A rocket engine concept of me and Cosmo

Chara-cter

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#1
I and 8bitCosmonaut just came up with this concept
(Diagram edited from this one on Wikipedia)
1623767571269.png

Like the NERVA, the liquid hydrogen got heated, turn into gas and spits out the back, creating thrust. In our concept, the engine will add LOX to that hydrogen and burn it again, creating even more thrust. Cosmo is also working on a detailed version of this that also utilises a double chamber design for a presentation.
 

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#3
So a NERVA with liquid oxygen (since hydrogen will go back and reburn with LOX)
 
#4
I and 8bitCosmonaut just came up with this concept
(Diagram edited from this one on Wikipedia)
View attachment 66806
Like the NERVA, the liquid hydrogen got heated, turn into gas and spits out the back, creating thrust. In our concept, the engine will add LOX to that hydrogen and burn it again, creating even more thrust. Cosmo is also working on a detailed version of this that also utilises a double chamber design for a presentation.
The idea we had was actually a coincident, JLMC's idea was to combust the still-combustible hydrogen to get more thrust out of it, while my original idea was to attempt to mitigate the issue of leaking hydrogen propellant during deep space missions, by storing the hydrogen in the form of water, which spiraled down into reintroducing the oxygen into the hydrogen exhaust to combust and generate more thrust.

Since JLMC have given you guys a rough idea of such an engine's operation, I shall give you my take.


First I am going to assume that the spacecraft is using nuclear as a power source and has no issue with energy shortage.

Hydrogen that is stored as water will be electrolyzed into Oxygen and Hydrogen, cooled down into their liquid form and stored into their separate propellant tanks. The amount of water electrolyzed depends on the planned burn time.

The engine concept that I've proposed above has two modes; Normal and High-Thrust.

Normal mode (above image, left) has the external bell attached to the main exhaust nozzle, where the superheated hydrogen will flow through that and generate normal thrust. LOX will still run along the internal combustion chamber to prevent long term heat damage. The hot oxygen will be sent back to the heat exchanger to be cooled back down.

High-Thrust mode (bottom) has the external bell pushed down to attach to the nozzle of the inner combustion chamber via the use of actuators, the exhaust hydrogen is diverted into the inner combustion chamber and the LOX injection plug valve is opened. This combustion chamber does not require an ignition system, as the exhaust hydrogen's temperature far surpasses its flash point, simply introducing it to the oxygen will allow for immediate self-ignition.

1623808774947.png
 

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*blinks eyes*
 

Chara-cter

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#6
So a NERVA with liquid oxygen (since hydrogen will go back and reburn with LOX)
Exactly

The idea we had was actually a coincident, JLMC's idea was to combust the still-combustible hydrogen to get more thrust out of it, while my original idea was to attempt to mitigate the issue of leaking hydrogen propellant during deep space missions, by storing the hydrogen in the form of water, which spiraled down into reintroducing the oxygen into the hydrogen exhaust to combust and generate more thrust.

Since JLMC have given you guys a rough idea of such an engine's operation, I shall give you my take.


First I am going to assume that the spacecraft is using nuclear as a power source and has no issue with energy shortage.

Hydrogen that is stored as water will be electrolyzed into Oxygen and Hydrogen, cooled down into their liquid form and stored into their separate propellant tanks. The amount of water electrolyzed depends on the planned burn time.

The engine concept that I've proposed above has two modes; Normal and High-Thrust.

Normal mode (above image, left) has the external bell attached to the main exhaust nozzle, where the superheated hydrogen will flow through that and generate normal thrust. LOX will still run along the internal combustion chamber to prevent long term heat damage. The hot oxygen will be sent back to the heat exchanger to be cooled back down.

High-Thrust mode (bottom) has the external bell pushed down to attach to the nozzle of the inner combustion chamber via the use of actuators, the exhaust hydrogen is diverted into the inner combustion chamber and the LOX injection plug valve is opened. This combustion chamber does not require an ignition system, as the exhaust hydrogen's temperature far surpasses its flash point, simply introducing it to the oxygen will allow for immediate self-ignition.

View attachment 66867
Some problems (that I guess might not be that serious) would be with the diverters and the plug valves. Since hot hydrogen is blasting at those parts, I wonder if it would melt and damage them
Altaïr Horus Lupercal What do you think about this concept?
 

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#7
Exactly



Some problems (that I guess might not be that serious) would be with the diverters and the plug valves. Since hot hydrogen is blasting at those parts, I wonder if it would melt and damage them
Altaïr Horus Lupercal What do you think about this concept?
How bout coolin it with hydrogen or oxygen (not yet combusted)
 

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#8
Exactly



Some problems (that I guess might not be that serious) would be with the diverters and the plug valves. Since hot hydrogen is blasting at those parts, I wonder if it would melt and damage them
Altaïr Horus Lupercal What do you think about this concept?
In a sense this is a LOX/LH2 engine where LH2 is super heated before entering the combustion chamber. Heat management would probably be the biggest challenge indeed, it's generally what limits the conception of a rocket engine.

The nozzle would probably suffer even more, because LOX and LH2 have reacted together at that point, and the gases are even hotter.
At least, the thermolysis process could mitigate that problem: above 2000°C, the water molecules actually start splitting back into hydrogen and oxygen. I even found a diagram that shows by how much it happens depending on the temperature:
water-split-temperature-graph.jpg
I haven't found much informations about this, but apparently it also happens in a SSME: hydrogen and oxygen don't react completely in the combustion chamber (the temperature reaches 3300°C), and the reaction gradually finishes itself in the nozzle, as the gases cool down because of their expansion.

It means that at least the temperature in the combustion chamber wouldn't skyrocket to something like 5000°C, but still, cooling would be a major challenge there.

Also, the specific impulse of such an engine wouldn't be necessarily higher compared to the NERVA: in a LOX/LH2 reaction, the oxygen weighs 8 times more than hydrogen, assuming stoechiometric proportions (it would be rather 5 or 6 considering usual fuel/oxydizer ratios). The mixture would be more energetic, but also way heavier than pure hydrogen, so it's not necessarily a win on this side. But the idea of mixing chemical and thermal propulsion is interesting in itself.
 
#10
I haven't found much informations about this, but apparently it also happens in a SSME: hydrogen and oxygen don't react completely in the combustion chamber (the temperature reaches 3300°C), and the reaction gradually finishes itself in the nozzle, as the gases cool down because of their expansion.

It means that at least the temperature in the combustion chamber wouldn't skyrocket to something like 5000°C, but still, cooling would be a major challenge there.

Also, the specific impulse of such an engine wouldn't be necessarily higher compared to the NERVA: in a LOX/LH2 reaction, the oxygen weighs 8 times more than hydrogen, assuming stoechiometric proportions (it would be rather 5 or 6 considering usual fuel/oxydizer ratios). The mixture would be more energetic, but also way heavier than pure hydrogen, so it's not necessarily a win on this side. But the idea of mixing chemical and thermal propulsion is interesting in itself.
See JLMC? I knew it wouldnt be that easy.

I think its best we keep the water-form hydrogen storage idea and abandon the rest.