Soyuz (Soyus, Союз, union) is a series of spacecraft designed by Sergey Korolev for the Soviet Union's space program. The Soyuz succeeded the Voskhod spacecraft design and were originally built as part of the Luna program. The spacecraft are launched by the Soyuz launch vehicle, as part of the Soyuz program and the later missions of the Zond program. They were later used to carry cosmonauts to and from the Salyut and Mir space stations and are now used for transport to and from the International Space Station. The first unmanned launch of the Soyuz was on November 28, 1966. The first manned launch of the Soyuz was on April 23, 1967.
Spacecraft design Edit
A Soyuz spacecraft consists of three parts. From front to back, a roughly spherical orbital module, a small smooth reentry module, and a cylindrical service module with solar panels attached. The first two portions are habitable living space. By moving as much as possible into the orbital module, which does not have to be shielded or decelerated during atmospheric reentry, the Soyuz is both larger and lighter than the Apollo spacecraft's command module. The Apollo command module had 6 cubic meters of living space and a mass of 5000 kg; the 3-part Soyuz provided the same crew with 9 cubic meters of living space, an airlock, and the service module for the mass of the Apollo capsule alone.
Soyuz can carry up to three cosmonauts and provide life support for them for up to 3.2 days. The life support system provides a nitrogen/oxygen atmosphere at sea level partial pressures. The atmosphere is regenerated through KO2 cylinders which absorbs most of the CO2 and water produced by the crew and regenerates the oxygen, and LiOH cylinders which absorb leftover CO2.
The vehicle is protected during launch by a nose fairing, which is jettisoned after passing through the atmosphere. It has an automatic docking system. The ship can be operated automatically, or by a pilot independently of ground control.
The forepart of the spacecraft is the orbital module. It houses all the equipment that will not be needed for reentry, such as experiments, cameras or cargo. It also contains the docking port and can be isolated from the descent module to act as an airlock if needed. This separation also lets the orbital module be customized to the mission with less risk to the life-critical descent module.
The descent module is used for launch and the journey back to Earth. It is covered by a heat-resistant covering to protect it during re-entry. It is slowed initially by the atmosphere, then by a braking parachute, followed by the main parachute which slows the craft for landing. At 1 metre above the ground, solid-fuel braking engines mounted behind the heat shield are fired to give a soft landing. One of the design requirements for the reentry module was for it to have the highest possible volumetric efficiency (internal volume divided by hull area). The best shape for this is a sphere, but such a shape can provide no lift, which results in a purely ballistic reentry. Ballistic reentries are hard on the occupants due to high deceleration and can't be steered beyond their initial deorbit burn. That is why it was decided to go with the 'headlight' shape that the Soyuz uses - a hemispherical forward area joined by a barely angled cone (7 degrees) to a classic spherical section heat shield. This shape allows a small amount of lift to be generated due to the unequal weight distribution. The nickname was thought up at a time when nearly every headlight was circular.
At the back of the vehicle is the service module. It has a pressurized container shaped like a bulging can that contains systems for temperature control, electric power supply, long-range radio communications, radio telemetry, instruments for orientation and control. A non-pressurized part of the service module contains the main engine and a spare: liquid-fuel propulsion systems for maneuvering in orbit and initiating the descent back to Earth. The ship also has a system of low-thrust engines for orientation. Outside the service module are the sensors for the orientation system and the solar array, which is oriented towards the sun by rotating the ship.
The many incarnations of the Soyuz Edit
The first manned version of the Soyuz was called 7K-OK. It could support up to three crewmembers in a shirt-sleeve environment. Although it could feature a docking fixture, this was passive and only allowed the two spacecraft to be joined, with no facility for internal transfer. Cosmonauts had to spacewalk to the other spacecraft, as done on Soyuz 4 and 5. This spacecraft was also designed to fly to the moon.
The 7K-L1 was designed to launch men from the Earth to circle the moon. It was based on the 7K-OK with several components stripped out to reduce the vehicle weight. The most notable modifications included the removal of the orbital module (extra space for living quarters or equipment) and reserve parachute. It was the primary hope for Soviet circumlunar flight. Tests in the Zond program from 1968-1970 produced multiple failures in the 7K-L1's re-entry systems. The goal was scrapped, along with the two remaining 7K-L1s.
The next manned version of the Soyuz was the 7K-OKS. This was designed for space station flights and now had a docking port that allowed internal transfer between spacecraft. It flew only twice manned. During the reentry of the second flight, Soyuz 11, the crew were killed when the capsule depressurised during the re-entry phase.
The complete redesign that resulted led to the 7K-T. It deleted one crew space so that all cosmonauts could wear spacesuits during launch and reentry. The replacement of solar panels with batteries limited it to about two days of undocked flight.
A modified version of this spacecraft flew on Soyuz 13 where instead of the docking system was a large Orion 2 astrophysical camera for imaging the sky and Earth.
Another modification was the 7K-T/A9 used for the flights to the military Almaz space station. This featured the ability for remote control of the space station and a new parachute system but other than that the changes are still classified and unknown.
The Soyuz ASTP spacecraft was designed for use during the Apollo Soyuz Test Project. It featured design changes mandated by the Americans to make the spacecraft safer. The Soyuz ASTP featured new solar panels for increased mission length, an androgynous universal docking mechanism instead of the standard male mechanism and modifications to the environmental control system to lower the cabin pressure to 0.68 atmospheres (69 kPa) prior to docking with Apollo. The last flight of this version, Soyuz 22 again replaced the docking port with a camera.
The next major redesign was the Soyuz T version. It featured solar panels allowing longer missions, a revised Igla rendezvous system and new translation/attitude thruster system on the Service module.
The Soyuz TM crew transports were introduced in 1986 to service the Mir space station. It added to the Soyuz T new docking and rendezvous, radio communications, emergency and integrated parachute/landing engine systems. The new Kurs rendezvous and docking system permitted the Soyuz TM to maneuver independently of the station, without the station making "mirror image" maneuvers to match unwanted translations introduced by earlier models' aft-mounted attitude control.
A slightly modified Soyuz TMA is now also being used. This features several changes to accommodate requirements requested by the American space agency NASA, including more latitude in the height and weight of the crew and improved parachute systems. It is also the first expendable vehicle to feature "glass cockpit" technology.
The unmanned Progress spacecraft were derived from Soyuz and are used for servicing space stations. The Chinese Shenzhou spacecraft is also heavily influenced by the design of the Soyuz. In 2004, Russian space officials announced that the Soyuz will be replaced by early 2011 with the new Kliper spacecraft.
- David S.F. Portree, Mir Hardware Heritage, NASA RP-1357, 1995
- Information on Soyuz spacecraft (search for Soyuz on that page for links to every spacecraft imaginable)
- OMWorld's ASTP Docking Trainer Page
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