Can Fusion Thrusters Revolutionize Space Travel?

[gleem]

TL;DR

A fusion reactor is used to produce plasmoids which can be expelled in a controlled manner at speeds greater than 20 km/sec.

Princeton University researchers have https://www.pppl.gov/news/2021/01/new-concept-rocket-thruster-exploits-mechanism-behind-solar-flares a new type of rocket thruster using a fusion reactor which is used to produce plasmoid bubbles. These bubbles are extracted from the reactor at speed of 20 to possibly 500 Km/sec based on simulations. They believe that if this device can be built it could reduce the time of flight to Mars (and beyond) by a factor of ten. On top of that, it can use any gas available and is throttlable.

A diagram of the engine is contained in this article.

 

[anorlunda]

Here's a link to the actual paper (paywalled).

https://www.cambridge.org/core/jour...oid-thruster/F296E45CC504E8FF2586EA79117E2514

Abstract
A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The generated low-temperature plasma is simulated in a global annular geometry using the extended magnetohydrodynamic model. Because the system-size plasmoid is an Alfvenic outflow from the reconnection site, its thrust is proportional to the square of the magnetic field strength and does not ideally depend on the mass of the ion species of the plasma. Exhaust velocities in the range of 20 to 500 km s−1500 km s−1, controllable by the coil currents, are observed in the simulations.

They believe that if this device can be built it could reduce the time of flight to Mars (and beyond) by a factor of ten.

They can't say that unless they can estimate the mass of the whole vessel, including the fusion reactor.

 

[hutchphd]

My guess is that it is a few decades away. And will remain so.

 

[mfb]

This looks like a variation of ion thrusters. It uses concepts of plasma handling that you also see in fusion reactors and in the Sun, but that doesn't mean it would fuse anything. It's probably not surprising that authors without any idea see "fusion" mentioned and jump on it...

We don't even have the power for ion thrusters for larger spacecraft , and this would need even more power per thrust.

 

[Al_]

Fission fragment rockets are much more realistic at the moment. And very cool.

 

[Astronuc]

Summary:: A fusion reactor is used to produce plasmoids which can be expelled in a controlled manner at speeds greater than 20 km/sec.

A diagram of the engine is contained in this article.

From the MSN article:

Fusion reactor experiments are popular on Earth as the“next generation” of nuclear energy technology, but none has created more power than it uses... yet. Spaceflight is a popular additional use case for plasma fusion ideas because fusion technology can, hypothetically, stay pretty lightweight while generating a ton of thrust. High-temperature elements in plasma form are confined and selectively released to propel a spacecraft .

Ugh!

A plasmoid is a form of plasma, not an 'additional' material.

Later in the artice -

And finally, Ebrahimi’s device design is flexible to work with any gaseous element, meaning both lighter, smaller atoms of gas and bigger, heavier ones. This gives spacefaring groups the option to choose different kinds of burns for longer or shorter flights, for example.

Um, fusion ain't going to happen.

From the schematic, it's not clear where fusion reaction would be taking place.

I'll have to download the paper to peruse the details. I'd be interested in the rate of recombination in the plasma. https://arxiv.org/abs/2011.04192

Meanwhile - While looking for some background material, I stumbled across this article "Problematic nature of plasmoid theory of magnetic reconnection". I haven't looked at the details yet.
https://arxiv.org/abs/1904.09836

The concept reminds of stuff we looked at ~35+ years ago.