Author Topic: ITS Radiation protection  (Read 41845 times)

Offline nacnud

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ITS Radiation protection
« on: 09/28/2016 10:39 pm »
I've been looking at the beautiful pictures of the ITS spacecraft landed at various stunning locations around the solar system with people wandering around outside taking in the views, what an amazing holiday that would be. However a lot of the most amazing locations are hot for not just for their selfie taking possibility, they also have radiation levels far above what is considered safe. Especially in the Jupiter system.

Now in his presentation musk mentioned creating magnetic fields on a terraformed Mars to protect from solar radiation, and this would handily keep a martian atmosphere from being eroded by the solar wind.

My question is what kind of magnetic field could a lightly modified ITS produce to protect those wanting to take a stroll on whatever body the ITS has decided to land on, and how far from the spacecraft could you get before you got fried.

So to get started what resources does the ITS give us to work with? Well there are the two propellants LOX and methane. LOX freezes at 54K (ish) so I would say that 60K would be a good lower limit to what we could cool superconducting magnets to without adding additional cooling systems to the spacecraft.

I'm off to google to look into the performance available from superconducting magnets at those temperatures and to work out how big a bubble of protection a couple of helmholtz coils could provide. This being NSF I suspect someone out there could calculate the answer of the top of their head before I get back, well I hope so as my google fu can be weak at times :)

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #1 on: 09/28/2016 10:53 pm »
Compute the gyroradius of a N Mev proton of alpha particle. You'll find you need a unhealthful magnetic field strength to encompass such a ship. Smaller confines are possible but of limited usefulness.

And with charge transfer/exchange, particles can temporarily become neutral and tunnel through this. Potentially metal particle scattering and/or reflection/refraction can allow for charge transfer effects.

Offline nacnud

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Re: ITS Radiation protection
« Reply #2 on: 09/28/2016 11:30 pm »
Thanks Space Ghost, I'll get the calculator out, once I remember how to calculate that. :)

Also it looks like we'll have to go colder than 60K, probably down to 24K, according to research from cern. Though there is no mention of what strength of B-field such a conductor can withstand before losing superconductivity. As for unhealthy levels of B-field I suppose a solution would be to make the coils bigger, so that means deployable.

Back to google to look a what are safe B-field levels, what effect high current and magnetic fields have on superconductors, what happens if we make the coils bigger and how to calculate the power requirements of all this.

Offline sanman

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Re: ITS Radiation protection
« Reply #3 on: 09/28/2016 11:40 pm »
What about the "plasma bubble" idea for mini-magnetosphere? If you can generate a plasma bubble that's a few hundred meters across, then that could protect your ship:

http://physicsworld.com/cws/article/news/2008/nov/06/magnetic-shield-could-protect-spacecraft

I wonder whether the 200kW power budget of ITS could accommodate something like this?
(ie. "Solar flare incoming - shutting off overhead lighting and entertainment devices for next 5 min!")


What Musk said about magnetosphere on Mars seems like it would have to be a similarly localized solution - nothing large enough to stop atmospheric erosion, which would require jolting the planet's core.

http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars/


Offline philw1776

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Re: ITS Radiation protection
« Reply #4 on: 09/28/2016 11:50 pm »
Read an article somewhere that running a superconducting cable around Mars' equator powered by a good sized nuclear fission plant would produce a planetary mag field.  It was not some fringe physics publication.  In any case, it will be a long time before the elonauts can manufacture such a planetary cable.

And I agree that a 100+ meters radius mag field is a possibility for spacecraft.  ESA is running a project on this.
« Last Edit: 09/28/2016 11:51 pm by philw1776 »
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Offline nacnud

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Re: ITS Radiation protection
« Reply #5 on: 09/29/2016 12:09 am »
I'm looking into the mini-magnetosphere too, but I don't think a plasma bubble shield is viable once landed on a celestial body, though I don't know enough to rule it out yet.

What I'm looking into is whether an ITS in a high ionizing radiation environment could be modified to protect suited astronauts enough to allow a flags and footprints mission as depicted below. I think in this case the body landed on is Europa. If so the daily dose there is 54 rem this is about what the NASA astronaut dose is for a year.

Offline Lars-J

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Re: ITS Radiation protection
« Reply #6 on: 09/29/2016 12:16 am »
I'm looking into the mini-magnetosphere too, but I don't think a plasma bubble shield is viable once landed on a celestial body, though I don't know enough to rule it out yet.

What I'm looking into is whether an ITS in a high ionizing radiation environment could be modified to protect suited astronauts enough to allow a flags and footprints mission as depicted below. I think in this case the body landed on is Europa. If so the daily dose there is 54 rem this is about what the NASA astronaut dose is for a year.

I think it is likely that any ITS designed for the deep solar system (Jupiter and beyond) will have some significant changes done for the crew area, to improve radiation protection and other systems.

Offline nacnud

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Re: ITS Radiation protection
« Reply #7 on: 09/29/2016 12:16 am »
Read an article somewhere that running a superconducting cable around Mars' equator powered by a good sized nuclear fission plant would produce a planetary mag field...

Too add to this I vaguely remember reading somewhere that the time taken to erode an unshielded terraformed Martian atmosphere was about 1 million years. Not a time scale significant to an individual but definitely significant on a species level.

Again no sources or maths to back this up, yet.

Offline philw1776

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Re: ITS Radiation protection
« Reply #8 on: 09/29/2016 12:21 am »
Read an article somewhere that running a superconducting cable around Mars' equator powered by a good sized nuclear fission plant would produce a planetary mag field...

Too add to this I vaguely remember reading somewhere that the time taken to erode an unshielded terraformed Martian atmosphere was about 1 million years. Not a time scale significant to an individual but definitely significant on a species level.

Again no sources or maths to back this up, yet.

I've read the same thing.  I believe it was many tens of millions but that matters not.  It's a long time. 
GCR is the biggie and is mitigated by simply placing >2 meters of regolith over your head living underground.  Storing your water overhead would be better but folks would get frakked when the roof leaks. :)
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Offline mvpel

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Re: ITS Radiation protection
« Reply #9 on: 09/29/2016 12:25 am »
What I'm looking into is whether an ITS in a high ionizing radiation environment could be modified to protect suited astronauts enough to allow a flags and footprints mission as depicted below. I think in this case the body landed on is Europa. If so the daily dose there is 54 rem this is about what the NASA astronaut dose is for a year.

You'd just have a little Bechtel nuclear reactor aboard the ITS driving a superconducting magnetic radiation shield that extends its protection far enough to cover the EVA crew and the drilling rig. No sweat.

Space Radiation Superconducting Shield
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline nacnud

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Re: ITS Radiation protection
« Reply #10 on: 09/29/2016 12:28 am »
I think it is likely that any ITS designed for the deep solar system (Jupiter and beyond) will have some significant changes done for the crew area, to improve radiation protection and other systems.

Agreed, just wondering to what extent an active radiation protection system could extend beyond the ship itself to allow people to go for a walk in these high radiation environments.

Perhaps a better solution, in low gravity, would be to add protection to individual suits. Polythene bags filled with water are the best lightweight system I know of so those people taking in the europa night sky should be looking more like the michelin man than the martian.


Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #11 on: 09/29/2016 12:29 am »
What about the "plasma bubble" idea for mini-magnetosphere? If you can generate a plasma bubble that's a few hundred meters across, then that could protect your ship:

To shield from radiation you'd need a extremely high optical density plasma that could absorb relativistic particles. If we could do that, ITER and NIF would have already succeeded.

NIF is the furthest along with alpha heating (means it absorbs X rays - which are a fraction of the optical density to absorb relativistic protons/alpha particles). Only works for seconds, takes huge apparatus, size of plasma in centimeters (or less!).

Simply - "no".

What would you need here to work as a shield ? Something that would constructively cancel inbound particles momentum on itself. So you'd need to know in advance where it would be, what momentum vector it has, and cancel (thermalize) much of the energy.

If you figure it out, there are a lot of smart people who'd love to know too ...

Offline philw1776

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Re: ITS Radiation protection
« Reply #12 on: 09/29/2016 12:32 am »
What about the "plasma bubble" idea for mini-magnetosphere? If you can generate a plasma bubble that's a few hundred meters across, then that could protect your ship:

To shield from radiation you'd need a extremely high optical density plasma that could absorb relativistic particles. If we could do that, ITER and NIF would have already succeeded.

NIF is the furthest along with alpha heating (means it absorbs X rays - which are a fraction of the optical density to absorb relativistic protons/alpha particles). Only works for seconds, takes huge apparatus, size of plasma in centimeters (or less!).

Simply - "no".

What would you need here to work as a shield ? Something that would constructively cancel inbound particles momentum on itself. So you'd need to know in advance where it would be, what momentum vector it has, and cancel (thermalize) much of the energy.

If you figure it out, there are a lot of smart people who'd love to know too ...

Tell CERN & ESA before it's too late

http://www.sr2s.eu/

"The aim of the (SRS2) project has been to develop, validate and increase the Technology Readiness Level (TRL) of the most critical technologies related to a magnetic shielding system for protecting astronauts’ lives during long duration space missions.
Long duration permanence in deep space or on the surface of planet not protected by a thick atmosphere and/or magnetosphere represent a challenge which remains, as today, unsolved. Long term exposure to Galactic Cosmic Rays (GCR) and Solar Energetic Particles (SEP) is thought to cause a significant increase in the probability of various type of cancers. Means to adequately shield the astronauts from the ionising radiation are required in order to realistically plan for exploration missions to Mars"
« Last Edit: 09/29/2016 12:33 am by philw1776 »
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Offline sanman

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Re: ITS Radiation protection
« Reply #13 on: 09/29/2016 12:34 am »
Plus the solar flux is significantly less when you're out to Jupiter and beyond. You'd need bigger solar panels for outer solar system missions, or else maybe nuclear reactor (hopefully without aggravating the radiation risk too badly)

If nuclear reactor was installed on ITS, then you probably don't need the solar panels anymore. (Could reactor be installed somewhere in aft section, below the methalox tanks for better shielding?)

Then you'd have the juice to power your mini-magnetosphere. (Furthermore, could mini-magnetosphere anti-radiation system be combined with magnetoshell aerobraking system?)

Possible ideas:

http://www.space.com/29512-mars-mission-radiation-nasa-challenge.html

http://www.sciencedirect.com/science/article/pii/S0094576514003798




« Last Edit: 09/29/2016 12:51 am by sanman »

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #14 on: 09/29/2016 12:38 am »
Oh, and to give you the idea how much flux we are talking about, remember that when a SC like Juno dives into the radiation field, the metal of the SC warms up significantly. It's really a massive amount of radiation. 

What about the "plasma bubble" idea for mini-magnetosphere? If you can generate a plasma bubble that's a few hundred meters across, then that could protect your ship:

To shield from radiation you'd need a extremely high optical density plasma that could absorb relativistic particles. If we could do that, ITER and NIF would have already succeeded.

NIF is the furthest along with alpha heating (means it absorbs X rays - which are a fraction of the optical density to absorb relativistic protons/alpha particles). Only works for seconds, takes huge apparatus, size of plasma in centimeters (or less!).

Simply - "no".

What would you need here to work as a shield ? Something that would constructively cancel inbound particles momentum on itself. So you'd need to know in advance where it would be, what momentum vector it has, and cancel (thermalize) much of the energy.

If you figure it out, there are a lot of smart people who'd love to know too ...

Tell CERN & ESA before it's too late

http://www.sr2s.eu/

"The aim of the (SRS2) project has been to develop, validate and increase the Technology Readiness Level (TRL) of the most critical technologies related to a magnetic shielding system for protecting astronauts’ lives during long duration space missions.
Long duration permanence in deep space or on the surface of planet not protected by a thick atmosphere and/or magnetosphere represent a challenge which remains, as today, unsolved. Long term exposure to Galactic Cosmic Rays (GCR) and Solar Energetic Particles (SEP) is thought to cause a significant increase in the probability of various type of cancers. Means to adequately shield the astronauts from the ionising radiation are required in order to realistically plan for exploration missions to Mars"


GCRs are often neutral, and do cleave proteins. They can only be scattered. SEP's are charged and have higher flux.

Lots of science is spent tilting at windmills. Sometimes they succeed. We've been attempting controlled fusion for longer than I've been alive. Lets not plan on anytime soon for that, ok?

add:
Oh, and those people are among the ones who'd like to know, how you did it.
« Last Edit: 09/29/2016 12:42 am by Space Ghost 1962 »

Offline mvpel

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Re: ITS Radiation protection
« Reply #15 on: 09/29/2016 12:39 am »
If nuclear reactor was installed on ITS, then you probably don't need the solar panels anymore. (Could reactor be installed somewhere in aft section, below the methalox tanks for better shielding?)

Sailors aboard nuclear submarines get a lower dose of radiation than people working a 9-5 office job, even with the bunks right next door to the reactor compartment.
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline philw1776

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Re: ITS Radiation protection
« Reply #16 on: 09/29/2016 12:52 am »
Oh, and to give you the idea how much flux we are talking about, remember that when a SC like Juno dives into the radiation field, the metal of the SC warms up significantly. It's really a massive amount of radiation. 

What about the "plasma bubble" idea for mini-magnetosphere? If you can generate a plasma bubble that's a few hundred meters across, then that could protect your ship:

To shield from radiation you'd need a extremely high optical density plasma that could absorb relativistic particles. If we could do that, ITER and NIF would have already succeeded.

NIF is the furthest along with alpha heating (means it absorbs X rays - which are a fraction of the optical density to absorb relativistic protons/alpha particles). Only works for seconds, takes huge apparatus, size of plasma in centimeters (or less!).

Simply - "no".

What would you need here to work as a shield ? Something that would constructively cancel inbound particles momentum on itself. So you'd need to know in advance where it would be, what momentum vector it has, and cancel (thermalize) much of the energy.

If you figure it out, there are a lot of smart people who'd love to know too ...

Tell CERN & ESA before it's too late

http://www.sr2s.eu/

"The aim of the (SRS2) project has been to develop, validate and increase the Technology Readiness Level (TRL) of the most critical technologies related to a magnetic shielding system for protecting astronauts’ lives during long duration space missions.
Long duration permanence in deep space or on the surface of planet not protected by a thick atmosphere and/or magnetosphere represent a challenge which remains, as today, unsolved. Long term exposure to Galactic Cosmic Rays (GCR) and Solar Energetic Particles (SEP) is thought to cause a significant increase in the probability of various type of cancers. Means to adequately shield the astronauts from the ionising radiation are required in order to realistically plan for exploration missions to Mars"


GCRs are often neutral, and do cleave proteins. They can only be scattered. SEP's are charged and have higher flux.

Lots of science is spent tilting at windmills. Sometimes they succeed. We've been attempting controlled fusion for longer than I've been alive. Lets not plan on anytime soon for that, ok?

add:
Oh, and those people are among the ones who'd like to know, how you did it.

GCR shielding as I have said previously upthread is achieved on Mars, 1/2 by the planet itself and the rest by a few meters of regolith.  Live underground.  Stops most protons and their insidious secondary spawn.
SRS2 is aimed at charged particle solar flux shielding.  It's probably just as viable as ITS.  Both possible because physics and basic engineering are not violated.  Difficult, because each requires very clever just beyond state of the art engineering.  Doable, or maybe not in a reasonable timeframe. The only guarantee is that you are guaranteed to fail if you don't try.
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Offline sanman

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Re: ITS Radiation protection
« Reply #17 on: 09/29/2016 12:54 am »
Sailors aboard nuclear submarines get a lower dose of radiation than people working a 9-5 office job, even with the bunks right next door to the reactor compartment.

Okay, but terrestrial isn't as mass-constrained as space hardware. Hopefully proper design would mitigate risks.

Offline mvpel

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Re: ITS Radiation protection
« Reply #18 on: 09/29/2016 01:03 am »
Okay, but terrestrial isn't as mass-constrained as space hardware. Hopefully proper design would mitigate risks.

With respect to "mass constraints," you did see Elon's presentation, right?  ;D ;D ;D He said that the ITS would wind up being more of a "medium sized" rocket in a future stable of vehicles.  :o

And 30 years worth of submarine fuel would fit under your desk - the rest is cooling and shielding.

The Shielding of Mobile Reactors (Part I)
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Offline nacnud

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Re: ITS Radiation protection
« Reply #19 on: 09/29/2016 01:11 am »
So to clarify,

To shield the people having a stroll on Europa from the charged particle flux present in that environment there seems to be two solutions.
 
* a magnetic shield deployed around the area where you want to ramble, the best of these is SR2S.
* a physical barrier that stops radiation due to its interaction with the matter in the shield.

There is another option, only stay on the surface for a short time. Say 10 minutes.

Big problems with SR2S, it's a large system and only protects the volume that it contains. Your walk is only going to be a few meters before you need to move the system. Perhaps it could be fitted to a rover but not a suit.

Big problems with a physical barrier system, it's is going to be very heavy. Again perhaps it could be fitted to a rover.

The prospects of those Europa explorers coming home with much more than a couple of selfies is looking remote.

Edit: typo
« Last Edit: 09/29/2016 01:19 am by nacnud »

Offline mvpel

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Re: ITS Radiation protection
« Reply #20 on: 09/29/2016 01:59 am »
Big problems with SR2S, it's a large system and only protects the volume that it contains. Your walk is only going to be a few meters before you need to move the system. Perhaps it could be fitted to a rover but not a suit.

Well today it's a large system. They're aiming for a 10-meter diameter field in their development project, but I wonder what kind of magnetic field you could crank out if you had a small nuclear reactor at your disposal?

Quote
The prospects of those Europa explorers coming home with much more than a couple of selfies is looking remote.

If you sit in your shielded spacecraft and teleoperate the equipment that was sent ahead on another flight to build a nice ice-cave habitat, you can limit your excessive radiation exposure to however long it takes to walk from the edge of the spacecraft magnetic field to the airlock on your new ice cave. And then you can sit in your ice cave sipping cappuccino brewed from Europa water heated by your trusty nuclear reactor, and teleoperate the construction of your refueling depot for folks headed out to Saturn and beyond.

Sure, it's looking remote. But like Robert Zubrin said, "Five hundred years from now, people are not going to remember which faction came out on top in Iraq or Syria ... or whatever. But they will remember what we do to make their civilization possible."
« Last Edit: 09/29/2016 02:05 am by mvpel »
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline QuantumG

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Re: ITS Radiation protection
« Reply #21 on: 10/01/2016 09:10 am »
Not you father's GCR concern trolling.
Human spaceflight is basically just LARPing now.

Offline Vultur

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Re: ITS Radiation protection
« Reply #22 on: 10/02/2016 11:47 pm »
Compute the gyroradius of a N Mev proton of alpha particle. You'll find you need a unhealthful magnetic field strength to encompass such a ship.

Is the strength of magnetic field that would harm a human known and, if so, how? I know MRI fields are a couple of tesla... have humans ever been exposed to more than that?

 Mice have been levitated at 17 tesla without harm.

IIRC fields much above that are really hard to generate.

Offline docmordrid

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Re: ITS Radiation protection
« Reply #23 on: 10/03/2016 12:12 am »
No detectable genotoxic effects up to a 7T static MRI field. Mean age of subjects 34 years +/- 7 years.

https://dx.doi.org/10.1016%2Fj.neuroimage.2016.03.023
« Last Edit: 10/03/2016 12:14 am by docmordrid »
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Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #24 on: 10/03/2016 12:30 am »
See:
http://www.greenfacts.org/en/static-fields/l-3/4-interactions-body.htm

And:
https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-magnetic-field-have-to-be-to-kill-you/

And:
https://www.sott.net/article/282845-The-effects-of-magnetic-fields-on-the-body

Have recently held my wife's hand because she was scared of the MRI. Bits of metal from an 20 year old injury worked there way to the surface during the scan.

By the way, for acceptable shielding, 100T is a minimum for a 500ft coverage. Considering 1TEV particle flux. Now also consider the 1/r^3  effects for the rest of the ship/occupants.

Where magnetic shielding might work is in an toroidial emergency shelter. Is that this case?

Offline Vultur

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Re: ITS Radiation protection
« Reply #25 on: 10/03/2016 02:04 am »
And:
https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-magnetic-field-have-to-be-to-kill-you/

Yeah, I read that when I was looking it up. It's clear that insanely strong (magnetar level) fields would be fatal. But there doesn't seem to be any real knowledge between the ~8 Tesla humans have been exposed to (or maybe the slightly higher levels mice have been exposed to) and those ~100,000 Tesla magnetars.

Quote
And:
https://www.sott.net/article/282845-The-effects-of-magnetic-fields-on-the-body

This website doesn't look reliable, anti-vaccination stuff and such.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #26 on: 10/03/2016 03:01 am »
Read an article somewhere that running a superconducting cable around Mars' equator powered by a good sized nuclear fission plant would produce a planetary mag field...

Too add to this I vaguely remember reading somewhere that the time taken to erode an unshielded terraformed Martian atmosphere was about 1 million years. Not a time scale significant to an individual but definitely significant on a species level.

Again no sources or maths to back this up, yet.
Closer to 100 million years.

And anyway, it's relatively easy to build a magnetic field around Mars. A superconducting ring around the equator would be a nice method of global power distribution AND storage plus would protect the atmosphere. And would be a lot easier than raising the surface pressure to above the Armstrong Limit.
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Offline Robotbeat

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Re: ITS Radiation protection
« Reply #27 on: 10/03/2016 03:09 am »
Mini-magnetosphere, bah. Just use passive shielding. Polyethylene or water work fine. Methane is actually a fantastic shielding material, but would require re-designing ITS to take advantage of this fact. (Hydrogen is even better.) But starting from a clean-sheet, if you have a hard requirement to mitigate radiation, especially high energy radiation like GCR, your best bet is probably to go quickly and then put your crew module /inside/ the fuel tank. This is really annoying unless you're operating at large scale (inverse cubed/square, etc). Most efficient possible is a huge hydrogen tank used for a NTR-centric design.

But I'll jump into the magnetic shielding thing:

You DON'T need high fields necessarily. You need /large/ fields. A large hoop with low field is just as effective as small hoop with high field. Additionally, there ARE designs that actually null out the high field inside the ship, this just requires cleverness in the design of the coil.

But I prefer using propellant for shielding. Magnets are a mess, and aren't even necessarily as effective (or even as mass efficient!) as a good, thick hydrogen shield.
« Last Edit: 10/03/2016 03:10 am by Robotbeat »
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Offline mikelepage

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Re: ITS Radiation protection
« Reply #28 on: 10/03/2016 07:28 am »
Seems relevant to post a link to this toroidal magnetic spacecraft shield once more:
http://engineering.dartmouth.edu/~d76205x/research/Shielding/docs/ToMaSS.pdf

Spin gravity is not the only reason torus shapes are good.

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #29 on: 10/03/2016 05:39 pm »
And:
https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-magnetic-field-have-to-be-to-kill-you/

Yeah, I read that when I was looking it up. It's clear that insanely strong (magnetar level) fields would be fatal. But there doesn't seem to be any real knowledge between the ~8 Tesla humans have been exposed to (or maybe the slightly higher levels mice have been exposed to) and those ~100,000 Tesla magnetars.

Quote
And:
https://www.sott.net/article/282845-The-effects-of-magnetic-fields-on-the-body

This website doesn't look reliable, anti-vaccination stuff and such.
Debated the last one. Could not find a sufficient non abstract reference to some of the JHU medicine work, which has lots of arcane physiology and biological terms.

The problem with the scope of radiation issues is that the physics, engineering, physiology, biology, and aerospace design covers too broad an area for the average reader of this site to stomach.

The desire for magical "Star Trek" shields makes some blind to the actual processes you are up against.

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Re: ITS Radiation protection
« Reply #30 on: 10/06/2016 02:59 pm »
I thought it was mentioned but I don't remember where that the ITS should have its rocket end pointed to the sun and the windows pointed out to space to minimize radiation exposure to the occupants. Engines and tanks of LOX and LCH4 make good radiation blockers.
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Offline obsever

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Re: ITS Radiation protection
« Reply #31 on: 10/06/2016 04:24 pm »
I thought it was mentioned but I don't remember where that the ITS should have its rocket end pointed to the sun and the windows pointed out to space to minimize radiation exposure to the occupants. Engines and tanks of LOX and LCH4 make good radiation blockers.

Elon Musk actually said it in his presentation, but it's nonsense. Most of the dangerous radiation in space are galactic cosmic rays and solar particle events from coronal mass ejections. In both cases the radiation is mostly isotropic, so the spacecraft orientation will not really matter.
(my job is solar particle radiation research)

Offline Toast

Re: ITS Radiation protection
« Reply #32 on: 10/06/2016 04:29 pm »
I would have thought coronal mass ejections would produce nonisotropic radiation. Does that mean the only way to safeguard against that possibility is to have a "radiation room" of some sort surrounded by water tanks? Or would even that be ineffective?

Offline MP99

Re: ITS Radiation protection
« Reply #33 on: 10/06/2016 04:33 pm »


I thought it was mentioned but I don't remember where that the ITS should have its rocket end pointed to the sun and the windows pointed out to space to minimize radiation exposure to the occupants. Engines and tanks of LOX and LCH4 make good radiation blockers.

I suspect that it will be the other way around - prop tanks on the shady side to keep them from boiling off.

Which would then mean that the window would be permanently in the glare of the Sun.

Cheers, Martin

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Re: ITS Radiation protection
« Reply #34 on: 10/06/2016 04:33 pm »
Elon Musk actually said it in his presentation, but it's nonsense. Most of the dangerous radiation in space are galactic cosmic rays and solar particle events from coronal mass ejections. In both cases the radiation is mostly isotropic, so the spacecraft orientation will not really matter.
(my job is solar particle radiation research)

So whats the truth? I would assume solar radiation(flares etc) would be pretty much from the sun only. I can see cosmic being pretty isotropic. Though even that has some galactic orientation depending on charge or no charge for the particles.
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Re: ITS Radiation protection
« Reply #35 on: 10/06/2016 04:35 pm »



I suspect that it will be the other way around - prop tanks on the shady side to keep them from boiling off.

Which would then mean that the window would be permanently in the glare of the Sun.

Cheers, Martin

Light weight shades could fix that.
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Offline guckyfan

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Re: ITS Radiation protection
« Reply #36 on: 10/06/2016 04:40 pm »
Elon Musk actually said it in his presentation, but it's nonsense. Most of the dangerous radiation in space are galactic cosmic rays and solar particle events from coronal mass ejections. In both cases the radiation is mostly isotropic, so the spacecraft orientation will not really matter.
(my job is solar particle radiation research)

So whats the truth? I would assume solar radiation(flares etc) would be pretty much from the sun only. I can see cosmic being pretty isotropic. Though even that has some galactic orientation depending on charge or no charge for the particles.

Maybe not directly from the sun but aligned with magnetic fields. Isotropics would surprise me a lot. So during normal cruise I would the engines pointed towards the sun as this would give the best heat protection, besides a beautiful view of the stars. During a solar particle event point the engines to whatever direction the largest flow of particles comes. There's got to be some maximum direction even if not everything comes from there.

Offline obsever

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Re: ITS Radiation protection
« Reply #37 on: 10/06/2016 04:44 pm »
I would have thought coronal mass ejections would produce nonisotropic radiation.

CME's are a kind of large shock-waves travelling outwards from the Sun. The particles are generated inside the shock-wave, so when it passes over you, the radiation is isotropic. There is some non-isotropic flux escaping forward and backward from the CME, but that is a relatively minor contribution.


Quote
Does that mean the only way to safeguard against that possibility is to have a "radiation room" of some sort surrounded by water tanks?

Yes, but you would need a lot of water to make it really effective.

Edit: ITS will be large and can take a lot of mass, so I guess that a well-shielded radiation shelter might be possible.
« Last Edit: 10/06/2016 04:48 pm by obsever »

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Re: ITS Radiation protection
« Reply #38 on: 10/06/2016 06:28 pm »
There's got to be some maximum direction even if not everything comes from there.

Now that I think about there is always two tales to a comet.
One from light pressure.
One from the solar wind.
They look to be about ~15 deg apart from one another.
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Offline Burninate

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Re: ITS Radiation protection
« Reply #39 on: 10/06/2016 07:23 pm »
I would have thought coronal mass ejections would produce nonisotropic radiation. Does that mean the only way to safeguard against that possibility is to have a "radiation room" of some sort surrounded by water tanks? Or would even that be ineffective?

Basically, yes, that's the only way.  It doesn't need to be surrounded by water tanks, only mass - because the differences between different types of mass are fairly small (metals slightly worse, water or hydrocarbons like plastic & food slightly better).  Because this difference is small, specialized radiation shielding makes rather less sense than using some mass you would already be taking with you on the mission for some other purpose.

That mass can be water, which is easily pumped.  It can also be food, which will be the main way you store water at the beginning of the mission.

Food + H2O + O2  + humans + time =>
Humans + CO2 + More H2O than you started with, the hydrogen in the hydrocarbon food having been redistributed to the oxygen atmosphere, and additional water being implicit in even fairly well-dehydrated foodstuffs

Alternately, you could use rocket fuel that hasn't been burned yet, or on Mars removable regolith.

A solar storm room has to be small, because the mass needed for a given amount of protection scales with volume ^ (2/3).  You can't shield a whole hab because it would cost too much mass.  GCRs, which are assumed to accumulate steadily, can't be dealt with this way because you can't squeeze ten people into a closet-sized space for months at a time.  Solar storms will last more like hours to days.

Both are expected to be mostly isotropic;  Anisotropies associated with the sun blocking GCR's and with the outward net direction of the solar wind exist, but they're apparently not large enough for significant protection from directional shielding.  Also GCRs require an order of magnitude more shielding for the same reduction in radiation.

On a 1000-day conjunction-class mission, a 2kg/person*day estimate for food with 100 passengers puts the food figure at 200 tons, which is quite a bit to work with in creating a larder / storm shelter large enough for 100 passengers to have a reasonable amount of shielding.  It's a lot more shielding than 1 passenger would get with 2 tons of personal food supply.

Assume each person gets 1m^3 of space, a bit larger than a casket.  A sphere with volume 100m^3 (radius 2.88m) shielded by 200 tons recieves around 1.91t/m^2, or 191g/cm^2 (actual figure somewhat smaller because realistic-density food occupies lots of volume, so a thin-shell approximation is inappropriate... probably still more than 100g/cm^2 though).
« Last Edit: 10/06/2016 08:22 pm by Burninate »

Offline obsever

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Re: ITS Radiation protection
« Reply #40 on: 10/06/2016 08:04 pm »
There's got to be some maximum direction even if not everything comes from there.

Now that I think about there is always two tales to a comet.
One from light pressure.
One from the solar wind.
They look to be about ~15 deg apart from one another.

That is true but it has nothing to do with high energy radiation. Particles can be accelerated by magnetic fields within a coronal mass ejection to more than 10000 times higher energies than the energy of solar wind.

Offline DanielW

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Re: ITS Radiation protection
« Reply #41 on: 10/06/2016 08:49 pm »
With regards to radiation protection; how much protection would you get simply by huddling together? It seems like given a large group, even if you are on the outer edge, your exposure would be cut by more than half.

Offline tyrred

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Re: ITS Radiation protection
« Reply #42 on: 10/06/2016 10:04 pm »
Would a shadow shield provide a reasonable amount of protection against CME's, if spaceship is turned to orient it between sun and crew?  Or are shadow shields only useful in the context of shielding a crew from a nuclear propulsion radiation source?

Offline mark_m

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Re: ITS Radiation protection
« Reply #43 on: 10/07/2016 12:40 am »
How much protection from radiation would the 2 unpressurized decks of densely-packed cargo provide (as a baseline to whatever additional protection offered by a solar-storm-safe-room)? Significant or negligible?

On the return trip, when the cargo decks would be presumedly nearly empty, there would also presumedly be far fewer passengers, so a smaller area would need the additional protection.

Offline Blackjax

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Re: ITS Radiation protection
« Reply #44 on: 10/07/2016 01:22 am »
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.

When I see this sort of stuff, it makes me wonder if people are thinking too much about how we do it in gravity.  On this trip 'bunks' and 'cabins' are really going to serve two major purposes, privacy and sound suppression.  Both of these purposes can be served with detachable/collapsible/flexible dividers (quilted fabric that attaches with velcro as one example).  Rigid, walls, bunk beds, and mattresses aren't actually needed in zero-g.  I think instead of picturing a permanent 'floorplan' it might be better to think in terms of sleeping accommodations that can be stowed when not needed and spaces that can be reconfigured for flexible use and to reduce claustrophobia.

Offline Burninate

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Re: ITS Radiation protection
« Reply #45 on: 10/07/2016 01:57 am »
How much protection from radiation would the 2 unpressurized decks of densely-packed cargo provide (as a baseline to whatever additional protection offered by a solar-storm-safe-room)? Significant or negligible?

This is what I'm saying.  Densely-packed cargo *is* how you make a solar-storm-safe-room.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #46 on: 10/07/2016 02:04 am »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.
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Offline Burninate

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Re: ITS Radiation protection
« Reply #47 on: 10/07/2016 02:11 am »
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.

When I see this sort of stuff, it makes me wonder if people are thinking too much about how we do it in gravity.  On this trip 'bunks' and 'cabins' are really going to serve two major purposes, privacy and sound suppression.  Both of these purposes can be served with detachable/collapsible/flexible dividers (quilted fabric that attaches with velcro as one example).  Rigid, walls, bunk beds, and mattresses aren't actually needed in zero-g.  I think instead of picturing a permanent 'floorplan' it might be better to think in terms of sleeping accommodations that can be stowed when not needed and spaces that can be reconfigured for flexible use and to reduce claustrophobia.

On a long-term space voyage, the primary considerations should be ECLSS & sound suppression.  In order to sleep, people require low CO2 concentration, low air particulate count, and low noise.  A substantially better & quieter ventilation system will be desirable on a large long-term hab - the one aboard the ISS is unacceptably loud and drives astronauts to sleeping pills and earplugs.  And that ventilation will drive the shape of the sleeping arrangements, because ducting systems require continuous, balanced flow to ensure that there are no embarrassing circulation issues.  In a hotel, if one room is consistently cold someone might complain, whereas in a space hotel someone will come down mid-sleep with increased intracranial pressure, migraines, visual disturbances, and eventually hyperventilation.

https://thinkprogress.org/its-taking-less-co2-than-expected-to-cause-health-risks-in-astronauts-7af09e82b83#.z6kztya7x

Offline Burninate

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Re: ITS Radiation protection
« Reply #48 on: 10/07/2016 02:13 am »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.

The highest shielding this can provide consistently to all passengers is 50% of the incoming radiation, presupposing an infinite number of passengers and no issues with ventilation.  This is highly unsatisfactory, because incoming radiation may be more than twice a lethal dosage.

Offline orbitjunkie

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Re: ITS Radiation protection
« Reply #49 on: 10/07/2016 03:02 am »
I thought it was mentioned but I don't remember where that the ITS should have its rocket end pointed to the sun and the windows pointed out to space to minimize radiation exposure to the occupants. Engines and tanks of LOX and LCH4 make good radiation blockers.

$10 says wherever they align the engines, they'll rotate so Mars is always visible through the windows. 24/7 for the entire trip, and getting bigger every day.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #50 on: 10/07/2016 03:04 am »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.

The highest shielding this can provide consistently to all passengers is 50% of the incoming radiation, presupposing an infinite number of passengers and no issues with ventilation.  This is highly unsatisfactory, because incoming radiation may be more than twice a lethal dosage.
yeah, in a vacuum far outside the ship. Even the ship itself provides significant shielding.

As I said, if you're surrounded by your food/water rations and your fellow passengers in a small space, you'll be fine.
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Offline Burninate

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Re: ITS Radiation protection
« Reply #51 on: 10/07/2016 03:31 am »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.

The highest shielding this can provide consistently to all passengers is 50% of the incoming radiation, presupposing an infinite number of passengers and no issues with ventilation.  This is highly unsatisfactory, because incoming radiation may be more than twice a lethal dosage.
yeah, in a vacuum far outside the ship. Even the ship itself provides significant shielding.

As I said, if you're surrounded by your food/water rations and your fellow passengers in a small space, you'll be fine.

"Yes but Soylent Shielding has nonzero utility" is certainly something I can concur with, albeit I suspect its utility is sort of negligible.  "You'll be fine" is not even something you can come close to saying at this point in the conversation.  To get from here to there you're going to need data on solar storm radiation intensity and shielding.

Offline go4mars

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Re: ITS Radiation protection
« Reply #52 on: 10/07/2016 05:08 am »
...Millions to the person who perfects an efficient zero-G shower.

How about a "Bath Bag"?

      Essentially, a large bag that a person would get into, sticking their head out through a hole that has elastic around it to "seal" it...

A bath bag with two head holes. 
Help protect that special someone from some of the radiation while helping loofa the hard to reach middle of their back.  Cooling water can circulate through.  Throw 50 or 100 of these fun occupied bath bags in a pile for extra fun shielding. 
« Last Edit: 10/07/2016 05:09 am by go4mars »
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Re: ITS Radiation protection
« Reply #53 on: 10/07/2016 12:36 pm »
I think musk has considered the radiation and zero g problems. The best solution to limit those "problems" is to get to mars quickly. He has proposed a 3 month trip instead of the cycler trips or as in the "martian" which seem to be about 6 months. Solar storms will always be a problem.
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Offline cro-magnon gramps

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Re: ITS Radiation protection
« Reply #54 on: 10/07/2016 12:57 pm »
Something that I haven't seen discussed is Electro-Magnetic Shielding...
a Google search of Electro-Magnetic Shielding for Spacecraft turned up a few hits
Cern and a few other laboratories are working the possibility...
How soon they have a practical application for use is anyone's guess
But as Elon's into Physics, it would not be surprising that he is following the progress

http://cds.cern.ch/journal/CERNBulletin/2015/32/News%20Articles/2038160?ln=en

http://www.universetoday.com/20671/ion-shield-for-interplanetary-spaceships-now-a-reality/

http://www.minimagnetosphere.rl.ac.uk/

any thoughts from the NSF brain trust?

Gramps with Shields Up, Incomming!!! Ducking and Cover  ;D
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Re: ITS Radiation protection
« Reply #55 on: 10/07/2016 01:48 pm »
Can I ask for a consensus as to whether Magnetic or other shielding techniques (outside of the physical barrier type), are feasible in the next 10-20 years, on a scale to protect ITS sized space craft in Space. NOT crew, leaving the confines of the space craft. Yes or No... 

I'm looking for learned opinion on this. No hand waving. Is it "magic, unicorns and fairy dust" or something that is way out, 100 + years, before a practical application is possible... Star Trek wishful thinking...

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Re: ITS Radiation protection
« Reply #56 on: 10/07/2016 01:51 pm »
Sort of off topic.
I was reading about MgB2 Magnesium DiBoride. It is a type 1.5 superconductor and can be cooled by liquid hydrogen. This will be used in both electric transmission and replace the current superconductors in mri(niobium tin?).

https://en.wikipedia.org/wiki/Magnesium_diboride

Has critical temp of 39K and high magnetic field resistance.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

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Re: ITS Radiation protection
« Reply #57 on: 10/07/2016 02:06 pm »
So from wikipedia a field of somewhere between 14T to 55T.
So could a skin around the crew compartment have a field generating (wires) and then a inner layer of sheet. The inner layer of sheet should block the field from penetrating to the interior. The whole skin(both layers) would need to be cooled to 20K with LH2.

How much would such a skin prevent penetration of the charged particles?
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Offline Llian Rhydderch

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Re: ITS Radiation protection
« Reply #58 on: 10/07/2016 02:38 pm »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.

There is a biological analogue for the this sort of "take one for the team" social behavior: in the insect world, in the social bees. Apis mellifera, the common honeybee, does exactly that; only it is for thermal protection and life extension of the colony rather than radiation reduction.

In the winter, honeybee colonies can live and successfully overwinter in temperate latitudes with (very) cold winters.  Temperatures well below freezing  (even -20 to -25C) are survivable if a couple conditions are met:

1) the bees (those that live) never get below the temperature level that would freeze their tissues: but 'some' are very cold, and very near 0C. They do this by forming tightly packed winter clusters where the interior bees can still feed on honey stores, and generate metabolic heat, keeping the interior of the cluster ball on the order of 20+C; they will even shake/move/vibrate their bodies to get more heat under some conditions.  Heat from the interior/feeding/moving-if-necessary bees keeping the successively colder outer layers of the ball above freezing.

The ball can (and needs to, to get to more honey stores as the ball-interior honey is used up) move somewhat during the diurnal warmer parts of some days; new bees will move from the inside toward the outside, and "assume the position" (many of the outermost bees have crawled head first into empty cells in the honecomb; others fill up passages in the bee space, making a tightly packed ball); and the formerly outer layer bees will be cycled inside before they die of metabolic starvation, as they neither feed nor even move as the temp moves down through 15C to 10C to ... near 0C.  If they get the layers and heat transfer wrong, then an outer layer or two of bees may freeze, die, and eventually have their dessicated bodies cast out of the hive on a warmer cleanup day.

2) the outdoor temperature must get above freezing, and maybe  a bit higher, at least a part of a day every six weeks or so.  This allows the bees to take (very short) defecation flights and clear their waste products.  If this doesn't happen, the waste will begin to exit some bees somewhat randomly within the hive, social order will rapidly break down, that that particular colony will be one that does not overwinter successfully, and that queen will of course not live to produce any new swarms and new queens come spring.

No. 2 is the major climatological phenomenon that determines how far north (in the Northern Hemisphere) that apis mellifera bee colonies will survive.  But the description in no. 1 can also cause colonies to die off as well: if some day does not warm up sufficiently so that the ball can move to new honey stores inside the hive every so many days, then the interior bees can use up all available honey and the colony can literally starve with honey inches away, simply because the bee cluster cannot move.

TL;DR version: there is a biological analogue, even amongst the social insects, for a cluster behavior that protects the group by rotating exposure to the most dangerous part of the physical environment.

So Robotbeat's and other's surmise on the radiation protection options of human clusters for short-term risk reduction seems plausible to me.

Edit: fixed a typo
« Last Edit: 10/07/2016 04:08 pm by Llian Rhydderch »
Re arguments from authority on NSF:  "no one is exempt from error, and errors of authority are usually the worst kind.  Taking your word for things without question is no different than a bracket design not being tested because the designer was an old hand."
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Offline ThereIWas3

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Re: ITS Radiation protection
« Reply #59 on: 10/07/2016 02:49 pm »
Any information on what happens to the food?

Offline docmordrid

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Re: ITS Radiation protection
« Reply #60 on: 10/07/2016 02:52 pm »
From radiation exposure? Nothing other than its less likely to spoil because the micro-organisms are rendered dead as Caesar. Irradiation has been used for food preservation since at least WW-2.
« Last Edit: 10/07/2016 02:55 pm by docmordrid »
DM

Offline DanielW

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Re: ITS Radiation protection
« Reply #61 on: 10/07/2016 03:00 pm »
This is going to sound dumb (and maybe it is, or at least funny), but there's a significant amount of self-shielding simply by having a hundred people close together in a big huddle. Significant shielding even for the people on the outside (they're still half-shielded).

Food and water also work great.

So if you just had a massive game of "sardines" in the pantry, you're good.

I noted this one page back. The take-away is that you just need to concentrate stuff, the bigger your ship the better. Maybe have a rope lattice that you can unpack for these events in your designated shelter so people can hang on if they are in the middle. Just to give something solid to keep from being jostled by the crowd.

Offline obsever

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Re: ITS Radiation protection
« Reply #62 on: 10/07/2016 03:18 pm »
Something that I haven't seen discussed is Electro-Magnetic Shielding...

For an electromagnetic active shield to be able to deflect the really dangerous highest-energy particles you need magnets with very large coils. Off course the large size of ITS helps here. But the technology is in the stage of early concept studies, I think too immature for SpaceX to consider it. Perhaps in a future iteration of ITS design.

Taking the imagination even further, such magnets could be then perhaps also reused to deflect plasma during re-entry and reduce the requirements on heat shields / improve their reusability. But that is even further in future :)

http://phys.org/news/2009-11-superconductor-magnet-spacecraft-shield.html

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #63 on: 10/07/2016 03:32 pm »
If we model ITS as a spherical shell of 30m in diameter, its effective shielding with 150t of dry mass is 5g/cm^2, but most of that is probably carbon fiber and epoxy, which are significantly better per weight than aluminum, Which makes up partly for the fact the mass isn't evenly distributed. So already, you have enough shielding to weather the worst solar storms recorded. Plus you have landing propellant and especially a whole bunch of food and water.

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:
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Offline RonM

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Re: ITS Radiation protection
« Reply #64 on: 10/07/2016 03:54 pm »
Can I ask for a consensus as to whether Magnetic or other shielding techniques (outside of the physical barrier type), are feasible in the next 10-20 years, on a scale to protect ITS sized space craft in Space. NOT crew, leaving the confines of the space craft. Yes or No... 

I'm looking for learned opinion on this. No hand waving. Is it "magic, unicorns and fairy dust" or something that is way out, 100 + years, before a practical application is possible... Star Trek wishful thinking...

Gramps

Here's a NIAC presentation from 2014. The coils are huge. Doesn't look practical to me at today's tech.


Offline Robotbeat

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Re: ITS Radiation protection
« Reply #65 on: 10/07/2016 03:55 pm »
Magnetic shielding is not feasible in the near-term, 10-20 years. It doesn't even trade well on a mass basis. What DOES trade well is using your fuel for shielding.

People love to talk about magnetic shielding, but even if someone DID employ it, it wouldn't shield high energy GCR very well, just solar flares. Gyro radius for a given magnetic field is just too large for GCR.

Not that this will stop EVERY SINGLE radiation shielding conversation from veering to magnetic shields... :)
« Last Edit: 10/08/2016 12:36 am by Robotbeat »
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Offline obsever

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Re: ITS Radiation protection
« Reply #66 on: 10/07/2016 04:42 pm »
If we model ITS as a spherical shell of 30m in diameter, its effective shielding with 150t of dry mass is 5g/cm^2, but most of that is probably carbon fiber and epoxy, which are significantly better per weight than aluminum, Which makes up partly for the fact the mass isn't evenly distributed. So already, you have enough shielding to weather the worst solar storms recorded. Plus you have landing propellant and especially a whole bunch of food and water.

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

An issue is that radiation dose monitoring was going on only for about 4 solar cycles, and the Sun likes to surprise us sometimes. This study included an estimate for a hypotetical SPE that could have accompanied the "Carrington Flare", the strongest solar flare ever observed (in 1859):
http://www.swsc-journal.org/articles/swsc/pdf/2014/01/swsc130038.pdf

The radiation dose from such event could be deadly with 5 g/cm^2 shielding and with 20-30 g/cm^2 shielding (7-11 cm of Al, typical for ISS Columbus module according to the paper) would still exceed the 30-days limit recommended for ESA astronauts, although the colonists might perhaps accept such risk.

Offline IRobot

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Re: ITS Radiation protection
« Reply #67 on: 10/07/2016 05:13 pm »
Musk mentioned short transits to Mars. I remember an old presentation (non SpaceX) where a short (3 months) transit would make more sense in terms of food, water and reduced radiation.
An 8 month transit makes sense for a probe but with consumables for people it pays off to spend more fuel and do a faster transit.
It is an optimization between fuel and consumables + radiation shielding.

My bet is that part of radiation mitigation will be achieved by short transits.
« Last Edit: 10/07/2016 05:15 pm by IRobot »

Offline neoforce

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Re: ITS Radiation protection
« Reply #68 on: 10/07/2016 05:34 pm »
Musk mentioned short transits to Mars. I remember an old presentation (non SpaceX) where a short (3 months) transit would make more sense in terms of food, water and reduced radiation.
An 8 month transit makes sense for a probe but with consumables for people it pays off to spend more fuel and do a faster transit.
It is an optimization between fuel and consumables + radiation shielding.

My bet is that part of radiation mitigation will be achieved by short transits.

Musk published transit times in the recent talk.  See ship capacity slide at http://imgur.com/a/20nku  Average time is 115 days.  Min is 80 days, max is 150 days.

Offline envy887

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Re: ITS Radiation protection
« Reply #69 on: 10/07/2016 08:05 pm »
If we model ITS as a spherical shell of 30m in diameter, its effective shielding with 150t of dry mass is 5g/cm^2, but most of that is probably carbon fiber and epoxy, which are significantly better per weight than aluminum, Which makes up partly for the fact the mass isn't evenly distributed. So already, you have enough shielding to weather the worst solar storms recorded. Plus you have landing propellant and especially a whole bunch of food and water.

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

An issue is that radiation dose monitoring was going on only for about 4 solar cycles, and the Sun likes to surprise us sometimes. This study included an estimate for a hypotetical SPE that could have accompanied the "Carrington Flare", the strongest solar flare ever observed (in 1859):
http://www.swsc-journal.org/articles/swsc/pdf/2014/01/swsc130038.pdf

The radiation dose from such event could be deadly with 5 g/cm^2 shielding and with 20-30 g/cm^2 shielding (7-11 cm of Al, typical for ISS Columbus module according to the paper) would still exceed the 30-days limit recommended for ESA astronauts, although the colonists might perhaps accept such risk.

g/cm2 is a VERY poor way to compare materials. 5 g/cm2 of water is better than 20 g/cm2 of aluminum. Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

See this post for more details (follow the quote link to see the image):
This graph shows it most clearly as it gives a range of materials from hydrogen to lead.

As you can see on the right, even the smallest hydrogen shield reduces the radiation dose. Whereas for aluminum, there's a large portion of the right curve where the aluminum makes you worse off, but eventually helps some as you approach 30g/cm^2. For lead, it's the entire curve to beyond 30grams/cm^2 where it makes the effective dose much worse. Carbon fiber composite would be somewhere near water as far as effectiveness. As you can see, it's better than aluminum.

Offline obsever

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Re: ITS Radiation protection
« Reply #70 on: 10/07/2016 09:58 pm »
Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

First sentence in wikipedia on carbon fibre: "...composed mostly of carbon atoms."
Not any hydrogen really.


Quote
See this post for more details (follow the quote link to see the image):

Thanks, interesting thread. I'll have a closer look. From a quick look at that post, the plot refers to GCR, which is composed mostly from heavy nuclei  contain a lot more heavy nuclei than SEP.
We were talking about SEP events, which are composed >90% percent of protons so the implications on shielding materials are very different. I think g/cm^2 is a good parameter to use in this case.

In any case, with the amount of cargo carried on the ITS I'm already quite convinced that making an ad-hoc radiation shelter from food supplies, etc., should reduce the risk from SEP events to reasonably acceptable levels.

But now that you brought up GCR... that is potentially a lot nastier problem. I don't have much experience with GCR modelling, but a colleague of mine who has some is saying that with any amount of shielding (even low-Z materials) you always get a lot of secondary radiation and it's impossible to reduce that. He for sure doesn't have experience with spacecraft of ITS size (because no one does) and possible solutions such size might offer, but dealing with GCR might be an interesting challenge.

Edit: I think developing something like this might be the best solution: https://www.newscientist.com/article/dn26840-anti-radiation-drug-could-work-days-after-exposure/
« Last Edit: 10/07/2016 11:05 pm by obsever »

Offline envy887

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Re: ITS Radiation protection
« Reply #71 on: 10/07/2016 11:56 pm »
Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

First sentence in wikipedia on carbon fibre: "...composed mostly of carbon atoms."
Not any hydrogen really.
Sorry, should have said carbon fiber based composites. The fiber itself isn't hydrogenated, but the resin typically is.
Quote
Quote
See this post for more details (follow the quote link to see the image):

Thanks, interesting thread. I'll have a closer look. From a quick look at that post, the plot refers to GCR, which is composed mostly from heavy nuclei  contain a lot more heavy nuclei than SEP.
We were talking about SEP events, which are composed >90% percent of protons so the implications on shielding materials are very different. I think g/cm^2 is a good parameter to use in this case.

In any case, with the amount of cargo carried on the ITS I'm already quite convinced that making an ad-hoc radiation shelter from food supplies, etc., should reduce the risk from SEP events to reasonably acceptable levels.

But now that you brought up GCR... that is potentially a lot nastier problem. I don't have much experience with GCR modelling, but a colleague of mine who has some is saying that with any amount of shielding (even low-Z materials) you always get a lot of secondary radiation and it's impossible to reduce that. He for sure doesn't have experience with spacecraft of ITS size (because no one does) and possible solutions such size might offer, but dealing with GCR might be an interesting challenge.

Edit: I think developing something like this might be the best solution: https://www.newscientist.com/article/dn26840-anti-radiation-drug-could-work-days-after-exposure/
Don't high-energy protons also create secondaries? Either way, composites structures are better for shielding as the specific strength is higher, so for the same shielding mass you get a stronger ship (or can carry more non-structural shielding mass).

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #72 on: 10/08/2016 12:50 am »
Yeah, aluminum is a terrible baseline. It's worse than other materials, and especially for GCR. But even for SPE, you want low-atomic-mass. And carbon is much better. Carbon fiber composites even more so. Carbon fiber composite tanks filled with methane and food and water and various plastics even better.

observer:"I don't have much experience with GCR modelling, but a colleague of mine who has some is saying that with any amount of shielding (even low-Z materials) you always get a lot of secondary radiation and it's impossible to reduce that."

Well, I also have experience with GCR modeling, and your colleague is wrong. With the right materials and thicknesses (not insane thickness, either), you can reduce the effective dose of GCR. Secondaries can definitely be reduced, it's wrong to say it's impossible to reduce.

Yes, if you only have thin shielding (like an aluminum spacecraft alone), you may actually be worse off. And there's also even a slight bump in secondaries there even for low-z, but as you add shielding, it quickly gets overwhelmed by positive effects of GCR shielding with low-z materials.

EDIT: I came across a little more agitated than I intended, because I had written up this post before but I accidentally deleted it before posting and so had to rewrite it. :)
« Last Edit: 10/08/2016 01:04 am by Robotbeat »
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Offline Burninate

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Re: ITS Radiation protection
« Reply #73 on: 10/08/2016 12:54 am »
If we model ITS as a spherical shell of 30m in diameter, its effective shielding with 150t of dry mass is 5g/cm^2, but most of that is probably carbon fiber and epoxy, which are significantly better per weight than aluminum, Which makes up partly for the fact the mass isn't evenly distributed. So already, you have enough shielding to weather the worst solar storms recorded. Plus you have landing propellant and especially a whole bunch of food and water.

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

An issue is that radiation dose monitoring was going on only for about 4 solar cycles, and the Sun likes to surprise us sometimes. This study included an estimate for a hypotetical SPE that could have accompanied the "Carrington Flare", the strongest solar flare ever observed (in 1859):
http://www.swsc-journal.org/articles/swsc/pdf/2014/01/swsc130038.pdf

The radiation dose from such event could be deadly with 5 g/cm^2 shielding and with 20-30 g/cm^2 shielding (7-11 cm of Al, typical for ISS Columbus module according to the paper) would still exceed the 30-days limit recommended for ESA astronauts, although the colonists might perhaps accept such risk.

g/cm2 is a VERY poor way to compare materials. 5 g/cm2 of water is better than 20 g/cm2 of aluminum. Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

See this post for more details (follow the quote link to see the image):
This graph shows it most clearly as it gives a range of materials from hydrogen to lead.

As you can see on the right, even the smallest hydrogen shield reduces the radiation dose. Whereas for aluminum, there's a large portion of the right curve where the aluminum makes you worse off, but eventually helps some as you approach 30g/cm^2. For lead, it's the entire curve to beyond 30grams/cm^2 where it makes the effective dose much worse. Carbon fiber composite would be somewhere near water as far as effectiveness. As you can see, it's better than aluminum.

I'm gonna need a citation on that.

https://three.jsc.nasa.gov/articles/CucinottaKimChappell0512.pdf suggests that aluminum at the same cross-sectional mass will give a dose of about 10-20% higher than water, by table 6 and 7.  Robotbeat's table of GCR dose claims a slightly higher 20-40% by eye, but nowhere near 300% higher.
« Last Edit: 10/08/2016 12:58 am by Burninate »

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #74 on: 10/08/2016 12:57 am »
observer:

One of the best solutions to GCR (which complements any shielding you might have) is speed. ITS transit takes half as long as a typical human Mars architecture, which means the GCR dose is halved. That's actually a huge improvement, as halving GCR dose with shielding alone would be incredibly difficult (though not impossible, as your colleague seemed to say).

You are right that an anti-radiation drug is probably the very best solution, long-term. I'm hopeful we can develop something better than Amifostine.
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Offline Robotbeat

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Re: ITS Radiation protection
« Reply #75 on: 10/08/2016 12:59 am »
If we model ITS as a spherical shell of 30m in diameter, its effective shielding with 150t of dry mass is 5g/cm^2, but most of that is probably carbon fiber and epoxy, which are significantly better per weight than aluminum, Which makes up partly for the fact the mass isn't evenly distributed. So already, you have enough shielding to weather the worst solar storms recorded. Plus you have landing propellant and especially a whole bunch of food and water.

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

An issue is that radiation dose monitoring was going on only for about 4 solar cycles, and the Sun likes to surprise us sometimes. This study included an estimate for a hypotetical SPE that could have accompanied the "Carrington Flare", the strongest solar flare ever observed (in 1859):
http://www.swsc-journal.org/articles/swsc/pdf/2014/01/swsc130038.pdf

The radiation dose from such event could be deadly with 5 g/cm^2 shielding and with 20-30 g/cm^2 shielding (7-11 cm of Al, typical for ISS Columbus module according to the paper) would still exceed the 30-days limit recommended for ESA astronauts, although the colonists might perhaps accept such risk.

g/cm2 is a VERY poor way to compare materials. 5 g/cm2 of water is better than 20 g/cm2 of aluminum. Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

See this post for more details (follow the quote link to see the image):
This graph shows it most clearly as it gives a range of materials from hydrogen to lead.

As you can see on the right, even the smallest hydrogen shield reduces the radiation dose. Whereas for aluminum, there's a large portion of the right curve where the aluminum makes you worse off, but eventually helps some as you approach 30g/cm^2. For lead, it's the entire curve to beyond 30grams/cm^2 where it makes the effective dose much worse. Carbon fiber composite would be somewhere near water as far as effectiveness. As you can see, it's better than aluminum.

I'm gonna need a citation on that.

https://three.jsc.nasa.gov/articles/CucinottaKimChappell0512.pdf suggests that aluminum at the same cross-sectional mass will give a dose of about 10-20% higher than water, by table 6 and 7.
If you actually clicked on my post that he cited, you would see that there IS a citation right in the graph. And that the very next post was someone asking for the paper and the next post after that was me linking to it: http://asgsb.indstate.edu/bulletins/v16n2/v16n2p19-28.pdf

Additionally, the relative effectiveness of different materials is HIGHLY dependent on the spectrum of the incoming radiation and where on the shielding thickness graph you look. For thin shields and high energy radiation, aluminum can be MUCH worse than water or carbon fiber. That is why I was very specific about where on the graph I was talking about. It's misleading and kind of useless to say "aluminum at the same cross-sectional mass will give a dose of about 10-20% higher than water" without saying the thickness or radiation type.
« Last Edit: 10/08/2016 02:54 am by Robotbeat »
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Offline Burninate

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Re: ITS Radiation protection
« Reply #76 on: 10/08/2016 03:48 am »
The thread merge seems to have broken some of the quotelinks.

Robotbeat: I'm looking at figure 4 on GCR-spectrum shielding from page 24 of http://asgsb.indstate.edu/bulletins/v16n2/v16n2p19-28.pdf , the one that was snipped into an attachment... and I'm not seeing it.  The line for water and the line for aluminum are not that far from each other;  No factor-of-four improvement is depicted for water.  Maybe you're looking at the wrong line?


Meanwhile, on pages 25 & 27 of the source I linked: https://three.jsc.nasa.gov/articles/CucinottaKimChappell0512.pdf

"aluminum at the same cross-sectional mass will give a dose of about 10-20% higher than water" refers to figure 6a showing about +10% on GCR alone at solar minimum, and figure 7a that shows about +20% on GCR at solar maximum combined with an SPE identical to the one that occurred in 1972.  I'm using the E(Sv) column if that helps.
« Last Edit: 10/08/2016 03:59 am by Burninate »

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #77 on: 10/08/2016 04:00 am »
I'm looking at figure 4 on GCR-spectrum shielding from page 24 of http://asgsb.indstate.edu/bulletins/v16n2/v16n2p19-28.pdf , the one that was snipped into an attachment... and I'm not seeing it.  The line for water and the line for aluminum are not that far from each other.
The lines are close at the left side, but the right side shows actual biological effect, and the lines are significantly further apart.

Look at the second chart in Figure 4, which shows the biological effect. "1.0" is same as no shielding. As you can see, anything 10g/cm^2 or less of aluminum actually makes you WORSE off than nothing, whereas at 10g/cm^2, water has already reduced biological effect by 25%. That means that at 10g/cm^2, water is infinitely more effective than aluminum. And even at a quite thick 30g/cm^2, aluminum has only reduced the biological effect by 20%, whereas water has reduced it by 50%, so water is 2-2.5x as effective at that point.
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Offline envy887

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Re: ITS Radiation protection
« Reply #78 on: 10/08/2016 04:06 am »
The effects are highly non-linear, so saying "equivalent mass per area" doesn't mean much in terms of dose. I'm comparing the effective dose of GCR through 20g/cm2 Al and 5 g/cm2 water and they look like the same dose on the chart.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #79 on: 10/08/2016 04:32 am »
The effects are highly non-linear, so saying "equivalent mass per area" doesn't mean much in terms of dose. I'm comparing the effective dose of GCR through 20g/cm2 Al and 5 g/cm2 water and they look like the same dose on the chart.
Okay, I'd agree with that last part. Add enough aluminum, and you do indeed get some shielding out of it even for GCR.
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Offline Vultur

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Re: ITS Radiation protection
« Reply #80 on: 10/08/2016 08:28 am »

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

That chart looks like it says even the worst flare on there (Aug 72) is between "5% chance of vomiting" and "5% chance of death" at only 0.3 g/cm^2. Am I reading that wrong?

If not, do solar flares strong enough to kill by acute radiation sickness even exist short of something like the Carrington event?

You are right that an anti-radiation drug is probably the very best solution, long-term. I'm hopeful we can develop something better than Amifostine.

I think the real long-term solution will be low, chronic radiation doses not mattering because cancer becomes trivially treatable.

Offline obsever

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Re: ITS Radiation protection
« Reply #81 on: 10/08/2016 11:18 am »
Carbon fiber has a very high hydrogen content and should shield similar to water for the same mass/area.

First sentence in wikipedia on carbon fibre: "...composed mostly of carbon atoms."
Not any hydrogen really.
Sorry, should have said carbon fiber based composites. The fiber itself isn't hydrogenated, but the resin typically is.
It will probably then depend on the exact recipe SpaceX will use, but I guess you're right that it would be likely a lot better than Al.

Quote
Don't high-energy protons also create secondaries?

I might be wrong because my experience is with lower energy particles than what we talk about here, but I think that with heavier ions you get a lot more nuclear reactions like spallation, etc., so the secondaries include lighter ions and neutrons, while protons lose energy mainly by electro-magnetic interactions, so the worst secondaries in this case would be some high-energy electrons which would be easier to shield. But I'm well outside the area of my experience here, others might give a more accurate answer.

Offline obsever

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Re: ITS Radiation protection
« Reply #82 on: 10/08/2016 12:03 pm »

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

That chart looks like it says even the worst flare on there (Aug 72) is between "5% chance of vomiting" and "5% chance of death" at only 0.3 g/cm^2. Am I reading that wrong?

I'm wondering what "5% chance of death" means, death by acute radiation sickness or from developing cancer later in life?

Quote
If not, do solar flares strong enough to kill by acute radiation sickness even exist short of something like the Carrington event?

For reasonably designed spaceships probably not, but in a future with "millions living and working in space" there may be at any given moment 100's of astronauts spacewalking with limited protection from a spacesuit. In that case a 5% chance of death would be a big deal. There is already a warning system used for ISS astronauts, but I think it's only real-time. If there would be for example people working on lunar surface hours away from a shelter, some capability to predict would be needed.

By the way, solar flare is not the same as a solar particle event. Flares are explosions on the Sun, producing mainly X-rays and UV radiation. They can be associated with coronal mass ejections (CME), which in turn can be accompanied with solar particle events. Flares and CME's can disrupt electronics, but solar particle events are the ones producing high energy particles dangerous to humans.

Offline Torbjorn Larsson, OM

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Re: ITS Radiation protection
« Reply #83 on: 10/09/2016 11:02 am »
What I'm looking into is whether an ITS in a high ionizing radiation environment could be modified to protect suited astronauts enough to allow a flags and footprints mission as depicted below. I think in this case the body landed on is Europa. If so the daily dose there is 54 rem this is about what the NASA astronaut dose is for a year.

If you really want to place scientists (or hotel guests) on Europa, presumably you can melt down habitats below the surface radiation depth in advance, instead of attempting high tech shielding. However it would be a risky prospect in case of unplanned delays.


If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

That chart looks like it says even the worst flare on there (Aug 72) is between "5% chance of vomiting" and "5% chance of death" at only 0.3 g/cm^2. Am I reading that wrong?

I'm wondering what "5% chance of death" means, death by acute radiation sickness or from developing cancer later in life?

The NASA limit is 5 % increased chance integrated over a lifetime, so those charts may be graphed against that measure.

As for ITS, it would have its insulated and massive engine compartment facing the Sun adding to the metalox tanks and cargo shielding in between the crew and the radiation source.

Having advance storm warning for making it to a storm cellar behind the water tank would work for massive particles, say by placing space weather detection and communication cubesats (powered for months, so by fuel cells?) along the route. But it wouldn't work for photons. That is what klaxons are for, I suppose.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #84 on: 10/11/2016 01:16 am »

If we assume 200kg of food, water, and other consumables per person, you could have a shield 2m by 0.5m that's good for 20g/cm^2 of highly effective shielding. Arrange in a spherical phalanx with the other passengers, you have better shielding than is listed in this graph, which assumed crappy aluminum.

As you can see, solar flares would pose zero immediate mortal danger just by using the mass already on hand. Also, flares mellow out as they get further from the Sun, and these are basically the worst flares recorded:

That chart looks like it says even the worst flare on there (Aug 72) is between "5% chance of vomiting" and "5% chance of death" at only 0.3 g/cm^2. Am I reading that wrong?
You are correct. But with such thin shielding, the implication is you're not even inside a spaceship but just a spacesuit. In that case, the greater risk is probably inhaling your own vomit. But this is irrelevant for ITS because 1) no one will be doing EVAs and 2) the ship's structure is much more than 0.3g/cm^2.


Quote
I'm wondering what "5% chance of death" means, death by acute radiation sickness or from developing cancer later in life?
...
The former. Though such a big acute dose wouldn't help your cancer risk.

This is why Musk says space radiation isn't "deadly." It's really not going to kill you outright pretty much no matter what flare you get. But it is a significant long-term health risk. Luckily Mars has lots of built-in radiation shielding in its ~40g/cm^2 effective thickness atmosphere, so these kind of flares actually pose essentially zero risk. There is still a significant amount of GCR, but if your habitat is very well-shielded, I once calculated you could still afford about 30-35 hours per week outside on an EVA and remain below the maximum dose allowed for radiation workers in the US. (And I think only a fairly small minority of workers at a Mars city will work outside with any kind of regularity.)

So again, I think Musk is correct in his IAC talk about radiation. Though I do hope we develop some medication that lowers the risk even further.
« Last Edit: 10/11/2016 01:48 am by Robotbeat »
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Offline Optimist

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Re: ITS Radiation protection
« Reply #85 on: 10/11/2016 11:35 am »
Wonder if this material/tech is one of the things, Elon M. said others where working on, regarding radiation protection.
Looks like NASA has had a recent breakthrough, regarding scaling up production and so lower cost.

https://www.nasa.gov/feature/langley/team-discovers-new-method-of-making-promising-material


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Re: ITS Radiation protection
« Reply #86 on: 10/11/2016 12:10 pm »
1) The breakthrough wasn't really NASA's.
2) all that's great about it is it has boron in it.
3) it's only slightly better than some other materials, not as good as high hydrogen materials like polyethylene
4) it's supposed to be strong, but no one has made any that's usably strong for composites. It's about as strong a cotton.
5) still very expensive. Ridiculously so.
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Offline Optimist

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Re: ITS Radiation protection
« Reply #87 on: 10/11/2016 12:34 pm »
I am no expert, but according to this article its supposed to be an ideal shielding material, and better than Polyethylene.
From the article:

" Polyethylene, the same plastic commonly found in water bottles and grocery bags, also has potential as a candidate for radiation shielding. It is very high in hydrogen and fairly cheap to produce—however, it’s not strong enough to build a large structure, especially a spacecraft, which goes through high heat and strong forces during launch. And adding polyethylene to a metal structure would add quite a bit of mass, meaning that more fuel would be required for launch."

"One material in development at NASA has the potential to do both jobs: Hydrogenated boron nitride nanotubes—known as hydrogenated BNNTs—are tiny, nanotubes made of carbon, boron, and nitrogen, with hydrogen interspersed throughout the empty spaces left in between the tubes. Boron is also an excellent absorber secondary neutrons, making hydrogenated BNNTs an ideal shielding material."

http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars


 

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #88 on: 10/11/2016 12:41 pm »
Nope. As you might notice, they never actually said it's better shielding than polyethylene. Also, they haven't been very successful at achieving hydrogen loading. And the strength is terrible, still.
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Offline Robotbeat

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Re: ITS Radiation protection
« Reply #90 on: 10/12/2016 02:03 am »
Mars-bound astronauts face chronic dementia risk from galactic cosmic ray exposure
Nope. It's baloney. But of course, all the "serious" people like to grab onto imagined risks to make themselves feel better.

from Zubrin:
"Charles Limoli is pushing his "space radiation will wreck your brain" bunk again. Here's the refutation. #Mars #Space
http://www.thespacereview.com/article/2749/1 "


Quote
In fact, however, the study has no relevance for human Mars exploration, as the irradiation doses inflicted on the researchers’ unfortunate subjects has no relationship to what would be experienced by astronauts on their way to the Red Planet. The principal difference is that the rate that the dose was administered to the mice under study was four million times faster than that what travelers in interplanetary space would experience. In addition, the total cumulative dose delivered to the mice inside of 30 seconds was about 50 percent greater than the GCR dose that astronauts would receive over the course of a 2.5-year Mars mission.

And:
Quote
It is shocking that the authors neglected to caveat the significance of their results by admitting these differences. Not only that, they kept the information about actual dose rates employed buried deep within the paper (it can be found in the middle of a text paragraph towards the end entitled “Animals, heavy ion irradiation, and tissue harvesting”), thereby allowing it to easily be missed by popular science writers duped into reporting the allegedly sensational implications of their irrelevant work.
« Last Edit: 10/12/2016 02:06 am by Robotbeat »
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Offline Robotbeat

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Re: ITS Radiation protection
« Reply #91 on: 10/12/2016 02:13 am »
That ridiculous study basically subjected those poor mice to 150% the total GCR dose of a 2.5 year Mars mission in the space of 30 seconds.

Imagine a coffee drinker drinking 2.5 years of caffeine in a single cup. They'd either immediately vomit (we hope) or they'd die as they'd have FAR exceeded the ability of the body to cope with the substance.

So again, that study is severely flawed and shouldn't even be discussed. I'd argue for either its retraction or its amendment.
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Offline Pipcard

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Re: ITS Radiation protection
« Reply #92 on: 10/12/2016 04:16 am »
I don't necessarily agree with the statement below, but what do you think of it?

Radiation and zero/reduced gravity are serious issues and Zubrin by his approach (superficial analysis and ridicule) has failed to slay those dragons.

...

In The Case For Mars Zubrin claims that the increased risk of dying from cancer is about 1% and that this is much less than either the expected risk of dying from cancer of 20% or the risk to the crew from the Mars mission from other causes. He may be right, but I would want to see a peer reviewed report written by acknowledged experts in the field. Total cancer risk depends on lifestyle, by being accepted onto astronaut training and then going on a Mars mission will change the lifestyle of the crew. This effect is likely to be of the same order as the radiation effect, but it is unclear whether it is positive or not. Risk of dying from cancer is greatly effected by early diagnosis and high quality treatment. The crew both before and after a Mars mission are likely to get much better health care than the general population. These and several other factors make it difficult to produce definitive results.

Offline obsever

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Re: ITS Radiation protection
« Reply #93 on: 10/12/2016 06:16 pm »
That ridiculous study basically subjected those poor mice to 150% the total GCR dose of a 2.5 year Mars mission in the space of 30 seconds.

Imagine a coffee drinker drinking 2.5 years of caffeine in a single cup. They'd either immediately vomit (we hope) or they'd die as they'd have FAR exceeded the ability of the body to cope with the substance.

So again, that study is severely flawed and shouldn't even be discussed. I'd argue for either its retraction or its amendment.

I'm wondering if it would be worthwhile to send a Dragon with a mouse habitat on a long duration deep space mission to study GCR exposure effects and returning the mice to Earth for tissue analysis. The solar cycle is headed for a minimum in the next few years, so it will be a good time for a GCR study. Perhaps even with a small centrifuge to separate the radiation effects from the effects of zero-g. SpaceX could re-use one of their returned cargo Dragons for this, and the mission could also double as a test of high-speed re-entry for the Pica-X heat shields.

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #94 on: 10/12/2016 08:29 pm »
Ok, for those of you who've never done "due-dilligence" on a pharmaceutical firm, during early tests of such you intentionally attempt to "overdose" to prove both efficacy and toxicity.

So similarly with these radiation tests, they overdo exposure. What you'd get then are mechanisms to look for in how radiation injures tissue. After understanding the mechanisms, one then would apply them to models closer to human physiology. Then with possibly rhesus monkey's, you'd follow up with lesser "overdoses" to see that the same effects were present.

But none of this would get likely effects on a Mars expedition. To do so you'd want a long duration exposure test. Which you'd want to run something like seven times, with careful monitoring and follow up.

Estimate that effort would cost, if we could bring it off, at least $2B end to end. Which you could not incrementally finance, for various reasons involving retaining the necessary requirements to retain the integrity of the results to be unchallengable.

Now comes the bargaining to deal with the "sticker shock". Maybe we compromise X or Y, bring it down to 3 or 5 instead of 7 runs, shorter time/less exposure, less similar conditions. Improve the "cost per efficacy". On an already dangerously thin (medically speaking) statistical base. And you get ... nothing.

This is also how certain medical trials ... go bad.

You want good results it'll cost. You don't, then you get what you asked for.

Offline Darren_Hensley

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Re: ITS Radiation protection
« Reply #95 on: 10/12/2016 09:36 pm »
It seems to me the discussion here is going in circles. It's clear we need further real-time and real environment testing. It's also clear, time will be the determining factor, either someone will do the serious time and research, or we will suffer the pain of not taking the time to get serious. Even NASA astronauts have said, "We still don't have enough data to be certain about the hazards of long term space radiation exposure."

We have the opportunity here, but everyone with a stake in the game is sitting on the sideline, the coach is absent, and the stock holders are reluctant to proceed. It's time to take the field, and put the ball in play. I say we take action and start producing results that will actually make the score advance. Less talk and more walk is what we need.
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Offline obsever

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Re: ITS Radiation protection
« Reply #96 on: 10/12/2016 10:32 pm »
You want good results it'll cost. You don't, then you get what you asked for.

Fair enough. I presume that despite the costs it will have to be done eventually, if the goal is to settle the solar system.

I would like to understand whether the present state of knowledge on the subject of exposure to GCR is good enough to sufficiently manage the risk on early flights, and if not, whether something less than a full scale effort of the kind you described could improve the current knowledge considerably.
« Last Edit: 10/12/2016 10:49 pm by obsever »

Offline obsever

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Re: ITS Radiation protection
« Reply #97 on: 10/12/2016 10:58 pm »
It seems to me the discussion here is going in circles.

Well, I haven't followed the topic here long enough to notice that. But at least on the part of the circle that I followed, I find that questions about the risk from solar particle events were knowledgeably addressed, and so far the discussion on the risk from GCR is also very informative, which I appreciate.

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #98 on: 10/13/2016 12:36 am »
The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)

The likely return on these would be actual specimen lesions/effects in appropriate physiological context, with measurable quantitative effects, evaluated with the scope of potential mitigation as well as long term consequences of such.

Beyond Mars/Moon HSF, such research would likely find support for radiation therapies for other kinds of radiation exposure/hazards.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #99 on: 10/13/2016 06:24 am »
(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)

The research you are suggesting would be very helpful, I agree. But highly elliptical orbit would fly them through the van Allen belt many times. This is not a realistic deep space environment and likely lethal. Placing them in L4 or L5 would be a better way IMO. Or L1 L2. The proximity of the moon should not affect radiation that much there.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #100 on: 10/13/2016 12:05 pm »
A totally different question. One side of the ITS is covered with PicaX. Does that give any appreciable radiation protection? People could move there in case of a solar outburst.

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Re: ITS Radiation protection
« Reply #101 on: 10/13/2016 03:04 pm »
Phenolic impregnated carbon (something).
Phenolic is basically a benzene ring.
Lots of carbon and one oxygen and lots and lots of hyrdrogen.
Sounds good.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
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Offline whitelancer64

Re: ITS Radiation protection
« Reply #102 on: 10/13/2016 03:12 pm »
Phenolic impregnated carbon (something).
Phenolic is basically a benzene ring.
Lots of carbon and one oxygen and lots and lots of hyrdrogen.
Sounds good.
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Offline obsever

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Re: ITS Radiation protection
« Reply #103 on: 10/13/2016 03:28 pm »
So is there any information available about the density of Pica-X and the thickness required for 24 re-entries at hyperbolic speeds?

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Re: ITS Radiation protection
« Reply #104 on: 10/13/2016 03:30 pm »
well to start with how thick is the dragon. I saw that is rated for reentry from the moon?
Maybe 6" thick?
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Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #105 on: 10/13/2016 08:26 pm »
(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)
But highly elliptical orbit would fly them through the van Allen belt many times. This is not a realistic deep space environment and likely lethal.

Nope. Only on departure/return. Which astros would also have to do. Am talking a single "orbit", possibly leveraged with a lunar alignment coming/going.

Quote
Placing them in L4 or L5 would be a better way IMO. Or L1 L2. The proximity of the moon should not affect radiation that much there.

Too costly/complicated for an already costly/complicated and hard to fund mission. KISS principle.

And yes, the moon matters. You ideally want a exit through belts, long (multiple months) out of radiation belts, and an entry through belts.

Validates HSF vehicle too. Might need to fly this a few times.

The point is to have objective physiological data.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #106 on: 10/13/2016 08:53 pm »
The Moon doesn't matter. Solid angle from EML1/2 is just way too small averaged over the halo orbit.
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Offline guckyfan

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Re: ITS Radiation protection
« Reply #107 on: 10/13/2016 09:09 pm »
(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)
But highly elliptical orbit would fly them through the van Allen belt many times. This is not a realistic deep space environment and likely lethal.

Nope. Only on departure/return. Which astros would also have to do. Am talking a single "orbit", possibly leveraged with a lunar alignment coming/going.


The point is to have objective physiological data.

So one orbit. How long can a single orbit be? I thougt you are talking several months at least.

Offline Burninate

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Re: ITS Radiation protection
« Reply #108 on: 10/13/2016 09:47 pm »
So is there any information available about the density of Pica-X and the thickness required for 24 re-entries at hyperbolic speeds?

Other than claims that they've made very large (order of magnitude) improvements on this?  Not sure.

Regardless, though, it's not useful info.  The shielding *will necessarily have to be* light in order to permit the mission architecture, whether "light" works durably at present or not.  If the shielding substantially increases the dry mass of the vehicle, then the whole system will need to be scaled up.

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #109 on: 10/13/2016 10:04 pm »
(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)
But highly elliptical orbit would fly them through the van Allen belt many times. This is not a realistic deep space environment and likely lethal.

Nope. Only on departure/return. Which astros would also have to do. Am talking a single "orbit", possibly leveraged with a lunar alignment coming/going.


The point is to have objective physiological data.

So one orbit. How long can a single orbit be? I thougt you are talking several months at least.

Can be as long as almost one year (simple keplerian N body, almost anytime). Use the Moon/sun perturbations (narrow window), longer than a Mars synod.

In other words, "long enough".

Long enough physiologically is something like a substantial fraction of the expected HSF. Generally speaking, months.

Now lets take into account what consumables and operations might limit us to (capsule). Something like 2-3 months with current capabilities. "Good enough".

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #110 on: 10/13/2016 10:05 pm »
The Moon doesn't matter. Solid angle from EML1/2 is just way too small averaged over the halo orbit.

Not shielding issue. Operations issues.

Offline dwheeler

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Re: ITS Radiation protection
« Reply #111 on: 10/14/2016 12:38 am »
That ridiculous study basically subjected those poor mice to 150% the total GCR dose of a 2.5 year Mars mission in the space of 30 seconds.

Imagine a coffee drinker drinking 2.5 years of caffeine in a single cup. They'd either immediately vomit (we hope) or they'd die as they'd have FAR exceeded the ability of the body to cope with the substance.

So again, that study is severely flawed and shouldn't even be discussed. I'd argue for either its retraction or its amendment.

The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

(For the last, a long life HSF vehicle fitted with a test cell and robotic lab animal environment management, launched on a highly elliptic orbit would be a means to that end.)

The likely return on these would be actual specimen lesions/effects in appropriate physiological context, with measurable quantitative effects, evaluated with the scope of potential mitigation as well as long term consequences of such.

Beyond Mars/Moon HSF, such research would likely find support for radiation therapies for other kinds of radiation exposure/hazards.

 Instead of an actual orbital mission, wouldn't it be cheaper to just do the (debunked) research properly? Hit the mice in more reasonable doses (daily? hourly?) over x months.  (Poor little guys...  :-\ )

Offline guckyfan

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Re: ITS Radiation protection
« Reply #112 on: 10/14/2016 10:26 am »
The Moon doesn't matter. Solid angle from EML1/2 is just way too small averaged over the halo orbit.

Not shielding issue. Operations issues.

It was a reply to my concerns if EML1/2 would provide suitable radiation environments. Operation issues would be similar to EML4/5, I agree.


« Last Edit: 10/14/2016 10:26 am by guckyfan »

Offline guckyfan

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Re: ITS Radiation protection
« Reply #113 on: 10/14/2016 10:29 am »
So one orbit. How long can a single orbit be? I thougt you are talking several months at least.

Can be as long as almost one year (simple keplerian N body, almost anytime). Use the Moon/sun perturbations (narrow window), longer than a Mars synod.

In other words, "long enough".

Long enough physiologically is something like a substantial fraction of the expected HSF. Generally speaking, months.

Now lets take into account what consumables and operations might limit us to (capsule). Something like 2-3 months with current capabilities. "Good enough".

Thanks, I was not aware of that option.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #114 on: 10/14/2016 10:35 am »
Instead of an actual orbital mission, wouldn't it be cheaper to just do the (debunked) research properly? Hit the mice in more reasonable doses (daily? hourly?) over x months.  (Poor little guys...  :-\ )

I believe there are no suitable radiation sources. None that would be available for such a long time. Also it would be quite difficult to provide a mix of radiation types as would be present in space.

You could do research in Chernobyl. But the radiation there is different again. Research done there with mice yielded surprising results.

Offline docmordrid

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Re: ITS Radiation protection
« Reply #115 on: 10/14/2016 10:35 am »
So is there any information available about the density of Pica-X and the thickness required for 24 re-entries at hyperbolic speeds?

PICA-X v1 was about 0.27g/cm^3**. They are now on PICA-X v2 for Dragon 1 and PICA-X v3 for Crew Dragon. Densities unknown.

** http://136.142.82.187/eng12/history/spring2013/pdf/3131.pdf
DM

Offline Negan

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Re: ITS Radiation protection
« Reply #116 on: 10/14/2016 05:48 pm »
Why does this thread even exist? Either you go to Mars on ITS and live with whatever protection it provides, or you stay home.

Offline obsever

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Re: ITS Radiation protection
« Reply #117 on: 10/14/2016 06:57 pm »
Why does this thread even exist?

Why does anything exist? You may have hit upon the ultimate question there...
There is just one answer: 42  ;)
(and it's mice who are really doing the research...)


Back to the topic at hand:
The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

this looks like it could be considered a step zero on your plan:
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

Offline Negan

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Re: ITS Radiation protection
« Reply #118 on: 10/14/2016 07:19 pm »
Back to the topic at hand:
The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

this looks like it could be considered a step zero on your plan:
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

So what does this have to do with ITS radiation protection? There are no plans to any further research on their part. Plenty other of threads to discuss such theoretical research. Just people jumping on their soap box about what they think should be not what has been actually laid out. They need to get over it and move on to another thread.

If Musk is right or wrong about his views on radiation, it doesn't matter. He's the only one that gets a say when it comes to ITS.
« Last Edit: 10/14/2016 07:32 pm by Negan »

Online rsdavis9

Re: ITS Radiation protection
« Reply #119 on: 10/14/2016 07:49 pm »

Why does anything exist? You may have hit upon the ultimate question there...
There is just one answer: 42  ;)
(and it's mice who are really doing the research...)




Notice how musk put 42 engines on the booster :)
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline Hobbes-22

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Re: ITS Radiation protection
« Reply #120 on: 10/15/2016 09:18 am »
Okay, but terrestrial isn't as mass-constrained as space hardware. Hopefully proper design would mitigate risks.

With respect to "mass constraints," you did see Elon's presentation, right?  ;D ;D ;D He said that the ITS would wind up being more of a "medium sized" rocket in a future stable of vehicles.  :o

And 30 years worth of submarine fuel would fit under your desk - the rest is cooling and shielding.

The Shielding of Mobile Reactors (Part I)

To give an idea, the reactor compartment in a submarine weighs on the order of 1000 tons. And AIU cosmic rays have higher energies than the gamma produced in a reactor.

Offline Lumina

Re: ITS Radiation protection
« Reply #121 on: 10/15/2016 02:15 pm »

Why does anything exist? You may have hit upon the ultimate question there...
There is just one answer: 42  ;)
(and it's mice who are really doing the research...)


Notice how musk put 42 engines on the booster :)

And how he named the ship Heart of Gold :)

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #122 on: 10/15/2016 09:27 pm »
Why does this thread even exist?

Why does anything exist? You may have hit upon the ultimate question there...
There is just one answer: 42  ;)
(and it's mice who are really doing the research...)

Because a mature HSF effort that is trying to describe itself as a worthy HSF adventure (note Musk's "fun" and "entertainment" references to humans enjoying the transit) must consider radiation effects/mitigation. For that you need to confront/measure the physiological issues, otherwise "average" humans won't attempt it.


This isn't the desperate Mars One or even anything like Zubrin's "extreme sports" fantasy "conquest of Mars" by a few. He's talking about a much more grand scale, and thus the rules aren't the same as before..

Some narrow minded people here still have no grasp on what Musk is attempting. They try to "back fill" it into their own prior expectations, making tiny versions of ITS etc. Even Zubrin is mind-boggling stupid for the same reason. This is a lot bigger.

Even our stalwart, most practiced, best qualified "space" professionals here, on this site, ... still don't get it. Still licking their stupid wounds over the Space Shuttle not living up to expectations. Well, I was part of that past too, and am able to at least grab a tiny bit of that vision. And yet not so embittered to grapple with the scope of its unsolved problems, this is one of them.

As to agenda, simple - would like the human race to win. Duh.

Quote
Back to the topic at hand:
The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

this looks like it could be considered a step zero on your plan:
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

Am aware of this. Have been at presentations and asked questions, pointed out experiment flaws. Microfluidics in a deep space probe are dicey.

Look at the last few slides - that tells the story on all of this. Zero information.

Anything that moves the needle helps.

However, the void needs to eventually be filled with genuine in-situ physiological experiments that inform on HSF effects/mitigation. Which my example above attempts to do.

If you are serious about this thread, then apply your enthusiasm/intellect/professionalism to it. Not that hard.

Offline savuporo

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Re: ITS Radiation protection
« Reply #123 on: 10/15/2016 11:13 pm »
Quote
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

Am aware of this. Have been at presentations and asked questions, pointed out experiment flaws. Microfluidics in a deep space probe are dicey.
Why are microfluidics in deep space dicey ? A version of this is going to LEO mid next year ( barring further COPVsplosions )

https://www.nasa.gov/sites/default/files/atoms/files/powercell_fact_sheet-1aug2016-508.pdf
Orion - the first and only manned not-too-deep-space craft

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #124 on: 10/16/2016 02:45 am »
Quote
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

Am aware of this. Have been at presentations and asked questions, pointed out experiment flaws. Microfluidics in a deep space probe are dicey.
Why are microfluidics in deep space dicey ? A version of this is going to LEO mid next year ( barring further COPVsplosions )

https://www.nasa.gov/sites/default/files/atoms/files/powercell_fact_sheet-1aug2016-508.pdf

Environment issues.

Offline savuporo

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Re: ITS Radiation protection
« Reply #125 on: 10/16/2016 03:30 am »
Environment issues.
Everything going to deep space has environment issues, is there anything specific to microfluidics that would be specifically problematic ? Honest question
Orion - the first and only manned not-too-deep-space craft

Offline Space Ghost 1962

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Re: ITS Radiation protection
« Reply #126 on: 10/16/2016 03:35 am »
Environment issues.
Everything going to deep space has environment issues, is there anything specific to microfluidics that would be specifically problematic ? Honest question
Honest answer. Why bother to post anything but?

There are limits.

Offline rakaydos

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Re: ITS Radiation protection
« Reply #127 on: 10/16/2016 05:25 am »
Environment issues.
Everything going to deep space has environment issues, is there anything specific to microfluidics that would be specifically problematic ? Honest question
Honest answer. Why bother to post anything but?

There are limits.

...well that's cryptic...

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #128 on: 10/16/2016 02:13 pm »
Why does this thread even exist?

Why does anything exist? You may have hit upon the ultimate question there...
There is just one answer: 42  ;)
(and it's mice who are really doing the research...)

Because a mature HSF effort that is trying to describe itself as a worthy HSF adventure (note Musk's "fun" and "entertainment" references to humans enjoying the transit) must consider radiation effects/mitigation. For that you need to confront/measure the physiological issues, otherwise "average" humans won't attempt it.


This isn't the desperate Mars One or even anything like Zubrin's "extreme sports" fantasy "conquest of Mars" by a few. He's talking about a much more grand scale, and thus the rules aren't the same as before..

Some narrow minded people here still have no grasp on what Musk is attempting. They try to "back fill" it into their own prior expectations, making tiny versions of ITS etc. Even Zubrin is mind-boggling stupid for the same reason. This is a lot bigger.

Even our stalwart, most practiced, best qualified "space" professionals here, on this site, ... still don't get it. Still licking their stupid wounds over the Space Shuttle not living up to expectations. Well, I was part of that past too, and am able to at least grab a tiny bit of that vision. And yet not so embittered to grapple with the scope of its unsolved problems, this is one of them.

As to agenda, simple - would like the human race to win. Duh.

Quote
Back to the topic at hand:
The bottom line is that we don't have funding for appropriate basic research, that research programs are overstating results (likely on the unlikely theory that this will get them more funds...), and there's no funding for a physiological mission to gather appropriate exposure experience.

Here's what I'd fund to address this:
 + 10-20 grants on neurological tissue radiation damage processes caused by GeV energy particles
 + With these processes understood, 5-10 grants on approaches to mitigate such damage (ex:tardigrades)
 + A long duration exposure (3-6 months) of 5-7 mammals/primates in the comparable environment

this looks like it could be considered a step zero on your plan:
http://mstl.atl.calpoly.edu/~bklofas/Presentations/DevelopersWorkshop2014/Ricco_BioSentinel.pdf
It is focused on yeast cells, but perhaps it wouldn't be too much of a stretch to imagine studying neurological tissue in a similar way as a next step.

Am aware of this. Have been at presentations and asked questions, pointed out experiment flaws. Microfluidics in a deep space probe are dicey.

Look at the last few slides - that tells the story on all of this. Zero information.

Anything that moves the needle helps.

However, the void needs to eventually be filled with genuine in-situ physiological experiments that inform on HSF effects/mitigation. Which my example above attempts to do.

If you are serious about this thread, then apply your enthusiasm/intellect/professionalism to it. Not that hard.

Okay, I get what you're saying and yeah, I've thought about it in the same context.

In the "extreme sports" context, zero radiation protection is needed. None but the ship and Mars herself.

But if you want a colony and children, you need something better than nothing.

I think ITS already does a VERY good job, though, simply by operating at large scale. That makes a significant amount of self-shielding. And even more important, it travels FAST. That means half the usual dose right off the bat.

But you could also add some more shielding or use anti-radiation drugs.

Frankly, I think Musk has simply convince himself that initially, the radiation simply isn't a big problem and that long-term techniques will eventually be available to help passengers lower their dosage. Could be greater speed, better drugs, or even something like magnetic shielding using whatever superconductors are available 40 years from now.

But consider that you can build a colony that has huge amounts of shielding. In that context, the short trip doesn't add much dose, so may simply not be important.

For instance, in a ten-story building, the bottom floors will be self-shielded just by the structure above to very low levels.

You don't need to solve every future problem before starting, just convince yourself it can and will be solved.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline guckyfan

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Re: ITS Radiation protection
« Reply #129 on: 10/16/2016 02:36 pm »

In the "extreme sports" context, zero radiation protection is needed. None but the ship and Mars herself.

But if you want a colony and children, you need something better than nothing.

I am not sure that is even true. I agree this is what we must assume and work with in the beginning. But I would not be surprised at all if thorough long term research will show that we can live on the surface without any heavy shielding and without negative consequences.

Offline tdperk

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Re: ITS Radiation protection
« Reply #130 on: 10/16/2016 03:47 pm »
What quantity/sort of radionucleotides would need to be harvested/bred form belt material to sink into the crust by shafts sealed by depth, so that subsequent reactions would re-melt Mars core and re/start convection?

Has any one done such calculations?

Seems like a steady stream of tangential impactors over 1M+ years plus the core remelt would get the job done for the remainder of the solar system healthspan.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #131 on: 10/16/2016 06:05 pm »
What quantity/sort of radionucleotides would need to be harvested/bred form belt material to sink into the crust by shafts sealed by depth, so that subsequent reactions would re-melt Mars core and re/start convection?

Has any one done such calculations?

Seems like a steady stream of tangential impactors over 1M+ years plus the core remelt would get the job done for the remainder of the solar system healthspan.
Why the heck would you do that???

If you want to build a magnetic field, then build one. A big superconducting cable around the equator. Could even be used for planetwide electrical power distribution and seasonal energy storage.

ORDERS of magnitude easier than what you described. I started doing preliminary analysis on how big it'd need to be, cooling requirements, etc. It's really not that hard compared to getting Mars' surface pressure up beyond the Armstrong Limit.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline tdperk

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Re: ITS Radiation protection
« Reply #132 on: 10/16/2016 11:14 pm »
Why the heck would you do that???

To solve the habitability problem for a few billion year or so .

I might even add, "Duh."

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #133 on: 10/17/2016 01:54 am »
Why the heck would you do that???

To solve the habitability problem for a few billion year or so .

I might even add, "Duh."
Why'd you crop out the rest of my comment? Why the heck would you do that when the alternative is far cheaper and would work much better?

Mars would need active management to last that long no matter what, since it'd either be far too cold (now) or far too hot (to last beyond a billion years). A superconducting ring is FAR easier/cheaper/better to do and doesn't require scouring the solar system for every last scrap of radioactive isotope.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline guckyfan

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Re: ITS Radiation protection
« Reply #134 on: 10/17/2016 07:35 am »

Mars would need active management to last that long no matter what, since it'd either be far too cold (now) or far too hot (to last beyond a billion years). A superconducting ring is FAR easier/cheaper/better to do and doesn't require scouring the solar system for every last scrap of radioactive isotope.

To last beyond a billion years we should see Mars as a stepping stone where we learn the things we need to master living in space. We then can expand out into the asteroid belt and on to the kuiper belt and oort cloud. We should not waste effort to terraform Mars. It would be a detour for that goal.

I fully agree that active management of Mars would always be needed. Rekindling the core of Mars is way beyond our present capabilities. Before we can do that we have very likely already expanded beyond Mars and don't need it any more.

Edit: we seem to be slightly OT for ITS Radiation protection.
« Last Edit: 10/17/2016 07:37 am by guckyfan »

Offline mikelepage

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Re: ITS Radiation protection
« Reply #135 on: 10/17/2016 12:11 pm »
Edit: we seem to be slightly OT for ITS Radiation protection.
Back on topic, I haven't seen if anyone else has suggested this solution - I think it could work :)

The ITS animation showed solar panels poking out of the ship like Mickey Mouse ears, which suggests that the engines (or the nose, but probably engines) would be pointed towards the sun during the cruise Earth-Mars.  We also know Elon has suggested you could solve (some of) the radiation problem by putting a column of water between the crew and the sun.  We know that for the vast majority of the transit between Earth and Mars (in either direction) the methane and LOX tanks are going to be mostly empty - a place where you could put your "column of water" - BUT obviously you don't want water to contaminate any LOX/Propellent which is left.

So what if on the nose end of the inside of the LOX tank you had an expandable membrane that you could pump water into, and in the aft end of the crewed section, you have another expandable membrane that you store water inside for those times when the LOX tank has LOX in it.

The idea would be that at the beginning of each trip, during the trans-Mars injection burn and ascent/trans-Earth burns, the crew won't need that much room - they'll all be strapped into their acceleration couches at the nose of the ship, with a massive "water balloon" occupying most of the crew area behind them. Then as soon as the injection burn is finished, the other tanks are mostly empty, and all that water is pumped back through a valve into the membrane in the LOX tank, and the rest of the crew space becomes available for the crew to move about for the duration of the cruise.

At the beginning of each cruise you'd have maybe 10m of water between the crew and the sun, which would decrease as the crew consumed the water.  If some of the water is stored around the rim of the base of the crew quarters, that ought to be good for reducing the radation dose by at least half? right?

Not sure what material you would use for the membrane, but I'm imagining you would use whatever material it is they use for the hoses they pump the LOX into the tank in the first place.  The other problem I see is that you would tend to either freeze the water or boil the remaining oxygen -  not sure how they're planning to keep the oxygen liquid for 3 months anyway.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #136 on: 10/17/2016 01:01 pm »
10m by 12m cylinder is 1000tons of water. Nope.
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Offline tdperk

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Re: ITS Radiation protection
« Reply #137 on: 10/19/2016 09:29 am »
The ITS will spend a lot of time on Mars, on the surface.  The trip seems likely to mitigate radiation by being quick.  It may be radiation mitigation near term for the ITS will be, moving out of the ITS and underground.

It seems protecting the planet from radiation is a valid long term goal.

Probably longer term than non-museum usage of the ITS though.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #138 on: 10/19/2016 12:29 pm »
The ITS will spend a lot of time on Mars, on the surface.  The trip seems likely to mitigate radiation by being quick.  It may be radiation mitigation near term for the ITS will be, moving out of the ITS and underground.

The ITS will be a habitat only for the first one or two flights. The planet itself and its atmosphere will already provide a reduction of over 50%. After that they will have separate habitats. Those need to be designed for radiation protection. While the ITS servs as habitat they can use water for temporary radiation protection. They will have access to plenty of water and can fill water bags for additional temporary radiation protection.

Offline Vultur

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Re: ITS Radiation protection
« Reply #139 on: 10/22/2016 05:55 am »

In the "extreme sports" context, zero radiation protection is needed. None but the ship and Mars herself.

But if you want a colony and children, you need something better than nothing.

I am not sure that is even true. I agree this is what we must assume and work with in the beginning. But I would not be surprised at all if thorough long term research will show that we can live on the surface without any heavy shielding and without negative consequences.

Long term, IMO, 'low' (IE sub radiation sickness/sterility causing) levels of radiation will be irrelevant because we'll get something like a cancer vaccine or ultra-easy cancer treatment.

We could probably have this in 20 years in an environment where biotech could really hit its exponential curve. Due to regulatory limitations, probably more like 40-50 years away.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #140 on: 10/22/2016 06:19 am »
Long term, IMO, 'low' (IE sub radiation sickness/sterility causing) levels of radiation will be irrelevant because we'll get something like a cancer vaccine or ultra-easy cancer treatment.

We could probably have this in 20 years in an environment where biotech could really hit its exponential curve. Due to regulatory limitations, probably more like 40-50 years away.

That is another option. I did not think about this one. I was thinking that maybe it turns out that there is no need for any mitigation. GCR is high energy but quite low level. I don't think we have good tests on that kind of radiation environment to make good models for equivalent radiation effect on humans.

I think presently worst case models are used. That is reasonable but will be replaced with better models, once people have lived on Mars for a long enough time and animal tests have been done over several generations. After all people live on earth under radiation exposure exceeding recommendations and there seem to be no ill effects. But these populations may not be sufficiently observed yet so maybe not good comparison. Also the kind of radiation they are experiencing is different to GCR. So again not comparable.

Offline ThereIWas3

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Re: ITS Radiation protection
« Reply #141 on: 10/28/2016 11:23 pm »
I would worry more about micrometeorite damage with a thin carbon fiber skin.   Not just to people, but to engine plumbing.  (see the movie "Mission to Mars" starring Gary Sinéad)
Radiation might kill you in 10 years. Micrometeorites can kill you right now.

Offline Coastal Ron

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Re: ITS Radiation protection
« Reply #142 on: 10/28/2016 11:49 pm »
I would worry more about micrometeorite damage with a thin carbon fiber skin.   Not just to people, but to engine plumbing.  (see the movie "Mission to Mars" starring Gary Sinéad)
Radiation might kill you in 10 years. Micrometeorites can kill you right now.

I think for micrometeorites it's an odds thing, and even in the asteroid belt large items are truly very far apart.

As for movies, things are always far more likely to explode than physics would normally allow for, but just in case it appears SpaceX has pretty good sensors on their engines to monitor for problems.  And if anything potential damage during transit bolsters the idea that more engines are good, since you have more backups.

Note:  In "Mission to Mars", the actor you're thinking of is Gary Sinise.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline ThereIWas3

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Re: ITS Radiation protection
« Reply #143 on: 10/29/2016 04:07 am »
Note:  In "Mission to Mars", the actor you're thinking of is Gary Sinise.

Silly spelling corrector on my phone. :)

In the movie it was not the engines that got hit, but a fuel line.

Maybe best not to fly through meteor showers just the same.

Offline mikelepage

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Re: ITS Radiation protection
« Reply #144 on: 11/01/2016 03:53 am »
Long term, IMO, 'low' (IE sub radiation sickness/sterility causing) levels of radiation will be irrelevant because we'll get something like a cancer vaccine or ultra-easy cancer treatment.

We could probably have this in 20 years in an environment where biotech could really hit its exponential curve. Due to regulatory limitations, probably more like 40-50 years away.
Insert appropriately cynical comment here ::) yeah maybe, but we're actually going backwards in some medical pursuits (e.g. bacterial drug resistance) so assuming an exponential curve is a bit of a stretch.

Quote
That is another option. I did not think about this one. I was thinking that maybe it turns out that there is no need for any mitigation. GCR is high energy but quite low level. I don't think we have good tests on that kind of radiation environment to make good models for equivalent radiation effect on humans.

I think presently worst case models are used. That is reasonable but will be replaced with better models, once people have lived on Mars for a long enough time and animal tests have been done over several generations. After all people live on earth under radiation exposure exceeding recommendations and there seem to be no ill effects. But these populations may not be sufficiently observed yet so maybe not good comparison. Also the kind of radiation they are experiencing is different to GCR. So again not comparable.

The annual exposure from background sources for everyone is around 2-4mSv.  Above 100mSv annual exposure where the data becomes conclusive regarding increased cancer risk.  Between 4 and 100mSv is where it's fuzzy: we can probably take considerably more than 4, but with the knowledge we have now, we know we should stay below 100 if we want to be safe on a long-term basis.  (ISS astronauts receive 160mSv in 6 months or 320mSv per year).

Curiosity measured 1.8mSv per day (657mSv per year) in interplanetary space, and living on the surface of Mars would cut that down by half (equivalent to ISS), so we're really only talking about 2 to 3 halving thicknesses of whatever passive shielding material you're using before we get down into the <100mSv/year region (1/28* 657 = 82mSv/year), where we're as likely as not to be okay.

For the highest energy GCR the halving thickness of water is about 18cm (~7"), so having about 0.5 m of water as shielding (not the 10m I said earlier), should be enough to get use down into sub 100mSv/annual exposure range.

If 100 people on an ITS crew vehicle are allocated 1 ton of water each (4kg per person per day including reuse), incorporating that into an envelope around the crew vehicle would allow you to achieve that 0.5m thickness for 200 square metres.  If you created a cylindrical envelope tank around the edge of the crew vehicle with a diameter of ~15m, your envelope could be ~4m tall.  It's not enough to cover the whole crew vehicle, but with some good design you should be able to get total exposure down close to where we need it long term.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #145 on: 11/01/2016 04:06 am »
Halving thicknesses work for gamma rays and X-rays. Not for GCR.
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Offline Burninate

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Re: ITS Radiation protection
« Reply #146 on: 11/01/2016 06:36 pm »
If 100 people on an ITS crew vehicle are allocated 1 ton of water each (4kg per person per day including reuse), incorporating that into an envelope around the crew vehicle would allow you to achieve that 0.5m thickness for 200 square metres.

An estimate that cuts closer to what we suspect would be that each crew member will be allocated ~2kg/person/day of solid food, mostly dehydrated (this is 10% below the ISS), plus a buffer of 20kg of drinking water.  The primary source of drinking water will be the ECLSS, processing water vapor and urine;  The human body produces excess water in a fairly closed system because the chemical reactions in glucose metabolism turn glucose and oxygen into water and CO2.

Normally we lose enough water to exhalation, sweat, and urine that our food consumption is not also an adequate supply of water, but this assumption does not hold in an advanced spacecraft ECLSS whose waste products are carbon monoxide and a thick wastewater brine.  It can recycle enough water that the hydrogen & carbon content of the food is sufficient to keep the whole system cycling and replace the losses.

Offline Vultur

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Re: ITS Radiation protection
« Reply #147 on: 11/02/2016 03:32 am »
Insert appropriately cynical comment here ::) yeah maybe, but we're actually going backwards in some medical pursuits (e.g. bacterial drug resistance) so assuming an exponential curve is a bit of a stretch.

Antibiotic resistance isn't comparable since the bacteria are actively evolving. Radiation hazards/cancer don't work that way.

And I'm not really assuming an exponential curve. We're probably not going to see the huge life expectancy rises of the early-mid 20th century again, since all the "low-hanging fruit" (vaccination, sanitation, antibiotics) is already done, sure.

But we're talking about decades. (And things will likely speed up compared to now, as biotech gets cheaper & more countries/facilities/people get seriously involved in working on it. Especially since a lot of those countries will have regulations much less restrictive than the US FDA.)

Offline RonM

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Re: ITS Radiation protection
« Reply #148 on: 11/02/2016 03:52 am »
I think we'd be better off counting on old fashioned engineering than future medical developments. A few decades back people thought we would have cured cancer and had fusion reactors by now.

Offline mikelepage

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Re: ITS Radiation protection
« Reply #149 on: 11/02/2016 07:00 am »
Halving thicknesses work for gamma rays and X-rays. Not for GCR.

My mistake.  And I see I'm not the first person to be caught out by the stupidity of GCRs being called a "ray".

Still, I don't think that changes the conclusion that the best geometry with which to arrange water for passive shielding around the ITS crew vehicle is in a cylinder of some kind?  Attenuation may not be logarithmic, but once you get past a certain thickness, thicker is better right?  What is that thickness?

Insert appropriately cynical comment here ::) yeah maybe, but we're actually going backwards in some medical pursuits (e.g. bacterial drug resistance) so assuming an exponential curve is a bit of a stretch.

Antibiotic resistance isn't comparable since the bacteria are actively evolving. Radiation hazards/cancer don't work that way.

Well true, but the cancer problem is many orders of magnitude more complex.  Hence my cynicism.

As my cancer lecturer once put it to us:
"cancer is our name for the state in which some cells in a multicellular organism revert to being single celled organisms."

Important to emphasise that there is nothing fundamentally "unnatural" about cancer cells.  They can still be perfectly viable cells (if you put them into culture in a lab they live just about forever), and they possess all the immune markers of "self", same as that every other cell in that organism.  It's just that those cells have had damage to the mechanisms which allow them to play nice with all the cells around them.  Which is bad for any multicellular organism that happens to host them.

You've somehow got to get immune cells to stop paying attention to all the signals they're receiving telling them to "leave this cell alone" and get them to attack it.  It's possible there might turn out to be some silver bullet with foreseeable tech, but I think it will probably take the singularity/much more advanced nanotech that can physically dispatch cancer cells on a cell-by-cell basis, before it is no longer a life-threatening condition.  In the meanwhile, better to plan to avoid getting cooked by GCRs etc.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #150 on: 11/02/2016 12:21 pm »
There's been tremendous progress already with fighting leukemia with immunotherapy related techniques.

It's easier to imagine engineering fixes to a lot of the problems of human spaceflight, but I think long-term biomedical advances will play an enormous role. Biology is exceedingly complex, which makes even "simple" problems like obesity difficult to solve, but it also means there's enormous potential for improvement without breaking any physical laws.
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Offline DOCinCT

Re: ITS Radiation protection
« Reply #151 on: 11/02/2016 06:44 pm »
(Haven't been able to read all posts here, but...)
There is a fair amount of research going back over a decade on the effectiveness of carbon based (composites and polymers) radiation shielding.  So maybe the use of carbon fiber wrapped structures is not just for construction purposes or weight loss??  No real need for magnetic fields or water tanks etc.

Offline Burninate

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Re: ITS Radiation protection
« Reply #152 on: 11/02/2016 07:51 pm »
(Haven't been able to read all posts here, but...)
There is a fair amount of research going back over a decade on the effectiveness of carbon based (composites and polymers) radiation shielding.  So maybe the use of carbon fiber wrapped structures is not just for construction purposes or weight loss??  No real need for magnetic fields or water tanks etc.

Nope.  Carbon fiber, hydrocarbons like plastic & food, and water are going to provide very similar levels of shielding per mass - all moderately better than aluminum, but not better enough to matter all that much.  Purpose-built shielding is a non-starter, mass used for shielding should be mass you're already taking along for the mission for other reasons.

And the necessary mass to realistically shield against substantial amounts (think 99% or 90%, not 20%) of GCR radiation is going to be ridiculously large.  The necessary mass to shield against a solar storm is more reasonable, largely because you can shield a closet-sized area for a short period using a minimum of surface area, while shielding the whole hab is prohibitively heavy;  It's also much more practical in a very large-scale spacecraft because of the sphere-cube ratio than it is in something Dragon/Orion-sized.  Lastly, the type of radiation in solar storms is much less penetrative than the cosmic ray particulate hits.

We're just going to have to live with GCRs, for the most part.
« Last Edit: 11/04/2016 03:38 am by Burninate »

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #153 on: 11/02/2016 08:29 pm »
Actually significantly better than aluminum since a thin aluminum structure actually generates enough secondaries to make GCR worse than nothing at all. Composites don't really do that. And add in some food near sleeping quarters and you can measurably reduce the dose.
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Offline LMT

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Re: ITS Radiation protection
« Reply #154 on: 11/04/2016 04:21 am »
Mini-Magnetosphere for Proton Shielding

Can I ask for a consensus as to whether Magnetic or other shielding techniques (outside of the physical barrier type), are feasible in the next 10-20 years, on a scale to protect ITS sized space craft in Space.

There's been some related research recently in artificial mini-magnetospheres.  Bamford et al. suggest mini-magnetosphere protection from solar protons, as a first application.  However they emphasize the complexity of mini-magnetosphere behavior in the natural plasma environment.

Offline LMT

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Re: ITS Radiation protection
« Reply #155 on: 11/04/2016 04:32 am »
Crew Radiation Exposure Estimates

Cross-posting for relevance:  McGirl et al. 2016, "Crew Radiation Exposure Estimates from GCR and SPE Environments During a Hypothetical Mars Mission".

In the study, female crew members under 40 approach their lifetime 3% risk limit, even on a single-synod mission with 500-day stay.  That's at -7000 m elevation, beneath 15 cm of aluminum shielding.

If we add the extra risk of poorly-understood HZE particle effects, possibly most crew members approach the 3% limit, and are restricted to one single-synod mission.

Offline guckyfan

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Re: ITS Radiation protection
« Reply #156 on: 11/04/2016 04:51 am »
If we add the extra risk of poorly-understood HZE particle effects, possibly most crew members approach the 3% limit, and are restricted to one single-synod mission.

My reply on that threa:

Quote
Sievert are a weighted metric for biologic effects and include the higher risk due to high energy particles. As the effects of high energy particles are not very well known, it is a safe assumption that the effects are not undervalued. Much more likely they are overvalued as a cautionary measure.

Also the mention of lifetime doses makes me think they use the obsolete Linear No Threshold.

Offline MikeAtkinson

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Re: ITS Radiation protection
« Reply #157 on: 11/04/2016 07:09 am »
Crew Radiation Exposure Estimates

Cross-posting for relevance:  McGirl et al. 2016, "Crew Radiation Exposure Estimates from GCR and SPE Environments During a Hypothetical Mars Mission".

In the study, female crew members under 40 approach their lifetime 3% risk limit, even on a single-synod mission with 500-day stay.  That's at -7000 m elevation, beneath 15 cm of aluminum shielding.

The study is for aluminium shielding and 200 day transits - so not particularly relevant for ITS which uses carbon fiber composites and 90-120 day transits.

The study also has no shielding from crew supplies, all recent designs have used water, food and waste to give extra shielding and ITS will be no exception.

On Mars it seems likely that most crew time will be spent under considerable regolith shielding, with EVA and pressurised rover time the major source of radiation exposure.

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #158 on: 11/04/2016 12:36 pm »
Mini-Magnetosphere for Proton Shielding

Can I ask for a consensus as to whether Magnetic or other shielding techniques (outside of the physical barrier type), are feasible in the next 10-20 years, on a scale to protect ITS sized space craft in Space.

There's been some related research recently in artificial mini-magnetospheres.  Bamford et al. suggest mini-magnetosphere protection from solar protons, as a first application.  However they emphasize the complexity of mini-magnetosphere behavior in the natural plasma environment.
Yeah, the problem with these magnetic shields is that realistic designs do not shield against GCR, just SPEs, which we already can shield against effectively using repositioned supplies at no extra mass.

I think there's a use for this long-term. a very large shield over a Mars city would also provide energy storage. A ring around the whole planet would be possible, too, and would also serve for power distribution. But it just doesn't trade well for spacecraft. But this may change if we develop much better superconductors.
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Offline LMT

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Re: ITS Radiation protection
« Reply #159 on: 11/04/2016 02:09 pm »
Mini-Magnetosphere for Proton Shielding

Can I ask for a consensus as to whether Magnetic or other shielding techniques (outside of the physical barrier type), are feasible in the next 10-20 years, on a scale to protect ITS sized space craft in Space.

There's been some related research recently in artificial mini-magnetospheres.  Bamford et al. suggest mini-magnetosphere protection from solar protons, as a first application.  However they emphasize the complexity of mini-magnetosphere behavior in the natural plasma environment.
Yeah, the problem with these magnetic shields is that realistic designs do not shield against GCR, just SPEs, which we already can shield against effectively using repositioned supplies at no extra mass.

I don't know how you're getting that statement from the paper - or how you judge what's realistic (references always help) - but the authors do emphasize that this particular shield would be more effective than some others because it is not blocking, but "refractive".  In this shield, cross field currents give a refractive "3D safe zone effective against both directional and omni-directional threats". 

Net net:  SCR protection is the first application, but there would also be a measure of protection from GCRs with energies topping out, theoretically, somewhere in the 100 MeV to 1 GeV range.  That would actually cover many GCRs.  The authors note that GCR particles at GeV energies have flux "six orders of magnitude less" than SCRs.  Also we can note that the highest GCR flux is at lower energies, ~100 MeV.  Fig. 5.7.2.1.2-1 Space Radiation Environment.



« Last Edit: 12/14/2016 06:10 pm by LMT »

Offline Robotbeat

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Re: ITS Radiation protection
« Reply #160 on: 11/04/2016 02:32 pm »
Yes, and by the same token you can block lower energy GCRs with passive shielding, too.

we're concerned with the hard to block high energy GCRs as even if they have lower flux they have higher energy.
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Offline LMT

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Re: ITS Radiation protection
« Reply #161 on: 11/04/2016 03:07 pm »
we're concerned with the hard to block high energy GCRs as even if they have lower flux they have higher energy.

There's a big difference between "no shield" against GCR particles and shielding against 90%+ of the particle flux.  That's the correction.



So tell us more about that artificial planetary magnetic ring and its global power distribution scheme.  You have designs on martian superconductor production?
« Last Edit: 12/14/2016 06:42 pm by LMT »

Offline philw1776

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Re: ITS Radiation protection
« Reply #162 on: 11/04/2016 03:47 pm »
Even 80/20 rule improvement would be a huge gain over problematic aluminum.
Combine that with fast transit and then underground regolith shielded sleeping quarters on Mars and it's a huge exposure reduction over prior approaches.
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