Space collision: When does a spacecraft break apart?

Understanding breakup in orbit through simulations and experiments.

April, 2026. Earth’s low-Earth orbit is being filled with satellites, spent rocket parts, and space debris. Fragments just a few centimeters in size can shatter satellites due to high orbital velocities. If a fragment strikes a satellite, it breaks into countless new fragments—and each one threatens other spacecraft in orbit.

Fraunhofer EMI is investigating how satellites break into debris during collisions. To do this, the researchers combine experiments with numerical simulations.

Using a two-stage light gas accelerator, scientists accelerate small objects to speeds of up to eight kilometers per second, thereby realistically simulating collisions. In one recent HVI (hypervelocity impact) +experiment, a four-centimeter fragment struck a shoebox-sized satellite—shatering it into over 100 000 fragments.

Numerical simulations complement the experiments and allow for the analysis of different types of satellites. In doing so, the researchers model the fragmentation of the solid satellite structure into a debris cloud caused by the collision. A discrete element method (DEM) is used to simulate the satellite’s disintegration: millions of small particles are connected by springs to represent materials such as aluminum or carbon-fiber-reinforced plastic (CFRP). This forms the basis for the realistic simulation of the physical processes that describe the transition from the satellite structure to a debris cloud. Using graphics processing units (GPUs) or parallelized CPU clusters, even large satellites can be simulated down to the submillimeter range.

In the long term, the research team aims to translate its expertise into simplified models for describing satellite breakup. These models will help assess risks in orbit and make near-Earth orbit safer.

The work was conducted as part of a research project by the German Space Agency at the DLR.