The world's largest solid-propellant launch vehicle, Gravity-1, lifted off from the East China Sea on Wednesday, sending nine satellites and one test payload into orbit. The mission, the rocket's third flight, marked the first time China conducted a sea-based launch of a commercial rocket in the Yangtze River Delta region and demonstrated open-sea mobile launch capability.

Unlike its previous two launches just kilometers off the coast, this time the launch vessel sailed to a zone about 170 kilometers east of Shanghai.

"Open-sea launch means we face completely different conditions," said Xu Guoguang, chief designer of Gravity-1. "The sea is rough even without wind. We had to plan support for the entire journey in advance."

The rocket, with a takeoff weight of 405 tonnes, faced significant challenges from waves and winds. The team prepared three layers of protection: coordinating with weather satellites to forecast sea conditions along the entire route, equipping the vessel with real-time weather monitoring gear, and setting up sheltered ports along the way for emergency shelter.

Three advantages drive the sea-launch approach. Safety is primary – the rocket's trajectory and debris fall zone remain over the ocean, where population and assets are minimal.

Efficiency follows. Land-launched rockets must detour around cities and airspace, with each degree of deviation consuming energy and reducing payload capacity, while sea launches allow a direct trajectory to the optimal orbit.

The third is orbital flexibility. Different spacecraft require different orbits, and sea launches let the launch point be almost freely chosen based on mission requirements.

With a maximum payload of 6.5 tonnes to low Earth orbit (LEO), Gravity-1 is transitioning from testing to commercial operations. The next launch, in the third quarter, will take part in China's LEO internet constellation deployment. A larger liquid-propellant rocket, Gravity-2, is under development with a LEO capacity of 21.5 tonnes and a 500 km sun-synchronous orbit capacity of 15 tonnes, which is expected to be ready for its maiden flight by the fourth quarter.

"Sea launch of solid-propellant rockets paves the way for future launch of liquid rockets at sea," Xu said. "We are also considering other methods, such as launching from drilling platforms."