Shenzhou

Capsule-type, non-reusable spacecraft vehicle designed to carry up to three astronauts for a solo orbital flight of up to 7 days, or to ferry them to the space station and then return them to Earth. It can also be docked to the space station to serve as a ‘lift boat’.

Type: Crewed capsule vehicle. Crew size: 3. Programme: Project 921-I, Project 921-II, Project 921-III. Primary contractors: CAST/SAST. Status: Operational. First launch: 1999-11-20. Launch vehicle: CZ-2F. Launch site: Jiuquan-SLS1.

Programme

Launched atop the CZ-2F launch vehicle, the Shenzhou spacecraft was modelled after the Russian Soyuz-TM but slightly larger in size and has been developed mostly from Chinese technology. The spacecraft vehicle made its unmanned test flight in November 1999, and the first crewed flight in the Shenzhou 5 mission in October 2003. By the end of 2016 it had completed 11 orbital flights, including six crewed missions. The spacecraft vehicle is expected to remain in service until the 2020s, when it will be replaced by the new-generation multi-purpose crew vehicle currently in development.

Please see: Shenzhou Programme (Project 921)

Spacecraft Design

General Design

The Shenzhou is a modular assembly consisting of a forward cylindrical orbital module, an aerodynamic re-entry module, and an aft cylindrical service module with a pair of solar panel wings. A launch escape tower is attached to the front-end of the assembly and is jettisoned 2 minutes after the lift-off. The crew stays inside the habitable re-entry module during launch and re-entry and controls the spacecraft from there. The orbital module, which is also habitable, provides additional habitable space for the crew during orbital flight.

The spacecraft is launched atop the CZ-2F launch vehicle from Pad 921 (SLS-1) at the Jiuquan Satellite Launch Centre (JSLC), and operates in a 343 km near-circular orbit inclined at 42.5° to the Earth equator. It is capable of carrying up to three astronauts to fly in low Earth orbit (LEO) for up to 7 days in a solo flight mission. When the mission is completed, the orbital and service modules are discarded, while the heat-shield-protected re-entry module carrying the crew makes an unpowered ballistic descent through the atmosphere and then deploys parachutes and landing rockets for a soft-landing.

The spacecraft assembly is nearly 9 m in total length (excluding the launch escape tower), 2.5 m in diameter, with a gross launch mass of 8,130 kg and an orbital mass of 7,800 kg. It consists of 13 sub-systems: space frame, guidance navigation and control (GNC), data management, telemetry and communications, thermal control, propulsion, power, mission payload, environment control and life support system (ECLSS), crew, instruments and lightening, emergency rescue, and re-entry and landing. It is fitted with a total of 52 engines, including four main engines and 48 small-thrust control vectors (16 on the orbital module, 8 on the re-entry module, and 24 on the service module).

Orbital Module

The orbital module at the front of the spacecraft assembly is used to carry key equipment including a space toilet, and also provides additional habitable space for the crew to live and conduct scientific experiments during orbital flight. The module is 2.80 m in length, 2.25 m in diameter, with an internal volume of 8 cubic metres and an orbital mass of 1,500 kg. The module is connected to the re-entry module via a 65 cm diameter cylindrical hatch, which is sealed off during ascent, rendezvous docking, and re-entry. A large cylindrical hatch located on the side the module allows the crew to enter the spacecraft before launch, and can also be used for the astronauts to exit and re-enter the spacecraft during EVA. There is a third, smaller cylindrical hatch on the side of the orbital module in some early Shenzhou missions, possibly used as a window for Earth-observation payload.

For the early solo flight variant of the Shenzhou vehicle, the orbital module was fitted with its own independent altitude control, propulsion, telemetry and communication systems, as well as a second pair of smaller solar panel wings and 16 thrusters (in four groups of 4 thrusters). This design allowed the module to remain flying in orbit in an automated mode for another six months after being jettisoned from the re-entry module at the end of the manned mission.

Chinese spacecraft engineers originally envisioned to use the jettisoned orbital module as the target for the next Shenzhou spacecraft to practice orbital rendezvous and docking, but this idea was later abandoned. Instead, after the jettison the orbital module served as an orbital bus to carry scientific experiment or Earth-observation packages, with additional mission payload attached externally to the front of the module.

The Shenzhou 7 mission in 2008 featured a specially modified orbital module which doubled as an airlock and storage space for two EVA spacesuits. The spacewalking astronauts exited and returned to the spacecraft vehicle via the large cylindrical hatch on the side of the module, while the hatch connecting to the re-entry module remained sealed off throughout the EVA. This orbital module design lacked the automated orbital flight ability and was simply discarded and de-orbited at the end of mission.

From the Shenzhou 8 mission onwards, the Shenzhou spacecraft has been built in the crew transport configuration, which features an APAS-style docking port and an optical and radar-based automated rendezvous and docking system at the front end of its orbital module. Designed by SAST and believed to have been derived from the Russian APAS-89, the docking system features a single androgynous docking port, radio beacons, transponders, communication antenna, UHF radar, laser rangefinder, and electro-optical tracking system. The inside diameter of the docking port tunnel is 0.8 metre. During a rendezvous docking, the Shenzhou vehicle chases and closes in the space station though a V-bar approach from behind.

Re-entry Module

The re-entry module provides a fully pressurised and habitable living space for the crew during the ascent and re-entry phase of the flight. The module accommodates Soyuz-style moulded seats for up to three crew members, flight instrument panel, control sticker, periscope, and the communications system, with an internal volume of 8 cubic metres. There are two windows for the crew to observe the outside.

The module is fitted with eight (in four pairs) 5 N control engines, including 2 pitch/yaw thrusters, 2 translation thrusters, and 4 roll thrusters to maintain its flight status during re-entry.

During the descent stage of the flight, the re-entry module first makes an unpowered (but controlled) ballistic descent through the atmosphere, with its heat shield protected blunt end pointing forward. The module has a spherical aerodynamic design, with its centre of mass deliberately and precisely offset from its axis of symmetry to achieve an angle of attack during the free fall. This allows the yield of a small lift to reduce g-force from 8—9 g for a purely ballistic trajectory to 4—5 g during the hypersonic free-fall, as well as greatly reducing the peak re-entry heat. In an emergency situation, the module can also re-entry using a purely ballistic trajectory, which would increase the g-force to 8—9 g. If necessary, the module can splashdown on water and then remain afloat.

The re-entry module is fitted with five parachutes: a pilot chute (4.25 m2 surface area), a second pilot chute (surface area: 0.7 m2), a drogue chute (surface area: 24 m2), a main parachute (surface area: 1,200 m2), and a backup parachute (surface area: 760 m2). The parachutes are deployed from the altitude of 10,000 m.

The 280 kg heat shield is jettisoned before landing so that the four landing rockets at the bottom of the module could fire to allow a soft-landing.

Service Module

The inhabitable service module is larger than that of the Soyuz-TM. It accommodates the navigation, communications, flight control, thermal control, propulsion systems, as well as batteries, oxygen tanks, and propellant tanks. It has a pair of adjustable solar panel wings 17 m in span to obtain maximum solar insulation regardless of the spacecraft’s flight status.

The propulsion system consists of four high-thrust main engines and 24 smaller-thrust control vectors, plus four 230-litre propellant tanks containing a total of 1,000 kg N2O4/MMH liquid propellant. The four main engines, each rated at 2.5 kN, are located at the base of the spacecraft’s service module. There are eight (in four pairs) 150 N pitch/yaw thrusters, eight (in four pairs) 5 N pitch/yaw thrusters, and eight (in four pairs) 5 N roll / translation thrusters.

Launch Escape System

The launch escape assembly incorporates the launch escape tower, the orbital module, the descent module, the upper portion of the payload fairing and four foldable grid aerodynamic flaps. In case of an anomaly during the launch, the assembly with the crew can be pulled away from the remainder of the launch vehicle within seconds, by rockets mounted on the launch escape tower above the payload fairing. The whole assembly is 15.1 m in length and 3.8 m in diameter, and has a total mass of 11,260 kg. It is powered by the solid fuel rocket motors mounted on the launch escape tower and payload fairing. The two-piece payload fairing is also equipped with rocket motors for high-altitude escape.

The launch escape tower is 8.35 m in length and fitted with six rocket motors: four main escape motors, a pitch motor and a separation motor with eight nuzzles. The main four main escape motors are mounted symmetrically on the lower part of the launch escape tower at an angle of 30° to the axis of the launch vehicle. Above them are eight smaller separation motors. The pitch motors are mounted at the top of the tower.

Environmental Control and Life Support System

The Environmental Control and Life Support System (ECLSS) ensures a habitable and safe environment for the onboard crew throughout the flight mission. It consists of the environment control system, oxygen and other gases storage tanks, water supply and processing system, astronaut waste disposal and collection system (‘space toilet’), fire/smoke detectors, and fire suppression system. During the flight mission, every day a typical crew member consumes 0.83 kg oxygen and 1.8 litre of water, and produces 0.9 kg carbon dioxide.

The Shenzhou vehicle can create and maintain an inside atmosphere similar to that on Earth, with conventional air (nitrogen/oxygen). A liquid-circulating temperature control unit maintains the temperature inside the habitable modules between 17—25°C. Air dampness is maintained between 30—70%. An air ventilation and purification system detects and absorbs dusts, carbon dioxide and carbon monoxide.

The Shenzhou orbital module is fitted with a space toilet, which uses a vacuum system to collect human waste of the onboard crew. A food heater can provide the crew with hot meals during the flight. The crew is required to wear the intra-vehicular activity pressure suits during launch, docking, undocking and descent. The suit, which was based on the Russian Sokol design, can protect the crew members in the event of hull breach or pressure loss.

Mission Profile

Launch

The launch campaign of a Shenzhou flight mission begins approximately two months prior to the launch date. The Shenzhou vehicle is airlifted in climate-controlled containers onboard a military cargo plane from its fabrication facility in the Beijing Space City to Dingxin Airbase 76 km southwest of the launch centre, and then transported by road to the spacecraft assembly facility in the technical area of the launch centre. The vehicle is first assembled and tested in the Spacecraft Non-Hazardous Operation Building, before being transferred to the Spacecraft Hazardous Operation Building for fuelling.

Once the Shenzhou vehicle is assembled and tested, it is moved to the Launch Vehicle Vertical Processing Building to be integrated with the launcher rocket, the launch escape tower, and the payload fairing. 3—5 days prior to launch, the CZ-2F/Shenzhou launch vehicle stack is rolled out in a vertical position atop the mobile launcher platform from the vehicle processing building to the launch pad, where the final inspections and alignments of the launch vehicle and the launch rehearsal are conducted. Fuelling of the launch vehicle begins 24 hours prior to launch and takes 6—7 hours to complete.

T minus 1 hour 30 minutes

The mission crew enters the Shenzhou spacecraft on the launch pad. They access the spacecraft at the top of the launch vehicle stack through a lift inside the umbilical tower. They first enter the spacecraft’s orbital module via a large hatch on the launcher rocket’s payload fairing and then a large hatch on the side of the module. They then descend to the re-entry module below via a second hatch connecting the two modules. They then strap themselves onto the moulded seats inside the re-entry module, and remain in that position throughout the countdown.

T minus 45 minutes

The rotating platform and support arms of the umbilical tower are swung opened.

T minus 15 minutes

All ground crews evacuate the launch pad area.

T minus 2 minutes

The launch vehicle switches to internal power.

T minus 0 seconds

Launch vehicle ignites its engines and lifts off.

T plus 10 seconds

Launch vehicle makes the roll programme (tilt manoeuvre) to fly downrange.

T plus 2 minutes

The launch escape tower is jettisoned.

T plus 2 minutes, 20 seconds

The four strap-on boosters of the launch vehicle are jettisoned.

T plus 2 minutes, 40 seconds

Main engine cut-off, first-stage jettison, and second-stage ignition.

T plus 3 minutes, 20 seconds

The two-piece payload fairing is jettisoned.

T plus 7 minutes, 41 seconds

The second-stage main engine cut-off.

T plus 9 minutes, 40 seconds

Second-stage swivelling motor cut-off. The spacecraft reaches 7.5 km/sec velocity.

T plus 9 minutes, 43 seconds

The second-stage of the launch vehicle is separated and the spacecraft vehicle enters a 200 x 350 km parking orbit.

Should an emergency occur during the launch and ascent stage which results in mission abort, a number of escape procedures have been designed to ensure the safe return of the crew. From the astronauts entering the spacecraft to 30 minutes prior to the launch, the crew can exit the launch pad via an explosion-proof elevator, or a canvas slide that leads to an underground shelter beneath the umbilical tower.

The spacecraft’s launch escape system is activated at 30 minutes prior to launch. Fitted with five sets of solid rockets, the launch escape tower can pull the orbital and re-entry modules of the spacecraft away from the launch vehicle in case of anomaly on the launch pad or during the initial ascend phase, and return the crew by parachute to one of the four emergency landing zones in Chinese territory. The system can be triggered either automatically by the onboard computer, or manually by the ground or spacecraft commander. The system remains active until T plus 120 seconds (39,000 m altitude), at which point the launch escape tower is jettisoned.

From 120 seconds to 200 seconds into the launch, the orbital and re-entry module of the spacecraft can still be pulled away from the launch vehicle by the payload fairing, which is also equipped with solid rockets. The escape procedure would be similar to that using the launch escape tower. After the payload fairing is jettisoned at T plus 200 seconds, the spacecraft can be separated from the second-stage of the launch vehicle in case of emergency, before proceeding with the landing procedure under the command of either the crew or ground mission control.

There are four inland emergency landing zones located at the east of the Jiuquan Satellite Launch Centre, Yinchuan in the Ningxia Autonomous Region, Yunlin in Shaanxi Province, and Handan in Hebei Province. During the launch phase, three sea landing zones are also established in the West Pacific over a range of 5,200 km, with naval warships and rescue vessels in standby nearby for a search and rescue mission.

Recovery

The recovery is normally carried out in early morning or late evening, so that the re-entry capsule is illuminated by the sun while it descends from high altitude, creating a strong contrast to the dark night sky in the background. This helps the optical tracking of the capsule by the ground stations. While it takes the launch vehicle just under 10 minutes from launch pad lift-off to orbit insertion, the journey to return to Earth takes about 46 minutes, over a distance of 12,960 km.

The re-entry trajectory data is transmitted to the Shenzhou spacecraft during the final orbit by one of the ground tracking stations or instrumentation ships. Prior to the re-entry sequence, the crew returns inside the re-entry module, seals off the hatch to the orbital module, don their pressure suits and helmets, and strap themselves onto the moulded seats ready for the re-entry. The command for initiating the re-entry sequence is sent to the spacecraft via uplink by a Yuanwang instrumentation ship stationed in the South Atlantic off the African coast.

T minus 47 minutes

The re-entry sequence begins with the firing of the spacecraft’s manoeuvring thrusters to turn the spacecraft vehicle 90° in the azimuth direction. The unoccupied orbital module is then separated from the remainder of the spacecraft and burns up upon re-entry into the atmosphere.

The spacecraft then makes another 90° turn in the azimuth direction, so that it travels in a ‘backside first’ position, with its main engine pointing forward towards its orbital motion direction. The final manoeuvre involves the spacecraft raising its backside slightly to create an angle between the spacecraft axis and its motion direction.

T minus 45 minutes

The spacecraft fires its main engines for a two-minute de-orbit burn, reducing the spacecraft’s velocity by about 100 m/sec to allow it to enter the re-entry trajectory. The retrofire occurs over Southern Africa, while the spacecraft is monitored by the Yuanwang instrumentation ship off the West African coast and the Chinese ground tracking station in Swakopmund, Namibia. The two stations are also responsible for confirming that the spacecraft has entered the correct re-entry trajectory after the retrofire burn.

T minus 35 minutes

The spacecraft left the sight of the Swakopmund tracking station and enters the sight of the ESA ground tracking station in Malindi, Kenya.

T minus 25 minutes

The spacecraft enters the sight of the Chinese ground tracking station in Karachi, Pakistan. The service module of the spacecraft is jettisoned at altitude of 140 km, while the re-entry module continues its descent to Earth.

T minus 22 minutes

The re-entry capsule enters the sight of the space tracking station in Heitian, Xinjiang in Chinese territory. At an altitude of 120 km, the capsule makes final manoeuvres to create an angle of attack, so that a small amount of lift can be generated in the atmosphere by its “headlight” shape. This allows the capsule to carry out a controlled ballistic descent, reducing the G-force to a bearable 4—5 g.

Between the altitudes of 80—40 km, the re-entry capsule encounters more significant air density in the lower thermosphere at a speed of 8 km/s. The capsule performs a series of S-bend manoeuvres under automatic control to help it lose speed more quickly. Friction from Earth’s thickening atmosphere heats the capsule’s outer surface to 1,500—2,000°C. Temperature within the capsule is generally controlled at between 17—25°C, but could reach 40°C for a short period of time.

The radio communications between the re-entry capsule and ground is temporarily broken up due to the re-entry blackout, which lasts 360—370 seconds. However, the plasma envelope around the capsule’s surface created by the re-entry heat allows it to be tracked by the forward radar station in Guazhou (Anxi), Gansu Province.

At this point, the jettisoned service module breaks up while it enters the dense atmosphere. This occurs while the re-entry capsule passes over the Jiuquan Satellite Launch Centre. The breakup of the service module is monitored by the optical tracking station near the launch centre. The re-entry capsule continues its descent, passing over the secondary landing zone east of the Jiuquan launch centre at an altitude of 50 km. Its trail is tracked by the thermal imaging equipment at the landing zone.

T minus 15 minutes

The main landing site’s forward target acquisition radar located in Bayan Obo, Inner Mongolia captures the re-entry capsule in descent (50 km altitude) and transfers the capsule’s trajectory data to the measurement station in Damiao, Inner Mongolia.

At below 40 km altitude, the communications blackout ends and the re-entry capsule switches on its 243 MHz MF radio beacon to help the search and rescue teams locate itself.

T minus 13 minutes

The unified S-band (USB) tracking radar at the main measurement station in Damiao, Inner Mongolia captures the re-entry capsule at an altitude of 30 km and a speed of 1.9 km/s. The station sends a command to the capsule to initiate the landing sequence. The station also calculates the coordinates of the projected landing position and directs the air and ground search and rescue teams to the position.

T minus 11 minutes

The 3.2 metric tonne re-entry capsule deploys its parachutes at an altitude of 10,000 m and a speed of 200 m/s. It deploys its first pilot chute, followed by a second pilot chute. A drogue chute attached to the second pilot chute is then deployed to reduce the speed of the capsule from 180 m/s to 80 m/s. After 16 seconds, the drogue chute is separated from the capsule and the main parachute is deployed at the altitude of 8,000 m.

While the capsule descents from 6,000 m and 5,000 m altitude, its onboard landing system judges the effectiveness of the main parachute by measuring the capsule’s rate of descent. If the re-entry capsule takes less than 55 seconds to complete this descent, the system would deem a failure in the main parachute and trigger the deployment of the backup parachute.

The 280 kg heat-shield on the bottom of the craft is jettisoned at an altitude of 6,000 m. A second medium-frequency (20 MHz) radio beacon attached to the main parachute is turned on, giving direction to the ground rescue team. The radio communications with ground control is also resumed. At the same time, the harnesses of the main parachute shift the vehicle’s attitude to a 30-degree angle relative to the ground, dissipating heat, and then shift it again to a straight vertical descent prior to landing. The descending rate of the capsule is maintained at 10 m/s.

The astronaut seats are elevated into the landing position at 20 seconds after the jettison of the heat shield.

T minus 10 seconds

At about 10 metres above the ground, the indicator on the flight instrument panel inside the re-entry capsule is lightened to warn the crew that the touchdown is imminent.

T minus 2 seconds

At 1 metre above the ground, the re-entry capsule fires the four landing rockets at the bottom to reduce the descent rate to 2—5.5 m/s before touching down.

T minus 0 second

The re-entry capsule touches down. Immediately after ground contact, the parachute cords are cut to avoid wind disturbance. The strobe light on the capsule is switched on, flashing at a frequency of 55 times per minute to help the search and rescue teams locate it at night. The light can work continuously for up to 25 hours.

The spacecraft crew remains inside the re-entry capsule until the arrival of the rescue teams. After examining the capsule from outside, the rescue crews open the hatch on the re-entry capsule and help the astronauts to exit the capsule. The astronauts are briefly examined by medical staffs on site, before being airlifted by helicopter to a nearby airport, where an air force passenger jet is on standby to transport them back to Beijing.

If the weather conditions at the primary landing zone in Siziwang Banner cannot meet the minimum requirements for a safe landing (high-altitude wind speed <70 m/s; low-altitude wind speed < 15 m/s; snow thickness < 0.5 m; visibility > 10 km), the Shenzhou spacecraft can chose to land at the backup landing site east of the Jiuquan Satellite Launch Centre.

In an emergency scenario, a Shenzhou capsule can also land in one of the 10 emergency landing zones within Chinese territories and overseas, or making a splashdown in the sea. Shenzhou crews are equipped with survival kits including first aid kit, flashlight, food, and weapons in case they land in remote regions.

Specifications

Orbit:.................300—400 km LEO, 42.5º inclination
Mass, Gross (kg):......8,130
Mass, Orbital (kg):....7,800
Propellants:...........N2O4/UDMH

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