BEIJING, July 10 — The Long March 10B, China’s latest heavy-lift rocket, incorporates a titanium-alloy grid fin system that deploys for aerodynamic control after stage separation at roughly 70 kilometers altitude, according to technical specifications released by the China Aerospace Science and Technology Corporation (CASC). Grid fins have a lineage reaching back to Soviet ballistic missile designs, later adapted by SpaceX for the Falcon 9’s controlled descent.
The fins are one component of a broader reusability architecture that includes four carbon-fiber landing legs, each 3.5 meters long and fitted with shock absorbers, which extend before touchdown. The first stage is powered by seven YF-100K engines, each generating 1,200 kilonewtons of thrust at sea level.
The engines, burning refined kerosene (RP-1) and liquid oxygen in a staged combustion cycle, can throttle down to 40 percent for precision landing maneuvers. CASC developed a new integrated navigation system combining GPS, BeiDou, and inertial measurement units to handle real-time trajectory adjustments during descent. The system is designed to guide the first stage to a designated landing platform, the “Marine Recovery Platform,” which measures 80 meters long and 40 meters wide.
The platform is anchored at 19 degrees north latitude, 112 degrees east longitude. According to the program’s technical documentation, the grid fins, landing legs, engine throttling, and navigation system were validated through more than 200 ground tests and 50 simulated flights before the maiden launch.
Engineering lineage and adaptation
The grid fin itself is a lattice structure that provides aerodynamic control at both subsonic and supersonic speeds. Soviet engineers first deployed them on ballistic missiles, though their modern reusability application was pioneered by SpaceX. The Long March 10B’s fins are fabricated from titanium alloy, chosen for its strength-to-weight ratio and ability to withstand the thermal loads of reentry.
The fins deploy after stage separation at approximately 70 kilometers altitude. The grid fins can pivot to steer the descending stage, working in concert with the engine’s gimbaling during the landing burn.
The landing legs, each 3.5 meters long, are constructed from carbon-fiber composites. They are folded against the stage during ascent and deploy before touchdown. The shock absorbers are designed to handle the vertical velocity at landing.
Propulsion and landing architecture
The seven YF-100K engines are arranged in a cluster. The staged combustion cycle, in which a portion of the fuel is burned in a preburner to drive the turbopumps before entering the main combustion chamber, provides higher efficiency than gas-generator cycles. The engines burn RP-1 kerosene and liquid oxygen.
The 40 percent throttle capability allows the engines to reduce thrust significantly during the final descent, enabling a controlled touchdown rather than a hard impact. The integrated navigation system fuses satellite positioning from both GPS and BeiDou with inertial measurement data to calculate position, velocity, and attitude in real time.
The Marine Recovery Platform is anchored at a fixed location. At 80 meters long and 40 meters wide, it provides a landing area roughly the size of a football pitch. The platform is anchored at 19 degrees north latitude, 112 degrees east longitude.
Testing and validation
The record shows that CASC conducted over 200 ground tests and 50 simulated flights before the maiden launch. These tests included static fire tests of the YF-100K engines at various throttle settings, deployment tests of the grid fins and landing legs in simulated flight conditions, and closed-loop navigation system tests using hardware-in-the-loop simulations. The simulated flights modeled the full descent profile from stage separation through landing, including the aerodynamic regime where grid fins are most effective.
Engineers validated the control algorithms against these simulations before committing to flight. The Long March 10B’s reusability technologies represent a significant step for China’s space program, which has historically relied on expendable launch vehicles.
The ability to recover and reuse the first stage could reduce launch costs and increase flight cadence, though CASC has not yet released cost-per-launch figures or reuse targets. What to watch next: The performance of the grid fins and landing legs on the maiden flight will determine whether CASC proceeds with a recovery attempt on the next mission.
If successful, the Long March 10B could become the first Chinese orbital rocket to land a first stage propulsively, joining the Falcon 9 as one of the few reusable orbital-class boosters in operation.
