Hydra & Hythol Propellant Concepts

[Skye]

Hydra is a propellant concept I have come up with for a high-performance Methane-Based propellant. It has some downsides, like small handling issues, but far, far worse things have been handled & fired before.

Hydra is a mix of: 82% CH4 (methane), 10% C2H6 (ethane), 5% C3H8 (propane), 2% CH5N (Methylamine), & 1% C2H4 (Ethylene)

Oxidiser is just 100% O2, couldn’t find anything better, unsurprisingly.

Fuel + Oxidiser together are called Hydralox-M (the M is there to indicate Methane base, & to avoid confusion with Hydrolox when spoken)

Obviously, the methane is there for an overall good propellant base, the ethane & propane are there to boost density, the methylamine is there to give nitrogen in the exhaust (basically free energy without needing oxidiser), plus boost Hydrogen-richness, & the Ethylene is there to, because of its low ignition temperature (& instability, but in small amounts diluted it should be safe), it aids in ignition & combustion stability.

I’ve also done a study on the ideal engine for this propellant and have come up with this:

Full Flow Staged Combustion, O/F ratio of 3.35, combustion temp of ~3650 K, oxygen regen cooling chamber & nozzle, oxygen transpiration cooling throat. 350+ BAR chamber pressure depending on the engine.

Supposedly, this propellant combo could achieve (rounded to nearest percentage):

10% Increased density

10% increased density impulse

+4% Isp (ASL)

+3% Isp (Vac)

+8% Thrust

~40% less ignition delay

Better ignition, shutdown, & combustion stability

Fairly low storage hazard (more than methalox, but worth?)

92 Kelvin storage temperature (Vs ~95 for methane)

Is it worth it? Could it work? 

[Jim]

Hydra is a propellant concept I have come up with for a high-performance Methane-Based propellant. It has some downsides, like small handling issues, but far, far worse things have been handled & fired before.

Hydra is a mix of: 82% CH4 (methane), 10% C2H6 (ethane), 5% C3H8 (propane), 2% CH5N (Methylamine), & 1% C2H4 (Ethylene)

Oxidiser is just 100% O2, couldn’t find anything better, unsurprisingly.

Fuel + Oxidiser together are called Hydralox-M (the M is there to indicate Methane base, & to avoid confusion with Hydrolox when spoken)

Obviously, the methane is there for an overall good propellant base, the ethane & propane are there to boost density, the methylamine is there to give nitrogen in the exhaust (basically free energy without needing oxidiser), plus boost Hydrogen-richness, & the Ethylene is there to, because of its low ignition temperature (& instability, but in small amounts diluted it should be safe), it aids in ignition & combustion stability.

I’ve also done a study on the ideal engine for this propellant and have come up with this:

Full Flow Staged Combustion, O/F ratio of 3.35, combustion temp of ~3650 K, oxygen regen cooling chamber & nozzle, oxygen transpiration cooling throat. 350+ BAR chamber pressure depending on the engine.

Supposedly, this propellant combo could achieve (rounded to nearest percentage):

10% Increased density

10% increased density impulse

+4% Isp (ASL)

+3% Isp (Vac)

+8% Thrust

~40% less ignition delay

Better ignition, shutdown, & combustion stability

Fairly low storage hazard (more than methalox, but worth?)

92 Kelvin storage temperature (Vs ~95 for methane)

Is it worth it? Could it work? 

What would be the point?  It is cheaper than Methane?
Why bother?  Just use Natural Gas like ULA and Blue Origin

[Skye]

Higher Isp, higher density, N2 in the exhaust, not too expensive, even more stable combustion.

[Proponent]

I wonder whether all of those components, especially the ethylene, would play nice in a staged combustion cycle.

[Skye]

The methane & ethane shouldn’t be too bad, the propane may be a small issue, but hopefully the ethylene won’t be too bad, considering it’s only 1% of the fuel. Worst case, we can develop something to minimise coking (e.g: some sort of system where the engine is cleaned by propellant flow mid-flight)

[Ke8ort]

One issue I could see with your mixture is the formation of N2. At high temperatures, nitrogen is no longer "inert" and will start reacting with materials to form nitrides.  I don't know how much of an issue this will be, but it's something to consider.

[Skye]

Would it not just react with other nitrogen to form N2? How would I counter it?

[Ke8ort]

Would it not just react with other nitrogen to form N2? How would I counter it?

At high temperatures, the N2 atoms will dissociate into individual nitrogen atoms which want to react with other stuff. However, after doing some quick googling, it looks like the combustion temperature is right below the dissociation temperature of N2 (somewhere between 3000K and 4000K). At the very least, your preburners should be safe since they will have a lower combustion temperature than the MCC.

[Jim]

Higher Isp, higher density, N2 in the exhaust, not too expensive, even more stable combustion.

What is "not too expensive" based on?  Have you bought any or priced it out? 
What is more stable combustion based on?

[Jim]

again, how is this better than Natural Gas?

[Skye]

Higher Isp, higher density, N2 in the exhaust, not too expensive, even more stable combustion.

What is "not too expensive" based on?  Have you bought any or priced it out? 
What is more stable combustion based on?

According to a quick google search:

LCH4 is ~$40/kg
LC2H6 is ~$19/kg
LC3H8 is ~$15/kg
LC2H4 is ~$1/kg
LCH5N is ~$1/kg

(All prices rounded up)

More stable combustion is based on the C2H4, which should aid ignition shutdown, etc.

again, how is this better than Natural Gas?

Higher Isp (+2%), density (+12%), -40% ignition delay


A few small handling issues, but nothing too awful, people have handled much worse many times

[redneck]

Higher Isp, higher density, N2 in the exhaust, not too expensive, even more stable combustion.

What is "not too expensive" based on?  Have you bought any or priced it out? 
What is more stable combustion based on?

According to a quick google search:

LCH4 is ~$40/kg
LC2H6 is ~$19/kg
LC3H8 is ~$15/kg
LC2H4 is ~$1/kg
LCH5N is ~$1/kg

(All prices rounded up)

More stable combustion is based on the C2H4, which should aid ignition shutdown, etc.

again, how is this better than Natural Gas?

Higher Isp (+2%), density (+12%), -40% ignition delay


A few small handling issues, but nothing too awful, people have handled much worse many times

I think a bit of research will let you know that the quoted price on LCH4 is off by a couple of orders of magnitude. Off the top of my head, less than half the price of the other items on your list. $40.00 per kilogram should be more like $0.40 per kilogram.

[Skye]

Huh, interesting. (Damn you google, you dirty liar!)

Would it be that much more expensive, given that the ethane, propane, ethylene, & methylamine only make up 10, 5, 2, & 1% of the propellant respectively?

Edit: I also have a hydrogen-based propellant concept called Hythol - should I make a separate thread on it, or just add it into this thread and turn it into a general propellant concepts thread?

[Jim]

According to a quick google search:

LCH4 is ~$40/kg
LC2H6 is ~$19/kg
LC3H8 is ~$15/kg
LC2H4 is ~$1/kg
LCH5N is ~$1/kg

(All prices rounded up)

meaningless.  Says notthing on producing the mix to the ratios you specify.

More stable combustion is based on the C2H4, which should aid ignition shutdown, etc.

based on what data?  better than C2H4 alone or natural gas?

Higher Isp (+2%), density (+12%), -40% ignition delay

again, how this better than C2H4 alone or natural gas with cost in mind?

[Jim]

Huh, interesting. (Damn you google, you dirty liar!)

Would it be that much more expensive, given that the ethane, propane, ethylene, & methylamine only make up 10, 5, 2, & 1% of the propellant respectively?

what is the process to mix them all together?

[Jim]

Edit: I also have a hydrogen-based propellant concept called Hythol - should I make a separate thread on it, or just add it into this thread and turn it into a general propellant concepts thread?

how about just forget about it all together.

[redneck]

Edit: I also have a hydrogen-based propellant concept called Hythol - should I make a separate thread on it, or just add it into this thread and turn it into a general propellant concepts thread?

how about just forget about it all together.

How about working with one that is throwing out ideas and is willing to learn? Idea people burn through many ideas while searching for the useful ones. And even those that never quite make it are part of the culture of searching and learning.

[Skye]

again, how this better than C2H4 alone or natural gas with cost in mind?

Well, C2H4 in such large quantities would be extremely unstable & worse to handle than having it diluted, and considering how little of the cost propellant makes up, does it really matter if it’s, say, 50% more expensive than base methane?

what is the process to mix them all together?

Pre-mix them before cooling? They are apparently all soluble / miscible in / with CH4

How about working with one that is throwing out ideas and is willing to learn? Idea people burn through many ideas while searching for the useful ones. And even those that never quite make it are part of the culture of searching and learning.

Quite true, I have come up with many a stupid idea, but I’ve had a couple good ones, and hopefully this is one!

[redneck]

[quote

How about working with one that is throwing out ideas and is willing to learn? Idea people burn through many ideas while searching for the useful ones. And even those that never quite make it are part of the culture of searching and learning.


Quite true, I have come up with many a stupid idea, but I’ve had a couple good ones, and hopefully this is one!

I haven't noticed ITAR mentioned in this thread. Being from Britain, and working on an open forum, you will miss a fair bit of information that is technically illegal for many of us to post. International Traffic in Arms Regulations can be interpreted as exporting controlled technology when we get too specific in certain areas in this forum.   Thought you should be aware that the responses to your thoughts will be limited.

Added later.  You may have run across the Isp equation that the Isp is proportional to the square root of temperature over molecular weight by now.  Double Isp either requires quadruple the temperature or reducing molecular weight by a factor of four. With the CH4 vs C2H4 that you listed above. CH4 plus O2 goes to CO2(44) plus 2xH2O(18) for an average molecular weight of 26.67. C2H4 plus O2 goes to CO2(44) plus 1xH2O(18) for an average molecular weight of 31.  You would have to increase operating temperature by 16% just to maintain the same Isp.  Vastly simplified while drinking my morning coffee.

[Skye]

I see, thank you. It is unfortunately necessary that ITAR exists, due to things I won’t talk about on this forum, but the limitations are only for extremely technical things, right?

Anyways, about the Isp, just wanted to add the cycle is FFSC, 350 BAR chamber pressure, ~3650 K temp. Anything you could add to increase H richness? Ammonia? (We have methylamine which may act as a buffer against copper damage)

[Jim]

Anyways, about the Isp, just wanted to add the cycle is FFSC, 350 BAR chamber pressure, ~3650 K temp. Anything you could add to increase H richness? Ammonia? (We have methylamine which may act as a buffer against copper damage)

Cost, not ISP is what is needs to be optimized

[Skye]

I know, but I have a small obsession with increasing Isp, especially for minimal extra cost. Plus, if cost matters most, why develop FFSC over normal SC or ORSC. Hell, why go above GG, or even PF?

[Robotbeat]

Because it enables more benign turbine conditions for a given chamber pressure, enabling higher reuse levels and/or more reliability.

[Stan-1967]

This concept would limit the benefits of sub cooled methane.  The ethylene & methylamine would freeze out before the methane.  So maybe you gain a few ISP points,  but you get penalized on total prop load.

Also the focus on hydrogen is misguided.  Look at what the hydrogen is bonded with.  Big heavy atoms of nitrogen dont help ISP.  Look at the combustion enthalpy.

[Greg Hullender]

This concept would limit the benefits of sub cooled methane.  The ethylene & methylamine would freeze out before the methane.  So maybe you gain a few ISP points,  but you get penalized on total prop load.

Also the focus on hydrogen is misguided.  Look at what the hydrogen is bonded with.  Big heavy atoms of nitrogen dont help ISP.  Look at the combustion enthalpy.

This is why you want a monatomic-hydrogen-fueled rocket. According to this 1990s paper, you can get an ISP of 750 to 1500s! Of course there are a few technical details, but, hey, it worked great in Space Cadet and The Rolling Stones!

[Jim]

I know, but I have a small obsession with increasing Isp, especially for minimal extra cost. P

You haven't shown that it is minimal cost

why develop FFSC over normal SC or ORSC. Hell, why go above GG, or even PF?

Because they are used on a reusable vehicle

[Skye]

This concept would limit the benefits of sub cooled methane.  The ethylene & methylamine would freeze out before the methane.  So maybe you gain a few ISP points,  but you get penalized on total prop load.

Also the focus on hydrogen is misguided.  Look at what the hydrogen is bonded with.  Big heavy atoms of nitrogen dont help ISP.  Look at the combustion enthalpy.

Would the nitrogen not form N2 & give you a lot of energy?

Methylamine’s NH bonds take “between 4 & 50” KJ/ Mol to break, and forming N2 bonds gives you 945 KJ/ Mol. Does this not improve exhaust energy in the form of thermal / kinetic? Plus it doesn’t even take oxidiser, it’s just heated by the combustion temp & releases energy for it.

Plus, it makes the exhaust more H2O-rich, which raises Isp, since methylamine improves the H:C ratio.

I dunno, we just covered bond strength in chemistry class. Maybe I’m obsessive over new shiny things lol

And to everyone replying to the FFSC comment, idk why I said that, it was the only similar thing I could think of, though it wasn’t very similar

[Skye]

Not sure if it’s worth adding, but I may as well mention Hythol, my hydrogen-based propellant.

Mix of:

91% H2

4% CH4 (dissolved)

3% NH3 (dissolved)

1% CH5N (dissolved)

1% C2H4 (dissolved)

Only -0.5% Isp average, and +12% density!