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In-Orbit
Refuelling

Advanced propulsion and fluid management for the next generation of satellite life extension.

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1.0 IN-ORBIT REFUELING INITIATIVE

WHY

In-orbit refueling is a key capability needed to move space programs to the next level.
As constellations grow and missions become more complex, spacecraft will require the ability to refuel in orbit.For this ecosystem to scale, refueling cannot remain proprietary. It must become standardized and interoperable across vendors.

This initiative is a systems engineering effort aimed at helping move the industry toward that goal.

Space logistics will scale only when interoperability becomes possible.

HOW

By bringing together engineers, architects, and domain experts from across the global space community.Using Model-Based Systems Engineering (MBSE), we collaboratively explore mission concepts, operational architectures, system functions, and interface ideas that could enable multi-vendor compatibility.

The objective is to think through the problem at a true system level, not from the perspective of a single spacecraft or company.

WHAT

The outcome of this effort is a practical systems-engineering framework for in-orbit refueling.A framework that organizations can reference while developing their own vehicles, depots, docking systems, or operational concepts.

The long-term vision is simple: Any compatible servicing vehicle should be able to refuel any compatible client spacecraft.

WHY JOIN THIS INITIATIVE

This is a self-directed engineering initiative where you will be challenged to develop mastery of systems engineering while contributing to a real-world space project with a meaningful purpose.Contributors have the autonomy to explore ideas, challenge assumptions, and help shape the architecture of a real space infrastructure concept.

Participants will work through the full systems engineering process applied to a complex space mission, including:

  • Mission context
  • Operational concepts
  • Functional architecture
  • System requirements
  • Interface thinking

The goal is not only contribution, but mastery. You will be challenged to think at the level required for real space programs.

And the purpose is meaningful. This effort contributes toward something the space industry will eventually need: a practical foundation for interoperable in-orbit refueling.If you work in spacecraft design, propulsion, mission operations, docking systems, autonomy, or space infrastructure — and want to explore this problem with other engineers — you are welcome to participate.

Objective for Current Week

Current Week: March 12, 2026 –

Review existing artifacts

Participation

Contributions can be made in two ways

Contributors (Core Team)

Participate in the systems engineering work, join discussions, and develop artifacts within the project (Confluence backend).
Also provide technical input and improvements to the evolving artifacts.

Reviewers

Provide critical feedback, research insights, and technical comments on the published material to improve the quality and realism of the concept.lue.

Expertise Required

This initiative requires feedback in many areas including:

  1. Launch and In Orbit insertion
  2. Optimization – Propellant delivering solution must itself be optimized
    1. Location of IOR system
    2. Size of Depot and SV
  3. RPOD operations
    1. Trajectory and maneuver planning for plane and phase alignment
    2. Proximity Operations
    3. Docking/Undocking
    4. Fuel Transfer systems
  4. Return to Depot Guidance
  5. Debris Avoidance (Nominal and During RPOD operations)

Skills Required

  1. Space Skills: RPOD, Proximity Operations, Docking, Launch, In Orbit Insertion
  2. Space Calculations: Calculate Delta V, Trajectory, Propellant Use, Propulsion required
  3. Engineering Skills: LiDAR, AI, Image Processing
  4. Engineering: Mechanical, Space, Electronics
  5. Skills/Tools: Systems Engineering, MBSE, Capella, ARCADIA, SysML, Catia, Jira, Confluence

Want to Participate or Have Questions?

To participate:

  • Review the Terms and Conditions
  • Review the project pages
  • Send your interest with contribution type (Author or Feedback) and relevant space experience

Relevant experience may include RPOD, ISAM, payload systems, GNC, or launch systems.

Contact: ior.project@reliqai.com

A user ID and password will be issued to enable commenting and participation.

You can learn more about In-Orbit Refueling (IOR) here.

Refer to FAQ here