Propellant leak forces Sherpa tug off SpaceX rideshare mission

WASHINGTON – A Sherpa tug was removed from an upcoming SpaceX rideshare mission after its propulsion system developed a leak, forcing Spaceflight to find new trips for 10 cubesats.

Spaceflight said on December 21 that, after integrating its Sherpa-LTC vehicle with SpaceX equipment for the Transporter-3 mission scheduled to launch in mid-January, technicians discovered a leak in the Sherpa’s propulsion system. That propulsion system, provided by Benchmark Space Systems, had just been installed and powered prior to integration.

“At this time we believe there is no damage to any customer spacecraft or safety concerns, but it is a significant advance,” the company said. “As a precaution, we have decided not to fly the Sherpa-LTC1 on our SXRS-6 mission.”

Jodi Sorensen, a spokeswoman for Spaceflight, said the leak was discovered on December 21. The Sherpa was removed from SpaceX’s launch hardware and will be sent back to Spaceflight’s facility in Auburn, Washington, for analysis. “We will continue to work closely with Benchmark to find out the root cause of the leak, but nothing is definitive at this time,” he said.

The leak was discovered the same day that Benchmark announced that its thrusters had been installed in Sherpa and powered. Halcyon Avant propellants use high-performance hydrocarbon and peroxide propellants that offer performance similar to systems using hydrazine and mixed oxides of nitrogen, company officials said, without the handling challenges of those toxic propellants.

The Halcyon Avant thrusters installed on Sherpa-LTC1 are the first scheduled to go into space after completing tests on the ground. A company spokesperson referred questions about the leak to Spaceflight.

The removal of the Sherpa from the Transporter-3 launch affects 10 cubesats that would have been deployed from it. Three larger synthetic aperture radar satellites, two from Capella Space and one from Umbra, are connected to different ports on the Falcon 9 payload adapter and will continue to fly on the SXRS-6 mission, Spaceflight said.

The affected satellites include four Kleos Space cubosats named Patrol Mission by the company. That set of cubesats, your third group of cubesats, is designed for radio frequency geolocation. Lynk Global had its first commercial satellite, Lynk Tower 1, on Sherpa when the company began rolling out its satellite phone services.

NASA’s Low Latitude Ionosphere / Thermosphere Density Enhancements, or LLITED, mission features two 1.5-unit cubosats developed by The Aerospace Corporation to study aspects of the nocturnal upper atmosphere. That mission was intended to make use of the Sherpa’s propulsion system, maneuvering in a lower orbit to free those cubesats.

The Czech Aerospace Research Center and small satellite maker Spacemanic were flying the three-unit Cubesat VZLUSAT-2 to demonstrate technologies for a future constellation of Czech satellites. German company Space Products and Innovation had SPiN-1, a one-unit technology demonstration cubesat. The Portland State Aerospace Society has OreSat0, a one-unit cubesat built by college students using open source technologies.

Spaceflight says it is working to remanifest those satellites in other launches. “Leaving no stone unturned, we’re doing our best to find pitches for them as quickly as possible,” Sorensen said. He later said that Spaceflight worked with another payload integrator to re-manifest a customer on Transporter-3.

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