Gilmour is using Hydrogen Peroxide as their oxidiser

[drew]

So it was recently brought to my attention that Gilmour is using high concentration Hydrogen Peroxide as their oxidiser in their hybrid motors. I should say I assume that it's high concentration as to my knowledge as high test peroxide is a requirement for rocket propellant use cases.

Does anyone view this as an EXCEPTIONALLY BAD IDEA? I've always been cautiously optimistic that they'd do what they've set out to do and thought it would be good for both Australia in general and our hobby more specifically. Now I'm concerned that they're going to maim or kill someone at worst and I'm much less optimistic about their future to but it mildly.

TBH I think I've never picked up the Hydrogen Peroxide oxidiser bit in their PR spiels as I've just never considered it would be considered. You can see it mentioned here.

https://www.gspacetech.com/single-post/2018/01/PR/Gilmour-Space-achieves-45kN-of-thrust-in-first-test

I'm also struck by the hubris of this statement.

Gilmour Space is pioneering a new breed of cheaper, safer and greener hybrid-engine rockets

emphasis mine.

[SpaceManMat]

They are supposed to be a rocket company trying to put payloads into orbit. As orbital class propellants go it’s on the more tame side of things, compared to say lox. Yes it’s of concern but any rocket startup is pretty much guaranteed to have a motor failure during development, as long as they take proper precautions then it will be safe.

[drew]

They are supposed to be a rocket company trying to put payloads into orbit. As orbital class propellants go it’s on the more tame side of things, compared to say lox. Yes it’s of concern but any rocket startup is pretty much guaranteed to have a motor failure during development, as long as they take proper precautions then it will be safe.

Mmm, I'm not convinced. HTP is great for setting fires. Really great in fact. There are plenty of horror stories out there revolving around HTP.

I guess my shock comes from the fact that I always assumed they were using Nitrous for their hybrids. I'd never even considered they'd leverage HTP.

The whole quote about safer hybrids is quite misleading as well imo given their use of HTP.

[OverTheTop]

This book is great for hypergolics. Not sure if it covers HTP. If it does you should get a good feel for how bad it might be:
https://library.sciencemadness.org/libr ... nition.pdf

If it has nothing on HTP you will enjoy the read anyway

Whatever they are using needs to work within whatever constraints they are allowed to work within. It might come down to something like availability, cost or any number of other factors that will swing the equation in favour of HTP. It is not ringing alarm bells for me currently. MON or NTO I think would scare me more as oxidants, but I'm not a chemist . I wouldn't go anywhere near RFNA either

MON=Mixed Oxides of Nitrogen
NTO= Nitrogen Tetroxide
RFNA=Red Fuming Nitric Acid

[drew]

This book is great for hypergolics. Not sure if it covers HTP. If it does you should get a good feel for how bad it might be:
https://library.sciencemadness.org/libr ... nition.pdf

If it has nothing on HTP you will enjoy the read anyway

Whatever they are using needs to work within whatever constraints they are allowed to work within. It might come down to something like availability, cost or any number of other factors that will swing the equation in favour of HTP. It is not ringing alarm bells for me currently. MON or NTO I think would scare me more as oxidants, but I'm not a chemist . I wouldn't go anywhere near RFNA either

MON=Mixed Oxides of Nitrogen
NTO= Nitrogen Tetroxide
RFNA=Red Fuming Nitric Acid

Hi OTT,

Yep, I've read Ignition. That book is part of the basis for why I'm so sh*t scared of HTP.

From the chapter "Peroxide - Always a Bridesmaid"

Hydrogen peroxide decomposes according to the equation H2O2 —> H2O + 1/2 O2, with the evolution of heat. Of course, WFNA also decomposed, but not exothermically. The difference is crucial: It meant that peroxide decomposition is self-accelerating. Say that you have a tank of peroxide, with no efficient means of sucking heat out of it. Your peroxide starts to decompose for some reason or other. This decomposition produces heat, which warms up the rest of the peroxide, which naturally then starts to decompose faster — producing more heat. And so the faster it goes the faster it goes until the whole thing goes up in a magnificent whoosh or bang as the case may be, spreading superheated steam and hot oxygen all over the landscape. And a disconcerting number of things could start the decomposition in the first place: most of the transition metals (Fe, Cu, Ag, Co, etc.) and their compounds; many organic compounds (a splash of peroxide on a wool suit can turn the wearer into a flaming torch, suitable for decorating Nero's gardens); ordinary dirt, of ambiguous composition, and universal provenance; OH ions. Name a substance at random, and there's a 50-50 chance (or better) that it will catalyze peroxide decomposition.

[OverTheTop]

I am not a chemist, but since I do hang around quite a few of them (one of the perks of designing spectrometers ) I asked a few about their thoughts on the matter. Basically their opinion was that there was not a huge difference in them from their point of view. Each will have its own foibles and need to be dealt with appropriately, and the outcome will be similar.

There is the decomposition issue with H2O2 so storing for any amount of time will have it water down its value as a fuel, quite literally. That's one area where N2O is better from our POV.

[drew]

I am not a chemist, but since I do hang around quite a few of them (one of the perks of designing spectrometers ) I asked a few about their thoughts on the matter. Basically their opinion was that there was not a huge difference in them from their point of view. Each will have its own foibles and need to be dealt with appropriately, and the outcome will be similar.

There is the decomposition issue with H2O2 so storing for any amount of time will have it water down its value as a fuel, quite literally. That's one area where N2O is better from our POV.

So have those chemists read Ignition!?

Back to Ignition, the second to last paragraph in the book states the following.

Hydrogen peroxide will continue to be used, as a monopropellant, for attitude control and in other low-thrust applications. It will probably not be used as an oxidizer for main propulsion.

My question to you is what advancement in HTP usage or storage has caused the above conclusion to no longer be applicable?

[OverTheTop]

Hydrogen peroxide will continue to be used, as a monopropellant, for attitude control and in other low-thrust applications. It will probably not be used as an oxidizer for main propulsion.

That statement, to me, reads "low Isp". Given that assumption I suspect either cost or availability is the driving factor.

I have used relatively concentrated H2O2 (30%, aka 100 volume) and conc HCl to etch printed circuit boards (Cu) in the past. I have seen one tray of the stuff get away when I etched too many boards without letting the mixture cool. Etch time was about 10 seconds . Nothing much happened except the tray bubbling over in the fume hood. Made sure I didn't do that again though. Yes, it has its foibles.

[drew]

That statement, to me, reads "low Isp". Given that assumption I suspect either cost or availability is the driving factor.

According to the ESA...

The propulsive performance of hydrogen peroxide monopropellant rockets is about 20% lower than hydrazine, but the volume specific impulse achievable with 90% H2O2 is higher than most other propellants due to its high density. This is particularly useful for systems with significant aerodynamic drag losses and/or stringent volume constraints. With respect to bi-propellant and hybrid rocket engines, hydrogen peroxide yields a specific impulse comparable to other liquid oxidizers like dinitrogen tetroxide, nitric acid and even liquid oxygen (Wernimont and Muellens4, Wernimont and Garboden5)

https://www.esa.int/gsp/ACT/doc/PRO/ACT-RPR-PRO-JPC2006-HP%20Rockets%202006-5239.pdf

So technically you're correct in terms of a marginally lower Isp but that's is effectively negated by the high density of HTP when compared to other oxidisers.

[SpaceManMat]

Underlined key word below... it is the job to know how to how. Should be no supprises as the issues have been long known and documented.
I heard somewhere that one of the workers a Saturn 5 stage blew themselves up when they kicked a frozen lump of LOX on the test pad, not a recommended propellant handling method.
Hopefully the new guys are not be the kind that only learns things the hard way, such people do not make good propellant experts. Ignition was a great read wast it, I believe it is going to be republished.

They are supposed to be a rocket company trying to put payloads into orbit. As orbital class propellants go it’s on the more tame side of things, compared to say lox. Yes it’s of concern but any rocket startup is pretty much guaranteed to have a motor failure during development, as long as they take proper precautions then it will be safe.

Mmm, I'm not convinced. HTP is great for setting fires. Really great in fact. There are plenty of horror stories out there revolving around HTP.

I guess my shock comes from the fact that I always assumed they were using Nitrous for their hybrids. I'd never even considered they'd leverage HTP.

The whole quote about safer hybrids is quite misleading as well imo given their use of HTP.

[drew]

Underlined key word below... it is the job to know how to how. Should be no supprises as the issues have been long known and documented.
I heard somewhere that one of the workers a Saturn 5 stage blew themselves up when they kicked a frozen lump of LOX on the test pad, not a recommended propellant handling method.
Hopefully the new guys are not be the kind that only learns things the hard way, such people do not make good propellant experts. Ignition was a great read wast it, I believe it is going to be republished.

In theory I completely agree with you Matt. In practice Gilmour tounting their "safer" HTP hybrids makes me seriously question, well, everything. It's not like N2O is a walk in the park, as seen here.

http://www.knightsarrow.com/rockets/scaled-composites-accident/

Even with that comparatively speaking I think N2O is far superior to HTP from a safety perspective. And that's what concerns me. Scaled killed 3 people with a N2O hybrid test. These folk are playing with HTP instead. And that's a worry imho.

[OverTheTop]

I heard somewhere that one of the workers a Saturn 5 stage blew themselves up when they kicked a frozen lump of LOX on the test pad, not a recommended propellant handling method.

I recall that the person in question lost a leg. He kicked a stalacmite that had formed on the ground from a LOX leak somewhere above. He would have been thinking it was normal ice.

Great info on the H2O2 from ESA. Thanks Matt! So possibly volume is a driving factor, but I would not have thought major.

It did really surprise me how blasé the chemists were about the differences. If Gilmore handle this professionally and learn from mistakes that other people have made before, rather than making them themselves, the outcome should be acceptable.

[drew]

Great info on the H2O2 from ESA. Thanks Matt! So possibly volume is a driving factor, but I would not have thought major.

Indeed. It appears that HTP is on par with LOX in biprop and hybrid motors from an Isp perspective, at least according to this ESA study. And yet it's not being leveraged by anyone in that fashion other than Gilmour.

Either Gilmour knows something everyone else doesn't or everyone else knows something Gilmour should know. I think it's obvious where I believe the discrepancy lies.