Cosmos 1686

Infobox Space station
station = Cosmos 1686
station_

station_image_size =
station_image_caption = Cosmos 1686 (top) docked to Salyut 7, imaged by Range-Doppler radar.
insignia = Salyut_insignia.jpg
insignia_caption = Salyut program insignia
sign = Salyut 7
launch = 1985-09-27
02:01:00 UTC
Docked to Salyut 7 on 1985-10-02.
launch_pad = Baikonur Cosmodrome, USSR
reentry = 1991-02-11
mass = 20,000 kg
perigee = 219 km (118.25 nmi)
apogee = 278 km (150.1 nmi)
inclination = 51.6 degrees
period = 89.2 minutes
length = 15 m
width = 16 m
diameter = 4.15 m
orbits_day = 16.14
in_orbit = 1959 days
as_of = deorbit & reentry
stats_ref = [cite web
title = COSMOS 1686 DEB Satellite details 1985-086C NORAD 16128
publisher = n2yo.com
date = 2007-06-29
url = http://www.n2yo.com/satellite.php?s=16128
accessdate = 2007-06-29] cite book
last = Portree
first = David
authorlink = David S. F. Portree
title = Mir Hardware Heritage
publisher = NASA
date = March 1995
location = Lyndon B. Johnson Space Center, United States of America
url =http://en.wikisource.org/wiki/Mir_Hardware_Heritage]
configuration_

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configuration_size =
configuration_caption = Combined Cosmos 1686-Salyut 7 space station complex

Cosmos 1686 was a heavily modified TKS spacecraft which docked unmanned to the Soviet space station Salyut 7 as part of tests to attach scientific expansion modules to stations in Earth orbit. The module which docked to the station was the FGB component of a TKS vehicle launched on 1985-09-27, and was designed to test systems planned for use on the Mir Core Module. The spacecraft docked with Salyut 7 on 1985-10-02, during the long-duration stay of the cosmonauts of its fifth principal expedition, which arrived on Soyuz T-14.

Notable features

* The spacecraft's Merkur capsule was greatly modified to carry instruments - the retrorocket and parachute packages were replaced by scientific equipment, including an infrared telescope and the Ozon spectrometer.
* The combined Salyut 7-Cosmos 1686 complex massed 43 tons, with Cosmos 1686 delivering 4500 kg of cargo to Salyut 7 and nearly doubling the amount of habitable volume available to the station's crew.
* On August 19-August 22 1986, ground controllers boosted the vacant Salyut 7-Cosmos 1686 complex to a 474 km by 492 km orbit using engines on Cosmos 1686. This reduced the propellant supply of the complex to 70 kg (about 500 kg were required for controlled deorbit). In addition, Cosmos 1686 and Salyut 7 each suffered major systems breakdowns soon after they were abandoned, making the complex impossible to control.
* All previous space stations over which the Soviets maintained control were intentionally deorbited after their last cosmonaut crew departed. The Soviets estimated that the reboost gave the complex an 8-yr lifetime in orbit. They considered recovering the station using the Buran shuttle. However, following delays to and the eventual cancellation of the Buran program, Cosmos 1686 underwent uncontrolled reentry with Salyut 7 on February 11, 1991.