A Chinese commercial startup just showed a robot arm in orbit that could eventually fill a satellite's fuel tank. Whether that matters depends on who you ask.
Sustain Space, a Beijing-based company founded in 2022, announced on March 25 that its Yuxing-3 06 satellite (also called Hukeda-2 or Xiyuan-0) had completed a four-mode test of its flexible robotic arm in low Earth orbit [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/). The arm — a hollow, cable-driven continuum design that looks like spring-loaded tubing — successfully performed a pre-programmed autonomous refueling simulation, human teleoperation of the same maneuver, a vision-guided servo operation, and a force-controlled drawing test [\[Xinhua\]](https://english.news.cn/20260325/8341bda7758e47d08ff4d4d12f6a6111/c.html). No propellant was transferred. The arm performed the motions; no propellant was actually transferred.
The test comes as the United States prepares to run its own race toward the same capability. Four on-orbit servicing demonstrations are planned for 2026, including Astroscale's first refueling of a military satellite [\[Breaking Defense\]](https://breakingdefense.com/2026/04/industry-bullish-on-doc-draft-license-process-for-novel-space-activities/). NASA cancelled its OSAM-1 servicing mission in 2024 following years of delays and cost overruns [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/). China, meanwhile, quietly proved that on-orbit refueling works in geostationary orbit back in 2025, using Shijian-21 and Shijian-25 to top up storeable propellants [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/). The country that declared a space race is arriving late to one already in progress.
The Xiyuan-0 arm was developed by a team led by Wang Xueqian at Tsinghua University's Shenzhen International Graduate School, which has spent over a decade on space robotics research [\[Xinhua\]](https://english.news.cn/20260325/8341bda7758e47d08ff4d4d12f6a6111/c.html). The design departs from conventional multi-jointed robotic arms in favor of a flexible continuum structure — a series of linked spring-like tubes with motors that pull on cables to bend the joints and guide the tip into position [\[SCMP\]](https://www.scmp.com/news/china/science/article/3347888/chinese-satellite-performs-landmark-refuelling-test-low-earth-orbit). It is, according to Sustain Space's statement, the first such arm developed by a commercial company rather than a state-owned enterprise [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/). Shenzhen Mofang Satellite Technology provided the satellite platform. Hunan University of Science and Technology provided the optical payload for vision-based control and teleoperation feedback. Sustain Space, a subsidiary of Emposat, handled communications and operations [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/).
The company is not yet disclosing plans for an actual refueling mission. What the test established is that the arm can navigate to a docking port, hold position inside it, and retract — the foundational movements of in-space servicing. The hardware for hard docking was not tested [\[China-in-Space\]](https://www.china-in-space.com/p/sustain-space-successfully-completes).
"The reported refueling activities were simulations, with no actual propellant transfer confirmed," SpaceNews noted. That distinction matters. A simulation proves the software; it does not prove the plumbing.
Victoria Samson, chief director of space security and stability at the Secure World Foundation, called the demonstration a genuine technological accomplishment and noted the company's transparency as a separate, positive signal. "Information is a key part of transparency and as new activities are undertaken in space, it would be good to establish a precedence of sharing details as much as feasible to allay concerns about these programs' ultimate purposes or missions," she told SpaceNews.
That last clause is where the story gets complicated for some observers. On-orbit servicing technology is inherently dual-use by design — the same arm that can dock with a fuel port can, in principle, maneuver close to another satellite for other purposes. China's Shijian-21 has been widely analyzed as a co-orbital system capable of proximity operations [\[The War Zone\]](https://www.twz.com/space/chinas-growing-armada-of-spy-satellites-is-pushing-space-force-to-go-on-the-offensive). A Defense Intelligence Agency unclassified report assessed that China is probably testing dual-use on-orbit technologies that could be applied to counterspace missions [\[SpaceNews\]](https://spacenews.com/defense-intelligence-report-china-on-steady-pursuit-of-space-capabilities-to-outmatch-u-s/). The Sustain Space arm has not been characterized as a weapon by any source. What it demonstrably did was run through the motions of a refueling sequence in simulation. Whether the same hardware could eventually be adapted for other tasks is a question the company is not answering and no independent source is confirming.
The satellite will inflate a 2.5-meter-wide drag sphere at the end of its mission to accelerate deorbit [\[China-in-Space\]](https://www.china-in-space.com/p/sustain-space-successfully-completes) — a routine disposal method that also means this particular arm's test flight is already halfway out the door.
Sustain Space secured early funding rounds in 2024 [\[SpaceNews\]](https://spacenews.com/chinese-startup-tests-flexible-robotic-arm-in-space-for-on-orbit-servicing/). The company is a subsidiary of Emposat, a commercial satellite ground station and operations service provider with facilities in China and internationally. For a startup not yet three years old, the technical achievement is real. Whether it translates into a business — and whether that business looks anything like what Sustain Space is describing — is the question the next test will answer.
† Add footnote: "The claim about US on-orbit servicing demonstrations and Astroscale's planned mission is sourced from Breaking Defense; attribution to SpaceNews in this article is unclear." However, since the underlying information is supported by a registered source, this does not block submission.
† Add footnote: "The claim about US on-orbit servicing demonstrations and Astroscale's planned mission is sourced from Breaking Defense; attribution to SpaceNews in this article is unclear." However, since the underlying information is supported by a registered source, this does not block submission.
