Author Topic: Crystal Grains Store Large Amounts of Oxygen  (Read 7206 times)

Offline sanman

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Crystal Grains Store Large Amounts of Oxygen
« on: 10/07/2014 03:04 am »
A new material has been found to store large quantities of oxygen through selective chemisorption:

http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder/2014_09_30_iltsluger


People are talking about it for food packing (ie. sucking away the oxygen), and even scuba diving. But could it be similarly useful for extending astronaut EVAs?

Offline Lee Jay

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #1 on: 10/07/2014 03:19 am »
Extending EVA O2 supply would just push the limitation elsewhere.  Make the suit last forever and you're still going to have around the same EVA time limits due to crew fatigue.  That's why O2, CO2, and other EVA consumables all last roughly the same time.

Offline Cinder

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #2 on: 10/07/2014 06:13 pm »
There's BotE skepticism on how good these are over at Ars.
http://arstechnica.com/civis/viewtopic.php?f=26&t=1256993

At the very least the ideation picture of a diver with nothing much more than a mask for continuous breathing, is deceptive.  The "room" the article uses as reference would be only the size of a small closet.
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Offline R7

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #3 on: 10/07/2014 06:47 pm »
But could it be similarly useful for extending astronaut EVAs?

No.

Read the original paper, look at figure 2. Desorption and resorption fluctuates the crystal mass between ~98.7% and ~95.6% of original over longer period of time. This translates to horrible ~3% propellant mass fraction for this kind of "crystal tank".

Might enable lighter, more compact portable oxygen concentrators for respiratory challenged earthlings.
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Offline MP99

Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #4 on: 10/07/2014 07:05 pm »
But could it be similarly useful for extending astronaut EVAs?

No.

Read the original paper, look at figure 2. Desorption and resorption fluctuates the crystal mass between ~98.7% and ~95.6% of original over longer period of time. This translates to horrible ~3% propellant mass fraction for this kind of "crystal tank".

Might enable lighter, more compact portable oxygen concentrators for respiratory challenged earthlings.
These aren't propellant tanks containing liquid oxygen. They are tanks pressurised to many atmospheres with compressed gas.

It's a reasonable question whether a tank which only needs to contain gas at low pressure might be lighter, not only because of smaller size, but also because of reduced skin thickness.

A reduced bulk to the backpack might also be a benefit in and of itself.

Cheers, Martin

Offline a_langwich

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #5 on: 10/07/2014 08:24 pm »
Sigh.  Bovine excrement popular science, hyping a modest theoretical endeavor.  "Could lead to" floating cities, flying cars, breathless excitement, and sex with supermodels every hour.  Or, as is actually the case, at BEST it could lead to more funding for the hype-rs for a small period of time, until everybody has moved on to the next great thing.

Hemosponge.  By July 1984, the concepts had been under development almost a decade, and prototypes had already been tested for several years:  http://www.nytimes.com/1984/07/10/science/inventor-s-goal-artificial-gills-for-people.html

That article talks about "making it smaller," but the size problem wasn't in how big it had to be to hold the oxygen, but how big it had to be to catch the miniscule amounts of molecular oxygen dissolved in seawater.  That's a fundamental limitation.  You can pump it through faster, but pumping requires energy, and your binding energy has to increase to rip the oxygen out of the water as it flies past.

The second problem mentioned was the binding/release energy.  This latest paper seems to ignore how much energy it takes to pull the oxygen back off the crystals (they mention using a vacuum, which would be frightfully expensive in energy terms).  It turns out that is a big problem, if you are not running it on a nuclear sub providing copious amounts of power.  It would use far too much power for a diver with a battery pack, and internal combustion engines would use up the oxygen they were supposed to be helping provide.  If you ARE running it on a nuclear sub, go ahead and run electrolysis on water and get your oxygen that way, rather than sucking all the dissolved oxygen out of miles of seawater and killing all lifeforms that depend on it.

It turns out hemoglobin is exquisitely tailored to balance tightly binding oxygen from the fluid in the lungs, while gently releasing it at the extremities due to slight variations in blood pH, presence of CO2, and other factors.
http://en.wikipedia.org/wiki/Oxygen%E2%80%93haemoglobin_dissociation_curve

And lastly, as mentioned above, the "large amounts of oxygen" being stored are in comparison to apparently very lightly compressed air.  More heavily compressed air, like you would find in a scuba tank, would actually be more dense than this.  Compressed pure oxygen would be more compact still, and LOX would be far, far more compact.

So, in summary, the authors found a chemical complex that bound to and released molecular oxygen.  All the rest was hype.

Offline R7

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #6 on: 10/07/2014 08:39 pm »
It's a reasonable question whether a tank which only needs to contain gas at low pressure might be lighter, not only because of smaller size, but also because of reduced skin thickness.

A reduced bulk to the backpack might also be a benefit in and of itself.

Alrighty then let us pick an example and do comparative math.

Random googling selected 3L 300bar steel scuba tank as contender. It weighs 4.4kg.

If filled to 300bar at 300K the tank contains 1.167kg of pure oxygen. Gas data from NIST oxygen properties book. Tank + oxygen weighs 5.567kg, useful mass fraction is 21%.

Crystal mass containing equivalent amount of oxygen weighs (98.7 / (98.7 - 95.6))*1.167kg = 37.16kg , 6.7 times more than full scuba tank.

The paper says that the crystal stuff "concentrates O2 by a factor
of 32 times the density of O2 gas at 1 atm". A bit ambiguous but 1.167kg of oxygen at 300K and 1 atm occupies 897L, divided by 32 gives 28L. Crystal density information varies 1.562kg/L - 1.421kg/L which give 24.8L - 26.2L size for the crystal storage. In any case substantially more than 3L + steel shell.

There, going from COTS scuba tanks to space-rated COPVs only improves the case for compressed storage.

Btw NASA daily oxygen per crew member standard is 0.84kg so the 3L tank is not miniscule.
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Offline MP99

Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #7 on: 10/07/2014 10:46 pm »
Thanks, both.

At least now we're talking about GOX vs LOX.

BTW, re energy to release the oxygen, the graph attached above shows temps of 110-120C. Is more required to initiate release?

Cheers, Martin

Offline R7

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #8 on: 10/08/2014 06:24 am »
BTW, re energy to release the oxygen, the graph attached above shows temps of 110-120C. Is more required to initiate release?

Thin black line is temperature, thicker reddish is weight% (the paper had no legends on that one but deducible from the text). Temperature fluctuates between ~29-140C. The release seems to start almost immediately when temperature starts to rise.

Another questions is how is release rate connected to the temperature. Is it proportional, does the release stop if you lower the temperature or is there some sort of runaway process which releases all oxygen once it's triggered to start? Even if it would be some nice proportional function of temperature there are practical challenges. What if you need a quick shut-off? With tank you close a valve, the crystal thing requires cooling down a lot of mass.

And would mechanical shocks, vibrations cause release? Answers might be in the paper but lost interest in deciphering the material science jargon once it was obvious regular tanks beat it hands down.
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Offline MP99

Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #9 on: 10/08/2014 07:28 am »
Sorry, I meant "up to 110-120C". Thanks for correction re 140C.

Understood re overall mass fraction.

Cheers, Martin

Offline cordwainer

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #10 on: 11/29/2014 09:38 am »
While the mass fraction is not very good and actually worse than a pressurized tank I could see this being useful for space travel in a few different ways.

1. Creation of a EVA hardsuit that is more comfortable and portable. A solid tank would be more conformable and large pressurized tanks can restrict movement. You don't really need a large oxygen supply for most EVA missions and a suit that conforms more to the body like a mechanical counter pressure suit would be easier to wear while in a space craft to make it easier for the astronauts to put the suit on and off in case of a decompression event or for easy egress from the spacecraft.

2. Boil-off is not just an issue with hydrogen and the possibility for a blow out to a pressurized tank that is constantly under pressure is higher than tanks that are regularly emptied and refilled. If we ever build an interstellar generation ship your going to either have two sets of oxygen tanks for atmosphere with each set acting as a bleed off for the other set(which adds unnecessary weight and complexity). Or you could build a solid oxygen tank using this technology that would be slightly lighter and much safer for long term storage of your air supply.

Offline cordwainer

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #11 on: 11/29/2014 09:53 am »
3. Could be useful for safer more maintenance free long term oxygen storage for any spacecraft. Specifically for storage of an emergency air supply in case of a decompression event. If your passengers find wearing parts of an MCP suit all the time uncomfortable(like while sleeping). You could have oxygen masks with feed lines to these solid oxygen tanks in specific areas aboard ship(note this could be useful for airlines planet-side).

4. Another possible plus to a solid oxygen tank would be that due to it being solid and more conformable it could offer better radiation protection to the crew when used in a shadow shield.

Offline cordwainer

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #12 on: 11/29/2014 10:02 am »
I imagine the tech level they would need for this to replace pressurized air supplies for the uses cited would not have to be anywhere near equivalent in storage capacity. It would only have to do slightly better than say current air rebreathing technologies that utilize potassium superoxide like the IDA71.

Offline cordwainer

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #13 on: 11/29/2014 10:20 am »
While(a-langwich, please use a username that is capitalized) makes a number of good points, they actually don't effect the use of such tanks in the aforementioned example. Heat could be provided for through an exothermic reaction(like in concrete or cement) and in space you have plenty of vacuum that could be used to draw a buffer gas along the surface area of the crystals. For small scale emergency air supplies or short EVA's this technology actually may be sound. While for an air supply to a Generation Ship or and Under Water habitat you would have plenty of heat and mass ratio fraction for this to work. I think this has promise when utilized on the small scale or very large scale.

Offline cordwainer

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #14 on: 11/29/2014 10:28 am »
Contrary to popular belief scuba divers very rarely carry oxygen tanks. The vast majority of divers breathe air or nitrox stored in a diving cylinder. A small minority breathe trimix, heliox or other exotic gases. Some of these may carry pure oxygen for accelerated decompression or as a component of a rebreather. Some shallow divers, particularly naval divers, use oxygen rebreathers or have done so historically.

Oxygen is rarely held at pressures higher than 200 bar / 3000 psi due to the risks of fire triggered by high temperatures caused by adiabatic heating when the gas changes pressure when moving from one vessel to another.
Average sea-level pressure is 101.325 kPa (1013.25 hPa or mbar) or 29.92 inches (inHg) or 760 millimetres of mercury (mmHg).

So it looks as if to me if most pressurized oxygen tanks aren't held at higher that three times the atmospheric pressure and if these oxygen crystals can hold as much oxygen as stated then they could be useful at least as a rebreather apparatus(a-langwich). The big issue is how much energy is need to release the oxygen in the crystals and how fast the oxygen gets released. The would have to release at partial pressure at least for it to be useful.

Offline mvpel

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #15 on: 11/29/2014 12:45 pm »
My dad, who had the respiratory challenge of COPD, used liquid oxygen. There was a dewar in the living room about four feet tall and two feet in diameter that the medical service company leased out, and refilled once a month or so. For excursions, the LOX packs were easily filled from the main container with the flip of a lever. It was a pretty sweet setup, and it was fun to do little science experiments with the LOX, though it was a bit tricky to get at it due to the safety mechanisms. My dad was a shop teacher in his day, though, so we managed it.

Here's the unit:
http://www.cairemedical.com/products/Helios_plus_marathon.aspx
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Offline kdhilliard

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #16 on: 02/21/2015 08:57 am »
Oxygen is rarely held at pressures higher than 200 bar / 3000 psi due to the risks of fire triggered by high temperatures caused by adiabatic heating when the gas changes pressure when moving from one vessel to another. Average sea-level pressure is 101.325 kPa (1013.25 hPa or mbar) or 29.92 inches (inHg) or 760 millimetres of mercury (mmHg).

So it looks as if to me if most pressurized oxygen tanks aren't held at higher that three times the atmospheric pressure ...

How do you come up with 3 atm?

1 bar is 0.987 atm so your 200 bar is ~ 200 atm.  Oxygen cylinders used in metal shops are more typically in the 2200 psi (~ 150 atm) range but NASA's new NORS (Nitrogen Oxygen Recharge System) uses 6000 psi (~ 400 atm) tanks.

Offline Moe Grills

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Re: Crystal Grains Store Large Amounts of Oxygen
« Reply #17 on: 02/21/2015 05:32 pm »
Extending EVA O2 supply would just push the limitation elsewhere.  Make the suit last forever and you're still going to have around the same EVA time limits due to crew fatigue.  That's why O2, CO2, and other EVA consumables all last roughly the same time.

Not to mention electric power supply, coolant, etc.

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