DARPA-backed ASTRA robot builds structure in orbit without humans

First autonomous assembly in orbit

Caltech researchers have demonstrated a robotic system that assembled a truss section in low Earth orbit without human help. Called ASTRA (Autonomous In-Space Tensioned Reflector Assembly), the system was developed in the third phase of DARPA's NOM4D program.

It combines a robotic arm, motorized component dispensers, an assembly plate and an onboard computer in a payload of roughly 1 cubic meter. The payload launched on March 30, 2026, from Vandenberg Space Force Base aboard Momentus's Vigoride 7, one of 10 payloads on SpaceX's Transporter-16 mission.

How it works

ASTRA reached orbit with two preassembled truss bays. On ground command, it released the launch restraints, deployed the existing bays and used the robotic arm to build a third one. The arm picks composite fiber struts and aluminum joints from dispensers, positions them on the assembly plate and connects them; a reflective surface made of perforated Kapton film is then attached.

The target is a 1.4-meter-diameter reflector antenna. The demonstration did not complete the full antenna, but assembling the third bay established the feasibility of the approach. The planned configuration consists of 11 bays.

Lightweight material, limited contact

The perforated film, co-developed with the University of Pennsylvania, requires less prestress than the knitted metallic mesh used in conventional deployable reflectors, which could enable lighter structures.

Operating in orbit brought problems not seen in lab tests. With only about seven or eight communication windows of roughly 15 minutes a day, the team tested fixes on a flight spare at Caltech before sending revised commands to the spacecraft.