Starches as Radiation Shielding

[cubinator]

The other day I was reheating some food in the microwave for dinner, and I noticed (yet again) that my beans were still not very warm. I started thinking about how they don't absorb the heat energy from the microwaves as much as other food does, and they have a lot of starch, and then I wondered: Could starch be a good material for radiation shielding? Today I googled it, and the second result was from NASA! Here it is:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120006695.pdf

So a starch-based material would be a very potent radiation shield, and it could be grown in space! I thought it was pretty interesting.  What else do you know on the topic?

[Shpaget]

I would assume that non heating of the food is the result of that food being transparent to microwave radiation, not opaque.

A shield needs to be opaque, meaning it stops all (or most of) the radiation. If it stops radiation, it needs to absorb the energy in that radiation, and that means heat.

Or is it reflective? in that case, the radiation would just bounce around in the oven until it hits something that can absorb the microwaves.

[cubinator]

17 minutes ago, Shpaget said:

Or is it reflective? in that case, the radiation would just bounce around in the oven until it hits something that can absorb the microwaves.

I think it's reflective, considering the NASA report says it's a great thermal insulator too.

[DBowman]

I think though microwaves are not your biggest issue. From my reading I think the big problem (that you can do something about, forget about cosmic rays) is high energy/velocity protons from 'solar proton events'. The best shielding for that is low atomic mass elements - so hydrogen. But for 'convenience' (low volume, non cryo) you have to settle for some 'high H' molecules and maybe a something you'd be carrying anyway; e.g. H2O and CH4 kind of fit that bill. Starches are carbon polymers, so 'on average' CH2. I'd expect starches and sugars to be useful but not ideal in themselves, as part of all the payload trade-offs they might be pretty good - and the waste they generate from consumption is probably good also (H2O and ???) so you can consume them without totally removing your shielding. 

[cubinator]

@DBowman The paper did say the starch also had a plasticizer in it, and those two together made for a really robust shield that can be grown in space. Starch alone, I presume, would not work as well but still be somewhat effective. And I'm not worried about microwaves in long space missions, I just mentioned it because that's how I got the idea to look it up. 

[Bill Phil]

7 hours ago, cubinator said:

The other day I was reheating some food in the microwave for dinner, and I noticed (yet again) that my beans were still not very warm. I started thinking about how they don't absorb the heat energy from the microwaves as much as other food does, and they have a lot of starch, and then I wondered: Could starch be a good material for radiation shielding? Today I googled it, and the second result was from NASA! Here it is:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120006695.pdf

So a starch-based material would be a very potent radiation shield, and it could be grown in space! I thought it was pretty interesting.  What else do you know on the topic?

Anything with a lot of hydrogen (or atoms in general) is more resistant to radiation. But, if I recall, microwaves heat things up by inciting friction...?

[DBowman]

3 hours ago, cubinator said:

@DBowman The paper did say the starch also had a plasticizer in it, and those two together made for a really robust shield that can be grown in space. Starch alone, I presume, would not work as well but still be somewhat effective. And I'm not worried about microwaves in long space missions, I just mentioned it because that's how I got the idea to look it up. 

ah interesting - I should read the paper I guess! it sounds like they are not planing to eat it and then use the poop.

44 minutes ago, Bill Phil said:

if I recall, microwaves heat things up by inciting friction...?

fwiw here is my mental model: Molecules are like little masses joined by springs. They have resonant frequencies, some frequencies you shake them at will damp out the energy but the resonant ones will amp up any oscillation of the springs (like pushing someone on a swing, the length of the 'hang' determines the frequency you have to push at). The 'spring's are 'good at' absorbing photons of particular frequencies and converting that energy into various motions of the masses joined to the spring, intra molecular motion if you like. If you have molecules waggling and bumping into each other then some 'waggle energy' will get converted to 'whole molecule motion' = heat by collisions of bits of molecules (is this 'friction'? even the waggle might be heat). Microwaves are tuned/chosen to resonate with H2O, so they directly heat the water. The heating they do to conductors is via a different mechanism, like an antenna picking up energy?

[kerbiloid]

Potato is made of starch.

So, 2-3 t of potatoes placed around the cabin would provide both radiation shielding and food supply.

Mark Watney recommends.

[Bill Phil]

5 minutes ago, kerbiloid said:

Potato is made of starch.

 

That, and a bunch of other good and healthy stuff!

[SinBad]

Starch, sugars, even fats and proteins are all full of hydrogen and mixtures of them are usually rather easy to shape and cure (bake?).

Ginger bread house on the moon.

Shortbread solar sailers

Can't wait to see what nasa cooks up with this.

[kerbiloid]

Also, its true Kerbal: to fly inside a giant can of beans & potatoes puree, eating it from the middle.

[lajoswinkler]

Microwave oven radiation is nonionizing electromagnetic radiation, microwave photons. They heat stuff.

Stuff you want to block in outer space is cosmic rays (extreme gamma rays, protons, electrons, neutrons, ...), gamma rays, x-rays. Ionizing radiation. They strip electrons from atoms and molecules, creating ions and radicals that wreck our body's cellular proteins and other stuff.

 

Two completely different things.

[Bill Phil]

11 minutes ago, lajoswinkler said:

Microwave oven radiation is nonionizing electromagnetic radiation, microwave photons. They heat stuff.

Stuff you want to block in outer space is cosmic rays (extreme gamma rays, protons, electrons, neutrons, ...), gamma rays, x-rays. Ionizing radiation. They strip electrons from atoms and molecules, creating ions and radicals that wreck our body's cellular proteins and other stuff.

 

Two completely different things.

Very correct. However, starches are large molecules, and they consist partly of hydrogen and carbon, which can help against neutron radiation. It's not very effective against most ionizing radiation, though. But it's likely that the sheer mass in a thick enough layer would do some good. Depends on the halving thickness of the starch you use...

Edited June 23, 2016 by Bill Phil

[kerbiloid]

2 hours ago, Bill Phil said:

and they consist partly of hydrogen and carbon, which can help against neutron radiation

And if grow the potato watering them with heavy water, they additionally can use it in the ship reactor as a moderator.
From time to time scooping a new portion of hot fried potatoes with a long spoon.

[lajoswinkler]

1 hour ago, kerbiloid said:

And if grow the potato watering them with heavy water, they additionally can use it in the ship reactor as a moderator.
From time to time scooping a new portion of hot fried potatoes with a long spoon.

Potatos won't grow in heavy water. Enzymes are highly sensitive to small differences in hydrogen atom size.

[p1t1o]

I think, correct me if Im wrong, but when it comes to radiation shielding, its the type of atoms you have that matter, and not how they are bonded to each other. There is no magical compound that is better at shielding than another compound with the same density and atomic makeup, chemical bonding doesn't play a part. The sort of radiation that is absorbed by chemical bonds will be of too long a wavelength to be dangerous. I think.

Anyway, starch has quite a lot of carbon, and I've never heard carbon being a great shield for anything (other than thermal). Its probably ok-ish, in that it is mass between you and the radiation, but its too heavy to be an efficient neutron absorber and not heavy enough to be an efficient gamma/X-ray absorber. I think.

If you do have a lot of starch on board for some other reason though, storing it in between the crew and space will be of some benefit.

Edited June 23, 2016 by p1t1o

[cubinator]

7 hours ago, lajoswinkler said:

Two completely different things.

I realize that, I just noticed that starch doesn't absorb microwave energy very well, and I wondered if that applied to other types of radiation as well. The paper I linked seems to indicate it does a reasonable job protecting against both.

3 hours ago, p1t1o said:

Snip

Starch also has a lot of hydrogen, which I hear offers very good protection against ionizing radiation, thus explaining how it can be shielding to both ionizing and non-ionizing radiation.

[p1t1o]

1 minute ago, cubinator said:

Starch also has a lot of hydrogen, which I hear offers very good protection against ionizing radiation, thus explaining how it can be shielding to both ionizing and non-ionizing radiation.

Its actually only about 6% hydrogen by mass, as opposed to say water, which is 11% hydrogen by mass and then there is polyethylene (or other hydrocarbon polymers), which approach ~16.7% hydrogen.

Starch may have utility as a sort of "multi-use" raw material, where it could contribute to shielding, but if we are talking "What makes an optimal material for space radiation shielding?" I don't think starch makes a great choice.

I read the link provided, which does indicate it has some utility, but it speaks mainly of stability and absorption cross-section is not discussed. As a heatshield it sounds more promising, as when you look at it, it is structurally fairly similar to the phenolics used in current heatshields.

[cubinator]

20 minutes ago, p1t1o said:

Its actually only about 6% hydrogen by mass, as opposed to say water, which is 11% hydrogen by mass and then there is polyethylene (or other hydrocarbon polymers), which approach ~16.7% hydrogen.

Starch may have utility as a sort of "multi-use" raw material, where it could contribute to shielding, but if we are talking "What makes an optimal material for space radiation shielding?" I don't think starch makes a great choice.

I read the link provided, which does indicate it has some utility, but it speaks mainly of stability and absorption cross-section is not discussed. As a heatshield it sounds more promising, as when you look at it, it is structurally fairly similar to the phenolics used in current heatshields.

I think the main advantage of starch is that it could be grown in-situ, so you wouldn't need to carry your heat shield/radiation shield during launch, allowing for either a bigger payload or smaller rocket. 

[p1t1o]

Just now, cubinator said:

I think the main advantage of starch is that it could be grown in-situ, so you wouldn't need to carry your heat shield/radiation shield during launch, allowing for either a bigger payload or smaller rocket. 

Yeah, I don't understand that part. Grown from what? Space-soil? You're gonna have to lift all the raw materials. I suppose you might one day grow it in lunar or martian soil (???) but then you have to carry all the water there anyway, soooo?

[lajoswinkler]

Starch would be a poor cosmic ray absorber. It's best to just use water.

[cubinator]

6 minutes ago, p1t1o said:

Yeah, I don't understand that part. Grown from what? Space-soil? You're gonna have to lift all the raw materials. I suppose you might one day grow it in lunar or martian soil (???) but then you have to carry all the water there anyway, soooo?

Yeah, you'd probably be better off using your fuel tanks as radiation shielding.

[RainDreamer]

Side question: is irraditated potato safe to eat?

[cubinator]

Just now, RainDreamer said:

Side question: is irraditated potato safe to eat?

If it's irradiated with microwaves, it is definitely unsafe and should not be consumed, breathed, or looked at.

[RainDreamer]

I supposed if mark watney can eat it, we can. Maybe he has that lead belly perk from fall out.