Nuclear Powered Rockets

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Context:

In 2023, the US space agency started a new program named NASA Innovative Advanced Concepts (NIAC) and has selected the development of a new concept of bimodal nuclear propulsion.
This new bimodal nuclear propulsion system will use a “wave rotor topping cycle” that may reduce transit times to Mars to 45 days. This proposal was put forward by Prof. Ryan Gosse.

How will nuclear propulsion work?

Nuclear propulsion is based on two concepts Nuclear-Thermal Propulsion (NTP) and Nuclear-Electric Propulsion (NEP).
The NTP system includes a nuclear reactor that will heat liquid hydrogen (LH2) propellant and turn it into ionized hydrogen gas (plasma) that will then be channeled through nozzles to generate thrust.

Nuclear Thermal Rocket

A nuclear thermal rocket(NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket.
In an NTR, a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor and then expands through a rocket nozzle to create thrust. The external nuclear heat source theoretically allows a higher effective exhaust velocity and is expected to double or triple payload capacity compared to chemical propellants that store energy internally.
NTRs have been proposed as a spacecraft propulsion technology, with the earliest ground tests occurring in 1955.
Nuclear-powered thermal rockets are more effective than chemical thermal rockets, primarily because they can use low-molecular-mass propellants such as hydrogen.

Nuclear Electric Rocket

A nuclear electric rocket(more properly nuclear electric propulsion) is a type of spacecraft propulsion system where thermal energy from a nuclear reactor is converted to electrical energy, which is used to drive an ion thruster or other electrical spacecraft propulsion
The nuclear electric rocket terminology is slightly inconsistent, as technically the "rocket" part of the propulsion system is non-nuclear and could also be driven by solar panels. This is in contrast with a nuclear thermal rocket, which directly uses reactor heat to add energy to a working fluid, which is then expelled out of a rocket nozzle.
The key elements to NEP are:

1. A compact reactor core.
2. An electric generator.
3. A compact waste heat rejection system such as heat pipes.
4. An electric power conditioning and distribution system.
5. Electrically powered spacecraft propulsion.

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