China is taking another significant step on the road towards a permanent presence in space, following the Long March 7 (TZ-1) launch of Tianzhou-1 – the first Chinese logistics cargo vehicle. The launch took place at 11:40:45 UTC on Thursday from the LC201 Launch Complex at the Wenchang Space Launch Center, followed by docking on Saturday
A successful mission for the Tianzhou-1 (TZ-1) vehicle will demonstrate China’s capability of cargo transport and refueling of an orbiting space station.
With a launch mass or nearly 13,000 kg, Tianzhou-1 is the heaviest cargo ever to be orbited by a Chinese launch vehicle.
The main objective of Tianzhou-1 mission is to conduct the on-orbit refueling of the Tiangong-2 space station.
During the mission, the new vehicle will make three rendezvous attempts with Tiangong-2. Combined operations with the Tiangong-2 / Tianzhou-1 orbital complex will take place over two months. At the end of this period, Tianzhou-1 will separate from Tiangong-2 and will initiate an autonomous orbital mission for three months to carry out experiments and tests during that period of time.
At the end of the mission, Tianzhou-1 will make an automatic destructive reentry into Earth’s atmosphere.
A cargo freighter for the future:
The Tianzhou (‘Heavenly Vessel’) cargo freighter has a payload capacity of 6,500 kg (including 2,000 kg of propellant), It has a length of 10.6 meters and a maximum diameter of 3.35 meters.
The new vehicle, developed on the basis of the Tiangong-1 space station, will be capable of executing fully automated rendezvous maneuvers and docking with Tiangong-2 and with the future modular Tiangong station.
Like the Russian Progress cargo vehicles, future crews and mission control will be able to override the approaching vehicle.
Transporting diverse cargo and fuel to the orbital outposts, Tianzhou will also be used to discard trash and execute autonomous missions after undocking. At the end of the mission, the vehicle will be discarded via a destructive reentry into the Earth’s atmosphere.
The second Tianzhou cargo vehicle is scheduled for launch in 2019, after the launch of the Tiangong space station core module (the Tianhe-1) using a Long March-5B rocket from Wenchang. The docking of Tianzhou-2 with the Tianhe-1 module will open the door for the launch of the Shenzhou-12 crew mission.
The Long March-7:
The development of the Chang Zheng-7 (CZ-7) (Long March-7 – LM-7) launch vehicle began in May 2010. It was originally designated Chang Zheng-2F/H (CZ-2F/H).
The new launcher is China’s new-generation medium-lift orbital launch vehicle developed by China Academy of Launch Vehicle Technology (CALT). The initial project was to be a modernized version of the CZ-2F to be used on the unmanned and manned flight missions in China’s “Manned Space Program”.
LM-7 will be mainly used for orbiting the new Tianzhou logistics cargo vehicle for the Tiangong-2 and to the modular Tiangong space station, but in the future, will replace the hypergolic launchers of the LM-2, LM-3 and LM-4 rocket range.
Initial flights of the new launch vehicle will be seen as test launches before achieving an operational capability when it will also be used for crewed launches.
The LM-7 is a two stage launch vehicle equipped with four strap-on boosters. Total length is 53.00 meters, diameter is 3.35 m and a span of 10.05 m, with a gross mass of 597,000 kg. At launch it develops a lift-off thrust of 7,200 kN. The rocket is capable of orbiting 13,500 kg into a 400 km LEO and 5,500 kg into a 700 km SSO.
Rocket components are transported to the launch site from the industrial city of Tianjin using two dedicated cargo ships, the Yuanwang-21 and the Yuanwang-22. The components are then offloaded at the Qinglan seaport serving the Wenchang Space Launch Centre.
The new rocket is powered by the newly developed YF-100, with the first stage using two engines and strap-on boosters using a single engine each. It includes the YF-115 on the second stage using four engines, using kerosene as fuel and liquid oxygen as oxidizer.
The development of the YF-100 began in 2000 at the Academy of Aerospace Liquid Propulsion Technology. The engine was certified by the State Administration of Science, Technology and Industry for National Defense (SASTIND) in May 2012.
It is a staged combustion cycle engine producing 1,199.19 kN at sea-level with a Isp of 2,942.0 N.s/kg (vacuum values are: thrust 1,339.48 kN; Isp 3,286.2 N.s/kg). The YF-100 will also be used on the CZ-5 and CZ-6 launch vehicles.
The YF-115 is it also a staged combustion cycle engine. It develops 176.5 kN in a vacuum.
Wenchang, China’s new space launch center:
Wenchang Space Launch Centre is located in the northeast corner of the Hainan Island on the southern coast of China.
The center is equipped with two launch complexes. Launch Complex LC101 is used for the Long March-5 launch vehicle family while Launch Complex LC201 is used for the Long March-7 launch vehicle.
Both pads are similar and are equipped with a fixed umbilical tower, underground flame deflector trenches and ducts. Similarly to what happens at the other Chinese launch centers, the umbilical towers have swing arms to allow technicians to access and inspect the launch vehicle and payload.
The launch pads are served by two vehicle assembly and integration buildings. Launch Complex LC101 is served by Building 501 while Launch Complex LC201 is served by Building 502. Each building is 99.4 meters tall permitting the assembly and testing of the launch vehicle in a full, vertical stacked position.
This is a new approach to the launch vehicle preparation for flight, because at the other Chinese launch centers the launchers are stacked and tested for flight at the launch platforms.
After being stacked at the vehicle assembly and integration building at the top of a mobile launch platform, the rocket is rolled to the launch pad.
The journey takes several minutes to cover the 2,800 meters separating the vehicle assembly and integration buildings, and the launch pads.
After arriving at the launch pads, the mobile structure is then placed above the flame trench and the necessary umbilical connections between the fixed structures and the mobile platform are established ahead of the flow to launch.
The new launch complex provides additional versatility that isn’t available at the other three launch sites. Wencheng also allows for an increase in performance for the launch vehicles gained from Earth’s rotational because is closer to the Earth equator. This reduces the amount of propellants required for the satellite’s maneuvers from the transit orbit to GEO.
Also, the launch vehicle can fly from the launch site to the southeast direction into the South Pacific, avoiding the possibility of rocket debris falling into any populated area – which has occurred during numerous Chinese launches.