BEIJING, April 17 -- Chinese President Xi Jinpinghas offered condolences to the family of rocket scientist Liang Sili, who died of illness at the age of 91 in Beijing Thursday.

In his message, Xi deeply mourned the loss of Liang, who after the founding of New China, returned to the country and devoted himself tirelessly to China's aerospace program.

"He made important contributions to China's aerospace cause. His patriotism, dedication and rigorous scholarship deserve our respect," Xi said.

Liang was one of the founders of China's aerospace cause, and a renowned missile and rocket control expert. He was a member of both the Chinese Academy of Sciences and the International Academy of Astronautics.