theoretical propulsion

[TimBueschen]

I have been working on an idea i had for a new type of rocket engine that works in the atmousphere that would most likely be a jetpack rocket engine. It takes in air and seperates it into individual atoms then rebonds them to form a combustible compound. You would take in the air change it into the new substence and compress it, than you would be able tom create thrust. I am not sure how everything will work but please comment back about this propulsion system.

[LucidDreamer]

A combustion reaction: (reactant containing carbon) + O2 --> CO2 + H2O (unbalanced)

I think your jetpack rocket engine would need a reactant besides what's already in the air. If you were to take CO2 or something from the air and turn it into a combustible compound then you would use more energy than you would get out of the combustible compound. Maybe you could make a suit of photocells to supply the energy needed to make the combustible compound. You could be a sort of flying combustible black plant.

[Rasori]

Nitpicking, but I was near-certain that the air had more than just O2 in it...

[insane_alien]

photocells probably would not not be able to provide enough power for it to lift itself but a nuclear reactor just might.

[Mokele]

Um, doesn't the 2nd law of thermo screw that up? You use energy to form complex molecules, storing a portion of that energy in their chemical bonds, then break for bonds and release the energy. In both steps, you lose energy to entropy, so it seems a bit pointless. Plus, you'd have to start out with a store of energy anyway, so why not just cut out the middle-steps and use whatever you have stored for propulsion directly? You'd get more efficiency that way.

 

Mokele

[[Tycho?]]

Um' date=' doesn't the 2nd law of thermo screw that up? You use energy to form complex molecules, storing a portion of that energy in their chemical bonds, then break for bonds and release the energy. In both steps, you lose energy to entropy, so it seems a bit pointless. Plus, you'd have to start out with a store of energy anyway, so why not just cut out the middle-steps and use whatever you have stored for propulsion directly? You'd get more efficiency that way.

 

Mokele[/quote']

 

I was thinking the same thing, but for a thruster it doesn't need to be creating power. Having a surplus of energy doesn't automatically give you thrust, you have to convert that into kinetic energy. If you could make your own combustibles from the atmosphere, you would be able to get that kinetic energy from combusing the fuel. It would also mean that you dont need fuel tanks, only an energy reserve. Although I doubt that such a devise would work anyway, it would be innefficient to the extreme, the amount of power needed to make your own fuel in flight must be huge.

[mezarashi]

'']It would also mean that you dont need fuel tanks, only an energy reserve. Although I doubt that such a devise would work anyway, it would be innefficient to the extreme, the amount of power needed to make your own fuel in flight must be huge.

 

But then again, that's what "fuel" means to us; it is an energy reserve. Before we were able to harvest nuclear energy, it was and generally currently still is by far the only reliable and "safe" method in storing a large amount of energy (through molecular bonds). Our current technology would make it ridiculous to continually create this fuel during flight for the equipment used to do so would be such an unnecessary but additional weight to propel. So far our battery technology is relatively limited in storing electrical energy. How much energy is in 1 kg of battery vs 1 kg of benzene? (even considering the thermal losses associated with converting it into some sort of mechanical kinetic energy). I guess in the end, we have these options and they are nothing new in the context of existing engineering technology:

 

1. Use the fuel or energy reserve to directly drive the propulsion system. For example a rocket in which the fuel is combusted in such a way that the molecules exit the rocket at high speeds creating thrust. (chemical energy->molecular kinetic energy->thrust)

 

2. Use the fuel to directly create mechanical energy, like we do in a car. The fuel will explode locally within the pistons to create torque, which can then be coupled to the moving wheels or the propellers of an airplane. (chemical energy->molecular kinetic energy->mechanical torque->some sort of propulsion system)

 

3. This is an extension of #2 in fact. Using the fuel to create mechanical energy (either directly through a combustion engine or through thermal energy in water like in a power plant and its turbine) which is THEN used to create electrical power, which can then drive an electrical-mechanical system that will drive the system. This is the flying nuclear-power plant option which would in fact be atomic energy rather than chemical. (chemical energy->molecular kinetic energy(thermal)->mechanical torque->electromagnetic->electro-mechanically couple back to a mechanical propulsion system)

 

Our energy needs seem so complicated and inefficient when you think about. Why can't the kind of energy we want just be lying around somwhere?