For the first time, a robot has autonomously assembled part of a structure in space.

Caltech's Autonomous In-Space Tensioned Reflector Assembly (ASTRA) system used a robotic arm to retrieve structural tubes and joints from onboard dispensers and connect them into a third truss bay, joining two preassembled sections deployed after launch.

The payload, about one cubic meter in size, launched March 30, 2026, on SpaceX's Transporter-16 mission from Vandenberg Space Force Base aboard Momentus Inc.'s Vigoride 7 orbital vehicle.

Principal investigator Sergio Pellegrino called it the first time a structure has been autonomously constructed in space.

Every large spacecraft today is constrained by the rocket fairing, the protective enclosure that must hold the entire payload at launch.

Engineers traditionally fold structures into compact packages that unfold in orbit, or launch separate pieces for astronauts to assemble — both approaches cap size and complexity. Robotic construction offers a third path: ship raw materials to orbit and build there.

DARPA's NOM4D program manager Andrew Detor said the goal is efficient, scalable construction of structures at hundreds of meters or kilometers in scale, which nothing approaching can be achieved today. The technique could enable enormous telescopes, antennas, and solar power stations.

The demonstration was not flawless. Technical difficulties and scheduling constraints prevented the robot from finishing its planned 1.4-meter reflector antenna, designed as 11 connected bays topped with a reflective Kapton film co-invented by Caltech and University of Pennsylvania researchers.

According to Science Daily, the team managed operations from Earth through only about seven or eight communication windows of roughly 15 minutes each day, diagnosing problems by recreating them on a laboratory flight spare before sending revised instructions.

Interesting Engineering reports the mission ends in December, with the incomplete antenna yielding lessons for future systems.

ASTRA is one of only two NOM4D projects selected for the program's third orbital-demonstration phase. The other, led by the University of Illinois Urbana-Champaign, will test hardening carbon tubes in space using a module attached to the International Space Station.

The long-term stakes span astronomy, communications, and energy: large orbital reflectors could collect more light for telescopes, support powerful radio antennas, and underpin space-based solar power — Pellegrino also co-directs Caltech's Space Solar Power Project.

The small team spent under 12 months building the flight hardware, and former postdoctoral scholar Jaden Suh said seeing his childhood dream of sending space structures to orbit was incredible.