AthenaZero robot throws baseball at 113 km/h, lands Science Robotics cover

lukas_m_ziegler · x · 2026-09-20

The AthenaZero humanoid from raiinstitute is on this month's Science Robotics cover after throwing a baseball at 113 km/h.

The key is its hardware design:

Effective mass: only 3.97 kg at the wrist, versus 29.21 kg for a Franka and 34.72 kg for a UR5e measured the same way — nearly an order of magnitude lower, close to a human arm.
How: conventional industrial arms use gear ratios of 80:1 or higher, and gearboxes multiply reflected inertia by the square of the ratio. AthenaZero uses quasi-direct drive at roughly 5:1 on most joints and remotises transmissions so heavy components sit proximal, near the torso.
Specs: one-DoF torso, two 7-DoF arms, two 6-DoF underactuated hands — 22 actuators across 27 joints; 1.6 m tall, 1.8 m wingspan, 3+ kg payload.

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