NASA’s DART Spacecraft Will Rely on a Powerful Ion Engine to Fly to Didymos

In spite of the current crisis created by the novel coronavirus, other threats to humanity are still present. The most talked one until now was the threat of a possible asteroid collision on Earth, which has taken a backseat since the outbreak started. However, the threat is still there, astronomers say.

Although an asteroid collision seems rather evanescent at the moment, scientists claim it is a real threat and one that has the potential to actually end humanity as we know it. Space agencies like NASA and the ESA are still developing plans that will allegedly protect us from that hazard.

NASA’s DART Will Collide With Didymos B

NASA’s DART (Double Asteroid Redirection Test) mission is set to take-off on July 22nd of 2021 and will study the use of kinetic impact to deflect a space rock. It will aim the small binary asteroid system known as Didymos, which poses no risk to Earth.

The larger rock in the system, called Didymos A, is approximately 780 meters (2,560 feet) in size, and the smaller one, Didymos B, has a diameter of about 160 meters (535 feet). DART is programmed to collide with Didymos B, which is close to the usual size of an asteroid that could destroy humanity.

After taking off in July 2021, DART will arrive at the asteroid on September 22nd, as the pair of space rocks is about 11 million kilometers (6.8 million miles) from Earth. To reach the target, the vehicle will depend on a powerful ion engine: NASA’s Evolutionary Xenon ThrusterCommercial (NEXT-C).

This engine has two main parts: the thruster and the power processing unit (PPU). The probe is currently prepared for the mission by undergoing several tests, both in performance and environment. The thruster was placed through vibration, thermal vacuum, and performance tests before it was connected to the PPU, and was subjected to simulated spaceflight settings, such as intense vibration and extremely cold temperatures.

How DART Works

NEXT-C is a powerful engine that doesn’t resemble a rocket, which needs an enormous quantity of thrust in order to lift something from Earth. Still, when it comes to ion drives, it is an incredibly powerful product, about three times more potent than the NSTAR ion drives on NASA’s DAWN and Deep Space One probes.

NEXT is able to generate 6.9 kW thrust power and 236 mN thrust as it was created to produce the highest total impulse of any ion engine ever developed: 17 MN·s. Ion engines do not burn thrust like a rocket, although they do use a propellant: usually, the fuel is xenon.

This particular ion drive is a double-grid system, with the xenon being placed into a chamber where it hits the upper grid. Solar arrays generate electricity, the upstream grid is charged positive, and as the fuel ions move through the upper grid, they are also charged positively. The xenon then moves toward the second, or accelerator grid, which is, you guessed it, charged negatively. This sends the ions out of the engine, generating thrust which is identical to the force between the upper ions and the accelerator grids.

Follow-up Missions to Observe the Impacts

DART will be accompanied by the Italian Space Agency‘s LICIA (Light Italian CubeSat for Imaging of Asteroids) in the mission to the Didymos binary system. LICIA is a set of six cube satellites that will split form DART after the collision with the small asteroid. It is programmed to take pictures of the impact and the junk produced by the crash and send the data back to Earth.

The collision is expected to alter Didymos B’s orbital speed by around a half-millimeter per second. That will change its spin period by a sufficient amount that Earth-based telescopes will be able to identify it.

Although DART will obviously be destroyed during the crash, the ESA is setting up a monitoring mission, called HERA, and set to launch in 2024, with the arrival date to the site scheduled for 2027. HERA will observe the effects of the collision created by DART, and will also be equipped with numerous tools that will help it learn more about binary asteroids.

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