Despite thruster glitch, test of manual Progress docking successful
In a test of the manual docking system on the Russian side of the International Space Station (ISS), a Progress cargo ship undocked from the Pirs docking compartment early this morning and was remotely re-docked by cosmonaut Alexey Ovchinin some 30 minutes later, despite a thruster glitch at the moment of capture.
Progress MS-01 nears Pirs for re-docking. Photo Credit: Roscosmos
The test provided an opportunity to verify a new signal converter installed on the Telerobotically Operated Rendezvous System (TORU), which allows crews to take over an approaching Progress spacecraft in the event the automated docking program fails.
Physical separation occurred at 12:36 a.m. CDT (05:36 GMT) July 1. Progress MS-01, which had been attached to the orbiting outpost since December 2015, was pushed away via springs in the docking mechanism. The initial speed was only 4.7 inches (12 centimeters) per second.
The automatic departure was monitored by Expedition 48 flight engineers Ovchinin and Oleg Skripochka. Both were positioned at the TORU station located in the Zvezda service module.
Twelve minutes and two brief thruster firings later, the Progress reached a distance of about 623 feet (190 meters) away from the ISS and transitioned to stationkeeping mode.
After initial checks, mission control in Moscow gave the two Russians permission to initiate the manual docking. The close rate was about 11.8 inches (30 centimeters) per second, as the two cosmonauts insured the docking target was in the center of the crosshairs in the engineering camera view from Progress.
Ovchinin was at TORU’s controls and was flying the spacecraft in. Skripochka monitored the approach. All remained on target.
Once the Progress reached about 82 feet (25 meters) from Pirs, another stationkeeping period occurred to ensure everything was still aligned and systems were still operating as expected.
Due to a thruster glitch, the Progress began to oscillate around the Pirs docking compartment. Photo Credit: NASA TV
Final approach started around 1 a.m. CDT (06:00 GMT) as Ovchinin guided Progress in at a rate of only 5.9 inches (15 centimeters) per second. There was another brief stationkeeping period at about 9.8 feet (3 meters), but final capture of the docking probe occurred at 1:05 a.m. CDT (06:05 GMT).
At the moment of docking, however, there was a noticeable amount of oscillation. Based on views from engineering cameras, the Progress rotated as much as 10 to 15 degrees. Some dampening between the ISS and visiting vehicles is normal, but this amount was more than usual.
According to Spaceflight101, as the Progress docked to Pirs, thrusters from both the X and Y axes fired. Normally, only the X-axis thrusters fire to push the spacecraft at the moment of contact to engage capture latches. The reason the Y-axis thrusters fired remains under investigation.
After the oscillation dampened, the probe was retracted and hooks closed forming a hard-mate between the space station and cargo craft. There it will remain, with hatches closed until Saturday night.
Over the last number of weeks, the crew loaded the spacecraft with hundreds of pounds of unneeded equipment and trash. The hatches between the space station and Progress were officially closed on the morning of June 28.
Final undocking will occur at 10:48 p.m. CDT July 2 (03:48 GMT July 3). Four hours later, Progress MS-01 will deorbit and burn up over the Pacific Ocean.
Video courtesy of NASA TV
Derek Richardson
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity.
Nice report, thanks. Only thing I’d suggest adding is to specify the backaway/return direction — out-of-plane, aft, whatever. This is important to assessing the dynamic forces acting on the vehicle during ‘proximity operations’.