Long March 7

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Long March 7[1][2]
Maquette Longue Marche 7 DSC 0004.jpg
Function Medium to heavy orbital launch vehicle
Manufacturer CALT
Country of origin China
Size
Height 53.10 m (174.2 ft)
Diameter 3.35 m (11.0 ft)
Mass 594,000 kg (1,310,000 lb)
Stages 2
Capacity
Payload to LEO (200km x 400km x 42°) 13,500 kg (29,800 lb)
Payload to SSO 700km 5,500 kg (12,100 lb)
Associated rockets
Family Long March
Comparable Delta IV, Atlas V, Falcon 9, H-IIA
Launch history
Status Active
Launch sites Wenchang LC-2
Total launches 1
Successes 1
First flight June 25, 2016
Boosters - K2 booster
No. boosters 4
Length 27 m (89 ft)
Diameter 2.25 m (7.4 ft)
Engines 1 YF-100
Thrust SL: 1,200 kN (270,000 lbf)
Vac: 1,340 kN (300,000 lbf)
Total thrust SL: 4,800 kN (1,100,000 lbf)
Vac: 5,360 kN (1,200,000 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 m (11.0 ft)
Engines 2 YF-100
Thrust SL: 2,400 kN (540,000 lbf)
Vac: 2,680 kN (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 m (11.0 ft)
Engines 4 YF-115
Thrust 706 kN (159,000 lbf)
Specific impulse 342 seconds (3.35 km/s)
Fuel RP-1/LOX
Third stage - Yuanzheng-1A(Optional)
Engines 1 YF-50D
Thrust 6.5 kN (1,500 lbf)
Specific impulse 315.5 seconds (3.094 km/s)
Fuel UDMH/N2O4

The Long March 7 (Chinese: 长征七号运载火箭), or Chang Zheng 7 as in pinyin, abbreviated LM-7 for export or CZ-7 within China, originally Long March 2F/H or Chang Zheng 2F/H, is a Chinese liquid-fuelled carrier rocket, developed by the China Aerospace Science and Technology Corporation.[3] It made its inaugural flight on June 25, 2016.

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 will initially be used to launch the Tianzhou robotic cargo spacecraft, and will eventually replace the Long March 2F as China's crew-rated launch vehicle.[3]

History[edit]

The Long March 7 project started in 2008 with the formation of the development team within the traditional designer of space launch vehicles, CALT.[4] 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.[5]

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.[5] 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.[6]

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.[7]

The inaugural flight was successfully performed on June 25, 2016 at 12:00hs 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.[8]

Design[edit]

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 N2O4/UDMH propellants, the Long March 7 uses LOX/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.[9] It will be capable of placing a 5,500-kilogram (12,100 lb) payload into a sun-synchronous orbit.[1]

Stages[edit]

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.[6]

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 t (4.4 tons) and 13.5 t (14.9 tons) for LEO, 2 t (2.2 tons) and 8 t (8.8 tons) for SSO and 4 t (4.4 tons) and 7 t (7.7 tons) to GTO.[10][11]

Boosters[edit]

The Long March 7 can use 0, 2 or 4 boosters using RP-1/LOX propellant.[12] They are powered by a single oxidizer-rich staged combustion YF-100 engine. Each boosters supplies 1,200 kN (270,000 lbf) at sea level and 1,340 kN (300,000 lbf) 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.[1][12] They use the legacy 2.25 m (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 m (89 ft).[12] A Long March 7 rocket booster created a fireball visible from portions of Utah, Nevada, Colorado, Idaho and California on the evening of July 27, 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.[13]

First Stage[edit]

The first stage has 3.35 m (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 axis.[12] 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 site. This is a critical difference to the LM-5 that requires water transport for its core stages.[1] While it shares diameter and engines with the Long March 6 first stage, the development were completely separated and done by different groups.[6]

Second Stage[edit]

The second stage also shares the first 3.35 m (11.0 ft) diameter tanks and propellant. It is powered by four oxidizer-rich staged combustion YF-115 engines. Two are fixed and two can gimbal in two axis.[12] It offers 706 kN (159,000 lbf) of thrust in vacuum with a specific impulse of 341.5 seconds (3.349 km/s).[1] While it shares engines with the Long March 6 second stage, the development were completely separated and done by different groups.[6]

Optional Stages[edit]

Yuanzheng-1A[edit]

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.[14] The inaugural flight successfully used this upper stage to deliver multiple payloads to different orbits.[10]

Hydrogen Stage[edit]

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 t (4.4 tons) and 7 t (7.7 tons) 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.[10]

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.[12]

Solid Boosters[edit]

The 2013 presentation of the variation also proposed smaller 2 m (6 ft 7 in) diameter solid boosters as a cheaper option for smaller payloads.[12]

Avionics[edit]

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.[15]

2013 Proposed Variations[edit]

In a paper published on the Manned Spaceflight publication of the CMSEO, the Long March 7 was presented as a family of launch vehicles.[12] 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.[12]

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.[12]

Version LEO SSO GTO
CZ-720 2 t (2.2 tons) -
CZ-722 7.5 t (8.3 tons) 1.3 t (1.4 tons)
CZ-724 13.5 t (14.9 tons) 5.5 t (6.1 tons)
CZ-720/SM 1.0 t (1.1 tons)
CZ-722/SM 4.5 t (5.0 tons)
CZ-724/SM 8.5 t (9.4 tons)
CZ-722S/SM 1.8 t (2.0 tons)
CZ-724S/SM 3.9 t (4.3 tons)
CZ-730 1.2 t (1.3 tons)
CZ-732 4.5 t (5.0 tons)
CZ-734 7 t (7.7 tons)
CZ-720(HO) 5.5 t (6.1 tons) 2.9 t (3.2 tons) 1.5 t (1.7 tons)
CZ-722S(HO) 7.5 t (8.3 tons) 4.4 t (4.9 tons) 2.4 t (2.6 tons)

The paper also presented the propulsion options for each stage. It is interesting to note that the RP-1/LOX second stage only had 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.[12]

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

List of Launches[edit]

Flight number Date (UTC) Launch site Upper stage Payload Orbit Result Footage
1 25 June 2016
12:00[10]
Wenchang LC-2 YZ-1A Next-Generation Crew Capsule Scale Model
Star of Aoxiang
Aolong-1
Tiange-1
Tiange-2
LEO Success Rocket Launch (Inaugural flight, from T-1 minute to upper stage separation)

Booster Reentry

2 2017 1st half[16] Wenchang LC-2 None Tianzhou 1 LEO

References[edit]

  1. ^ a b c d e "Chang Zheng-7 (Long March-7)". SinoDefence. Retrieved 2015-07-02. 
  2. ^ "长征七号运载火箭 (The Long March 7 Launch Vehicle)" (in Chinese). baike.com. Retrieved 2015-07-03. 
  3. ^ a b "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). 2016-03-03. Retrieved 2016-04-27. 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 
  4. ^ "8年历程 拓荒与先行" [The Eight Year Tale of Pioneer and Leading]. www.spacechina.com (in Chinese). 2016-06-25. Retrieved 2016-06-27. 
  5. ^ a b "立项论证 平地起高楼" [Demonstration project launches]. www.spacechina.com (in Chinese). 2016-06-25. Retrieved 2016-06-27. 
  6. ^ a b c d "突破运力"下限"的长征6号" [Advances in Light Capacity Long March 6] (in Chinese). Tencent Military Channel. 2013-12-19. Retrieved 2015-08-03. 
  7. ^ "正式更名 迈出新一步" [Change of official name for a new step]. www.spacechina.com (in Chinese). 2016-06-25. Retrieved 2016-06-27. 
  8. ^ Barbosa, Rui C. (2016-06-25). "China successfully debuts Long March 7 – Recovers capsule". Nasaspaceflight.com. Retrieved 2015-07-02. 
  9. ^ SINA News Sina, 19 November 2010, [1]
  10. ^ a b c d "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). 2016-06-25. Retrieved 2016-06-25. 
  11. ^ "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. 2016-06-28. Retrieved 2016-06-30. 
  12. ^ a b c d e f g h i j k 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 June 30, 2016. 
  13. ^ Mike, Wall (2016-07-28). "Amazing Fireball Over Western US Caused by Chinese Space Junk". space.com. Retrieved 2016-07-28. 
  14. ^ "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 sucessfully]. www.xinhuanet.com (in Chinese). 2016-06-27. Retrieved 2016-06-27. 
  15. ^ "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. 2016-06-27. Retrieved 2016-06-29. 
  16. ^ Ping, Wu (June 2016). "China Manned Space Programme: Its Achievements and Future Developments" (PDF). China Manned Space Agency. Retrieved 2016-06-28.