China’s new medium-heavy space launcher, the Long March 7, should fly late next year, entering service in an initial version capable of lifting 13.5 metric tons (30,000 lb.) to low orbit, making it significantly larger than current Chinese rockets.

The Long March 7 will have four boosters, says the principal engineer of manufacturer CALT, Shen Lin, adding that China is also planning new upper stages and launch vehicles, some using solid propellants and others fueled with methane.

Speaking at the Asian Joint Conference on Propulsion and Power, held at Xian, China, on March 2-3, Shen confirms that the Long March 7 will use kerosene for fuel, which was expected, since its boosters and core first stage are to be driven by a new standard engine, the YF-100, which features 120 metric tons (265,000 lb.) thrust.

The YF-100 has staged combustion, Chinese industry officials say, referring to a challenging but efficient technology. The engine has achieved a 305-sec. specific impulse, a key measure of efficiency, they add. The 18-ton-thrust second-stage engine of Long March 7, which may be named YF-118 or YF-18, has been revealed as using staged combustion.

China has been working on engines burning methane (CH4) and liquid oxygen (LOx) since 2008, say senior Chinese space engineers Li Ping and Li Bin in a paper presented to the conference. “A pilot engine with 600-kn thrust (135,000 lb.) was [test-fired] to investigate the key technologies related with the reusable LOx-CH4 booster engines,” they say. This has been followed with development work on a 100-kn pilot upper-stage engine and several small-thrust reaction-control engines.

Hydrogen-fueled engines were adapted for the methane tests, another official says, adding that China has investigated liquefied petroleum gas as a fuel.

Long March 7 and its smaller sibling, the Long March 6, are overtaking the biggest member of China’s new rocket family, Long March 5, whose development began earlier. Long March 6 development is running behind that of Long March 7 by only a few months, if at all, says an official familiar with the programs. Long March 5 is introducing more technology than the two smaller rockets, notably a hydrogen first-stage core engine and a 5-meter (16.4-ft.) body dia.

The YF-100 also is the booster engine of the Long March 5 and the first-stage core engine of the Long March 6. Six YF-100s will propel Long March 7 — two in the core and one on each booster. Although this new family is eventually supposed to supplant the current launchers, all of which use toxic hydrazine fuel, the first version of Long March 7 will be considerably more powerful than any of the earlier rockets. The human-rated Long March 2F, for example, is capable of lofting 8.4 tons to low orbit, CALT says.

CALT, a subsidiary of national space conglomerate CASC, is developing Long March 5 and 7. The company drew up the preliminary design of the Long March 6, but CASC assigned the detail design and production of that small launcher to another subsidiary, SASC, officials say.

In the preliminary design, Long March 6 used the smallest of China’s three standard rocket body diameters, 2.25 meters, but SASC officials have said it will be built with the same 3.35-meter dia. as Long March 7.

The three diameters, variously matched with three engines, form a modular family. Long March 7 uses the 2.25-meter-dia. modules for its boosters. In a further important rationalization of the Chinese space effort, all of the new rockets will use a new launch base being built on Hainan Island, an official says.

The throw weight of Long March 7 will be varied by introducing the new upper stages that Shen mentioned, says an official familiar with the plans. That person says China can easily develop several different upper stages because it has quite a few engines of appropriate size, including hydrazine engines — even though the country’s policy is to get rid of toxic propellants.

No details were made available concerning the solid-propellant launchers, except that one official said they might deliver payloads of about 1 ton. The orbit for those satellites was not disclosed. But since Shen said they would be used to help deal with disasters, they would evidently be placed in polar orbits.

The solid-propellant rockets would be “responsive” launchers, meaning that they could be used at short notice. They appear to overlap in function with Long March 6, which has also been described as a fast-response rocket.

If China again pursues a modular design approach, then those proposed launchers would be closely related to a plan to fit solid-rocket boosters on Long March 5. Solid-propellant rockets are far less efficient than those using liquid propellant, but they are much cheaper to make.