The possibility of refueling satellites on orbit, once the stuff of science fiction, soon could become a reality as companies backed by lucrative commercial investment and U.S. Department of Defense (DOD) contracts move forward with in-space refueling demonstrations. Meanwhile, the U.S. Space Force and U.S. Space Command (USSPACECOM) continue to evaluate refueling for its cost-saving potential.
One frequently cited advantage is the extension of operational lifespans. Traditionally, satellites become inoperable when they deplete their fuel supplies, even if the rest of their hardware continues to function. This can lead to the need for replacement satellites and contribute to the mounting problem of orbital debris. By replenishing fuel supplies on orbit, satellites could extend their mission years beyond their original design lives, maximizing return on investment and reducing the need to manufacture and launch new spacecraft.
Commercial firms maintain that for satellites in geostationary orbit (GEO) — where launch and replacement costs are especially challenging — refueling could be a game-changer. “We’re not just enabling a refueling mission, we’re laying the groundwork for scalable, flexible logistics across space,” Ian Thomas, refueler program manager for Astroscale U.S., said of the company’s upcoming U.S. Space Force fueling demonstration.
Scheduled for mid-2026, the Tetra-5 mission is among several Space Force fueling demonstrations over the next two years. Astroscale made an announcement during the April 2025 Space Symposium in Colorado Springs, Colorado, that its Refueler APS-R spacecraft would be the first “to conduct hydrazine refueling operations above GEO and will be the first-ever on-orbit refueling mission supporting a DOD asset.”
“We’re not just enabling a refueling mission, we’re laying the groundwork for scalable, flexible logistics across space.” ~ Ian Thomas, refueler program manager for Astroscale U.S.
Also in 2026, Orion Space Solutions will conduct in-space autonomous rendezvous, proximity operations and docking (RPOD), and Northrop Grumman will refuel a Space Force Tetra-6 satellite in GEO, scheduled in 2027. The successive Tetra demonstrations are part of a broader effort to develop in-space servicing, assembly and manufacturing (ISAM) technology. NASA and the DOD have spent more than $2 billion during the past decade developing ISAM capability, according to a July 2025 Government Accountability Office report. Other nations, including China, also are developing and demonstrating ISAM technologies.
Likewise, efforts are underway to develop refueling for deep space missions. SpaceX and Blue Origin are eyeing potential fuel depots on orbit to aid crewed flights to the moon or Mars. SpaceX conducted a fuel-transfer demonstration inside a Starship spacecraft during a 2024 flight. Blue Origin aims to create a fuel transport vehicle that would take on fuel near Earth before carrying astronauts to the moon, The Wall Street Journal reported in August 2025. Both deep space vehicles would use a combination of liquid methane and liquid oxygen. The supercold propellants are prone to boil off in space, making storage and fuel transfer more complicated than for satellites. Most satellites are fueled by hydrazine, a stable alternative that doesn’t require onboard cryogenic storage capacity.
Assessing the advantages
From a military viewpoint, on-orbit refueling presents significant strategic advantages, notably the ability to exercise dynamic maneuverability. In an era when space threats are multiplying, the need to reposition satellites, or “dynamic space operations,” is becoming more urgent. “We’ve done enough of the exercises. We’ve done enough of the training. … [We] see what dynamic maneuver would do for us if we had it,” Army Lt. Gen. Thomas L. James, deputy commander of USSPACECOM, said during a May 2025 webinar with the Mitchell Institute for Aerospace Studies. “We see the advantages. I mean, it’s clear that’s there.”
Maneuverability would offer resilience during conflict and expand the military’s space domain awareness — its ability to monitor satellites and debris. Similarly, surveillance and reconnaissance spacecraft would benefit because operators monitoring adversaries’ satellites wouldn’t need to curtail their missions over fuel concerns. Such issues are increasingly vital as military leaders contemplate the future of space defense. “We’re not in the acquisition or capability development business, but we are certainly into the requirements of understanding what our vision and view of orbital warfare is going to look like in the future, and what we have to have in place, and … that is absolutely based on things like dynamic space maneuver,” James said.
Another advantage involves orbital debris and the ability to steer clear of space junk. As space becomes more congested, operators have reported an uptick in unplanned maneuvers to avoid debris and other satellites. California-based space tracking company Slingshot Aerospace said analysis showed a 17% year-over-year spike in close approaches per satellite across low Earth orbit (LEO) in 2024.
On-orbit refueling also would ease this problem by extending satellites’ lifespans, resulting in fewer inactive satellites and less need for new launches. It might also aid in debris removal. Several companies are developing spacecraft to grab and reposition derelict satellites to graveyard orbits. Among them are Japan-based Astroscale and Switzerland’s ClearSpace. In a demonstration in December 2024, Astroscale’s ADRAS-J (Active Debris Removal by Astroscale-Japan) moved to within 15 meters of an abandoned rocket’s upper stage. ClearSpace is set to test debris-removal capabilities with a demonstration in 2026.
But such technologies, while promising, face questions about cost and practicality given the likelihood that such spacecraft would be limited to one or two captures per mission due to fuel constraints. On-orbit refueling could address this by expanding spacecrafts’ lifespans — and potentially speeding up the pace of objects removed from LEO. Aiden O’Leary, who has co-authored several papers about in-space refueling, told Apogee that active debris removal, coupled with on-orbit refueling, could turn the tide in space debris removal.
“Because of [refueling], you could then do all of these orbital maneuvers instantaneously and remove tens or hundreds of satellites or rocket bodies in the lifetime of that satellite before it becomes too old to function,” O’Leary said. O’Leary co-founded technology logistics and marketing company Modulate Media, where he serves as chief technology officer.
The push for satellite refueling, meanwhile, is contributing to a wave of innovation. Recent Space Force contracts with Northrop Grumman, Orion Space Solutions and Astroscale U.S. for on-orbit refueling are attracting broader interest across the defense sector. By funding experiments like Tetra-5 and Tetra-6, the Space Force is encouraging development of new technologies and ideas to shape in-space logistics.
Lauren Smith, Northrop Grumman’s program manager for in-space refueling, emphasized the importance of such demonstration contracts: This project “served as a pathfinder to help inform future enterprise refueling requirements and potential risk-reductions activities,” she said in a March 2025 SpaceNews report.
Northrop’s Tetra-6 project, also known as Elixir, would introduce several technologies, including a Passive Refueling Module (PRM), which serves as a refueling interface. For its 2027 demonstration, a Northrop satellite bus carrying a fuel depot known as GAS-T, short for Geosynchronous Auxiliary Support Tanker, will launch into GEO to dock with a PRM-equipped Tetra-6 satellite.
“Show me the military advantage, I mean in a fight. If I go to war with China, how does refueling help me beat them?” ~ Gen. Shawn Bratton, U.S. Space Force, vice chief of space operations
Astroscale’s Tetra-5 mission would demonstrate similar technologies, including the refueling transfer valve RAFTI (Rapidly Attachable Fluid Transfer Interface) created by Colorado-based startup Orbit Fab. For the Space Force demonstration, two small satellites equipped with RAFTI will be launched to just above GEO. Astroscale will launch a Refueler APS-R spacecraft to dock with and fuel one of the satellites. Then the APS-R will refuel itself from a spacecraft designed by Orbit Fab and maneuver to the second Space Force satellite to refuel it. Ron Lopez, president of Astroscale U.S., said the Tetra-5 demonstration will show that “in-space logistics does not have to be years away. … The Astroscale U.S. Refueler is proof that commercial space companies can develop and deliver new, operational capabilities on time and on budget.”
Melissa Sampson, vice president of business development at Orbit Fab, expressed similar confidence, saying the company successfully demonstrated RAFTI a few years ago during a mission to the International Space Station and has already secured contracts to install RAFTI ports on commercial satellites. The company aims to create in-space fuel depots to provide fuel to service vehicles or directly to satellites. Sampson said she’s optimistic refueling will play a pivotal role in removing space debris, including satellites nearing the end of their lifecycles. “Refueling means that they could be moved out of the way. It means they could go into a disposal orbit, or they could be brought back to Earth and enter the atmosphere as a disposal method,” she told Apogee. “So, it opens up a whole lot of opportunities and a whole lot of solutions because you would now have unlimited fuel and you’re not trying to say, ‘Oh, my gosh, I can only go another mile in space. How am I going to properly get my satellite out of the orbit so newer satellites can use that orbit?’”
The Space Force’s Space Systems Command has approved both the Orbit Fab RAFTI and the Northrop PRM refueling systems “as acceptable commercial solutions for refueling,” enabling their placement on satellites.
Some are skeptical
Despite these technological strides, Space Force leaders remain unconvinced the technology offers a definitive, cost-effective edge. “I don’t know that I see the clear military advantage of refueling,” then-Lt. Gen. Shawn Bratton, who at the time was the Space Force’s deputy chief of operations for strategy, plans, programs and requirements, said during a space industry conference in Albuquerque, New Mexico, in May 2025. Gen. Bratton is now vice chief of space operations. A key question remains, he said: Does refueling deliver more value than replacement? Unlike air-to-air refueling, which extends the operational range of aircraft, the case for satellites isn’t so obvious. “With spacecraft, the issue is life extension,” Bratton said. Many satellites, especially older military models, are retired due to hardware failures, not because they run out of fuel.
Another significant challenge is that most satellites on orbit were never designed to be refueled. Adapting the existing fleet for servicing would be difficult, if not impossible. Referring to what realistically can be serviced now, Bratton said, “With the fleet we’re flying today, the answer is not much.” That means the near-term benefits of refueling could be limited, and substantial advantages may not materialize until a new generation of service-ready satellites is launched — a process that could take a decade or more.
Bratton’s comments mirrored those of Space Force Gen. B. Chance Saltzman, chief of space operations, in testimony to Congress. Asked about the issue at a House appropriations hearing in April 2024, Saltzman cited the potential for a non-refueling strategy. “From a mission standpoint, we’re rapidly trying to shift from large satellites in geosynchronous orbit, whose lifespan requires them to have a lot of fuel, where refueling could be valuable, we’re shifting from that kind of architecture into a proliferated low Earth orbit with a set of constellations.
“We’re talking hundreds of satellites much smaller and more easy to replace. So, the idea is that you wouldn’t need to refuel them because you’re trying to replenish that proliferated constellation on a more frequent basis. So, three to five years on orbit, replace it with updated technology. It wouldn’t necessarily require the same level of servicing on orbit,” he told the House Appropriations Committee. “We’re trying to get the balance just right and make sure that all the dollars that we invest would be properly utilized.”
Still, the case for satellite refueling isn’t settled. Building, launching and sustaining a refueling architecture in space is expensive, and it’s not clear whether enough high-value satellites exist to justify the investment. At the same time, from a military operations standpoint, refueling presents key tactical advantages, namely dynamic space operations. Bratton summarized the dilemma this way: “GEO and LEO I think are very different,” he told the conference in Albuquerque. “At LEO, it’s really hard for me to wrap my head around. At GEO, for maneuverable spacecraft, all right, I’m there. So, now it’s, ‘Do I have enough of those [expensive satellites in GEO] that warrant building a fueling architecture and getting it up there?’ I don’t know today that I do. Now, will I 10 years from now? I think the jury’s still out. Dynamic space operations is a military advantage, and I don’t disagree with that. I’m just looking at the hardware that’s going to use refueling, and I’m not sure quite honestly if it’s worth the investment.”
Venture-backed companies are hoping the DOD eventually becomes “an anchor customer” to enable the further buildout of space-based logistics. But the Pentagon wants industry to lead the effort — and shoulder the risk. One concern is whether refueling infrastructure could become a liability. “Refueling has some disadvantages … because it’s a big fat target depending on how you establish your refueling systems,” Gen. James said in a May 2025 Air & Space Forces Magazine article. Concentrated refueling depots or rendezvous points could provide adversaries with attractive targets, potentially undermining the very resilience the system aims to create.
Alternative technologies, nuclear
Critics of on-orbit refueling also point to alternative strategies that might supplant refueling. One is to rapidly deploy new satellites as existing ones reach the end of their lifespan, a process that might be faster and cheaper than servicing. Also, advances in artificial intelligence, machine learning and propulsion technology could someday enable satellite operations that don’t require refueling architecture. As Bratton put it during the Albuquerque conference, “Show me the military advantage, I mean in a fight. If I go to war with China, how does refueling help me beat them? Then I’m super interested. But if you can’t show me that, then it’s a science project.”
Lt. Gen. Philip A. Garrant, head of Space Systems Command, gave a similarly direct assessment. Speaking with reporters during the Space Symposium, he said that given rapid advances in technology, “satellites may have modern propulsion systems where fuel isn’t the limited capacity; new novel types of batteries, new novel types of propulsion.” Under this scenario, he said, the need for refueling could diminish — with resources possibly better spent on developing new, more capable satellites.
“I look at it as a problem in two phases,” he said, as reported in Breaking Defense. “I think we have a near-term problem where we have legacy satellites that … have limited ability to refuel or be refueled. So, I think we have a case to make where we have to be able to add ability to these satellites, whether you latch on another satellite that provides the power, whether you have the means to refuel a satellite. Clearly, if we’re going to have an offensive or defensive capability, [a satellite] has to be able to maneuver to the target or maneuver to the high value asset that it’s defending.”
In the end, Garrant said, it might be cheaper for the Space Force to await newer types of satellites and in the meantime send up smaller, cheaper satellites with short lifespans that are relatively easy to replace. At any rate, the future of satellite refueling remains a waiting game. The technology holds the promise to revolutionize space operations with longer lifespans, operational maneuverability, reduced debris and potential long-term savings. Yet, obstacles remain — from legacy systems and the cost to replace non-serviceable spacecraft to the potential for fuel depots to become “big fat targets.”
Another possibility, alluded to by Garrant at the Space Symposium, is that other emerging technologies could be just down the road. One possible contender: nuclear fission. Fission has been studied for decades but has attracted more interest and research dollars in recent years. In late September 2023, the Air Force Research Laboratory (AFRL) awarded $60 million to three companies — Intuitive Machines, Lockheed Martin and Westinghouse Government Services — to develop technologies for nuclear-powered spacecraft. The project is part of an AFRL program called Joint Emergent Technology Supplying On-orbit Nuclear Power (JETSON). Its aim is to create small reactors to provide electricity on satellites. The contracts extend through the end of December 2025.
Lockheed Martin, which received the largest of the contracts at $33.7 million, was asked to “mature the technical design of the JETSON spacecraft systems and subsystems to a preliminary design review level of maturity,” according to a DOD award statement.
While it’s too early to determine whether nuclear-powered generators make better sense than on-orbit refueling or proliferated constellations — or even if they’re affordable — the technology could become a go-to option in the development of unique, maneuverable spacecraft. Jeff Schrader, vice president of strategy and business development at Lockheed Martin, said spacecraft powered by nuclear thermal propulsion or nuclear electric propulsion aren’t limited by fuel constraints when conducting dynamic operations. “This thing could actually potentially pick up and move a satellite to a different orbit that the original satellite was never meant to be in, and allow it to do multi-orbit missions,” he told DefenseScoop in April 2024.
Kate Watts, Lockheed Martin Space’s vice president of mission strategy and advanced capabilities for exploration, told the publication that nuclear propulsion offers significant advantages, in particular when it comes to energy density, which could usher in an era of space architecture and missions not limited by size, weight or power. A small candy-sized amount of uranium “is about the same energy density as 500 barrels of oil or 1.8 [NASA Space Launch System] upper stages,” Watts said, according to DefenseScoop. “It’s a ton of energy packed in a very small space, which is now allowing you to no longer be power-limited like we are today, and fuel-limited once we develop these systems.”
Looking ahead, the potential for nuclear power may come down to costs. In June 2025, the Defense Advanced Research Projects Agency (DARPA) ended its 5-year-old Demonstration Rocket for Agile Cislunar Operations project to develop a nuclear thermal engine for satellites because the research cost-to-benefit ratio no longer matched. “As the launch costs came down, the efficiency gain from nuclear thermal propulsion relative to the massive R&D costs necessary to achieve that technology started to look like less and less of a positive ROI [return on investment],” Rob McHenry, then DARPA deputy director, told the Mitchell Institute during a June webinar.
However, McHenry said another nuclear technology could prove cost-effective and potentially drive research focus in coming years. The technology behind nuclear thermal propulsion rockets (NTR) is much less expensive and poses significant benefits, he said. NTRs use small on-board nuclear reactors to generate electricity, eliminating the need for solar panels, and a DARPA study indicated that NTRs have up to five times the efficiency of chemical propellants.
“Analysis by NASA and others has shown that nuclear electric is probably a more optimal long-term solution,” McHenry told the Mitchell Institute. “I believe that that’s actually a more optimal solution for national security missions as well, because that power in the space domain [providing maneuverability] may be the critical enabler, as much as the propulsion efficiency.”