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An artist’s concept of an electric-propelled spacecraft. | Credit: NASA
Electrically propelled spacecraft could soon be better protected against their own exhaust, thanks to new supercomputer simulations.
Electric propulsion is a more efficient alternative to traditional chemical rockets, and is increasingly being used space Missions, starting with prototypes on NASA’s Deep Space 1 and European Space AgencySMART-1 in 1998 and 2003, respectively, and thereafter Find a use In pioneering scientific missions such as NASA dawn and self Missions to Asteroid belt. There is even Plan to use electric propulsion On NASA Lunar portal Space station.
The idea behind electric propulsion is that the electric current ionizes (i.e. removes an electron from) Atoms Of neutral gas, such as xenon or krypton, stored on board the spacecraft. The ionization process produces a cloud of ions and Electrons. Then a principle called the Hall effect generates an electric field that accelerates the ions and electrons and directs them into a distinctive blue plume exiting the spacecraft at more than 37,000 miles per hour (60,000 kilometers per hour). Hence the electric propulsion system is also referred to as ion drive.
according to Sir Isaac Newton‘s Third law of motionEvery action has an equal and opposite reaction. The column of ions emitted by the spacecraft thus provides thrust. However, it takes some time to build up momentum, because despite moving at high speed, the ion column is very sparse. The motivation generated is not as strong immediately as Chemical missileBut ion engines require less fuel and therefore less mass, which reduces launch costs, and ion engines do not burn through all their fuel as quickly as chemical rockets.
Related to: How an ion engine helped NASA’s Dawn probe visit the dwarf planet Ceres
An advanced electric propulsion system undergoing testing at NASA’s Glenn Research Center. | Image credit: NASA/Jeff Janis
Power for electromagnetic fields is often provided by solar arrays, and thus this technology is sometimes referred to as solar electric propulsion. But for missions beyond that The sunWhere sunlight is dim, nuclear energy is in the form of… Radioisotopic thermogenerators RTGs can also be used to drive electric propulsion.
Although electric propulsion is now mature and used for a variety of tasks, it is not a perfect technology. One problem in particular is that the ion plume could damage the spacecraft. Even though the plume is directed away from the probe, electrons in the plume could find themselves redirected, moving against the plume’s direction of travel and impacting the spacecraft, damaging solar arrays, communications antennas, and any other exposed components. Suffice to say this is not good for investigation.
“For missions that can last for years, [electric propulsion] Thrust devices must operate smoothly and stably over long periods of time timeChen Kui of the University of Virginia’s College of Engineering and Applied Science said: statement.
Before solutions can be developed to protect spacecraft from these scattered electrons, their behavior in the ion engine shaft must first be understood, and that is where Cui and Joseph Wang of the University of Southern California come in. Simulating ion engine exhaust, modeling the thermodynamic behavior of electrons and how they affect the overall properties of the column.
“These particles may be small, but their motion and energy play an important role in determining the macroscopic dynamics of the plume emitted by the electric propulsion motor,” Cui said.
What Cui and Wang found is that the electrons in the column behave differently depending on their temperature and speed.
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“Electrons are a lot like marbles packed into a tube,” Coy said. “Inside the beam, the electrons are hot and moving quickly. Their temperature does not change much if they go in the direction of the beam. However, if the ‘balls’ exit the middle of the tube, they begin to cool. This cooling occurs in a certain direction, which is the direction perpendicular to the direction of the beam. “beam.”
In other words, the electrons in the core of the beam that are moving faster have a more or less constant temperature, but those on the outside cool faster and slow down and move outside the beam, potentially scattering back and impacting the electrons. Spacecraft.
Now that scientists better understand the behavior of electrons in the ion column, they can incorporate this into future electric propulsion engine designs, looking for ways to reduce backscatter, or perhaps confine the electrons more closely to the core of the beam. Ultimately, this could help electric-propelled missions fly further and for longer, propelled by the gentle blue breeze from their ion plume.
