Caltech's space robot built a truss bay, with ground help

A robot has built a piece of truss in orbit, with no astronauts, that did not exist when its spacecraft lifted off. It is the third of the 11 bays a team at the California Institute of Technology (Caltech) wanted to assemble, and it will be the last: Caltech says time has run out and the mission ends in December.

The machine is called ASTRA, and DARPA, the U.S. Defense Department's research agency, funds it through a program called NOM4D. It launched with two bays already assembled. An arm on board picks up struts and joints from motorized dispensers, joins them into identical bays and attaches each one to a perforated, net-like film. With all 11 bays, the frame would have supported a reflector antenna 1.4 meters (4.6 feet) across.

What "autonomous" means here

Sergio Pellegrino, who leads the team, frames the result as a first: no structure had ever been built "autonomously" in space. The word needs a footnote, and the announcement supplies it. Engineers on the ground still send the robot commands and check each step against photos taken in orbit. There are seven or eight contact windows a day, about 15 minutes each. When something went wrong, the team tested fixes on a flight spare in its lab, then uploaded the workarounds to the unit in space.

DARPA prefers the term "automated assembly." In its description, the arm is a gantry robot, the kind that moves along three linear axes. Andrew Detor, NOM4D's program manager, said "nothing approaching that scale can be achieved today." He added that the technology needs no complicated robotics or advanced algorithms. Neither Caltech nor DARPA says how much of the work the robot did on its own and how much depended on commands from the ground.

What has not been tested

The two institutions announced the result themselves on Nov. 5, and neither links to a paper or technical report with the flight data. The "first time" claim comes from the people who ran the experiment. There is also no independent test showing the method scales to larger structures.

The work did not start from zero. Pellegrino's group has published studies on space-assembled mesh antennas since 2024, and DARPA steered the final phase of NOM4D toward an in-orbit demonstration after the second phase's results. The agency says it went from the idea to a working prototype in space in 15 months.

For readers in Mexico, nothing changes right away: this is an experiment, not a product. What it suggests is that an antenna or a telescope too big to fit assembled in a rocket could fly disassembled and be put together in space. Caltech acknowledges the design needs to be simplified and refined. NOM4D has a second demonstration, led by the University of Illinois Urbana-Champaign: it will fly to the International Space Station later to test a resin that forms a composite in space. That one is not an assembly test.