Interchangeable modularity is a central concept for China’s new family of space launchers. With initial versions of three rocket types now flying, the industry is moving on to widening the payload options with new combinations of propulsion modules.

A new type, Long March 8, will economize on development and production costs by using a major module of Long March 7, a founding member of the family. For the largest of the new types, Long March 5, a module will be omitted to make a version for building China’s planned space station.

Development of Long March 8 is aimed at low costs, says China’s main builder of space launchers, Calt. The rocket looks likely to begin the process of replacing the venerable Long March 2, 3 and 4 series. Long March 5 and 7 and their little sibling Long March 6 did not do so because they introduced new, not overlapping, payload capacities.

Long March 8 is designed to loft 7.6 metric tons (17,000 lb.) to low earth orbit, says Calt. Although a first flight in 2018 is possible, probably two years of development will be needed, says Lu Yu, director of Calt’s science and technology committee.

The rocket is closely comparable in performance to Long March 3A, which, like China’s other old launchers, uses hydrazine propellant, highly toxic stuff that is difficult to handle. Calt probably intends to use the new launcher to replace Long March 3A.

“We have basically completed preliminary development and are about to enter regular engineering design and production,” says Lu. “Progress will be much faster than it was for former types.”

One reason for that will be reuse of modules. The core first stage will be the kerosene-burning one from Long March 7, with two engines of the YF-100 type, a foundation of the new family. The second stage will be the hydrogen-fueled third stage of Long March 3A.

There will be two boosters, of a design based on but shorter than the first stage of Long March 11, a solid-propellant launcher that first flew in 2015. The Long March 11 motor is of 9 in. (2 meter) diameter and is subject to an improvement program (REFERENCE TO CHINASOLID).

The use of proven hardware already in production “can greatly reduce costs,” Lu said at the Global Space Exploration Conference held at Beijing on June 6–8.

Long March 8 will be able to carry 4.5 metric tons to a 435-mi. (700 km) solar-synchronous orbit, or 2.5 metric tons to geostationary transfer orbit (GTO), says Lu. Long March 3A can place 2.6 metric tons in GTO.

The second version of Long March 5 will fly in 2018, Lu says. Called Long March 5B, it dispenses with the second core stage of the original Long March 5. Throw weight to low Earth orbit will be 25 metric tons, compared with the capacity of the original version to deliver 14 metric tons to geostationary transfer orbit. 

It will be mainly used to launch the Chinese space station, Lu told the conference, which was organized by the Chinese Society of Astronautics and the International Astronautical Federation. Construction of the space station is supposed to begin next year.

But the deputy director of the military’s equipment development department, Zhang Yulin, said in March that Long March 5B was scheduled to fly in 2019, according to Xinhua news agency. The development of the new version has been mentioned for several years, though details have been lacking.

The first version is still called Long March 5, not Long March 5A. China’s most powerful space launcher, it will be used mainly for launching the country’s fifth and sixth lunar probes and for the second phase of the national navigation satellite program.

In keeping with its role of launching bulky space station modules, Long March 5B will have a 67.3-ft.-long payload fairing, compared with the 40.3 ft. of the first version. Calt has tested the operation of the new fairing at its new manufacturing base at Tianjin. Diameters of the fairing and core remain 17 and 16.4 ft., respectively.

Long March 5B will lift off with the same thrust as Long March 5, 10,565 kN (2,375,100 lb.), because the same engines are used: two YF-77s burning liquid hydrogen with liquid oxygen in the core and two YF-100s in each of four boosters. Those boosters are basically the same as the core first stages of Long March 7 and 8.

Despite the longer fairing, Long March 5B will be shorter than the first Long March 5 version – 176.05 ft., compared with 186.9 ft. – because of the omission of the hydrogen-fueled second stage. Judging from a low-resolution picture, the propellant tanks of the first stage have not been enlarged in Long March 5B. Liftoff weight will be 837 metric tons, down from 867 metric tons.

Calt has planned to build six versions in the Long March 5 series, varying the number of core stages and boosters.

Long March 11 is also a Calt product, but Long March 6, a liquid-propellant rocket using the YF-100, comes from a sibling organization, Sast. Both those launchers first flew in 2015, followed by Long March 5 and 7 in 2016.