Mars Radiation

[Robotbeat]

There’s no advantage to using Boron-11 instead of polyethylene.

There's no advantage to intentionally adding additional boron-11 instead of polyethylene. Yes that's true.

There is however an advantage to not removing (at great expense!) that last little bit of boron-11 from your already-pretty-enriched boron-10 product. The advantage is cost.

There is a mass advantage to doing it versus natural boron. If you mean using 95% B10 instead of 99.9%B10, then sure, small benefit from going to 99.9%.

…

Boron-11 could be used for any interior applications calling for boron, ..

Boron is not a common structural material (although Shuttle used it). So your comment doesn’t make much sense. Why would you be using Boron if not for its ability to mop up neutrons?

(And no, having a low cross section isn’t an advantage in this case, either.)

[Twark_Main]

There’s no advantage to using Boron-11 instead of polyethylene.

There's no advantage to intentionally adding additional boron-11 instead of polyethylene. Yes that's true.

There is however an advantage to not removing (at great expense!) that last little bit of boron-11 from your already-pretty-enriched boron-10 product. The advantage is cost.

There is a mass advantage to doing it versus natural boron.

My point is that at Starship level launch costs, this advantage does seem to be far outweighted by the cost of isotope separation.

If you mean using 95% B10 instead of 99.9%B10, then sure, small benefit from going to 99.9%.

I mean precisely that you shouldn't do that.

The cost of 99.9% isotopic purity would be astronomical. Far better to just "bite the bullet" and launch a slightly larger quantity boron with lower enrichment.

Regular boron is only 20% boron-10. Even 95% boron-10 is already considered a high level of enrichment, and is almost certainly uneconomic given Starship launch costs. 99.9% is just plain ridiculous.

…

Boron-11 could be used for any interior applications calling for boron, ..

Boron is not a common structural material (although Shuttle used it). So your comment doesn’t make much sense. Why would you be using Boron if not for its ability to mop up neutrons?

Did I stutter? "Any" applications.   I intentionally didn't specify, because we can't necessarily predict it ahead of time.

This includes, apparently, what you wrote in bold. So to borrow a phrase your comment doesn’t make much sense.    Always nice when people answer their own question however!

Yes if you need to build a neutron absorber assembly inside the shielded hab (not sure why you'd do that, vs simply locating your radiation source outside the GCR shield) then obviously you're not going to use boron-11. But if all you need is the chemical properties of boron (fire retardants etc) then you should consider whether to use depleted boron.

(And no, having a low cross section isn’t an advantage in this case, either.)

Oh sorry, I thought you'd read the article (at least the relevant sections) when I linked to it.

https://en.wikipedia.org/wiki/Boron#Radiation-hardened_semiconductors

[Robotbeat]

There’s no advantage to using Boron-11 instead of polyethylene.

There's no advantage to intentionally adding additional boron-11 instead of polyethylene. Yes that's true.

There is however an advantage to not removing (at great expense!) that last little bit of boron-11 from your already-pretty-enriched boron-10 product. The advantage is cost.

There is a mass advantage to doing it versus natural boron.

My point is that at Starship level launch costs, this advantage does seem to be far outweighted by the cost of isotope separation.

If you mean using 95% B10 instead of 99.9%B10, then sure, small benefit from going to 99.9%.

I mean precisely that you shouldn't do that.

The cost of 99.9% isotopic purity would be astronomical. Far better to just "bite the bullet" and launch a slightly larger quantity boron with lower enrichment.

Regular boron is only 20% boron-10. Even 95% boron-10 is already considered a high level of enrichment, and is almost certainly uneconomic given Starship launch costs. 99.9% is just plain ridiculous.


…

Yes, I pretty clearly was *acknowledging* this.

[Twark_Main]

I'll take yes for an answer. 

I was surprised at the level of controversy over (what I considered to be) a set of relatively uncontroversial statements about boron shielding. Looks like just "loudly agreeing with each-other" in this case.

[Robotbeat]

Yup, many such case.

I do want to point out that even if the costs are fairly high per unit mass, in some cases there are other mass considerations. I'm thinking of enriched Boron-10 for use on a radiation protection vest. At very low altitudes of Mars, 1 inch of polyethylene shielding (i.e. like a vest) gets you 0.45mSv/day dose but 1inch of Boron-10 gets you 0.35mSv/day dose. Might cost a million dollars, but that's probably cheap if it reduces the dose by ~100mSv, allowing you to reduce transit speed dramatically.

[Twark_Main]

Haha agreed. The vest is an interesting case, thanks.

Times of Israel had a good article on the AstroRad vest from Artemis 1. No boron as far as I know, but it does have polyethylene with variable thickness to best protect individual organs. See Paige, Newman & Lombardo 2020.

https://www.timesofisrael.com/israels-stemrad-gears-up-for-major-demo-of-anti-radiation-suit-on-nasas-artemis-i/

https://ieeexplore.ieee.org/abstract/document/9172794




EDIT Also good news everyone, our new excuse just dropped. "I'm not fat, I'm self-shielded."   

[LMT]

At very low altitudes of Mars, 1 inch of polyethylene shielding (i.e. like a vest) gets you 0.45mSv/day dose but 1inch of Boron-10 gets you 0.35mSv/day dose.

Bare skin gets ~ 0.34 mSv/day, as we saw in thread.   

[Robotbeat]

At very low altitudes of Mars, 1 inch of polyethylene shielding (i.e. like a vest) gets you 0.45mSv/day dose but 1inch of Boron-10 gets you 0.35mSv/day dose.

Bare skin gets ~ 0.34 mSv/day, as we saw in thread.   

Yeah, you’re right, but our values are not inconsistent. I was looking at -5km altitude, Hellas Basin is greater depth than that, altitude of -7km or lower.

[LMT]

At very low altitudes of Mars, 1 inch of polyethylene shielding (i.e. like a vest) gets you 0.45mSv/day dose but 1inch of Boron-10 gets you 0.35mSv/day dose.

Bare skin gets ~ 0.34 mSv/day, as we saw in thread.   

Yeah, you’re right, but our values are not inconsistent. I was looking at -5km altitude, Hellas Basin is greater depth than that, altitude of -7km or lower.

Notice your own post, and quantify the actual shielding effect.

[Robotbeat]

? How are we even in disagreement?

[Lampyridae]

? How are we even in disagreement?

Even moreso when you consider the variation of cosmic radiation flux over years and decades.

Yup, many such case.

I do want to point out that even if the costs are fairly high per unit mass, in some cases there are other mass considerations. I'm thinking of enriched Boron-10 for use on a radiation protection vest. At very low altitudes of Mars, 1 inch of polyethylene shielding (i.e. like a vest) gets you 0.45mSv/day dose but 1inch of Boron-10 gets you 0.35mSv/day dose. Might cost a million dollars, but that's probably cheap if it reduces the dose by ~100mSv, allowing you to reduce transit speed dramatically.

This paper suggests a price of $45/g for 99% B-10. Comparable to gold. So a square metre of 5g/cm^2 Boron-10 works out to $2.25 million.

Boron-10 carbide seems a lot cheaper for some reason, and it's 80% boron atoms.

[spacenut]

Rovers can be shielded.  Robotic arms can be used off rovers.  Rovers can be shielded heavier.  Only go outside when necessary, otherwise stay in rovers and in habitats.  In the future of a Mars colony, satellites can provide shielding by creating a radiation belt like the Van-Allen belt on earth.  These same satellites might be able to do double duty by being similar to Starlinks for communication.  Satellites might be placed in the Mars-Sun LaGrange point to deflect radiation from the sun.  There are many options.  Polyethylene is cheap, and lightweight.  Is boron heavy?  I know it can be expensive and the carbon based boron molecule would be heavier.  Then, Mars is 0.38 earths gravity, so what might be heavy on earth would be lighter on Mars. 

[Slarty1080]

Rovers can be shielded.  Robotic arms can be used off rovers.  Rovers can be shielded heavier.  Only go outside when necessary, otherwise stay in rovers and in habitats.  In the future of a Mars colony, satellites can provide shielding by creating a radiation belt like the Van-Allen belt on earth.  These same satellites might be able to do double duty by being similar to Starlinks for communication.  Satellites might be placed in the Mars-Sun LaGrange point to deflect radiation from the sun.  There are many options.  Polyethylene is cheap, and lightweight.  Is boron heavy?  I know it can be expensive and the carbon based boron molecule would be heavier.  Then, Mars is 0.38 earths gravity, so what might be heavy on earth would be lighter on Mars.

Is a satellite based artificial Van-Allen radiation belt a realistic possibility? It sounds highly suspect to me (but I would love to be proved wrong). The density of boron is greater than than of polyethylene, but presumably it is more effective at absorbing radiation than polythene gram for gram.

It is true that they would weigh less on Mars, but they would both be launched from Earth for the foreseeable future so It wouldn't make any difference. Longer term polyethylene could fairly easily be produced on Mars, but Boron would be a lot harder to source/extract locally.

[Robotbeat]

The Van Allen Belt doesn’t provide shielding. The Earth’s magnetic field does.

[Twark_Main]

The Van Allen Belt doesn’t provide shielding.

That's not exactly true.

https://www.researchgate.net/publication/270653683_An_impenetrable_barrier_to_ultra-relativistic_electrons_in_the_Van_Allen_Radiation_Belt

https://scitechdaily.com/van-allen-probes-reveal-impenetrable-barrier-space/

[Greg Hullender]

The Van Allen Belt doesn’t provide shielding. The Earth’s magnetic field does.

I think he's talking about the idea proposed in How to create an artificial magnetosphere for Mars" (R.A. Bamford et al, Acta Astronautica, Volume 190, January 2022, Pages 323-333). The idea is to create an artificial Van Allen belt of charged particles and then to run an electrical current through that loop, generating a magnetic field. (See section 8, starting on page 16.)

Plasma structures such as radiation belts naturally occur around planets like the Earth. In these cases, the co-rotating ions and electrons are formed as a result of the rotation of the planet and complex interactions of its natural magnetic field. Here we do the opposite, artificially driving a current in a plasma torus to create a resultant magnetic field.

[Twark_Main]

The Van Allen Belt doesn’t provide shielding. The Earth’s magnetic field does.

I think he's talking about the idea proposed in How to create an artificial magnetosphere for Mars" (R.A. Bamford et al, Acta Astronautica, Volume 190, January 2022, Pages 323-333). The idea is to create an artificial Van Allen belt of charged particles and then to run an electrical current through that loop, generating a magnetic field. (See section 8, starting on page 16.)

Plasma structures such as radiation belts naturally occur around planets like the Earth. In these cases, the co-rotating ions and electrons are formed as a result of the rotation of the planet and complex interactions of its natural magnetic field. Here we do the opposite, artificially driving a current in a plasma torus to create a resultant magnetic field.

Anyone care to comment on whether this is more or less difficult than the "standard" buried superconducting loop plan?

https://inis.iaea.org/collection/NCLCollectionStore/_Public/40/084/40084971.pdf

Clearly the buried conductors plan requires more work to build the "wires," but for the other parts of the system the relative feasibility is less clear.

[Robotbeat]

The Van Allen Belt doesn’t provide shielding. The Earth’s magnetic field does.

I think he's talking about the idea proposed in How to create an artificial magnetosphere for Mars" (R.A. Bamford et al, Acta Astronautica, Volume 190, January 2022, Pages 323-333). The idea is to create an artificial Van Allen belt of charged particles and then to run an electrical current through that loop, generating a magnetic field. (See section 8, starting on page 16.)

Plasma structures such as radiation belts naturally occur around planets like the Earth. In these cases, the co-rotating ions and electrons are formed as a result of the rotation of the planet and complex interactions of its natural magnetic field. Here we do the opposite, artificially driving a current in a plasma torus to create a resultant magnetic field.

Anyone care to comment on whether this is more or less difficult than the "standard" buried superconducting loop plan?

https://inis.iaea.org/collection/NCLCollectionStore/_Public/40/084/40084971.pdf

Clearly the buried conductors plan requires more work to build the "wires," but for the other parts of the system the relative feasibility is less clear.

I think Jim Greene's orbital magnetosphere plan is less effective than burying wires. Burying wires can also act as a global energy storage and distribution system for Mars.

[Lampyridae]

FYI, there is finally a paper on active + passive radiation shielding.

https://www.sciencedirect.com/science/article/pii/S2214552423000391

What's interesting is that they were able to compute a simple scaled reduction factor for the various ions and energies and then feed them into HZTERN. Hopefully NASA can implement this feature with OLTARIS if we agitate enough.

Note: this is for electrostatic shielding, which isn't going to be great for Mars surface and its low pressure, dusty, highly conductive atmosphere.

[LMT]

Note: this is for electrostatic shielding, which isn't going to be great for Mars surface and its low pressure, dusty, highly conductive atmosphere.

I think it can't work there at all, no.  Electrical conductivity is ~ 2 orders of magnitude higher than Earth's.  The shield would discharge far below the required electric potential.