyeglasses. Would that work on PCTFE? Probably NASA is worried about micrometeoroids, but there aren't any on the surface of Mars. Instead there's cold and sand storms. PCTFE is just as hard (scratch resistant), more gas impermeable, more transparent, handles cold better, but tensile strength isn't as good.

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