China would develop two large new engines, including one sized for a Moon rocket, under an apparently official plan set out by senior engineers associated with the country’s space propulsion industry.

The proposed program would include re-engining the Long March 5 heavy launcher, which is still under development.

With no rocket engine developing more thrust than the 120-metric-ton (260,000-lb.) YF-100, China is still far behind other countries in space propulsion, researchers Li Ping and Li Bin have told the Asian Joint Conference on Propulsion and Power in a paper that must have had official backing from China’s main rocket-engine maker, the Academy of Aerospace Propulsion Technology (AAPT).

“The thrust requirement of future Chinese heavy or super-heavy launch vehicles is on the order of 4,000-7,000 kilonewtons [900,000-1,570,000 lb.],” the researchers say. The “super-heavy launcher” is evidently the proposed Chinese Moon rocket, research on which has been approved.

Such an engine would be a technical and economic challenge. Bigger engines are inherently harder to develop; and their production run tends to be short, because they have relatively few uses.

The proposed solution is to build the largest engine for which China has a viable commercial use, using familiar liquid oxygen (LOx) and kerosene propellant, and then to double it by mating two sets of combustion chambers and nozzles to a single set of bigger turbo pumps.

“Based on available technologies and test facilities in China, it is possible to develop a 2,000-3,500-kn-class LOx-kerosene engine with single chamber in [a] short time,” say Li Ping and Li Bin. This engine “can be applied to optimize the configuration of [the] CZ-5 launch vehicle to reduce engine number and to increase reliability. The second step is to develop the 4,000-7,000-kn-class heavy-thrust engine with double chambers with a heavy-power turbo pump.”

Chinese rocket builder CALT has said a Moon rocket would need 3,000 tons (about 30,000 kn or 6.7 million lb.) of thrust at liftoff. Given the demands of launching manned lunar spacecraft, that figure probably cannot be trimmed by much, if at all, so the proposed propulsion program implies that between five and eight engines would hurl the Moon rocket from its launch pad. They would presumably be distributed between side-mounted booster modules and a first-stage core. The first-stage core could use kerosene or hydrogen as a fuel, say Li Ping and Li Bin, but they make no proposal for developing a bigger engine using hydrogen. But oxygen and hydrogen would be used for the second-stage, they say.

The Long March 5 will be the largest Chinese space launcher when it goes into service, which will happen in 2014, according to an official schedule restated by CALT deputy chief Liang Xiaohong on March 3. With two core stages and four boosters, it has been designed to deliver 14 tons to geostationary transfer orbit, compared with the 5.5-ton capacity of the current Long March 3BE.

In its largest configuration, the Long March 5 will have four boosters each mounting two YF-100s, plus two hydrogen-fueled engines in the core. Having so many engines presents a relatively high risk of failure, depending on the rocket’s ability to continue after losing one, hence the proposal to substitute larger power plants. The new booster engine would be more than twice as big as the YF-100, however.

Li Ping is a senior official of the Xi’an Aerospace Propulsion Institute, part of the AAPT, which develops China’s liquid-fuel rocket engines. Li Bin is an associate professor at Northwestern Polytechnical University, another leading center of aerospace technology in China, also in Xi’an. Their paper can be taken as an official statement, since it also gives details of projects that would not be discussed without careful consideration by the authorities.

Asian Joint Conference on Propulsion and Power, a meeting of Chinese, Japanese and South Korean aerospace propulsion researchers, was held in Xi’an on March 2-3.