Long March 7

Model of the LM-7

The Langer Marsch 7 , LM-7 for short ( Chinese  長征 七號  /  长征 七号 , Pinyin Chángzhēng qīhào , Changzheng-7, CZ-7 for short ) is a family of medium-weight launch vehicles manufactured by the China Aerospace Science and Technology Corporation in the People's Republic of China . The first CZ-7 took off from the Wenchang Cosmodrome on June 25, 2016 . In the basic version, it can transport up to 13.5 tons in a low-earth orbit. Your main task is to be the launch of the Tianzhou cargo spacecraft for the Chinese space station .

history

The history of the rocket goes back to 2006, when Wang Yongzhi (王永志, * 1932), the technical director of the manned space program of the People's Republic of China , pointed out that a supply spaceship with the largest possible loading capacity was needed to supply the planned modular space station needed. The largest launcher in China at the time, the Changzheng 2 F , could only transport 9 t into low-earth orbit (LEO), where the space station was to be placed. This was considered to be too small to be able to supply the station in a reasonably cost-efficient manner.

At first it was thought of developing an improved version of the Changzheng 2F, the so-called "Changzheng 2F / H", where the "H" stands for huàn (换) or "changed". On November 21, 2008, the first working group entrusted with the preliminary planning was set up at the Academy for Launch Vehicle Technology, and in January 2009 the company set up its own office, which from now on was responsible for the development of the rocket. Since pretty much everything on the CZ-7F had been changed for the new launch vehicle, from the fuel to the engines to the stage concept, the company decided in June 2010 to give it a completely new name: "Changzheng 7". On September 25, 2010, the CCP Political Bureau formally approved the construction of the modular space station, and in January 2011, the Changzheng 7 was officially approved and funds were released.

Similar to the Changzheng 5 in 2006 , there were originally five variants of the rocket, numbered A to E, which were all equipped with two core modules with a diameter of 3.35 m. This two-stage nuclear rocket could optionally be expanded with two or four boosters and partially with a third, hydrogen-powered upper stage. Initially, however, the focus was on the development of a two-stage rocket with four boosters, which was originally known as the "CZ-7C" or "CZ 340", ie "3.35 m in diameter with 4 small boosters". In the further course of this rocket, the colloquial name "Changzheng 7" became established.

In July 2011, the development of the first prototype of the Changzheng 7 began. Due to its relatively small diameter, the rocket, unlike the Changzheng 5 , can still be transported by rail; it is designed for both the Xichang cosmodrome in Sichuan and the Xichang cosmodrome to start from Wenchang on the island of Hainan in the very south of China. The challenges are significantly greater in Wenchang: high temperature, high humidity, high salt content in the air and frequent occurrences of rainy days with 5–15 mm of precipitation within 12 hours. Therefore, the Wenchang Cosmodrome was chosen for the first large-scale exercise. At the end of 2014, the prototype of the rocket, disassembled into its components, was brought to Hainan, then assembly and refueling were rehearsed for almost three months. It turned out that due to the low temperature of −183 ° C of the liquid oxygen used as an oxidizer and the high humidity on the outer skin of the rocket, frost and dew droplets formed, which endangered flight safety. The problem could be solved by additional insulation measures and then a new record was set for the time the rocket could stay on the launch pad after refueling. This makes it possible, to a certain extent, to find a safe starting time in the changeable tropical weather on Hainan.

Construction of the final prototype began in May 2015. A year later, on May 8, 2016, the rocket freighter Yuan Wang 21 picked up the real rocket in the port of Tianjin and delivered it six days later, on May 14, after a 1,670 nautical mile journey at the port of Qinglan on Hainan. This was the first time that a missile from the " New Generation Launch Vehicle Production Base " in Tianjin had been transported entirely by sea to Hainan. On May 23, the rocket was fully assembled. After a thorough check, it left the spacecraft assembly building on June 22nd, and the successful maiden flight took off on June 25, 2016 at 12:00 UTC.

construction

The Changzheng 7 follows the modular principle introduced with the Changzheng 5 launch vehicle family in 2002. Its first stage is almost identical to the K-3 booster of the Changzheng 5, with two jointly deflectable, YF-100 type liquid propulsion units developed at the Academy for Liquid Rocket Engine Technology (AALPT) since 2000 , which instead of the well storable but toxic 1 , 1-dimethylhydrazine and dinitrogen tetroxide now use liquid oxygen and rocket kerosene as fuel as with the earlier rockets . The same fuel combination is used in the four boosters, which each have an individually steerable YF-100 engine and, unlike the Changzheng 5, are connected to the core stage at three points. 174 seconds after take-off, the boosters switch off their engines, then they are disconnected. The two engines of the first stage continue to work for 14 seconds, then the first stage separates from the rocket. The almost 3 m long intermediate piece originally located between the first and second stage is then separated from the second stage, and the four YF-115 engines of the second stage, which also work with liquid oxygen and rocket kerosene, are ignited. Here two of the engines are permanently mounted, while the other two can be steered as a pair. The third stage of the Changzheng 7A corresponds to the third stage of the Changzheng 3A with two hydrogen / oxygen engines.

13 m long within the cantilevered payload fairing of 4.2 m diameter, an optional kick stage type Yuanzheng 1A are housed, an apogee motor having a diameter of 2.8 m, which can be up to 20 times ignited and up to seven satellites in subject to a pre-programmed sequence in different orbits.

Mission profile

Jiuquan Taiyuan Xichang Wenchang

Cosmodrome in the People's Republic of China

In the initial euphoria after the project was approved, it was said that the Changzheng-7 family should replace the CZ-2 and CZ-3 missiles. There is no more talk of that today. The main task of the Changzheng 7 continues to be the transport of the Tianzhou supply spaceship , even if the new generation spaceship launched with the Changzheng 5 will be in service in its configuration as a cargo spaceship . The latter can indeed take back freight back to Earth, but with a maximum payload capacity of 4 t it can carry significantly less into orbit than Tianzhou with 6.5 t. Currently (2020) it is planned to use both spaceships, depending on the requirements. With its payload capacity of up to 13.5 t, the Changzheng 7 can also easily transport the 8-ton Shenzhou spaceship into low-earth orbit. Therefore, in order not to endanger the safety of the crew in the event of such a mission, the guaranteed reliability of the missile was set at 98%. For comparison: internationally, a reliability of 95% to 96% is common for manned flights and 91% for unmanned flights. The guaranteed reliability of the Changzheng 2F previously used for launching the Shenzhou spaceships is 97%.

The rocket is suitable for the tropics to a certain extent, i.e. it is suitable for the Xichang and Wenchang cosmodromes. Right from the start, they were designed to be watertight. This means that the Changzheng 7 can also take off in moderate rain , which in China is defined as 5-15 mm per 12 hours. Not only on the southern island of Hainan, but also in Sichuan, with the exception of the period from December to February, this occurs very frequently. In Hainan, there is also the problem of sea breezes outside of the summer typhoon season. The Changzheng 7 and its launch pad at the Wenchang Cosmodrome are designed to withstand stormy winds of force 8 during refueling and final inspections , and the vertical installation in a building with heavy steel doors greatly reduces the dangerous time on the launch pad .

Technical specifications

model	CZ-7	CZ-7A
stages	2	3
height	53.1 m	60.13 m
diameter	3.35 m (10.05 m with boosters)	3.35 m (10.05 m with boosters)
Takeoff mass	597 t (with kick step)	573 t
Start thrust	7200 kN	7200 kN
payload	13.5 t (400 km LEO ) 5.5 t (700 km SSE )	7 t ( GTO )
1st stage (K-3-1)
height	26 m
diameter	3.35 m
Takeoff mass	186 t
Engine	2 × YF-100 with 1200 kN takeoff thrust each
fuel	174 tons of liquid oxygen and rocket kerosene
Booster (4 × K-2-1)
height	26.5 m
diameter	2.25 m
Takeoff mass	81.5 t
Engine	1 × YF-100 with 1200 kN take-off thrust
fuel	75.5 t of liquid oxygen and rocket kerosene
2nd stage (K-3-2)
height	11.5 m
diameter	3.35 m
Takeoff mass	71 t
Engine	4 × YF-115 with 180 kN vacuum thrust each
fuel	65 tons of liquid oxygen and rocket kerosene
3rd stage (H-3-3), only with CZ-7A
height	12.4 m
diameter	3 m
Engine	2 × YF-75 reignited with 78 kN vacuum thrust each
fuel	liquid oxygen and liquid hydrogen

Start list

List updated: March 16, 2020

Performed starts

Serial No.	Date (UTC)	Missile type	Launch site	payload	Type of payload	Payload weight	orbit	Remarks
1	June 25, 2016 12:00 PM	CZ-7 / YZ-1A	Wenchang 201	Return capsule of the multipurpose spaceship Aoxiang ZhixingTiange Feixingqi 1Tiange Feixingqi 2Aolong 1ZGZ Shiyan Zhuangzhi	Prototype of a new re-entry capsule Technologieerprobungssatellit / 12U- Cubesat Technologieerprobungssatellite Technologieerprobungssatellit Technologieerprobungssatellit Technologieerprobung (attached to the upper level)	?	LEO	Success , test flight, first flight of the Langer Marsch 7
2	April 20, 2017 11:41 am	CZ-7	Wenchang 201	Tianzhou-1 SilkRoad-1 (Silu-1)	Unmanned space freighter for Tiangong 2 Earth observation / Cubesat	12910 kg	LEO	success
3	March 16, 2020 1:34 PM	CZ-7A	Wenchang 201	新 技术 试验 六号 (Xīn jìshù shìyàn liù hào)	Technology testing satellite		GTO	Failure

Individual evidence

1. ↑ Daniel Maurat: Long March 5/6 / 7. In: raumfahrer.net. November 5, 2011, accessed February 24, 2020 . 
2. ↑ 蒋正翔: 长征 七号 为 我国 新一代 中型 运载火箭. In: theory.gmw.cn. June 26, 2016, accessed February 23, 2020 (Chinese). 
3. ↑ 李国利 et al .: 长征 七号 诞生 全记录. In: xinhuanet.com. June 26, 2016, accessed February 23, 2020 (Chinese). 
4. ↑ nasaspaceflight.com: China successfully debuts Long March 7 rocket | NASASpaceFlight.com , accessed June 26, 2016
5. ↑ 蒋正翔: 长征 七号 为 我国 新一代 中型 运载火箭. In: theory.gmw.cn. June 26, 2016, accessed February 24, 2020 (Chinese). 
6. ↑ 长征 七号 甲. In: m.calt.com. Retrieved February 22, 2020 (Chinese). 
7. ↑ 李国利 et al .: 长征 七号 运载火箭 搭载 6 类 7 项 新型 载荷 均为 首次 发射 验证. In: gov.cn. June 26, 2016, accessed February 25, 2020 (Chinese). 
8. ↑ Daniel Maurat: Long March 5/6 / 7. In: raumfahrer.net. November 5, 2011, accessed February 25, 2020 . 
9. ↑ 华辉 美食 人: 中国 新 飞船 将 可 重复 用 、 带 6 人 ， 空间站 核心 舱 合 练 3 个 月. In: k.sina.com.cn. January 22, 2020, accessed February 25, 2020 (Chinese). 
10. ↑ 我国 载人 火箭 可靠性 国际 领先. In: calt.spacechina.com. December 16, 2016, accessed February 25, 2020 (Chinese). 
11. ↑ 蒋正翔: 长征 七号 为 我国 新一代 中型 运载火箭. In: theory.gmw.cn. June 26, 2016, accessed February 23, 2020 (Chinese). 
12. ↑ 李国利 et al .: 长征 七号 诞生 全记录. In: xinhuanet.com. June 26, 2016, accessed February 23, 2020 (Chinese). 
13. ↑ SpaceFlight101: Long March 7 - Rockets , accessed June 26, 2016
14. ↑ 长征 七号 甲. In: m.calt.com. Retrieved February 22, 2020 (Chinese).