For the first time, a robot has automatically assembled part of a structure in space, without the intervention of astronauts.
Usually, satellites are built on Earth before being launched. Their components must fit inside the rocket, even if that means folding them up and deploying them once in orbit. This constraint limits the size of some equipment. Researchers at the California Institute of Technology, or Caltech, have just tested another method: sending separate parts and assembling them automatically in orbit.
Artist's view of a robot assembling a large lattice structure in space as part of the NOM4D program.
Credit: Caltech / Momentus.
Their machine is called ASTRA. It carries lightweight tubes, connecting elements and a thin reflective surface. A mechanical arm picks up the parts, places them in the correct position and then connects them. The whole assembly gradually forms a framework designed to support an antenna.
The experiment involved a 1.4-meter-diameter model, only part of which was assembled in orbit. Two sections had been prepared before launch. The robot built the third, thereby demonstrating one step of the process.
The device left Earth on March 30, 2026, aboard a SpaceX mission. It then operated on a space platform operated by Momentus. From the ground, engineers sent commands and checked the results using photographs taken in orbit. Construction followed a sequence of automatic movements, but the team sometimes had to intervene to resolve problems.
Photograph taken in orbit by a camera from the ASTRA experiment, showing the assembly mechanism and the reflective elements of the structure, with Earth in the background.
Credit: Caltech / Momentus.
These difficulties slowed the experiment down. The engineers had only short daily windows to communicate with the device. When an incident occurred, they reproduced the problem on an identical unit kept in the laboratory. They could then try a fix before sending new instructions to the space robot.
Why build in this way? An antenna or a telescope mirror could one day greatly exceed the dimensions permitted by a rocket. Rather than launching a huge folded object, it would be possible to transport smaller components. The robot would then assemble them where the equipment needs to operate.
The ASTRA mission is scheduled to end in December 2026. Another project in the same U.S. program will also test, aboard the International Space Station, the manufacture of durable materials directly in space. This experiment will address another question: how can certain parts be produced on-site instead of being transported entirely from Earth?