Orbital Express milestones.

Boeing claimed to have achieved an industry first when its Orbital Express system autonomously transferred propellant fuel and a battery from one spacecraft to another. During the fuel transfer demonstration, the Boeing Autonomous Space Transport Robotic Operations (ASTRO) servicing spacecraft transferred hydrazine propellant with Ball Aerospace's NextSat client spacecraft. The ASTRO vehicle also used a robotic arm to transfer a battery to NextSat. It marked the first time that a spacecraft autonomously transferred hardware to another spacecraft using a robotic arm.

The tests were the first in a series of planned demonstrations during a three-month mission to validate the system's functionality. The technologies developed by the DARPA-led programme are intended to support a broad range of future US national security, civil, and commercial space activities.

A few days later, the two Orbital Express spacecraft, which had been launched in a mated configuration, successfully separated and re-mated for the first time. The spacecraft were separated with use of the ASTRO's robotic arm, and the launch ring between them was safely ejected.

The system subsequently performed a fully autonomous free-flight rendezvous and capture operation. Using its onboard cameras and advanced video guidance system, the ASTRO spacecraft separated from the NextSat spacecraft, backed away to a distance of 10m, maintained proximity flight with NextSat for a full orbit, and then approached and captured NextSat with its docking mechanism.