A robot developed by the California Institute of Technology has autonomously assembled part of a structure in orbit for the first time, demonstrating a technology that could eventually enable the construction of gigantic telescopes, antennas and solar arrays.
The robotic system, part of Caltech's Autonomous In-Space Tensioned Reflector Assembly (ASTRA) project, spent six months in low Earth orbit attempting to build a 1.4-meter-wide reflector antenna from composite tubes, aluminium connectors, and Kapton reflective film.
"This is the first time that a structure has been autonomously constructed in space," said Sergio Pellegrino, the Joyce and Krent Kresa Professor of Aerospace and Civil Engineering at Caltech and leader of the ASTRA demonstration.
The experiment is part of DARPA's Novel Orbital and Moon Manufacturing, Materials, and Mass-efficient Design (NOM4D) program, established in 2022 to investigate technologies for manufacturing and assembling large structures in orbit rather than launching them prebuilt. DARPA compares the assembly process to building with sophisticated versions of K'Nex or Tinkertoy construction toys.
"NOM4D's objective is to enable efficient, scalable construction of very large structures in space," said Andrew Detor, DARPA program manager for NOM4D, in a written statement. "By 'very large,' I mean hundreds of meters or kilometers in scale. Nothing approaching that scale can be achieved today."
ASTRA launched on March 30, 2026, aboard a SpaceX Transporter-16 mission from Vandenberg Space Force Base, riding on Momentus Inc.'s Vigoride 7 orbital vehicle. The payload occupied about one cubic metre and contained the assembly machinery, a robotic arm, motorised part dispensers, and the two pre-assembled truss bays.
In orbit, the robot extended the two pre-assembled bays and built a third using its automated arm to retrieve structural tubes and connecting joints from storage dispensers and join them into repeating sections. Three team members on Earth, Charles Sommer, Alan Truong, and graduate student Tara Venkatadri, monitored progress via photographs and sent instructions during limited communication windows of about 15 minutes each, roughly seven or eight times daily.
To diagnose problems, engineers used a flight-spare ASTRA system kept at Pellegrino's Caltech laboratory. "Every time we confirm there is an issue in space, we come to the laboratory and try to mimic the problem on the ground," Sommer said.
The team encountered technical difficulties and scheduling constraints that prevented completion of the full antenna, but researchers believe they collected enough evidence to establish the technical feasibility of the approach. “That's basically the reason you do proof-of-concept testing. There are a lot of differences in the space environment compared to down on Earth,” said Jaden Suh, a former Caltech postdoctoral scholar now at the University of Texas at Austin. “There are always lots of little surprises.”
Future applications could include giant space telescopes, advanced radio antennas, and enormous solar arrays for space-based solar power, an idea being explored through Caltech's Space Solar Power Project. Pellegrino said: "Once you get to the size limit where structures cannot be prebuilt on the ground and unfolded, you have to think about how to build them in space."
The mission is expected to conclude in December.
Analysis
Why This Matters
- The demonstration proves that autonomous robotic construction in orbit is technically feasible, potentially freeing future space infrastructure from the size limits of rocket fairings.
- Success could enable much larger telescopes, antennas, and solar arrays than can be launched pre-assembled, transforming astronomy, communications, and space-based energy systems.
- The lessons learned from in-orbit troubleshooting (limited communication windows, unexpected environmental effects) will inform the design of more reliable future autonomous construction systems.
Background
Robotic space construction is not new, Canadarm2 helped build the International Space Station, and 3D printers have operated aboard the ISS. But those systems either manoeuvred pre-built components through astronaut assistance or manufactured small parts inside the station. ASTRA is the first to autonomously assemble a load-bearing structure from individual components in open orbit, without human intervention in the assembly itself. DARPA's NOM4D program aims to scale this concept to structures hundreds of metres or kilometres in size, potentially shipping raw materials from Earth for in-orbit manufacturing.
Key Perspectives
Sergio Pellegrino (Caltech): Called the demonstration the first autonomous construction of a structure in space, saying the work could be useful for astronomy, communications, and building very large solar arrays for space solar power.
Andrew Detor (DARPA): Described the demonstration as a significant step toward structures kilometers in scale, noting that "nothing approaching that scale can be achieved today."
Jaden Suh (former Caltech postdoc, now UT Austin): Emphasised that proof-of-concept testing reveals unexpected differences from the lab environment, calling the challenges "lots of little surprises."
Charles Sommer (former Caltech systems engineer): Described the team's method of replicating in-orbit problems on a ground-based duplicate to develop solutions.
What to Watch
- Whether the ASTRA mission completes additional bay assembly before its planned conclusion in December.
- DARPA's next phase of NOM4D: selection of follow-on orbital demonstrations or scaling projects.
- Potential application of the technique to the Space Solar Power Project, which aims to wirelessly transmit solar energy from orbit to Earth.
Checked
12 claims in this story checked against 1 source: 12 supported.
Show each claim
- SupportedA Caltech robot autonomously assembled part of a structure in space for the first time.Latest Science News -- ScienceDaily: “For the first time, a robot has successfully assembled part of a structure in space without astronauts”
- SupportedThe DARPA-funded ASTRA demonstration built a truss bay in orbit as a step toward potential kilometer-scale space construction.Latest Science News -- ScienceDaily: “The robot successfully assembled an initial section, providing evidence that this construction method can work in orbit.”
- SupportedPellegrino said, “This is the first time that a structure has been autonomously constructed in space.”Latest Science News -- ScienceDaily: ““This is the first time that a structure has been autonomously constructed in space,” says Sergio Pellegrino”
- SupportedDetor said NOM4D aims to enable efficient, scalable construction of very large structures in space, on a scale of hundreds of meters or kilometers.Latest Science News -- ScienceDaily: ““NOM4D's objective is to enable efficient, scalable construction of very large structures in space,” said Andrew Detor, DARPA program manager for NOM4D, in a written statement. “By 'very large,' I mean hundreds of meters or kilometers in scale.”
- SupportedASTRA spent six months in low Earth orbit attempting to construct a 1.4-meter-wide reflector antenna.Latest Science News -- ScienceDaily: “The robotic system has spent six months in orbit attempting to construct a reflector antenna measuring 1.4 meters across.”
- SupportedASTRA launched on March 30, 2026, aboard SpaceX Transporter-16 from Vandenberg, riding on Momentus's Vigoride 7.Latest Science News -- ScienceDaily: “ASTRA began its journey on March 30, 2026, when a SpaceX Transporter-16 mission launched from Vandenberg Space Force Base in California early that morning. The robot traveled aboard Momentus Inc.'s Vigoride 7 orbital vehicle”
- SupportedThe payload occupied about one cubic metre and included assembly machinery, a robotic arm, dispensers and two pre-assembled truss bays.Latest Science News -- ScienceDaily: “ASTRA occupied approximately one cubic meter of space, a compact package containing both the assembly machinery and the materials required for construction. Inside were two previously assembled truss bays”
- SupportedThe robot extended the two pre-assembled bays and constructed a third.Latest Science News -- ScienceDaily: “The robot then extended the two previously assembled truss bays out of the machine and proceeded to construct a third bay using the onboard assembly system.”
- SupportedSommer said, “Every time we confirm there is an issue in space, we come to the laboratory and try to mimic the problem on the ground.”Latest Science News -- ScienceDaily: ““Every time we confirm there is an issue in space, we come to the laboratory and try to mimic the problem on the ground,” Sommer says.”
- SupportedSuh said, “That's basically the reason you do proof-of-concept testing. There are a lot of differences in the space environment compared to down on Earth,” and “There are always lots of little surprises.”Latest Science News -- ScienceDaily: ““That's basically the reason you do proof-of-concept testing. There are a lot of differences in the space environment compared to down on Earth,” Suh explains. “There are always lots of little surprises.””
- SupportedTechnical difficulties and scheduling constraints prevented completion of the full antenna, but the team believes it gathered enough evidence to establish technical feasibility.Latest Science News -- ScienceDaily: “The team encountered technical difficulties and scheduling constraints that prevented it from finishing the entire antenna. Nevertheless, the robot successfully assembled an initial section, providing evidence that this construction method can work in orbit.”
- SupportedPellegrino said, “Once you get to the size limit where structures cannot be prebuilt on the ground and unfolded, you have to think about how to build them in space.”Latest Science News -- ScienceDaily: ““Once you get to the size limit where structures cannot be prebuilt on the ground and unfolded, you have to think about how to build them in space,” Pellegrino says.”