BEIJING -- China will accelerate research and commercial use of rocket upper stages, a carrier rocket official said on Friday.

"The Yuanzheng rocket upper stage family will have a new member, Yuanzheng-1S, this year, serving launches for low and medium Earth orbit satellites," said Wang Mingzhe, an upper stage architect of the China Academy of Launch Vehicle Technology (CALT).

Upper stages are independent aircraft installed on the carrier rocket that are capable of restarting their engines multiple times in space to allow them to send different payloads to varying orbits.

Earlier this month, China's Yuanzheng-1 rocket upper stage helped send two satellites into orbit on a single carrier rocket for its domestic BeiDou Navigation Satellite System in Xichang in southwest China's Sichuan Province.

China began to develop upper stage spacecraft in the 1980s, according to a report released by CALT. The first mission took place in March 2015 involving the Yuanzheng-1, which can perform two ignitions and operate for 6.5 hours.

Over the past three years, the Yuanzheng upper stage family has gained two members, Yuanzheng-1A and Yuanzheng-2, which are capable of up to 20 engine restarts and multiple spacecraft separation events.

"In addition to putting satellites into position, the Yuanzheng upper stage family is also able to monitor the space environment and send data back to Earth, which can help gain experience for future aircraft design," said Ye Chengmin, the vice chief architect for upper stages with CALT.

An upper stage is designed to operate at high altitude. Currently, China's three Yuanzheng upper stages all feature medium- and high-orbit missions.

Wang Mingzhe said there is growing demand for putting upper stages into commercial use, such as using them as launch vehicles to send small payloads into low and medium orbits. The new model Yuanzheng-1S will be a simplified version to cater to these needs.

"Compared with the long flight time of three other models, Yuanzheng-1S needs to finish its mission within one hour. This takes a lot of upgrading, such as streamlining systems to make this version more economical and efficient," said Wang.

Yuanzheng-1S is scheduled to be used for launches to Sun-synchronous orbits atop a Long March 2C carrier rocket in 2018.

Wang said that upper stages are expected to play a huge role in future moon and Mars exploration as well as orbital transfer and the clearing of space debris.