A Russian cargo ship linked up with the International Space Station today (April 9) to deliver tons of vital supplies during a swift, six-hour trip to the orbiting outpost.
The unmanned Progress 55 spacecraft linked up with the space station at 5:14 p.m. EDT (2114 GMT) nearly six hours after launching into orbit atop a Soyuz rocket from the Baikonur Cosmodrome in the Central Asian nation of Kazakhstan at 11:26 a.m. EDT (1526 GMT). It was 9:26 p.m. local time in Baikonur at the time of the launch.
The Progress 55 spacecraft performed flawlessly during the docking during its "silky smooth six-hour adventure," NASA spokesman Rob Navias said during live NASA TV commentary. [See photos of the Progress 55's launch to the space station]
Russian space officials applauded the docking success, with cosmonauts onboard describing Progress 55 as "a great present for Cosmonautics Day." Saturday, April 12, is Cosmonautics Day, a Russian holiday that celebrates the 1961 launch of Yuri Gagarin on the world's first human spaceflight.
Progress 55 (also known as the Progress M-23M) brought 1,764 lbs. of propellant, 926 lbs. of water, 105 lbs. of oxygen and 3,126 lbs. of other supplies like food and materials for science experiments to the six crewmembers living and working on the station today. NASA's Rick Mastracchio and Steve Swanson; Russian cosmonauts Alexander Skvortsov, Mikhail Tyurin and Oleg Artemyev; and Japanese astronaut Koichi Wakata make up the station's Expedition 39 crew.
Russia's Progress vehicles have been making the quick, six-hour trips to the station since 2012. The manned Soyuz capsules that ferry astronauts and cosmonauts to and from the station have done the same express flight since 2013. Before the fast-tracked arrivals, Progress and Soyuz spacecraft took two days to reach the station after launch.
Progress and Soyuz vehicles are similar in appearance, however, instead of the Soyuz's crew-carrying return capsule, Progress ships have a propellant capsule.
When Swanson, Skvortsov and Artemyev launched from Baikonur about two weeks ago, they were expected to make an express trip to the station like the Progress today, however, due to a slight issue with the positioning of the Soyuz after launch, they instead took two days to dock with the space station.
The Progress 55 launch comes just two days after the robotic Progress 54 departed the space station. Progress 54 undocked from the Pirs docking compartment (making way for the Progress 55) on Monday (April 7) after being attached to the station since February. The Progress 54 vehicle has now moved away from the outpost for tests before it de-orbits, burning up in Earth's atmosphere.
The International Space Station will play host to another unmanned cargo ship next week when the private spaceflight company SpaceX launches its third official resupply flight to the space laboratory on Monday (April 14) using its Dragon capsule and Falcon 9 rocket.
Editor's Note: This is an updated version of an earlier story posted on Space.com.