CALT introduced the Long March 3A in the early 1990s as a successor to the Long March 3. With an increased payload capacity of 2,600 kg to GTO, the 3A model was positioned as a contender for the international commercial launch market against foreign designs. By adopting a modular design approach, the launch vehicle would also be developed into different configurations to meet different mission requirements.
Although the 3A model inherited the first- and second-stage of the Long March 3, the rest of the launch vehicle was completely redesigned, with 70% of its onboard technologies being new. The most significant improvement was the third-stage, which featured a new LOX/LH2 engine designated YF-75. The engine consisted of two 78.5 kN-thrust chamber motors with fully swinging nozzles (4° on each direction), and had the re-ignition capability to allow the engine to switch on and off during the flight to achieve maximum payload efficiency. The vacuum thrust of the YF-75 was 78% higher than that of the old YF-73.
The Long March 3A also features a fuel management system, which used low-temperature helium gas carried inside the 7 onboard canisters to keep the liquid oxygen and liquid hydrogen tanks pressurised. This measure increased the payload capacity by 200 kg, and also allowed the engine to be switched on and off freely during the flight to give better adaptability to different missions. The launch vehicle is capable of launching either a single or dual payloads, and can deliver the payload to either the GTO or Super GTO.
The Long March 3A development began in the mid-1980s in response to the demand for a launch vehicle with increased payload capacity to lift the new-generation Dong Fang Hong 3 (DFH-3) communications satellite (Project 862). In 1985, CALT proposed to improve the existing Long March 3 in two phases. The first phase aimed to introduce a new third-stage featuring the 157 kN YF-75 engine. The second phase would add 2 or 4 strap-on liquid boosters to the core stage.
The DFH-3 / Long March 3A concept was officially approved in February 1986, with the first flight scheduled for 1992. However, the development of the Long March 3A was delayed as priority was given to the development of the Long March 2E, and as a result, the Long March 3A was not ready until 1994.
On 8 February 1994, a Long March 3A launched from Xichang Satellite Launch Centre successfully placed its payloads, a dummy DFH-3 satellite named Kuafu 1, and a scientific research satellite Shijian 4, into their intended orbits. Nine months later, on 30 November, a second Long March 3A mission successfully placed the first operational DFH-3 satellite into GTO (apogee: 36,197 km; perigee: 200 km).
Since then, the Long March 3A has been serving as a reliable workhorse for China’s geostationary launch missions, with a success rate of 100%. On 24 October 2007, the launch vehicle lofted China’s first lunar orbiting probe into orbit.