As we all know, NASA plans to extend human presence across the solar system, including the Moon and Mars. To do that, it needs to shorten the time it would take for us to get there and our support capabilities in a broad spectrum of associated activities.
NASA’s Solar Electric Propulsion (SEP) project is developing critical technologies that will enable us to extend the scope of new exploration and scientific missions while planning to support a wide variety of next-generation journeys to destinations in deep space.
Energized by the electric power from on-board solar arrays, the electrically propelled system will use 10 times less propellant than a comparable, conventional chemical propulsion system, (such as those used to fly the space shuttles into orbit), while retaining the capability to boost robotic and crewed missions well beyond low-Earth orbit; sending exploration spacecraft to distant destinations; and ferrying cargo to and from points of interest.
As you can imagine, this will also assist in laying the groundwork for future missions or resupplying those already underway.
NASA’s Glenn Research Center in Cleveland is the place leading the Solar Electric Propulsion project, and within the next decade, they hope to demonstrate a model ready for system-level flight.
Technologies currently under development include advanced solar arrays, high-voltage power management and distribution, power processing units, high-power Hall thrusters and spaceflight diagnostics for measuring system performance.
Under the guidance of NASA’s Game Changing Development Program, the SEP project has developed large, flexible, radiation-resistant solar arrays that can be stowed into small, lightweight, more cost-effective packages for launch. After launch, the arrays unfurl, capturing solar energy to provide the electrical power required to enable high-powered propulsion. (You will have seen similar principles employed in recent sci-fi films).
In the case of solar electric-propelled craft, large solar cell arrays convert sunlight to electrical power. The SEP project worked with ATK Space Systems Inc. and Deployable Space Systems Inc., both of Goleta, California, to build and test two solar array designs: one that folds out like a handheld fan (ATK MegaFlex) and another that rolls out like a window shade (DSS Mega-ROSA). Both use lightweight, durable structures and flexible blanket technology and can operate for long periods in Earth orbit or passing through the punishing Van Allen radiation belts.
With SEP technology, energy is fed into exceptionally fuel-efficient thrusters to provide gentle but nonstop thrust throughout the mission. The SEP project uses electrostatic Hall thrusters with advanced magnetic shielding, doing away with conventional chemical propellant delivered by a traditional rocket engine.
So how does it work?
The thruster generates and traps electrons in a magnetic field. Once trapped, they are used to ionize the onboard propellant – in this case, inert xenon gas – into an exhaust plume of plasma capable of accelerating the spacecraft forward. Several Hall thrusters can be combined to increase power. A system able to accelerate xenon ions to more than 65,000 mph will provide enough force over time to move cargo and perform orbital transfers.
In 2015, researchers successfully tested a12.5-kilowatt (kW) Hall thruster that employs magnetic shielding, enabling it to operate continuously for years on end. Such a capacity is vital to deep-space exploration missions. In 2016, NASA contracted for a flight-capable SEP system, including a power processing unit; a Hall thruster; and a xenon flow controller that can demonstrate the viability of said technology during spaceflight and ultimately be used on operational vehicles to achieve NASA’s mission in space.
The Solar Electric Propulsion project will demonstrate key technologies necessary for robotic and human exploration-class solar transportation systems as well as highly efficient orbit transfer capabilities. The first element of NASA’s Lunar Orbital Platform-Gateway will demonstrate the use of advanced, high-power SEP to maintain the gateway’s position and move it through orbits.
I don’t know about you, but after the Moon Missions ended over four decades ago, I felt the human race – who were making great strides into the great unknown – has been treading water . . . cosmologically speaking, ever since. It’s about time we witnessed something special, something that will help us take a step in the right direction toward future exploration and colonization.
- Source material: NASA – Space Technology Mission Directorate