Progress MS-06 freighter undocks from ISS

File photo of an unpiloted Russian cargo craft. Credit: NASA

Closing out visiting vehicle comings-and-goings for 2017, the unpiloted Russian Progress MS-06 cargo spacecraft undocked from the International Space Station in preparation for an eventual deorbit into Earth’s atmosphere.

Progress MS-06 pulled into port on June 16, 2017, at the aft end of the Zvezda service module on the Russian Orbital Segment of the space station. Over the last six months, the freighter’s 2,700 kilograms of equipment, food, water, and fuel was emptied and replaced with trash and unneeded equipment that will burn up in the atmosphere with the rest of the one-time use spacecraft.

Undocking officially took place at 01:03 GMT on Dec. 28 (8:03 p.m. EST Dec. 27), 2017. At 04:10 GMT, Russian flight controllers transmitted commands to Progress MS-06 to fire its engines for a three-minute burn to deorbit the space freighter, sending it on a destructive re-entry over an unpopulated region in the south Pacific Ocean. At 04:43 GMT, the spacecraft re-entered the Earth’s atmosphere. According to ballistics calculations, the disintegration of the cargo craft’s structure occurred at 04:51 GMT.

The undocked Progress MS-06 spacecraft. Credit: Roscosmos

While docked, Progress MS-06 was used for several space station reboosts. The first occurred on Aug. 9 and a second not long after on Aug. 27. A third, fourth, and fifth orbit-raising burn took place on Sept. 27, Nov. 2, and Nov. 29, respectively.

Over time due to a slight amount of drag in the upper atmosphere, the space station gradually slows down. From time to time, correction burns are needed to maintain an operational altitude of around 400 kilometers.

Currently, only one Russian cargo craft remains at the orbiting outpost: Progress MS-07, which is docked at the Earth-facing port of the Pirs module. Additionally, two crewed Soyuz spacecraft are docked: Soyuz MS-06 at the space-facing port of Poisk and Soyuz MS-07 at the Earth-facing port of Rassvet. Also, one U.S. cargo capsule is berthed: SpaceX’s CRS-13 Dragon at the Earth-facing port of Harmony.

The next Russian cargo ship to launch to the ISS will be Progress MS-08. It will take to the skies on Feb. 11, 2018, atop a Soyuz 2.1a rocket to supply Expedition 54 and 55. Once in orbit, it will rendezvous and dock with the aft port of Zvezda within two orbits, which will take about three hours.

Progress MS-07, which launched on Oct. 14, 2017, was supposed to utilize this rendezvous profile; however, a glitch with the Soyuz rocket on its first launch attempt caused a rare abort and scrub.

Because the fast-track rendezvous require precise orbital alignments, it was not possible to do either a two-orbit or four-orbit trek to the station. Instead, the freighter defaulted to a more-standard 34-orbit, two-day profile after liftoff.

Russia is looking at utilizing the three-hour trek to the space station on both its cargo and crewed launches. However, the rendezvous technique must be tested and perfected via Progress spacecraft before the crewed Soyuz attempts the fast-track profile.

The International Space Station's docking configuration on Dec. 28, 2017. Credit: Orbital Velocity

NOTE: While this article was written by Derek Richardson, it was originally published at SpaceFlight Insider. Feel free to head over there to read all the stuff they write about!