Yuanzheng () is a restartable

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

developed by the China Academy of Launch Vehicle Technology (CALT) for the Long March rocket family. The Yuanzheng stage enables the Chinese

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

s to deploy payloads directly to high-energy orbits such as

medium Earth orbit A medium Earth orbit (MEO) is an geocentric orbit, Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between above sea level.

(MEO) and

geosynchronous orbit A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...

(GSO). Since the Long March third stage cannot restart, it cannot circularize a GSO or GEO orbit from a geosyncronous transfer orbit ( GTO). With its restart capability, Yuanzheng has enabled the deployment of satellite pairs for the

BeiDou Navigation Satellite System The BeiDou Navigation Satellite System (BDS; ) is a satellite-based radio navigation system owned and operated by the China National Space Administration. It provides geolocation and time information to a BDS receiver anywhere on or near the ...

in MEO and communications satellites in GSO. This eliminates the need for the spacecraft to include a liquid apogee engine or an apogee kick motor. Yuanzheng has a thrust of with a

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...

of 315.5 seconds. It uses the storable

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

propellants

unsymmetrical dimethylhydrazine Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. At room temperature, UDMH is a colorle ...

(UDMH) and

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

(), and can perform at least two burns within its rated life of 6.5 hours, sufficient to reach the transfer orbit apogee, and perform the circularization burn from there. Operational variants are designated YZ-1 for

Long March 3B The Long March 3B (), also known as the CZ-3B and LM-3B, is a Chinese orbital launch vehicle. Introduced in 1996, it is launched from Launch Area 2 and 3 at the Xichang Satellite Launch Center in Sichuan. A three-stage rocket with four strap-on ...

and 3C, YZ-1A for

Long March 7 The Long March 7 (), or Chang Zheng 7 in pinyin, abbreviated LM-7 for export or CZ-7 within China, originally Long March 2F/H or Chang Zheng 2F/H, nicknamed Bingjian (), is a Chinese liquid-fuelled launch vehicle of the Long March family, dev ...

, YZ-1S for

Long March 2C The Long March 2C (LM-2C), also known as the Chang Zheng 2C (CZ-2C), is a Chinese orbital launch vehicle, part of the Long March 2 rocket family. Developed and manufactured by the China Academy of Launch Vehicle Technology (CALT), the Long M ...

, YZ-2 for

Long March 5 Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào) or Changzheng 5 (CZ-5), also known by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicl ...

, and YZ-3 for

Long March 2D The Long March 2D (), also known as the Chang Zheng 2D, CZ-2D, and LM-2D, is a Chinese two-stage orbital carrier rocket mainly used for launching LEO and SSO satellites. It is manufactured by the Shanghai Academy of Spaceflight Technology ( ...

Models

History

Yuanzheng was presented in a 2013 paper and performed its first mission on 30 May 2015. The debut flight of the

in 2016 included an improved version called Yuanzheng-1A that can flexibly deploy multiple payloads into various target orbits. Further variants were later deployed for

(YZ-2) in 2016,

(YZ-1S) and

(YZ-3) in 2018.

Versions

Currently, there is known to be five versions: * Yuanzheng-1 (AKA YZ-1) (): Initial version used with the

Long March 3 The Long March 3 (), also known as the Changzheng 3, CZ-3 and LM-3, was a Chinese orbital carrier rocket design. They were all launched from Launch Area 3 at the Xichang Satellite Launch Center. It was a three-stage rocket, and was mostly used ...

. It could perform missions of 6.5 hours, make two ignitions, perform one spacecraft deployment operation. * Yuanzheng-1A (AKA YZ-1A) (): Improved version used with the

. Improved version with mission life extended to 48hs, capability to perform at least 9 ignitions and ability to do 7 different separation events. It also includes improved thermal control system, guidance algorithms and orbit planning for multiple payload deployment missions. It will be used as the base system for future deep space propulsion stages, space tugs and orbital servicing and debris removal spacecraft. * Yuanzheng-1S (AKA YZ-1S) (): Improved version used with the

. * Yuanzheng-2 (AKA YZ-2) (): New version used with the

upper stage. * Yuanzheng-3 (AKA YZ-3) (): New version used with the

References

{{DEFAULTSORT:Yuanzheng-1 Rocket stages