[Edit this paragraph] Introduction
The Long March 3B (CZ-3B) is a three-stage large-scale liquid launch vehicle. It consists of the Long March 3A carrier rocket and four liquid boosters. It has the advantages of large carrying capacity, strong adaptability and good heredity. It is the launch vehicle with the largest carrying capacity, the most advanced technology and the most complicated structure in China, representing the highest level of launch vehicle technology in China at present, and is also in the forefront of the world space industry.
The Long March 3b is mainly used to launch geosynchronous orbit satellites with a carrying capacity of 5. 1 ton. It is the main rocket used for commercial satellite launching service in China. The take-off mass of the whole rocket is 425 tons, the total length is 54.838 meters, the first and second stage diameters are 3.35 meters, the booster diameter is 2.25 meters, the third stage diameter is 3.0 meters, and the maximum diameter of the satellite fairing is 4.0 meters. Its first stage, booster and second stage use UDMH and N2O4 as propellants, while its third stage uses more efficient liquid hydrogen (LH2) and liquid oxygen (LOX).
The whole rocket consists of rocket body structure, power system, control system, telemetry system, external measurement safety system, taxi propellant management and attitude control system, cryogenic propellant utilization system, separation system and auxiliary system.
Long March 3 B has successfully launched several large satellites, namely Mabuhay, APT-IIR, China Star-/KOOC-0/,SINOSAT-/KOOC-0/.
[Edit this paragraph] Main technical parameters
Parametric booster-one sub-stage, two sub-stages and three sub-stages.
N2O4/UDMH liquid oxygen /LH2 propellant
Engine model dafy5-1dafy6-2dafy20-1(main engine)
DaFY2 1- 1 (running engine)
YF-75
Thrust (kN) 740.4 * 4 296 1.6 742 (main engine)
1 1.8 * 4 (running engine)
78.5 * 2
Engine specific impulse (N*s/kg) 2556.2 2556.2
2922.57 (host)
29 10.5 (swimming engine)
43 12
The diameter of the arrow is 2.25m, 3.35m and 3.300m.
The length of the arrow is15.326m23.272m9.943m12.375m.
The diameter of the fairing is 4.00m.
The length of the fairing is 9.56 meters.
The total length of the rocket is 54.838 meters.
The takeoff mass is 426 tons.
[Edit this paragraph] Description of rocket structure
The first sub-floor of the structural diagram of Long March 3 B
The first sub-stage is 23.272 meters long. The upper part is an oxidizer tank filled with liquid nitrogen tetroxide (N2O4), and the lower part is a combustion agent tank filled with liquid UDMH. The first stage is equipped with DaFY6-2 engine, which consists of four liquid N2O4/UDMH engines in parallel with a thrust of 75 tons. The nozzle of each DaFY6-2 engine can be driven by servo mechanism to swing in one direction to control the attitude of the rocket, and the maximum swing angle is 10 degrees.
roll booster
Length of each booster tube bundle 15.326 m. The upper part is an oxidizer box filled with liquid nitrogen tetroxide (N2O4), and the lower part is a combustion agent box filled with liquid UDMH, with one tail installed at each end. Each of the four boosters is equipped with a DaFY5- 1 engine with a thrust of 75 tons and a fixed nozzle.
divide into sections
The second stage is 9.943 meters long. The upper part of the second stage is equipped with an oxidizer tank of liquid nitrogen tetroxide (N2O4), and the lower part is equipped with a combustion agent tank of liquid UDMH. The second stage is equipped with DaFY20- 1 engine (main engine) with a thrust of 75 tons, DaFY2 1- 1, with four small nozzles and a thrust of 4.8 tons. The nozzle of the main engine is fixed, and the nozzle of the traveling engine can swing in one direction with a maximum swing angle of 60 degrees to control the flying attitude of the arrow.
Three children
The third sub-stage is12.375m long, and the upper part is a combustion agent tank filled with liquid hydrogen (LH2) and the lower part is an oxidant tank filled with liquid oxygen (LOX). The third stage adopts YF-75 hydrogen-oxygen engine, which has the ability of second start. It consists of two independent single-tube engines in parallel, each with a thrust of 8 tons. Driven by the servo mechanism, it can swing in both directions, and the maximum comprehensive swing angle is 4 degrees, which controls the flight attitude of the third-stage arrow.
satellite fairing
During the flight of the rocket through the atmosphere, the satellite fairing at the top of the rocket protects the satellite from all kinds of interference from the atmosphere. The satellite fairing provides a good environment for the satellite. The satellite fairing of the Long March 3 B rocket consists of an end cover, a biconical section, a cylindrical section and an inverted cone section. The end cover is made of glass fiber reinforced plastic, which has good radio wave permeability. The biconical section and the cylindrical section are made of metal honeycomb materials, and the inverted conical section is made of chemical milling alloy materials. If necessary, the radio transmission window and the operation window can be opened on the cylindrical section and the biconical section. The fairing of Changsanyi rocket is 9.56 meters long, with a maximum outer diameter of 4.0 meters and a maximum static envelope diameter of 3.65.
Star-arrow docking
The Long March 3B rocket can provide various mechanical interfaces, but generally it provides the standard 937B and 1 194 mechanical interfaces. The lower end frame of the satellite is butted with the upper end frame of the payload bracket of the rocket and locked with a belt.
[Edit this paragraph] Carrying capacity
The standard geosynchronous transfer orbit (GTO) carrying capacity of the Long March 3B rocket is 5. 1 ton. The standard geosynchronous orbit parameters and orbit accuracy are listed in the following table:
Parameter standard GTO orbit parameter orbit accuracy (3s)
Perigee altitude is 200km 30km and 30 km.
The apogee height is 35786 km, and the semi-major axis 120 km.
Orbit inclination is 28.5 0.21.
The perigee amplitude angle is179.6 0.6.
The standard GTO parameters represent the orbital parameters when the satellite is separated from the rocket. Users can choose different orbits according to the needs of satellites and the carrying capacity of rockets. If the carrying capacity is surplus, the Long March 3 B rocket can send the satellite into low inclination orbit or super-synchronous transfer orbit, thus prolonging the on-orbit life of the satellite.
[Edit this paragraph] Flight sequence
Task description
The Long March 3b can send satellites into geosynchronous transfer orbit (GTO). In a typical GTO mission, the first and second stages of Chang 'e-3 B rocket first sent the combination of satellite and third stage into a circular parking orbit, and then the third stage flew for more than 600 seconds. After the assembly is reoriented under the control of the rocket control system, the three-stage engine is re-ignited, and the assembly is sent to the target GTO orbit, and finally the third stage is separated from the satellite. See the mission diagram of the Long March 3b GTO.
Major flight event
The main flight events of Long March 3B are as follows:
Booster separation:
Each booster is connected with the rocket core stage through the rod structure of the front connection surface and the ball head structure of the rear connection surface respectively. After the booster engine is turned off, the explosion bolt and the separation nut used for connection are unlocked respectively, the small solid separation rocket installed on the booster is ignited, the booster is pushed away from the rocket core stage, and the booster falls freely to complete the separation.
One child/two children separated:
The primary/secondary separation is called "thermal separation". After the first-stage engine is turned off, the second-stage main engine is ignited, and the explosion bolt connecting the two stages is detonated to unlock, so that the first stage is pushed away by the high-speed airflow ejected by the second-stage engine, and the first stage and the second stage are separated.
Fairing guard:
The fairing is thrown in the way of "unlocking-steering-separating". In the horizontal direction, the fairing is connected with the third stage through the 12 transverse explosion bolt, and in the vertical direction, the two halves of the fairing are connected with a detonating cord through two longitudinal explosion bolts. When throwing the engine hood, the 12 transverse explosion bolt and the 2 longitudinal explosion bolts explode at the same time, and the longitudinal detonating cord is unlocked within 0. 1 sec, and the separating spring installed on the third front frame pushes the two halves of the fairing apart. The two halves of the fairing rotate around the hinge on the front frame of the third stage, and the fairing separates and falls with the acceleration of the rocket.
In the process of range hood, collision and pollution will not occur.
Underground/underground separation:
Two-stage/three-stage separation is called "cold separation". After the main engine and walking engine of the second stage are turned off, the small acceleration rocket installed on the third stage is ignited, thus generating an acceleration in the flight direction of the rocket, which makes the propellant of the third stage sink and facilitates the ignition and start of the third stage engine. At the same time, the explosive bolt connecting the second stage and the third stage was detonated and unlocked, and the small thrust rocket installed on the second stage was ignited to generate reverse acceleration, and the second stage was separated from the third stage.
Satellite/tertiary separation:
The separation of the satellite from the third stage is realized by the separation force of the separation spring. When the rocket control system sends an instruction to separate the satellite from the rocket body, the pollution-free explosion bolt on the belt connecting the satellite and the payload bracket is detonated and unlocked, and the unlocked belt is pulled back by the tension spring installed on the payload bracket. The satellite was pushed away from the rocket by a separating spring.
Typical flight sequence
Event flight time (seconds)
Primary ignition -3
Take-off 0.00
Program to 1 1.0
Booster separation 127.24
Primary/secondary separation 147.36
Cowl guard 232.4
Two-stage/three-stage separation and three-stage engine ignition+0.5.50000.000000000005
Three-stage engine shut down once 63 1.32
Secondary ignition of three-stage engine 128 1.23
Secondary shutdown of three-stage engine 1459+0
Satellite/three-stage separation 1559.907
[Edit this paragraph] Launch site operation
The Long March 3B rocket was launched in xichang satellite launch center. The rocket will be loaded on the train and transported from Beijing to Xichang, Sichuan, where various testing and operation activities will be carried out at the technical center and launch center in xichang satellite launch center, including four general inspections of the technical center, the transfer of the rocket from the technical center to the launch center, the vertical docking of the rocket sub-stages at the launch center, four general inspections of the launch center, joint satellite/rocket operation, rocket refueling and final launch countdown.
[Edit this paragraph] Chang Sanyi's previous launches
1996.2.25 international communication satellite failure.
1997.8.20 "Mahaibe" satellite succeeded.
1997.10.17 "Asia-Pacific II" succeeded.
1998.5.3 "Zhongwei No.1" was successful.
1998.7. 18 "CIGNA 1No." succeeded.
April 2005 12 "Asia-Pacific VI" was successful.
2006. 10.29 "CIGNA II" was successful.
May 200714 "Nixing No.1" was successful.
On June 9, 2008, "Zhongxing 9" was successfully launched.
2008. 10.30 Venezuela-1 communication satellite was successful.
On August 3 1 2009, China launched the Indonesian "Parapa -D" communication satellite by the Long March 3B carrier rocket in xichang satellite launch center. The first and second stages of the rocket were flying normally, but the third stage was abnormal after two ignitions, and it was impossible to send the satellite into the scheduled orbit.
At about 22: 00 on August 3, 2009, the commercial communication satellite "Parapa -D" was captured by the ground monitoring and control network. The satellite underwent perigee orbit change on September 1. The orbit change was successful and the satellite was in normal condition.