Hydra & Hythol Propellant Concepts

[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!