A robot designed and built at Caltech has done something no machine has done before: it built a structure in space, entirely on its own.
The demonstration is called ASTRA — the Autonomous In-Space Tensioned Reflector Assembly — and it is the work of a small team in Pasadena led by Sergio Pellegrino, Caltech’s Joyce and Kent Kresa Professor of Aerospace and Civil Engineering, who is also a senior research scientist at the Jet Propulsion Laboratory. After six months in orbit, the team confirmed this week that it assembled a section of a truss in low Earth orbit — a first.
“This is the first time that a structure has been autonomously constructed in space,” Pellegrino said.
Space Legos, built by a robot
ASTRA works a bit like a high-tech K’Nex set, as DARPA puts it. The cubic-meter payload carries an armlike manipulator and dispensers stocked with composite fiber tubes and aluminum joints. The manipulator picks up one piece at a time and snaps it into place, building identical sections — called bays — of a ring-shaped truss.
The structure is the frame of a reflector antenna 1.4 meters (4.6 feet) across. ASTRA launched with two bays already built; once in orbit, it deployed those two, then autonomously assembled a third bay — the section that proves the concept works. The finished antenna would need 11 bays; the team built only the initial section, but the demonstration showed the method is feasible and scalable. ASTRA’s mission winds down in December.
A launch from Vandenberg, and a twin back in Pasadena
ASTRA reached orbit early on March 30, 2026, launching from Vandenberg Space Force Base aboard Momentus Inc.’s Vigoride 7 vehicle, itself carried by a SpaceX Transporter-16 mission.
Operating it was not straightforward: there are only about seven or eight 15-minute windows each day when the ground team can reach the spacecraft. Commands were sent by Charles Sommer, a former Caltech systems engineer; Alan Truong, a Caltech research engineer; and graduate student Tara Venkatadri — and checked against photos from one of the payload’s 11 cameras.
When something went wrong, the team reproduced the problem on ASTRA’s twin — a flight spare in Pellegrino’s Caltech lab — worked out a fix, and relayed it to the spacecraft.
Why building in orbit matters
Today, the size of anything we put in space is limited by the rocket fairing that carries it. Structures are folded up and unfurled in orbit, or pieced together by hand over several launches. ASTRA points to a third option: build them where they will be used.
That matters because the structures scientists want next are far bigger than any fairing. ASTRA is part of DARPA’s NOM4D program — Novel Orbital and Moon Manufacturing, Materials, and Mass-efficient Design — launched in 2022 to explore manufacturing in orbit. Caltech’s is one of only two projects to reach the program’s third phase, small-scale orbital demonstrations. DARPA’s program manager, Andrew Detor, put the ambition plainly: “very large” means hundreds of meters or kilometers in scale, and “nothing approaching that scale can be achieved today.”
The payoff would be enormous mirrors for space telescopes, giant radio antennas, and very large solar arrays — including for space solar power, a field Pellegrino also works in as co-director of Caltech’s Space Solar Power Project. ASTRA’s reflective film was co-invented by the Caltech team and University of Pennsylvania collaborators led by professor Igor Bargatin; it needs less prestress than the usual knitted metallic mesh, allowing much lighter structures.
A Pasadena-built first
The whole demonstration — concept, design, build, and a less-than-12-month sprint to deliver the payload to Momentus — happened in a Caltech lab near JPL, which Caltech manages for NASA. It is the same line of work behind Pellegrino’s earlier proposal for a 100-meter space telescope assembled in orbit by robots: a reminder that some of the most consequential space hardware of the next decades may be put together not by astronauts, but by machines built in Pasadena.
Sources: Caltech (via Phys.org), “Robot successfully builds space structure in first autonomous construction demo,” November 6, 2026; DARPA, Novel Orbital and Moon Manufacturing, Materials, and Mass-efficient Design (NOM4D) program page; Caltech, “NOM4D – ASTRA Assembly Demonstration” (video).
