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[–] itsmemom97 0 points 1 points (+1|-0) ago 

If you want an answer in terms of 'does the reaction between sodium and water generate as much energy as the combustion of rocket fuel', then I cannot answer your question. My thermodynamics are too rusty to get even a ballpark figure.

In terms of reaction mechanics, however, I can offer an explanation.

Short answer: no.

Long answer:

Let's first examine the mechanics in the combustion of rocket fuel, and its use as a propellant for a rocket. Inside the rocket, the fuel is ignited, which causes a vigorous chemical reaction that generates a massive heat and gaseous reaction products per kilogram rocket fuel. It's actually the backward expelling of these reaction products at the exhaust of the rocket that propells the rocket forward. Or, as Isaac Newton posed in his third law, each reaction (the expelling of exhaust gases) has a corresponding counter reaction (the rocket is propelled forward).

The reaction between sodium and water is quite different. Sodium and water react to hydrogen gas and sodium hydroxide. The hydrogen gas evaporates, and the sodium hydroxide dissolves in the rest of the water, resulting in a solution of caustic soda. So, this reaction only produces a little amount of gaseous reaction products that could act as a propelling agent. Too little to propel a rocket. You could argue that the hydrogen gas could be ignited to act as a propellant, but that doesn't generate enough energy.

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[–] schneiderwm [S] 0 points 1 points (+1|-0) ago 

So when pure sodium is dropped into water the explosion that occurs is just caustic soda being made?

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[–] itsmemom97 0 points 1 points (+1|-0) ago 

yeah, well, and hydrogen gas. In chemical terms:

2Na + 2H2O --> 2NaOH(aq) + H2

which means: 2 sodium atoms both steal the OH part from H2O to form 2 sodium hydroxide (NaOH) molecules - that readily dissolve in the rest of the water. The 2 resulting H's combine to form H2, hydrogen gas.

The bang you hear is the hydrogen gas being ignited by the heat of the reaction of the sodium with the water. Interestingly, in this ignition (burning) of the hydrogen, 2 hydrogen molecules combine with one oxygen molecule from the air to form 2 water molecules, or in code:

2 H2 + O2 --> 2 H2O

and we're back to water. So eventually, it all ends up as caustic soda in water. Don't try this at home.

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[–] Nwabudike_Morgan 0 points 0 points (+0|-0) ago  (edited ago)

I think the sub is a little small for you to find an actual rocket scientist to answer you, but wiki notes that:

"The primary remaining difficulty with hybrids is with mixing the propellants during the combustion process. In solid propellants, the oxidizer and fuel are mixed in a factory in carefully controlled conditions. Liquid propellants are generally mixed by the injector at the top of the combustion chamber, which directs many small swift-moving streams of fuel and oxidizer into one another. Liquid-fueled rocket injector design has been studied at great length and still resists reliable performance prediction. In a hybrid motor, the mixing happens at the melting or evaporating surface of the fuel. The mixing is not a well-controlled process and generally quite a lot of propellant is left unburned,[3] which limits the efficiency of the motor. The combustion rate of the fuel is largely determined by the oxidizer flux and exposed fuel surface area. This combustion rate is not usually sufficient for high power operations such as boost stages unless the surface area or oxidizer flux is high. Too high of oxidizer flux can lead to flooding and loss of flame holding that locally extinguishes the combustion. Surface area can be increased, typically by longer grains or multiple ports, but this can increase combustion chamber size, reduce grain strength and/or reduce volumetric loading. Additionally, as the burn continues, the hole down the center of the grain (the 'port') widens and the mixture ratio tends to become more oxidizer rich.

There has been much less development of hybrid motors than solid and liquid motors. For military use, ease of handling and maintenance have driven the use of solid rockets. For orbital work, liquid fuels are more efficient than hybrids and most development has concentrated there."

TL;DR, you could probably do it, but it wouldn't be simple and there are much better/easier options available. Also sodium isn't all that expensive apparently they do some fancy electrolysis with table salt.