**3. Aero nuclear propulsion**

Aero nuclear propulsion refers to using nuclear reactors or radioisotope thermoelectric generators (RTGs) to power aircraft. While the use of nuclear power for

### *Nuclear Propulsion DOI: http://dx.doi.org/10.5772/intechopen.110616*

aircraft propulsion has been researched for many years, it has never been widely adopted due to technical, regulatory, and public acceptance challenges.

In aero-nuclear propulsion, a nuclear reactor would be used to generate electricity, which could be used to electric power motors that drive the aircraft's propellers or turbines. Alternatively, an RTG or NTP could be used to provide a direct heat source, which could produce high-speed exhaust to provide thrust.

The main advantage of aero-nuclear propulsion is that it offers a much higher energy density than conventional fuel sources, allowing for longer flight times and greater range. However, the use of nuclear power in aircraft also presents several challenges, including the need for a highly reliable and safe power source, effective shielding to protect against radiation exposure, and rigorous regulatory and licensing processes.

Despite these challenges, the concept of aero-nuclear propulsion continues to attract interest from researchers and military organizations, who see it as a potential solution to meet the growing demand for longer-range, higher-performance aircraft or missiles.

Aero nuclear propulsion can be combined with ramjet or scramjet technologies to increase thrust and specific impulse [2]. Ramjet and scramjet are two types of airbreathing propulsion systems that have the potential to revolutionize space and highspeed flight. Unlike traditional rocket propulsion systems that carry both fuel and oxidizer, ramjets and scramjets rely on the atmospheric air for oxygen, allowing them to be much lighter and more efficient [3].

### **3.1 Ramjet propulsion**

A ramjet is a type of air-breathing propulsion system that uses the vehicle's motion to compress incoming air, which is then mixed with fuel and burned to produce hot gases that are expelled through a nozzle to produce thrust. Ramjets are characterized by their simplicity and high performance at high speeds, making them well-suited for high-speed flight and space applications. The thrust of a ramjet is given by:

$$T = \dot{m}v\_{\varepsilon},\tag{1}$$

where *T* is the thrust, *m*\_ is the mass flow rate of the propellant, and *ve* is the exhaust velocity.

Ramjets are limited by their performance at low speeds, as they rely on the motion of the vehicle to compress the incoming air. To overcome this limitation, a ramjet can be combined with a conventional rocket propulsion system, allowing the vehicle to take off from a standstill and then transition to ramjet propulsion once it reaches high speeds [2].
