LONG MARCH 6 AND 7

Even as construction of the CZ-5 got under way, China astonished the space community when it announced in 2009 plans to develop a second new launcher, the Long March 6, and then a third, the Long March 7. Both were, by government decision in July 2008, allocated to the Shanghai Academy of Space Technology (SAST) in Shanghai to balance the development of the Long March 5 by CALT in Beijing. The first paper studies had been done by the 8th Research Institute as far back as 2000 and the idea was to have a lighter version of the CZ-5. In 2010, it was announced that the CZ-6 would be a “light” launcher with a payload of 10 tonnes and another new rocket, the CZ-7, would be a medium-lift launcher able to carry 10­20 tonnes. In effect, the CZ-5 would be the basis for a launcher family of small (CZ – 6), medium (CZ-7), and heavy lift (CZ-5) rockets using common modules and engines, rather like the Angara series in Russia. The approach of “launcher families” actually dated back to the Yangel design bureau in the Ukraine in the 1960s, where Mikhail Yangel conceived the idea of several versions of launchers using common components – the UR (Universalnaya Raketa or “universal rocket”). Maximizing commonality, the CZ-6 and CZ-7 will also use the new YF-100 engine. First flight dates have both been given ahead of the Long March 5 (2014-15), with the CZ-7 due in 2013 and the CZ-6 due in 2014. Lift-off mass will be 472 and 103 tonnes, while thrust will be 1,180 kN and 4,700 kN for the Long March 6 and 7, respectively.

The original strategy was for the Long March 6 to lift into orbit a weight greater than the CZ-2F, but less than the Long March 5, both stages having a single YF-100 engine. Over time, though, China began to lighten the CZ-6, shrinking it to a much smaller launcher able to lift a tonne to 700 km Sun-synchronous orbit, its two stages as small as 2.25 m but also serving as the strap-ons for the CZ-7. In appearance, it began to look more like Europe’s light launcher, the Vega, introduced in 2012.

The CZ-7 also went through a number of design evolutions. At the 2012 Asian Joint Conference on Propulsion and Power, held in Xian in March 2012, it was announced that its payload had been frozen at 13.5 tonnes to low Earth orbit and 5.5 tonnes to Sun-synchronous orbit. It would be the most powerful Chinese launcher pending the arrival of the Long March 5. According to Liang Xiaohong, deputy head of CALT, it would be used for cargo spacecraft for the space station. The rocket would have the following elements:

Core stage: two YF-100 engines, 120 tonnes each, diameter 3.35 m;

Strap-ons: four YF-100 engines, 120 tonnes each, all with diameter 2.25 m;

Second stage (H3): one 18-tonne-thrust engine, diameter 3 m.

In appearance, it will look not unlike the CZ-2E or 3B. At launch, six YF-lOOs will fire together, making a tremendous noise and generating up to 720 tonnes of thrust.