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Changzheng 4B
The Changzheng 4B (CZ-4B, or “Long March 4B”) was developed in the late 1990s for launching the Ziyuan 1 (also known as CBERS 1) polar orbit remote-sensing satellite. Development of the satellite began in 1989 and the rocket made the first flight in May 1999.
The CZ-4B was generally similar to the CZ-4A in design. The most significant modification was adopting a newly-designed payload fairing 8.48m in length and 3.35m in diameter in order to house the large remote-sensing satellite. Other improvements included:
- Increased payload capacity;
- Replacing the original mechanical-electrical flight control with a digital electronic control;
- Improved telemetry, tracking & control system and self-destruction mechanism, with smaller size and reduced weight;
- A revised nuzzle design in the second-stage for better high-altitude performance;
- A propellant management system on the second-stage of the rocket to reduce the spare propellant requirement, thus increasing the vehicle’s payload capability;
Residual Propellant Venting System
On 4 October 1990, the third-stage of a CZ-4A, which had just successfully delivered the Fengyun 1B satellite in the second flight of the rocket, exploded in the 895km orbit, producing more than 80 trackable space debris pieces.
In 1993, Chinese space engineers confirmed that the third-stage of the new CZ-4B launch vehicle had been redesigned to include a residual propellant venting system. However, the system was not included on the early variant of the CZ-4 rocket, as the satellite designer was concerned that this may damage the satellite.
Another third-stage of a CZ-4B rocket exploded on 11 May 2000 after it had placed the Ziyuan 1 (CBERS-1) satellite into the orbit on 14 October 1999, producing over 300 trackable space debris pieces in a 735km orbit.
The residual propellant venting system was then swiftly installed on all subsequent CZ-4B flights. No further explosion had occurred since then.
CZ-4B
Specifications
| Stages | 3 |
| Boosters | 0 |
| Overall length | 45.576 m |
| Core stage diameter | 3.35 m |
| Take-off mass | 248.47 t |
| Take-off thrust | 2,971 kN |
| Thrust-weight ratio | 1.21 |
| Payload capacity | 2,295 kg to 700 km SSO 1,473 kg to 900 km SSO |
| First flight | 1999 |
| Launch site | Taiyuan |
| Status | Operational |
Stages
| First-stage | Second-stage | Third-stage | |
| Length | 24.65 m | 10.40 m | 4.93 m |
| Diameter | 3.35 m | 3.35 m | 2.9 m |
| Gross mass | 193.33 t | 38.326 t | 14.56 t |
| Empty mass | 9.998 t | 2.932 t | 1.727 t |
| Propellant mass | 183.34 t | 35.374 t | 12.814 t |
| Engine | YF-21B | (Main) YF-22B (Swivelling) 4 X YF-23B |
YF-40 |
| Propellant | N2O4/UDMH | N2O4/UDMH | N2O4/UDMH |
| Thrust* | 2,971 kN | (Main) 742 kN (Swivelling) 4X 47.1 kN |
1.1.03 kN |
| Isp* | 2,550 N.s/kg | (Main) 2,922.4 N.s/kg (Swivelling) 2,834.0 N.s/kg |
2,971.4 N.s/kg |
| Burn time | (Main) 126.8 s (Swivelling) 136.8 s |
359.74 s |
* Sea-level values for the first-stage, and vacuum values for the second- and third-stage
Payload Fairing
| Length | 8.483 m |
| Diameter | 3.35 m |
| Mass | 1,350 kg |
Last updated: 23 February 2012