# Yuanzheng

Yuanzheng (Chinese: 远征; pinyin: Yuǎn Zhēng; lit. 'Expedition') is a restartable upper stage developed by the China Academy of Launch Vehicle Technology (CALT) for the Long March rocket family.
The Yuanzheng stage enables the Chinese launch vehicles to deploy payloads directly to high-energy orbits such as medium Earth orbit (MEO) and geosynchronous orbit (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 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 6.5 kN (1,500 lb$_f$) with a specific impulse of 315.5 seconds. It uses the storable hypergolic propellants unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (N$_2$O$_4$), 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 and 3C, YZ-1A for Long March 7, YZ-1S for Long March 2C, YZ-2 for Long March 5, and YZ-3 for Long March 2D.

## History

Yuanzheng was presented in a 2013 paper and performed its first mission on 30 May 2015. The debut flight of the Long March 7 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 Long March 5 (YZ-2) in 2016, Long March 2C (YZ-1S) and Long March 2D (YZ-3) in 2018.
| Flight No. | Date (UTC) | Carrier Rocket | Stage Model | Serial Number | Launch site | Mission | Result |
| 01 | 2015-03-30 13:52 | Long March 3C | YZ-1 | Y1 | Xichang | BDS I1-S | Success |
| 02 | 2015-07-25 12:29 | Long March 3B | YZ-1 | Y2 | Xichang | BDS M1-S / BDS M2-S | Success |
| 03 | 2016-02-01 07:29 | Long March 3C | YZ-1 | Y3 | Xichang | BDS M3-S | Success |
| 04 | 2016-06-25 12:00 | Long March 7 | YZ-1A | Y1 | Wenchang | Inaugural Mission | Success |
| 05 | 2016-11-3 12:43 | Long March 5 | YZ-2 | Y1 | Wenchang | Inaugural Mission | Success |
| 06 | 2017-11-5 11:45 | Long March 3B | YZ-1 | Y4 | Xichang | BDS-3 M1 BDS-3 M2 | Success |
| 07 | 2018-01-11 23:18 | Long March 3B | YZ-1 | Y5 | Xichang | BDS-3 M7 BDS-3 M8 | Success |
| 08 | 2018-02-12 05:03 | Long March 3B | YZ-1 | Y6 | Xichang | BDS-3 M3 BDS-3 M4 | Success |
| 09 | 2018-03-29 17:56 | Long March 3B | YZ-1 | Y7 | Xichang | BDS-3 M9 BDS-3 M10 | Success |
| 10 | 2018-07-29 01:48 | Long March 3B | YZ-1 | Y8 | Xichang | BDS-3 M5 BDS-3 M6 | Success |
| 11 | 2018-08-24 23:52 | Long March 3B | YZ-1 | Y9 | Xichang | BDS-3 M11 BDS-3 M12 | Success |
| 12 | 2018-09-19 14:07 | Long March 3B | YZ-1 | Y10 | Xichang | BDS-3 M13 BDS-3 M14 | Success |
| 13 | 2018-10-09 02:43 | Long March 2C | YZ-1S | Y1 | Jiuquan | Yaogan 32A, 32B | Success |
| 14 | 2018-10-15 04:23 | Long March 3B | YZ-1 | Y11 | Xichang | BDS-3 M15 BDS-3 M16 | Success |
| 15 | 2018-11-18 18:00 | Long March 3B | YZ-1 | Y12 | Xichang | BDS-3 M17 BDS-3 M18 | Success |
| 16 | 2018-12-29 08:00 | Long March 2D | YZ-3 | Y1 | Jiuquan | Yunhai-2 01, 02, 03, 04, 05, 06 Hongyan-1 | Success |
| 17 | 2019-09-22 21:10 | Long March 3B/E | YZ-1 | Y13 | Xichang | BDS-3 M23 BDS-3 M24 | Success |
| 18 | 2019-11-23 00:55 | Long March 3B/E | YZ-1 | Y14 | Xichang | BeiDou-3 M21 BeiDou-3 M22 | Success |
| 19 | 2019-12-16 07:22 | Long March 3B/E | YZ-1 | Y15 | Xichang | BeiDou-3 M19 BeiDou-3 M20 | Success |
| 20 | 2021-08-24 11:15 | Long March 2C | YZ-1S | Y2 | Jiuquan | RSW-01 RSW-02 unknown payload | Success |
| 21 | 2021-11-03 07:43 | Long March 2C | YZ-1S | Y4 | Jiuquan | Yaogan 32-02A, 32-02B | Success |
| 22 | 2022-05-20 10:30 | Long March 2C | YZ-1S | Y5 | Jiuquan | LEO Test Sat 1/2 Digui Tongxin Weixing | Success |
| 23 | 2023-07-09 11:00 | Long March 2C | YZ-1S | Y3 | Jiuquan | Hulianwang Jishu Shiyan 1A Hulianwang Jishu Shiyan 1B | Success |
| 24 | 2023-11-16 03:55 | Long March 2C | YZ-1S | Y9 | Jiuquan | Haiyang-3A | Success |
| 25 | 2023-11-23 10:00 | Long March 2D | YZ-3 | Y2 | Xichang | Hulianwang Jishu Shiyan 2A Hulianwang Jishu Shiyan 2B Hulianwang Jishu Shiyan 2C | Success |
| 26 | 2023-12-26 03:26 | Long March 3B/E | YZ-1 | Y16 | Xichang | BeiDou-3 M25 BeiDou-3 M26 | Success |
| 27 | 2023-12-30 00:13 | Long March 2C | YZ-1S | Y17 | Jiuquan | Hulianwang Jishu Shiyan 4A Hulianwang Jishu Shiyan 4B Hulianwang Jishu Shiyan 4C | Success |
| 28 | 2024-03-13 12:51 | Long March 2C | YZ-1S | Y18 | Xichang | DRO-A DRO-B | Failure |
| 29 | 2024-03-21 05:27 | Long March 2D | YZ-3 | Y3 | Jiuquan | Yunhai-2 Group 02 | Success |
| 30 | 2024-09-19 01:14 | Long March 3B/E | YZ-1 | Y17 | Xichang | BeiDou-3 M27 BeiDou-3 M28 | Success |

## Versions

Currently, there is known to be five versions:
* Yuanzheng-1 (AKA YZ-1) (Chinese: 远征一号; pinyin: Yuǎn Zhēng Yī Hào; lit. 'Expedition One'): Initial version used with the Long March 3. It could perform missions of 6.5 hours, make two ignitions, perform one spacecraft deployment operation.
* Yuanzheng-1A (AKA YZ-1A) (Chinese: 远征一号甲; pinyin: Yuǎn Zhēng Yī Hào Jiǎ; lit. 'Expedition One A'): Improved version used with the Long March 7. 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) (Chinese: 远征一号商业型; pinyin: Yuǎn Zhēng Yī Hào Shāng Yè Xíng; lit. 'Expedition One Commercial Version'): Improved version used with the Long March 2C.
* Yuanzheng-2 (AKA YZ-2) (Chinese: 远征二号; pinyin: Yuǎn Zhēng Èr Hào; lit. 'Expedition Two'): New version used with the 5.2 m (17 ft) Long March 5 upper stage.
* Yuanzheng-3 (AKA YZ-3) (Chinese: 远征三号; pinyin: Yuǎn Zhēng Sān Hào; lit. 'Expedition Three'): New version used with the Long March 2D.