[🇮🇳] ISRO Successfully Starts Trials of Advanced Nuclear Thermal Propulsion System

Krishna with Flute · Feb 25, 2025

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ISRO Successfully Starts Trials of Advanced Nuclear Thermal Propulsion System

ISRO has indeed initiated trials for using nuclear power in satellite launches, marking a significant step forward in space exploration.

Nuclear-powered rockets are being developed to address several challenges in interplanetary missions, including the limitations posed by insufficient sunlight and oxygen. These challenges have hindered the efficiency and speed of space travel, particularly for missions to distant planets like Mars.

Solar-powered systems rely on sunlight for energy, which becomes less effective as spacecraft move further from the Sun. This was evident in the Chandrayaan-3 mission, where the lander's operations were limited due to lack of sunlight. Chemical rockets require oxygen as an oxidizer, which is not readily available in space or on many celestial bodies. Conventional chemical propulsion systems take six to nine months to reach Mars from Earth. This prolonged exposure increases risks such as cosmic radiation and microgravity effects on astronauts.

Nuclear thermal propulsion (NTP) can significantly reduce travel times by leveraging nuclear fission for energy production. For example, a trip to Mars could be completed in about 45 days instead of several months. NTP offers nearly five times the propellant efficiency of chemical rockets, allowing for more payload capacity and longer sustained thrust. Nuclear power can enable missions beyond our solar system due to its ability to provide consistent energy without relying on solar input.

The Demonstration Rocket for Agile Cislunar Operations (DRACO) project (NASA and DARPA Collaboration) aims to test a nuclear rocket engine in space by 2027 or earlier if possible.

Chandrayaan-3 Testing

ISRO successfully tested the first stage of an atomic-powered engine, specifically a radioisotope heating unit, on Chandrayaan-3. This unit is part of the propulsion module still orbiting the Moon.

The radioisotope heating unit (RHU) on Chandrayaan-3 works by harnessing the heat generated from the radioactive decay of isotopes, typically plutonium-238. The RHUs contain a small amount of plutonium-238, which decays radioactively over time. This decay process releases heat continuously. Each RHU generates about one watt of heat, which is sufficient to maintain operational temperatures for sensitive components and instruments on the spacecraft.

In Chandrayaan-3, two RHUs were installed in the propulsion module to keep it at operational temperatures during its mission. These units are crucial for maintaining functionality in extreme cold conditions where conventional heaters might fail.

The use of RHUs provides a reliable and long-lasting source of heat without relying on moving parts or external power sources. They help prolong mission life by ensuring that critical systems remain operational over extended periods.

However, a point to note is that RTGs are not used for propulsion but for generating electricity on interplanetary missions like Voyager and Cassini. RTGs harness heat from radioactive decay to produce electricity.

The successful testing of a radioisotope heating unit on Chandrayaan-3 is a crucial milestone in this endeavour.

Collaboration With BARC

ISRO is collaborating with the Bhabha Atomic Research Centre (BARC) to develop more advanced components like a 100-watt Radioisotope Thermoelectric Generator (RTG), which will be essential for powering future nuclear rockets.

The RTG provides a reliable and long-lasting source of power, essential for maintaining onboard systems such as communication equipment, navigation systems, and scientific instruments during extended missions. This power is generated by converting heat from radioactive decay into electricity using thermocouples.

RTGs are more fuel-efficient compared to traditional chemical batteries used in satellites. They offer a consistent power output over years without needing refuelling or maintenance.

As a leading institution for nuclear research and development in India, BARC provides critical expertise in handling radioactive materials and designing systems that convert radioactive decay into usable energy.

BARC has facilities like the Apsara-U reactor that enhance indigenous production of radioisotopes necessary for RTGs. These isotopes are vital for generating heat or electricity through radioactive decay.

Given its experience with nuclear safety protocols and waste management, BARC likely contributes to addressing safety concerns related to launch accidents and disposal of radioactive waste associated with these missions.

Nuclear Thermal Rockets

These rockets use fission reactors to generate high temperatures, which are then transferred to liquid propellants for propulsion. They offer greater efficiency compared to conventional chemical rockets.

ISRO plans to utilise nuclear propulsion for future interplanetary missions due to its potential for faster transit times and increased efficiency.

Addressing safety issues related to launch accidents and radioactive waste disposal remains critical for advancing this technology.

The start-up system of the nuclear rocket, control valve, control rod, cooling channel, thrust chamber, program controller and fuel pump were developed. The new rocket is expected to be launched soon. With that, India will make a huge leap in the field of space research.

Former ISRO Chairman S Somanath emphasised that India's nuclear sector will play a pivotal role in powering future space missions through collaborations with the Department of Atomic Energy. This initiative aligns with global trends where several countries are exploring nuclear power options for space exploration due to their compactness and long life attributes.

Benefits of Nuclear Power In Space Missions

Independence from Sunlight: Nuclear power systems can function independently of sunlight, making them ideal for deep space missions beyond the inner Solar System where solar energy is limited.

Compactness And Efficiency: Nuclear-based systems often have less mass than solar panels of equivalent power, allowing for more compact spacecraft designs that are easier to manoeuvre. They provide high efficiency in terms of fuel usage, especially with nuclear thermal propulsion (NTP), which can be three times more efficient than chemical rockets.

Reduced Transit Times: NTP engines reduce trip times by requiring less fuel to be lifted into space, which is crucial for human missions to Mars and beyond. For example, a trip to Mars could be shortened by about 25% compared to traditional chemical rockets.

Increased Payload Capacity: The efficiency of nuclear propulsion allows for larger payloads or additional supplies on board spacecraft, enhancing mission capabilities and scientific returns.

Long-Term Power Supply: Nuclear systems can provide sustained power over years without needing frequent refuelling or maintenance, making them suitable for long-duration missions or establishing sustainable bases on other planets.

Enhanced Instrumentation and Communication: They offer higher power levels for onboard instruments and communication systems, which is particularly beneficial as spacecraft travel farther from the Sun where solar energy becomes insufficient.

IDN