China launched their experimental satellite Shijian-16-2 today from Jiuquan Satellite Launch Center. It is second Shijian-16 satellite-first was launched on October 25, 2013. It was 231st mission of Long March rocket.

Again CNSA surprised us with launch of the rocket; this time launch was performed with technology demonstrator satellite on atop. Only information about planned launch activity was NOTAM announcements regarding Jiuquan region air space. Launch was performed today at 03:21 GMT from platform 603 on Launch Site 43 in Jiuquan Satellite Launch Center. Shijian-16-2 was described by CNSA and Chinese media (Xinhua News Agency) shortly:

“Satellite was used for conducting spacial environment detection and technological experiments”

Launch and successful deployment of the satellite was confirmed by NORAD; satellite reached orbit with perigee at 595 km, apogee at 616 km and inclination at 75.01°.

Series of Shijian satellites date back to 1971, when first SJ-1 satellite was launched. Basically these satellites are usually designed especially for specific mission. First SJ satellites were equipped with different instruments for measuring radiation level, but most recent SJ satellites were testing electric propulsion (SJ-13) or were monitoring and tracking space debris (SJ-15). Few satellites were probably military early warning spacecrafts like SJ-11. First satellite from SJ-16 generation was launched on October 25, 2013 from Jiuquan Satellite Launch Center also on atop of Long March 4B. It was described as satellite for monitoring space radiation and various science experiments. Its orbit was almost identical as orbit of SJ-16-2: 599 × 616 km with inclination at 74.98°. In 2016 already one Shijian satellite was launched on April 5 with various experiments on microgravity. It was SJ-10 with special capsule with scientific payload (biological material), which returned to Earth on April 18, 2016.

Long March 4B rocket was designed by China Academy of Launch Vehicle Technology for LEO and SSO missions with possibility of lifting up to 4200 kg of payload (for LEO, for SSO it is 2800 kg). It remains in service since 1999. Its construction bases on three stages fueled with N2O4/UDMH; rocket is long for 45.8 m with diameter at 3.35 m and weighs 249200 kg. Comparing to Long March 4 it is equipped with fully digital avionics and longer payload fairing. First stage of the rocket is long for 24.65 m and is equipped with YF-21B engine generating thrust at 2971 kN. Second stage is long for 10.4 m and is equipped with YF-24C engine, which is basically combination of central YF-22C (thrust at 742.04 kN) and four stabilizing YF-23C (with thrust per engine at 47.1 kN). Third stage length is 2.9 m with single YF-40 engine providing thrust of 100.8 kN.