Despite thruster difficulties, an Astroscale debris-removal demonstration gets close

Space Technology

Astroscale announced on May 4 that it accomplished another close approach rendezvous between its dual ELSA-d spacecraft last month, although that persisting thruster issues are delaying a capture demonstration that was originally scheduled for January.

In January, four of Astroscale’s eight 1-newton thrusters failed aboard the ELSA-d servicer spacecraft, which is a 175-kilogram satellite meant to showcase orbital debris removal methods. Despite the mishap, Astroscale successfully directed ELSA-d’s servicer vessel to approach the much smaller client spacecraft on April 7 from a distance of about 1,700 kilometers.

According to Mike Lindsay, Astroscale CTO (chief technology officer), the rendezvous brought the 17-kilogram client craft into a range of the servicer’s low-power radio (LPR) sensors, allowing it to take control over the navigational controls from the ground.

The flawless hand-off to the servicer’s onboard sensors, according to Lindsay, was a serious technological feat that Astroscale had not intended to test before ELSA-d’s propulsion troubles forced the team to reconsider the mission.

When ELSA-d’s propulsion anomaly occurred on January 25, Astroscale was preparing for a capture demonstration, leading the corporation to transfer the servicer to a location beyond the coverage of its own onboard sensors. The servicer craft is fitted with eight 1-newton HPGP (High-Performance Green Propulsion) thrusters from ECAPS, a Swedish propulsion company owned by Bradford Space in the United States.

Last month, Bradford Space, who works as the Chief Executive Officer Ian Fichtenbaum informed SpaceNews that the thrusters on ELSA-d are not at fault. “These concerns have nothing to do with the thrusters’ design or construction, and we have complete trust in our products,” he stated.

Astroscale reported in a May 4 press release that the loss of three thrusters was due to a “system fault,” but that “the principal reason for the loss of the 4th thruster is not obvious and is under joint examination by Astroscale and Bradford/ECAPS.”

Astroscale does not anticipate to put any of the 4 thrusters online, according to Lindsay. The servicer is still maneuverable since the failing thrusters are not all located on one side. When the thrusters failed on the ELSA-d servicer, no propellant was lost, according to Lindsay, leaving the spaceship with sufficient fuel to capture as well as de-orbit the client vessel if Astroscale chose to go forward with that aspect of the mission.

Although the servicer was successful in releasing and recapturing the client using its magnetic technique last August, Astroscale planned to try again with less direct ground support. Lindsay said Astroscale certified the servicer’s LPR sensor for this station-keeping it was going to require for this semi-autonomous capture demonstration before the testing in January was called off.

“At that moment, the spacecraft basically says, ‘I understand where the client is, and I know what I require to do to get nearer to the client and accomplish the rendezvous,'” Lindsay explained.

If Astroscale goes through with a semi-autonomous capture effort, ground operators will still be necessary to perform several safety checks. If the servicer’s next capture try goes ahead, it will approach the client craft from a larger distance than the August capture mission.

Ground operators assumed charge of the servicer’s navigation after the April 7 rendezvous, moving it around 300 kilometers (kms) away from client to an orbital location where it may remain stable for numerous months.

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