4 minute read•Updated 12:16 PM EDT, Wed April 2, 2025
The United States Space Force is proceeding with the next phase of on-orbit operations with the development of two groundbreaking missions; Tetra-5 and Tetra-6; to test satellite refueling technologies that could revolutionize space logistics.
These in-space experiments are expected to launch in 2026 and 2027, respectively, and will spotlight commercial companies vying to lead the rapidly emerging in-orbit refueling market.
Catalysts for Commercial Orbital Logistics
Originally announced in 2022 as a single $44.5 million mission, the initiative has since evolved into a two-pronged demonstration series. The missions are intended to evaluate new hardware and validate commercial refueling interfaces in space, laying the groundwork for a sustainable, competitive servicing infrastructure.
Tetra-5 will validate the interface and a commercial refueling architecture. The mission represents a key milestone in proving that privately developed technologies can meet the Space Force's operational and sustainability goals.
Tetra-5: Docking with the Future
Scheduled for launch in 2026, the Tetra-5 mission will feature two small satellites equipped with Orbit Fab’s Rapidly Attachable Fluid Transfer Interface (RAFTI); a key component in enabling orbital propellant transfers.
RAFTI is designed as a standardized valve for cross-platform refueling, and its success could signal the beginning of interoperable fueling systems across public and private spacecraft.
One of the Tetra-5 satellites will attempt to dock with Orbit Fab’s orbital propellant depot, developed in partnership with the Department of Defense’s Defense Innovation Unit (DIU). The other satellite will test compatibility with a propellant shuttle under development by Astroscale U.S., also working with SSC’s Servicing, Mobility, and Logistics (SML) division.
Tetra-6: Northrop Grumman’s Turn
Tetra-6 will follow in 2027, showcasing Northrop Grumman’s Passive Refueling Module (PRM). Like RAFTI, PRM is being developed under the auspices of the DIU and is designed to support autonomous docking and fuel transfer in space.
The Tetra-6 mission will deploy a single satellite outfitted with the PRM interface. The satellite will attempt to dock with ROOSTER-5, Northrop Grumman’s Rapid On-orbit Space Technology Evaluation Ring; a demonstration tanker based on the company’s ESPAStar D platform.
This effort supports the development of GAS-T (Geosynchronous Auxiliary Support Tanker), a scalable fuel depot concept that would reside in geostationary orbit to support a range of commercial and government satellites.
Commercial Solutions Receive Official Approval
Both RAFTI and PRM have been officially endorsed by the Space Systems Command as “acceptable commercial solutions for refueling,” a notable endorsement that underscores the government’s willingness to integrate private-sector innovation into its long-term space strategy.
While the spotlight rests on Orbit Fab, Northrop Grumman, and Astroscale, several other contractors are contributing to the Tetra missions. Defense contractor Arcfield will serve as the primary satellite integrator for both missions, while Redwire will supply the satellite buses.
The Space Systems Command itself will retain operational control of both demonstrations, ensuring mission assurance and the integrity of the test results.
Why In-Orbit Refueling Matters
The implications of successful orbital refueling extend far beyond these individual missions. According to industry experts, reliable in-space refueling could:
Extend satellite operational lifetimes, postponing costly replacements
Enhance maneuverability for defense and commercial missions alike
Lower the overall cost of space operations
Enable long-duration or modular missions that can evolve over time
But before these possibilities can be fully realized, the Space Force wants proof. The Tetra missions are as much about verifying the technical readiness of these systems as they are about evaluating the business case for a commercially viable space servicing ecosystem.
