Rocket Science — Basics — Part 6 — Nuclear Engines 🚀🧑🚀
In this blog, we will explore nuclear-powered engines. Over the last 3 to 5 years, there has been a growing conversation about the necessity for humans to establish a presence on Mars and create a sustainable living environment there. Significant research has been conducted in the rocket and space sectors to ensure safe travel to Mars. To transport humans efficiently between Earth and Mars, we need advanced rocket engines capable of making this journey feasible. Scientists are proposing an attractive solution to this challenge: Nuclear Thermal Rockets (NTRs).
These type of rockets have very high Specific Impulse (measure of how good the engine is based on fuel efficiency) since they generate enormous amount of heat. It can even have double the time of Specific Impulse when compared to solid and liquid engines. We also need to choose materials that can tolerate such high temperatures. The main advantage is, the need for lift-off mass is halved and payloads can be increased in the rocket.
As we can see from the above diagram, the liquid hydrogen is pumped into the nuclear reactor chamber where it is heated to a very high temperatures. The nuclear reactor functions similar to the ones used in electricity generation and in submarines. The temperature is generated by nuclear fission reaction.
How fission reaction works?🤔
When a neutron hits a larger atom, it makes the atom to go to excited state and split into two smaller atoms thereby causing a chain reaction. Fission reaction does not happen automatically in nature. This type of chain reaction can be controlled. That is why, we were able to use it in power generation plants. The combined mass of fragmented nuclei’s will be lower than that of original nucleus because that mass will be converted as nuclear energy.
From the above diagram, we can see that Uranium 235 is bombarded with a neutron, it splits into Barium and Krypton and release a large amount of energy and the resulting three neutrons hit another three atoms and same actions continues causing a chain reaction.
Uranium 235 is used as a radioactive material. Liquid hydrogen is used because of its low molecular weight and high efficiency, is passed through the reactor, where it absorbs heat. The liquid with this high temperature moves towards the nozzle and expands thereby causing reduction in pressure and creating an increase in velocity. The nozzle actually converts the thermal energy into kinetic energy (Energy possessed by the object due to its motion).
The advantages of these nuclear powered thermal engines is that it can significantly reduce travel times to Mars, potentially by up to 25% and can minimize crew exposure to cosmic radiation. These engines could revolutionize space travel by significantly reducing travel time to distant destinations, making human exploration of the solar system more feasible and who knows mankind can go on expedition to celestial objects and other planets just like vacation.
These systems are not designed for launch from Earth due to their lower thrust capabilities. Instead, they will be launched into space using chemical rockets and activated once in orbit. The main disadvantages of these engines are radiation from the reactor to other spacecraft or to the crew members and propellant (liquid hydrogen storing at very low temperature) storage.
In the next blog, we shall explore lasers for getting into space.
Thanks for reading!!!
