by WASHINGTON — A Sherpa tug that was launched a month ago is still under commissioning and has yet to begin maneuvering as its orbit gradually wears out.
Spaceflight Inc.’s Sherpa-LTC2 tug. launched on September 4 as the payload on a Falcon 9 launch of 51 Starlink satellites from the Cape Canaveral Space Station in Florida. The rocket placed the payloads into an initial orbit of about 310 kilometers.
Spaceflight planned to use a chemical propulsion system on Sherpa, provided by Benchmark Space Systems, to raise the vehicle’s orbit to an altitude of 1,000 kilometers. The Sherpa payload, initially undisclosed by Spaceflight, is a V-band communications demonstrator from Boeing called the Varuna.
However, tracking information from the US Space Force indicates that Sherpa has not yet reached orbit. Atmospheric drag caused this orbit to gradually decay, and the spacecraft was recently tracked in a 283 by 296 kilometer orbit. This raised concerns that the spacecraft could come back in a few weeks if it does not start firing its thrusters.
Spaceflight spokeswoman Jodi Sorenson told SpaceNews on Oct. 4 that the company continues to go through the post-launch award process for the Sherpa tug. “As always with experimental first-flight systems, the commissioning process is fluid,” he said, with orbit-raising maneuvers beginning as soon as commissioning is complete. He did not give an estimate of when the spacecraft’s commissioning would be completed.
The Sherpa-LTC2 is the first of Spaceflight’s Sherpa series of tugs to launch with this high-performance chemical propulsion system. The original Sherpa-LTC tug was scheduled to launch on a SpaceX Transporter sharing mission in January, but was pulled due to leaks in that propulsion system. This was one of a series of events that led SpaceX to announce in March that it would not fly Spaceflight payloads on rideshare missions after those that had already taken place.
Curt Blake, Spaceflight’s chief executive, said in August that the company had “gone through all kinds of checks to get things right” before launching Sherpa-LTC2.
The Sherpa-LTC is part of a line of Sherpa vehicles that includes versions without propulsion systems, with attitude control thrusters and with electric propulsion. Another Sherpa vehicle, the Sherpa-ES, will carry a chemical propulsion system with high delta-V, or change in velocity, performance for a mission that will carry cargo on a “lunar slingshot” mission around the Moon in geostationary orbit in 2023.
