The Progress M-21M resupply vehicle was manually docked with the ISS, following an extended trip in space towards its arrival on Friday. The vehicle was tasked with testing a more-efficient KURS automated rendezvous system. However, the system failed at 60 meters distance from the Station, requiring a rare manual docking that was ably completed by Commander Oleg Kotov.
A Russian Soyuz-U rocket launched Progress M-21M en route for its rendezvous with the orbital outpost at 20:53 UTC on Monday.
Following its liftoff from the Baikonur Cosmodrome, Progress M-21M spent several days in orbit, unlike a number of its predecessors that have been using the well-practised four-orbit fast rendezvous with the ISS, conducted over a period of around six hours.
The fast rendezvous approach was detailed in a Russian document describing the new rendezvous profile, which was seen by NASASpaceflight.com, with the purpose of the maneuver aimed at shortening the time it takes between launches and dockings of Russian vehicles to the ISS, which usually stands at about 50 hours.
While the primary driver for this capability is to cut down on the amount of time that crews must spend inside the cramped Soyuz spacecraft between launch and docking, the maneuver was first being tested out with a few Progress vehicles in order to prove the concept, and demonstrate that it can be performed safely and successfully.
Progress vehicles can also benefit from the faster rendezvous however, as it allows time-critical biological payloads to reach the ISS very soon after launch, as other vehicles, such as Japan’s HTV and Europe’s ATV, can take up to a week to reach the ISS following launch.
The speedy process has since become standard for both Progress and Soyuz vehicles heading to the Station – allowing new crewmembers to become part of the ISS expedition without having to spend two days inside the small capsule.
However, the uncrewed Russian resupply spacecraft – loaded with almost three tons of food, fuel and supplies for the six Expedition 38 crew members aboard the ISS – reverted back to the longer route to the ISS, allowing for the test of an upgraded rendezvous system.
In fact, the trip was even longer than usual, involving four days on orbit, allowing for flybys of the Station to test the new system.
Unlike recent Progress vehicles that used the 2AO-VKA and AKR-VKA antennas of KURS-A system, M-21M sported a AO-753A antenna of the KURS-NA system instead.
Once the Progress reached its preliminary orbit, it conducted a series of automated engine burns to put it on track to fly within one mile of the station on Wednesday, allowing for the test of the lighter, more-efficient KURS automated rendezvous system hardware for upgraded Soyuz and Progress vehicles. The tests were all classed as successful.
Following the flyby, the Progress looped above and behind the station, returning Friday for its docking.
However, despite a good approach and flyaround, the KURS system suffered a failure at just 60 meters distance during final approach.
The Progress immediately halted its approach, allowing for Oleg Kotov to take control of the vehicle via the manual TORU system.
Using a joystick and a control panel on the ISS, the Expedition 38 commander guided the Progress into the docking port with a large amount of skill, as the vehicle started to move around the docking target.
Docking was confirmed at 22:30 UTC, followed by hard mate.
The antenna system was last in the news for an unrelated reason, namely with Progress M-19M, when its KURS-A antenna did not deploy after separation during its April trip to the Station.
With Russian controllers uploading a software patch to aid the KURS approach – and the manual TORU system on standby, in case of a KURS failure – the teams pressed on towards a docking with the ISS, aimed with a large amount of documentation to cover numerous docking scenarios.
As Progress approached the ISS, TV cameras on the Station provided the first view of the antenna, which appeared to be restricted by the docking collar.
With NASA teams also analyzing the situation from the Johnson Space Center (JSC) ahead of its arrival at the orbital outpost, the main area of concern related to the potential for damage on the ISS, as the Progress docked with the antenna out of its nominal configuration.
The expansive notes showed a level of caution from the NASA teams, such as the potential for contact between the off-nominal KURS hardware and an antenna on the ISS in the location of the docking port – to the point an EVA would be required to repair it after Progress departs.
“KURS antenna could collide with the high gain antenna (ОНА) pin-locking assembly and the (4АО-ВКА) antenna on the SM. This could result in damage to the (4АО-ВКА) antenna,” added a specific L2 section on the Progress M-19M situation.
“External inspection of the (4АО-ВКА) antenna will also be required when the Progress vehicle undocks. If the test is failed or there are comments during the external inspection, EVA will be required to repair or replace the (4АО-ВКА) antenna.”
However, the veteran ship docked without issue, allowing for soft dock, the docking probe to be retracted, followed by hard dock 10 minutes later.
Now the tests are complete on this latest Progress (M-21M), docking – along with its delivery of 1,763 pounds of propellant, 48 pounds of oxygen, 57 pounds of air, 925 pounds of water and 3,119 pounds of spare parts and experiment hardware – saw the vehicle take up residency at the aft port of the Zvezda service module.
Hatch opening will occur over the weekend.
(Images: via NASA, Roscosmos and L2).
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