Why is the US Space Force researching 'orbital warehouses'?

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The U.S. military is looking into putting "orbital warehouses" into orbit around Earth where fuel and other materials could be stored for easy pickup by future spacecraft on satellite servicing missions.

A new U.S. military challenge aims to "accelerate operational logistics" for to help the U.S. Space Force keep its satellites active and respond in a timely fashion to threats. The challenge was created amid repeated warnings that China and Russia are actively maneuvering their own satellites close to U.S. spacecraft in orbit and launching new types of orbital weaponry.

"An orbital warehouse will have the same functionality as a terrestrial warehouse: to receive, store, inspect, and cross-load supplies, while offering protection of those supplies from the environment," a SSC spokesperson told Space.com via email. "The orbital transfer vehicles would transport the supplies to and from the orbital warehouse, or other location of interest."

The challenge, led by Space Force's Space Systems Command (SSC) and SpaceWERX (Space Force's innovation arm), is asking companies to offer fundable ideas for orbital warehouses and orbital "transfer vehicles" that can haul fuel and supplies to and from these depots, as well insight on the best orbits in which to put the depots and vehicles, and how to manage fuel and reusability for longer-term missions. A call-out this summer will offer more details.

There's no timeline available on when these orbital warehouses (or other assets) will be operationally ready, although the SSC spokesperson added that the work is linked with the new "Objective Force 2040" planning document released in April by Space Force, defining where the branch of the U.S. military hopes to be in the next 15 years.

SSC stated the capabilities it is looking for include in-space servicing, propulsion, orbital mechanics, robotics, autonomy, metrology (measurement tools), materials and cryogenics, ground-to-space logistics, and mission analysis.

Planning is already underway for two funded on-orbit demonstrations in 2027 to help inform the requirements of the challenge.

"Starfish Space will build and launch the US-Otter 1, which will demonstrate rendezvous and proximity operations and docking with a client vehicle in near geosynchronous orbit," the SSC spokesperson said in an email. (Geosynchronous orbit is 22,236 miles or 35,786 kilometers above our planet, and allows a spacecraft to remain above a fixed location on Earth.)

Additionally, Astroscale plans to build and launch its Provisioner (or Astroscale Prototype Servicer–Refueler) in partnership with the Air Force Research Laboratory (AFRL), the Defense Innovation Unit (DIU), and two directorates of SSC. The demonstration will use fuel from DIU, stored on a commercial Orbit Fab depot. The Provisioner would then be used to refuel satellites owned by the government: AFRL Tetra-5, and so-far undisclosed SDA satellites.

SSC, the spokesperson stated, fully expects warehouses will be key to future missions using capabilities like those demonstrated by Astroscale and Starfish Space.

A broad sweep of entities can participate in the challenge: anything from startups and small businesses, to larger companies, academia and research labs.