Progress MS-18 docks at Zvezda
Launched in the early hours of October 28, 2021, the Progress MS-18 cargo ship embarked on a two-day trip to the International Space Station, ISS, concluding with a docking at the aft port of the Zvezda Service Module. That particular docking mechanism was unoccupied for half a year, because it is connected to the rest of the outpost via the PrK transfer compartment which had been leaking air despite all efforts to seal tiny cracks in its walls. (INSIDER CONTENT) Progress MS-18 should confirm that the PrK chamber could be used safely.
Progress MS-18 mission at a glance:
Progress MS-18 mission
According to Roskosmos, Progress MS-18 will deliver around 1,490 kilograms of supplies to the ISS, including 560 kilograms of propellant for refueling the station, 420 liters of water in the tanks of the Rodnik system and 43 kilograms of compressed air in the tanks of the oxygen supply system. In its pressurized cargo section, the spacecraft will carry dry cargo for the crew and equipment for ongoing scientific studies including experiments Matreshka-R, Biomag-M, Aseptik, Struktura and Fotobioreaktor.
During the early planning of the ISS flight manifest in 2014, the second Russian cargo mission of 2021 was planned for April 16, 2021, however in the provisional schedule prepared by Roskosmos at the end of August 2020, the launch of Progress MS-18 (ISS mission 79P, Production No. 447) was planned for August 18, 2021. By November 2020, the start of the mission slipped to October 28, 2021.
At the time, the vehicle was expected to dock at the aft port of the Zvezda Service Module, SM, and remain in orbit for 215 days, supporting the 66th long-duration expeditions aboard the ISS. That schedule remained unchanged until the launch.
Progress MS-18 launch campaign
The Soyuz-2-1a rocket for the Progress MS-18 mission arrived at Baikonur in the middle of August 2021. On September 1, Roskosmos announced that the cargo ship had been taken out of storage inside processing complex at Site 254 and installed in its testing rig, where specialists conducted visual inspection of the spacecraft in preparation for electric checks scheduled to begin on September 2.
The autonomous tests of the spacecraft's radio systems in the anechoic chamber were completed on September 23 and on September 28, the spacecraft was transported into the vacuum chamber for air leak checks, which were completed by October 4, when the spacecraft was returned to its processing facility at Site 254.
Progress MS-18 (top center) returns to its processing facility on October 4, 2021, after the completion of vacuum tests.
The mechanical assembly of the first and second stages of the Soyuz-2-1a launch vehicle for the mission was performed at Site 31 by October 8. On the same day, specialists conducted routine tests of the cargo ship's solar panels, tested the lines of the ship's Rodnik water-supply system. On October 15, a meeting of technical management cleared Progress MS-18 for fueling of its propulsion unit and of the re-fueling section. Prior to its departure to the fueling station, the spacecraft undewent balancing and weighting at Site 254. Also, on October 15, specialists at the vehicle assembly building at Site 31 completed the four-day process of pneumatic tests on the three stages of the Soyuz-2-1a rocket and transitioned to autonomous tests of the rocket's systems.
The fueling operations with Progress were completed by October 19, after which, the cargo ship was returned to its processing stand at Site 254. On October 20, the spacecraft was integrated with an adapter section serving as an interface with the launch vehicle. The stack was then lowered in horizontal position, rolled inside its payload fairing and, on October 22, the assembled payload section was loaded into a rail transporter and shipped to the vehicle assembly building for integration with its rocket which was completed on October 23.
The launch vehicle was rolled out to the launch pad on the morning of Oct. 25, 2021.
Progress MS-18 launch profile
Following vertical liftoff under the combined thrust of the four RD-107 engines on the first stage and the single RD-108 of the second (core) stage, the launch vehicle headed eastward from Baikonur matching its ground track to an orbit inclined 51.67 degrees to the plane of the Equator. The four first-stage boosters separated nearly two minutes into the flight, followed by the split and drop of the two halves of the payload fairing slightly more than a minute later. In the meantime, the second stage continued firing until 4.7 minutes into the flight.
The third stage ignited moments before the separation of the second stage, firing its RD-0110 engine through a lattice structure connecting the two boosters and ensuring a continuous thrust during the separation process. A fraction of a second after the boosters of the second and third stage parted ways, the aft cylindrical section of the third stage split into three segments and dropped off, ensuring the fall of the second stage and the aft section into the same drop zone.
The spacecraft was expected to separate from the third stage of the launch vehicle 8 minutes and 49 seconds after liftoff into a 193 by 240-kilometer orbit with an inclination 51.67 degrees toward the Equator.
Rendezvous and docking
The Progress MS-18 mission followed a two-day rendezvous profile with the ISS. Its docking at the aft port of the Zvezda Service Module was scheduled for Oct. 30, 2021, at 04:33 Moscow Time (9:33 p.m. EDT on October 29) with three-minute accuracy. The actual physical contact between the cargo ship and the station was registered at 04:31:19 Moscow Time on October 30 (9:31 p.m. EDT on October 29).
It was the first spacecraft docking at the aft port of the Zvezda Service Module since the departure of Progress MS-14 on April 28, 2021. During that period, the PrK transfer chamber connecting the port to the Zvezda's interior, remained closed off to mitigate an air leak in its walls (INSIDER CONTENT).
On November 10, Roskosmos announced that Progress MS-18 cargo ship was scheduled to fire its engine for 361 seconds starting at 23:15 Moscow Time (3:15 p.m. EST), increasing the station's velocity by 0.7 meters per second and boosting its average altitude by 1,240 meters to 420.72 kilometers. According to the State Corporation, the maneuver, designed to avoid space junk, went as scheduled.
Several hours earlier, Roskosmos said that the ISS had been predicted to pass close to a fragment of the Fengyun-1C satellite around 04:00 Moscow Time on November 12 (8 p.m. EST on November 11). Fengyun-1C satellite was destroyed in 2007 in a test of a Chinese anti-satellite missile.
Previously, an orbit correction using Progress MS-18's propulsion system was planned to be initiated on Nov. 16, 2021, at 20:40 Moscow Time. The maneuver was scheduled to last 478 seconds, Roskosmos said on November 8. However, on November 11, Roskosmos announced that the orbit correction originally planned on November 16 had been cancelled, because the space-junk-avoidance manuever conducted on November 10 was designed to provide necessary orbital parameters for the station.
Another maneuver with Progress MS-18's engines was conducted on Dec. 3, 2021, this time to avoid a fragment of the US Pegasus rocket launched in 1994. On December 1, the piece was predicted to pass as far as 5.4 kilometers from the ISS at 13:33 Moscow Time on December 3, but the estimate was later updated to around three kilometes. As a result, at 10:58 Moscow Time, Progress MS-18 was commanded to fire its propulsion system for 160.9 seconds slowing the ISS' velocity by 0.3 meters per second and lowering its overall altitude by 310 meters. According to the Russian mission control, after the maneuver, the station was in orbit with the following parameters:
Two components of the core stage appearing in the foreground of the photo released on May 4, 2021, likely belong to the Soyuz-2-1b rocket assigned to launch the Progress MS-17. The vehicle for the ninth OneWeb mission is in the background. Click to enlarge. Credit: Roskosmos
Progress MS-18 is undergoing tests in anechoic chamber on Sept. 23, 2021. Click to enlarge. Credit: Roskosmos
Click to enlarge. Credit: Roskosmos
Progress MS-18 is integrated with a payload fairing on Oct. 22, 2021. Click to enlarge. Credit: Roskosmos
Progress MS-18 lifts off on Oct. 28, 2021. Click to enlarge. Credit: Roskosmos