International Space Agencies – Missions and Discoveries

Bimodal Nuclear Propulsion can send missions to Mars in 45 days


From UPSC perspective, the following things are important :

Prelims level: Bimodal Nuclear Propulsion

Mains level: Not Much


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.

Benefits offered

  • 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.

Benefits for manned missions

  • 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.

Limitations of these nuclear propulsion systems

  • 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.


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