NASA explores nuclear propulsion for travel to deep space

The nuclear thermal propulsion rocket engine uses what is known as centrifugal liquidfuel bubbling. This allows for faster travel through deep-space. The University of Alabama at Huntsville (UAH), is leading an American consortium to study the concept of thermal propellant under a NASA research contract. nuclear power (NTP).

NASA has made significant progress towards a solid fuel NTP design. This bubbling design is one of three hydrogen-based concepts for a next generation liquid-fueled NTP rocket.

While the hydrogen propellant gas is heated to extremely high temperatures by the bubbling centrifugal NTP, there is no combustion. The engine's rotating liquid uranium core heats hydrogen through a porous wall. This causes the gas to bubble up and cause it to expand quickly. The expanding hydrogen gives the spacecraft thrust as it leaves the nozzle.

The design has significant advantages over conventional liquid-fueled rocket engine engines that burn hydrogen or oxygen. Dr. Dale Thomas is the principal investigator of the project and an internationally recognized systems engineering scholar at UAH. He explains that conventional liquid-fuel engine combustion results in heavier propellant molecules (H2O for hydrogen and oxygen) and won't come out the nozzle as fast, which provides more push, but less impulse.

For example, thrust is the force that an engine produces to propel a spacecraft beyond Earth's gravity. Momentum refers to the amount of momentum that a fuel unit can provide. This is important when it comes time to get a ship to a specific destination in space. The bubbler engine is conceptually intriguing. However, technical challenges remain. One of these is the development of a porous wall material that can withstand direct contact of molten uranium.

Dr. Thomas says, "We are still in the beginning stages of this." He notes that bubbling is a concept that has existed since the 1960s. Although the physics of bubbling is well-understood, engineering problems have kept this idea from being implemented. We are currently evaluating current technology to determine if we can develop a prototype liquid-fueled NTP motor.

According to him, UAH's research focuses on three areas. The first is thermodynamic modeling and analysis heat transfer between liquid uranium, and gaseous hydrogen. We will analyze and model the trajectory and geometry of gaseous hydrogen bubbles within a liquid-uranium medium. Third, we will conduct experiments to verify the predictions made by the thermodynamic and dynamical models.