A conceptual design of the Augmentation System Port Interface (ASPIN) docking port for satellites using the Mission Augmentation Port (MAP) interface standard. Credit: Lockheed Martin

Servicing satellites in orbit is a nascent segment of the space economy that the U.S. military has been watching mostly from the sidelines.

The Space Force says it is now ready to get in the game. It is investing in early-stage technologies and laying out a strategy to buy commercial services to refuel and service satellites in geostationary orbit by the early 2030s.

The military’s thinking about satellite servicing has changed from just a few years ago when space operators didn’t see a strong use case for in-orbit repairs and refueling. Now it’s viewed as a strategic advantage, said Vice Chief of Space Operations Gen. David Thompson.

The Space Force considers satellite servicing and in-orbit logistics as “core capabilities” and is watching developments in the commercial industry, said Thompson.

“We are ready to use the technology as soon as the market is there,” he said May 15 at a Space Force Association event. Meanwhile, “there is a whole bunch of design and analysis we have to do to figure out what makes sense.”

Lt. Gen. John Shaw, U.S. Space Command deputy commander, outlines requirements for sustained maneuver and dynamic space operations at the Space Warfighters Luncheon during the 38th Space Symposium, Colorado Springs, April 19, 2023.

Congress signaled support for these efforts, inserting $30 million in the 2023 Space Force budget for on-orbit servicing technologies. Thompson last year directed the Space Systems Command to use the funds to establish a program office and figure out a procurement strategy for satellite servicing.

The new office is just starting to get off the ground, said Maj. Gen. Stephen Purdy, program executive officer for assured access to space at the Space Systems Command.

Purdy said military space operators are sending a clear demand signal for in-orbit capabilities, and the goal is to create a dedicated budget line for these services.

“It’s a little bit of the classic starter’s dilemma,” he told SpaceNews, noting that starting new programs in the Defense Department is notoriously cumbersome. Meanwhile, “there is a desire to have a refueling capability.”

‘We need logistics’

A strong case for satellite refueling has been laid out by Lt. Gen. John Shaw, deputy commander of U.S. Space Command. At recent industry events, Shaw argued that the way DoD has acquired satellites for decades — without a capability to refuel in orbit — prevents operators from freely maneuvering spacecraft in response to threats.

Shaw compared it to buying a car with a single tank of fuel and having to make it last for the entire lifetime of the vehicle.

“We need to have on-orbit logistics and service capabilities,” Shaw said in a speech at the Space Symposium in April.

Space Command, for example, operates “neighborhood watch” satellites known as GSSAP (Geosynchronous Space Situational Awareness Program) to monitor the geostationary belt, where the military deploys its most valuable assets. GSSAPs were built to last for decades, but maneuvers must be carefully planned to minimize fuel consumption.

“If I had the ability to refuel GSSAP regularly, do you think we would operate them like we do today? We would not,” Shaw said. “We would be zipping around the globe. We’d be trying to keep a potential adversary off balance.”

Purdy said that message has been heard loud and clear.

“We cannot do warfighting in the space domain if we have to measure every drop of fuel and decide whether you really want to do this mission if that means the satellite will run out of fuel two years early,” he said.

Projects in the works

Purdy assigned Col. Meredith Beg to lead the new Space Force office focused on space mobility and logistics.

“Our goal is to ensure that we can deliver this capability that the combatant command is clamoring for,” Beg told SpaceNews.

“We don’t have a defined budget yet. But we are working through the corporate process to establish what that needs to look like,” she said.

An artist’s rendering of a Mission Extension Pod attached to a client vehicle.

Satellite servicing is part of the broader activity known as ISAM, for in-space servicing, assembly and manufacturing. The Space Force is interested in ISAM, but its major focus is mobility and maneuver, said Beg. Refueling is the “near-term requirement.”

These technologies also are being pursued by Space Force under the Orbital Prime program aimed at small businesses. Launched in 2021, Orbital Prime has awarded about 125 research and study contracts to teams of industry and academia.

Outside the Space Force, other organizations funding in-orbit satellite servicing programs include the Air Force Research Laboratory and the Defense Innovation Unit. But the most significant investment today is coming from the private sector, Beg noted. “We’re looking to leverage all that hard work and brainpower to actually deliver capabilities to our warfighters.”

Of the $30 million Congress added in 2023, $26 million will be allocated to projects managed by the Space Enterprise Consortium, a Space Systems Command organization that works with startups and commercial space firms.

In June, the SpEC consortium plans to request prototype proposals “to support the development of a robust commercial base capable of providing space mobility and logistics services.”

SpEC, in a draft solicitation, noted that few commercial services are available. “However, multiple performers are working towards technology demonstration.”

Proposals are sought in four areas: refueling, transportation, servicing and debris mitigation.

The SpEC plans to award one or more contracts for projects that will be co-funded by the $26 million appropriated in the Space Force budget and $7.8 million from the winning contractors. Developing technologies under private-public partnerships allows the Space Force to influence commercial technology development.

Refueling demonstration planned

Beg said a long-term acquisition strategy for refueling and other in-orbit services is still to be mapped out.

To help inform the procurement strategy for in-orbit refueling, the Space Force is funding experiments such as the $50 million Tetra-5, co-sponsored by the Defense Innovation Unit.

The Space Systems Command’s Innovation and Prototyping Directorate last summer awarded Orion Space Solutions a contract to develop three small satellites that will dock with a hydrazine depot in geostationary orbit supplied by the commercial startup Orbit Fab. The experiment is projected to launch in 2025.

The head of the prototyping directorate, Col. Joseph Roth, said the Tetra-5 experiment, if successful, will help build confidence in the technology.

“Colonel Beg and the rest of us are getting really strong signals from the warfighting units that they want to have on-orbit refueling capability and logistics,” said Roth. “It will take time to establish requirements and put in the budget, but it’s pretty exciting to see.”

DARPA pioneered in-orbit servicing

For years, Josh Davis, senior project engineer at the Aerospace Corp., has studied developments in space mobility and logistics.

The Defense Advanced Research Projects Agency (DARPA) in 2007 demonstrated in-orbit refueling in an experiment called Orbital Express. Although the project was successful, Davis noted, the military never transitioned the technology to an operational program because there was no actual need for it.

The Air Force operated satellites in space for more than 50 years without refueling or in-space logistics capabilities, Davis said. Now that a need has been identified, the Space Force has to work through the Pentagon’s requirements process. “From a budgeting perspective, it’s very hard to stand up a new mission area,” he said.

Transitioning to a satellite fleet that can be serviced in orbit, he said, also requires building next-generation spacecraft equipped with refueling ports compatible with available servicing vehicles.

The good news for the Space Force, Davis said, is that the industry has advanced rapidly since Orbital Express. There are now commercial companies able to provide services, so the government doesn’t have to build unique systems.

DARPA, in 2020, signed an agreement to share its satellite servicing technology with a commercial firm, Northrop Grumman’s SpaceLogistics. The company now has two Mission Extension Vehicles in orbit docked with two Intelsat geostationary satellites that were running low on fuel, and will keep those satellites in service for about 15 years.

A Rendering of Orbit Fab’s refueling depot in space.

Satellite operators Intelsat and Optus have ordered two of three fuel pods to be delivered by SpaceLogistics’ new Mission Robotic Vehicle, projected to launch in 2024 to extend the life of geostationary satellites by at least six years. The third customer has not yet been announced.

Despite uncertainty about DoD funding for satellite servicing, the industry is making investments in anticipation of government demand, Davis said.

He pointed to Shaw’s comments as a “very clear demand signal from the Space Force’s customer, U.S. Space Command.”

Standard interfaces for spacecraft

For the satellite servicing industry to take off, Davis said, decisions will have to be made about hardware and software interfaces to make vehicles interoperable.

“As we move forward, there is definitely a lot of interest in figuring out how we standardize the servicing features on our next generation of satellites,” he said.

Volumes of standards have been developed for NASA programs such as the International Space Station, but those are not applicable to military satellites.

The Space Force has a lot of work to do in this area, Davis said. It is unlikely that the industry will adopt the equivalent of a USB plug-and-play standard for spacecraft, at least in the foreseeable future, Davis added. “Eventually, I would love to get there.”

Companies like Northrop Grumman, Lockheed Martin, Astroscale, Orbit Fab and others are developing interfaces, and some may be more widely adopted than others. “Somebody is going to get the market first, and they’re going to get the lion’s share,” said Davis.

He noted that the industry group known as CONFERS (Consortium for Execution of Rendezvous and Servicing Operations) will have an important role to play in this area.

CONFERS was founded by DARPA in 2017 to help develop and promote industry-led standards for satellite servicing activities. The consortium has more than 50 member organizations from the U.S. and several other countries.

Roth, the director of prototyping at Space Systems Command, said government and industry experiments will help test different interfaces “to see which works the best.”

“We do keep our eye on the industrial base,” particularly on satellite refueling developments,” he said. “We’re just at the early stages of on-orbit refueling, and I’m glad we have a robust industrial base that’s actually exploring this for commercial use.”

Roth said the Space Force is closely watching Northrop Grumman’s servicing vehicles and the company’s next-generation mission refueling pods. “We are definitely going after commercial opportunities,” he said.

Open-source docking device

With an eye on the military satellite servicing market, Lockheed Martin in April 2022 released the technical specifications of a docking device — called Augmentation System Port Interface, or Aspin. Lockheed Martin hopes satellite manufacturers will adopt the standard in order to make satellites interoperable and easier to update on orbit with new technology.

“We are definitely looking at that port,” Roth said. An attractive feature of Aspin, he said, is that it was designed to be compatible with Orbit Fab’s refueling port called Rafti — short for rapidly attachable fluid transfer interface.

Lockheed Martin’s vice president of mission strategy Eric Brown said the Aspin port was designed to enable a broad range of services, including refueling satellites, recharging batteries or adding new payloads.

“We’re seeing the demand signals coming from the right places, certainly for refueling,” Brown said.

In addition to Aspin, the company is investing in rendezvous and proximity operations technology. Two Lockheed Martin cubesats conducted a demonstration in geostationary orbit in November, performing maneuvers in close proximity.

In the experiment called Lockheed Martin’s In-space Upgrade Satellite System, or Linuss, one of the cubesats performed the role of servicing vehicle and the other served as the resident space object.

Brown said Lockheed Martin is planning a new experiment to test the Aspin docking adapter in space.

“We expect Aspin to be stock content on any satellite that we intend to propose to the U.S. government and allies,” Brown said. “And we expect that every satellite program that the Space Force procures is going to ask for the ability to be refueled.”

Lockheed Martin, an investor in Orbit Fab, purposely designed Aspin to be interoperable with the Rafti port. But Aspin also will enable other capabilities such as snapping on a new processor to a satellite.

One of the concepts envisioned for Aspin is to put the port on a small satellite carrying a new processor or sensor that would be launched to orbit and, under its own propulsion, dock with the client satellite.

“The problem we have today is you design these satellites over the course of several years, and technology continues to evolve,” Brown said. Technologies like Aspin would allow the Space Force to update their satellites relatively quickly.

Gas stations in space

Orbit Fab announced plans in 2022 to offer refueling services in geostationary orbit by 2025 at a price of $20 million for 100 kilograms of hydrazine.

The company will deploy a depot and “shuttle” spacecraft to take fuel to satellites.

Adam Harris, Orbit Fab’s vice president of business development, said the company continues to push these projects forward with private funding but also relies on government support.

The company secured a $12 million U.S. Air Force Strategic Funding Increase — with $6 million coming from the Air Force and $6 million in matching private funds — to further develop its Rafti refueling port for compatibility with military satellites.

The Rafti port has to be installed on the client satellite in order to receive fuel. Orbit Fab also is developing a grappling device for the fuel delivery vehicle that attaches to the Rafti port.

In the Tetra-5 experiment, a small satellite will rendezvous and dock with Orbit Fab’s depot to get hydrazine. Orbit Fab on May 25 announced it selected Impulse Space’s orbital transfer vehicle as the hosting platform for the fuel depot. The OTV will supply power, communications, attitude control and propulsion for the fuel depot.

The military’s seemingly growing appetite for refueling capabilities is “very exciting for us,” Harris said.

“When Lockheed Martin, Northrop Grumman or other companies build spacecraft, we talk to them about how you can integrate our refueling interface so that those spacecraft can be refillable,” he said. “We want to make that as easy as possible for all spacecraft manufacturers.”

Space Command is telling the Space Force it wants refuelable satellites by 2030. Although that seems a long way off, planning for that future has to start now, Harris said.

“When you know refueling is available, you can change the way you do business with spacecraft,” he said. “And you can make those maneuvers without regret.”

This article originally appeared in the June 2023 issue of SpaceNews magazine.

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...