NASA Tests Osiris-REx Thruster on the Way to Asteroid Bennu

Traveling beyond the low-Earth orbit requires precision and pre-calculated maneuvers. Aside from that, every spacecraft tasked to go somewhere deeper in space requires innovative systems and engines including thrusters. NASA test fired OSIRIS-REx thrusters while the spacecraft is on its way to a rendezvous with asteroid Bennu.

OSIRIS-REx was launched into space last September. The mission is to perform a comprehensive surface mapping of an asteroid to give more information about the formation of Earth and the Solar System because asteroids are believed to be one of the oldest space rocks.

The spacecraft fired its Trajectory Correction Maneuver (TCM) thrusters last Friday, Oct. 7, for the first time. This was done to fine-tune the path of the spacecraft from Earth to its target asteroid, Bennu. This sensitive maneuver was carefully executed last Friday. The process began at 1:00 pm and successfully fired the thrusters for 12 seconds. The outcome of the test fire is a slight change in the spacecraft’s velocity by 1.1 miles (50 centimeters per second) per hour. The maneuver also used about 18 ounces of OSIRIS-REx fuel. At the moment, the spacecraft is already nine million miles (14.5 million kilometers) away from the planet.

But this thruster test is not a surprise; it is already included in the flight plan to correct its trajectory if there’s a need for it after lift-off on Sept. 8. The spacecraft was propelled by United Launch Alliance (ULA) Atlas V rocket; the rocket was very accurate with its calculations that fine-tuning of the spacecraft’s trajectory was not necessary. However, NASA scientists still decided to test fire the thrusters to see  its capacity and to prepare for bigger “propulsive maneuver” that is set to take place in December.

Engineers in charge of OSIRIS-REx plan for future trajectory corrections and its fuel consumptions are already included in its propellant load.  “The mission had allocated approximately 388 ounces (11 kilograms) of propellant for TCM-1 to create a velocity change of up to 26 miles per hour (11.6 meters per second), had it been necessary,” a NASA official said in a press release.

Precise path calculations will require less fuel consumption so this means that the OSIRIS-REx spacecraft is actually saving up on fuel. The path of the spacecraft is being monitored by the Doppler shift in radio signals to the Deep Space Network at the Goldstone Observatory in California. Soon, the navigation team will  process daily reports to determine the exact effect of the thruster test to the movement of the spacecraft.

All in all, there are four different thrusters aboard OSIRIS-REx that will enable the spacecraft to go to asteroid Bennu and back to Earth. The asteroid-sampling mission is one of the most ambitious and most difficult NASA missions yet because it will require the spacecraft to land on an asteroid and to travel back to Earth to deliver the samples. This is the reason why OSIRIS-REx has a number of thrusters aboard.

This December, OSIRIS-REx will activate its Main Engine (ME) thrusters to help the spacecraft reach the path for its Earth Gravity Assist on Sept. 22, 2017, while the smaller thrusters will be used in maneuvering near the surface of the asteroid.


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