Use of Red Oxygen as an Oxidiser

[fredinno]

Would a oxidizer like red oxygen become a good oxidizer for use in the future? There was a old thread discussing the possibility of using Red Oxygen and Metallic Hydrogen as oxidizers, but it mainly focused on Metallic Hydrogen, a theoretical form of Hydrogen that may or may not exist. Therefore, I have created a new thread focusing on the more practical component, Red Oxygen.

Red oxygen is a stable form of Oxygen that is a dark-red solid allotrope of Oxygen, aka. O8. It is produced by compressing oxygen at room temperature to 98692.3 atm, or 10 GPa (Really hard to produce). Due to its incredible density, it has a higher ISP, and would mean (in theory) smaller, and more economical rockets (especially for ultra-heavy launchers). It also is metastable, meaning that rockets will not need excessive reinforcing.

For more information: http://en.wikipedia.org/wiki/Solid_oxygen#Red_oxygen

Edited May 24, 2015 by fredinno

[dansmithers]

It could be useful, assuming its meta-stability doesn't make it nonflammable.

And, of course, assuming that you could modify an engine to burn it.

[SciMan]

Not to mention that the tanks for containing it need to be able to withstand 10GPa continuously. That's a very, very heavy tank. Tanks to hold this stuff probably end up with an extremely low mass ratio. As in, tank weighs 10,000 kg and holds 1,000 kg of metastable-O8, total mass 11,000 kg.

That's a losing proposition for a rocket oxidizer tank.

[fredinno]

Not to mention that the tanks for containing it need to be able to withstand 10GPa continuously. That's a very, very heavy tank. Tanks to hold this stuff probably end up with an extremely low mass ratio. As in, tank weighs 10,000 kg and holds 1,000 kg of metastable-O8, total mass 11,000 kg.

That's a losing proposition for a rocket oxidizer tank.

Wouldn't metastability make a tank containing red oxygen stay red oxygen without the continuous addition of pressure?

[sgt_flyer]

the tanks will not need to sustain these kind of pressures - that's why they are researches on metastability

(Think of red oxygen of something like diamonds are to carbon)

Now, i've not found how broad this is metastable (ex, if it requires only 1 gpa to maintain metastability, it's still too much )

Now, the main problem would still be the pricing of such fuels - producing those metastable fuels would require very expensive facilities and energy expenditures (create such pressure would require gigantic amounts of energy) - so you'll have an extremely expensive fuel. So, you'll soon run into the problem of needing to balance this extra pricy fuel vs the costs of a larger, but cheaply fueled, rocket

[DeepOdyssey]

Metallic Hydrogen

What? Hydrogen as oxidizing agent? Hydrogen is a good reducing agent.

[Iskierka]

The way metallic hydrogen was meant to be used as a propellant is that in the process of decomposing from an atomic metal, it would release huge energy quantities, allowing very high exhaust velocities from a monopropellant. I presume the suggestion is similar for red oxygen. However, red oxygen likely isn't being discussed for two reasons: A, it very likely has a lower energy release, and B, hydrogen is a sixteenth of the molecular mass once decomposed, meaning that to compete in velocity oxygen would have to be released with four times as much energy, greatly exacerbating the problem in A.

If red oxygen turned out to be metastable and metallic hydrogen didn't, then it may be somewhat interesting, though likely doesn't have near the same exceptional Isp offerings - in fact it likely wouldn't significantly outperform LH2-LOx, if at all. Red oxygen is only particularly something you might consider as it has lower formation pressure - though I suspect if you could reach the formation pressure of RO, MH would not be too infeasible.

EDIT - reading more, apparently O8 isn't meant to be used similar to metallic hydrogen, and is an actual oxidizer. The problem I imagine forming here is that it may be metastable in the same way ozone is, which we have tested as an oxidizer as it gives an extra oxygen with nearly no energy required to remove it. Trouble is, those tests generally turned into magic tricks, as ozone was rather fond of making the test stand vanish in a poof of smoke every time it encountered the slightest contaminant in fuel lines. It was in fact so volatile and eager to perform its trick that if you dilute it down with oxygen to the extent that it stops this act, you've lost basically all performance gains offered by the O2/O3 mixture.

Edited May 24, 2015 by Iskierka

[fredinno]

What? Hydrogen as oxidizing agent? Hydrogen is a good reducing agent.

I meant Metallic Hydrogen as the rocket fuel.

[K^2]

What makes you think that red oxygen is metastable? Seems to me, if it was metastable under standard conditions, we'd be using it for something. It's not impossible to produce, even if production in large quantities is prohibitively expensive right now.

[fredinno]

What makes you think that red oxygen is metastable? Seems to me, if it was metastable under standard conditions, we'd be using it for something. It's not impossible to produce, even if production in large quantities is prohibitively expensive right now.

I don’t think it is, it is considered metastable over a large pressure domain. I'm not sure at what pressure it is (it would be great if it was at 1 atm, but I haven't been able to find a report that specifies it).

[K^2]

That's problematic. I could see binding oxygen into a matrix that would keep it at higher pressure, potentially sufficient to maintain metastability, but I'm having trouble picturing this even as an SRB. If you make matrix out of your fuel, under these conditions, it's going to instantly react. If you use a buffer, it's hard to make it not to eat up too much of your I_SP.

[Red Iron Crown]

Due to its incredible density, it has a higher ISP

That's the opposite of how it works. All other things being equal, heavier molecules produce lower Isp than lighter ones. That's why H2 is such a popular propellant, even for NTRs where it doesn't need to combust.

[cryogen]

There's a bit of confusion. Density and I_sp are unrelated. Specific impulse only measures how much impulse a unit of mass will impart -- it doesn't care about volume.

Density is important too (of course): denser fuel means smaller rockets, less drag and probably lower tank mass. The source article, in Nature, suggests O₄ could be an interesting rocket oxidizer because it's denser than liquid O₂ -- not necessarily more energetic:

The interest in new oxygen allotropes is not purely theoretical. Liquefied ordinary oxygen (O₂) is used as a rocket fuel (called LOX), as it reacts energetically with fuels such as hydrogen and hydrocarbons. As the O₄ allotrope packs a lot of oxygen into a small space, it might be even more energy-dense.

http://www.nature.com/news/2001/011116/full/news011122-3.html

Is it more energetic than O₂ (which would give it higher Isp)? Well, maybe I guess? It's a different molecular form, so it could have a higher enthalpy of formation.

I can't find an answer by Googling: I'm not sure if this has been measured. (edit: but see below...) We do know ozone (O₃) has +143 kJ/mol enthalpy relative to O₂, which gives it a theoretical 20-30s of I_sp advantage, so I think it's plausible O₄ could have an advantage too. (In John D. Clark's Ignition, he says ozone is unlikely to ever be used in an actual rocket engine (pp. 112-114), because it's too unstable to spontaneous decomposition. (That's an amazingly fun book by the way -- you can find PDFs online, because it's out of print)).

https://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation_(data_table)

https://books.google.com/books?id=BfR0LexeuREC&pg=PA437

As for the molecular mass difference (O₄ weighs twice as much), that shouldn't matter. It would be completely combusted, so it's the molecular mass of the products like H₂O that are relevant for I_sp, not the oxidizer mass.

update: I found a theoretical paper that estimates O₄'s enthalpy of formation, using computational quantum chemistry. They think it's 93 - 95 kcal/mol (389 - 397 kJ/mol), which is almost three times that of ozone (!). So if it were stable (more so than ozone, which I'm very skeptical of), it could have a really huge I_sp advantage.

Ab initio calculations with highly correlated methods together with extensive basis sets have been used to obtain the most accurate heat of formation and stability with respect to dissociation (into molecular oxygen) for the chemically bound tetraoxygen molecule... Our best estimates places that value in the range 93-95 kcal/mol...

http://www.ncbi.nlm.nih.gov/pubmed/15268030

Edited May 25, 2015 by cryogen

[fredinno]

There's a bit of confusion. Density and I_sp are unrelated. Specific impulse only measures how much impulse a unit of mass will impart -- it doesn't care about volume.

Density is important too (of course): denser fuel means smaller rockets, less drag and probably lower tank mass. The source article, in Nature, suggests O₄ could be an interesting rocket oxidizer because it's denser than liquid O₂ -- not necessarily more energetic:

http://www.nature.com/news/2001/011116/full/news011122-3.html

Is it more energetic than O₂ (which would give it higher Isp)? Well, maybe I guess? It's a different molecular form, so it could have a higher enthalpy of formation.

I can't find an answer by Googling: I'm not sure if this has been measured. (edit: but see below...) We do know ozone (O₃) has +143 kJ/mol enthalpy relative to O₂, which gives it a theoretical 20-30s of I_sp advantage, so I think it's plausible O₄ could have an advantage too. (In John D. Clark's Ignition, he says ozone is unlikely to ever be used in an actual rocket engine (pp. 112-114), because it's too unstable to spontaneous decomposition. (That's an amazingly fun book by the way -- you can find PDFs online, because it's out of print)).

https://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation_(data_table)

https://books.google.com/books?id=BfR0LexeuREC&pg=PA437

As for the molecular mass difference (O₄ weighs twice as much), that shouldn't matter. It would be completely combusted, so it's the molecular mass of the products like H₂O that are relevant for I_sp, not the oxidizer mass.

update: I found a theoretical paper that estimates O₄'s enthalpy of formation, using computational quantum chemistry. They think it's 93 - 95 kcal/mol (389 - 397 kJ/mol), which is almost three times that of ozone (!). So if it were stable (more so than ozone, which I'm very skeptical of), it could have a really huge I_sp advantage.

http://www.ncbi.nlm.nih.gov/pubmed/15268030

From my research, O4 itself is purely theoretical- however, Red Oxygen was thought to be O4 not O8 until very recently- They could just be referring to Red Oxygen.

[cryogen]

From my research, O4 itself is purely theoretical- however, Red Oxygen was thought to be O4 not O8 until very recently- They could just be referring to Red Oxygen.

Well they have direct evidence now,

Experimental Detection of Tetraoxygen

Although suggested by Lewis in 1924 and theoretically predicted, O4 has so far proved extremely elusive, defying all attempts at the positive experimental detection of a bound, intact O4 species. The search has now been brought to an end by the conclusive proof, achieved by neutralization–re-ionization mass spectrometry (see picture), of the existence of intact O4 as a gas-phase species with a lifetime in excess of 1 μs, whose dissociation requires overcoming a barrier of the order of 10 kcal mol−1.

http://onlinelibrary.wiley.com/doi/10.1002/1521-3773(20011105)40:21%3C4062::AID-ANIE4062%3E3.0.CO;2-X/abstract