Deep Space Exploration - No Longer a Distant Dream
A new revolution is on the horizon
Much in the same ways cars, trains and a plethora of aircraft have revolutionized their respective industries, advancements in electric propulsion technology could transform the space industry. So, what exactly is electric propulsion? A new method which utilizes electromagnetic fields to accelerate a propellant ( such as xenon gas ) and generate thrust that propels a spacecraft. At first glance, it is a rather simple concept and space agencies have pioneered electric propulsion technology as the future of space exploration.
Several space missions have already been completed using propulsion devices utilizing gridded ion thrusters and Hall thrusters. Both of these work based on a similar principle - solar power gets converted into thrust energy when the propellant, in most cases plasma, becomes ionized, which in turn causes acceleration through electromagnetic fields. There is, however, a persisting issue; the electrodes required for these devices reduce their lifetime due to the exposure and damage caused by the plasma, especially at a high - power level.
In order to get around this problem, scientists have resorted to using electrodeless plasma thrusters. For instance, one such technology harnesses radio frequency ( rf ) to generate plasma. An antenna will emit radio waves into a cylindrical chamber in order to create plasma, at which point a magnetic nozzle channels and accelerates the plasma to generate thrust. These type of thrusters are known as helicon thrusters and they are a significant improvement over the ion gridded and Hall thruster variants. Not only do they allow operational flexibility and a high thrust to power ratio, they are, at their core, simple.
Issues with the conversion efficiency
It is important to mention that Helicon thrusters have a different set of problems. The development of Helicon or MN rf plasma thrusters has been slowed down by the conversion efficiency of the rf power to thrust energy. The early stages of development yielded only single - digit conversion rates, which has in more recent studies, reached a conversion rate of 20%.
On the other hand, professor Kazunori Takahashi, from Tohoku University's department of elecrical engineering, achieved a breakthrough. In his latest experiment, Takahashi reached a 30% conversion efficiency. The propellant made all the difference. Most older electric propulsion devices use xenon gas, a propellant that is very expensive and hard to come by in sufficient quantities. Professor Takahashi used argon to achieve 30% conversion efficiency rate.
“Applying a cusp-type magnetic field inhibited the energy loss that generally occurs to the plasma source wall,” Takahashi said. “The breakthrough opens the door to advances in high-power space transportation technology.”