Milligravity platform enables asteroid impact studies on Earth

Several locations are suitable for conducting research on reduced gravity environments, including aboard the International Space Station and in satellites. But the best place to study granular dynamics under microgravity is on an asteroid, and the second-best place — according to Joeris et al. — is in their new milligravity control and asteroid environment simulation system.

The researchers’ machine relies on the existing drop tower at The Center of Applied Space Technology and Microgravity, in Bremen, Germany. Their primary innovation is the addition of a linear stage in the drop tower, which provides constant, precise, and controllable acceleration. This is the core of the platform, generating Coriolis-free milligravity.

They used their platform to study an asteroid-like environment comprised of a granular surface, with gravity on the order of millimeters per square seconds.

“Looking at images of asteroids, the exact mechanisms leading to their surface composition are hard to explain,” said author Kolja Joeris. “We are hoping to contribute to that with our machine.”

Specifically, the group studied how particles in such an environment settle after impact. Once gravity is reduced beyond a certain threshold, they found the coefficient of restitution — the elasticity of the collision, determining whether particles settle into areas of smaller particles — increases for target surfaces consisting of very small particles.

“At low gravity, the balance with forces like electrostatics and cohesion shift away from what we are used to on Earth,” said Joeris.

Understanding granular dynamics in an asteroid environment under reduced gravity can help inform instrumentation and touchdown procedures for future asteroid missions, like the Japan Aerospace Exploration Agency’s Hayabusa2 or a follow-up to NASA’s OSIRIS-REx.

Source: “Controlled partial gravity platform for milligravity in drop tower experiments,” by Kolja Joeris, Matthias Keulen, and Jonathan E. Kollmer, Review of Scientific Instruments (2025). The article can be accessed at https://doi.org/10.1063/5.0233405 .