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Cars and aircraft have been powered by the same principles of combusting fossil fuels since their inception. Fueled by growing environmental concerns, the auto, aircraft, and shipping industries are looking for alternate solutions. Of course, this transition is beneficial for many other reasons, ranging from lower R&D costs, increased reliability, and reduced dependencies.
A similar shift might be ongoing in the space sector right now. Researchers across the world are investigating and developing alternate propulsion systems. The reasons are multiple; there is a desire to make space travel greener, faster, longer range, more affordable, and more regular. We recently covered a theory that could make Warp Drives a possibility, which of course, is a holy grail of space travel. But there are other technologies that are closer to becoming a reality.
On the most grounded side of the spectrum, we have the innovations used in the commercial space race. Jeff Bezos’ company Blue Origin power their craft using a mix of liquid hydrogen and oxygen, meaning that the craft at least technically doesn’t emit any carbon dioxide. While there are caveats to that statement, multiple companies and research teams are working to reduce the climate footprint of space travel, with propulsion being a particular concern.
One technology that seems promising is that of Plasma Thrusters. Being simple in construction and highly efficient, they’re deemed useful for changing smaller satellites' orbit. The European Space Agency and Spanish company SENER are working on the Helicon Plasma Thruster, which since its first test firing in 2015 has gone through an iterative process where ionization, acceleration efficiency, weight, and size have been improved. The hope is for this technology to become a cost-effective solution for large constellations of small satellites and other small spacecraft.
But there are also somewhat grander plans for Plasma Thrusters. Due to their effectiveness, some believe that they can make manned space travel faster than ever before. At Princeton Plasma Physics Laboratory, a physicist named Fatima Ebrahimi has designed a plasma thruster that could be of great importance as humanity ventures further into space. Currently, existing rocket engines have a low specific impulse or, in layman’s terms: low exhaust velocity, which limits craft acceleration.
Ebrahimi’s concept is built around tokamaks, torus-shaped fusion devices featuring a magnetic field able to contain hot ionized gas, ergo plasma. According to Ebrahimi, a tokamak such as the National Spherical Torus Experiment Upgrade (NSTX-U) will be able to create plasma bubbles that travel at incredible speeds in the region of 20km/s. With this knowledge, Ebrahimi created an engine design that, among others, can increase and decrease thrust by adjusting the strength of its magnetic fields. Another unique property of this new design is that it creates thrust not only by ejecting plasma gas but also plasmoids to create thrust. Plasmoids are a coherent structure containing both plasma and a magnetic field.
The long-distance engine
Readers of old-school sci-fi books will recognize the idea of nuclear propulsion. Along with the US Department of Energy, NASA is leading an effort to advance nuclear space technologies. They’ve recently selected three conceptual reactor designs, each receiving a contract worth $5 million.
Nuclear propulsion offers more useable energy in relation to fuel mass than chemical rockets. This makes such engines suitable for long-distance missions such as traveling to Mars or deep space exploration. Upon the completion of these contracts, design reviews will be conducted to provide NASA with recommendations for future research and development projects.
And this is just a narrow selection of the multitude of technologies being developed around the globe. We’ll continue to keep you posted on new developments in this field.