Nuclear fusion rocket engine: the dream continues

space

Technology Innovation Website Editor – 12/07/2023

A nuclear fusion rocket engine uses rotating magnetic fields to propel plasma and produce thrust.
[Imagem: Pulsar Fusion]

Spindle direct drive

The dream of building a nuclear fusion rocket is still very much alive, and it could become a reality even before fusion is used to generate energy.

startup company Pulsar Fusionin the United Kingdom, which has been trying to make a nuclear fusion-powered rocket engine for more than a decade, has announced an agreement with researchers from Princeton University in the United States of America, to try to better understand the plasma involved in fusion.

There are many theoretical ways to achieve nuclear fusion, but they all depend on confining the fuel, which must remain in an extremely hot and pressured environment long enough for the reaction to occur. This confinement can usually be done manually, called magnetic confinement, or by pressure created by groups of laser beams, known as inertial confinement.

In the field of power generation, inertial confinement has advanced in recent years, especially with the ignition of nuclear fusion achieved last year at the Lawrence Livermore National Laboratory in the United States of America. But the vast majority of experiments to use nuclear fusion to generate electricity still use magnetic fields to confine plasma into structures called tokamax and stellarators.

Using nuclear fusion to propel a rocket is much simpler than a fusion station here on Earth because you don’t even need to magnetically entrap the plasma – you just need to control it enough to accelerate it and eject it into space. Here, too, there are several ways, but Pulsar Fusion works on a concept called Direct Fusion Drive, in which the propulsion for the missile comes directly from the nuclear fusion reaction, without having to go through an intermediate step of generating electricity.

It is much easier to make a nuclear fusion rocket engine than to build a nuclear fusion power plant.
[Imagem: Pulsar Fusion]

Plasma control

In the company’s design, the reactor generates power by creating a plasma of electrically charged particles. A rotating magnetic field then captures this plasma and ejects it into the rocket’s exit nozzle. According to the company’s calculations, with particles escaping at 800,000 km/h, it’s possible to go to Saturn in two years — the Cassini spacecraft took seven years to get there.

The problem is that design is easier than design, and controlling the heat of the plasma more than the heat of the sun is far from trivial. In fact, we still understand very little about the behavior of plasma, not only to manipulate it, but above all to manipulate it so as not to interrupt the process of nuclear fusion.

This is where the Princeton University team comes in, who have a project called “Inverted Princeton Field Formation,” which has already conducted a series of experiments in plasma physics to evaluate the configuration of a fusion power reactor.

The two teams will then collaborate to apply the latest machine learning techniques to analyze data from the Princeton reactor. The primary goal will be to try to understand the behavior of ultra-hot melted plasma in the rocket engine configuration, i.e. in the pulsed configuration.

Specifically, the simulations will evaluate the performance of the nuclear fusion plasma for propulsion as it exits a rocket engine emitting exhaust particles at hundreds of km/s, which will provide the parameters for tuning the axial magnetic fields generated by the coils.

Predictive simulation

Ultimately, the researchers hope to create predictive simulations of the behavior of ions and electrons in plasmas in the inverted field configuration. Accurate predictive simulations are needed for closed-loop systems, a key component of a future reactor that could be used to propel missiles.

“Humanity has a great need for faster thrusters in our growing space economy, and fusion provides 1,000 times the power of conventional ion thrusters currently used in orbit,” said Richard Dinan, founder of Pulsar Fusion. “In short, if humans can achieve fusion for energy, fusion propulsion in space is inevitable. We believe that fusion propulsion will appear in space for decades before we can harness fusion for energy on Earth.”