A robotic system developed by Caltech has successfully assembled part of a structure in space without astronauts for the first time, according to research funded by the Defense Advanced Research Projects Agency (DARPA).
The robot, part of DARPA's NOM4D program, uses an automated arm to retrieve structural tubes and connecting joints from storage dispensers and joins them into sections called bays that form a larger framework called a truss. "This is the first time that a structure has been autonomously constructed in space," says Sergio Pellegrino, the Joyce and Krent Kresa Professor of Aerospace and Civil Engineering at Caltech.
Pellegrino leads Caltech's Autonomous In-Space Tensioned Reflector Assembly (ASTRA) demonstration. The robotic system spent six months in orbit attempting to construct a reflector antenna measuring 1.4 meters across, made from composite fiber tubes, aluminum connectors, and Kapton, a polymer film. The team encountered technical difficulties and scheduling constraints that prevented completion of the entire antenna, but the robot successfully assembled an initial section, demonstrating the construction method can work in orbit.
The system launched on March 30, 2026, aboard SpaceX Transporter-16 and traveled on Momentus Inc.'s Vigoride 7 orbital vehicle. After reaching orbit, three Caltech team members—Charles Sommer, Alan Truong, and graduate student Tara Venkatadri—managed construction commands from Earth by transmitting instructions to the onboard computer while monitoring progress through photographs from orbit.
Assembling large structures directly in space could transform astronomy, communications, and space-based energy systems. Future telescopes could use enormous reflective surfaces to collect more light, and similar structures could support powerful radio antennas. The approach addresses a fundamental challenge: fitting large spacecraft components inside a rocket's fairing, the protective enclosure that surrounds payloads during launch.
DARPA established NOM4D in 2022 to investigate technologies for in-orbit manufacturing and assembly. Caltech's ASTRA is one of only two projects selected to advance to the program's third phase. The other, led by the University of Illinois Urbana-Champaign, investigates hardening carbon tubes in space using a module at the International Space Station.
Andrew Detor, DARPA program manager for NOM4D, stated that the program's objective is "to enable efficient, scalable construction of very large structures in space," meaning "hundreds of meters or kilometers in scale. Nothing approaching that scale can be achieved today."