Long March 7

The Long March 7 (Chinese: 长征七号运载火箭), 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 (冰箭; 'the Ice Arrow'), is a Chinese liquid-fuelled carrier rocket of the Long March family, developed by the China Aerospace Science and Technology Corporation.[4] It made its inaugural flight on 25 June 2016.

Long March 7

Long March 7 "Bingjian" model, 2015 Paris Air Show
Function	Medium to heavy launch vehicle
Manufacturer	CALT
Country of origin	China
Size
Height	CZ-7: 53.10 metres (174.2 ft) CZ-7A: 60.13 metres (197.3 ft) [1]
Diameter	3.35 metres (11.0 ft)
Mass	CZ-7: 597,000 kilograms (1,316,000 lb) [2] CZ-7A: 573,000 kilograms (1,263,000 lb) [1]
Stages	CZ-7: Two CZ-7A: Three[3]
Capacity
Payload to LEO (200 x 400 km x 42°)	13,500 kilograms (29,800 lb)
Payload to GTO	5,500 kilograms (12,100 lb) to 7,000 kg (15,000 lb) [3]
Associated rockets
Family	Long March
Comparable	Delta IV, Atlas V, Falcon 9 v1.1, GSLV Mk.III, H-IIA
Launch history
Status	Active
Launch sites	Wenchang, LC-2
Total launches	3 (7:2, 7A:1)
Successes	2 (7:2, 7A:0)
Failures	1 (7:0, 7A:1)
First flight	25 June 2016
Last flight	Active
stage – K2 booster
Length	27 metres (89 ft)
Diameter	2.25 metres (7 ft 5 in)
Engines	1 YF-100
Thrust	SL: 1,200 kilonewtons (270,000 lbf) Vac: 1,340 kilonewtons (300,000 lbf)
Specific impulse	SL: 300 seconds (2.9 km/s) Vac: 335 seconds (3.29 km/s)
Fuel	RP-1 / LOX
First stage – K3 core module
Diameter	3.35 metres (11.0 ft)
Engines	2 YF-100
Thrust	SL: 2,400 kilonewtons (540,000 lbf) Vac: 2,680 kilonewtons (600,000 lbf)
Specific impulse	SL: 300 seconds (2.9 km/s) Vac: 335 seconds (3.29 km/s)
Fuel	RP-1 / LOX
Second stage
Diameter	3.35 metres (11.0 ft)
Engines	4 YF-115
Thrust	706 kilonewtons (159,000 lbf)
Specific impulse	342 seconds (3.35 km/s)
Fuel	RP-1 / LOX
Third stage (CZ-7A)
Diameter	3.0 m (9.8 ft)
Empty mass	2,800 kg (6,200 lb)
Gross mass	21,000 kg (46,000 lb)
Propellant mass	18,200 kg (40,100 lb)
Engines	2 × YF-75
Thrust	167.17 kN (37,580 lbf)
Specific impulse	4,295 m/s (438.0 s)
Burn time	478 seconds
Fuel	LH2 / LOX

Designed as a replacement of the Long March 2F, Long March 7 and its variants are expected to be the workhorse of the fleet, eventually accounting for around 70% of all Chinese launches. Long March 7 will also play a critical role in the Chinese Space Station. It was used to launch the Tianzhou robotic cargo spacecraft, and will eventually replace the Long March 2F as China's crew-rated launch vehicle.[4]

Since 2020, in addition to the base Long March 7 configuration, there is the Long March 7A (CZ-7A) variant which differs from the base CZ-7 by the addition of a liquid hydrogen-liquid oxygen third stage inherited from the third stage of the Long March 3B.[3]

History

The Long March 7 project started in 2008 with the formation of the development team within the traditional designer of space launch vehicles, CALT.[5] With the acquisition of the RD-120 technology and development of the YF-100 and YF-115 engines, the original plan was to re-engine the Long March 2F. The Long March 2F/H, as it would have been called, would "just" switch from N₂O₄ / UDMH to a LOX / kerosene propellant and improved thrust engines to offer better performance. But the switch resulted in a cascade of changes that increased the project complexity significantly.[6]

At the same time, the original Long March 5 project was expected to include heavy, medium and light versions. Since the Long March 2F/H and the medium Long March 5 had significant overlaps, it was decided to merge both projects. This way, the high reliability and flight legacy components and technologies of the Long March 2F were merged with the new technologies developed for the Long March 5.[6] Although finished nearly at the same time, the Long March 6 was a completely separate product developed by a young team within SAST. As such, it shares little more than tank diameters and propulsion with the LM-5 and LM7, but does cover the range of payloads between the medium Long March 7 and the very light Long March 11.[7]

In 2010, the project name was changed officially to Long March 7. According to the project deputy manager, Zhang Tao, the project required eleven new major technologies. But the innovation was not only at the product level, but one at the process itself. This was, according to the project manager, Wang Xiaojun, the first time the whole process was developed in digital 3D, using computer-aided design directly to computer-aided manufacturing.[8]

The inaugural flight was successfully performed on 25 June 2016, at 12:00 UTC from the Wenchang, LC-2 launch pad. It launched in the LM-7 configuration with enhanced by the also debuting Yuanzheng-1A stage, which performed its multi-orbit mission successfully.[9]

Design

The Long March 7 is the medium-lift variant of a new generation rocket family that includes the heavier-lift Long March 5 and the small-mid cargo Long March 6. The structure is based on the reliable, man-rated Long March 2F rocket. It inherited the 3.35 m-diameter core stage and 2.25 m-diameter liquid rocket boosters. Where the earlier Long March 2 rocket family used expensive and dangerous N
2O
4 / UDMH propellants, the Long March 7 uses LOX and kerosene. The engines are shared with the Long March 5 and 6. The goal was to build a more cost-effective and less hazardous rocket family to replace today's Long March 2 and eventually the Long March 3.[10] It will be capable of placing a 5,500 kilograms (12,100 lb) payload into a sun-synchronous orbit of 700 kilometres (430 mi).[11]

Stages

The Long March 7 inherits the modular stages of the original Long March 5 project. As such, its first stage is the same module as the LM-5 boosters. It also shares tank diameters and engines with the Long March 6, but the design groups were completely different. The LM-5 and LM-7 were developed by CALT, while the LM-6 was done by SAST. Even the avionics are different.[7]

The basic Long March 7 can be optimized by varying the number of boosters or enhanced by the addition of upper stages. These stages allow more mission flexibility, like direct injection to higher orbits or multiple orbit deployment. They can also increase the performance significantly. Thanks to this modularity, performance can be dialed between 4,000 kilograms (8,800 lb) and 13,500 kilograms (29,800 lb) for LEO, 2,000 kilograms (4,400 lb) and 8,000 kilograms (18,000 lb) for SSO and 4,000 kilograms (8,800 lb) and 7,000 kilograms (15,000 lb) to GTO.[12][13]

Boosters

The Long March 7 can use 0, 2 or 4 boosters using RP-1 / LOX propellant.[14] They are powered by a single oxidizer-rich staged combustion YF-100 engine. Each boosters supplies 1,200 kilonewtons (270,000 lb_f) at sea level and 1,340 kilonewtons (300,000 lb_f) in vacuum of thrust. Its specific impulse is 300 seconds (2.9 km/s) at sea level and 335 seconds (3.29 km/s) in vacuum. Each module has its own single axis thrust vector control, and thus it required a special design in the control systems of the rocket to coordinate all the rocket's nozzles.[11][14] They use the legacy 2.25 metres (7 ft 5 in) width of the Long March 2 and Long March 3 families, but due to the increased thrust of the YF-100 with respect to the YF-20 and YF-25, the boosters are almost twice as long, at 27 metres (89 ft).[14] A Long March 7 rocket booster created a fireball visible from portions of Utah, Nevada, Colorado, Idaho and California on the evening of 27 July 2016; its disintegration was widely reported on social media, and the uncontrolled re-entry of such a five-ton object was regarded as a rare event.[15]

First stage

The first stage has 3.35 metres (11.0 ft) diameter tanks carrying RP-1 / LOX propellant. It is powered by two YF-100 engines, sharing the same propulsion elements as the boosters, only that for the first stage the engines can gimbal in two axes.[14] Also, this first stage is the same basic module as the Long March 5 boosters. The diameter was designed for land transport and as such, it will be able to launch from all the Chinese launch sites. This is a critical difference to the LM-5 that requires water transport for its core stages.[11] While it shares diameter and engines with the Long March 6 first stage, the development was completely separated and done by different groups.[7]

Second stage

The second stage also shares the first 3.35 metres (11.0 ft) diameter tanks and propellant. It is powered by four oxidizer-rich staged combustion RP-1/LOX YF-115 engines. Two are fixed and two can gimbal in two axis.[14] It offers 706 kilonewtons (159,000 lb_f) of thrust in vacuum with a specific impulse of 341.5 seconds (3.349 km/s).[11] While it shares engines with the Long March 6 second stage, the development were completely separated and done by different groups.[7]

Optional stages

Yuanzheng-1A

It can use the Yuanzheng-1A upper stage to increase payload to higher energy orbits and enable multiple ignition missions. Particularly, allows direct injection to SSO orbits.[16] The inaugural flight successfully used this upper stage to deliver multiple payloads to different orbits.[12]

Hydrogen stage

The Long March 7 is expected to be enhanced by a high-energy liquid hydrogen and liquid oxygen stage. This stage and the low inclination of Wenchang would enable to launch payload between 4,000 kilograms (8,800 lb) and 7,000 kilograms (15,000 lb) to GTO orbit. That would be a 25% increase with respect to the previously most powerful Chinese launcher, the Long March 3B, but well below the Long March 5.[12] The Long March 7A variant, active since March 2020, accomplishes just this enhancement; it is made of the initial two stages of Long March 7, with a third stage powered by liquid hydrogen and liquid oxygen.

In the 2013 presentation of variations, a hydrogen-powered stage was also used as a second stage. It was not clear if it would be the same stage used as the second stage or a different stage. In both cases (second and third stage) they would be powered by the YF-75 or the YF-75D.[14]

Solid boosters

The 2013 presentation of the variation also proposed smaller 2 metres (6 ft 7 in) diameter solid boosters as a cheaper option for smaller payloads.[14]

Avionics

After the inaugural flight, Song Zhengyu, Deputy Chief Control Systems Designer for the Long March 7 project, stated that the flight had proven indigenous avionics. They had to work with the local industry to develop space rated dual processor PLCs. It was also stated that the real-time operating system was also an indigenous development. The general design was based on a distributed architecture to enable scalability and fault tolerance. This avionics would be the base for most future developments and had been designed with reusability in mind.[17]

2013 proposed variations

In a paper published on the Manned Spaceflight publication of the CMSEO, the Long March 7 was presented as a family of launch vehicles.[14] The variations would be codified by a two number plus variable letters code, and a CZ-7 prefix in the form CZ-7##. The first digit would mean the number of stages in the core, which could be either 2 or 3. The second number would mean the number of boosters, which could be 0, 2 or 4, with an S appended if the boosters were of solid type. There was also proposed an alternative second stage powered by the LH/LOX propellant and dual YF-75 engines would be identified by appending an (HO) to the designation. At last, it could have an additional upper stage, later identified as the Yuanzheng-1A, that would be identified by appending to the designation /SM.[14]

For example, the version that debuted was codified under this nomenclature as the CZ-724/SM, since it had two RP-1/LOX core stages, four liquid boosters and was enhanced by the Yuanzheng-1A stage. A CZ-720 would have two RP-1/LOX stages and no boosters. A CZ-724S(HO) would have a RP-1/LOX first stage, a LH/LOX second stage and four solid boosters. A CZ-732 would have two RP-1/LOX stages, a LH/LOX third stage, and two liquid boosters. The paper expected the following performance from certain versions.[14]

Version	LEO	SSO	GTO
CZ-720	2000 kg	–
CZ-722	7500 kg	1300 kg
CZ-724	13500 kg	5500 kg
CZ-720/SM		1000 kg
CZ-722/SM		4500 kg
CZ-724/SM		8500 kg
CZ-722S/SM		1800 kg
CZ-724S/SM		3900 kg
CZ-730			1200 kg
CZ-732			4500 kg
CZ-734			7000 kg
CZ-720(HO)	5500 kg	2900 kg	1500 kg
CZ-722S(HO)	7500 kg	4400 kg	2400 kg

The paper also presented the propulsion options for each stage. The RP-1/LOX second stage had only two YF-115 instead of the normal four, when used in the version with no boosters. It might have implied a different smaller upper stage or an under filled one.[14]

Version	Boosters	1st Stage	2nd Stage	3rd Stage	Maneuver Stage
CZ-720	0	YF-100×2	YF-115×2	/	/
CZ-722	2.25 m liquid×2	YF-100×2	YF-115×4	/	/
CZ-724	2.25 m liquid×4	YF-100×2	YF-115×4	/	/
CZ-720/SM	0	YF-100×2	YF-115×2	/	YF-50×1
CZ-722/SM	2.25 m liquid×2	YF-100×2	YF-115×4	/	YF-50×1
CZ-724/SM	2.25 m liquid×4	YF-100×2	YF-115×4	/	YF-50×1
CZ-722S/SM	2 m solid×2	YF-100×2	YF-115×4	/	YF-50×1
CZ-724S/SM	2 m solid×4	YF-100×2	YF-115×4	/	YF-50×1
CZ-720(HO)	0	YF-100×2	YF-75×2	/	/
CZ-722(HO)	2.25 m liquid×2	YF-100×2	YF-75×2	/	/
CZ-724(HO)	2.25 m liquid×4	YF-100×2	YF-75×2	/	/
CZ-722S(HO)	2 m solid×2	YF-100×2	YF-75×2	/	/
CZ-724S(HO)	2 m solid×4	YF-100×2	YF-75×2	/	/
CZ-730	0	YF-100×2	YF-115×2	YF-75×2	/
CZ-732	2.25 m liquid×2	YF-100×2	YF-115×4	YF-75×2	/
CZ-734	2.25 m liquid×4	YF-100×2	YF-115×4	YF-75×2	/

CZ-7A variant

Since 2020, the base two-stage CZ-7 configuration has been supplemented by the CZ-7A variant. The 7A variant employs the boosters and the first two stages of the base configuration, and add to this a third stage that employs two cryogenic YF-75 engines operating on LH₂ and LOX liquid fuels; the third stage of the 7A variant is inherited from the third stage of the Long March 3B. (Note that the 7A variant is similar to the CZ-73x variants first proposed in 2013; see previous subsection).

The maiden CZ-7A was launched on 16 March 2020 at 13:34 UTC from Wenchang Satellite Launch Center on Hainan island. Two hours after launch, state news sources announced that the flight ended in failure; no causes for the failure were indicated initially. Launch preparations for the maiden flight continued in the weeks prior to launch despite measures taken to combat the spread of the COVID-19 virus in China. Investigations into the failure of the maiden flight may or may not impact other Long March rocket variants depending upon the precise cause of the launch failure.[18]

List of launches

Main article: List of Long March launches

Flight number	Date (UTC)	Variant	Launch site	Upper stage	Payload	Orbit	Result	Notes	References
Y1	25 June 2016 12:00 [12]	7	Wenchang, LC-2	YZ-1A	Next-Generation Crew Capsule Scale Model Star of Aoxiang Aolong-1 Tiange-1 Tiange-2	LEO	Success		[19][20]
Y2	20 April 2017 11:41 [21]	7	Wenchang, LC-2	None	Tianzhou 1	LEO	Success		[22][23]
7A-Y1	16 March 2020 13:34	7A	Wenchang, LC-2	None	New Technology Verification Satellite-6	GTO	Failure		[3][24][25]

References

1. Jones, Andrew (16 February 2020). "China quietly rolls out new rocket to launch mystery satellite". spacenews.com. Retrieved 16 February 2020.
2. http://www.xinhuanet.com/english/2020-05/06/c_139033824.htm - 8 May 2020
3. Jones, Andrew (14 February 2020). "China prepares to launch new rockets as part of push to boost space program". space.com. Retrieved 14 February 2020.
4. "2016年，还有哪些航天大事值得期待？ | 科学人 | 果壳网 科技有意思" [What aerospace event to look for in 2016]. www.guokr.com (in Chinese). 3 March 2016. Retrieved 27 April 2016. 长征七号火箭原名长征二号F/H，最初可以看做长征二号F火箭换用YF-100和YF-115液氧煤油发动机的产物，但在实际研制中它应用了全数字化设计手段，代表了我国60年来运载火箭研制的最高水平
5. 8年历程 拓荒与先行 [The Eight Year Tale of Pioneer and Leading]. www.spacechina.com (in Chinese). 25 June 2016. Retrieved 27 June 2016.
6. 立项论证 平地起高楼 [Demonstration project launches]. www.spacechina.com (in Chinese). 25 June 2016. Retrieved 27 June 2016.
7. 突破运力"下限"的长征6号 [Advances in Light Capacity Long March 6] (in Chinese). Tencent Military Channel. 19 December 2013. Retrieved 3 August 2015.
8. 正式更名 迈出新一步 [Change of official name for a new step]. www.spacechina.com (in Chinese). 25 June 2016. Retrieved 27 June 2016.
9. Barbosa, Rui C. (25 June 2016). "China successfully debuts Long March 7 – Recovers capsule". Nasaspaceflight.com. Retrieved 2 July 2015.
10. SINA News Sina, 19 November 2010,
11. "Chang Zheng-7 (Long March-7)". SinoDefence. Retrieved 2 July 2015.
12. 长征七号首飞成功 空间实验室任务大幕拉开 [Successful maiden flight of the Long March 7 mission Damulakai]. www.spacechina.com (in Chinese). 25 June 2016. Retrieved 25 June 2016.
13. 未来，长征七号火箭将"挑大梁" [Long March 7 to play the leading role in the future]. www.calt.com (in Chinese). CALT. 28 June 2016. Retrieved 30 June 2016.
14. Fan, Ruixiang; Rong, Yi (2013). 代中型运载火箭的发展展望 [Our prospective next-generation medium launch vehicle development]. 载人航天 [Manned Spaceflight] (in Chinese). CMSEO. 2013 (2013, 01). doi:10.16329/j.cnki.zrht.2013.01.009. ISSN 1674-5825. Retrieved 30 June 2016.
15. Mike, Wall (28 July 2016). "Amazing Fireball Over Western US Caused by Chinese Space Junk". space.com. Retrieved 28 July 2016.
16. 长征七号搭载的缩比返回舱成功着陆 [Scaled down return capsule that launched by the Long March-7 has landed successfully]. www.xinhuanet.com (in Chinese). 27 June 2016. Retrieved 27 June 2016.
17. 控制系统多项"国产化"技术护航长七首飞成功 [Successful maiden flight of the Long March 7 demonstrate indigenous avionics]. www.cmse.gov.cn (in Chinese). CMSEO. 27 June 2016. Archived from the original on 14 September 2016. Retrieved 29 June 2016.
18. Jones, Andrew (16 March 2020). "Launch of China's new Long March 7A ends in failure". spacenews.com. Retrieved 16 March 2020.
19. CCTV13 (24 June 2016). "Long March 7 Maiden Flight – T – 1 minute to upper stage separation". Youtube (in Chinese). CNTV.
20. Kevin Anthony (27 July 2016). "ROCKET REENTRY – Lights up night sky! (Chang Zheng 7 Rocket)". Youtube.
21. Ping, Wu (June 2016). "China Manned Space Programme: Its Achievements and Future Developments" (PDF). China Manned Space Agency. Retrieved 28 June 2016.
22. Rui C. Barbosa (19 April 2017). "Tianzhou-1 – China launches and docks debut cargo resupply". NASAspaceflight.com.
23. "China's 'Heavenly Vessel' Sails into Orbit atop Long March 7 Rocket on Space Logistics Demonstration". Spaceflight 101. 20 April 2017.
24. "EPIC FAILURE: XJY-6 - CZ-7A (Y1) - WSLC - March 16, 2020 (13:34 UTC)". NASAspaceflight.com. 16 March 2020.
25. Barbosa, Rui (16 March 2020). "Long March 7A fails during Xinjishu Yanzheng-6 mission". NASASpaceFlight.com. Retrieved 16 March 2020.