# NUCLEAR ROCKET:
Table of Contents:
- What Is Nuclear Rocket?
- Classification Of Nuclear Rocket
- Performance Of Nuclear Rocket
What Is Nuclear Rocket?
Nuclear rocket is conceptually similar to solar thermal rocket except for the source of heat. In nuclear rocket propulsion, the heat released from nuclear fission is used to burn the propellant. At the fundamental level, all nuclear fission reactors convert a nuclear mass m into energy E according to E = mc², where c is the speed of light. Fission is the process in which neutrons are absorbed by the fuel material. A fissile fuel, usually uranium or plutonium, converts a percentage of its mass into energy when its nuclei are split by neutrons. The excitement of the fuel atoms produces thermal energy which is then used to heat the propellant.
The heated propellant flows through the core of a nuclear reactor, and expands through a rocket nozzle to create thrust. To produce greater impulse and efficiency, higher temperatures in the reactor core are needed. In addition, a low propellant molecular mass will lead to a greater expansion of the propellant gas which in turn generates greater nozzle pressure. As such, hydrogen is mainly used as the propellant. Effectively, a nuclear thermal propulsion system can produce 107 times greater energy density than a chemical propulsion system.
Classification Of Nuclear Rocket:
- Solid Core
- Liquid Core
- Gas Core
1. Solid Core (Nuclear Rocket):
Solid Core Nuclear Rocket
2. Liquid Core (Nuclear Rocket):
A liquid-core engine which involves a rotating solid cylinder can be used to contain the fuel at a higher temperature. The induced centripetal force causes the fuel, which is of a higher molecular mass than the propellant, to the cylindrical wall. As the fuel melts and rises to temperatures above the melting point of the cylinder, the inner cylindrical wall naturally melts. The twist to this engine lies in the centripetal force which keeps the molten layer intact. Additionally, coolants running on the outside of the cylinder ensure that the entire cylinder does not melt through. The fuel is therefore able to be brought to a higher temperature than that in a solid core, and the propellant expelled with a greater force. Liquid-core engines can attain a much higher specific impulse of 1600 seconds.
These engines are currently considered to be very difficult to build. The reaction time of the nuclear fuel is much longer than the heating time of the working fluid and therefore requires a method to trap the fuel inside the engine while allowing the working fluid to easily exit through the nozzle. Most liquid-phase engines have focused on rotating the fuel/fluid mixture at very high speeds to press the fuel to the outside by centripetal force.
Liquid Core Nuclear Rocket
3. Gas Core (Nuclear Rocket):
The final classification is the gas-core engine. This is a modification to the liquid-core design which uses rapid circulation of the fluid to create a toroidal pocket of gaseous uranium fuel in the middle of the reactor, surrounded by hydrogen. In this case, the fuel does not touch the reactor wall at all, so temperatures could reach several tens of thousands of degrees, which would allow specific impulses of 3000 to 5000 seconds.