Researchers working to extend rocket life spans

As China pushes forward its lunar and deep-space exploration programs, engineers are striving to improve the capabilities of rockets to better serve the nation's extraterrestrial aspirations.

One breakthrough by a Chinese engineer does not look fancy－it involves foam insulation－but it is expected to significantly extend a carrier rocket's service in space, enabling more distant missions or complex in-orbit operations.

Zhang Shaohua, a senior researcher of cryogenic rocket engine technology at the China Academy of Launch Vehicle Technology in Beijing, said on Friday that the program is intended to develop a cutting-edge solution to reduce the evaporation of fuels in cryogenic rocket engines.

Considered by engineers as a better option for rocket propulsion, cryogenic engines work at very low temperatures and use nontoxic and nonpolluting propellants such as liquid hydrogen and liquid oxygen. They have the best thrust efficiency among all existing rocket engines.

Such engines have been widely used in domestic and foreign carrier rockets, including China's Long March 5 and the United States' Delta IV.

"But this type of engine has one problem that restrains the rocket from extended missions－serious propellant evaporation caused by high temperatures during space flights," Zhang explained, saying that the current solution is to make big rockets that carry abundant amounts of fuel.

Once the new method his team is working on becomes mature and is put into use, Chinese designers will be able to build mightier rockets capable of flying farther or staying for longer periods in space without needing to make them bigger, he said.

Currently, rockets propelled by cryogenic engines can stay in orbit for at most several hours, the researcher said.

"Our new solution, if it is up to our goals, will extend the orbital period to at least five days, and in the long term, to as long as 30 days. That will allow us to carry out longer-duration space transportation or construct an in-orbit refueling station and will be very helpful for the nation's lunar and deep-space missions," he said.

The solution consists of three major technologies. The first is a new type of polyurethane foam that can increase the insulation capacity of the fuel container by more than 50 percent compared with traditional foam materials. The second, also a new-generation insulation method, uses multiple layers of variable density materials, promising at least an 18-percent increase in performance compared with existing technology. The third is an optimized method to control the loss of propellants during the engine's discharge of exhaust gases.

"We began research and development in 2010 and have conducted a great deal of ground-based experiments to verify the technology since then," Zhang said.

The experiments' results showed that with the new techniques, the daily evaporation of propellants in cryogenic engines can be cut from 2.5 percent to 0.5 percent, the researcher noted.

"Next we plan to ask for space authorities' support so we can have an opportunity to test it during launch missions."

zhaolei@chinadaily.com.cn