En route to an asteroid, the Psyche probe fired its ion thrusters

En route to an asteroid, the Psyche probe fired its ion thrusters
En route to an asteroid, the Psyche probe fired its ion thrusters

More than 300 million kilometers from Earth, the Psyche probe has just turned on its ion propulsion system to venture into deep space to meet the mysterious metallic asteroid Psyche.

The mission took off on October 13 aboard a SpaceX Falcon Heavy rocket. The first 100 days were spent testing the ship’s scientific systems and instruments. After six months of flight, Psyche therefore activated its four Hall effect thrusters which use the electricity produced by the ship’s solar panels to ionize xenon gas. These charged ions are accelerated through an electric field to reach a thrust of 15 km per second at the exit of the thruster.

A weak but constant push

These thrusters have very low thrust levels. A single thruster generates 240 millinewtons of thrust, which is roughly equivalent to the force an AA battery would exert on the palm of your hand. But it can operate for months and build up the strength to accelerate to the speeds needed to sail that far. According to data communicated by NASA, Psyche is currently moving at a speed of 135,000 km/h. Over time, the probe will accelerate to 200,000 km/h.

photo credit: © NASA/JPL-Caltech

This photo shows an ion thruster in operation, identical to those used for NASA’s Psyche spacecraft. The blue glow comes from charged atoms, or ions, of xenon. © NASA/JPL-Caltech

The asteroid Psyche lies in the main asteroid belt between Mars and Jupiter. It is one of nine metallic asteroids detected in our solar system. The probe must reach its destination in 2029. Before that, in May 2026, Psyche will return to Mars and will use its gravitational field. To do this, it will cut off its ion thrusters in order to let itself be caught by Martian gravity in order to accomplish what is called a gravitational slingshot to change its trajectory and regain speed.

Arriving at its destination, Psyche will then begin a 26-month mission punctuated by four observation orbits increasingly closer to the asteroid. Once this step has been completed, the thrusters will be restarted until the ship arrives at its destination. A 26-month mission will then begin, punctuated by four observation orbits increasingly closer to the asteroid.

In addition to its innovative solar propulsion system, Psyché is testing a new very high-speed laser communication technology called Deep Space Optical Communications (DSOC), to which we have devoted a detailed article.

The scientific objectives of the Psyche mission

To carry out its scientific investigation, the probe carries three instruments: a magnetometer to detect traces of an old magnetic field on the asteroid; a gamma-ray and neutron spectrometer to determine its chemical composition; a multispectral imager to study the mineral composition and topography of Psyche.

The asteroid Psyche is still largely mysterious to scientists who have only been able to observe it using radar and telescopes. Researchers believe Psyche is a mixture of rock and metal, with the latter making up 30 and 60 percent of its volume. Two hypotheses currently prevail to explain its origin. The first believes that this asteroid is the remains of the molten metallic core of an embryonic rocky planet like those which gave birth to Mercury, Venus, Mars and Earth.

The second hypothesis makes Psyche a primitive, non-molten body formed from the first materials of the solar system which agglomerates under the effect of gravity. But the mission team admits that these theories may turn out to be partially or even completely wrong. Psyche exploration can reveal crucial information about the origins of several planets in the solar system, starting with our Earth.

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