Note4Students

From UPSC perspective, the following things are important :

Prelims level: Bimodal Nuclear Propulsion

Mains level: Not Much

nuclear

NASA is planning to send mission to Mars in 45 days using the Bimodal Nuclear Propulsion.

Bimodal Nuclear Propulsion: What is it?

NASA relaunched its program to develop bimodal nuclear propulsion a few years ago. Bimodal nuclear propulsion is a two-part system that includes an NTP and NEP element.
This system is expected to enable transits to Mars in 100 days.
In 2023, the US space agency started a new program named NASA Innovative Advanced Concepts (NIAC) and has selected a nuclear concept for Phase I development.
This new bimodal nuclear propulsion system will use a “wave rotor topping cycle” that may reduce transit times to Mars to 45 days.

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 ionised hydrogen gas (plasma) that will then be channelled through nozzles to generate thrust.
NEP depends on a nuclear reactor to provide electricity to a Hall-Effect thruster (ion engine).
It will generate an electromagnetic field that will ionise and accelerate an inert gas (for example xenon) to create thrust.

Nuclear propulsions have major advantages over conventional chemical propulsion.
These benefits include fuel efficiency, a higher specific impulse rating and unlimited energy density (virtually).
NEP’s advantage over NTP and conventional chemical propulsion systems is that it offers more than 10,000 seconds of Specific impulse (ISP).
ISP is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust.

A crewed mission to Mars based on conventional propulsion technology may last up to three years.
However, A transit time of 45 days will reduce the overall mission time to months instead of years.
This will drastically reduce the major risks associated with missions to Mars which include – radiation exposure, the time spent in microgravity and related health concerns.

This means NEP systems can maintain thrust for close to three hours.
However, the thrust level is lower compared to conventional rockets and NTP systems.
In outer space, the thermal energy conversion rate is just 30-40% under ideal circumstances.