Salyut 4

Salyut 4 was the second successful 'Zarya' station and followed on from Salyut 1 in 1970. Cosmos 557 made it into orbit in 1973, but failed immediately so it never even got the Salyut name. Salyut 2 (another failure) and Salyut 3 were 'Almaz' stations designed for use in reconnoitring the Earth from space.

Salyut 4 hosted two crews for missions of 30 days (Soyuz 17) and 63 days (Soyuz 18) respectively and they used a range of equipment for scientific and medical studies. The original attempt to fly the Soyuz 18 mission during 1975 had to be aborted when the upper stage of its carrier rocket failed to separate cleanly. The crew was forced to land immediately as the spacecraft had insufficient velocity to reach orbit.

Soyuz 20, which was launched without a cew, gave an indication of longer missions to come with future Salyut stations. It stayed docked for three months in an extended test of Soyuz spacecraft systems before returning safely to Earth.

The 'missing' Soyuz 19 designation belonged to the spacecraft launched as the Soviet Union's contribution to the international Apollo-Soyuz Test Project which brought the USSR and the USA together in space (see the diary entry for 1975 July 17).

The engine compartment at the rear, was 'borrowed' directly from the design of Soyuz. This resulted from Korolyov's design bureau taking a fast-track design route using one of Chelomei's 'Almaz' spacecraft hulls and adapting it using tried and tested Soyuz components.

The four angled thrusters were used for changing the station's orbit. The three nozzles across the centre are the Soyuz retro-rocket nozzles. They were not used by version of the engine installed on the Salyut stations - hence them being plugged.

One of Salyut's rendezvous radar transponder antennae is housed inside the yellow dome on a stalk at bottom right.

This view shows some of Salyut 4's interior - a velo-ergometer for exercising and for medical experiments hangs from the 'ceiling'. Either side of it is a small airlock used for disposing of rubbish to the vacuum of space. A sleeping bag with an elastic restraint is next to the right hand one.

Aside from medical and biological studies of the crew and photographic studies of the Earth from space, Salyut 4 served principally as an astrophysical observatory. The table below lists the main equipment which was on board at launch.

The photo shows the external sensors of the instrument cluster. The cone-shaped structure at top right acts as a light baffle for the telescope's main mirror and extends through the hull to a control panel inside the station.

External Experiments

OST-1	Solar telescope used to measure ultra-violet radiation from the Sun in order to study its surface temperature
ITS-K	Infra-red telescope used to study radiation from the Earth's atmosphere, and to make astronomical observations - it was used to study the Moon, Saturn, the Magellanic Clouds, the Andromeda nebula, and stars
Filin	X-ray telscope for finding x-ray emission sources in the night sky
RT-4	X-ray telescope for measuring the "brightness" of x-ray objects, it was used to study the Crab nebula and the star Rigel among others
SSP-2	A spectrometer used to study the Earth's atmosphere (particularly the ozone layer as there were already concerns about it being damaged by pollution) and the Sun
MMK-1	Micro-meteoroid detector studying the presence of small particles in near-Earth space
Emissaya	A spectrometer used to measure minute particles of dust in the Earth's atmosphere

Internal Experiments

Biotherm-1	A container with a controlled climate used to study single celled plant growth
Biotherm-2M	A container with a controlled climate used to house fruit flies for genetic research, and also play home to other insects
Biotherm-3	A container with a controlled climate containing three small aquariums used to study the development of eggs of the South African Marsh Frog - tadpoles produced were frozen and returned to Earth for study
Biotherm-4	A container with a controlled climate used to study changes in animal cell structure - samples of animal tissue were suspended in a nutrient fluid
Oasis-1M	A greenhouse for studying plant growth - principally onion and pea plants

Salyut 4 Diary

Date	Time (UTC)	Event
1974 Dec 26	04:19	Salyut 4 launched from the Baikonur Cosmodrome by Proton rocket into 215 x 252 kilometre orbit at 51.6 degrees inclination
1974 Dec 31		Salyut 4 established in its operational orbit of 338 x 351 kilometres
1975 Jan 10	21:43	Soyuz 17 launched from the Baikonur Cosmodrome by Soyuz rocket into 185 x 249 kilometre orbit with Aleksei Gubarev and Georgi Grechko aboard
1975 Jan 12	01:25	Soyuz 17 docks with Salyut 4 - orbit is 336 x 349 kilometres
1975 Jan 12		The crew of Soyuz 17 enters Salyut 4 and find a note left inside by the space station preparation team - it says 'Wipe Your Feet!'
1975 Feb 9	06:08	Soyuz 17 undocks with Gubarev and Grechko aboard - Salyut 4 orbit is 334 x 346 kilometres
1975 Feb 9	11:03	Soyuz 17 lands - 100 kilometres north-east of Tselinograd
1975 Mar 22		Salyut 4 orbit has decayed to 330 x 340 kilometres, it is raised to 337x 350 kilometres
1975 Apr 1		Salyut 4 orbit is adjusted to 339 x 351 kilometres ready for rendezvous with the upcoming Soyuz 18
1975 Apr 5	11:02	Soyuz spacecraft (subsequently named by the Soviet Union as the 1975 'April anomaly') launched from the Baikonur Cosmodrome by Soyuz rocket with Vasily Lazarev and Oleg Makarov aboard
1975 Apr 5	11:07	Separation between the second and third stages of the April anomaly Soyuz rocket fails - the third stage engine fires however, and the crew is forced to use the Soyuz propulsion system to pull away from it
1975 Apr 5	11:23	The April anomaly Soyuz lands almost 1,600 km from the launch site, near the town of Gorno-Altaisk close to the Chinese border, and possibly inside China itself
1975 May 14		Salyut 4 orbit has decayed to 330 x 351 kilometres, it is raised to 344 x 353 kilometres ready for rendezvous with the second attempt at the Soyuz 18 mission
1975 May 24	14:58	Soyuz 18 launched from the Baikonur Cosmodrome by Soyuz rocket into 186 x 230 kilometre orbit with Pyotr Klimuk and Vitali Sevastyanov aboard
1975 May 25	21:30	Soyuz 18 docks with Salyut 4 - orbit is 338 x 349 kilometres
1975 Jul 24		The crew begins mothballing Salyut 4 in preparation for their departure
1975 Jul 25		Salyut 4 orbit is adjusted using Soyuz 18 propulsion system - it has decayed to 335 x 344 kilometres - the rocket motor firings raise it to 342 x 361 kilometres
1975 Jul 26	10:56	Soyuz 18 undocks FROM Salyut 4with Klimuk and Sevatyanov aboard - Salyut 4 orbit is 342 x 361 kilometres
1975 Jul 26	14:18	Soyuz 18 lands - 56 kilometres south-west of Arkalyk
1975 Nov 4		Salyut 4 orbit has decayed to 332 x 348 kilometres, it is raised to 344 x 353 kilometres
1975 Nov 17	14:38	Soyuz 20 launched from the Baikonur Cosmodrome by Soyuz rocket into 177 x 251 kilometre orbit - it has no crew aboard but carries a cargo of biological specimens including turtles and plants - experiments are to performed in parallel with the Cosmos 782 biological satellite on a three-week mission
1975 Nov 19	16:19	Soyuz 20 docks with Salyut 4 - orbit is 342 x 350 kilometres
1976 Feb 15	23:07	Soyuz 20 undocks - Salyut 4 orbit is 335 x 341 kilometres
1976 Feb 16	02:24	Soyuz 20 lands - 56 kilometres south-west of Arkalyk
1977 Feb 2		After nearly one year, Salyut 4 orbit has decayed to 186 x 187 kilometres - its propulsion system is activated, causing it to re-enter the Earth atmosphere over the Pacific Ocean where it is destroyed by frictional heating