Luo, 51, on-site director-in-chief of China's carrier-borne fighter jet J-15, suffered a heart attack Sunday onboard the retrofitted aircraft carrier "Liaoning" just after the successful landing of the jet on the deck of the carrier, and later died in hospital, the official Chinese media reported.
In his condolence message to Luo's family, Xi, who will succeed President Hu Jintao in March after becoming China's top leader during the leadership transition earlier this month, said the scientist's death was unexpected and is a "big loss to the (Communist) Party as well as to the nation," the Xinhua News Agency reported.
Xi, who has also become chairman of the party's powerful Central Military Commission, said Luo devoted himself to the country's aviation industry and made an extraordinary contribution to its development.
Luo, chairman and general manager of the Shenyang Aircraft Corp., headed the manufacturing and production phase of the J-15 fighter jet.
The J-15 was described as being capable of firing anti-ship, air-to-air and air-to-ground missiles and precision guided bombs, and Xinhua quoted military experts as saying they believe the jet's capabilities are comparable to Russia's Sukhoi Su-33 and the U.S. F/A-18 Hornet.
The aircraft carrier was originally built in 1988 by the Soviet Union, and China bought it from Ukraine, a former Soviet state, in 1998. The vessel formally entered into China's service Sept. 25, after its crew completed more than 100 training and test programs, Xinhua said.
Luo reportedly had been under mental pressure as he sought to accomplish the deck landing of the J-15.
China Daily quoted Luo's teachers and classmates at college as saying he studied hard and his colleagues respected him because he had devoted all his life to his work.
China Central Television CCTV quoted company sources as saying Luo had felt unwell on the carrier but carried on with his work.
"After Luo left the Liaoning, Xie Genhua, our corporation's Party chief, went to receive him and found he did not look well. Luo then returned to the hotel and in his suite, had a sudden heart seizure," Wang Enfu, union head at Shenyang, told China Daily.
"A driver and a local guide rushed him to the hospital, but he could not hold on, even though the car was only a few hundred meters away from the hospital."
"The tragedy happened all of a sudden, we could never have anticipated it," company general manager Liu Yongtao said.
Liu was quoted as saying Luo made his final call to his wife Saturday, telling her he was pleased that all test missions had been completed.