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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. 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.

Must Read:

Cryogenic Engine: https://www.iasgyan.in/blogs/cryogenic-engine

Basics of Missiles: https://www.iasgyan.in/blogs/the-basics-of-missiles

Nuclear Fission and Fusion: https://www.iasgyan.in/daily-current-affairs/nuclear-fusion-and-fission

https://timesofindia.indiatimes.com/gadgets-news/explained-how-nuclear-powered-rockets-can-send-missions-to-mars-in-45-days/articleshow/97176430.cms

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