The EU-funded SpaceUSB project has validated a Common Passive Interface (CPI) designed to work as a shared mechanical and electrical connection point for spacecraft servicing. Rather than replacing every existing satellite interface, the CPI is intended to create an interoperability layer between major European service-interface families: HOTDOCK, SIROM and iSSI. The result is a tested prototype that could make future satellites easier to dock with, repair, refuel, upgrade or assemble in orbit.
SpaceUSB's final work is significant because in-space servicing depends on physical compatibility. When spacecraft use bespoke connectors, servicing vehicles and replacement hardware must be designed around the particular interface used on a mission. A common connector baseline could reduce that fragmentation for future modular spacecraft architectures. The project remains a laboratory-validated and standardization-focused development, not an orbital deployment.
The consortium's final CPI demonstration video and project update shows the interface's design and validation campaign. That campaign included mechanical docking, electrical connectivity and data-transfer tests, plus a representative orbital replacement unit, or ORU, configuration.
How the Common Passive Interface works
CPI is described as a mechanical and electrical envelope that enables power and data transfer when two space elements dock. Its purpose is not to require every participant to abandon an established service interface. Instead, it is designed to bridge the three European interface families that SpaceUSB identified as its target: HOTDOCK, SIROM and iSSI.
That distinction matters. The project is pursuing interoperability at the connection layer, which could allow components built around different established interfaces to participate in a shared servicing ecosystem. The laboratory results demonstrated both physical mating and electrical and data connectivity across the target interface families.
| Approach | Interface relationship | What SpaceUSB demonstrated |
|---|---|---|
| Existing European service interfaces | HOTDOCK, SIROM and iSSI are separate interface families. | They are the CPI's intended interoperability targets. |
| SpaceUSB Common Passive Interface | A common layer designed to bridge the three interface families without mission-wide replacement of each partner's interface. | Mechanical docking plus electrical and data-transfer testing in a laboratory and test-bed setting. |
The design supports concepts including modular docking, servicing, refueling and on-orbit assembly. Those are future applications enabled by compatible spacecraft architectures, not services that CPI itself has deployed. Its importance lies in giving mission designers a potential common foundation before hardware is launched.
The Horizon Europe project, under Grant Agreement 101135215, formally ended on 31 December 2025 following its final review process with the European Commission and HaDEA. The consortium published its final video in February 2026. CPI specifications are available on request, an approach intended to support continued standardization and industry uptake.
What CPI could change for the space market
For satellite operators, a repairable or upgradeable spacecraft can only be practical if a servicing mission can reliably connect to it. A shared interface could reduce the need for one-off hardware adaptations in future serviceable missions. That may support longer-lived spacecraft designs and, where satellites are built for servicing, reduce pressure to replace hardware that could otherwise be repaired or upgraded.
The potential debris benefit also needs to be understood correctly. CPI does not remove debris from orbit and has not been demonstrated in space. Its possible contribution is architectural: if more spacecraft can be maintained, upgraded or handled through compatible servicing systems, modular mission designs may offer an alternative to treating every failed or outdated component as fully disposable.
For startups and smaller suppliers, the most immediate opportunity is not a guaranteed new market but a clearer technical target. A common baseline could make it less necessary to commit early to several bespoke connector strategies. Businesses working on replacement units, robotic servicing hardware, satellite components, test equipment or service-planning software could have a more interoperable ecosystem to design around if CPI gains wider adoption.
Practical implications include:
- Hardware suppliers could design modular components around a common connection concept rather than a single isolated servicing family.
- Satellite-as-a-service providers could potentially plan missions around replaceable units and compatible servicing paths.
- Earth-observation operators could eventually benefit from spacecraft architectures that are designed for hardware upgrades, where mission economics support that approach.
- Testing and integration specialists could find demand for validating how components perform across interoperable service interfaces.
There are still important limits. SpaceUSB has demonstrated feasibility in laboratory and test-bed conditions, not in orbit. The research does not announce a first flight mission, commercial availability date or universal industry mandate. It also does not define a completed regulatory route for CPI-enabled servicing missions. Any operational use will depend on future spacecraft designs, mission partners, standards adoption and the requirements governing individual missions.
For businesses, the near-term question is whether to monitor CPI as a design and partnership signal rather than treat it as an off-the-shelf orbital servicing solution. The strongest value would emerge if future European missions and suppliers adopt the interface as a common building block.
For companies exploring modular spacecraft services, the hardware interface is only one part of the operational challenge. Teams also need reliable systems for mission data, partner workflows and service coordination as concepts move toward deployment. Scalevise can help translate complex operational requirements into custom software and integration projects that replace disconnected processes with practical tools. Discuss a custom software project with Scalevise.
Frequently Asked Questions
What is the SpaceUSB Common Passive Interface?
The Common Passive Interface, or CPI, is a mechanical and electrical connection envelope developed by SpaceUSB. It is designed to transfer power and data between docked space elements and bridge HOTDOCK, SIROM and iSSI service-interface families.
Has SpaceUSB deployed the CPI in orbit?
No. SpaceUSB validated CPI through laboratory and test-bed demonstrations, including mechanical docking and electrical and data-transfer tests. The supplied research does not identify an orbital deployment.
What satellite servicing tasks could CPI support?
The project positions CPI as a building block for modular docking, servicing, refueling and on-orbit assembly concepts. Actual use depends on future spacecraft and missions adopting compatible architectures.
When did the SpaceUSB project end?
The Horizon Europe SpaceUSB project formally ended on 31 December 2025. Its consortium published a final video in February 2026 covering CPI's design and validation work.
Conclusion
SpaceUSB has delivered and tested a credible interoperability building block for European in-space servicing. CPI does not yet represent an operational universal connector in orbit, but its validated ability to bridge HOTDOCK, SIROM and iSSI addresses a core obstacle to modular satellite maintenance. Its long-term value will depend on adoption in future spacecraft and servicing missions.
