15 years after its concept was first conceived and 6 years after its development began, China’s CZ-6 (Chang Zheng-6, or Long March-6) orbital launcher finally made its maiden flight on 20 September 2015, marking the first major milestone in the development of China’s new-generation Chang Zheng launcher rockets.
The CZ-6 rocket was delivered to the Taiyuan Satellite Launch Centre (TSLC) in August 2015. The launch was originally scheduled for 07:00 CST on 19 September (18 September, 23:00 UTC). However, the launch was aborted at T minus 10 minutes due to a technical issue. 24 hours later, at 07:01 CST on 20 September (19 September, 23:01 UTC), the rocket finally lifted off, lofting a multi-payload of 20 micro- and nano-satellites into orbit.
Overview
The first all-new Chinese orbital launcher introduced in nearly two decades, the CZ-6 has been positioned as a small-load orbital launcher for small- and micro-satellites of under 1,000 kg mass, filling a launch capacity gap in the existing Chang Zheng launch vehicle family. This put the CZ-6 in the same class as the European Space Agency Vega and the Russian Angara-1.
China began the development of the new-generation Chang Zheng launchers in 2000. The most significant improvement over the current generation Chang Zheng rockets was the abandoning of the toxic N2O4/UDMH propellant in favour of the cleaner Liquid Oxygen (LOX)/Kerosene and LOX/LH2 propellents.
The CZ-6 is the first member of the new generation rocket family to fly. It is to be followed by two further models — the medium-load CZ-7 and the heavy-load CZ-5, which are due to make their maiden flights in 2016 and 2017 respectively. Together they will gradually replace the entire current generation Chang Zheng launchers including the CZ-2, CZ-3 and CZ-4 series over the next decade or so.
Original Concept
China’s new generation expandable space launcher rocket family was first announced in February 2001, followed by more detailed descriptions during the Zhuhai Air Show in late 2002. The original concept was to assemble launchers of various capabilities from three baseline rocket modules of 2.25 m, 3.35 m and 5.00 m diameter. These modules would be powered by either the 120 t thrust liquid engine YF-100 or the 50 t thrust liquid engine YF-77.
The smallest launcher of the family was to be based on the 2.25 m diameter module powered by a single YF-100 engine. Under the modular design principle, the same module could also serve as the strap-on booster for the medium- and heavy-load launchers.
The small-load launcher rocket was to be added with a LOX/LH2 upper-stage powered by a YF-73 engine derived from the CZ-3’s third-stage, giving a launch capability of up to 1,500 kg payload to the low Earth orbit (LEO), or up to 1,000 kg to the 700 km Sun Synchronous Orbit (SSO).
According to the calculations, a rocket 2.25 m in diameter would need to be around 35 m in length in order to carry enough propellant to achieve the intended payload capacity. At this length-to-diameter ratio the rocket would require extra enhancements in its structural strength and flight control. In addition, the rocket’s payload capacity to SSO would be limited to under 500 kg if the launch mission would only rely on land-based tracking stations within Chinese territory.
As an alternative, the design team produced an additional two proposals based on an enlarged first stage either 3.00 m or 3.35 m in diameter. Eventually a three-stage design with a 3.35 m diameter first-stage and 2.25 m diameter second- and third-stage (Design Proposal C) was chosen as the final design.
Development History
China Academy of Launch Vehicle Technology (CALT, or the 1st Academy) of China Aerospace Science & Technology Corporation (CASC) was originally leading the development of all new-generation Chang Zheng launcher rockets, but the CZ-6 development was reassigned to Shanghai Academy of Spaceflight Technology (SAST, or the 8th Academy) in July 2008.
The Chinese government officially authorised the CZ-6 development in 2009. SAST has since then introduced some further improvements to the rocket’s design, including thrust vectoring control on the rocket’s first-stage and self-pressurisation oxidiser tanks.
At the time when the CZ-6 development began, it had been nearly 20 years since China last introduced an all-new launcher rocket. SAST identified 12 key new technologies on the CZ-6, including three newly developed rocket engines (YF-100, YF-115, and the H2O2/Kerosene engine), a newly developed guidance, navigation and control (GNC) system, and a restartable third-stage.
Detailed design of the launcher was carried out by Shanghai Institute of Aerospace System Engineering (上海宇航系统工程研究所), or 805 Institute, a subsidiary of SAST. The rocket is fabricated at SAST-owned Shanghai General Factory of Aerospace Equipment Manufacturing (上海航天设备制造总厂), also known as 149 Factory.
The YF-100 rocket engine was certified by the State Administration of Science, Technology and Industry for National Defence (SASTIND) in early 2012. The first ground testing of the CZ-6’s first-stage was conducted successfully on 27 November 2012, followed by a second successful testing on 3 April 2013. The CZ-6’s second-stage had its ground testing in the first half of 2013, and the third-stage in July of the same year. The long-duration (500 seconds) ground testing of the YF-100 engine was conducted in August 2013.
At the same time, a new launch pad to support CZ-6 launch missions began construction at the Taiyuan Satellite Launch Centre (TSLC). Instead of an umbilical tower commonly seen in other Chinese launch complexes, the new launch pad featured only a simple umbilical structure providing gas, liquid and power supplies due to the rapid-launch capability of the CZ-6.
A non-flying example of the CZ-6 was delivered to the TSLC in late 2013 for an all-system launch campaign simulation. In December 2013 Chinese state-run media confirmed that the CZ-6 launch simulation had been completed, paving the way for the launcher’s maiden flight scheduled for 2014–15. However, it took another 20 months for SAST to fine-tune the rocket’s design, before the launcher was ready for its maiden flight.
Design Features
The whole launch vehicle has a gross launch mass of 103,217 kg and a dry mass of 9,020 kg. The 1,177 kN thrust YF-100 engine gives the rocket a thrust-to-weight ratio of 1.2. The overall length of the launcher is 29.237 m, significantly reducing its length-to-diameter ratio. The launcher has a maximum payload capacity of 1,080 kg to a 700 km SSO, or 500 kg if only Chinese domestic land-based tracking stations are used.
The first stage of the launcher is 3.35 m in diameter and is powered by a single YF-100 liquid engine burning the LOX/Kerosene bi-propellant. The stage carries 76,000 kg of propellants and has a burn time of 155 seconds.
The second stage is 2.25 m in diameter and is powered by a single YF-115 liquid engine also burning the LOX/Kerosene bi-propellant. The stage carries 15,000 kg of propellants.
The third-stage, also 2.25 m in diameter, is powered by four parallel 1,000 N-thrust liquid engines burning hydrogen peroxide (H2O2)/Kerosene bi-propellant. With a dual-way swinging nozzle and restart capability, these engines would also serve as the rocket’s reaction control system (RCS) thrusters during the ascent flight, an arrangement intended to simplify the launcher’s control system and improve its reliability.
The launcher could be fitted with two types of payload fairing, either 2.25 m or 2.60 m in diameter, in order to support different sizes of payload cargo.
Due to the relatively small size and structural weight, the rocket could be assembled at the rocket plant and then transported in one-piece on a wheeled transporter vehicle to the launch pad, where it is erected, checked, fuelled, and launched. The entire launch campaign would only take 7 days, in contrast to 30—40 days required by conventional Chang Zheng launchers.
CZ-6A
Even before the CZ-6 made its maiden flight, SAST had already begun the conceptual study of a drastically modified version known as CZ-6A (also referred to as CZ-8 by some sources). According to the PowerPoint presentation produced by SAST, the CZ-6A launcher would feature two 2.00 m diameter solid rocket strap-on boosters, a redesigned first-stage powered by two YF-100 engines, and a redesigned 3.35 m second-stage.
The new launcher would be capable of delivering up to 4,000 kg payload to the SSO, making it in the same class as the CZ-7 medium-load launcher currently being developed by CALT. The CZ-7 requires special fuelling equipment for its LOX/LH2 engines, which is only available at the Xichang or Hainan launch centre, whereas the CZ-6A could be launched from all four launch centres in China.
Some sources also suggested that the CZ-6A could be fitted with SAST’s TY-1 upper stage, which has multiple-satellite, multiple restart, and long-duration flight capabilities. This would enable the CZ-6A to support the launch of geostationary satellites and deep space probes.
