NASA has announced that it will launch Psyche in August 2022 to reach the asteroid belt between Mars and Jupiter. But there is something unique about this spacecraft—it will travel across space using a "solar electric propulsion" system.

Annibale de Gasparis, an Italian astronomer, found an asteroid called Psyche in 1852. The space rock was named after the Greek goddess of the soul. It is noteworthy because it has a significant amount of metal, in contrast to other asteroids with icy or stony compositions.

Asteroid Psyche orbits the Sun at a distance ranging from 235 million to 309 million miles from the brightest star of our solar system. One orbit takes five years to complete. Scientists have speculated that Psyche, the space rock, would be a remnant of an old planet whose crust and mantle mysteriously vanished over time.

Since scientists are unable to approach, view or measure Earth's core directly, the Psyche mission provides them with a once-in-a-lifetime opportunity to study and comprehend the origins of terrestrial planets like Earth.

The Psyche spacecraft, named after the asteroid, will travel to the asteroid for more than three years to conduct a thorough inspection. After arriving at the asteroid—most probably by 2026—the spacecraft will enter orbit around it and deploy a range of sensors to study the celestial body.

NASA said: “The spacecraft will rely on the large chemical rocket engines of the Falcon Heavy launch vehicle to blast off the launchpad and to escape Earth’s gravity. But the rest of the journey, once Psyche separates from the launch vehicle, will rely on solar electric propulsion.”

As explained by the space agency, large solar arrays turn sunlight into electricity and provide the power source for the spacecraft's thrusters in this type of propulsion [solar electric propulsion]. They're called Hall thrusters, and the Psyche spacecraft will be the first to utilise them beyond Moon's orbit, stated NASA.

Psyche spacecraft will carry xenon, the same neutral gas used in vehicle lamps and plasma TVs, as a propellant. Electromagnetic fields will be used by the spacecraft's four thrusters to accelerate and expel charged atoms, or ions, of that xenon. As the ions are ejected, propulsion is created, moving the spacecraft into space and generating blue ionised xenon beams.

The Hall thrusters on Psyche could run for years on end without running out of fuel. Psyche's tanks will hold 2,030 pounds (922 kilogrammes) of xenon; engineers believe that if the mission were to rely on standard chemical thrusters, it would burn through approximately five times that amount of fuel.

Arizona State University’s Lindy Elkins-Tanton, who as principal investigator leads the mission said: “Even in the beginning when we were first designing the mission in 2012, we were talking about solar electric propulsion as part of the plan. Without it, we wouldn’t have the Psyche mission. And it’s become part of the character of the mission. It takes a specialised team to calculate trajectories and orbits using solar electric propulsion.”

However, Carl Sagan, the legendary astronomer, once imagined a solar sailer, a starship that uses sunlight to propel itself through the solar system, similar to how a boat uses the wind. Decades later, now we are witnessing the development of such spacecraft.

For example, the idea triggered by Sagan became a reality through Japan’s IKAROS—took flight in July 2010—which was an experimental satellite designed by the Japanese Aerospace Exploration Agency to demonstrate the latest solar sail propulsion techniques and later, the LightSail project. The LightSail 2 spacecraft, which launched in June 2019, uses only sunlight to change its orbit and is currently on an extended mission to advance solar sailing technology.

Solar Electric Propulsion

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