Int-Ball2

The Next Generation Takes Flight: JAXA's Int-Ball2 Revolutionizes Robotics on the ISS

The Japan Aerospace Exploration Agency (JAXA) has once again made its mark in the realm of space robotics with a monumental success: the in-orbit demonstration of the JEM Internal Ball Camera 2 (Int-Ball2). Inside the Japanese Experiment Module "Kibo" of the International Space Station (ISS), this spherical drone has not only proven its ability to fly autonomously but has also mastered the art of self-sufficiency with a fully automated docking

and charging system. This is far more than an upgraded camera—it is a critical stepping stone toward a future of truly autonomous space robots.

The Leap from Int-Ball 1.0 to Int-Ball 2.0

To truly appreciate Int-Ball2's achievement, one must look back at its trailblazing predecessor. Launched in 2017, the first Int-Ball was a groundbreaking proof-of-concept. It successfully demonstrated basic attitude and movement control in zero-gravity, proving that a free-flying robot could navigate the complex interior of a space station. However, for all its success, the first-generation Int-Ball had a significant limitation: every time it needed to recharge, an astronaut had to manually plug and unplug its electrical connector. This meant that while the robot handled the photography, it still required crew intervention for its most basic operational need.

Int-Ball2 has completely eliminated this bottleneck. The successful demonstration of automatic docking, a feature not present in the first unit, means the robot can now operate on a continuous cycle of flying, photographing, and recharging without any human assistance. This single technological advancement has profoundly improved the mission value of the project, truly achieving its goal of "zero burden on the crew for photography work."

The Engineering Behind the Magic: A Deep Dive

Creating a self-sufficient robotic camera capable of navigating a zero-gravity environment required solutions across multiple engineering disciplines. The breakthroughs achieved in Int-Ball2's design are a testament to meticulous research and development.

1. Flight Control: Mastering Six Degrees of Freedom in Zero-G

Autonomous flight in space is a fundamentally different challenge than flying a drone on Earth. A terrestrial drone battles gravity and air resistance. Int-Ball2, operating in the microgravity of the ISS, faces a different set of obstacles: it has no "down" to reference, and it must precisely control its motion in all directions.

The propulsion system is a masterclass in zero-G control. Utilizing a configuration of eight propellers, the robot achieves full control over six degrees of freedom (6-DOF): three for its position (x, y, z) and three for its orientation (roll, pitch, yaw). By skillfully adjusting the rotation speed of each propeller, the system can generate thrust vectors in any direction, allowing it to move, rotate, and, crucially, halt its motion.

A key challenge was maintaining stability. While gravity is absent, air currents from the ISS's life support systems are not. Int-Ball2's control system is designed to counteract these subtle but disruptive forces, ensuring the robot remains perfectly stable while pointing its camera in the desired direction. As detailed in research presented at the IAC 2020 conference (D. Hirano et al.), this sophisticated control system enables stable and precise flight within the tight confines of Kibo.

2. The Docking Mechanism: A Simple Solution to a Complex Problem

Automating the docking process for a free-flying sphere is no easy feat. The docking mechanism's design, which is patent pending (Patent No. 7175004), is an elegant solution to this challenge. It cleverly leverages the spherical shape of Int-Ball2 with a specially designed guide. This guide is a simple, yet highly effective, mechanism that ensures secure docking even if the robot's approach is slightly off-kilter.

The heart of the mechanism lies in its use of magnets. The guide moves back and forth, using the repulsive force of magnets to create both an alignment and a buffering system. This single, ingenious mechanism fulfills all the necessary functions: it gently pulls the vehicle into place, holds it securely for charging and communication, and then moves out of the way to allow for a clean release. This design, which was presented at the 2020 IEEE International Conference on Robotics and Automation (ICRA) by K. Watanabe, minimizes its footprint inside Kibo while maximizing functionality and reliability.

3. Verification Technology: From Ground Tests to Hybrid Simulation

Before Int-Ball2 ever left Earth, its systems were put through a battery of rigorous tests. JAXA's verification process was a blend of established techniques and new innovations.

• 2D Surface Plate Tests: Using an air levitation device, the robot's horizontal movements and docking sequences were tested on a two-dimensional surface, simulating a low-friction, weightless environment on a flat plane.

• Hybrid Simulation: To validate flight control in three-dimensional space, a new hybrid simulation test technology was developed. This sophisticated "Hardware-in-the-Loop" (HIL) system combined the real robot's flight computer and sensors with a virtual, simulated environment. This allowed engineers to test navigation, guidance, and control systems under realistic zero-G conditions without the need for a full-scale, expensive facility.

• Visual Marker Measurement: To ensure navigation accuracy, JAXA developed and applied a high-precision measurement system using planar visual markers. These markers, similar to advanced QR codes, allowed a camera to measure the robot's exact relative position and orientation with high fidelity, a crucial step for mission-critical operations.

Looking to the Future: Beyond Int-Ball2

Int-Ball2 is more than just a successful project—it is a foundation for JAXA's broader research into environmentally adaptive space robotics. The technologies demonstrated in this mission are directly applicable to a wide range of future endeavors:

• Future Manned Space Bases: The ability to transport cargo and perform routine tasks without crew intervention is vital for future manned outposts like the lunar Gateway. Int-Ball2's cargo handling technology is a direct precursor to this.

• Space Robotics for Exploration: The autonomous navigation and control systems will be instrumental in developing robots for future exploration missions on the Moon, Mars, and beyond.

• Spacecraft Software Environment: The successful demonstration of the "ROS 2 and cFS Bridge (RACS2)" software on Int-Ball2 highlights JAXA's commitment to creating open-source-compatible software environments. This approach encourages participation from private robotics researchers and accelerates the development of advanced space robotics.

JAXA's Int-Ball2 represents a major leap forward in space technology, proving that a fully autonomous, zero-burden robotic assistant is not a distant dream, but a current reality. With the initial on-orbit checkout nearing completion, the robot is set to begin regular operations next year, marking a new chapter in the partnership between humans and robots in the final frontier. This demonstration is a clear signal that the future of space exploration will be built on the shoulders of these small, spherical pioneers.