NASA this week took a giant step toward using solar electric power for future space missions by awarding a $67 million to Aerojet Rocketdyne to develop an advanced electric propulsion system.
Such a system would deploy large solar arrays that can be used to convert sunlight into electrical power that ionizes atoms of xenon which is the propellant for the spacecraft’s thrusters. The thrust of such a power plant isn’t huge but its ability to provide increasing, continuous power over a long period of time is what makes it so attractive for long-duration spaceflights.
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In addition, such a power plant could potentially increase spaceflight fuel efficiency by 10 times over current chemical propulsion technology and more than double thrust capability compared to current electric propulsion systems, NASA said.
Specifically Aerojet Rocketdyne will develop and deliver an integrated electric propulsion system – known as the Advanced Electric Propulsion System (AEPS) -- consisting of a thruster, power processing unit (PPU), low-pressure xenon flow controller, and electrical harness. NASA has developed and tested a prototype thruster and PPU that the company can use as a reference design, the space agency stated.
NASA has long experimented and used different forms of electronic electric propulsion technology. NASA said the first successful ion electric propulsion thruster was developed at Glenn Research Center in the 1950s. The first operational test of an electric propulsion system in space was Glenn’s Space Electric Rocket Test 1, which flew on July 20, 1964. Since then, NASA has increasingly relied on solar electric propulsion for long-duration, deep space robotic science and exploration missions the most recent being NASA’s Dawn mission which surveyed the giant asteroid Vesta and the protoplanet, Ceres, between 2011 and 2015.
NASA has also experimented with ion propulsion technology known as a Hall Thruster which trap electrons in a magnetic field and then use them to ionize propellant, which generate thrust, NASA said.
Interestingly a Hall Thruster was onboard the AirForce’s secretive X-37B spacecraft last year. The Air Force Research Laboratory said at the time: The Hall thruster that will fly on the X-37B experiment is a modified version of the units that have propelled Space and Missile Systems Center’s first three Advanced Extremely High Frequency military communications spacecraft. A Hall thruster is a type of electric propulsion device that produces thrust by ionizing and accelerating a noble gas, usually xenon. While producing comparatively low thrust relative to conventional rocket engines, Hall thrusters provide significantly greater specific impulse, or fuel economy. This results in increased payload carrying capacity and a greater number of on-orbit maneuvers for a spacecraft using Hall thrusters rather than traditional rocket engines. The experiment will include collection of telemetry from the Hall thruster operating in the space environment as well as measurement of the thrust imparted on the vehicle. The resulting data will be used to validate and improve Hall thruster and environmental modeling capabilities, which enhance the ability to extrapolate ground test results to actual on-orbit performance.
The AEPS is the next step in NASA’s overarching Solar Electric Propulsion project, which the space agency says is developing critical technologies to extend the range and capabilities of ambitious new science and exploration missions such as NASA’s proposed Asteroid Redirect Mission (ARM). ARM, if it gets funded, will rendezvous with the target asteroid, land a robotic spacecraft on the surface, grab a 4 meter or so sized boulder and begin a six-year journey to redirect the boulder into orbit around the moon for exploration by astronauts.
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