WASHINGTON — The U.S. Space Force is preparing a series of experiments to test in-space satellite refueling technologies, positioning commercial competitors at the forefront of an emerging sector of the space industry.
The planned demonstrations, known as Tetra-5 and Tetra-6, will evaluate refueling hardware from Astroscale, Northrop Grumman, and Orbit Fab — companies vying for dominance in the nascent orbital refueling market.
These experiments are seen as critical steps toward establishing a sustainable commercial refueling architecture in space. “Tetra-5 will validate the interface and a scalable commercial refueling architecture,” a Space Systems Command spokesperson said in a statement to SpaceNews.
Initially conceived in 2022 as a single $44.5 million experiment scheduled for 2025, the program has since been split into two separate missions: Tetra-5, launching in 2026, and Tetra-6, following in 2027.
Tetra-5: Testing commercial interfaces
The Tetra-5 mission will deploy two small satellites equipped with Orbit Fab’s Rapidly Attachable Fluid Transfer Interface (RAFTI), a specialized valve designed to enable on-orbit propellant transfers.
One satellite will attempt to dock with an Orbit Fab propellant depot developed with Pentagon funding through the Defense Innovation Unit. The second will test compatibility with an Astroscale U.S. propellant shuttle being developed in partnership with Space Systems Command’s Servicing, Mobility, and Logistics office.
Tetra-6: Northrop Grumman’s solution
The following year, Tetra-6 will test Northrop Grumman’s Passive Refueling Module (PRM), also developed with Defense Innovation Unit backing. This mission will deploy a single satellite equipped with the PRM interface, which will attempt to dock with Northrop Grumman’s ROOSTER-5 (Rapid On-orbit Space Technology Evaluation Ring) tanker satellite.
This demonstration supports the company’s development of an orbital fuel tanker called Geosynchronous Auxiliary Support Tanker (GAS-T), which would be built on the company’s ESPAStar D ring-shaped satellite bus.
The Space Systems Command said it has approved both the RAFTI and PRM refueling systems “as acceptable commercial solutions for refueling.”
Assessing the technology
Beyond the refueling hardware providers, the Tetra missions involve several other contractors. Arcfield serves as the satellite integrator, while Redwire will supply the satellite buses. The Space Systems Command will handle operations for both missions.
For the Space Force, these experiments will provide crucial data to assess the viability of the emerging in-space logistics industry. The service also wants to gain insight into whether commercial providers can establish sustainable business models without continuous government subsidies.
While Space Force officials have expressed interest in leveraging commercial refueling services, they first require concrete proof that the technology functions reliably in the harsh environment of space.
In-orbit refueling capability, according to companies in the industry, could transform space operations by extending satellite lifespans, enabling greater operational flexibility, and reducing the costs associated with replacing aging satellites.
