As an expert in the field of aerospace propulsion, I'd like to provide a detailed explanation of what powers rockets. Rockets are propelled by the principle of action and reaction, as described by Newton's third law of motion. The fundamental concept is that for a rocket to move forward, it must expel mass in the opposite direction at high speed. This expulsion of mass is achieved through the combustion of propellants, which are substances that can be burned to produce a high-velocity exhaust gas.

There are several types of rockets, each with its own method of propellant combustion and energy source:


1. Chemical Rockets: The most common type of rocket, chemical rockets are powered by the exothermic chemical reactions of their propellants. These reactions release a significant amount of energy, which is then converted into kinetic energy of the exhaust gases. The propellants can be in liquid or solid form.

- Liquid-Fuel Rockets: These rockets use liquid propellants that are stored in separate tanks and fed into a combustion chamber where they mix and burn. The combustion process generates high-pressure, high-temperature gases that are expelled through a nozzle to produce thrust.

- Solid-Fuel Rockets: These rockets use solid propellants that are typically cast as a single piece with a central hole (grain) that defines the burn rate and direction of the exhaust. Solid rockets are simpler to design and operate than liquid rockets, but they have less flexibility in terms of thrust control.


2. Electric Propulsion: This type of propulsion system uses electric power, often derived from solar panels or nuclear power sources, to ionize and accelerate a propellant, usually a noble gas like xenon. The ions are then expelled at very high velocities through an electric or magnetic field, generating thrust. Electric propulsion is highly efficient but produces relatively low thrust, making it suitable for long-duration missions in space where high delta-v (change in velocity) is required.


3. Nuclear Propulsion: Rockets can also be powered by nuclear energy. There are several methods of harnessing nuclear energy for propulsion:

- Nuclear Thermal Propulsion: This method uses a nuclear reactor to heat a working fluid, which is then expanded and expelled through a nozzle to generate thrust. The inert propellant is heated by the nuclear power source, making this a very high-performance propulsion system.

- Nuclear Electric Propulsion: Similar to electric propulsion, but the electric power is generated by a nuclear reactor. This allows for the use of electric propulsion systems with much higher power levels, resulting in higher thrust and efficiency.


4. Hybrid Rockets: These are a combination of solid and liquid propulsion. The fuel is in solid form, while the oxidizer is in liquid form. This allows for some of the simplicity and safety of solid rockets, combined with the performance and controllability of liquid rockets.


5. Plasma Propulsion: An emerging technology, plasma propulsion involves the acceleration of plasma to very high speeds to generate thrust. This can be achieved through various methods, including magnetohydrodynamic (MHD) propulsion, where a magnetic field is used to accelerate the plasma.

Each type of rocket propulsion system has its own advantages and disadvantages, and the choice of system depends on the specific requirements of the mission, such as the desired payload, mission duration, and available resources.

In conclusion, rockets are powered by a variety of energy sources and propellant combinations. The choice of propulsion system is crucial to the success of a space mission, as it directly impacts the spacecraft's performance, efficiency, and overall mission profile.

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Thermal rockets use an inert propellant, heated by a power source such as electric or nuclear power. Chemical rockets are powered by exothermic chemical reactions of the propellant: Solid-fuel rockets (or solid-propellant rockets or motors) are chemical rockets which use propellant in a solid state.read more >>