After spending two days catching up with the International Space Station, the Progress MS-08 Russian cargo freighter docked with the orbiting outpost, bringing several metric tons of supplies for Expedition 54 and future crews.
The autonomous docking of the 7.2-meter long spacecraft took place at 5:38 a.m. EST (10:38 GMT) Feb. 15, 2018, at the aft-end of the Zvezda service module while the duo were flying 406 kilometers above Earth just East of the Philippines, according to NASA.
Later in the day, Russian cosmonauts Alexander Misurkin and Anton Shkaplerov opened the hatch to begin transferring supplies. The craft contains some 1,390 kilograms of dry cargo, 890 kilograms of fuel, and 420 kilograms of water, and 46 kilograms of oxygen.
Not counting spacecraft delivering modules to the ISS, Progress MS-08 is the 98th uncrewed spacecraft to service the outpost since August of 2000. The vehicle is expected to remain at the complex until August 2018 when it will undock and de-orbit to burn up in Earth’s atmosphere with trash and un-needed equipment.
Progress MS-08 launched atop a Soyuz 2.1a rocket at 3:13 a.m. EST (08:13 GMT) Feb. 13, 2018, from the Baikonur Cosmodrome in Kazakhstan. This was two days after the original launch attempt was called off moments before engine ignition. Roscosmos, the Russian state-run space corporation, has not revealed the cause of the abort.
The two-day delay prompted the cancellation of an experimental super-fast rendezvous technique that would have seen the Progress freighter arrive at ISS within two orbits to dock just 3.5 hours after launch. However, because very precise orbital alignments are required, a more-standard 34-orbit trek had to be taken after the Feb. 13 launch scrub.
Over the last several years, the uncrewed Progress and crewed Soyuz spacecraft have regularly been using a four-orbit rendezvous to get to the station in about six hours. For Soyuz crews in particular, this means less time spent in a very cramped spacecraft before arriving at the more-more-spacious outpost, which has an internal volume equivalent of a Boeing 747 aircraft.
The two-orbit approach would reduce that even further, but the complex rendezvous needs to be tested first. It was supposed to be evaluated during the launch and arrival of Progress MS-07 in October 2017. However, a similar scrub also prompted a reversion to a 34-orbit rendezvous profile.
While it hasn’t been announced if a two-orbit rendezvous will be utilized, the next attempt Roscosmos has at testing the profile will come during the launch of Progress MS-09 in July 2018.
Only when a robotic Progress spacecraft successfully tests the technique will a crewed Soyuz utilize the profile. For comparison, the six-hour approach was first tested during the Progress M-16M mission in August 2012. The crewed Soyuz TMA-08M used the profile in March 2013.
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!