Progress M-55 (Russian: Прогресс М-55), identified by NASA as Progress 20P, was a Progress spacecraft used to resupply the International Space Station. It was a Progress-M 11F615A55 spacecraft, with the serial number 355.^[1]

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Progress M-55

Progress M-55 departing the ISS.
Mission type	ISS resupply
Operator	Roskosmos
COSPAR ID	2005-047A
SATCAT no.	28906
Mission duration	181 days
Spacecraft properties
Spacecraft type	Progress-M s/n 355
Manufacturer	RKK Energia
Launch mass	5700 kg
Start of mission
Launch date	21 December 2005, 18:38:20 UTC
Rocket	Soyuz-U
Launch site	Baikonur, Site 1/5
End of mission
Disposal	Deorbited
Decay date	19 June 2006, 17:53:14 UTC
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Inclination	51.6°
Epoch	21 December 2005
Docking with ISS
Docking port	Pirs
Docking date	23 December 2005, 19:46:18 UTC
Undocking date	19 June 2006, 14:06:01 UTC
Time docked	179 days
Cargo
Mass	1400 kg (equipment and spare parts)
Fuel	880 kg
Gaseous	83 kg
Water	210 kg
Progress ISS Resupply ← Progress M-54 Progress M-56 →

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Progress M-55 was launched by a Soyuz-U carrier rocket from Site 1/5 at the Baikonur Cosmodrome. Launch occurred at 18:38:20 UTC on 21 December 2005.^[1]

The spacecraft docked with the Pirs module at 19:46:18 UTC on 23 December 2005.^[2][3] It remained docked for almost 179 days before undocking at 14:06:01 UTC on 19 June 2006^[2] to make way for Progress M-57.^[4] It was deorbited at 17:06:01 UTC on 19 June 2006.^[2] The spacecraft burned up in the atmosphere over the Pacific Ocean, with any remaining debris landing in the ocean at around 17:53:14 UTC.^[2][5]

Progress M-55 carried supplies to the International Space Station, including food, water and oxygen for the crew and equipment for conducting scientific research.

• List of Progress flights
• Uncrewed spaceflights to the International Space Station