LONG-DURATION SPACEFLIGHT

With the loss of the race to the Moon, the Soviets reported that they had actually never intended to go there anyway. Their plan was to develop a long-duration orbital station. It was years before the truth came out and the details of their abandoned lunar programme became known. However, their statement was partially correct, as a military-based space platform called Almaz had been in development for years, supported by other Soyuz-type military variants. Almaz would not be the first station launched, however. To hasten the launch of the first Soviet space station, elements of Soyuz were added to a civilian variant called DOS and amalgamated into the world’s first space station – Salyut. This was launched two years before the Americans launched Skylab, which was itself fabricated from left over Apollo lunar hardware.

Soyuz

Critical to sustaining long-duration space flight is the supply of sufficient logistics and the rotation of the crews. For this, the Soviets called upon their orbital lunar space­craft Soyuz, adapting it to fly as a space station ferry craft (in manned and unmanned versions) and to serve as a crew rescue craft while docked to the station. The Soyuz vehicle was one of the most successful programmes in space history. Although the first manned mission in 1967 was a failure and resulted in the first casualty of space flight, a series of variants – Soyuz, Soyuz T, TM and TMA – have carried many crews to the Salyut and Mir national space stations and continue to do so to the current Inter­national Space Station. The programme will soon be entering its 40th year. After recovering from the loss of Soyuz 1 and the death of its cosmonaut, the Soviets evolved a series of missions to develop the rendezvous and docking technique they had intended to use on the way to the Moon, now amended for the space station programme. In addition, a short series of solo Soyuz flights flew space station equipment, conducting a series of test and supplementary flights to the often troubled Salyut series of stations.

The “original” Soyuz spacecraft was designed as a Vostok successor in about 1962. It weighed 6,450 kg (14,222 lb) and was 8.85m (29 ft) long from the base of its instrument section to the tip of its docking probe. The 2.3 m (7.5 ft) long, 2.3 m (7.5 ft) diameter instrument section, called the Equipment Module (EM), included a UDMH-nitric oxide prime and back-up propulsion system, for orbital manoeuvres and retro-fire. The prime engine had a burn time of 500 seconds and a thrust of 417 kg (919lb). The instrument section included two 3.6m (12ft) by 1.9m (6ft) solar panels.

The flight and Descent Module (DM) was shaped like an inverted cup and measured 2.2 m (7 ft) long and 2.3 m (7.5 ft) in diameter. It included up to three seats and systems such as hydrogen peroxide ACS thrusters, a beacon, sun and infra-red sensors, and rendezvous radar beacons. It was equipped with one drogue and one main parachute (plus a reserve), which opened at about 8,500m (28,000 ft) altitude, and, beneath a jettisonable heat shield, a soft-landing retro-rocket to reduce speed to 0.3m/sec (1 ft/ sec) at 1 m (3 ft) altitude. Attached to the flight module was an Orbital Module (OM), a spherical capsule containing extra housekeeping and science equipment and which acted as an airlock for EVAs. This was 2.65 m (8.69 ft) long and 2.25m (7.3 ft) in diameter. The OM was discarded after retro-fire. It also included a 1.2 m (4 ft) long docking probe at its tip. The Soyuz 12 spacecraft was basically the same as the earlier Soyuz craft, except the crew wore spacesuits (following the loss of the Soyuz 11 crew who hadn’t). The craft was equipped with only batteries for power, and no solar panels, as it was intended as a space station ferry with only a two-day independent flight capability.

Soyuz T – for Transport – was introduced in 1979 and weighed about 6,850 kg (15,104 lb). It was a redesigned Soyuz ferry vehicle, reconfigured to take a crew of three and with two solar panels which allowed independent flight for four rather than two days. Also included were new computers, controls and telemetry systems. The major change to the Soyuz was its fully integrated fuel system, with attitude control thrusters using the same fuel source as the main propulsion unit. The thrust of the main engine was reduced to 315 kg (695 lb) but there were now 26 ACS thrusters aboard. The main reason for this was that some previous docking failures could have been overcome had the cosmonauts been able to transfer fuel from the ACS system to the main spacecraft engine. Soyuz T2 was preceded by three unmanned tests under the Cosmos label (869, 1001 and 1074) and one Soyuz (Tl) in 1979.

Soyuz TM – Transport Modification – was introduced in 1986 and weighed about 7,100 kg (15,653 lb). This was an uprated and heavier Soyuz T spacecraft, incorporat­ing new primary and back-up parachutes, improved power systems and retro-rockets, and the capability to carry 200 kg (441 lb) more payload and return to Earth with 50 kg (110 lb). Soyuz TM was also equipped with a rendezvous and docking system com­patible with the Mir Kurs system. Soyuz TM1 was an unmanned test flight to Mir in 1986.

Soyuz TMA – Transport Modification Anthropometric – was introduced in 2002 and was more of a systems and internal upgrade than a structural one, measuring and weighing about the same as the TM. The requirement for a new version of Soyuz was in part due to larger (American) crew members being assigned to Soyuz missions. New seating support structures and modifications to the descent landing engines meant a slightly greater landing mass was possible, allowing regular three-person crews to be flown. In addition, the controls and displays now featured more computer displays and smaller electronics systems. There were no unmanned TMA precursor flights.

An unmanned variant called Progress was introduced in 1978 and has also been upgraded (Progress M, M1). This has been used to re-supply Soviet space stations with fuel, logistics and orbital re-boost capability and is still an integral element in the ISS programme.