CZ-3 Space Launch Vehicle

Long March 3 (LM-3) is a three-stage launch vehicle, primarily fintended or sending spacecraft into Geosynchronous Transfer Orbit. The development of the first and second stages of LM-3 is based on the first and second stages of LM-2C. The 1st and 2nd stages of an LM-3 launch vehicle, based on the LM-2C, are designed and manufactured by the Shanghai Academy of Spaceflight Technology. Most of the technology and flight hardware used in LM-3 have been qualified and proved by LM-2C. The third stage of LM-3 was newly developed. It is powered by a cryogenic engine, using liquid oxygen and liquid hydrogen as propellants.

The CZ-3 launch vehicle was introduced in 1984 to provide the PRC with its initial GEO mission capability. The vehicle also marked the first use of a high technology upper stage and led to China's entry into the commercial space launch services market. The CZ-3 is a 3-stage launch vehicle with the first two stages essentially identical to the CZ-2C. The third stage utilizes a restartable, liquid oxygen/liquid hydrogen engine designated YF-73. The GTO capacity of the CZ-3 is 1.5 metric tons (References 159, 164, 180-184). The Long March-3 is a multi-purpose 3-stage carrier rocket. It is 43.25 m long, and has maximum diameter of 3.35 m; its lift-off weight is approximately 202 tons and its lift-off thrust is 280 tons. The third stage is a high-energy, low-temperature, liquid-oxygen and liquid-hydrogen engine. Liquid hydrogen has a boiling point of 253°C below zero; it also has a low density and a low heat conduction coefficient, small surface tension, and low coefficient of viscosity. Its leakage rate is 50 times as high as that of water. Under standard atmospheric pressure, a tiny spark will ignite a mlxuter containing as little as 4 percent hydrogen and result in an explosion.

The hydrogen-oxygen engine was introduced in the 1960's; while its performance is superior, there are many difficult technical problems associated with it. For example, if the liquid hydrogen tank is not adequately insulated, the liquid hydrogen will evaporate rapidly, causing the tank pressure to rise which may lead to an explosion. If a small amount of air exists in the fueling tube, the nitrogen and oxygen in the air will solidify as the temperature drops sharply; then any vibration during the engine operation will produce sparks due to friction between the solid particles and create a strong explosion. Thereare also numerous other technical problems.

Thanks to a nationwide cooperative effort, the Long March-3 carrier rocket was born in 1984. The Long March-3 rocket was flight tested for the first time on 29 January 1984, where a satellite was launched into a 6,000-km elliptic orbit. Although this flight test was a success, it also revealed a number of weak links of the design. The inaugural flight from the Xichang Satellite Launch Center of the CZ-3 on 29 January 1984 failed when the third stage did not restart to maneuver from a LEO parking orbit to GTO. The payload was an experimental communication satellite.

During this flight, the third stage engine thrust was lost after engine restart. This caused the satellite to be placed into an elliptical orbit. However, most of the test and experimental investigations planned for the flight were carried out. A rigorous analysis was made for the launch vehicle telemetry data and the cause of the malfunction was identified as being an abnormal mixture ratio in the gas generator for the third stage. This caused the gas temperature to reach a high level to make the turbine shell burn out, resulting in the loss of thrust. In order to launch an experimental communications satellite into a geosynchronous orbit, these weak links must be carefully reviewed and the problems must be resolved before launch. The third stage engine was modified and four ground tests were carried out.

The weather in April is nice and calm in the great southwest, but after April the weather begins to change rapidly. Therefore, if one misses the "launch window" during April, the launch must be postponed by one year. Faced with this time-critical task, this team of 20-year veteran rockets builders accepted the challenge. On 30 January, both the launch site and the research base organized special teams to analyze the weak links and to suggest methods of solution. The data collected by the receiving ships were sent via the highest priority route to the hands of the key personnel, who performed analyses, computations and experiments around the clock in order to determine the cause of the problem. Then, a group of designers gathered to pool their wisdom together to arrive at an improved design; production of the test parts was started immediately and tests were scheduled. Two months of work was completed in 15 days.

By 01 March, two different measures of improvement had been introduced, but the chief designer of the communications satellite program, Ren Xinmin, still felt uncomfortable; he preferred to have a third measure of improvement implemented. But time was running out. After careful consideration, it was decided to go ahead with the improvement. To race against time, two teams were organized; each team worked day and night and completed the design, production, and testing in only 4 days and 3 nights. On 22 March, the redesigned parts were shipped to the launch site; on 23 March they were installed on the rocket which was already standing on the launch pad. The installation was difficult because the engine compartment was filled with delicate parts and conduits; the three technicians could only work in a crouched position, nevertheless, they completed the work in 4 days.

The next six missions (April 1984 - April 1990) were successful. On 8 April 1984, seventy days after the test flight, a Long March 3 with the modified third stage engine was launched. It was a perfect success. The Long March-3 rocket successfully launched a 1,430-kg experimental communications satellite into a geosynchronous orbit, which proved that China was now one of the advanced nations in the world in terms of carrier rocket technology. After that, several chinese communication satellites were launched by LM-3. On 7 April 1990, the seventh launch of LM-3 was carried out, delivering the first foreign communication satellite, AsiaSat 1, into a predetermined GTO. It was a total success and marked the real entrance of Long March launch vehicles for China into the international commercial launch service market.

Only one CZ-3 mission was attempted during 1991-1993, and this flight resulted in the stranding of a domestic PRO communications satellite in the wrong orbit. The eighth launch of LM-3 was conducted on 28 December 1991, and orbital insertion into the planned LEO was accomplished. However, when the third stage was reignited, a propellant pressurization malfunction caused a premature shut-down. Therefore, the satellite did not enter into the specified GTO, leaving the payload with an apogee of only 2,450 km instead of nearly 36,000 km as required. Analyses on flight telemetry data and tests indicated that the source of the failure was due to a speedy drop in pressure inside the the helium gas sphere for engine control caused by a leakage in the piping of gas feed. Measures have been taken to eliminate the possibility of this type of failure in the later launches.

On July 21, 1994, LM-3 with some improvement for APSTAR-1 mission, was successfully launched. To raise the launch reliability, the main measure on APSTAR-1 mission of LM-3 was taken, such as the leak-proof methods for gas feed pipes, more gas vessels for 3rd stage engine control and more gas vessels for 3rd stage pressurization. On July 3, 1996, LM-3 once again sent another APSTR-1A into GTO successfully.

LM-3 prematurely shut off for 48 seconds on August 18, 1996, during its ChinaStar-7 mission. The Hughes HS-376 satellite called the ChinaSat-7 (Zhongxing 7) was left in an unusable orbit due incomplete burn of the third stage of the rocket. The root cause of this falure is deflagration occurred occasionally at LH2 injector area of gas generator, which was caused by frozen oxygen due to inadequate of gas purging during coast flight. The corrective measures had been passed the review and implemented on LM-3 series launch vehicles.

A successful launch of a LM-3 occurred on 03 July 1996, launching China's communications satellite Apstar 1A. The People's Republic's space program showed strong signs of recovery during 1997, launching a CZ-3 from Xichang on 10 June 1997 carrying the country's first geosynchronous weather satellite (Feng Yun 2).

LM-3
	Background Information First Launch: January 1984 Flight Rate: 2-3 per year Launch Site: Xichang Space Launch Center, China Capability: 3,100 lb to GTO, 31.1 degrees 11,000 lb to LEO 2,100 lb to Earth Escape Trajectory History Chinese rocket program started in the late 1950s Evolved from Chinese surface-to-surface (CSS) series IRBMs LM-3 is enhanced version of the LM-2; addition of a cryogenic upper stage Description Three-stage liquid fueled vehicle Stage 1 consists of four YF-20 motors burning UDMH/N2O4 providing a total thrust of 625,800 lb Stage 2 uses one YF-22 engine burning UDMH/N2O4 providing a total thrust of 172,100 lb Stage 3 uses one YF-73 engine burning LOX/LH2 providing a thrust of 9,900 lb Profile Length: 144 ft Launch Weight: 444,400 lb Diameter: 11 ft Liftoff Thrust: 625,800 lb Payload Fairing: 19.2 ft x 8.5 ft